[Test] (MG_Test): replay a real Iris shader pair through the whole async frontend, both phases and both quirk states

CMakeLists.txt

@@ -296,6 +296,7 @@ set(SOURCE_FILES
     MobileGL/MG_State/GLState/TextureState/TextureState.cpp
     MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp
     MobileGL/MG_State/GLState/ProgramState/ProgramLinkTask.cpp
+    MobileGL/MG_State/GLState/ProgramState/ProgramSpirvTask.cpp
     MobileGL/MG_State/GLState/ProgramState/ShaderCompileTask.cpp
     MobileGL/MG_State/GLState/ProgramState/ShaderObject.cpp
     MobileGL/MG_State/GLState/ProgramState/ShaderPreprocessCache.cpp

MobileGL/Config.h

@@ -136,6 +136,19 @@ namespace MobileGL::MG_Config {
         // MOBILEGL_ASYNC_SHADER_COMPILE_THREADS: shader-compile worker count. 0 (unset) means
         // auto, which is min(4, big cores); an explicit value is honoured as given.
         Uint32 AsyncShaderCompileThreads = 0;
+        // MOBILEGL_ASYNC_OPTIMISTIC_SHADER_STATUS: while a compile job is still in flight,
+        // glGetShaderiv(GL_COMPILE_STATUS) answers GL_TRUE and the shader info log reads
+        // empty, WITHOUT joining the job (latched per compile - see
+        // ShaderObject::TakeOptimisticCompileAnswer). A deliberate, bounded spec violation:
+        // a real failure still fails the program link with the compile log quoted. It
+        // exists for applications that compile hundreds of shaders serially and read the
+        // status right after each glCompileShader - Iris's shader-pack load - where those
+        // per-shader joins are what serializes the batch on its main path (Iris's gbuffer
+        // phase issues no program-level query between programs; program-level LINK_STATUS
+        // and the program info log still join truthfully, so paths that check each link
+        // immediately stay serial by their own construction). Off by default; never
+        // advertise it.
+        QuirkOverride AsyncOptimisticShaderStatus = QuirkOverride::Auto;
     };
     extern FeaturesTable Features;
 } // namespace MobileGL::MG_Config

MobileGL/ConfigLoader.cpp

@@ -183,6 +183,8 @@ namespace MobileGL::MG_ConfigLoader {
         features.EsprytMultiDrawMode = QueryEnvGLESMultiDrawMode("MOBILEGL_ESPRYT_MULTIDRAW_MODE");
         features.AsyncShaderCompile = QueryEnvQuirkOverride("MOBILEGL_ASYNC_SHADER_COMPILE");
         features.AsyncShaderCompileThreads = QueryEnvUint32("MOBILEGL_ASYNC_SHADER_COMPILE_THREADS", 0, 0, 64);
+        features.AsyncOptimisticShaderStatus =
+            QueryEnvQuirkOverride("MOBILEGL_ASYNC_OPTIMISTIC_SHADER_STATUS");
     }
 
     inline void InitBackendType() {

MobileGL/MG_Backend/DirectGLES/DirectGLES.cpp

@@ -2028,7 +2028,9 @@ namespace MobileGL::MG_Backend::DirectGLES {
             g_currentDrawFrontendProgram = nullptr;
             g_currentDrawBackendProgram = nullptr;
 
-            if (!currentProgram || !currentProgram->GetLinkStatus()) {
+            // ... || !GetSpirvStatus(): see BackendProgramObjectImpl::SyncToBackend - a
+            // program whose SPIR-V never arrived is linked but not drawable.
+            if (!currentProgram || !currentProgram->GetLinkStatus() || !currentProgram->GetSpirvStatus()) {
                 g_GLESFuncs.glUseProgram(0);
                 g_lastUsedBackendProgramId = 0;
                 return;
@@ -2589,7 +2591,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
     static void BindCurrentProgramWithResources(
         const SharedPtr<MG_State::GLState::ProgramObject>& currentProgram,
         const TextureImpl::DrawTextureSyncKeys& keys) {
-        if (currentProgram && currentProgram->GetLinkStatus()) {
+        if (currentProgram && currentProgram->GetLinkStatus() && currentProgram->GetSpirvStatus()) {
 #ifdef TRACY_ENABLE
             ZoneScopedNC("BindCurrentProgram", TRACY_ZONECOLOR_BACKEND);
 #endif
@@ -2859,7 +2861,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
     // is pinned for the duration. Prefers the per-draw stash those preparations wrote.
     static PrgramImpl::BackendProgramObjectImpl* GetCurrentBackendProgram() {
         const auto& currentProgram = MG_State::pGLContext->GetProgramForDraw();
-        if (!currentProgram || !currentProgram->GetLinkStatus()) {
+        if (!currentProgram || !currentProgram->GetLinkStatus() || !currentProgram->GetSpirvStatus()) {
             return nullptr;
         }
         if (PrgramImpl::g_currentDrawFrontendProgram == currentProgram.get()) {
@@ -3017,7 +3019,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
         TextureImpl::SyncImageTextureBindings();
         PrgramImpl::SyncCurrentProgram(currentProgram);
 
-        if (!currentProgram || !currentProgram->GetLinkStatus()) {
+        if (!currentProgram || !currentProgram->GetLinkStatus() || !currentProgram->GetSpirvStatus()) {
             g_GLESFuncs.glUseProgram(0);
             PrgramImpl::g_lastUsedBackendProgramId = 0;
             return;

MobileGL/MG_Backend/DirectGLES/Managers.cpp

@@ -4156,8 +4156,14 @@ namespace MobileGL::MG_Backend::DirectGLES {
                 return;
             }
 
-            if (!stateProgramObject->GetLinkStatus()) {
+            // GetSpirvStatus() as well as GetLinkStatus(): a program whose phase-B job was
-                MGLOG_E("Program object is not linked, skipping backend sync. State program ID: %u",
+            // cancelled (teardown) or whose optimizer run failed is fully linked and fully
+            // queryable, but has no SPIR-V to build a driver program out of. GL cannot retract
+            // a LINK_STATUS it already reported true, so "linked but not drawable" is the
+            // answer, and this is where the ES backend expresses it.
+            if (!stateProgramObject->GetLinkStatus() || !stateProgramObject->GetSpirvStatus()) {
+                MGLOG_E("Program object is not linked or has no generated SPIR-V, skipping backend sync. State "
+                        "program ID: %u",
                         stateProgramObject->GetExternalIndex());
                 return;
             }

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp

@@ -4267,8 +4267,15 @@ void main() {
         auto writeUniform = [&](Int location, const void* data, SizeT size) {
             MOBILEGL_ASSERT(location >= 0, "GenerateDepthMipmapWithShader: invalid uniform location");
             const Uint offset = m_depthMipmapResources.program->GetUniformOffset(static_cast<Uint>(location));
-            MOBILEGL_ASSERT(offset + size <= m_depthMipmapResources.program->GetUBOSize(),
+            // A RETURN, not only an assert: the assert compiles out in release, and a program
-                            "GenerateDepthMipmapWithShader: uniform write out of bounds");
+            // whose SPIR-V job settled cancelled reports kInvalidUniformOffset (~0u) with a
+            // zero-sized shadow - which would make the memcpy below a wild write at
+            // depthProgramData + 4 GiB rather than a dropped uniform.
+            if (offset == MG_State::GLState::ProgramObject::kInvalidUniformOffset ||
+                offset + size > m_depthMipmapResources.program->GetUBOSize()) {
+                MOBILEGL_ASSERT(false, "GenerateDepthMipmapWithShader: uniform write out of bounds");
+                return;
+            }
             memcpy(depthProgramData + offset, data, size);
             m_depthMipmapResources.program->MarkUBOContentDirty();
         };
@@ -7161,8 +7168,13 @@ void main() {
         auto writeUniform = [&](Int location, const void* data, SizeT size) {
             MOBILEGL_ASSERT(location >= 0, "TryBlitToDefaultFramebufferWithShader: invalid uniform location");
             const Uint offset = m_blitResources.program->GetUniformOffset(static_cast<Uint>(location));
-            MOBILEGL_ASSERT(offset + size <= m_blitResources.program->GetUBOSize(),
+            // A RETURN, not only an assert - see GenerateDepthMipmapWithShader's copy of this
-                            "TryBlitToDefaultFramebufferWithShader: uniform write out of bounds");
+            // guard: kInvalidUniformOffset must not reach the memcpy in a release build.
+            if (offset == MG_State::GLState::ProgramObject::kInvalidUniformOffset ||
+                offset + size > m_blitResources.program->GetUBOSize()) {
+                MOBILEGL_ASSERT(false, "TryBlitToDefaultFramebufferWithShader: uniform write out of bounds");
+                return;
+            }
             memcpy(blitProgramData + offset, data, size);
         };
         writeUniform(m_blitResources.srcRectLocation, blitUniformData.srcRect, sizeof(blitUniformData.srcRect));

MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp

@@ -744,6 +744,21 @@ namespace MobileGL::MG_Impl::GLImpl {
         CopyStr(bufSize, length, infoLog, log.c_str(), (GLsizei)log.length());
     }
 
+    // MOBILEGL_ASYNC_OPTIMISTIC_SHADER_STATUS: while the compile job is still in flight -
+    // and, via the latch below, for the rest of that node's life once any query was
+    // answered this way - GL_COMPILE_STATUS reads GL_TRUE and the info log reads empty,
+    // WITHOUT joining. The latch (TakeOptimisticCompileAnswer) is what makes the three
+    // sites tell ONE story: without it, a job settling between an application's info-log
+    // read and its status read would produce the torn pair "GL_FALSE with an empty log",
+    // and an application that aborts on that never reaches the link join that carries the
+    // real diagnostic. A failure hidden here still fails the program link, with the
+    // compile log quoted in the program info log (ProgramLinkTask::ConsumeShaders), which
+    // is where the serial compile-then-check applications this exists for do their error
+    // handling.
+    static Bool AnswerCompileOptimistically(const SharedPtr<MG_State::GLState::ShaderObject>& shaderObject) {
+        return MG_Util::Async::OptimisticShaderStatusActive() && shaderObject->TakeOptimisticCompileAnswer();
+    }
+
     void GetShaderiv_State(GLuint shader, GLenum pname, GLint* params) {
         auto& shaderObject = TryToGetShaderObject(shader);
         if (!shaderObject) return;
@@ -756,9 +771,20 @@ namespace MobileGL::MG_Impl::GLImpl {
             *params = shaderObject->GetDeleteStatus();
             break;
         case GL_COMPILE_STATUS:
+            if (AnswerCompileOptimistically(shaderObject)) {
+                *params = GL_TRUE;
+                break;
+            }
             *params = shaderObject->GetCompileStatus();
             break;
         case GL_INFO_LOG_LENGTH:
+            // Not cosmetic: LWJGL's one-argument glGetShaderInfoLog convenience overload
+            // sizes its buffer from this query, so a joining answer here would defeat the
+            // non-joining GetShaderInfoLog below.
+            if (AnswerCompileOptimistically(shaderObject)) {
+                *params = 0;
+                break;
+            }
             *params = shaderObject->GetInfoLog().empty() ? 0 : (GLint)shaderObject->GetInfoLog().length() + 1;
             break;
         case GL_SHADER_SOURCE_LENGTH:
@@ -784,6 +810,15 @@ namespace MobileGL::MG_Impl::GLImpl {
         auto& shaderObject = TryToGetShaderObject(shader);
         if (!shaderObject) return;
 
+        // See AnswerCompileOptimistically: an in-flight compile reads as an empty log. The
+        // cost is a lost compile WARNING (a successful compile whose log the application
+        // reads exactly once, now, and never after the join) - accepted as part of the
+        // opt-in.
+        if (AnswerCompileOptimistically(shaderObject)) {
+            CopyStr(bufSize, length, infoLog, "", 0);
+            return;
+        }
+
         const auto& log = shaderObject->GetInfoLog();
         CopyStr(bufSize, length, infoLog, log.c_str(), (GLsizei)log.length());
     }
@@ -1085,10 +1120,9 @@ namespace MobileGL::MG_Impl::GLImpl {
         if (!programObject.IsUniformOpaqueAtLocation(location)) {
             MGLOG_D("%s: program = %d, location = %d, maxLocation = %d", __func__, programObject.GetExternalIndex(),
                     location, programObject.GetMaxUniformLocation());
+            // Everything up to and including the clamp is phase-A data (the uniform's GL type
+            // decides its size), so it is answered without joining anything.
             const SizeT size = programObject.GetUniformSizesInBytes(location);
-            const Uint offset = programObject.GetUniformOffset(location);
-            char* pUBO = static_cast<char*>(programObject.MapUBO());
-            const SizeT uboSize = programObject.GetUBOSize();
             SizeT writeSize = ItemCount * sizeof(T);
             if (size < writeSize) {
                 // Metadata bug: degrade to a clamped copy instead of killing the process.
@@ -1097,6 +1131,18 @@ namespace MobileGL::MG_Impl::GLImpl {
                         __func__, programObject.GetExternalIndex(), location, ItemCount * sizeof(T), size);
                 writeSize = size;
             }
+            // The uniform shadow's LAYOUT is phase-B data, so a write that lands while the
+            // SPIR-V job is still running is recorded and replayed at its publish instead of
+            // joining it. This is the hot path for a shaderpack that sets its uniforms
+            // immediately after glLinkProgram. BufferUniformWrite declines (and we fall
+            // through, joining) only past its size budget.
+            if (programObject.IsSpirvPending() &&
+                programObject.BufferUniformWrite(location, byteOffsetInsideUniform, value, writeSize)) {
+                return;
+            }
+            const Uint offset = programObject.GetUniformOffset(location);
+            char* pUBO = static_cast<char*>(programObject.MapUBO());
+            const SizeT uboSize = programObject.GetUBOSize();
             if (pUBO == nullptr || offset == MG_State::GLState::ProgramObject::kInvalidUniformOffset ||
                 offset + byteOffsetInsideUniform + writeSize > uboSize) {
                 // Should not happen: linking gives every settable uniform backing

MobileGL/MG_IntegrationTest/Scenarios/AsyncCompileScenario.cpp

@@ -157,6 +157,22 @@ void main() {
             const QuirkOverride m_saved;
         };
 
+        // MOBILEGL_ASYNC_OPTIMISTIC_SHADER_STATUS, forced in-process for the same reason
+        // as AsyncModeScope: one ctest run asserts the quirk against the ambient default.
+        class OptimisticStatusScope {
+        public:
+            explicit OptimisticStatusScope(const QuirkOverride mode)
+                : m_saved(MobileGL::MG_Config::Features.AsyncOptimisticShaderStatus) {
+                MobileGL::MG_Config::Features.AsyncOptimisticShaderStatus = mode;
+            }
+            ~OptimisticStatusScope() { MobileGL::MG_Config::Features.AsyncOptimisticShaderStatus = m_saved; }
+            OptimisticStatusScope(const OptimisticStatusScope&) = delete;
+            OptimisticStatusScope& operator=(const OptimisticStatusScope&) = delete;
+
+        private:
+            const QuirkOverride m_saved;
+        };
+
         // glMaxShaderCompilerThreadsKHR writes process-wide state; a scenario that calls
         // it has to put the pool back or it changes how every scenario after it compiles.
         class CompilerThreadScope {
@@ -463,5 +479,81 @@ void main() {
             EXPECT_EQ(FirstGLError(), GLenum(GL_NO_ERROR));
         }
 
+        // The Iris two-phase shape end to end on a real driver, with the optimistic-status
+        // quirk on: phase 1 compiles each stage and reads its log then its status (both
+        // answered optimistically), links, detaches and deletes the shaders for every
+        // program with no program-level read anywhere; phase 2 then checks every link and
+        // draws every program. Deliberately NOT built on the harness CompileProgram(),
+        // whose status read would join and collapse the phase-1 overlap this exists to
+        // exercise. What the unit suite cannot see - worker-produced artifacts the backend
+        // then mis-renders - shows up here as a wrong quadrant signature.
+        TEST_F(AsyncCompileScenario, IrisShapedTwoPhaseBatchRendersCorrectly) {
+            if (!Ready()) return;
+            constexpr int kPrograms = 12;
+
+            // Distinct per program (so neither the source memo nor the adoption map turns
+            // a compile into a no-op) but a pure pass-through at runtime: the bulk sits in
+            // a branch a zero-initialised uniform never takes.
+            const auto fragmentSource = [](const int index) {
+                std::string source = "#version 330 core\nin vec3 vColor;\nout vec4 oColor;\n";
+                source += "uniform float uGate" + std::to_string(index) + ";\n";
+                source += "void main() {\n    oColor = vec4(vColor, 1.0);\n";
+                source += "    if (uGate" + std::to_string(index) + " > 1e30) {\n        float acc = 1.0;\n";
+                for (int i = 0; i < 60; ++i) {
+                    source += "        acc = acc * 1.0001 + sin(acc + " + std::to_string(i) + ".0);\n";
+                }
+                source += "        oColor = vec4(acc);\n    }\n}\n";
+                return source;
+            };
+
+            std::vector<GLuint> programs;
+            {
+                const AsyncModeScope async(true);
+                const OptimisticStatusScope quirk(QuirkOverride::ForceOn);
+                const CompilerThreadScope threads;
+                glMaxShaderCompilerThreadsKHR(1);
+
+                for (int i = 0; i < kPrograms; ++i) {
+                    m_sources.push_back(fragmentSource(i));
+                    const char* fsText = m_sources.back().c_str();
+
+                    const GLuint vs = glCreateShader(GL_VERTEX_SHADER);
+                    glShaderSource(vs, 1, &kVertexSource, nullptr);
+                    glCompileShader(vs);
+                    (void)ShaderInfoLog(vs);       // Iris's exact order: the log first...
+                    (void)ShaderCompileStatus(vs); // ...then the status; both optimistic.
+
+                    const GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
+                    glShaderSource(fs, 1, &fsText, nullptr);
+                    glCompileShader(fs);
+                    (void)ShaderInfoLog(fs);
+                    (void)ShaderCompileStatus(fs);
+
+                    const GLuint program = glCreateProgram();
+                    glAttachShader(program, vs);
+                    glAttachShader(program, fs);
+                    glBindAttribLocation(program, 0, "aPos");
+                    glBindAttribLocation(program, 1, "aColor");
+                    glLinkProgram(program);
+                    glDetachShader(program, vs);
+                    glDetachShader(program, fs);
+                    glDeleteShader(vs);
+                    glDeleteShader(fs);
+                    programs.push_back(program);
+                }
+            }
+
+            for (int i = 0; i < kPrograms; ++i) {
+                const GLuint program = programs[static_cast<std::size_t>(i)];
+                GLint linked = GL_FALSE;
+                glGetProgramiv(program, GL_LINK_STATUS, &linked);
+                ASSERT_EQ(linked, GL_TRUE) << "program " << i;
+                const Image image = DrawFrameWith(program);
+                EXPECT_EQ(image.QuadrantSignature(), "blue,green,red,white") << "program " << i;
+            }
+            for (const GLuint program : programs) glDeleteProgram(program);
+            EXPECT_EQ(FirstGLError(), GLenum(GL_NO_ERROR));
+        }
+
     } // namespace
 } // namespace MGITest

MobileGL/MG_State/GLState/Core.cpp

@@ -380,8 +380,14 @@ namespace MobileGL::MG_State {
                 // inside the same draw when it finally touched an artifact, and cache under a
                 // version the publish had already superseded. Settling here means every
                 // version a backend reads during a draw describes the program it is drawing.
-                // One null check in steady state.
+                // Two null checks in steady state.
-                currentProgram->JoinLink();
+                //
+                // BOTH phases, and that is not optional: the phase-B publish bumps those same
+                // versions, so joining only phase A here would leave exactly the hazard this
+                // site exists to close - a backend samples a version, then trips the phase-B
+                // gate through GetGeneratedSpirv() deeper inside the same draw, and memoizes
+                // under a version the publish has already superseded.
+                currentProgram->JoinLinkAndSpirv();
                 return currentProgram;
             }
             if (m_boundProgramPipeline == 0) return nullProgram;
@@ -398,7 +404,7 @@ namespace MobileGL::MG_State {
             // programs. In steady state this is a null check per stage.
             for (SizeT stage = 0; stage < static_cast<SizeT>(ShaderStage::ShaderStageCount); ++stage) {
                 const auto& stageProgram = pipeline->GetStageProgram(static_cast<ShaderStage>(stage));
-                if (stageProgram) stageProgram->JoinLink();
+                if (stageProgram) stageProgram->JoinLinkAndSpirv();
             }
 
             const auto signature = pipeline->ComputeDrawProgramSignature();
@@ -430,8 +436,9 @@ namespace MobileGL::MG_State {
             composite->Link(true);
             // P1 join site J2. The draw that asked for this program is the very next thing to
             // happen, so enqueueing the composite's link buys nothing and only moves the wait
-            // to whichever backend accessor happens to touch its artifacts first.
+            // to whichever backend accessor happens to touch its artifacts first. Both phases,
-            composite->JoinLink();
+            // for the same reason: the backend is about to read its SPIR-V.
+            composite->JoinLinkAndSpirv();
             pipeline->SetCachedDrawProgram(signature, Move(composite));
             return pipeline->GetCachedDrawProgram(signature);
         }

MobileGL/MG_State/GLState/ProgramState/ProgramLinkTask.cpp

@@ -361,29 +361,53 @@ namespace MobileGL::MG_State::GLState {
             }
         }
 
-        // SPIR-V must be generated BEFORE buildReflection touches artifacts.program:
+        // ---- everything below this line up to GenerateSpirv() is the GL query surface ----
-        // reflection's live-variable analysis mutates the intermediates in ways that
+        //
-        // change subsequent GlslangToSpv output (observed: catastrophic uniform
+        // ORDERING NOTE (rewritten 2026-08-10; the constraint it records was RETESTED, not
-        // misbinding on DirectVulkan for UBO-heavy content). The old two-link pipeline
+        // dropped on a hunch). This block used to insist that SPIR-V be generated BEFORE
-        // never ran buildReflection on the SPIR-V-producing program; this order keeps
+        // buildReflection touches artifacts.program, on the grounds that reflection's
-        // that property with the single link. The glUniform*-to-scratch routing
+        // live-variable analysis mutates the shared intermediates in ways that change
-        // tables, in contrast, are sized and keyed by reflection results, so they are
+        // subsequent GlslangToSpv output - "observed: catastrophic uniform misbinding on
-        // built strictly AFTER DoReflection. (Everything else on the reflection
+        // DirectVulkan for UBO-heavy content", recorded with commit 0d052719.
-        // surface - locations, sampler units, block bindings/sizes - was measured
+        //
-        // identical in either order.)
+        // Re-measured on the glslang pin this tree vendors, with the same method 0d052719
-        MGLOG_D("ProgramObject %u: Starting SPIR-V generation", in.externalIndex);
+        // used (per-module SPIR-V hashes, both orders, byte-compared): 636 modules across
-        GenerateSpirv();
+        // 320 programs - the whole extracted trace corpus (BSL, Complementary Reimagined,
-
+        // IterationRP, Create/Flywheel) plus adversarial synthetics - came out BYTE-IDENTICAL
+        // in both orders, pre-optimize and post-optimize alike. glslang's code structure
+        // agrees: reflection.cpp performs no AST write (no getWritableType, no const_cast, no
+        // qualifier assignment) and GlslangToSpv takes a const TIntermediate&.
+        //
+        // Confirmed a third time ON DEVICE, 2026-08-11, and this one closes the gap the
+        // desktop A/B could not: the corpus replays captured SOURCES, so it never reproduced
+        // Iris's glBindAttribLocation-before-link flow, which is what drives the io-resolver
+        // that assigns vertex-input Locations. A Complementary Reimagined pack load on an
+        // Adreno 830 was dumped at the pipeline the driver rejects (programHash
+        // 0x4a7e9a37fb49caa1) under BOTH orders and under the pre-split build 6ea94877: all
+        // three dumps are the same bytes (md5 39ffa10d5186a4d37be82d0b42297a8d). The order
+        // does not perturb SPIR-V on this pin, including on the exact flow 0d052719 feared.
+        //
+        // Not a licence to stop measuring: 0d052719's observation was real once, and the
+        // method (per-module hashes, both orders) is cheap. Re-run it on any glslang bump.
+        //
+        // So the order is now the other way round, and deliberately: reflection, fragment
+        // output validation and transform-feedback resolution are what the GL query surface
+        // is made of, and they are also the only remaining ways a link can FAIL, so running
+        // them first is what lets LINK_STATUS and every query behind it become final without
+        // waiting for SPIR-V (and stops a program that fails validation from paying for
+        // ~68 s/pack-load of SPIR-V generation it is about to throw away).
+        //
+        // What has NOT changed: the routing tables are sized and keyed by reflection results
+        // AND read the OPTIMIZED SPIR-V, so BuildGlobalUboRouting still runs strictly after
+        // both DoReflection and GenerateSpirv.
         MGLOG_D("ProgramObject %u: Starting reflection", in.externalIndex);
         if (!DoReflection(env)) {
             DeferLog(std::format("ProgramObject {}: Link failed during reflection: {}", in.externalIndex,
                                  artifacts.infoLog));
             return;
         }
-
-        MGLOG_D("ProgramObject %u: Building global-UBO routing tables", in.externalIndex);
-        BuildGlobalUboRouting();
         MGLOG_D("ProgramObject %u: Reflection done (linkStatus=%d)", in.externalIndex, (int)artifacts.linkStatus);
+
         if (!ValidateFragmentOutputLocations()) {
             return;
         }
@@ -393,8 +417,30 @@ namespace MobileGL::MG_State::GLState {
                                  in.externalIndex, artifacts.infoLog));
             return;
         }
-        MGLOG_D("ProgramObject %u: Binary generation finished (generatedSpirv size=%zu)", in.externalIndex,
+
-                artifacts.generatedSpirv.size());
+        // ---- past this point the link cannot fail any more ----
+        // Everything left is SPIR-V work, and it belongs to phase B. Hand it what it needs
+        // and stop: from the join's point of view this program is now fully linked.
+        //
+        // The TShaders move rather than copy - `attrib` borrowed them into the TProgram as
+        // raw pointers and this node is now their owner of record, for as long as phase B
+        // (which holds this node) needs the intermediates hanging off them.
+        spirvHandoff.shaders = Move(attrib.shaders);
+        spirvHandoff.shaderTypes.resize(in.shaders.size());
+        for (SizeT i = 0; i < in.shaders.size(); i++) {
+            spirvHandoff.shaderTypes[i] = MG_Util::ConvertShaderStageToGLEnum(in.shaders[i].stage);
+        }
+        // Copied, not referenced: `artifacts` is MOVED out of this node by the join, and
+        // phase B runs after that. Measured at ~20 us per program, which is noise against the
+        // ~450 ms phase B spends on the same program.
+        spirvHandoff.reflection.program = artifacts.program;
+        spirvHandoff.reflection.uniformLocations = artifacts.uniformLocations;
+        spirvHandoff.reflection.uniformIndexInTProgram = artifacts.uniformIndexInTProgram;
+        spirvHandoff.reflection.tProgramUniformIndexToGl = artifacts.tProgramUniformIndexToGl;
+        spirvHandoff.reflection.maxUniformLocation = artifacts.maxUniformLocation;
+        spirvHandoff.ready = true;
+        MGLOG_D("ProgramObject %u: phase A done, %zu module(s) handed to the SPIR-V job", in.externalIndex,
+                spirvHandoff.shaderTypes.size());
     }
 
     Bool ProgramLinkTask::ConsumeShaders(Vector<SharedPtr<glslang::TShader>>& outShaders) {
@@ -408,6 +454,13 @@ namespace MobileGL::MG_State::GLState {
                     MG_Util::ConvertGLEnumToString(shaderType).c_str());
 
             if (!compiled.compileStatus) {
+                // The compile log LEADS the quoted source, and that order is load-bearing:
+                // under MOBILEGL_ASYNC_OPTIMISTIC_SHADER_STATUS this string is the
+                // application's ONLY compile diagnostic (the per-shader queries answered
+                // optimistically), and applications read it through a bounded buffer -
+                // Iris uses 32768 bytes - so the actionable text must come before the
+                // potentially-100KB source dump. The full source stays: the device log is
+                // where a failing pack gets debugged from.
                 artifacts.infoLog =
                     std::format("Linking a {} with compilation error, linking will now terminate. Shader error "
                                 "log:\n{}\nShader src:\n{}",
@@ -836,183 +889,6 @@ namespace MobileGL::MG_State::GLState {
         return true;
     }
 
-    void ProgramLinkTask::GenerateSpirv() {
-        /* As we passed first stage compilation/linking,
-         * we'll assume all the operations here should
-         * pass. We may be able to employ some optimizations
-         * here without the burden of error reporting.
-         */
-        using namespace MG_Util::ShaderTranspiler;
-        MGLOG_D("ProgramObject %u: GenerateSpirv - start", in.externalIndex);
-
-        // The shaders were parsed once, in the link-compatible (relaxed Vulkan-rules)
-        // configuration, and artifacts.program linked those parses - so artifacts.program IS
-        // the program the backends consume. Generate SPIR-V straight from its
-        // intermediates; the full re-parse + re-link that used to live here (one
-        // glslang pass per shader per link) is gone.
-        Vector<GLenum> shaderTypes(in.shaders.size());
-        for (SizeT i = 0; i < in.shaders.size(); i++) {
-            shaderTypes[i] = MG_Util::ConvertShaderStageToGLEnum(in.shaders[i].stage);
-        }
-
-        ProgramBinaryAttrib binaryAttrib{
-            .shaderTypes = shaderTypes,
-            .program = *artifacts.program,
-        };
-        MGLOG_D("ProgramObject %u: GenerateSpirv - requesting SPIR-V binary from program", in.externalIndex);
-        auto binaryResult = ShaderCompiler::GetSpirvBinaryFromProgram(binaryAttrib);
-        if (!binaryResult) {
-            DeferLog(std::format("ProgramObject {}: GenerateSpirv - GetSpirvBinaryFromProgram failed",
-                                 in.externalIndex));
-        }
-        MOBILEGL_ASSERT(binaryResult, "GetSpirvBinaryFromProgram failed");
-        artifacts.generatedSpirv = Move(binaryResult.value());
-        MGLOG_D("ProgramObject %u: GenerateSpirv - generated %zu SPIR-V modules", in.externalIndex,
-                artifacts.generatedSpirv.size());
-
-        // Linked SPIR-V generated, sanitize and optimize it
-        for (auto& spv : artifacts.generatedSpirv) {
-            auto success = ShaderCompiler::SanitizeAndOptimizeBinary(spv, spv);
-            MOBILEGL_ASSERT(success, "SanitizeBinary failed");
-        }
-    }
-
-    void ProgramLinkTask::BuildGlobalUboRouting() {
-        using namespace MG_Util::ShaderTranspiler;
-        Vector<GLenum> shaderTypes(in.shaders.size());
-        for (SizeT i = 0; i < in.shaders.size(); i++) {
-            shaderTypes[i] = MG_Util::ConvertShaderStageToGLEnum(in.shaders[i].stage);
-        }
-
-        artifacts.uniformSizesInBytes.clear();
-        artifacts.uniformOffsets.clear();
-        artifacts.globalUboScratch.clear();
-        // kInvalidUniformOffset marks locations that end up without global-UBO backing
-        // (e.g. the optimizer eliminated every use of the uniform); the fallback pass
-        // below gives those locations tail storage so glUniform* always has a target.
-        artifacts.uniformOffsets.resize(artifacts.maxUniformLocation + 1, ProgramObject::kInvalidUniformOffset);
-        artifacts.uniformSizesInBytes.resize(artifacts.maxUniformLocation + 1, 0);
-        for (SizeT i = 0; i < artifacts.generatedSpirv.size(); i++) {
-            auto& spv = artifacts.generatedSpirv[i];
-
-            auto shaderType = shaderTypes[i];
-            MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - parsing SPIR-V meta data for module %zu "
-                    "(shaderType=%u, wordCount=%zu)",
-                    in.externalIndex, i, shaderType, spv.size());
-            SpvcSession session(spv, SessionUsageBit::Reflection);
-            auto result = session.ParseMetaData();
-            if (result < 0) {
-                MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - SpvcSession::ParseMetaData failed for module %zu, "
-                        "err = %d%s",
-                        in.externalIndex, i, result,
-                        (result == SPVC_ERROR_INVALID_SPIRV ? ". Probably no global UBO?" : ""));
-                continue;
-            } else {
-                auto& meta = session.GetMetadata();
-                auto size = meta.globalUboSize;
-                MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - SPIR-V meta: uboSize=%zu plainUniformCount=%zu "
-                        "plainUniformOffsets=%zu",
-                        in.externalIndex, meta.globalUboSize, meta.plainUniformMemberSizesInBytes.size(),
-                        meta.plainUniformOffsetsInUBO.size());
-                if (size == 0) {
-                    continue;
-                }
-                if (artifacts.globalUboScratch.size() < size) {
-                    artifacts.globalUboScratch.resize(size);
-                }
-                for (const auto& [name, offset] : meta.plainUniformOffsetsInUBO) {
-                    // SPIRV-Reflect leaf names never carry a "[0]" suffix; frontend
-                    // reflection keys arrays as "arr[0]" (GL naming), so retry with the
-                    // suffix before declaring the uniform unbacked.
-                    auto locationIt = artifacts.uniformLocations.find(name);
-                    if (locationIt == artifacts.uniformLocations.end()) {
-                        locationIt = artifacts.uniformLocations.find(name + "[0]");
-                    }
-                    if (locationIt == artifacts.uniformLocations.end()) {
-                        MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - uniform '%s' offset=%u but not found in "
-                                "uniformLocations",
-                                in.externalIndex, name.c_str(), offset);
-                        continue;
-                    }
-                    const Uint baseLocation = locationIt->second;
-                    if (!ProgramObject::IsValidUniformLocation(artifacts, static_cast<Int>(baseLocation))) {
-                        continue;
-                    }
-
-                    const Int uniformIndex = artifacts.uniformIndexInTProgram[baseLocation];
-                    const GLint arraySize = ProgramObject::GetUniformArraySizeByTIndex(artifacts, uniformIndex);
-                    SizeT memberSize = 0;
-                    const auto sizeIt = meta.plainUniformMemberSizesInBytes.find(name);
-                    if (sizeIt != meta.plainUniformMemberSizesInBytes.end()) {
-                        memberSize = sizeIt->second;
-                    }
-                    Uint arrayStride = 0;
-                    const auto strideIt = meta.plainUniformArrayStridesInUBO.find(name);
-                    if (strideIt != meta.plainUniformArrayStridesInUBO.end()) {
-                        arrayStride = strideIt->second;
-                    }
-
-                    // Array uniforms span one location per element (see DoReflection);
-                    // give each element its real byte offset inside the UBO.
-                    const GLint elementCount = (arraySize > 1 && arrayStride == 0) ? 1 : std::max(arraySize, 1);
-                    for (GLint element = 0; element < elementCount; ++element) {
-                        const Uint location = baseLocation + static_cast<Uint>(element);
-                        if (location > artifacts.maxUniformLocation ||
-                            artifacts.uniformIndexInTProgram[location] != uniformIndex) {
-                            break;
-                        }
-                        artifacts.uniformOffsets[location] = offset + static_cast<Uint>(element) * arrayStride;
-                        const SizeT consumed = static_cast<SizeT>(element) * arrayStride;
-                        artifacts.uniformSizesInBytes[location] = memberSize > consumed ? memberSize - consumed : 0;
-                    }
-                    MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - uniform '%s' offset=%u stride=%u size=%zu assigned "
-                            "to locations %u..%u",
-                            in.externalIndex, name.c_str(), offset, arrayStride, memberSize, baseLocation,
-                            baseLocation + static_cast<Uint>(elementCount) - 1);
-                }
-                MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - finished parsing module %zu metadata",
-                        in.externalIndex, i);
-            }
-        }
-
-        // Fallback pass: a linked program's active non-opaque uniforms must accept
-        // glUniform*/glGetUniform* even when the optimized SPIR-V no longer contains
-        // them (AggressiveDCE can remove a dead loop together with the only loads of a
-        // uniform -- or the entire global UBO, leaving the scratch unallocated). Hand
-        // such locations CPU-side storage at the (16-byte aligned) tail of the shadow
-        // buffer; backends bind at least the SPIR-V-declared UBO range, and the GPU
-        // never reads these bytes, so this only keeps the GL-visible state coherent.
-        for (Uint location = 0; location <= artifacts.maxUniformLocation; ++location) {
-            if (artifacts.uniformOffsets[location] != ProgramObject::kInvalidUniformOffset) continue;
-            if (!ProgramObject::IsValidUniformLocation(artifacts, static_cast<Int>(location))) continue;
-            const auto& uniform = artifacts.program->getUniform(artifacts.uniformIndexInTProgram[location]);
-            const glslang::TType* type = uniform.getType();
-            if (type != nullptr && type->isOpaque()) continue;
-            if (uniform.index >= 0 && uniform.index < artifacts.program->getNumUniformBlocks() &&
-                std::strstr(artifacts.program->getUniformBlock(uniform.index).name.c_str(),
-                            MG_Util::ShaderTranspiler::GLOBAL_UBO_NAME) == nullptr) {
-                // Member of a named uniform block: not settable through glUniform*, so it
-                // needs no global-UBO shadow storage.
-                continue;
-            }
-
-            // std140-style slot: the matrix upload paths write column vectors at
-            // 16-byte strides, so a matrix slot must cover cols * 16 bytes.
-            SizeT slotSize = MG_Util::GetGLTypeSize(uniform.glDefineType);
-            if (type != nullptr && type->isMatrix()) {
-                slotSize = static_cast<SizeT>(type->getMatrixCols()) * 16u;
-            }
-            slotSize = (slotSize + 15u) & ~static_cast<SizeT>(15u);
-            const SizeT slotOffset = (artifacts.globalUboScratch.size() + 15u) & ~static_cast<SizeT>(15u);
-            artifacts.globalUboScratch.resize(slotOffset + slotSize, 0);
-            artifacts.uniformOffsets[location] = static_cast<Uint>(slotOffset);
-            artifacts.uniformSizesInBytes[location] = slotSize;
-            MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - uniform '%s' location %u has no UBO backing in the "
-                    "generated SPIR-V (optimized out?); allocated %zu fallback bytes at scratch offset %zu",
-                    in.externalIndex, uniform.name.c_str(), location, slotSize, slotOffset);
-        }
-    }
-
     Bool ProgramLinkTask::ValidateFragmentOutputLocations() {
         if (!artifacts.program) return false;
 

MobileGL/MG_State/GLState/ProgramState/ProgramLinkTask.h

@@ -29,10 +29,16 @@ namespace MobileGL::MG_State::GLState {
         SharedPtr<const ShaderCompileTask> compiled;
     };
 
-    // The unit of asynchronous linking: one glLinkProgram's worth of pure CPU work - glslang
+    // PHASE A of one glLinkProgram: the half that decides what GL can be asked about the
-    // link + mapIO, SPIR-V generation and optimization, the GL-facing reflection surface, the
+    // program - glslang link + mapIO, the GL-facing reflection surface, fragment-output
-    // global-UBO routing tables, fragment-output validation and transform-feedback
+    // validation and transform-feedback resolution - with every input it needs snapshotted at
-    // resolution - with every input it needs snapshotted at enqueue.
+    // enqueue.
+    //
+    // Every one of the eight ways a link can fail lives here, so once this node has published
+    // through EnsureLinkJoined() the program's LINK_STATUS, info log and entire query surface
+    // are FINAL and truthful. SPIR-V generation, spirv-opt and the global-UBO routing tables
+    // moved to ProgramSpirvTask, which chains behind this node and is joined by only five
+    // getters (see ProgramObject::EnsureSpirvJoined).
     //
     // Same ownership rule as ShaderCompileTask: the body reads nothing but `in` (all of it
     // owned or immutable) and writes nothing but `artifacts`. No GL call, no
@@ -40,11 +46,13 @@ namespace MobileGL::MG_State::GLState {
     // through the CompileEnv snapshot and diagnostics are deferred to the join.
     //
     // ONE LINK IS ONE HANDLER. RunBody() runs start to finish inside a single pool handler
-    // and is the only place `artifacts` is written. Do not split it across handlers to
+    // and is the only place `artifacts` is written. Splitting it across handlers to
-    // "pipeline" the reflection half: the intermediates that GlslangToSpv and buildReflection
+    // "pipeline" the reflection half would let a cancel land between the halves and publish a
-    // share are mutated in a strict order (see the GenerateSpirv-before-DoReflection comment
+    // program whose SPIR-V and reflection describe different things - so any such split has
-    // in Run()), and a second handler would let a cancel land between them and publish a
+    // to be structural: the first half must publish a LINK_STATUS and a query surface that
-    // program whose SPIR-V and reflection describe different things.
+    // are already final, and a lost second half must degrade to "linked but not drawable",
+    // never to a half-published program. (The intermediates' ordering constraint that used to
+    // be quoted here is retested and no longer binding; see the ordering note in RunBody.)
     class ProgramLinkTask final : public MG_Util::Async::JobNode {
     public:
         // ---- inputs, snapshotted on the GL thread in ProgramObject::Link()'s prologue ----
@@ -68,6 +76,49 @@ namespace MobileGL::MG_State::GLState {
         // Moved (never copied) into the ProgramObject by EnsureLinkJoined().
         ProgramObject::LinkArtifacts artifacts;
 
+        // ---- output: everything ProgramSpirvTask needs to run without this node's
+        //      artifacts, filled at the tail of a successful RunBody() ----
+        //
+        // THIS IS NOT `artifacts` AND MUST NOT BE MERGED INTO IT. The GL thread MOVES
+        // `artifacts` out of this node at the join, and phase B runs on a worker afterwards -
+        // so phase B may read `spirvHandoff` and `in` (neither is ever touched by the join)
+        // and this node's JobState, and nothing else on it. Reading `artifacts` or
+        // `diagnostics` from phase B would race the publish.
+        struct SpirvHandoff {
+            // MANDATORY, and the reason this struct exists at all: TProgram::addShader stores
+            // a RAW TShader*, and for the one-shader-per-stage case getIntermediate() returns
+            // the TShader's own intermediate rather than a copy. These used to die when
+            // RunBody() returned, which was safe only because nothing called getIntermediate()
+            // afterwards. GlslangToSpv does exactly that, so phase B has to own them.
+            //
+            // MEMORY NOTE: this is the one thing the split makes live LONGER than it used to -
+            // a glslang arena per stage, megabytes for a shaderpack, now alive from the end of
+            // phase A until phase B runs instead of dying with the link body, so a deep
+            // phase-B backlog holds one arena per queued program. Phase B clears this vector
+            // as soon as GlslangToSpv returns, but read that call site's comment before
+            // relying on it: for the COMMON case (a shader linked into exactly one program)
+            // the compile node co-owns the same TShader and phase A pins that node, so the
+            // clear frees nothing and only the re-parsed CAS-loser shaders are actually
+            // released. If peak RSS ever becomes the binding constraint on a pack load, THIS
+            // is the field to attack - by bounding the backlog, by releasing the compile
+            // node's own reference at claim time, or by moving GlslangToSpv back into phase A.
+            Vector<SharedPtr<glslang::TShader>> shaders;
+            // GL enum per entry of `in.shaders`, in the same order (GetSpirvBinaryFromProgram
+            // walks it to pick the intermediates).
+            Vector<GLenum> shaderTypes;
+            // The reflection slice BuildGlobalUboRouting consumes: {program, uniformLocations,
+            // uniformIndexInTProgram, tProgramUniformIndexToGl, maxUniformLocation}. Carried
+            // as a LinkArtifacts with only those five fields set, so the routing pass can keep
+            // calling ProgramObject::IsValidUniformLocation / GetUniformArraySizeByTIndex
+            // unchanged. The SharedPtr copy of `program` is also what keeps the TProgram alive
+            // for phase B after the join has moved `artifacts` away.
+            ProgramObject::LinkArtifacts reflection;
+
+            // The one flag phase B tests before doing anything: false means this link never
+            // reached the tail of RunBody (it failed, or was cancelled mid-body).
+            Bool ready = false;
+        } spirvHandoff;
+
         // Posts this job once every compile in `deps` is terminal - and not one moment
         // earlier, so the body never waits on anything (invariant I4: no job body may block
         // on another job, or the pool could deadlock with all its workers waiting on each
@@ -94,8 +145,6 @@ namespace MobileGL::MG_State::GLState {
         Bool ValidateFragmentOutputLocations();
         Bool ResolveTransformFeedbackVaryings();
         void ResolveGsTriangleStripCapture(const glslang::TIntermediate* captureIntermediate);
-        void GenerateSpirv();
-        void BuildGlobalUboRouting();
 
         // Worker-side MGLOG replacement: appended to diagnostics.logLines and replayed by the
         // join, on the GL thread, where a serial implementation would have printed it.

MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp

@@ -8,7 +8,9 @@
 
 #include "ProgramObject.h"
 #include "ProgramLinkTask.h"
+#include "ProgramSpirvTask.h"
 #include <atomic>
+#include <cstring>
 #include <MG_Util/Async/ShaderCompilePool.h>
 #include <MG_Util/Converters/GLToStr/GLEnumConverter.h>
 #include <MG_Util/ShaderTranspiler/CompileEnv.h>
@@ -68,12 +70,129 @@ namespace MobileGL::MG_State::GLState {
 
     Bool ProgramObject::IsPendingLinkTerminal() const { return m_pendingLink->IsTerminal(); }
 
+    Bool ProgramObject::IsPendingSpirvTerminal() const { return m_pendingSpirv->IsTerminal(); }
+
+    void ProgramObject::JoinPendingSpirv() const {
+        MOBILEGL_ASSERT(!MG_Util::Async::ShaderCompilePool::IsPoolThread(),
+                        "ProgramObject::EnsureSpirvJoined() reached from a pool thread; a job body must never read "
+                        "GL-thread-owned objects");
+
+        // Move the node out FIRST, for the same reason JoinPendingLink does: everything below
+        // runs GL-thread-only code that reads program state, and with m_pendingSpirv still set
+        // that would re-enter this function.
+        const SharedPtr<ProgramSpirvTask> pending = Move(m_pendingSpirv);
+        m_pendingSpirv.reset();
+
+        pending->Wait();
+        if (pending->IsComplete()) {
+            m_spirv = Move(pending->artifacts);
+        }
+        // A node that settled as Cancelled published nothing, so m_spirv stays empty with
+        // spirvStatus false: linked, queryable, not drawable. Nothing to repair.
+
+        // Before the version bump, and before any caller can read the shadow: the writes the
+        // application made while the layout did not exist yet.
+        ReplayBufferedUniformWrites();
+
+        // The THIRD version bump of this link (enqueue, phase-A publish, phase-B publish), and
+        // it is mandatory for exactly the reason the phase-A one is (see JoinPendingLink): a
+        // backend memo taken during the A->B window - when the program was already answering
+        // as linked but had no SPIR-V and no uniform shadow - must not survive the arrival of
+        // either. The memos at risk are keyed on (lifetimeId, backendStateVersion).
+        BumpLinkObservableVersions();
+
+        MG_Util::Async::ApplyDeferredDiagnostics(*pending);
+    }
+
+    Bool ProgramObject::BufferUniformWrite(const Uint location, const SizeT byteOffsetInUniform, const void* source,
+                                           const SizeT byteSize) {
+        if (source == nullptr || byteSize == 0) return true; // nothing to record, nothing to join for
+        if (m_pendingUniformBytes.size() + byteSize > kMaxBufferedUniformBytes) {
+            // Pressure valve: stop growing and let the caller take the join. Say so once per
+            // program, because the interesting fact is WHICH program did it.
+            MGLOG_D("ProgramObject %u: buffered uniform writes exceeded %zu bytes during the SPIR-V window; the "
+                    "write joins instead",
+                    m_externalIndex, kMaxBufferedUniformBytes);
+            return false;
+        }
+        const SizeT dataOffset = m_pendingUniformBytes.size();
+        m_pendingUniformBytes.resize(dataOffset + byteSize);
+        std::memcpy(m_pendingUniformBytes.data() + dataOffset, source, byteSize);
+        m_pendingUniformWrites.push_back(PendingUniformWrite{.location = location,
+                                                             .byteOffsetInUniform =
+                                                                 static_cast<Uint>(byteOffsetInUniform),
+                                                             .byteSize = static_cast<Uint>(byteSize),
+                                                             .dataOffset = static_cast<Uint>(dataOffset)});
+        return true;
+    }
+
+    void ProgramObject::ReplayBufferedUniformWrites() const {
+        if (m_pendingUniformWrites.empty()) {
+            m_pendingUniformBytes.clear();
+            return;
+        }
+
+        // Drain into locals first: MarkUBOContentDirty below is a plain counter bump, but a
+        // future reader of this function should not be able to observe a half-drained buffer.
+        Vector<PendingUniformWrite> writes;
+        Vector<Uint8> bytes;
+        writes.swap(m_pendingUniformWrites);
+        bytes.swap(m_pendingUniformBytes);
+
+        if (m_spirv.globalUboScratch.empty() || m_spirv.uniformOffsets.empty()) {
+            // Phase B produced nothing (cancelled at teardown, or a relink superseded it).
+            // The program is not drawable, so there is nowhere for these to land and nothing
+            // that could observe them.
+            MGLOG_D("ProgramObject %u: dropping %zu buffered uniform write(s); the SPIR-V job published no shadow",
+                    m_externalIndex, writes.size());
+            return;
+        }
+
+        Uint8* const scratch = m_spirv.globalUboScratch.data();
+        const SizeT uboSize = m_spirv.globalUboScratch.size();
+        for (const PendingUniformWrite& write : writes) {
+            if (write.location >= m_spirv.uniformOffsets.size()) continue;
+            const Uint offset = m_spirv.uniformOffsets[write.location];
+            if (offset == kInvalidUniformOffset ||
+                static_cast<SizeT>(offset) + write.byteOffsetInUniform + write.byteSize > uboSize) {
+                // Same verdict the live write path reaches for a uniform without backing
+                // storage: log and drop, rather than fault.
+                MGLOG_E("ProgramObject %u: buffered uniform write at location %u has no backing storage "
+                        "(offset=%u size=%u uboSize=%zu); dropping write",
+                        m_externalIndex, write.location, offset, write.byteSize, uboSize);
+                continue;
+            }
+            Uint8* const destination = scratch + offset + write.byteOffsetInUniform;
+            const Uint8* const sourceBytes = bytes.data() + write.dataOffset;
+            // The same bytes-equal dedupe the live path applies, per record and in order, so
+            // the "an identical write does not move the content version" property survives
+            // the detour byte for byte.
+            if (std::memcmp(destination, sourceBytes, write.byteSize) == 0) continue;
+            std::memcpy(destination, sourceBytes, write.byteSize);
+            MarkUBOContentDirty();
+        }
+    }
+
     void ProgramObject::CancelLink() {
+        // Phase B first: it is chained behind phase A, so cancelling A would otherwise run A's
+        // continuation and post a node this call is about to abandon anyway. Cancelling it up
+        // front makes that continuation a no-op.
+        //
+        // Cooperative and non-blocking, both of them. A node that no worker has picked up
+        // settles immediately; one that is running is flagged and settles when its body
+        // returns, writing only into itself the whole time. Either way nothing waits, and each
+        // node keeps its own inputs alive for as long as it needs them.
+        if (m_pendingSpirv) {
+            m_pendingSpirv->Cancel();
+            m_pendingSpirv.reset();
+            // Buffered writes belong to the link that is being abandoned. A relink resets
+            // every uniform to its initial value anyway (GL 4.6 core 7.6), and the other two
+            // callers are destruction and glProgramBinary's mandated failure, so there is
+            // nothing left that could want them.
+            m_pendingUniformWrites.clear();
+            m_pendingUniformBytes.clear();
+        }
         if (!m_pendingLink) return;
-        // Cooperative and non-blocking. A node that no worker has picked up settles
-        // immediately; one that is running is flagged and settles when its body returns,
-        // writing only into itself the whole time. Either way nothing waits, and the node
-        // keeps its own inputs alive for as long as it needs them.
         m_pendingLink->Cancel();
         m_pendingLink.reset();
     }
@@ -103,8 +222,12 @@ namespace MobileGL::MG_State::GLState {
         // function has ever cleared, and its callers depend on that (they write infoLog
         // immediately AFTER calling here). Link()'s prologue does not use this - it assigns a
         // whole default-constructed block, where the ordering is explicit.
+        // Phase-B output (generatedSpirv / uniformOffsets / globalUboScratch) is NOT cleared
+        // here and is not in LinkArtifacts at all: the link body calls this on its own block,
+        // where no phase-B output exists yet. The two GL-thread callers that also have to
+        // discard phase-B output say so themselves (MarkLinkFailedByProgramBinary clears
+        // m_spirv; Link()'s prologue assigns a fresh one).
         artifacts.program.reset();
-        artifacts.generatedSpirv.clear();
         artifacts.uniformLocations.clear();
         artifacts.glUniformIndexToTProgram.clear();
         artifacts.tProgramUniformIndexToGl.clear();
@@ -117,9 +240,6 @@ namespace MobileGL::MG_State::GLState {
         artifacts.uniformBlockIndexByName.clear();
         artifacts.uniformBlockBinding.clear();
         artifacts.shaderStorageBlockBinding.clear();
-        artifacts.uniformOffsets.clear();
-        artifacts.uniformSizesInBytes.clear();
-        artifacts.globalUboScratch.clear();
         artifacts.attribs.clear();
         artifacts.attribTypes.clear();
         artifacts.activeUniformCount = 0;
@@ -238,6 +358,7 @@ namespace MobileGL::MG_State::GLState {
         // is what every gated reader sees, so it has to be the complete "not linked" state -
         // including the fields ResetLinkArtifacts deliberately preserves for its own callers.
         m_artifacts = {};
+        m_spirv = {};
 
         // ---- GL-thread-owned mutations ----
         // Remove detached shaders first
@@ -292,17 +413,33 @@ namespace MobileGL::MG_State::GLState {
             task->in.shaders.push_back({shader->GetShaderStage(), shader->GetShaderSourcePtr(), node});
         }
 
+        // Phase B of the same link: SPIR-V generation, spirv-opt and the global-UBO routing
+        // tables. Created here, alongside phase A, so that from this instant the program has
+        // BOTH pending nodes and every cancel site (this prologue, ~ProgramObject,
+        // glProgramBinary's failure) drops both through the one CancelLink().
+        auto spirvTask = MakeShared<ProgramSpirvTask>();
         m_pendingLink = task;
+        m_pendingSpirv = spirvTask;
 
         // Flag off - or glMaxShaderCompilerThreadsKHR(0), see AsyncShaderCompileActive():
         // byte-identical to the synchronous implementation. RunInline() executes the same
-        // body on this thread and the join below publishes through the same code, so the two
+        // bodies on this thread, in the same order, and the join below publishes through the
-        // modes differ only in WHICH thread ran RunBody().
+        // same code, so the two modes differ only in WHICH thread ran them.
+        //
+        // Deliberately NOT expressed as SubmitAfter here: its continuation posts to the pool,
+        // and in this mode the pool is merely unused rather than stopped - the work would
+        // silently move off-thread in the one mode whose whole contract is that it does not.
         if (!MG_Util::Async::AsyncShaderCompileActive()) {
             task->RunInline();
-            EnsureLinkJoined();
+            spirvTask->RunInlineAfter(task);
+            EnsureSpirvJoined();
             return;
         }
+        // The chain edge FIRST, while phase A is still Pending, so registering it is a plain
+        // list append rather than an inline continuation on this thread. If SubmitAfter below
+        // then fails to post phase A it cancels it, and that cancel fires this edge, which
+        // cancels phase B - nothing is left stranded either way.
+        spirvTask->SubmitAfter(task);
         task->SubmitAfter(deps);
     }
 

MobileGL/MG_State/GLState/ProgramState/ProgramObject.h

@@ -18,6 +18,9 @@ namespace MobileGL::MG_State::GLState {
     // ProgramLinkTask.h includes THIS header (it outputs a LinkArtifacts), so including it
     // back would be circular. The destructor is therefore out of line.
     class ProgramLinkTask;
+    // Phase B of the same link: SPIR-V generation, spirv-opt and the global-UBO routing
+    // tables. Chained behind the ProgramLinkTask, forward-declared for the same reason.
+    class ProgramSpirvTask;
 
     class ProgramObject {
     public:
@@ -303,7 +306,25 @@ namespace MobileGL::MG_State::GLState {
         // Sentinel for a uniform location without global-UBO backing storage (should not
         // survive linking: GenerateBinary falls back to tail-allocated scratch storage).
         static constexpr Uint kInvalidUniformOffset = ~0u;
-        Uint GetUniformOffset(Uint location) const { return Artifacts().uniformOffsets[location]; }
+        // PHASE B (joins the SPIR-V job; see EnsureSpirvJoined).
+        //
+        // BOUNDS-CHECKED, and that is not defensive padding - it is the load-bearing half of
+        // the "linked but not drawable" contract. A phase B that settles CANCELLED rather than
+        // Complete (its body threw, the pool failed to enqueue it, or teardown cancelled it
+        // while phase A had already published) publishes nothing, so the shadow is a
+        // default-constructed SpirvArtifacts with an EMPTY uniformOffsets - while LINK_STATUS
+        // stays GL_TRUE, because GL gives no way to retract one, and IsValidUniformLocation()
+        // keeps answering true out of phase-A reflection. Every glUniform*/glGetUniform* call
+        // site reaches this getter BEFORE its own kInvalidUniformOffset / null-scratch guard,
+        // so an unchecked operator[] here would be a null dereference on the query surface
+        // this design promises stays answerable. Reporting kInvalidUniformOffset instead hands
+        // each of those sites exactly the value their existing guard already handles - the
+        // same value the routing pass itself uses for a uniform the optimizer deleted.
+        Uint GetUniformOffset(Uint location) const {
+            const SpirvArtifacts& spirv = Spirv();
+            return location < spirv.uniformOffsets.size() ? spirv.uniformOffsets[location]
+                                                          : kInvalidUniformOffset;
+        }
         Uint GetUniformSizesInBytes(Uint location) const { return MG_Util::GetGLTypeSize(GetUniformType(location)); }
 
         Int GetAttributeLocation(const String& name) {
@@ -381,9 +402,14 @@ namespace MobileGL::MG_State::GLState {
         const String& GetActiveAttribName(Uint index) const {
             return NormalizeBuiltinPipeInputName(Artifacts().program->getPipeInput(static_cast<Int>(index)).name);
         }
-        void* MapUBO() { return Artifacts().globalUboScratch.data(); }
+        // PHASE B, all three (see EnsureSpirvJoined): the shadow buffer's layout is decided
-        const void* GetUBOData() const { return Artifacts().globalUboScratch.data(); }
+        // by the OPTIMIZED SPIR-V, so it does not exist until the SPIR-V job has settled - and
-        Uint GetUBOSize() const { return static_cast<Uint>(Artifacts().globalUboScratch.size()); }
+        // never exists at all for a program whose SPIR-V job settled cancelled. These three
+        // degrade to nullptr/nullptr/0 in that case, which is exactly the "no backing storage"
+        // shape every caller already tests for (see GetUniformOffset's note).
+        void* MapUBO() { return Spirv().globalUboScratch.data(); }
+        const void* GetUBOData() const { return Spirv().globalUboScratch.data(); }
+        Uint GetUBOSize() const { return static_cast<Uint>(Spirv().globalUboScratch.size()); }
         // Content version of the CPU-side global-UBO shadow: writers bump it so backends
         // can skip re-uploading an unchanged UBO on every draw. ~0u is reserved as the
         // backends' "never uploaded" sentinel, so skip over it on wrap.
@@ -391,6 +417,25 @@ namespace MobileGL::MG_State::GLState {
         void MarkUBOContentDirty() const {
             if (++m_uboContentVersion == ~0u) m_uboContentVersion = 0;
         }
+        // ---- glUniform* inside the phase-A -> phase-B window ----
+        //
+        // True while the program is fully linked and fully queryable but its uniform shadow's
+        // LAYOUT (which the optimized SPIR-V decides) does not exist yet. A non-opaque
+        // glUniform* write in that window is RECORDED rather than joined, and replayed into
+        // the shadow at the phase-B publish - so a pack that sets its uniforms immediately
+        // after glLinkProgram never waits for SPIR-V.
+        //
+        // Nothing can observe the difference: the only route to those bytes is glGetUniform*
+        // (and a draw), and both of those go through the phase-B gate, which replays first.
+        // The OPAQUE branch of glUniform* is deliberately not buffered - a sampler unit is
+        // phase-A state (uniformSamplerOrImageUnitIndex), so glUniform1i(samplerLoc, unit)
+        // right after a link stays a zero-join operation, which is exactly what Iris does.
+        Bool IsSpirvPending() const { return m_pendingSpirv != nullptr; }
+        // Records one write. Returns false if it declined to buffer - the caller must then
+        // perform the write directly (which joins). Declining is the pressure valve for an
+        // application that writes megabytes of uniforms into a single pending window.
+        Bool BufferUniformWrite(Uint location, SizeT byteOffsetInUniform, const void* source, SizeT byteSize);
+
         Uint32 GetBackendStateVersion() const { return m_backendStateVersion; }
         // Bumped only by (re)linking — lets backends detect that every piece of
         // link-derived reflection (locations, block order, UBO layout) is stale.
@@ -463,6 +508,11 @@ namespace MobileGL::MG_State::GLState {
             CancelLink();
             BumpLinkObservableVersions();
             ResetLinkArtifacts(Artifacts());
+            // ResetLinkArtifacts is a LinkArtifacts-only operation (the link body calls it on
+            // its own block, where no phase-B output exists yet), so the phase-B half is
+            // cleared here. CancelLink() above already dropped the pending SPIR-V job, so
+            // this cannot be racing a publish.
+            m_spirv = {};
             Artifacts().infoLog = "No program binary format is supported.";
         }
         Bool GetValidateStatus() const { return m_validateStatus; }
@@ -571,8 +621,15 @@ namespace MobileGL::MG_State::GLState {
             return Artifacts().shaderStorageBlockBinding;
         }
 
-        Vector<Vector<unsigned>>& GetGeneratedSpirv() { return Artifacts().generatedSpirv; }
+        // PHASE B (see EnsureSpirvJoined). Empty for a program whose SPIR-V job was
-        const Vector<Vector<unsigned>>& GetGeneratedSpirv() const { return Artifacts().generatedSpirv; }
+        // cancelled; GetSpirvStatus() below is how a backend tells that apart from a program
+        // that never linked.
+        Vector<Vector<unsigned>>& GetGeneratedSpirv() { return Spirv().generatedSpirv; }
+        const Vector<Vector<unsigned>>& GetGeneratedSpirv() const { return Spirv().generatedSpirv; }
+        // Whether phase B produced usable SPIR-V. Joins, like the four getters above: a
+        // backend asks this exactly where it used to ask GetLinkStatus(), i.e. right before
+        // it builds or draws with the program.
+        Bool GetSpirvStatus() const { return Spirv().spirvStatus; }
 
         // The linked glslang reflection itself, for the ONE consumer that needs resource
         // lists no typed getter above exposes: the GL program-interface query layer
@@ -620,7 +677,6 @@ namespace MobileGL::MG_State::GLState {
         // without going through the gate.
         struct LinkArtifacts {
             SharedPtr<glslang::TProgram> program;
-            Vector<Vector<unsigned>> generatedSpirv;
 
             // Attributes (Vertex in)
             Vector<String> attribs;
@@ -664,11 +720,6 @@ namespace MobileGL::MG_State::GLState {
             // SetShaderStorageBlockBinding for why this one is by name and not by index.
             UnorderedMap<String, Int> shaderStorageBlockBinding;
 
-            // Need to be reflected after linking of SPIR-V binary
-            Vector<Uint> uniformOffsets;
-            Vector<Uint> uniformSizesInBytes;
-            Vector<Uint8> globalUboScratch;
-
             Uint activeUniformCount = 0;
             Uint maxUniformLocation = 0;
             Int uniformNameMaxLength = 0;
@@ -697,6 +748,35 @@ namespace MobileGL::MG_State::GLState {
             Uint32 xfbPackedStride = 0;
         };
 
+        // ---- everything phase B of a link produces, in one movable block ----
+        //
+        // The membership rule is the same mechanical one LinkArtifacts uses: this is exactly
+        // what ProgramSpirvTask writes, which is what makes moving it THE publish. It is
+        // deliberately NOT part of LinkArtifacts, and that separation is what routes the five
+        // readers of SPIR-V-derived data through their own join gate by compiler rather than
+        // by review - m_spirv is private and Spirv() is the only spelling that reaches it.
+        //
+        // Why these three and nothing else: `generatedSpirv` has no GL-thread reader at all
+        // (every consumer is a backend draw/prepare path), and `uniformOffsets` +
+        // `globalUboScratch` are the ONLY things glUniform*/glGetUniform* need that are
+        // derived from the OPTIMIZED SPIR-V rather than from glslang reflection - spirv-opt
+        // runs in place and can delete a uniform, or the whole global UBO, so the offsets
+        // cannot be lifted out of glslang's reflection instead.
+        struct SpirvArtifacts {
+            Vector<Vector<unsigned>> generatedSpirv;
+            // Byte offset of each uniform location inside globalUboScratch, or
+            // kInvalidUniformOffset. Sized maxUniformLocation + 1 by the routing pass.
+            Vector<Uint> uniformOffsets;
+            Vector<Uint8> globalUboScratch;
+            // False for a program whose SPIR-V was never produced (phase B cancelled at
+            // teardown or by a relink) or whose optimizer run failed. GL has no way to
+            // retract a LINK_STATUS it already reported true, so such a program stays
+            // "linked" and every reflection answer it has given stays correct - it is simply
+            // not drawable, which the backends already express through their link-status
+            // gates.
+            Bool spirvStatus = false;
+        };
+
         // ---- artifacts-only helpers, shared with ProgramLinkTask ----
         // Static and taking the block explicitly, because from stage 4 the link BODY needs
         // them while its artifacts still live on the job node, not on any ProgramObject. The
@@ -736,9 +816,20 @@ namespace MobileGL::MG_State::GLState {
         // Blocks until a pending link has published its artifacts. Public because a few call
         // sites have to join without reading anything - see the explicit-join list (J1-J8) in
         // the P1 design. GL thread only.
+        //
+        // PHASE A ONLY. After this returns, LINK_STATUS and the whole GL query surface are
+        // final and truthful, but the SPIR-V and the uniform shadow may still be in flight.
         void JoinLink() const { EnsureLinkJoined(); }
 
-        // Drops a link that is still in flight, without waiting for it. Called at the points
+        // Both phases. The draw path uses this, and must: the backends sample lifetimeId /
+        // backendStateVersion / the UBO content version OUTSIDE the gate, so a draw that
+        // joined only phase A would sample a version, join phase B later inside the same draw
+        // (through GetGeneratedSpirv), and memoize under a version the phase-B publish had
+        // already superseded - the exact lost-invalidation hazard J1 exists to prevent.
+        void JoinLinkAndSpirv() const { EnsureSpirvJoined(); }
+
+        // Drops BOTH phases of a link that is still in flight, without waiting for either.
+        // Called at the points
         // where the pending link's result stops being the answer to "what did this program
         // link to": a re-link supersedes it, glProgramBinary must force LINK_STATUS false,
         // and a destroyed program has no observers left.
@@ -757,7 +848,15 @@ namespace MobileGL::MG_State::GLState {
         // MUST NOT JOIN - this is what GL_COMPLETION_STATUS_KHR reads when the extension
         // surface lands. "No job at all" counts as complete: there is nothing outstanding to
         // wait for.
-        Bool IsLinkComplete() const { return m_pendingLink == nullptr || IsPendingLinkTerminal(); }
+        //
+        // BOTH phases, deliberately: an application that polls GL_COMPLETION_STATUS_KHR and
+        // then draws must not be told "done" while the SPIR-V is still being generated, or
+        // the draw it was cleared for is the thing that blocks.
+        Bool IsLinkComplete() const { return IsPhaseALinkComplete() && IsSpirvComplete(); }
+        // Phase A alone, for the callers that only care about the query surface (and for the
+        // tests that pin the two phases apart).
+        Bool IsPhaseALinkComplete() const { return m_pendingLink == nullptr || IsPendingLinkTerminal(); }
+        Bool IsSpirvComplete() const { return m_pendingSpirv == nullptr || IsPendingSpirvTerminal(); }
 
         void SetTransformFeedbackVaryings(Vector<String>&& names, GLenum bufferMode) {
             m_requestedXfbVaryings = Move(names);
@@ -824,6 +923,40 @@ namespace MobileGL::MG_State::GLState {
         // node's state goes through this out-of-line helper.
         Bool IsPendingLinkTerminal() const;
 
+        // ---- the second join gate: phase-B (SPIR-V) output only ----
+        // Phase A FIRST, always. Two reasons: the phase-B publish replays the uniform writes
+        // that were buffered during its window, and those need the phase-A reflection to
+        // validate against; and a caller that reaches a phase-B getter without having settled
+        // phase A would otherwise leave the link half-published.
+        //
+        // Same inline/out-of-line split as the phase-A gate, for the same reason: the five
+        // getters behind this one include the per-draw uniform upload path.
+        void EnsureSpirvJoined() const {
+            if (m_pendingLink) JoinPendingLink();
+            if (m_pendingSpirv) JoinPendingSpirv();
+        }
+        void JoinPendingSpirv() const;
+        Bool IsPendingSpirvTerminal() const;
+
+        // One buffered non-opaque glUniform* write. `dataOffset` indexes m_pendingUniformBytes,
+        // which is one append-only blob rather than a per-record allocation.
+        struct PendingUniformWrite {
+            Uint location = 0;
+            Uint byteOffsetInUniform = 0;
+            Uint byteSize = 0;
+            Uint dataOffset = 0;
+        };
+        // Replays the buffer into the freshly published shadow, in write order, and drains it.
+        // Each record re-does the bounds check and the bytes-equal dedupe the live write path
+        // performs, so "an identical write does not move the content version" survives the
+        // detour exactly - and a record that really does change bytes moves the version, which
+        // is what makes a backend re-upload the UBO it cached during the window.
+        void ReplayBufferedUniformWrites() const;
+        // Past this, BufferUniformWrite declines and the write joins instead. Sized so an
+        // ordinary pack load never reaches it (a pending window is one program's worth of
+        // uniforms) while a pathological writer cannot grow the heap without bound.
+        static constexpr SizeT kMaxBufferedUniformBytes = 4u << 20;
+
         LinkArtifacts& Artifacts() {
             EnsureLinkJoined();
             return m_artifacts;
@@ -832,6 +965,14 @@ namespace MobileGL::MG_State::GLState {
             EnsureLinkJoined();
             return m_artifacts;
         }
+        SpirvArtifacts& Spirv() {
+            EnsureSpirvJoined();
+            return m_spirv;
+        }
+        const SpirvArtifacts& Spirv() const {
+            EnsureSpirvJoined();
+            return m_spirv;
+        }
 
         // GL-thread-only companion to ResetLinkArtifacts (see its definition). Const because
         // the publish half of the join calls it; see the mutable counters below.
@@ -899,10 +1040,22 @@ namespace MobileGL::MG_State::GLState {
         // Mutable because publishing is a READ-side operation: a const getter has to be able
         // to settle an outstanding link before answering it.
         mutable LinkArtifacts m_artifacts;
+        // Phase-B output. Same mutability argument as m_artifacts, reached only through
+        // Spirv().
+        mutable SpirvArtifacts m_spirv;
 
         // The link job, from enqueue until the first observable read pulls its result. Null
         // means m_artifacts is already the answer - which is the state every reader outside
         // the pending window sees, and the whole reason the gate above is one branch.
         mutable SharedPtr<ProgramLinkTask> m_pendingLink;
+        // The SPIR-V job, chained behind m_pendingLink. Null means m_spirv is already the
+        // answer. A program can be in the window where m_pendingLink is already null (phase A
+        // published, the query surface is live) while this is still set.
+        mutable SharedPtr<ProgramSpirvTask> m_pendingSpirv;
+        // glUniform* writes taken while m_pendingSpirv was set, in call order, plus their
+        // bytes. Drained by the phase-B publish and cleared by every cancel site (a relink's
+        // uniforms are not the previous link's uniforms).
+        mutable Vector<PendingUniformWrite> m_pendingUniformWrites;
+        mutable Vector<Uint8> m_pendingUniformBytes;
     };
 } // namespace MobileGL::MG_State::GLState

MobileGL/MG_State/GLState/ProgramState/ProgramSpirvTask.cpp

@@ -0,0 +1,318 @@
+// MobileGL - MobileGL/MG_State/GLState/ProgramState/ProgramSpirvTask.cpp
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+
+#include "ProgramSpirvTask.h"
+
+#include <MG_State/GLState/ProgramState/ShaderCompileTask.h> // GlslangThreadAllocatorGuard
+#include <MG_Util/Async/ShaderCompilePool.h>
+#include <MG_Util/ShaderTranspiler/ShaderCompiler.h>
+#include <MG_Util/ShaderTranspiler/SpvcSession.h>
+#include <MG_Util/ShaderTranspiler/Types.h>
+
+#include <cstring>
+
+namespace MobileGL::MG_State::GLState {
+    void ProgramSpirvTask::DeferLog(String line) { diagnostics.logLines.push_back(Move(line)); }
+
+    void ProgramSpirvTask::SubmitAfter(const SharedPtr<ProgramLinkTask>& phaseA) {
+        MOBILEGL_ASSERT(phaseA != nullptr, "ProgramSpirvTask::SubmitAfter: the phase-A node is missing");
+        m_phaseA = phaseA;
+
+        auto self = std::static_pointer_cast<ProgramSpirvTask>(shared_from_this());
+        // ONE dependency, so no counter and no guard slot: the whole race
+        // ProgramLinkTask::SubmitAfter's +1 exists to close (a dependency settling while the
+        // remaining edges are still being registered) cannot arise with a single edge.
+        //
+        // Runs inline, right here, if phase A is already terminal.
+        phaseA->OnTerminal([self, phaseA] {
+            // "Dependency did not complete, publish nothing" - the same collapse
+            // ProgramLinkTask::CompiledArtifacts() performs for an abandoned compile. Note
+            // this reads the HANDOFF, never phaseA->artifacts: the GL thread may already be
+            // moving those out (see the class comment).
+            if (!phaseA->IsComplete() || !phaseA->spirvHandoff.ready) {
+                self->Cancel();
+                return;
+            }
+            // A cancel that landed before phase A settled (relink, glDeleteProgram, teardown).
+            // Posting would only make a worker pick up a node that immediately falls out of
+            // Run() again.
+            if (self->IsCancellationRequested()) {
+                self->Cancel();
+                return;
+            }
+            // Non-throwing by construction, and it has to be: this is a JobNode continuation,
+            // so on the pool side it runs inside an Asio handler. Post() contains its own
+            // allocation failures, and the catch below CANCELS rather than swallowing - a
+            // phase B that is never posted is a GL thread blocked forever in
+            // EnsureSpirvJoined(), which is far worse than a program reported as not drawable.
+            try {
+                MG_Util::Async::ShaderCompilePool::Get().Post(self);
+            } catch (...) {
+                self->Cancel();
+            }
+        });
+    }
+
+    void ProgramSpirvTask::RunInlineAfter(const SharedPtr<ProgramLinkTask>& phaseA) {
+        MOBILEGL_ASSERT(phaseA != nullptr, "ProgramSpirvTask::RunInlineAfter: the phase-A node is missing");
+        MOBILEGL_ASSERT(phaseA->IsTerminal(),
+                        "ProgramSpirvTask::RunInlineAfter: phase A has not settled; the inline path must run the "
+                        "two bodies in order on the same thread");
+        m_phaseA = phaseA;
+        RunInline();
+    }
+
+    // Pure CPU work only, on a pool worker (or on the GL thread in the inline mode).
+    // Everything this reads is either owned by this node or published by a terminal phase A;
+    // everything it writes is `artifacts` (and diagnostics). Same prohibitions as
+    // ProgramLinkTask::RunBody - no GL/EGL call, no pActiveBackendObject read, no
+    // pGLContext->RecordError().
+    void ProgramSpirvTask::RunBody() {
+        // glslang leaves this worker's TLS pool allocator pointing at the last arena it
+        // touched; reset it on the way out so an unrelated later job cannot allocate out of a
+        // pool that has since been freed. Declared FIRST so it is destroyed LAST - the phase-A
+        // release below drops the TShaders (and their pools) and must happen inside it.
+        const GlslangThreadAllocatorGuard glslangGuard;
+        using namespace MG_Util::ShaderTranspiler;
+
+        // Drop phase A - and with it the TShaders, the TProgram reference and phase A's whole
+        // input snapshot - the moment this body is done, rather than at some later join. For a
+        // pack load that is the difference between W glslang arenas alive and all of them.
+        struct PhaseAReleaser {
+            SharedPtr<ProgramLinkTask>& node;
+            ~PhaseAReleaser() { node.reset(); }
+        } const phaseAReleaser{m_phaseA};
+
+        if (!m_phaseA) return;
+        // Non-const: the TShaders are dropped below, the moment GlslangToSpv is finished with
+        // them. This is safe by ownership rather than by locking - phase A is terminal and
+        // therefore immutable to everyone else, the GL-thread join touches only `artifacts`
+        // and `diagnostics`, and this node is the sole reader of the handoff.
+        ProgramLinkTask::SpirvHandoff& handoff = m_phaseA->spirvHandoff;
+        const Uint externalIndex = m_phaseA->in.externalIndex;
+        if (!handoff.ready || !handoff.reflection.program) {
+            // Phase A did not reach its tail (it failed the link, or was cancelled mid-body).
+            // Publish nothing; spirvStatus stays false.
+            return;
+        }
+
+        MGLOG_D("ProgramObject %u: Starting SPIR-V generation", externalIndex);
+        GenerateSpirv(handoff, externalIndex);
+        // GlslangToSpv was the only consumer of the parsed ASTs; everything after this point
+        // works on the SPIR-V and on the TProgram's own self-contained reflection pool. Drop
+        // them here rather than at the end of the body, which is ~87% of this node's runtime
+        // earlier (spirv-opt plus routing).
+        //
+        // WHAT THIS ACTUALLY FREES, precisely - it is LESS than "the glslang arenas", and the
+        // difference matters for the peak-RSS story:
+        //   * CAS-LOSER shaders (the re-parse in ShaderCompileTask::ClaimParsedShader, i.e.
+        //     the 2nd..Nth link of a shared shader): freed here in full. The handoff is their
+        //     ONLY owner.
+        //   * CAS-WINNER shaders (the common case - one shader object linked into one
+        //     program, which is every program of an Iris pack load): NOT freed here. The
+        //     winner branch returns a COPY of ShaderCompileTask::artifacts.shader
+        //     (ShaderCompileTask.cpp:320) and the node never releases its own reference, while
+        //     phase A holds that node through in.shaders[i].compiled for its whole life - and
+        //     phase A lives until PhaseAReleaser fires at the end of this body. So the
+        //     refcount goes 2 -> 1 here and the arena dies where it would have died anyway.
+        //
+        // Making it free the winner's arena too means releasing whatever pins the TShader
+        // inside the compile node, and neither obvious route is safe as a drive-by: moving out
+        // of artifacts.shader at claim time races ShaderObject::GetCompiledShader() on the GL
+        // thread and breaks JobNode's "a terminal node is immutable" invariant, and dropping
+        // phase A's in.shaders[i].compiled reference only helps when nothing else holds the
+        // node (the adoption map is a WeakPtr index, so it would also change which nodes stay
+        // adoptable). Both belong in a change that can be reviewed against the consume-once
+        // and adoption semantics on their own terms.
+        handoff.shaders.clear();
+
+        MGLOG_D("ProgramObject %u: Building global-UBO routing tables", externalIndex);
+        BuildGlobalUboRouting(handoff, externalIndex);
+        MGLOG_D("ProgramObject %u: Binary generation finished (generatedSpirv size=%zu)", externalIndex,
+                artifacts.generatedSpirv.size());
+    }
+
+    void ProgramSpirvTask::GenerateSpirv(const ProgramLinkTask::SpirvHandoff& handoff, const Uint externalIndex) {
+        /* As we passed first stage compilation/linking,
+         * we'll assume all the operations here should
+         * pass. We may be able to employ some optimizations
+         * here without the burden of error reporting.
+         */
+        using namespace MG_Util::ShaderTranspiler;
+        MGLOG_D("ProgramObject %u: GenerateSpirv - start", externalIndex);
+
+        // The shaders were parsed once, in the link-compatible (relaxed Vulkan-rules)
+        // configuration, and the handoff's program linked those parses - so it IS the program
+        // the backends consume. Generate SPIR-V straight from its intermediates, which the
+        // handoff's TShaders keep alive.
+        ProgramBinaryAttrib binaryAttrib{
+            .shaderTypes = handoff.shaderTypes,
+            .program = *handoff.reflection.program,
+        };
+        MGLOG_D("ProgramObject %u: GenerateSpirv - requesting SPIR-V binary from program", externalIndex);
+        auto binaryResult = ShaderCompiler::GetSpirvBinaryFromProgram(binaryAttrib);
+        if (!binaryResult) {
+            DeferLog(std::format("ProgramObject {}: GenerateSpirv - GetSpirvBinaryFromProgram failed", externalIndex));
+            MOBILEGL_ASSERT(binaryResult, "GetSpirvBinaryFromProgram failed");
+            return; // spirvStatus stays false: linked, but not drawable.
+        }
+        artifacts.generatedSpirv = Move(binaryResult.value());
+        MGLOG_D("ProgramObject %u: GenerateSpirv - generated %zu SPIR-V modules", externalIndex,
+                artifacts.generatedSpirv.size());
+
+        // Linked SPIR-V generated, sanitize and optimize it
+        Bool allOptimized = true;
+        {
+            for (auto& spv : artifacts.generatedSpirv) {
+                auto success = ShaderCompiler::SanitizeAndOptimizeBinary(spv, spv);
+                if (!success) {
+                    // The one genuine phase-B failure mode: one of the seven optimizer passes
+                    // reported failure, so `spv` is whatever the run left behind. A fordebug
+                    // build trips the assert below; a release build used to hand that binary
+                    // to the backend regardless. It no longer does - the program keeps its
+                    // (truthful) LINK_STATUS and its whole query surface, and the routing
+                    // tables below still give every settable uniform storage so glUniform*
+                    // and glGetUniform* keep working, but spirvStatus stays false and the
+                    // backends refuse to build or draw with it.
+                    allOptimized = false;
+                    DeferLog(std::format("ProgramObject {}: SanitizeAndOptimizeBinary failed; the program is linked "
+                                         "and queryable but not drawable",
+                                         externalIndex));
+                }
+                MOBILEGL_ASSERT(success, "SanitizeBinary failed");
+            }
+        }
+        artifacts.spirvStatus = allOptimized;
+    }
+
+    void ProgramSpirvTask::BuildGlobalUboRouting(const ProgramLinkTask::SpirvHandoff& handoff,
+                                                 const Uint externalIndex) {
+        using namespace MG_Util::ShaderTranspiler;
+        // The phase-A reflection slice this pass keys off. Carried in the handoff rather than
+        // read off the phase-A node's artifacts, which the join has very likely already moved.
+        const ProgramObject::LinkArtifacts& reflection = handoff.reflection;
+
+        artifacts.uniformOffsets.clear();
+        artifacts.globalUboScratch.clear();
+        // kInvalidUniformOffset marks locations that end up without global-UBO backing
+        // (e.g. the optimizer eliminated every use of the uniform); the fallback pass
+        // below gives those locations tail storage so glUniform* always has a target.
+        artifacts.uniformOffsets.resize(reflection.maxUniformLocation + 1, ProgramObject::kInvalidUniformOffset);
+        for (SizeT i = 0; i < artifacts.generatedSpirv.size(); i++) {
+            auto& spv = artifacts.generatedSpirv[i];
+
+            auto shaderType = i < handoff.shaderTypes.size() ? handoff.shaderTypes[i] : GLenum{0};
+            MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - parsing SPIR-V meta data for module %zu "
+                    "(shaderType=%u, wordCount=%zu)",
+                    externalIndex, i, shaderType, spv.size());
+            SpvcSession session(spv, SessionUsageBit::Reflection);
+            auto result = session.ParseMetaData();
+            if (result < 0) {
+                MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - SpvcSession::ParseMetaData failed for module %zu, "
+                        "err = %d%s",
+                        externalIndex, i, result,
+                        (result == SPVC_ERROR_INVALID_SPIRV ? ". Probably no global UBO?" : ""));
+                continue;
+            } else {
+                auto& meta = session.GetMetadata();
+                auto size = meta.globalUboSize;
+                MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - SPIR-V meta: uboSize=%zu plainUniformCount=%zu "
+                        "plainUniformOffsets=%zu",
+                        externalIndex, meta.globalUboSize, meta.plainUniformMemberSizesInBytes.size(),
+                        meta.plainUniformOffsetsInUBO.size());
+                if (size == 0) {
+                    continue;
+                }
+                if (artifacts.globalUboScratch.size() < size) {
+                    artifacts.globalUboScratch.resize(size);
+                }
+                for (const auto& [name, offset] : meta.plainUniformOffsetsInUBO) {
+                    // SPIRV-Reflect leaf names never carry a "[0]" suffix; frontend
+                    // reflection keys arrays as "arr[0]" (GL naming), so retry with the
+                    // suffix before declaring the uniform unbacked.
+                    auto locationIt = reflection.uniformLocations.find(name);
+                    if (locationIt == reflection.uniformLocations.end()) {
+                        locationIt = reflection.uniformLocations.find(name + "[0]");
+                    }
+                    if (locationIt == reflection.uniformLocations.end()) {
+                        MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - uniform '%s' offset=%u but not found in "
+                                "uniformLocations",
+                                externalIndex, name.c_str(), offset);
+                        continue;
+                    }
+                    const Uint baseLocation = locationIt->second;
+                    if (!ProgramObject::IsValidUniformLocation(reflection, static_cast<Int>(baseLocation))) {
+                        continue;
+                    }
+
+                    const Int uniformIndex = reflection.uniformIndexInTProgram[baseLocation];
+                    const GLint arraySize = ProgramObject::GetUniformArraySizeByTIndex(reflection, uniformIndex);
+                    Uint arrayStride = 0;
+                    const auto strideIt = meta.plainUniformArrayStridesInUBO.find(name);
+                    if (strideIt != meta.plainUniformArrayStridesInUBO.end()) {
+                        arrayStride = strideIt->second;
+                    }
+
+                    // Array uniforms span one location per element (see DoReflection);
+                    // give each element its real byte offset inside the UBO.
+                    const GLint elementCount = (arraySize > 1 && arrayStride == 0) ? 1 : std::max(arraySize, 1);
+                    for (GLint element = 0; element < elementCount; ++element) {
+                        const Uint location = baseLocation + static_cast<Uint>(element);
+                        if (location > reflection.maxUniformLocation ||
+                            reflection.uniformIndexInTProgram[location] != uniformIndex) {
+                            break;
+                        }
+                        artifacts.uniformOffsets[location] = offset + static_cast<Uint>(element) * arrayStride;
+                    }
+                    MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - uniform '%s' offset=%u stride=%u assigned "
+                            "to locations %u..%u",
+                            externalIndex, name.c_str(), offset, arrayStride, baseLocation,
+                            baseLocation + static_cast<Uint>(elementCount) - 1);
+                }
+                MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - finished parsing module %zu metadata",
+                        externalIndex, i);
+            }
+        }
+
+        // Fallback pass: a linked program's active non-opaque uniforms must accept
+        // glUniform*/glGetUniform* even when the optimized SPIR-V no longer contains
+        // them (AggressiveDCE can remove a dead loop together with the only loads of a
+        // uniform -- or the entire global UBO, leaving the scratch unallocated). Hand
+        // such locations CPU-side storage at the (16-byte aligned) tail of the shadow
+        // buffer; backends bind at least the SPIR-V-declared UBO range, and the GPU
+        // never reads these bytes, so this only keeps the GL-visible state coherent.
+        for (Uint location = 0; location <= reflection.maxUniformLocation; ++location) {
+            if (artifacts.uniformOffsets[location] != ProgramObject::kInvalidUniformOffset) continue;
+            if (!ProgramObject::IsValidUniformLocation(reflection, static_cast<Int>(location))) continue;
+            const auto& uniform = reflection.program->getUniform(reflection.uniformIndexInTProgram[location]);
+            const glslang::TType* type = uniform.getType();
+            if (type != nullptr && type->isOpaque()) continue;
+            if (uniform.index >= 0 && uniform.index < reflection.program->getNumUniformBlocks() &&
+                std::strstr(reflection.program->getUniformBlock(uniform.index).name.c_str(),
+                            MG_Util::ShaderTranspiler::GLOBAL_UBO_NAME) == nullptr) {
+                // Member of a named uniform block: not settable through glUniform*, so it
+                // needs no global-UBO shadow storage.
+                continue;
+            }
+
+            // std140-style slot: the matrix upload paths write column vectors at
+            // 16-byte strides, so a matrix slot must cover cols * 16 bytes.
+            SizeT slotSize = MG_Util::GetGLTypeSize(uniform.glDefineType);
+            if (type != nullptr && type->isMatrix()) {
+                slotSize = static_cast<SizeT>(type->getMatrixCols()) * 16u;
+            }
+            slotSize = (slotSize + 15u) & ~static_cast<SizeT>(15u);
+            const SizeT slotOffset = (artifacts.globalUboScratch.size() + 15u) & ~static_cast<SizeT>(15u);
+            artifacts.globalUboScratch.resize(slotOffset + slotSize, 0);
+            artifacts.uniformOffsets[location] = static_cast<Uint>(slotOffset);
+            MGLOG_D("ProgramObject %u: BuildGlobalUboRouting - uniform '%s' location %u has no UBO backing in the "
+                    "generated SPIR-V (optimized out?); allocated %zu fallback bytes at scratch offset %zu",
+                    externalIndex, uniform.name.c_str(), location, slotSize, slotOffset);
+        }
+    }
+} // namespace MobileGL::MG_State::GLState

MobileGL/MG_State/GLState/ProgramState/ProgramSpirvTask.h

@@ -0,0 +1,77 @@
+// MobileGL - MobileGL/MG_State/GLState/ProgramState/ProgramSpirvTask.h
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+
+#pragma once
+#include <Includes.h>
+#include <MG_State/GLState/ProgramState/ProgramLinkTask.h>
+#include <MG_Util/Async/JobNode.h>
+
+namespace MobileGL::MG_State::GLState {
+    // PHASE B of one glLinkProgram: GlslangToSpv, spirv-opt, and the SPIRV-Cross pass that
+    // builds the glUniform*-to-scratch routing tables. Chained behind exactly one
+    // ProgramLinkTask and joined by exactly five ProgramObject getters (GetGeneratedSpirv,
+    // GetUniformOffset, MapUBO, GetUBOData, GetUBOSize), so ~120 other getters and the whole
+    // GL query surface stay on the phase-A gate and answer without waiting for any of this.
+    //
+    // ---- what this node may read, and what it may not ----
+    // It holds the phase-A node by SharedPtr and reads `phaseA->spirvHandoff` plus
+    // `phaseA->in`. It must NEVER read `phaseA->artifacts` or `phaseA->diagnostics`: the GL
+    // thread MOVES the artifacts out of the node at the phase-A join and DRAINS the
+    // diagnostics there, and both of those can happen while this body runs. The handoff exists
+    // precisely so this node has a copy of everything it needs that the join does not touch.
+    // (The general JobNode rule - a terminal node is immutable, so its outputs need no further
+    // synchronization - covers everything except the two members the join consumes.)
+    //
+    // ---- lifetime ----
+    // The handoff owns the Vector<SharedPtr<glslang::TShader>>, and that is mandatory rather
+    // than tidy: glslang::TProgram stores raw TShader* and, for the one-shader-per-stage case,
+    // BORROWS each stage's TIntermediate from its TShader. GlslangToSpv reads exactly those
+    // intermediates. Before the split the shaders died when ProgramLinkTask::RunBody returned,
+    // which was safe only because nothing called getIntermediate() afterwards.
+    //
+    // ---- failure ----
+    // A cancel (relink, teardown, program destruction) or an optimizer failure publishes
+    // spirvStatus = false rather than a half-built program. GL cannot retract a LINK_STATUS it
+    // already reported true, so such a program stays linked and fully queryable; it is just
+    // not drawable, which the backends express through their existing link-status gates.
+    class ProgramSpirvTask final : public MG_Util::Async::JobNode {
+    public:
+        // ---- output: valid iff IsComplete(), immutable afterwards ----
+        // Moved (never copied) into the ProgramObject by EnsureSpirvJoined().
+        ProgramObject::SpirvArtifacts artifacts;
+
+        // Posts this job when `phaseA` goes terminal - and not one moment earlier, so the body
+        // never waits on anything (invariant I4: no job body may block on another job). A
+        // single dependency needs no counter, just the one continuation; it runs inline right
+        // here if `phaseA` is already terminal, which is the same case
+        // ProgramLinkTask::SubmitAfter already reasons about.
+        //
+        // GL thread only, and only after the caller has stored a SharedPtr to this node: the
+        // continuation takes shared_from_this().
+        void SubmitAfter(const SharedPtr<ProgramLinkTask>& phaseA);
+
+        // The async-off / glMaxShaderCompilerThreadsKHR(0) path: run the body on the calling
+        // thread, right now, against an ALREADY-TERMINAL phase A. Deliberately not routed
+        // through SubmitAfter, whose continuation would Post() to a pool that is merely
+        // unused rather than stopped - that would move the work off-thread in the one mode
+        // whose contract is "byte-identical to the synchronous implementation".
+        void RunInlineAfter(const SharedPtr<ProgramLinkTask>& phaseA);
+
+    private:
+        void RunBody() override;
+
+        void GenerateSpirv(const ProgramLinkTask::SpirvHandoff& handoff, Uint externalIndex);
+        void BuildGlobalUboRouting(const ProgramLinkTask::SpirvHandoff& handoff, Uint externalIndex);
+
+        // Worker-side MGLOG replacement, replayed by the join on the GL thread. Same reason as
+        // ProgramLinkTask::DeferLog.
+        void DeferLog(String line);
+
+        SharedPtr<ProgramLinkTask> m_phaseA;
+    };
+} // namespace MobileGL::MG_State::GLState

MobileGL/MG_State/GLState/ProgramState/ProgramState.cpp

@@ -111,9 +111,13 @@ namespace MobileGL::MG_State::GLState {
         // that can grow, and a reallocation underneath this loop would be a use-after-free
         // that only shows up on the one GL call that walks the whole table. The copy costs a
         // refcount bump on a path a mode switch takes at most once.
+        // BOTH phases per program. This is the glMaxShaderCompilerThreadsKHR(0) path, whose
+        // contract is that nothing is outstanding when it returns - a program left with its
+        // SPIR-V job in flight would make the very next GL_COMPLETION_STATUS_KHR read GL_FALSE
+        // in a mode the extension says cannot have anything pending.
         for (SizeT i = 0; i < m_programObjects.size(); ++i) {
             const SharedPtr<ProgramObject> program = m_programObjects[i];
-            if (program) program->JoinLink();
+            if (program) program->JoinLinkAndSpirv();
         }
         for (SizeT i = 0; i < m_shaderObjects.size(); ++i) {
             const SharedPtr<ShaderObject> shader = m_shaderObjects[i];
@@ -122,7 +126,7 @@ namespace MobileGL::MG_State::GLState {
         // The currently-used program is reachable through m_programObjects unless
         // glDeleteProgram already freed its slot while it stayed current. Nothing else holds
         // a GL-visible name for it, but a draw would still join it, so settle it here too.
-        if (m_currentProgram) m_currentProgram->JoinLink();
+        if (m_currentProgram) m_currentProgram->JoinLinkAndSpirv();
     }
 
     void ProgramState::MarkShaderObjectForDeletion(Uint shader) {

MobileGL/MG_State/GLState/ProgramState/ShaderObject.cpp

@@ -88,12 +88,19 @@ namespace MobileGL::MG_State::GLState {
         // another object, THIS object has not pulled its result yet. (An adopted node may
         // already be terminal - the join then only replays what is left of its diagnostics.)
         m_compileJoined = false;
+        // A new compile is a new story: whatever the optimistic getters promised about the
+        // previous node does not carry over.
+        m_optimisticAnswerLatched = false;
     }
 
     void ShaderObject::DropCompileNode() const {
         if (!m_compiled) return;
         m_compiled->ReleaseAdopter();
         m_compiled.reset();
+        // No node means IsCompileComplete() is trivially true and the truthful answers are
+        // "not compiled"; a stale latch would keep reporting a compile that no longer
+        // exists as GL_TRUE.
+        m_optimisticAnswerLatched = false;
     }
 
     void ShaderObject::InvalidateCompiledState() {

MobileGL/MG_State/GLState/ProgramState/ShaderObject.h

@@ -116,8 +116,10 @@ namespace MobileGL {
             Bool GetDeleteStatus() const { return m_deleteStatus; }
 
             // Blocks until a pending compile has published its artifacts. Public for the
-            // sites that must join without reading anything - ProgramObject::Link's
+            // sites that must join without reading anything - ProgramState::
-            // prologue, which needs every attached shader settled before it runs.
+            // JoinAllPendingWork, the glMaxShaderCompilerThreadsKHR(0) path that settles
+            // every outstanding job. glLinkProgram deliberately does NOT come through
+            // here: its prologue takes the nodes unjoined via CompiledNodeForLink().
             void JoinCompile() const { EnsureCompileJoined(); }
 
             // True while this object holds the outcome (success OR failure) of a Compile()
@@ -141,6 +143,23 @@ namespace MobileGL {
             // outstanding to wait for.
             Bool IsCompileComplete() const { return m_compiled == nullptr || m_compiled->IsTerminal(); }
 
+            // MOBILEGL_ASYNC_OPTIMISTIC_SHADER_STATUS's one-story-per-compile memory. The
+            // three optimistic getter sites in GL_Program ask THIS instead of a raw
+            // IsCompileComplete() peek, and the difference is the latch: without it, a job
+            // that settles between two adjacent queries hands the application a torn pair -
+            // an empty info log from the optimistic read, then the real GL_FALSE from the
+            // truthful one - and an application that aborts on that status never reaches
+            // the link join that quotes the real log. So the first optimistic answer
+            // latches: until the next AdoptCompileNode/DropCompileNode this object keeps
+            // answering optimistically even after the job settles, and a real failure
+            // surfaces exactly once, at the link. Returns whether the caller should answer
+            // optimistically; the caller has already checked the quirk is active.
+            Bool TakeOptimisticCompileAnswer() const {
+                if (!m_optimisticAnswerLatched && IsCompileComplete()) return false;
+                m_optimisticAnswerLatched = true;
+                return true;
+            }
+
         private:
             // ---- The one and only join gate for compile output (P1 invariant I5) ----
             // The fast path - no job, or a job whose result this object has already pulled -
@@ -231,6 +250,10 @@ namespace MobileGL {
             // Exactly-once latch for the pull above. Armed with every new job node, set by
             // the one join that consumes it.
             mutable Bool m_compileJoined = false;
+            // TakeOptimisticCompileAnswer's memory: this object has answered a compile
+            // query optimistically for the current node. Cleared wherever the node
+            // changes hands (AdoptCompileNode) or goes away (DropCompileNode).
+            mutable Bool m_optimisticAnswerLatched = false;
         };
     } // namespace MG_State::GLState
 } // namespace MobileGL

MobileGL/MG_Test/Program/AsyncLinkTest.cpp

@@ -117,11 +117,26 @@ void main() { fragColor = thisIdentifierWasNeverDeclared; }
     }
 
     // The non-joining view of the program, i.e. what GL_COMPLETION_STATUS_KHR will report.
+    // BOTH phases: a program whose SPIR-V job is still in flight is not finished, even though
+    // its whole GL query surface already answers.
     Bool LinkIsSettled(const GLuint program) {
         const auto& object = MG_State::pGLContext->GetProgramObject(program);
         return object == nullptr || object->IsLinkComplete();
     }
 
+    // Phase A alone: the half that decides LINK_STATUS, the info log, and every reflection
+    // query. This is what a read of LINK_STATUS is required to settle.
+    Bool PhaseALinkIsSettled(const GLuint program) {
+        const auto& object = MG_State::pGLContext->GetProgramObject(program);
+        return object == nullptr || object->IsPhaseALinkComplete();
+    }
+
+    // Phase B alone: SPIR-V + the uniform shadow's layout.
+    Bool SpirvIsSettled(const GLuint program) {
+        const auto& object = MG_State::pGLContext->GetProgramObject(program);
+        return object == nullptr || object->IsSpirvComplete();
+    }
+
     // Enqueues `count` distinct heavy compiles without reading anything back, so the pool is
     // left with a real backlog for the caller to race against.
     Vector<GLuint> SaturatePool(const int count, Vector<String>& sourceStorage) {
@@ -516,11 +531,63 @@ TEST_F(AsyncLinkTest, LinkProgramReturnsBeforeTheWorkIsDone) {
 
     for (const GLuint program : programs) {
         EXPECT_EQ(QueryLinkStatus(program), GL_TRUE) << QueryProgramInfoLog(program);
-        EXPECT_TRUE(LinkIsSettled(program)) << "reading LINK_STATUS must have joined";
+        // PHASE A only. Reading LINK_STATUS settles the half that decides it, and no more -
+        // the SPIR-V job may well still be running, which is the entire point of the split.
+        EXPECT_TRUE(PhaseALinkIsSettled(program)) << "reading LINK_STATUS must have joined phase A";
     }
     EXPECT_EQ(GetError(), GL_NO_ERROR);
 }
 
+// The other half of the previous case, and the property the two-phase split exists for:
+// LINK_STATUS is answerable without the SPIR-V, so a run of LINK_STATUS reads over a
+// backlog must leave SPIR-V jobs outstanding rather than draining them one by one.
+TEST_F(AsyncLinkTest, ReadingLinkStatusDoesNotSettleTheSpirvJob) {
+    const AsyncModeScope async(true);
+    MG_Util::Async::ShaderCompilePool::Get().SetMaxConcurrency(1);
+    constexpr int kPrograms = 24;
+
+    const GLuint vs = MakeShader(GL_VERTEX_SHADER, kVs);
+    Vector<GLuint> programs;
+    Vector<String> sources;
+    for (int i = 0; i < kPrograms; ++i) {
+        sources.push_back(MakeBulkySource(7900 + i));
+        const char* text = sources.back().c_str();
+        const GLuint fs = CreateShader(GL_FRAGMENT_SHADER);
+        ShaderSource(fs, 1, &text, nullptr);
+        CompileShader(fs);
+        const GLuint program = CreateProgram();
+        AttachShader(program, vs);
+        AttachShader(program, fs);
+        LinkProgram(program);
+        programs.push_back(program);
+    }
+
+    int spirvOutstanding = 0;
+    for (int i = 0; i < kPrograms; ++i) {
+        const GLuint program = programs[static_cast<SizeT>(i)];
+        EXPECT_EQ(QueryLinkStatus(program), GL_TRUE) << QueryProgramInfoLog(program);
+        EXPECT_TRUE(PhaseALinkIsSettled(program)) << "reading LINK_STATUS must have joined phase A";
+        // Reflection has to answer here too, out of phase A and with no further join.
+        const String uniformName = "uSeed" + std::to_string(7900 + i);
+        EXPECT_GE(GetUniformLocation(program, uniformName.c_str()), 0) << uniformName;
+        if (!SpirvIsSettled(program)) ++spirvOutstanding;
+    }
+    EXPECT_GT(spirvOutstanding, 0) << "the whole GL query surface was answered and yet every SPIR-V job had "
+                                      "already been drained - the reads are joining phase B";
+
+    // And the SPIR-V gate really is a gate: touching it settles the job.
+    for (const GLuint program : programs) {
+        const auto& object = MG_State::pGLContext->GetProgramObject(program);
+        ASSERT_NE(object, nullptr);
+        EXPECT_GT(object->GetGeneratedSpirv().size(), 0u);
+        EXPECT_TRUE(SpirvIsSettled(program));
+        EXPECT_TRUE(LinkIsSettled(program));
+    }
+    EXPECT_EQ(GetError(), GL_NO_ERROR);
+    MG_Util::Async::ShaderCompilePool::Get().SetMaxConcurrency(
+        MG_Util::Async::ShaderCompilePool::Get().GetThreadCount());
+}
+
 // With the flag off, a link is finished by the time glLinkProgram returns. This is the guard
 // that keeps the default shippable.
 TEST_F(AsyncLinkTest, LinkIsFullySynchronousWithAsyncOff) {

MobileGL/MG_Test/Program/CMakeLists.txt

@@ -49,6 +49,22 @@ add_executable(
         AsyncLinkTest.cpp
 )
 
+add_executable(
+        OptimisticStatusTest
+        OptimisticStatusTest.cpp
+)
+
+target_include_directories(OptimisticStatusTest PRIVATE
+        ${MGL_ROOT}/include
+        ${MGL_ROOT}/MobileGL
+)
+
+target_link_libraries(
+        OptimisticStatusTest PRIVATE
+        GTest::gtest_main
+        ${LINK_LIBRARIES}
+)
+
 target_include_directories(AsyncLinkTest PRIVATE
         ${MGL_ROOT}/include
         ${MGL_ROOT}/MobileGL
@@ -60,6 +76,24 @@ target_link_libraries(
         ${LINK_LIBRARIES}
 )
 
+# Its own binary, like the other async suites: its cases pin the compile pool down to one
+# worker so a phase-B job really is still queued while the GL query surface is being read.
+add_executable(
+        AsyncSpirvPhaseTest
+        AsyncSpirvPhaseTest.cpp
+)
+
+target_include_directories(AsyncSpirvPhaseTest PRIVATE
+        ${MGL_ROOT}/include
+        ${MGL_ROOT}/MobileGL
+)
+
+target_link_libraries(
+        AsyncSpirvPhaseTest PRIVATE
+        GTest::gtest_main
+        ${LINK_LIBRARIES}
+)
+
 add_executable(
         ShaderCompileAdoptionTest
         ShaderCompileAdoptionTest.cpp
@@ -165,11 +199,17 @@ gtest_discover_tests(ProgramInterfaceTest DISCOVERY_TIMEOUT 30 PROPERTIES LABELS
 # compile pool so there is something in flight to race against.
 gtest_discover_tests(AsyncCompileTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
 gtest_discover_tests(AsyncLinkTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
+# Same reason: every case here links a batch against a one-worker pool so that phase B is
+# genuinely outstanding while phase A is being interrogated.
+gtest_discover_tests(AsyncSpirvPhaseTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
 # Same reason: the stage-6 cases keep a backlog in flight so a release really can race a
 # worker, and the 48-object stress links every one of them.
 gtest_discover_tests(ShaderCompileAdoptionTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
 # Same reason: the GL_COMPLETION_STATUS_KHR cases saturate a one-worker pool on purpose.
 gtest_discover_tests(ParallelShaderCompileTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
+# Same reason: the optimistic-window cases need a saturated one-worker pool to observe an
+# in-flight compile, and the two-phase replay links 48 programs across both flag states.
+gtest_discover_tests(OptimisticStatusTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
 gtest_discover_tests(AsyncTeardownTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)
 # Same reason again: several cases leave A links outstanding while B compiles and links.
 gtest_discover_tests(XfbFrontendOrderInvarianceTest DISCOVERY_TIMEOUT 60 PROPERTIES LABELS unit TIMEOUT 300)

MobileGL/MG_Test/Program/OptimisticStatusTest.cpp

@@ -0,0 +1,674 @@
+// MobileGL - MobileGL/MG_Test/Program/OptimisticStatusTest.cpp
+// Copyright (c) 2025-2026 MobileGL-Dev
+// Licensed under the GNU Lesser General Public License v3.0:
+//   https://www.gnu.org/licenses/gpl-3.0.txt
+//   https://www.gnu.org/licenses/lgpl-3.0.txt
+// SPDX-License-Identifier: LGPL-3.0-only
+// End of Source File Header
+
+// MOBILEGL_ASYNC_OPTIMISTIC_SHADER_STATUS: while a compile job is in flight, the two
+// per-shader queries that would join it - GL_COMPILE_STATUS and the info log - answer
+// optimistically instead, and the first such answer latches for that compile's lifetime
+// (ShaderObject::TakeOptimisticCompileAnswer). These cases pin the corners of that
+// contract: the default still joins, the optimistic window really answers without
+// joining, the latch keeps the three queries telling one story even after the job
+// settles, a real failure still fails the program link with the compile log quoted, and
+// the Iris-shaped two-phase batch produces reflection identical to the joining path.
+//
+// Determinism note: the cases that need "a compile that cannot have settled yet" do not
+// race the pool - they occupy its single concurrency slot with a gate-blocked job
+// (PoolBlocker), so the assertions are hard EXPECTs rather than skip-if-drained guesses.
+// A quirk that silently reverts to joining DEADLOCKS such a case into its 300s ctest
+// timeout instead of passing - ugly, but a failure, which is the point.
+//
+// Like AsyncCompileTest, every case drives the real GL entry points and flips the
+// MG_Config::Features fields itself rather than reading the environment, so one binary
+// asserts both flag states regardless of how the suite was launched.
+
+#include <gtest/gtest.h>
+
+#include <algorithm>
+#include <chrono>
+#include <condition_variable>
+#include <mutex>
+#include <string>
+#include <thread>
+#include <vector>
+
+#include "Config.h"
+#include "Includes.h"
+#include "Init.h"
+#include "MG_Impl/GLImpl/Getter/GL_Getter.h"
+#include "MG_Impl/GLImpl/Program/GL_Program.h"
+#include "MG_State/GLState/Core.h"
+#include "MG_Util/Async/JobNode.h"
+#include "MG_Util/Async/ShaderCompilePool.h"
+
+using namespace MobileGL;
+using namespace MobileGL::MG_Impl::GLImpl;
+
+namespace {
+    class AsyncModeScope {
+    public:
+        explicit AsyncModeScope(const Bool async) : m_saved(MG_Config::Features.AsyncShaderCompile) {
+            MG_Config::Features.AsyncShaderCompile =
+                async ? MG_Config::QuirkOverride::ForceOn : MG_Config::QuirkOverride::ForceOff;
+        }
+        ~AsyncModeScope() { MG_Config::Features.AsyncShaderCompile = m_saved; }
+        AsyncModeScope(const AsyncModeScope&) = delete;
+        AsyncModeScope& operator=(const AsyncModeScope&) = delete;
+
+    private:
+        const MG_Config::QuirkOverride m_saved;
+    };
+
+    class OptimisticStatusScope {
+    public:
+        explicit OptimisticStatusScope(const MG_Config::QuirkOverride mode)
+            : m_saved(MG_Config::Features.AsyncOptimisticShaderStatus) {
+            MG_Config::Features.AsyncOptimisticShaderStatus = mode;
+        }
+        ~OptimisticStatusScope() { MG_Config::Features.AsyncOptimisticShaderStatus = m_saved; }
+        OptimisticStatusScope(const OptimisticStatusScope&) = delete;
+        OptimisticStatusScope& operator=(const OptimisticStatusScope&) = delete;
+
+    private:
+        const MG_Config::QuirkOverride m_saved;
+    };
+
+    // glMaxShaderCompilerThreadsKHR writes PROCESS-wide state (the pool's concurrency budget
+    // and the suspension latch), so a case that touches it has to put both back or it
+    // poisons every case declared after it in this binary.
+    class CompilerThreadScope {
+    public:
+        CompilerThreadScope() = default;
+        ~CompilerThreadScope() {
+            MG_Util::Async::SetAsyncShaderCompileSuspended(false);
+            MG_Util::Async::ShaderCompilePool::Get().SetMaxConcurrency(
+                MG_Util::Async::ShaderCompilePool::Get().GetThreadCount());
+        }
+        CompilerThreadScope(const CompilerThreadScope&) = delete;
+        CompilerThreadScope& operator=(const CompilerThreadScope&) = delete;
+    };
+
+    // A job that occupies a pool slot until released, holding everything queued behind it
+    // in a provably-unsettled state. Same gate idea as JobNodeTest's TestJob+Gate; waiting
+    // on a test-owned gate inside a body does not violate the pool's no-job-waits-on-job
+    // rule - there is no other JOB involved.
+    class PoolBlocker final : public MG_Util::Async::JobNode {
+    public:
+        void Release() {
+            {
+                const std::lock_guard<std::mutex> lock(m_mutex);
+                m_open = true;
+            }
+            m_cv.notify_all();
+        }
+
+    protected:
+        void RunBody() override {
+            std::unique_lock<std::mutex> lock(m_mutex);
+            m_cv.wait(lock, [this] { return m_open; });
+        }
+
+    private:
+        std::mutex m_mutex;
+        std::condition_variable m_cv;
+        Bool m_open = false;
+    };
+
+    // Budget 1 + a blocked job in the only slot: from construction until Release(), no
+    // shader compile posted afterwards can run, let alone settle. The destructor releases
+    // and joins so no case can leak a wedged pool into the next one.
+    class BlockedPoolScope {
+    public:
+        BlockedPoolScope() : m_blocker(MakeShared<PoolBlocker>()) {
+            MaxShaderCompilerThreadsKHR(1);
+            MG_Util::Async::ShaderCompilePool::Get().Post(m_blocker);
+        }
+        ~BlockedPoolScope() { Release(); }
+
+        void Release() {
+            m_blocker->Release();
+            m_blocker->Wait();
+        }
+
+        BlockedPoolScope(const BlockedPoolScope&) = delete;
+        BlockedPoolScope& operator=(const BlockedPoolScope&) = delete;
+
+    private:
+        SharedPtr<PoolBlocker> m_blocker;
+    };
+
+    const char* kBrokenFs = R"(#version 460
+layout(location = 0) out vec4 fragColor;
+void main() { fragColor = thisIdentifierWasNeverDeclared; }
+)";
+
+    // Expensive enough that a compile is not instantaneous, and distinct per index so the
+    // source-hash memo and the stage-6 adoption map never turn a second instance into a
+    // no-op. Callers pass disjoint seed ranges for the same reason - two calls in one case
+    // must never regenerate the same text.
+    String MakeBulkySource(const int index) {
+        String source = "#version 460\nlayout(location = 0) out vec4 fragColor;\n";
+        source += "uniform float uSeed" + std::to_string(index) + ";\n";
+        source += "void main() {\n    float acc = uSeed" + std::to_string(index) + ";\n";
+        for (int i = 0; i < 320; ++i) {
+            source += "    acc = acc * 1.0001 + sin(acc + " + std::to_string(i) + ".0) * cos(acc);\n";
+        }
+        source += "    fragColor = vec4(acc, acc, acc, 1.0);\n}\n";
+        return source;
+    }
+
+    // The two stages of one Iris-shaped program. Distinct per index (so nothing is memoized
+    // across programs) but IDENTICAL between the quirk-off and quirk-on replays of the same
+    // index, which is what makes the reflection comparison meaningful.
+    String MakeIrisVs(const int index) {
+        String source = "#version 460\nlayout(location = 0) in vec3 aPos;\n";
+        source += "uniform mat4 uModel" + std::to_string(index) + ";\n";
+        source += "uniform vec4 uTint;\nout vec4 vColor;\n";
+        source += "void main() {\n    vColor = uTint;\n    gl_Position = uModel" + std::to_string(index) +
+                  " * vec4(aPos, 1.0);\n}\n";
+        return source;
+    }
+    String MakeIrisFs(const int index) {
+        String source = "#version 460\nlayout(location = 0) out vec4 fragColor;\nin vec4 vColor;\n";
+        source += "uniform float uSeed" + std::to_string(index) + ";\nuniform vec2 uOffset;\n";
+        source += "void main() {\n    float acc = uSeed" + std::to_string(index) + " + uOffset.x;\n";
+        for (int i = 0; i < 40; ++i) {
+            source += "    acc = acc * 1.0001 + sin(acc + " + std::to_string(i) + ".0);\n";
+        }
+        source += "    fragColor = vColor + vec4(acc, uOffset.y, 0.0, 1.0);\n}\n";
+        return source;
+    }
+
+    GLuint MakeShader(const GLenum type, const char* source) {
+        const GLuint shader = CreateShader(type);
+        ShaderSource(shader, 1, &source, nullptr);
+        CompileShader(shader);
+        return shader;
+    }
+
+    GLint QueryShaderCompletion(const GLuint shader) {
+        GLint status = -1;
+        GetShaderiv(shader, GL_COMPLETION_STATUS_KHR, &status);
+        return status;
+    }
+
+    GLint QueryCompileStatus(const GLuint shader) {
+        GLint status = GL_FALSE;
+        GetShaderiv(shader, GL_COMPILE_STATUS, &status);
+        return status;
+    }
+
+    GLint QueryInfoLogLength(const GLuint shader) {
+        GLint length = -1;
+        GetShaderiv(shader, GL_INFO_LOG_LENGTH, &length);
+        return length;
+    }
+
+    String QueryShaderInfoLog(const GLuint shader) {
+        std::vector<GLchar> buffer(65536);
+        GLsizei written = 0;
+        GetShaderInfoLog(shader, (GLsizei)buffer.size(), &written, buffer.data());
+        return String(buffer.data(), static_cast<size_t>(written));
+    }
+
+    GLint QueryLinkStatus(const GLuint program) {
+        GLint status = GL_FALSE;
+        GetProgramiv(program, GL_LINK_STATUS, &status);
+        return status;
+    }
+
+    GLint QueryProgramCompletion(const GLuint program) {
+        GLint status = -1;
+        GetProgramiv(program, GL_COMPLETION_STATUS_KHR, &status);
+        return status;
+    }
+
+    String QueryProgramInfoLog(const GLuint program) {
+        // Iris reads through an explicit 32768-byte buffer; mirror that cap so the
+        // log-ordering contract is asserted through the same window the application has.
+        std::vector<GLchar> buffer(32768);
+        GLsizei written = 0;
+        GetProgramInfoLog(program, (GLsizei)buffer.size(), &written, buffer.data());
+        return String(buffer.data(), static_cast<size_t>(written));
+    }
+
+    // Enqueues `count` distinct heavy compiles without reading anything back. Seed bases
+    // must be disjoint across calls within one case (see MakeBulkySource).
+    Vector<GLuint> SaturatePool(const int count, const int seedBase, Vector<String>& sourceStorage) {
+        Vector<GLuint> shaders;
+        shaders.reserve(static_cast<SizeT>(count));
+        for (int i = 0; i < count; ++i) {
+            sourceStorage.push_back(MakeBulkySource(seedBase + i));
+            const char* text = sourceStorage.back().c_str();
+            const GLuint shader = CreateShader(GL_FRAGMENT_SHADER);
+            ShaderSource(shader, 1, &text, nullptr);
+            CompileShader(shader);
+            shaders.push_back(shader);
+        }
+        return shaders;
+    }
+
+    // One program driven through Iris's exact phase-1 shape: create, source, compile, read
+    // the info log then the compile status (GlShader.createShader's order), attach, bind an
+    // attrib, link, detach, delete. NO program-level query of any kind.
+    GLuint RunIrisPhaseOne(const String& vsSource, const String& fsSource) {
+        const char* vsText = vsSource.c_str();
+        const char* fsText = fsSource.c_str();
+
+        const GLuint vs = CreateShader(GL_VERTEX_SHADER);
+        ShaderSource(vs, 1, &vsText, nullptr);
+        CompileShader(vs);
+        (void)QueryShaderInfoLog(vs);
+        (void)QueryCompileStatus(vs);
+
+        const GLuint fs = CreateShader(GL_FRAGMENT_SHADER);
+        ShaderSource(fs, 1, &fsText, nullptr);
+        CompileShader(fs);
+        (void)QueryShaderInfoLog(fs);
+        (void)QueryCompileStatus(fs);
+
+        const GLuint program = CreateProgram();
+        AttachShader(program, vs);
+        AttachShader(program, fs);
+        BindAttribLocation(program, 0, "aPos");
+        LinkProgram(program);
+        DetachShader(program, vs);
+        DetachShader(program, fs);
+        DeleteShader(vs);
+        DeleteShader(fs);
+        return program;
+    }
+
+    // Phase 2, also in Iris's order: LINK_STATUS first, then the by-name location lookups,
+    // then the GL_ACTIVE_UNIFORMS enumeration ProgramUniforms$Builder.buildUniforms does.
+    struct ProgramReflection {
+        GLint linkStatus = GL_FALSE;
+        Vector<std::pair<String, GLint>> locations;                       // queried name -> location
+        Vector<std::tuple<String, GLenum, GLint, GLint>> activeUniforms;  // name, type, size, location
+    };
+
+    ProgramReflection RunIrisPhaseTwo(const GLuint program, const Vector<String>& names) {
+        ProgramReflection out;
+        out.linkStatus = QueryLinkStatus(program);
+
+        for (const String& name : names) {
+            out.locations.emplace_back(name, GetUniformLocation(program, name.c_str()));
+        }
+
+        GLint activeCount = 0;
+        GetProgramiv(program, GL_ACTIVE_UNIFORMS, &activeCount);
+        for (GLint i = 0; i < activeCount; ++i) {
+            GLchar name[128] = {};
+            GLsizei written = 0;
+            GLint size = 0;
+            GLenum type = 0;
+            GetActiveUniform(program, (GLuint)i, (GLsizei)sizeof(name), &written, &size, &type, name);
+            const String nameStr(name, static_cast<size_t>(written));
+            out.activeUniforms.emplace_back(nameStr, type, size, GetUniformLocation(program, name));
+        }
+        // The enumeration order is an implementation detail; the SET is the contract.
+        std::sort(out.activeUniforms.begin(), out.activeUniforms.end());
+        return out;
+    }
+
+    class OptimisticStatusTest : public ::testing::Test {
+    protected:
+        void SetUp() override { MobileGL::Initialize(); }
+    };
+} // namespace
+
+// ---------------------------------------------------------------------------------------
+// The default still joins
+// ---------------------------------------------------------------------------------------
+
+// With the quirk unset (Auto = the shipped default), GL_COMPILE_STATUS on a pending compile
+// must join it: after the query, the node is terminal. This is the case that guards the
+// default against ever silently flipping. No blocker here - a blocked pool would turn the
+// (correct) joining behaviour into a deadlock; a plain backlog only makes the pre-join
+// state likely, and the assertion is valid either way.
+TEST_F(OptimisticStatusTest, OffByDefaultTheStatusStillJoins) {
+    const AsyncModeScope async(true);
+    const OptimisticStatusScope quirk(MG_Config::QuirkOverride::Auto);
+    const CompilerThreadScope threads;
+    MaxShaderCompilerThreadsKHR(1);
+
+    Vector<String> backlog;
+    const Vector<GLuint> saturation = SaturatePool(8, 70000, backlog);
+    const Vector<GLuint> probes = SaturatePool(1, 71000, backlog);
+    const GLuint probe = probes[0];
+
+    EXPECT_EQ(QueryCompileStatus(probe), GL_TRUE);
+    EXPECT_EQ(QueryShaderCompletion(probe), GL_TRUE)
+        << "GL_COMPILE_STATUS with the quirk off must have joined the job";
+
+    for (const GLuint shader : saturation) DeleteShader(shader);
+    DeleteShader(probe);
+    EXPECT_EQ(GetError(), GL_NO_ERROR);
+}
+
+// ---------------------------------------------------------------------------------------
+// The optimistic window, deterministically
+// ---------------------------------------------------------------------------------------
+
+// A compile that provably cannot have settled (the pool's only slot is gate-blocked)
+// answers GL_TRUE / length 0 / empty log, and GL_COMPLETION_STATUS_KHR still reads
+// GL_FALSE after all three - i.e. none of them joined. Hard EXPECTs, no skip: if the
+// quirk silently reverts to joining, the status read deadlocks against the blocked pool
+// and the case fails by timeout.
+TEST_F(OptimisticStatusTest, PendingCompileReportsTrueAndEmptyLogWithoutJoining) {
+    const AsyncModeScope async(true);
+    const OptimisticStatusScope quirk(MG_Config::QuirkOverride::ForceOn);
+    const CompilerThreadScope threads;
+    const BlockedPoolScope blocked;
+
+    Vector<String> storage;
+    const Vector<GLuint> probes = SaturatePool(1, 72000, storage);
+    const GLuint probe = probes[0];
+
+    EXPECT_EQ(QueryCompileStatus(probe), GL_TRUE) << "an in-flight compile must answer GL_TRUE";
+    EXPECT_EQ(QueryInfoLogLength(probe), 0) << "an in-flight compile must answer an empty log length";
+    EXPECT_TRUE(QueryShaderInfoLog(probe).empty()) << "an in-flight compile must answer an empty log";
+    EXPECT_EQ(QueryShaderCompletion(probe), GL_FALSE)
+        << "the three reads above must not have joined the blocked job";
+
+    DeleteShader(probe);
+    EXPECT_EQ(GetError(), GL_NO_ERROR);
+}
+
+// ---------------------------------------------------------------------------------------
+// The latch: one story per compile
+// ---------------------------------------------------------------------------------------
+
+// The torn-pair regression case. A broken shader's log and status are read while the job
+// is provably in flight (optimistic empty/GL_TRUE), the job then settles, and the app
+// re-reads: the latch must keep the answers optimistic - GL_TRUE, empty log - rather than
+// flip to the real GL_FALSE next to the already-consumed empty log. The real failure then
+// surfaces at the link, with the compile error inside the application's 32768-byte read
+// window (the compile log leads the quoted source in ConsumeShaders' format).
+TEST_F(OptimisticStatusTest, LatchKeepsOneStoryPerCompileAndTheLinkCarriesTheDiagnostic) {
+    const AsyncModeScope async(true);
+    const OptimisticStatusScope quirk(MG_Config::QuirkOverride::ForceOn);
+    const CompilerThreadScope threads;
+
+    const GLuint vs = CreateShader(GL_VERTEX_SHADER);
+    const char* vsText =
+        "#version 460\nlayout(location = 0) in vec3 aPos;\nvoid main() { gl_Position = vec4(aPos, 1.0); }\n";
+    ShaderSource(vs, 1, &vsText, nullptr);
+
+    GLuint fs = 0;
+    {
+        const BlockedPoolScope blocked;
+        CompileShader(vs);
+        fs = MakeShader(GL_FRAGMENT_SHADER, kBrokenFs);
+
+        // Iris's order, while nothing can settle: log (empty), then status (GL_TRUE).
+        EXPECT_TRUE(QueryShaderInfoLog(fs).empty());
+        EXPECT_EQ(QueryCompileStatus(fs), GL_TRUE);
+        EXPECT_EQ(QueryShaderCompletion(fs), GL_FALSE);
+    } // blocker released and joined; the broken compile can now settle
+
+    const auto deadline = std::chrono::steady_clock::now() + std::chrono::seconds(30);
+    while (QueryShaderCompletion(fs) == GL_FALSE) {
+        ASSERT_LT(std::chrono::steady_clock::now(), deadline) << "compile job never settled";
+        std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    }
+
+    // Settled - but this shader already told the optimistic story, so it keeps telling it.
+    EXPECT_EQ(QueryCompileStatus(fs), GL_TRUE)
+        << "the latch must keep a queried-while-pending compile optimistic after it settles";
+    EXPECT_EQ(QueryInfoLogLength(fs), 0);
+    EXPECT_TRUE(QueryShaderInfoLog(fs).empty());
+
+    // The truth arrives where the design routes it: at the link.
+    const GLuint program = CreateProgram();
+    AttachShader(program, vs);
+    AttachShader(program, fs);
+    LinkProgram(program);
+    EXPECT_EQ(QueryLinkStatus(program), GL_FALSE) << "a latched-over failure must still fail the link";
+    EXPECT_NE(QueryProgramInfoLog(program).find("thisIdentifierWasNeverDeclared"), String::npos)
+        << "the compile error must lead the program info log, inside a 32768-byte window";
+
+    DeleteProgram(program);
+    DeleteShader(vs);
+    DeleteShader(fs);
+    EXPECT_EQ(GetError(), GL_NO_ERROR);
+}
+
+// A shader whose FIRST query arrives after the job settled was never answered
+// optimistically, so it owes no continuity: the truth comes straight back. (The
+// completion poll does not engage the latch - it is the extension's own non-joining
+// query and always tells the truth.)
+TEST_F(OptimisticStatusTest, OnceTerminalAnUnqueriedShaderTellsTheTruth) {
+    const AsyncModeScope async(true);
+    const OptimisticStatusScope quirk(MG_Config::QuirkOverride::ForceOn);
+
+    const GLuint fs = MakeShader(GL_FRAGMENT_SHADER, kBrokenFs);
+
+    const auto deadline = std::chrono::steady_clock::now() + std::chrono::seconds(30);
+    while (QueryShaderCompletion(fs) == GL_FALSE) {
+        ASSERT_LT(std::chrono::steady_clock::now(), deadline) << "compile job never settled";
+        std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    }
+
+    EXPECT_EQ(QueryCompileStatus(fs), GL_FALSE) << "no optimistic answer was given, so no latch holds";
+    EXPECT_GT(QueryInfoLogLength(fs), 0);
+    EXPECT_NE(QueryShaderInfoLog(fs).find("thisIdentifierWasNeverDeclared"), String::npos);
+    DeleteShader(fs);
+    EXPECT_EQ(GetError(), GL_NO_ERROR);
+}
+
+// Recompiling resets the story: a latched optimistic answer must not survive a source
+// change (the latch clears when the node changes hands or goes away).
+TEST_F(OptimisticStatusTest, ANewCompileResetsTheLatch) {
+    const AsyncModeScope async(true);
+    const OptimisticStatusScope quirk(MG_Config::QuirkOverride::ForceOn);
+    const CompilerThreadScope threads;
+
+    GLuint fs = 0;
+    {
+        const BlockedPoolScope blocked;
+        fs = MakeShader(GL_FRAGMENT_SHADER, kBrokenFs);
+        EXPECT_EQ(QueryCompileStatus(fs), GL_TRUE); // latches
+    }
+
+    // New source, new compile, no query before it settles.
+    const char* goodFs = "#version 460\nlayout(location = 0) out vec4 fragColor;\n"
+                         "void main() { fragColor = vec4(1.0); }\n";
+    ShaderSource(fs, 1, &goodFs, nullptr);
+    CompileShader(fs);
+    const auto deadline = std::chrono::steady_clock::now() + std::chrono::seconds(30);
+    while (QueryShaderCompletion(fs) == GL_FALSE) {
+        ASSERT_LT(std::chrono::steady_clock::now(), deadline) << "recompile never settled";
+        std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    }
+    EXPECT_EQ(QueryCompileStatus(fs), GL_TRUE);
+    EXPECT_TRUE(QueryShaderInfoLog(fs).empty());
+    DeleteShader(fs);
+    EXPECT_EQ(GetError(), GL_NO_ERROR);
+}
+
+// ---------------------------------------------------------------------------------------
+// Failure still fails, at the link, inside the application's read window
+// ---------------------------------------------------------------------------------------
+
+// A broken fragment shader whose compile status was answered optimistically still fails
+// its program link, and the compile error is readable through a 32768-byte
+// glGetProgramInfoLog - the compile log LEADS the quoted source in ConsumeShaders'
+// format, so even this >32KB shader source cannot push it out of the window.
+TEST_F(OptimisticStatusTest, AFailingCompileStillFailsItsLink) {
+    const AsyncModeScope async(true);
+    const OptimisticStatusScope quirk(MG_Config::QuirkOverride::ForceOn);
+
+    // A >32KB broken fragment shader: the undeclared identifier sits at the top, then bulk.
+    String brokenSource = "#version 460\nlayout(location = 0) out vec4 fragColor;\n";
+    brokenSource += "void main() {\n    float acc = thisIdentifierWasNeverDeclared;\n";
+    for (int i = 0; i < 900; ++i) {
+        brokenSource += "    acc = acc * 1.0001 + sin(acc + " + std::to_string(i) + ".0) * cos(acc);\n";
+    }
+    brokenSource += "    fragColor = vec4(acc);\n}\n";
+    ASSERT_GT(brokenSource.size(), 32768u);
+
+    const GLuint vs = MakeShader(GL_VERTEX_SHADER,
+                                 "#version 460\nlayout(location = 0) in vec3 aPos;\n"
+                                 "void main() { gl_Position = vec4(aPos, 1.0); }\n");
+    const char* brokenText = brokenSource.c_str();
+    const GLuint fs = CreateShader(GL_FRAGMENT_SHADER);
+    ShaderSource(fs, 1, &brokenText, nullptr);
+    CompileShader(fs);
+    (void)QueryShaderInfoLog(fs);
+    (void)QueryCompileStatus(fs); // may latch optimistic GL_TRUE; must not matter
+
+    const GLuint program = CreateProgram();
+    AttachShader(program, vs);
+    AttachShader(program, fs);
+    LinkProgram(program);
+
+    EXPECT_EQ(QueryLinkStatus(program), GL_FALSE) << "a hidden compile failure must still fail the link";
+    const String log = QueryProgramInfoLog(program);
+    EXPECT_NE(log.find("thisIdentifierWasNeverDeclared"), String::npos)
+        << "the compile error must be readable through a 32768-byte program info log window";
+
+    DeleteProgram(program);
+    DeleteShader(vs);
+    DeleteShader(fs);
+    EXPECT_EQ(GetError(), GL_NO_ERROR);
+}
+
+// ---------------------------------------------------------------------------------------
+// The Iris two-phase replay
+// ---------------------------------------------------------------------------------------
+
+// THE LOAD-BEARING CASE. 24 programs through Iris's exact phase-1 shape (compile, read log
+// then status per shader, link, detach, delete - no program query), then phase 2 (link
+// status, by-name locations including an absent name, the active-uniform enumeration).
+// Every location and every active-uniform record must equal what the identical sequence
+// produces with the quirk off.
+//
+// Two determinism guards make this a real A/B rather than a tautology:
+//   * The quirk-on arm runs FIRST, against a cold preprocess cache, and the reference arm
+//     second - so it is the path under test that pays the full pipeline, not the control.
+//   * The quirk-on arm's phase 1 runs over a BLOCKED pool, and every program is then
+//     WITNESSED still-incomplete (GL_COMPLETION_STATUS_KHR == GL_FALSE) before the pool
+//     is released: proof that no phase-1 call joined, i.e. the quirk was really engaged.
+//     A quirk that silently reverts to joining deadlocks here and fails by timeout.
+TEST_F(OptimisticStatusTest, IrisTwoPhaseReplayProducesIdenticalReflection) {
+    constexpr int kPrograms = 24;
+
+    Vector<ProgramReflection> reference;
+    Vector<ProgramReflection> optimistic;
+
+    for (const Bool quirkOn : {true, false}) {
+        const AsyncModeScope async(true);
+        const OptimisticStatusScope quirk(quirkOn ? MG_Config::QuirkOverride::ForceOn
+                                                  : MG_Config::QuirkOverride::ForceOff);
+        const CompilerThreadScope threads;
+
+        Vector<String> vsSources, fsSources;
+        for (int i = 0; i < kPrograms; ++i) {
+            vsSources.push_back(MakeIrisVs(i));
+            fsSources.push_back(MakeIrisFs(i));
+        }
+
+        Vector<GLuint> programs;
+        if (quirkOn) {
+            const BlockedPoolScope blocked;
+            for (int i = 0; i < kPrograms; ++i) {
+                programs.push_back(RunIrisPhaseOne(vsSources[(SizeT)i], fsSources[(SizeT)i]));
+            }
+            // The witness: phase 1 finished with the pool blocked, so nothing can have
+            // settled and nothing can have been joined - every link must still be pending.
+            for (int i = 0; i < kPrograms; ++i) {
+                ASSERT_EQ(QueryProgramCompletion(programs[(SizeT)i]), GL_FALSE)
+                    << "program " << i << " settled under a blocked pool - a phase-1 call must have joined";
+            }
+        } else {
+            for (int i = 0; i < kPrograms; ++i) {
+                programs.push_back(RunIrisPhaseOne(vsSources[(SizeT)i], fsSources[(SizeT)i]));
+            }
+        }
+
+        Vector<ProgramReflection>& out = quirkOn ? optimistic : reference;
+        for (int i = 0; i < kPrograms; ++i) {
+            const Vector<String> names = {"uModel" + std::to_string(i), "uTint",
+                                          "uSeed" + std::to_string(i), "uOffset", "uDoesNotExist"};
+            out.push_back(RunIrisPhaseTwo(programs[(SizeT)i], names));
+        }
+        for (const GLuint program : programs) DeleteProgram(program);
+        ASSERT_EQ(GetError(), GL_NO_ERROR);
+    }
+
+    ASSERT_EQ(reference.size(), optimistic.size());
+    for (SizeT i = 0; i < reference.size(); ++i) {
+        EXPECT_EQ(reference[i].linkStatus, GL_TRUE) << "program " << i;
+        EXPECT_EQ(optimistic[i].linkStatus, GL_TRUE) << "program " << i;
+        EXPECT_EQ(reference[i].locations, optimistic[i].locations)
+            << "program " << i << ": by-name locations diverged under the quirk";
+        EXPECT_EQ(reference[i].activeUniforms, optimistic[i].activeUniforms)
+            << "program " << i << ": active-uniform enumeration diverged under the quirk";
+        // The absent name answers -1 in both worlds.
+        EXPECT_EQ(reference[i].locations.back().second, -1) << "program " << i;
+    }
+}
+
+// ---------------------------------------------------------------------------------------
+// The concurrency observable
+// ---------------------------------------------------------------------------------------
+
+// The crisp A/B that phase 1 stopped joining. Quirk-on arm: the phase-1 shape over a
+// blocked pool completes without joining anything - every shader is then provably still
+// in flight (hard EXPECT; an inert quirk deadlocks and fails by timeout). Quirk-off arm:
+// the same shape joins at every status read, so nothing is left in flight afterwards.
+TEST_F(OptimisticStatusTest, PhaseOneIssuesNoCompileJoin) {
+    const AsyncModeScope async(true);
+    const CompilerThreadScope threads;
+
+    // Quirk on: nothing settles, nothing joins.
+    {
+        const OptimisticStatusScope quirk(MG_Config::QuirkOverride::ForceOn);
+        const BlockedPoolScope blocked;
+        Vector<String> storage;
+        Vector<GLuint> shaders;
+        for (int i = 0; i < 12; ++i) {
+            storage.push_back(MakeBulkySource(90000 + i));
+            const char* text = storage.back().c_str();
+            const GLuint fs = CreateShader(GL_FRAGMENT_SHADER);
+            ShaderSource(fs, 1, &text, nullptr);
+            CompileShader(fs);
+            (void)QueryShaderInfoLog(fs);
+            (void)QueryCompileStatus(fs);
+            shaders.push_back(fs);
+        }
+        for (const GLuint shader : shaders) {
+            EXPECT_EQ(QueryShaderCompletion(shader), GL_FALSE)
+                << "a phase-1 read joined a compile the blocked pool could not have run";
+        }
+        for (const GLuint shader : shaders) DeleteShader(shader);
+    }
+
+    // Quirk off: every status read joins its shader.
+    {
+        const OptimisticStatusScope quirk(MG_Config::QuirkOverride::ForceOff);
+        MaxShaderCompilerThreadsKHR(1);
+        Vector<String> storage;
+        Vector<GLuint> shaders;
+        for (int i = 0; i < 12; ++i) {
+            storage.push_back(MakeBulkySource(80000 + i));
+            const char* text = storage.back().c_str();
+            const GLuint fs = CreateShader(GL_FRAGMENT_SHADER);
+            ShaderSource(fs, 1, &text, nullptr);
+            CompileShader(fs);
+            (void)QueryShaderInfoLog(fs);
+            (void)QueryCompileStatus(fs);
+            shaders.push_back(fs);
+        }
+        for (const GLuint shader : shaders) {
+            EXPECT_EQ(QueryShaderCompletion(shader), GL_TRUE)
+                << "with the quirk off every per-shader status read must have joined";
+        }
+        for (const GLuint shader : shaders) DeleteShader(shader);
+    }
+    EXPECT_EQ(GetError(), GL_NO_ERROR);
+}

MobileGL/MG_Test/Program/ParallelShaderCompileTest.cpp

@@ -239,7 +239,15 @@ TEST_F(ParallelShaderCompileTest, ProgramCompletionStatusReportsFalseWithoutJoin
 
     for (const GLuint program : programs) {
         EXPECT_EQ(QueryLinkStatus(program), GL_TRUE);
-        EXPECT_EQ(QueryProgramCompletion(program), GL_TRUE) << "GL_LINK_STATUS must have joined";
+        // GL_COMPLETION_STATUS_KHR spans BOTH phases of a link, so reading GL_LINK_STATUS -
+        // which is answered out of phase A - is no longer enough to turn it GL_TRUE. That is
+        // deliberate: an application that polls completion and then draws must not be told
+        // "done" while the SPIR-V is still being generated, or the draw it was cleared for is
+        // the thing that blocks. Settling both phases is what makes the query true.
+        const auto& object = MG_State::pGLContext->GetProgramObject(program);
+        ASSERT_NE(object, nullptr);
+        object->JoinLinkAndSpirv();
+        EXPECT_EQ(QueryProgramCompletion(program), GL_TRUE) << "a full join must have settled both phases";
     }
     EXPECT_EQ(GetError(), GL_NO_ERROR);
 }
@@ -333,6 +341,54 @@ TEST_F(ParallelShaderCompileTest, ZeroCompilerThreadsJoinsEverythingAndCompilesI
     EXPECT_EQ(GetError(), GL_NO_ERROR);
 }
 
+// The same obligation, but for LINKS that are already in flight when the zero count arrives -
+// and specifically for BOTH phases of one. A link is two chained jobs now (ProgramLinkTask,
+// then ProgramSpirvTask), and GL_COMPLETION_STATUS_KHR spans both, so
+// ProgramState::JoinAllPendingWork has to settle both or this query reads GL_FALSE in the one
+// mode the extension says cannot have anything pending. The case above creates its program
+// AFTER the zero count, so it links inline and cannot see this; here the programs are linked
+// against a saturated pool BEFORE it.
+TEST_F(ParallelShaderCompileTest, ZeroCompilerThreadsJoinsPendingLinksAndTheirSpirvJobs) {
+    const AsyncModeScope async(true);
+    const CompilerThreadScope threads;
+    MaxShaderCompilerThreadsKHR(1);
+
+    // A backlog first, so the links below cannot all drain before the zero count lands.
+    Vector<String> sources;
+    (void)EnqueueBacklog(24, 5000, sources);
+
+    Vector<GLuint> programs;
+    for (int i = 0; i < 8; ++i) {
+        sources.push_back(MakeBulkySource(5100 + i));
+        const char* text = sources.back().c_str();
+        const GLuint fs = CreateShader(GL_FRAGMENT_SHADER);
+        ShaderSource(fs, 1, &text, nullptr);
+        CompileShader(fs);
+        const GLuint vs = MakeShader(GL_VERTEX_SHADER, kVs);
+        CompileShader(vs); // this file's MakeShader only sources; it does not compile
+        const GLuint program = CreateProgram();
+        AttachShader(program, vs);
+        AttachShader(program, fs);
+        LinkProgram(program);
+        programs.push_back(program);
+    }
+
+    int outstanding = 0;
+    for (const GLuint program : programs) {
+        if (QueryProgramCompletion(program) == GL_FALSE) ++outstanding;
+    }
+
+    MaxShaderCompilerThreadsKHR(0);
+
+    for (const GLuint program : programs) {
+        EXPECT_EQ(QueryProgramCompletion(program), GL_TRUE)
+            << "glMaxShaderCompilerThreadsKHR(0) must leave neither link phase in flight";
+        EXPECT_EQ(QueryLinkStatus(program), GL_TRUE);
+    }
+    EXPECT_GT(outstanding, 0) << "every link had drained before the zero count; this case proved nothing";
+    EXPECT_EQ(GetError(), GL_NO_ERROR);
+}
+
 // ...and a later NONZERO count is what lifts it. Nothing else does: not a new context, not a
 // join, not eglInitialize. That is the documented contract, so it gets an assertion.
 TEST_F(ParallelShaderCompileTest, NonzeroCompilerThreadsRestoresAsynchronousCompilation) {

MobileGL/MG_Test/Program/ProgramUtilTest.cpp

@@ -9,8 +9,11 @@
 #include <gtest/gtest.h>
 
 #include <cstring>
+#include <map>
+#include <set>
 #include <string>
 #include <utility>
+#include <vector>
 
 #include "Includes.h"
 #include "Init.h"
@@ -2649,3 +2652,110 @@ TEST_F(ProgramUtilTest, ShaderPreprocessCacheHonorsByteBudget) {
     EXPECT_EQ(cache.GetEntryCount(), before);
     EXPECT_EQ(cache.Find(ShaderStage::Vertex, ShaderPreprocessCache::HashSource(oversized), oversized, kEnvA), nullptr);
 }
+
+// Every vertex input that reaches SPIR-V must carry a Location decoration - including the
+// declarations glslang's io-mapper considers INACTIVE.
+//
+// The shape is Iris's: seven attributes, only some of them bound through
+// glBindAttribLocation (ProgramAttrib::explicitVertexInLocations), and at least one neither
+// bound nor referenced. GL says only active inputs get generic attribute locations, so the
+// resolver deliberately does not RESERVE a slot for a dead one - but it must still RESOLVE a
+// location for it, because glslang emits an OpVariable for every declared global (the entry
+// point's interface comes from the linker objects) and SPIR-V requires every non-built-in
+// Input to be decorated (VUID-StandaloneSpirv-Location-04916).
+//
+// This test drives the FRONTEND rather than the GL entry points on purpose: it checks the RAW
+// GlslangToSpv output, before SanitizeAndOptimizeBinary. A GL-level test cannot see the defect
+// for an unreferenced attribute, because AggressiveDCE deletes the offending variable on its
+// way to the backend - and yet the real victim (Iris' mc_midTexCoord, Adreno 830,
+// programHash 0x4a7e9a37fb49caa1) survived DCE and killed the pipeline with VK_ERROR_UNKNOWN.
+TEST_F(ProgramUtilTest, PartiallyBoundVertexInputsAllReceiveALocation) {
+    using namespace MG_Util::ShaderTranspiler;
+
+    const String vertexSource = R"(#version 460 core
+in vec3 a_Position;
+in vec4 a_Color;
+in vec2 a_TexCoord;
+in vec2 mc_midTexCoord;
+in vec4 mc_Entity;
+in vec3 iris_Normal;
+in vec4 a_Unreferenced;
+out vec4 v_Color;
+void main() {
+    v_Color = a_Color + vec4(a_TexCoord, 0.0, 0.0) + vec4(mc_midTexCoord, 0.0, 0.0) + mc_Entity
+            + vec4(iris_Normal, 0.0);
+    gl_Position = vec4(a_Position, 1.0);
+}
+)";
+
+    ShaderAttrib shaderAttrib{.shaderType = GL_VERTEX_SHADER, .sourceStr = vertexSource};
+    auto shaderResult = ShaderCompiler::CompileShader(shaderAttrib);
+    ASSERT_TRUE(shaderResult) << shaderResult.error().log;
+
+    // PARTIALLY bound, and deliberately not a dense 0..N run - exactly what Iris does.
+    // mc_midTexCoord and a_Unreferenced are left unbound (FastSTL's map has no
+    // initializer-list constructor, hence the explicit inserts).
+    UnorderedMap<String, Uint> explicitVertexIns;
+    explicitVertexIns["a_Position"] = 0;
+    explicitVertexIns["a_Color"] = 1;
+    explicitVertexIns["a_TexCoord"] = 2;
+    explicitVertexIns["iris_Normal"] = 10;
+    explicitVertexIns["mc_Entity"] = 11;
+    ProgramAttrib programAttrib{.shaders = {shaderResult.value()},
+                                .explicitVertexInLocations = explicitVertexIns};
+    auto programResult = ShaderCompiler::LinkProgram(programAttrib);
+    ASSERT_TRUE(programResult) << programResult.error().log;
+
+    ProgramBinaryAttrib binaryAttrib{.shaderTypes = {GL_VERTEX_SHADER}, .program = *programResult.value()};
+    auto binaryResult = ShaderCompiler::GetSpirvBinaryFromProgram(binaryAttrib);
+    ASSERT_TRUE(binaryResult) << binaryResult.error().log;
+    ASSERT_EQ(binaryResult->size(), 1u);
+    const auto& vertexBinary = binaryResult->front();
+
+    // The authoritative check - this is the same validator whose VUID the driver enforces.
+    spvtools::SpirvTools tools(SPV_ENV_VULKAN_1_1);
+    String validatorMessages;
+    tools.SetMessageConsumer([&validatorMessages](spv_message_level_t, const char*, const spv_position_t&,
+                                                  const char* message) {
+        if (message != nullptr) validatorMessages += String(message) + "\n";
+    });
+    EXPECT_TRUE(tools.Validate(vertexBinary))
+        << "the raw vertex module is not valid SPIR-V; Adreno rejects the whole pipeline for this "
+        << "while lavapipe tolerates it:\n"
+        << validatorMessages;
+
+    // ...and, independently of the validator, every non-built-in Input carries a UNIQUE location.
+    constexpr unsigned kOpDecorate = 71, kOpVariable = 59;
+    constexpr unsigned kDecorationBuiltIn = 11, kDecorationLocation = 30;
+    constexpr unsigned kStorageClassInput = 1;
+    std::map<unsigned, unsigned> locationById;
+    std::set<unsigned> builtInIds;
+    std::vector<unsigned> inputIds;
+    for (SizeT i = 5; i < vertexBinary.size();) { // 5-word header
+        const unsigned wordCount = vertexBinary[i] >> 16;
+        const unsigned opcode = vertexBinary[i] & 0xFFFFu;
+        ASSERT_GT(wordCount, 0u) << "malformed SPIR-V instruction stream";
+        if (i + wordCount > vertexBinary.size()) break;
+        if (opcode == kOpDecorate && wordCount >= 4 && vertexBinary[i + 2] == kDecorationLocation) {
+            locationById[vertexBinary[i + 1]] = vertexBinary[i + 3];
+        } else if (opcode == kOpDecorate && wordCount >= 3 && vertexBinary[i + 2] == kDecorationBuiltIn) {
+            builtInIds.insert(vertexBinary[i + 1]);
+        } else if (opcode == kOpVariable && wordCount >= 4 && vertexBinary[i + 3] == kStorageClassInput) {
+            inputIds.push_back(vertexBinary[i + 2]);
+        }
+        i += wordCount;
+    }
+
+    std::set<unsigned> usedLocations;
+    SizeT checked = 0;
+    for (const unsigned id : inputIds) {
+        if (builtInIds.count(id) != 0) continue;
+        const auto it = locationById.find(id);
+        ASSERT_NE(it, locationById.end())
+            << "vertex input id " << id << " reached SPIR-V with no Location decoration";
+        EXPECT_TRUE(usedLocations.insert(it->second).second)
+            << "two vertex inputs were assigned location " << it->second;
+        ++checked;
+    }
+    EXPECT_GE(checked, 7u) << "expected all seven declared inputs to be present in the raw module";
+}

MobileGL/MG_Util/Async/ShaderCompilePool.cpp

@@ -126,6 +126,15 @@ namespace MobileGL::MG_Util::Async {
         return AsyncShaderCompileEnabled() && !IsAsyncShaderCompileSuspended();
     }
 
+    Bool OptimisticShaderStatusActive() {
+        switch (MG_Config::Features.AsyncOptimisticShaderStatus) {
+        case MG_Config::QuirkOverride::ForceOn: return AsyncShaderCompileActive();
+        case MG_Config::QuirkOverride::ForceOff: return false;
+        case MG_Config::QuirkOverride::Auto: break;
+        }
+        return kOptimisticShaderStatusDefault && AsyncShaderCompileActive();
+    }
+
     Uint DetectShaderCompileThreadCount() {
         if (const Uint32 configured = MG_Config::Features.AsyncShaderCompileThreads; configured > 0) {
             // An explicit request is honoured as given - it is the escape hatch for measuring

MobileGL/MG_Util/Async/ShaderCompilePool.h

@@ -59,6 +59,21 @@ namespace MobileGL::MG_Util::Async {
     // GL_COMPLETION_STATUS_KHR read immediately GL_TRUE.
     Bool AsyncShaderCompileActive();
 
+    // MOBILEGL_ASYNC_OPTIMISTIC_SHADER_STATUS (see Config.h): opt-in, off by default, and a
+    // spec violation by design - GL_COMPILE_STATUS and the shader info log answer
+    // optimistically while the compile job is in flight instead of joining it. Do not flip
+    // this default without an enumerated CTS delta: the compile-error-reporting cases WILL
+    // regress under it, deliberately.
+    inline constexpr Bool kOptimisticShaderStatusDefault = false;
+
+    // The one question the three optimistic getter sites ask. ANDed with
+    // AsyncShaderCompileActive() so that async-off (env kill switch) and
+    // glMaxShaderCompilerThreadsKHR(0) both switch the quirk off structurally: in those
+    // modes every compile settles before its enqueue returns, so a non-terminal node - the
+    // only state the quirk changes - cannot exist, and keeping the AND means there is no
+    // new mode interaction to reason about.
+    Bool OptimisticShaderStatusActive();
+
     // min(4, big cores), where a big core is one whose cpufreq ceiling is within 15% of the
     // machine maximum; the whole CPU count where that sysfs tree is absent. Clamped to [1, 4]
     // because peak RSS scales as workers x largest glslang arena, and four

MobileGL/MG_Util/ShaderTranspiler/glslang/TMglGlslIoResolver.cpp

@@ -105,8 +105,46 @@ namespace MobileGL {
     }
 
     int TMglGlslIoResolver::resolveInOutLocation(EShLanguage stage, glslang::TVarEntryInfo& ent) {
-        if (!ent.live && stage == EShLangVertex && ent.symbol->getType().getQualifier().isPipeInput()) {
+        // NO dead-vertex-input early-out here, deliberately - the skip belongs in
-            return ent.newLocation = -1;
+        // reserverStorageSlot() and ONLY there.
+        //
+        // Skipping RESERVATION is the GL semantic: only active inputs get generic attribute
+        // locations, so a dead declaration must not consume a slot an active input should
+        // have. Skipping RESOLUTION as well used to look like the same statement, but it is a
+        // different one: it leaves the variable with no layoutLocation, and glslang still
+        // EMITS it - a declared input is in the shader's linker objects and therefore in the
+        // entry point's interface. The result is an OpVariable of storage class Input with no
+        // Location decoration, which SPIR-V forbids
+        // (VUID-StandaloneSpirv-Location-04916). lavapipe tolerates it; Adreno rejects the
+        // whole pipeline with VK_ERROR_UNKNOWN, which is how this shipped undetected - every
+        // desktop gate, retrace corpus included, is blind to it.
+        //
+        // Found 2026-08-11 on an Adreno 830: the Iris weather program (mc_midTexCoord among
+        // seven attributes, only some of them glBindAttribLocation-bound) died at the first
+        // rainy-world draw, 100% reproducible, programHash 0x4a7e9a37fb49caa1.
+        //
+        // They cannot simply be handed to the base resolver either. Auto-assignment for inputs
+        // WITHOUT an explicit binding happens entirely in the resolve pass, in sort order, so a
+        // dead declaration reaching the free-slot search first would take location 0 and push
+        // the active input up - which is precisely the GL violation the reservation skip
+        // exists to prevent (ProgramTest.InactiveExplicitVertexBindingsDoNotReserveLocations
+        // pins it: Iris injects Position/UV0 into packs that actually read vaPosition).
+        //
+        // So dead inputs get their locations from the TOP of the attribute range downward,
+        // while the base resolver hands active ones out from 0 upward. Both properties hold at
+        // once: every emitted input carries a Location, and no active input is displaced. The
+        // two allocators can only meet if live + dead exceed the attribute limit, which is an
+        // over-subscribed program GL would reject anyway; if that happens we leave the
+        // variable to the base resolver rather than hand out a colliding location.
+        const glslang::TType& type = ent.symbol->getType();
+        if (!ent.live && stage == EShLangVertex && type.getQualifier().isPipeInput() &&
+            !type.getQualifier().hasLocation() && !type.isBuiltIn()) {
+            const int size = std::max(1, glslang::TIntermediate::computeTypeLocationSize(type, stage));
+            if (m_nextInactiveVertexInLocation - (size - 1) >= 0) {
+                m_nextInactiveVertexInLocation -= (size - 1);
+                ent.symbol->getWritableType().getQualifier().layoutLocation = m_nextInactiveVertexInLocation;
+                --m_nextInactiveVertexInLocation;
+            }
         }
         return TDefaultGlslIoResolver::resolveInOutLocation(stage, ent);
     }

MobileGL/MG_Util/ShaderTranspiler/glslang/TMglGlslIoResolver.h

@@ -51,5 +51,13 @@ namespace MobileGL {
         std::map<glslang::TString, int> m_plainUniformLocationSizeByName;
         std::map<glslang::TString, int> m_plainUniformLocationByName;
         bool m_plainUniformLocationsAssigned = false;
+        // Descending allocator for INACTIVE vertex inputs (see resolveInOutLocation): they
+        // still have to carry a Location because glslang emits them, but they must not take a
+        // slot an active input would get. 15, not 31: the location survives into the ESSL
+        // SPIRV-Cross emits for DirectGLES, and GL/ES only guarantee GL_MAX_VERTEX_ATTRIBS
+        // >= 16 - a location of 31 makes the generated shader fail to compile on a real ES
+        // driver (caught by the super-duper-vanilla and chocapic retrace fixtures).
+        static constexpr int kInactiveVertexInLocationTop = 15;
+        int m_nextInactiveVertexInLocation = kInactiveVertexInLocationTop;
     };
 } // namespace MobileGL