[Fix] (MG_Impl/GLImpl): reject the RGTC internal formats on 3D texture targets - RGTC compresses 4x4 blocks of a 2D image and has no 3D form, and the check must run on the raw enum because RGTC now resolves to plain R8/RG8 storage

CMakeLists.txt

@@ -188,6 +188,7 @@ set(SOURCE_FILES
     MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/EliminateFloatEqualsZeroPass.cpp
     MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/RenameSamplerFunctionParameterPass.cpp
     MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/DecomposeWorkgroupVec3Pass.cpp
+    MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/DecoratePositionInvariantPass.cpp
     MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/LowerDrawParametersPass.cpp
     MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/RebaseInstanceIndexPass.cpp
     MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/StripUboMemberRelaxedPrecisionPass.cpp

MobileGL/MG_Backend/DirectGLES/Managers.cpp

@@ -2216,11 +2216,17 @@ namespace MobileGL::MG_Backend::DirectGLES {
                 return;
             }
 
-            if (TextureImpl::IsMultisampleTextureTarget(targetInternal)) {
+            // Multisample targets reject the *sampler* parameters (LOD range, border color) but
+            // GL_TEXTURE_SWIZZLE_* is texture state, not sampler state, and ES accepts it on them.
+            // Bailing out entirely used to drop every swizzle write on the floor, which is what the
+            // frontend already assumes is legal (see GL_Texture.cpp's MS-invalid pname list, which
+            // deliberately omits the swizzle enums). Note the caches for the skipped parameters are
+            // still refreshed so they never look stale, but m_cacheSwizzleParams must NOT be, or the
+            // change detection below would swallow the very writes we came here to emit.
+            const Bool isMultisampleTarget = TextureImpl::IsMultisampleTextureTarget(targetInternal);
+            if (isMultisampleTarget) {
                 m_cacheLodRange = stateTextureObject->GetLevelRange();
-                m_cacheSwizzleParams = stateTextureObject->GetAllSwizzleParams();
                 m_cacheBorderColor = stateTextureObject->GetBorderColor();
-                return;
             }
 
             Bind(target);
@@ -2233,14 +2239,14 @@ namespace MobileGL::MG_Backend::DirectGLES {
 
             const auto& levelRange = stateTextureObject->GetLevelRange();
 
-            if (m_cacheLodRange.x() != levelRange.x()) {
+            if (!isMultisampleTarget && m_cacheLodRange.x() != levelRange.x()) {
                 g_GLESFuncs.glTexParameteri(target, GL_TEXTURE_BASE_LEVEL, static_cast<GLint>(levelRange.x()));
                 m_cacheLodRange.x() = levelRange.x();
             }
             DebugImpl::ErrorLopper::Loop([file = __FILE__, line = __LINE__, func = __func__](GLenum err) {
                 MGLOG_D("%s(%s:%d) ES error %s", func, file, line, MG_Util::ConvertGLEnumToString(err).c_str());
             });
-            if (m_cacheLodRange.y() != levelRange.y()) {
+            if (!isMultisampleTarget && m_cacheLodRange.y() != levelRange.y()) {
                 g_GLESFuncs.glTexParameteri(target, GL_TEXTURE_MAX_LEVEL, static_cast<GLint>(levelRange.y()));
                 m_cacheLodRange.y() = levelRange.y();
             }
@@ -2266,7 +2272,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
                 });
             }
 
-            if (m_cacheBorderColor != stateTextureObject->GetBorderColor()) {
+            if (!isMultisampleTarget && m_cacheBorderColor != stateTextureObject->GetBorderColor()) {
                 const auto& borderColor = stateTextureObject->GetBorderColor();
                 GLfloat borderColorArray[4] = {borderColor.x(), borderColor.y(), borderColor.z(), borderColor.w()};
                 g_GLESFuncs.glTexParameterfv(target, GL_TEXTURE_BORDER_COLOR, borderColorArray);

MobileGL/MG_Backend/DirectVulkan/Renderer/ProgramFactory.cpp

@@ -312,34 +312,6 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             return targetEnv;
         }
 
-        // Cheap raw-word scan for an `OpDecorate <id> BuiltIn InstanceIndex` decoration. Used
-        // only to decide whether to warn when shaderDrawParameters is unavailable; a false
-        // negative merely suppresses a diagnostic.
-        Bool SpirvDeclaresInstanceIndexBuiltin(const Vector<Uint>& spirv) {
-            constexpr Uint32 kSpirvMagicNumber = 0x07230203u;
-            constexpr SizeT kHeaderWordCount = 5;
-            if (spirv.size() <= kHeaderWordCount || spirv[0] != kSpirvMagicNumber) {
-                return false;
-            }
-
-            SizeT wordIndex = kHeaderWordCount;
-            while (wordIndex < spirv.size()) {
-                const Uint32 firstWord = spirv[wordIndex];
-                const Uint32 wordCount = firstWord >> 16;
-                const auto opcode = static_cast<spv::Op>(firstWord & 0xffffu);
-                if (wordCount == 0 || wordIndex + wordCount > spirv.size()) {
-                    break;
-                }
-                if (opcode == spv::Op::OpDecorate && wordCount >= 4 &&
-                    static_cast<spv::Decoration>(spirv[wordIndex + 2]) == spv::Decoration::BuiltIn &&
-                    static_cast<spv::BuiltIn>(spirv[wordIndex + 3]) == spv::BuiltIn::InstanceIndex) {
-                    return true;
-                }
-                wordIndex += wordCount;
-            }
-            return false;
-        }
-
         Bool IsInterfaceVariableStaticallyUsed(const Vector<Uint>& spirv, Uint32 spirvId) {
             if (spirv.empty() || spirvId == 0) {
                 return false;
@@ -1234,6 +1206,25 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         return false;
     }
 
+    // glslang's relaxed-Vulkan mode maps GL's gl_InstanceID onto the InstanceIndex builtin.
+    // Without shaderDrawParameters there is no gl_BaseInstance to subtract, so such a shader
+    // cannot be corrected and instanced draws with a non-zero baseInstance misrender; this
+    // detects the case so the user gets one warning instead of silent corruption.
+    Bool ProgramFactory::ReflectedReadsInstanceIndexBuiltin(const SpvReflectShaderModule& reflectModule) {
+        for (Uint32 entryIndex = 0; entryIndex < reflectModule.entry_point_count; ++entryIndex) {
+            const SpvReflectEntryPoint& entryPoint = reflectModule.entry_points[entryIndex];
+            for (Uint32 variableIndex = 0; variableIndex < entryPoint.input_variable_count; ++variableIndex) {
+                const SpvReflectInterfaceVariable* variable = entryPoint.input_variables[variableIndex];
+                if (variable != nullptr &&
+                    (variable->decoration_flags & SPV_REFLECT_DECORATION_BUILT_IN) != 0 &&
+                    variable->built_in == SpvBuiltInInstanceIndex) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
     VkShaderStageFlagBits ProgramFactory::ToVkStage(ShaderStage stage) {
         switch (stage) {
         case ShaderStage::Vertex:
@@ -1481,6 +1472,15 @@ namespace MobileGL::MG_Backend::DirectVulkan {
                 continue;
             }
 
+            if (!m_shaderDrawParametersEnabled && ReflectedReadsInstanceIndexBuiltin(reflectModule)) {
+                static Bool s_warnedInstanceIndexUnsupported = false;
+                if (!s_warnedInstanceIndexUnsupported) {
+                    s_warnedInstanceIndexUnsupported = true;
+                    MGLOG_W("ProgramFactory: shaderDrawParameters is unavailable; gl_InstanceID cannot be "
+                            "rebased and instanced draws with a non-zero baseInstance may render incorrectly");
+                }
+            }
+
             uint32_t inputCount = 0;
             SpvReflectResult reflectResult = spvReflectEnumerateInputVariables(&reflectModule, &inputCount, nullptr);
             MOBILEGL_ASSERT(reflectResult == SPV_REFLECT_RESULT_SUCCESS,
@@ -1892,8 +1892,12 @@ namespace MobileGL::MG_Backend::DirectVulkan {
                         moduleSpirvs[i], invariantSpirv)) {
                     moduleSpirvs[i] = std::move(invariantSpirv);
                 } else {
-                    MGLOG_W("ProgramFactory: position-invariant decoration failed for program %u; "
+                    // The pass round-trips through SPIRV-Tools IR, so an unparseable module
-                            "keeping the original module",
+                    // fails open and keeps the undecorated words - which silently reinstates
+                    // the multi-pass invariance bug rather than breaking anything loudly.
+                    MGLOG_E("ProgramFactory: position-invariant decoration failed for program %u; "
+                            "keeping the original module - multi-pass depth-equality chains "
+                            "(e.g. MC 26.3 OIT clouds) may drop primitives on this device",
                             program.GetExternalIndex());
                 }
             }
@@ -1902,24 +1906,19 @@ namespace MobileGL::MG_Backend::DirectVulkan {
             // gl_InstanceIndex, which wrongly includes the draw's baseInstance. Rebase vertex-stage
             // loads to (InstanceIndex - BaseInstance) so shaders observe GL semantics. Reflection
             // below runs on the rebased words so the added BaseInstance builtin stays consistent.
-            if (shaders[i] && shaders[i]->GetShaderStage() == ShaderStage::Vertex) {
+            // The unsupported-device counterpart of this rebase (warning when a shader reads
-                if (m_shaderDrawParametersEnabled) {
+            // the builtin but shaderDrawParameters is missing) rides along with
-                    Vector<Uint> rebasedSpirv;
+            // ReflectVertexInputs, which already reflects this stage.
-                    if (MG_Util::ShaderTranspiler::ShaderCompiler::RebaseInstanceIndexForVulkan(moduleSpirvs[i],
+            if (shaders[i] && shaders[i]->GetShaderStage() == ShaderStage::Vertex &&
-                                                                                               rebasedSpirv)) {
+                m_shaderDrawParametersEnabled) {
-                        moduleSpirvs[i] = std::move(rebasedSpirv);
+                Vector<Uint> rebasedSpirv;
-                    } else {
+                if (MG_Util::ShaderTranspiler::ShaderCompiler::RebaseInstanceIndexForVulkan(moduleSpirvs[i],
-                        MGLOG_E("ProgramFactory: failed to rebase gl_InstanceID for program %u; "
+                                                                                            rebasedSpirv)) {
-                                "instanced draws with a non-zero baseInstance may render incorrectly",
+                    moduleSpirvs[i] = std::move(rebasedSpirv);
-                                program.GetExternalIndex());
+                } else {
-                    }
+                    MGLOG_E("ProgramFactory: failed to rebase gl_InstanceID for program %u; "
-                } else if (SpirvDeclaresInstanceIndexBuiltin(moduleSpirvs[i])) {
+                            "instanced draws with a non-zero baseInstance may render incorrectly",
-                    static Bool s_warnedInstanceIndexUnsupported = false;
+                            program.GetExternalIndex());
-                    if (!s_warnedInstanceIndexUnsupported) {
-                        s_warnedInstanceIndexUnsupported = true;
-                        MGLOG_W("ProgramFactory: shaderDrawParameters is unavailable; gl_InstanceID cannot be "
-                                "rebased and instanced draws with a non-zero baseInstance may render incorrectly");
-                    }
                 }
             }
 

MobileGL/MG_Backend/DirectVulkan/Renderer/ProgramFactory.h

@@ -223,6 +223,9 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         // can be pinned by tests. A false negative loses the exemption, so such a shader is
         // stripped conservatively and forfeits its depth write.
         static Bool ReflectedFragmentReplacesDepth(const SpvReflectShaderModule& reflectModule);
+        // True when an entry point reads the InstanceIndex builtin. Only gates a diagnostic:
+        // without shaderDrawParameters such a shader cannot have gl_InstanceID rebased.
+        static Bool ReflectedReadsInstanceIndexBuiltin(const SpvReflectShaderModule& reflectModule);
 
     private:
         struct ProgramLookupCache {

MobileGL/MG_Impl/GLImpl/Exporting/Definitions.cpp

@@ -295,7 +295,13 @@ DECLARE_GL_FUNCTION_HEAD(void, VertexAttribDivisor, GLuint index, GLuint divisor
 DECLARE_GL_FUNCTION_STUB_HEAD(void, BindTransformFeedback, GLenum target, GLuint id) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, BindTransformFeedback, target, id)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, DeleteTransformFeedbacks, GLsizei n, const GLuint* ids) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, DeleteTransformFeedbacks, n, ids)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, GenTransformFeedbacks, GLsizei n, GLuint* ids) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, GenTransformFeedbacks, n, ids)
-DECLARE_GL_FUNCTION_STUB_HEAD(GLboolean, IsTransformFeedback, GLuint id) DECLARE_GL_FUNCTION_STUB_END(GLboolean, IsTransformFeedback, id)
+// Transform feedback objects are not implemented, so no name is ever a live object. The shared
+// stub returns (type)1, telling a probing caller that every id it invents already exists; GL_FALSE
+// is both truthful and what the spec requires for a name that was never generated.
+MOBILEGL_GL_API GLboolean glIsTransformFeedback(GLuint id) {
+    MGLOG_W("Stub function: %s(...)", __FUNCTION__);
+    return GL_FALSE;
+}
 DECLARE_GL_FUNCTION_STUB_HEAD(void, PauseTransformFeedback) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, PauseTransformFeedback)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, ResumeTransformFeedback) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, ResumeTransformFeedback)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, GetProgramBinary, GLuint program, GLsizei bufSize, GLsizei* length, GLenum* binaryFormat, void* binary) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, GetProgramBinary, program, bufSize, length, binaryFormat, binary)
@@ -2583,7 +2589,10 @@ DECLARE_GL_FUNCTION_STUB_HEAD(void, TransformFeedbackStreamAttribsNV, GLsizei co
 DECLARE_GL_FUNCTION_STUB_HEAD(void, BindTransformFeedbackNV, GLenum target, GLuint id) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, BindTransformFeedbackNV, target, id)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, DeleteTransformFeedbacksNV, GLsizei n, const GLuint* ids) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, DeleteTransformFeedbacksNV, n, ids)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, GenTransformFeedbacksNV, GLsizei n, GLuint* ids) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, GenTransformFeedbacksNV, n, ids)
-DECLARE_GL_FUNCTION_STUB_HEAD(GLboolean, IsTransformFeedbackNV, GLuint id) DECLARE_GL_FUNCTION_STUB_END(GLboolean, IsTransformFeedbackNV, id)
+MOBILEGL_GL_API GLboolean glIsTransformFeedbackNV(GLuint id) {
+    MGLOG_W("Stub function: %s(...)", __FUNCTION__);
+    return GL_FALSE;
+}
 DECLARE_GL_FUNCTION_STUB_HEAD(void, PauseTransformFeedbackNV, void) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, PauseTransformFeedbackNV, )
 DECLARE_GL_FUNCTION_STUB_HEAD(void, ResumeTransformFeedbackNV, void) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, ResumeTransformFeedbackNV, )
 DECLARE_GL_FUNCTION_STUB_HEAD(void, DrawTransformFeedbackNV, GLenum mode, GLuint id) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, DrawTransformFeedbackNV, mode, id)

MobileGL/MG_Impl/GLImpl/Texture/GL_Texture.cpp

@@ -350,6 +350,10 @@ namespace MobileGL::MG_Impl::GLImpl {
                 texture.AllocateStorage(uploadTarget, level, {levelTexelSize, levelByteSize});
                 texture.MarkStorageDirty(uploadTarget, level, false);
             }
+            // glGenerateMipmap defines exactly levels 0..requiredLevelCount-1. AllocateStorage only
+            // grows, so a previously longer chain (a bigger base image before respecification) would
+            // otherwise keep a tail of stale levels here and read as incomplete.
+            texture.TruncateMipmapLevels(uploadTarget, requiredLevelCount);
             // Mip generation grows/regenerates the level set on the GPU without marking any CPU
             // level dirty (MarkStorageDirty(...,false) above). Bump the content version so the
             // backend re-syncs: a cached sampled VkImageView built for the pre-generate level
@@ -429,8 +433,10 @@ namespace MobileGL::MG_Impl::GLImpl {
 
             const Int maxSamples = GetMaxSupportedTextureSamples(textureInternalFormat);
             if (samples > maxSamples) {
+                // GL specifies INVALID_OPERATION - not INVALID_VALUE - when the sample count
+                // exceeds what the format supports, and the native Adreno driver agrees.
                 MG_State::pGLContext->RecordError(
-                    ErrorCode::InvalidValue,
+                    ErrorCode::InvalidOperation,
                     MakeUnique<GenericErrorInfo>(
                         "MG_Impl/GLImpl", caller,
                         std::format("Sample count {} exceeds the supported maximum {} for this texture format.",
@@ -454,8 +460,56 @@ namespace MobileGL::MG_Impl::GLImpl {
             textureObject->SetSamples(samples);
             textureObject->SetFixedSampleLocations(fixedsamplelocations == GL_TRUE);
             textureMipmapObject->AllocateStorage(textureUploadTarget, 0, {{width, height, depth}, 0});
+            // Multisample textures are single-level by definition, so a name that previously held a
+            // mip chain must not keep its tail now that AllocateStorage only grows.
+            textureMipmapObject->TruncateMipmapLevels(textureUploadTarget, 1);
             textureMipmapObject->MarkStorageDirty(textureUploadTarget, 0, false);
         }
+
+        // Redefining level 0 of a texture that already had a base image drops the rest of the chain,
+        // which is exactly what AllocateLevel used to do implicitly for every level. Keeping that
+        // behaviour for level 0 - and only for level 0 - is what makes the grow-only change safe:
+        // any level-0 respecification leaves the chain in precisely the state it would have had
+        // before, while an upload to level N no longer destroys the levels beneath it.
+        //
+        // Why it has to be *every* level-0 respecification and not just a size change: Minecraft's
+        // Mipmap Levels setting rebuilds the block atlas at the SAME dimensions with a different
+        // level count. A size-only test would leave the old tail in place, and because Mojang
+        // terminates its chains with a 0x0 level the result is the zero-then-nonzero pattern that
+        // IsComplete() rejects (TextureObject.cpp) - whereupon DirectGLES skips syncing the texture
+        // entirely (Managers.cpp) and the atlas samples black.
+        //
+        // The "already has a base image" test is what lets the fix work at all: a level that was
+        // never written reads back as {0,0,0}, so building a chain top-down - upload level N first,
+        // then level 0 - must not discard the levels just uploaded. That ordering is what
+        // KHR-GL33.texture_repeat_mode does.
+        // Scoped to the respecified upload target only, which is what AllocateLevel already did.
+        // Cube maps keep six independent chains while reporting a single level count (face +X), so
+        // respecifying a face other than +X can leave the count longer than that face - but that
+        // asymmetry predates this change and widening the truncation to all six faces would destroy
+        // mip data for faces the application never touched. Left alone deliberately.
+        void DiscardMipmapChainOnBaseRespecification(MG_State::GLState::TextureObjectMipmap* texture,
+                                                     TextureUploadTarget uploadTarget, Uint level) {
+            if (level != 0) return;
+
+            const IntVec3 existingBaseSize = texture->GetMipmapTexelSize(uploadTarget, 0);
+            const Bool hasExistingBaseImage =
+                existingBaseSize.x() > 0 && existingBaseSize.y() > 0 && existingBaseSize.z() > 0;
+            if (!hasExistingBaseImage) return;
+
+            texture->TruncateMipmapLevels(uploadTarget, 1);
+        }
+
+        // Compressed texture upload is not implemented yet. GL_NUM_COMPRESSED_TEXTURE_FORMATS
+        // reports 0, so every compressed internalformat is by definition unsupported and
+        // GL_INVALID_ENUM is the specified error - unlike THROW_UNIMPL_EXCEPTION, which unwinds
+        // a C++ exception through the C GL ABI and takes the process down.
+        void RecordUnsupportedCompressedFormat(const char* caller) {
+            MG_State::pGLContext->RecordError(
+                ErrorCode::InvalidEnum,
+                MakeUnique<GenericErrorInfo>("MG_Impl/GLImpl", caller,
+                                             "Compressed texture formats are not supported."));
+        }
     } // namespace
 
     const SharedPtr<MG_State::GLState::ITextureObject>& GetTextureObjectByName(GLuint texture, const char* caller) {
@@ -1742,6 +1796,7 @@ namespace MobileGL::MG_Impl::GLImpl {
         if (isProxy) {
             MGLOG_D("%s: isProxy = true, not allocating", __func__);
         } else {
+            DiscardMipmapChainOnBaseRespecification(textureMipmapObject, textureUploadTarget, level);
             textureMipmapObject->AllocateStorage(textureUploadTarget, level, {{width, height, depth}, internalBytes});
         }
 
@@ -1869,6 +1924,7 @@ namespace MobileGL::MG_Impl::GLImpl {
             MGLOG_D("%s: isProxy = true, not allocating", __func__);
         } else {
             MGLOG_D("%s: Allocating %d bytes at mip %d", __func__, internalBytes, level);
+            DiscardMipmapChainOnBaseRespecification(textureMipmapObject, textureUploadTarget, level);
             textureMipmapObject->AllocateStorage(textureUploadTarget, level,
                                                  {{width, height, 1}, internalBytes});
         }
@@ -1957,6 +2013,7 @@ namespace MobileGL::MG_Impl::GLImpl {
                         "Texture object here should always be an object with mipmap");
         auto textureMipmapObject = static_cast<MG_State::GLState::TextureObjectMipmap*>(textureObject.get());
         if (!isProxy) {
+            DiscardMipmapChainOnBaseRespecification(textureMipmapObject, textureUploadTarget, level);
             textureMipmapObject->AllocateStorage(textureUploadTarget, level, {{width, 1, 1}, internalBytes});
         }
 
@@ -2609,7 +2666,13 @@ namespace MobileGL::MG_Impl::GLImpl {
     }
 
     void GetCompressedTexImage_State(GLenum target, GLint level, void* img) {
-        // TODO: implement
+        // TODO: implement compressed readback. Reporting success while writing nothing hands
+        // the caller stale memory with GL_NO_ERROR; no texture can be compressed yet, and GL
+        // specifies GL_INVALID_OPERATION when the bound level is not compressed.
+        MG_State::pGLContext->RecordError(
+            ErrorCode::InvalidOperation,
+            MakeUnique<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                         "Texture level is not stored in a compressed format."));
     }
 
     void GenTextures_State(GLsizei n, GLuint* textures) {
@@ -2796,20 +2859,20 @@ namespace MobileGL::MG_Impl::GLImpl {
     void CompressedTexSubImage3D_State(GLenum target, GLint level, GLint xoffset, GLint yoffset, GLint zoffset,
                                        GLsizei width, GLsizei height, GLsizei depth, GLenum format, GLsizei imageSize,
                                        const void* data) {
-        // TODO: implement
+        // TODO: implement compressed upload - see CompressedTexImage2D_State.
-        THROW_UNIMPL_EXCEPTION;
+        RecordUnsupportedCompressedFormat(__func__);
     }
 
     void CompressedTexSubImage2D_State(GLenum target, GLint level, GLint xoffset, GLint yoffset, GLsizei width,
                                        GLsizei height, GLenum format, GLsizei imageSize, const void* data) {
-        // TODO: implement
+        // TODO: implement compressed upload - see CompressedTexImage2D_State.
-        THROW_UNIMPL_EXCEPTION;
+        RecordUnsupportedCompressedFormat(__func__);
     }
 
     void CompressedTexSubImage1D_State(GLenum target, GLint level, GLint xoffset, GLsizei width, GLenum format,
                                        GLsizei imageSize, const void* data) {
-        // TODO: implement
+        // TODO: implement compressed upload - see CompressedTexImage2D_State.
-        THROW_UNIMPL_EXCEPTION;
+        RecordUnsupportedCompressedFormat(__func__);
     }
 
     void CompressedTexImage3D_State(GLenum target, GLint level, GLenum internalformat, GLsizei width, GLsizei height,
@@ -2819,8 +2882,8 @@ namespace MobileGL::MG_Impl::GLImpl {
         auto& textureObject = GetTextureObjectByTarget(textureUploadTarget, textureTarget);
         if (!ValidateTextureMutable(textureObject, __func__)) return;
 
-        // TODO: implement
+        // TODO: implement compressed upload - see CompressedTexImage2D_State.
-        THROW_UNIMPL_EXCEPTION;
+        RecordUnsupportedCompressedFormat(__func__);
     }
 
     void CompressedTexImage2D_State(GLenum target, GLint level, GLenum internalformat, GLsizei width, GLsizei height,
@@ -2830,8 +2893,11 @@ namespace MobileGL::MG_Impl::GLImpl {
         auto& textureObject = GetTextureObjectByTarget(textureUploadTarget, textureTarget);
         if (!ValidateTextureMutable(textureObject, __func__)) return;
 
-        // TODO: implement
+        // TODO: implement compressed upload. Until then report the spec error for an
-        THROW_UNIMPL_EXCEPTION;
+        // unsupported compressed format rather than throwing - a C++ exception unwinding
+        // through the C GL ABI is a hard crash for the caller, while GL_INVALID_ENUM is
+        // exactly what GL_NUM_COMPRESSED_TEXTURE_FORMATS == 0 promises.
+        RecordUnsupportedCompressedFormat(__func__);
     }
 
     void CompressedTexImage1D_State(GLenum target, GLint level, GLenum internalformat, GLsizei width, GLint border,
@@ -2841,8 +2907,8 @@ namespace MobileGL::MG_Impl::GLImpl {
         auto& textureObject = GetTextureObjectByTarget(textureUploadTarget, textureTarget);
         if (!ValidateTextureMutable(textureObject, __func__)) return;
 
-        // TODO: implement
+        // TODO: implement compressed upload - see CompressedTexImage2D_State.
-        THROW_UNIMPL_EXCEPTION;
+        RecordUnsupportedCompressedFormat(__func__);
     }
 
     void BindTexture_State(GLenum target, GLuint texture) {
@@ -3188,6 +3254,9 @@ namespace MobileGL::MG_Impl::GLImpl {
             textureMipmapObject->AllocateStorage(textureUploadTarget, level, {{levelWidth, 1, 1}, byteSize});
             textureMipmapObject->MarkStorageDirty(textureUploadTarget, level, false);
         }
+        // Immutable storage defines exactly `levels` levels; AllocateStorage only grows, so a
+        // longer pre-existing chain has to be dropped explicitly.
+        textureMipmapObject->TruncateMipmapLevels(textureUploadTarget, static_cast<Uint>(levels));
         textureObject->SetImmutableLevels(static_cast<Uint>(levels));
     }
 
@@ -3240,6 +3309,8 @@ namespace MobileGL::MG_Impl::GLImpl {
             textureMipmapObject->AllocateStorage(textureUploadTarget, level, {{levelWidth, levelHeight, 1}, byteSize});
             textureMipmapObject->MarkStorageDirty(textureUploadTarget, level, false);
         }
+        // See TextureStorage1D.
+        textureMipmapObject->TruncateMipmapLevels(textureUploadTarget, static_cast<Uint>(levels));
         textureObject->SetImmutableLevels(static_cast<Uint>(levels));
     }
 
@@ -3292,6 +3363,8 @@ namespace MobileGL::MG_Impl::GLImpl {
                                                  {{levelWidth, levelHeight, levelDepth}, byteSize});
             textureMipmapObject->MarkStorageDirty(textureUploadTarget, level, false);
         }
+        // See TextureStorage1D.
+        textureMipmapObject->TruncateMipmapLevels(textureUploadTarget, static_cast<Uint>(levels));
         textureObject->SetImmutableLevels(static_cast<Uint>(levels));
     }
 

MobileGL/MG_State/GLState/TextureState/MipmapStorage.cpp

@@ -16,17 +16,32 @@ namespace MobileGL {
             }
 
             void MipmapStorage::AllocateLevel(Uint level, MipmapInput input) {
-                m_data.reserve(std::bit_ceil(level + 1));
+                // Grow only. GL respecifies exactly the level it is handed, so allocating level 0
-                m_data.resize(level + 1);
+                // must not disturb the levels above it - but resize() shrinks as readily as it
-                m_texelSizes.reserve(std::bit_ceil(level + 1));
+                // grows, so this used to truncate the whole chain to a single level. Callers that
-                m_texelSizes.resize(level + 1);
+                // genuinely redefine the complete level set say so with TruncateToLevelCount.
-                m_texelSizes[level] = input.texelSize;
+                const SizeT requiredLevelCount = static_cast<SizeT>(level) + 1;
-                m_isDirty.resize(level + 1, false);
+                if (m_data.size() < requiredLevelCount) {
+                    m_data.reserve(std::bit_ceil(requiredLevelCount));
+                    m_data.resize(requiredLevelCount);
+                    m_texelSizes.reserve(std::bit_ceil(requiredLevelCount));
+                    m_texelSizes.resize(requiredLevelCount);
+                    m_isDirty.resize(requiredLevelCount, false);
+                }
 
+                m_texelSizes[level] = input.texelSize;
                 auto& data = m_data[level];
                 data.resize(input.byteSize, 0);
             }
 
+            void MipmapStorage::TruncateToLevelCount(SizeT levelCount) {
+                if (levelCount >= m_data.size()) return;
+
+                m_data.resize(levelCount);
+                m_texelSizes.resize(levelCount);
+                m_isDirty.resize(levelCount);
+            }
+
             void MipmapStorage::UpdateSubData(Uint level, DataPtr input) {
                 auto& targetData = m_data;
                 MOBILEGL_ASSERT(level < targetData.size(), "UpdateSubData: level out of range");
@@ -55,6 +70,7 @@ namespace MobileGL {
             }
 
             SizeT MipmapStorage::GetByteSize(Uint level) const {
+                if (level >= m_data.size()) return 0;
                 return m_data[level].size();
             }
 

MobileGL/MG_State/GLState/TextureState/MipmapStorage.h

@@ -19,6 +19,10 @@ namespace MobileGL {
             public:
                 SizeT GetLevelCount() const;
                 void AllocateLevel(Uint level, MipmapInput input);
+                // Discard every level at or above levelCount. AllocateLevel never shrinks, so this
+                // is the only way a chain gets shorter - use it where the caller defines the whole
+                // level set (glTexStorage*, mip regeneration, atlas respecification).
+                void TruncateToLevelCount(SizeT levelCount);
                 void UpdateSubData(Uint level, DataPtr input);
                 void* MapData(Uint level);
                 IntVec3 GetTexelSize(Uint level) const;

MobileGL/MG_State/GLState/TextureState/MipmapUploadTargetArray.h

@@ -29,6 +29,14 @@ namespace MobileGL {
                     m_storage[targetIndex].AllocateLevel(level, input);
                 }
 
+                // Per-target, like AllocateLevel: cube-map faces are respecified independently, so
+                // truncating one face must not disturb the others.
+                void TruncateToLevelCount(Uint targetIndex, SizeT levelCount) {
+                    MOBILEGL_ASSERT(targetIndex < TargetCount, "TruncateToLevelCount: target invalid");
+
+                    m_storage[targetIndex].TruncateToLevelCount(levelCount);
+                }
+
                 void UpdateSubData(Uint targetIndex, Uint level, DataPtr input) {
                     MOBILEGL_ASSERT(targetIndex < TargetCount, "UpdateSubData: target invalid");
                     m_storage[targetIndex].UpdateSubData(level, input);

MobileGL/MG_State/GLState/TextureState/TextureObject.cpp

@@ -271,6 +271,10 @@ namespace MobileGL {
                 m_textureStorage.AllocateLevel(GetIndexOfTextureUploadTarget(uploadTarget), mipmapLevel, input);
             }
 
+            void TextureObjectWithOneMipmap::TruncateMipmapLevels(TextureUploadTarget uploadTarget, Uint levelCount) {
+                m_textureStorage.TruncateToLevelCount(GetIndexOfTextureUploadTarget(uploadTarget), levelCount);
+            }
+
             void TextureObjectWithOneMipmap::UpdateMipmapSubData(TextureUploadTarget uploadTarget, Uint mipmapLevel,
                                                                  DataPtr input) {
                 m_textureStorage.UpdateSubData(GetIndexOfTextureUploadTarget(uploadTarget), mipmapLevel, input);

MobileGL/MG_State/GLState/TextureState/TextureObject.h

@@ -134,6 +134,10 @@ namespace MobileGL::MG_State::GLState {
         virtual const IntVec3 GetMipmapTexelSize(TextureUploadTarget target, Uint mipmapLevel) const = 0;
         virtual const SizeT GetMipmapByteSize(TextureUploadTarget target, Uint mipmapLevel) const = 0;
         virtual void AllocateStorage(TextureUploadTarget uploadTarget, Uint mipmapLevel, MipmapInput input) = 0;
+        // AllocateStorage only ever grows the chain. Callers that define the complete level set -
+        // glTexStorage*, mip regeneration, or a level-0 respecification at a new size - drop the
+        // leftovers explicitly, so a stale tail can never make the texture silently incomplete.
+        virtual void TruncateMipmapLevels(TextureUploadTarget uploadTarget, Uint levelCount) = 0;
         virtual void UpdateMipmapSubData(TextureUploadTarget uploadTarget, Uint mipmapLevel, DataPtr input) = 0;
         virtual void* MapMipmapData(TextureUploadTarget uploadTarget, Uint mipmapLevel) = 0;
         virtual void MarkStorageDirty(TextureUploadTarget uploadTarget, Uint mipmapLevel, Bool dirty = true) = 0;
@@ -175,6 +179,7 @@ namespace MobileGL::MG_State::GLState {
         const IntVec3 GetMipmapTexelSize(TextureUploadTarget target, Uint mipmapLevel) const override;
         const SizeT GetMipmapByteSize(TextureUploadTarget target, Uint mipmapLevel) const override;
         void AllocateStorage(TextureUploadTarget uploadTarget, Uint mipmapLevel, MipmapInput input) override;
+        void TruncateMipmapLevels(TextureUploadTarget uploadTarget, Uint levelCount) override;
         void UpdateMipmapSubData(TextureUploadTarget uploadTarget, Uint mipmapLevel, DataPtr input) override;
         void* MapMipmapData(TextureUploadTarget uploadTarget, Uint mipmapLevel) override;
         void MarkStorageDirty(TextureUploadTarget uploadTarget, Uint mipmapLevel, Bool dirty) override;

MobileGL/MG_State/GLState/TextureState/TextureObject2DCube.cpp

@@ -31,6 +31,10 @@ namespace MobileGL {
                 m_textureStorage.AllocateLevel(GetIndexOfTextureUploadTarget(uploadTarget), mipmapLevel, input);
             }
 
+            void TextureObject2DCube::TruncateMipmapLevels(TextureUploadTarget uploadTarget, Uint levelCount) {
+                m_textureStorage.TruncateToLevelCount(GetIndexOfTextureUploadTarget(uploadTarget), levelCount);
+            }
+
             void TextureObject2DCube::UpdateMipmapSubData(TextureUploadTarget uploadTarget, Uint mipmapLevel,
                                                           DataPtr input) {
                 m_textureStorage.UpdateSubData(GetIndexOfTextureUploadTarget(uploadTarget), mipmapLevel, input);

MobileGL/MG_State/GLState/TextureState/TextureObject2DCube.h

@@ -22,6 +22,7 @@ namespace MobileGL {
                 const IntVec3 GetMipmapTexelSize(TextureUploadTarget target, Uint mipmapLevel) const override;
                 const SizeT GetMipmapByteSize(TextureUploadTarget target, Uint mipmapLevel) const override;
                 void AllocateStorage(TextureUploadTarget uploadTarget, Uint mipmapLevel, MipmapInput input) override;
+                void TruncateMipmapLevels(TextureUploadTarget uploadTarget, Uint levelCount) override;
                 void UpdateMipmapSubData(TextureUploadTarget uploadTarget, Uint mipmapLevel, DataPtr input) override;
                 void* MapMipmapData(TextureUploadTarget uploadTarget, Uint mipmapLevel) override;
                 void MarkStorageDirty(TextureUploadTarget uploadTarget, Uint mipmapLevel, bool dirty) override;

MobileGL/MG_Test/CMakeLists.txt

@@ -73,6 +73,7 @@ add_subdirectory(VertexArray)
 add_subdirectory(Program)
 add_subdirectory(Query)
 add_subdirectory(Pipeline)
+add_subdirectory(ShaderTranspiler)
 if (ENABLE_INTEGRATION_TESTS)
     add_subdirectory(Backend/DirectVulkan)
 endif()

MobileGL/MG_Test/Pipeline/PipelineQuirkTest.cpp

@@ -92,6 +92,93 @@ namespace {
         0x00000005u, 0x0003003eu, 0x00000009u, 0x0000000bu, 0x000100fdu, 0x00010038u,
     };
 
+
+    // glslangValidator -V output for a vertex shader reading gl_InstanceIndex:
+    //   #version 450
+    //   layout(location = 0) in vec4 inPos;
+    //   void main() { gl_Position = inPos + vec4(float(gl_InstanceIndex)); }
+    constexpr Uint32 kInstanceIndexVertexSpirv[] = {
+        0x07230203u, 0x00010000u, 0x0008000bu, 0x0000001bu, 0x00000000u, 0x00020011u,
+        0x00000001u, 0x0006000bu, 0x00000001u, 0x4c534c47u, 0x6474732eu, 0x3035342eu,
+        0x00000000u, 0x0003000eu, 0x00000000u, 0x00000001u, 0x0008000fu, 0x00000000u,
+        0x00000004u, 0x6e69616du, 0x00000000u, 0x0000000du, 0x00000011u, 0x00000014u,
+        0x00030003u, 0x00000002u, 0x000001c2u, 0x00040005u, 0x00000004u, 0x6e69616du,
+        0x00000000u, 0x00060005u, 0x0000000bu, 0x505f6c67u, 0x65567265u, 0x78657472u,
+        0x00000000u, 0x00060006u, 0x0000000bu, 0x00000000u, 0x505f6c67u, 0x7469736fu,
+        0x006e6f69u, 0x00070006u, 0x0000000bu, 0x00000001u, 0x505f6c67u, 0x746e696fu,
+        0x657a6953u, 0x00000000u, 0x00070006u, 0x0000000bu, 0x00000002u, 0x435f6c67u,
+        0x4470696cu, 0x61747369u, 0x0065636eu, 0x00070006u, 0x0000000bu, 0x00000003u,
+        0x435f6c67u, 0x446c6c75u, 0x61747369u, 0x0065636eu, 0x00030005u, 0x0000000du,
+        0x00000000u, 0x00040005u, 0x00000011u, 0x6f506e69u, 0x00000073u, 0x00070005u,
+        0x00000014u, 0x495f6c67u, 0x6174736eu, 0x4965636eu, 0x7865646eu, 0x00000000u,
+        0x00030047u, 0x0000000bu, 0x00000002u, 0x00050048u, 0x0000000bu, 0x00000000u,
+        0x0000000bu, 0x00000000u, 0x00050048u, 0x0000000bu, 0x00000001u, 0x0000000bu,
+        0x00000001u, 0x00050048u, 0x0000000bu, 0x00000002u, 0x0000000bu, 0x00000003u,
+        0x00050048u, 0x0000000bu, 0x00000003u, 0x0000000bu, 0x00000004u, 0x00040047u,
+        0x00000011u, 0x0000001eu, 0x00000000u, 0x00040047u, 0x00000014u, 0x0000000bu,
+        0x0000002bu, 0x00020013u, 0x00000002u, 0x00030021u, 0x00000003u, 0x00000002u,
+        0x00030016u, 0x00000006u, 0x00000020u, 0x00040017u, 0x00000007u, 0x00000006u,
+        0x00000004u, 0x00040015u, 0x00000008u, 0x00000020u, 0x00000000u, 0x0004002bu,
+        0x00000008u, 0x00000009u, 0x00000001u, 0x0004001cu, 0x0000000au, 0x00000006u,
+        0x00000009u, 0x0006001eu, 0x0000000bu, 0x00000007u, 0x00000006u, 0x0000000au,
+        0x0000000au, 0x00040020u, 0x0000000cu, 0x00000003u, 0x0000000bu, 0x0004003bu,
+        0x0000000cu, 0x0000000du, 0x00000003u, 0x00040015u, 0x0000000eu, 0x00000020u,
+        0x00000001u, 0x0004002bu, 0x0000000eu, 0x0000000fu, 0x00000000u, 0x00040020u,
+        0x00000010u, 0x00000001u, 0x00000007u, 0x0004003bu, 0x00000010u, 0x00000011u,
+        0x00000001u, 0x00040020u, 0x00000013u, 0x00000001u, 0x0000000eu, 0x0004003bu,
+        0x00000013u, 0x00000014u, 0x00000001u, 0x00040020u, 0x00000019u, 0x00000003u,
+        0x00000007u, 0x00050036u, 0x00000002u, 0x00000004u, 0x00000000u, 0x00000003u,
+        0x000200f8u, 0x00000005u, 0x0004003du, 0x00000007u, 0x00000012u, 0x00000011u,
+        0x0004003du, 0x0000000eu, 0x00000015u, 0x00000014u, 0x0004006fu, 0x00000006u,
+        0x00000016u, 0x00000015u, 0x00070050u, 0x00000007u, 0x00000017u, 0x00000016u,
+        0x00000016u, 0x00000016u, 0x00000016u, 0x00050081u, 0x00000007u, 0x00000018u,
+        0x00000012u, 0x00000017u, 0x00050041u, 0x00000019u, 0x0000001au, 0x0000000du,
+        0x0000000fu, 0x0003003eu, 0x0000001au, 0x00000018u, 0x000100fdu, 0x00010038u,
+    };
+
+
+    // Same, but reading gl_VertexIndex instead: a DIFFERENT input builtin. glslang emits
+    // this for GL's gl_VertexID, so nearly every real vertex shader has one - it is what
+    // separates "declares some builtin" from "declares the InstanceIndex builtin".
+    constexpr Uint32 kVertexIndexVertexSpirv[] = {
+        0x07230203u, 0x00010000u, 0x0008000bu, 0x0000001bu, 0x00000000u, 0x00020011u,
+        0x00000001u, 0x0006000bu, 0x00000001u, 0x4c534c47u, 0x6474732eu, 0x3035342eu,
+        0x00000000u, 0x0003000eu, 0x00000000u, 0x00000001u, 0x0008000fu, 0x00000000u,
+        0x00000004u, 0x6e69616du, 0x00000000u, 0x0000000du, 0x00000011u, 0x00000014u,
+        0x00030003u, 0x00000002u, 0x000001c2u, 0x00040005u, 0x00000004u, 0x6e69616du,
+        0x00000000u, 0x00060005u, 0x0000000bu, 0x505f6c67u, 0x65567265u, 0x78657472u,
+        0x00000000u, 0x00060006u, 0x0000000bu, 0x00000000u, 0x505f6c67u, 0x7469736fu,
+        0x006e6f69u, 0x00070006u, 0x0000000bu, 0x00000001u, 0x505f6c67u, 0x746e696fu,
+        0x657a6953u, 0x00000000u, 0x00070006u, 0x0000000bu, 0x00000002u, 0x435f6c67u,
+        0x4470696cu, 0x61747369u, 0x0065636eu, 0x00070006u, 0x0000000bu, 0x00000003u,
+        0x435f6c67u, 0x446c6c75u, 0x61747369u, 0x0065636eu, 0x00030005u, 0x0000000du,
+        0x00000000u, 0x00040005u, 0x00000011u, 0x6f506e69u, 0x00000073u, 0x00060005u,
+        0x00000014u, 0x565f6c67u, 0x65747265u, 0x646e4978u, 0x00007865u, 0x00030047u,
+        0x0000000bu, 0x00000002u, 0x00050048u, 0x0000000bu, 0x00000000u, 0x0000000bu,
+        0x00000000u, 0x00050048u, 0x0000000bu, 0x00000001u, 0x0000000bu, 0x00000001u,
+        0x00050048u, 0x0000000bu, 0x00000002u, 0x0000000bu, 0x00000003u, 0x00050048u,
+        0x0000000bu, 0x00000003u, 0x0000000bu, 0x00000004u, 0x00040047u, 0x00000011u,
+        0x0000001eu, 0x00000000u, 0x00040047u, 0x00000014u, 0x0000000bu, 0x0000002au,
+        0x00020013u, 0x00000002u, 0x00030021u, 0x00000003u, 0x00000002u, 0x00030016u,
+        0x00000006u, 0x00000020u, 0x00040017u, 0x00000007u, 0x00000006u, 0x00000004u,
+        0x00040015u, 0x00000008u, 0x00000020u, 0x00000000u, 0x0004002bu, 0x00000008u,
+        0x00000009u, 0x00000001u, 0x0004001cu, 0x0000000au, 0x00000006u, 0x00000009u,
+        0x0006001eu, 0x0000000bu, 0x00000007u, 0x00000006u, 0x0000000au, 0x0000000au,
+        0x00040020u, 0x0000000cu, 0x00000003u, 0x0000000bu, 0x0004003bu, 0x0000000cu,
+        0x0000000du, 0x00000003u, 0x00040015u, 0x0000000eu, 0x00000020u, 0x00000001u,
+        0x0004002bu, 0x0000000eu, 0x0000000fu, 0x00000000u, 0x00040020u, 0x00000010u,
+        0x00000001u, 0x00000007u, 0x0004003bu, 0x00000010u, 0x00000011u, 0x00000001u,
+        0x00040020u, 0x00000013u, 0x00000001u, 0x0000000eu, 0x0004003bu, 0x00000013u,
+        0x00000014u, 0x00000001u, 0x00040020u, 0x00000019u, 0x00000003u, 0x00000007u,
+        0x00050036u, 0x00000002u, 0x00000004u, 0x00000000u, 0x00000003u, 0x000200f8u,
+        0x00000005u, 0x0004003du, 0x00000007u, 0x00000012u, 0x00000011u, 0x0004003du,
+        0x0000000eu, 0x00000015u, 0x00000014u, 0x0004006fu, 0x00000006u, 0x00000016u,
+        0x00000015u, 0x00070050u, 0x00000007u, 0x00000017u, 0x00000016u, 0x00000016u,
+        0x00000016u, 0x00000016u, 0x00050081u, 0x00000007u, 0x00000018u, 0x00000012u,
+        0x00000017u, 0x00050041u, 0x00000019u, 0x0000001au, 0x0000000du, 0x0000000fu,
+        0x0003003eu, 0x0000001au, 0x00000018u, 0x000100fdu, 0x00010038u,
+    };
+
     // Owns the reflection module so each test case cleans up after itself.
     class ReflectModule {
     public:
@@ -339,3 +426,31 @@ TEST(ReflectedFragmentReplacesDepth, ReflectedFlagFlipsTheStripDecision) {
     payload.fragmentReplacesDepth = ProgramFactory::ReflectedFragmentReplacesDepth(depthWriter.Get());
     EXPECT_FALSE(PipelineFactory::ShouldSuppressDepthWrite(payload));
 }
+
+
+// --- InstanceIndex reflection feeding the shaderDrawParameters diagnostic ---
+
+TEST(ReflectedReadsInstanceIndexBuiltin, TrueForAShaderReadingInstanceIndex) {
+    const ReflectModule module(kInstanceIndexVertexSpirv);
+    ASSERT_TRUE(module.Created());
+    EXPECT_TRUE(ProgramFactory::ReflectedReadsInstanceIndexBuiltin(module.Get()));
+}
+
+TEST(ReflectedReadsInstanceIndexBuiltin, FalseForAShaderReadingADifferentBuiltin) {
+    // Discriminates the builtin's identity, not merely its presence: weakening the check to
+    // "has any BuiltIn decoration" would fire the diagnostic on every real vertex shader.
+    const ReflectModule module(kVertexIndexVertexSpirv);
+    ASSERT_TRUE(module.Created());
+    EXPECT_FALSE(ProgramFactory::ReflectedReadsInstanceIndexBuiltin(module.Get()));
+}
+
+TEST(ReflectedReadsInstanceIndexBuiltin, FalseForAShaderWithNoInputBuiltins) {
+    const ReflectModule module(kPlainFragmentSpirv);
+    ASSERT_TRUE(module.Created());
+    EXPECT_FALSE(ProgramFactory::ReflectedReadsInstanceIndexBuiltin(module.Get()));
+}
+
+TEST(ReflectedReadsInstanceIndexBuiltin, FalseForAnEmptyModule) {
+    SpvReflectShaderModule emptyModule{};
+    EXPECT_FALSE(ProgramFactory::ReflectedReadsInstanceIndexBuiltin(emptyModule));
+}

MobileGL/MG_Test/ShaderTranspiler/CMakeLists.txt

@@ -0,0 +1,25 @@
+cmake_minimum_required(VERSION 3.14)
+
+add_executable(
+        SpirvPassTest
+        SpirvPassTest.cpp
+)
+
+target_include_directories(SpirvPassTest PRIVATE
+        ${MGL_ROOT}/include
+        ${MGL_ROOT}/MobileGL
+        ${MGL_ROOT}/3rdparty/SPIRV-Reflect
+)
+
+target_link_libraries(
+        SpirvPassTest PRIVATE
+        GTest::gtest_main
+        ${LINK_LIBRARIES}
+)
+
+if (MSVC)
+        target_compile_options(SpirvPassTest PRIVATE /Zc:preprocessor)
+endif()
+
+include(GoogleTest)
+gtest_discover_tests(SpirvPassTest DISCOVERY_TIMEOUT 30 PROPERTIES LABELS unit)

MobileGL/MG_Test/ShaderTranspiler/SpirvPassTest.cpp

@@ -0,0 +1,170 @@
+// MobileGL - MobileGL/MG_Test/ShaderTranspiler/SpirvPassTest.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 <gtest/gtest.h>
+
+#include <MG_Util/ShaderTranspiler/ShaderCompiler.h>
+
+#include <spirv_reflect.h>
+
+using namespace MobileGL;
+using MobileGL::MG_Util::ShaderTranspiler::ShaderCompiler;
+
+namespace {
+    // glslangValidator -V output. Both are vertex shaders writing gl_Position through
+    // the gl_PerVertex block, i.e. the Position builtin arrives as OpMemberDecorate rather
+    // than a plain OpDecorate - the shape real glslang output actually takes.
+
+    //   #version 450
+    //   layout(location = 0) in vec4 inPos;
+    //   void main() { gl_Position = inPos; }
+    constexpr Uint32 kPlainVertexSpirv[] = {
+        0x07230203u, 0x00010000u, 0x0008000bu, 0x00000015u, 0x00000000u, 0x00020011u,
+        0x00000001u, 0x0006000bu, 0x00000001u, 0x4c534c47u, 0x6474732eu, 0x3035342eu,
+        0x00000000u, 0x0003000eu, 0x00000000u, 0x00000001u, 0x0007000fu, 0x00000000u,
+        0x00000004u, 0x6e69616du, 0x00000000u, 0x0000000du, 0x00000011u, 0x00030003u,
+        0x00000002u, 0x000001c2u, 0x00040005u, 0x00000004u, 0x6e69616du, 0x00000000u,
+        0x00060005u, 0x0000000bu, 0x505f6c67u, 0x65567265u, 0x78657472u, 0x00000000u,
+        0x00060006u, 0x0000000bu, 0x00000000u, 0x505f6c67u, 0x7469736fu, 0x006e6f69u,
+        0x00070006u, 0x0000000bu, 0x00000001u, 0x505f6c67u, 0x746e696fu, 0x657a6953u,
+        0x00000000u, 0x00070006u, 0x0000000bu, 0x00000002u, 0x435f6c67u, 0x4470696cu,
+        0x61747369u, 0x0065636eu, 0x00070006u, 0x0000000bu, 0x00000003u, 0x435f6c67u,
+        0x446c6c75u, 0x61747369u, 0x0065636eu, 0x00030005u, 0x0000000du, 0x00000000u,
+        0x00040005u, 0x00000011u, 0x6f506e69u, 0x00000073u, 0x00030047u, 0x0000000bu,
+        0x00000002u, 0x00050048u, 0x0000000bu, 0x00000000u, 0x0000000bu, 0x00000000u,
+        0x00050048u, 0x0000000bu, 0x00000001u, 0x0000000bu, 0x00000001u, 0x00050048u,
+        0x0000000bu, 0x00000002u, 0x0000000bu, 0x00000003u, 0x00050048u, 0x0000000bu,
+        0x00000003u, 0x0000000bu, 0x00000004u, 0x00040047u, 0x00000011u, 0x0000001eu,
+        0x00000000u, 0x00020013u, 0x00000002u, 0x00030021u, 0x00000003u, 0x00000002u,
+        0x00030016u, 0x00000006u, 0x00000020u, 0x00040017u, 0x00000007u, 0x00000006u,
+        0x00000004u, 0x00040015u, 0x00000008u, 0x00000020u, 0x00000000u, 0x0004002bu,
+        0x00000008u, 0x00000009u, 0x00000001u, 0x0004001cu, 0x0000000au, 0x00000006u,
+        0x00000009u, 0x0006001eu, 0x0000000bu, 0x00000007u, 0x00000006u, 0x0000000au,
+        0x0000000au, 0x00040020u, 0x0000000cu, 0x00000003u, 0x0000000bu, 0x0004003bu,
+        0x0000000cu, 0x0000000du, 0x00000003u, 0x00040015u, 0x0000000eu, 0x00000020u,
+        0x00000001u, 0x0004002bu, 0x0000000eu, 0x0000000fu, 0x00000000u, 0x00040020u,
+        0x00000010u, 0x00000001u, 0x00000007u, 0x0004003bu, 0x00000010u, 0x00000011u,
+        0x00000001u, 0x00040020u, 0x00000013u, 0x00000003u, 0x00000007u, 0x00050036u,
+        0x00000002u, 0x00000004u, 0x00000000u, 0x00000003u, 0x000200f8u, 0x00000005u,
+        0x0004003du, 0x00000007u, 0x00000012u, 0x00000011u, 0x00050041u, 0x00000013u,
+        0x00000014u, 0x0000000du, 0x0000000fu, 0x0003003eu, 0x00000014u, 0x00000012u,
+        0x000100fdu, 0x00010038u,
+    };
+
+    //   ... plus `invariant gl_Position;` - already carries OpMemberDecorate %gl_PerVertex 0
+    //   Invariant, so the pass must not add a duplicate.
+    constexpr Uint32 kAlreadyInvariantVertexSpirv[] = {
+        0x07230203u, 0x00010000u, 0x0008000bu, 0x00000015u, 0x00000000u, 0x00020011u,
+        0x00000001u, 0x0006000bu, 0x00000001u, 0x4c534c47u, 0x6474732eu, 0x3035342eu,
+        0x00000000u, 0x0003000eu, 0x00000000u, 0x00000001u, 0x0007000fu, 0x00000000u,
+        0x00000004u, 0x6e69616du, 0x00000000u, 0x0000000du, 0x00000011u, 0x00030003u,
+        0x00000002u, 0x000001c2u, 0x00040005u, 0x00000004u, 0x6e69616du, 0x00000000u,
+        0x00060005u, 0x0000000bu, 0x505f6c67u, 0x65567265u, 0x78657472u, 0x00000000u,
+        0x00060006u, 0x0000000bu, 0x00000000u, 0x505f6c67u, 0x7469736fu, 0x006e6f69u,
+        0x00070006u, 0x0000000bu, 0x00000001u, 0x505f6c67u, 0x746e696fu, 0x657a6953u,
+        0x00000000u, 0x00070006u, 0x0000000bu, 0x00000002u, 0x435f6c67u, 0x4470696cu,
+        0x61747369u, 0x0065636eu, 0x00070006u, 0x0000000bu, 0x00000003u, 0x435f6c67u,
+        0x446c6c75u, 0x61747369u, 0x0065636eu, 0x00030005u, 0x0000000du, 0x00000000u,
+        0x00040005u, 0x00000011u, 0x6f506e69u, 0x00000073u, 0x00030047u, 0x0000000bu,
+        0x00000002u, 0x00050048u, 0x0000000bu, 0x00000000u, 0x0000000bu, 0x00000000u,
+        0x00040048u, 0x0000000bu, 0x00000000u, 0x00000012u, 0x00050048u, 0x0000000bu,
+        0x00000001u, 0x0000000bu, 0x00000001u, 0x00050048u, 0x0000000bu, 0x00000002u,
+        0x0000000bu, 0x00000003u, 0x00050048u, 0x0000000bu, 0x00000003u, 0x0000000bu,
+        0x00000004u, 0x00040047u, 0x00000011u, 0x0000001eu, 0x00000000u, 0x00020013u,
+        0x00000002u, 0x00030021u, 0x00000003u, 0x00000002u, 0x00030016u, 0x00000006u,
+        0x00000020u, 0x00040017u, 0x00000007u, 0x00000006u, 0x00000004u, 0x00040015u,
+        0x00000008u, 0x00000020u, 0x00000000u, 0x0004002bu, 0x00000008u, 0x00000009u,
+        0x00000001u, 0x0004001cu, 0x0000000au, 0x00000006u, 0x00000009u, 0x0006001eu,
+        0x0000000bu, 0x00000007u, 0x00000006u, 0x0000000au, 0x0000000au, 0x00040020u,
+        0x0000000cu, 0x00000003u, 0x0000000bu, 0x0004003bu, 0x0000000cu, 0x0000000du,
+        0x00000003u, 0x00040015u, 0x0000000eu, 0x00000020u, 0x00000001u, 0x0004002bu,
+        0x0000000eu, 0x0000000fu, 0x00000000u, 0x00040020u, 0x00000010u, 0x00000001u,
+        0x00000007u, 0x0004003bu, 0x00000010u, 0x00000011u, 0x00000001u, 0x00040020u,
+        0x00000013u, 0x00000003u, 0x00000007u, 0x00050036u, 0x00000002u, 0x00000004u,
+        0x00000000u, 0x00000003u, 0x000200f8u, 0x00000005u, 0x0004003du, 0x00000007u,
+        0x00000012u, 0x00000011u, 0x00050041u, 0x00000013u, 0x00000014u, 0x0000000du,
+        0x0000000fu, 0x0003003eu, 0x00000014u, 0x00000012u, 0x000100fdu, 0x00010038u,
+    };
+
+    // OpMemberDecorate <struct-id> <member> <decoration>
+    constexpr Uint32 kOpMemberDecorate = 72;
+    constexpr Uint32 kDecorationInvariant = 18;
+    constexpr Uint32 kSpirvHeaderWordCount = 5;
+
+    // Test-side reference walker. Deliberately independent of the production code so a bug in
+    // the pass cannot hide behind the same helper; only used to count what the pass emitted.
+    Uint32 CountInvariantMemberDecorations(const Vector<Uint32>& spirv) {
+        Uint32 count = 0;
+        for (SizeT i = kSpirvHeaderWordCount; i < spirv.size();) {
+            const Uint32 wordCount = spirv[i] >> 16;
+            const Uint32 opcode = spirv[i] & 0xFFFFu;
+            if (wordCount == 0 || i + wordCount > spirv.size()) {
+                break;
+            }
+            if (opcode == kOpMemberDecorate && wordCount >= 4 && spirv[i + 3] == kDecorationInvariant) {
+                ++count;
+            }
+            i += wordCount;
+        }
+        return count;
+    }
+
+    template <SizeT WordCount>
+    Vector<Uint32> ToVector(const Uint32 (&words)[WordCount]) {
+        return Vector<Uint32>(words, words + WordCount);
+    }
+} // namespace
+
+// --- DecoratePositionInvariantPass ---
+
+TEST(DecoratePositionInvariant, AddsInvariantToThePositionMember) {
+    const Vector<Uint32> input = ToVector(kPlainVertexSpirv);
+    ASSERT_EQ(CountInvariantMemberDecorations(input), 0u);
+
+    Vector<Uint32> output;
+    ASSERT_TRUE(ShaderCompiler::DecoratePositionInvariantForVulkan(input, output));
+    EXPECT_EQ(CountInvariantMemberDecorations(output), 1u);
+}
+
+TEST(DecoratePositionInvariant, DoesNotDuplicateAnExistingInvariant) {
+    const Vector<Uint32> input = ToVector(kAlreadyInvariantVertexSpirv);
+    ASSERT_EQ(CountInvariantMemberDecorations(input), 1u);
+
+    Vector<Uint32> output;
+    ASSERT_TRUE(ShaderCompiler::DecoratePositionInvariantForVulkan(input, output));
+    EXPECT_EQ(CountInvariantMemberDecorations(output), 1u);
+    // The pass reports SuccessWithoutChange here, and SPIRV-Tools asserts (in assert-enabled
+    // builds) that such a run round-trips byte-identically. Pin that from the outside so an
+    // assert-enabled CI build cannot be the first thing to discover a violation.
+    EXPECT_EQ(output, input);
+}
+
+TEST(DecoratePositionInvariant, IsIdempotent) {
+    Vector<Uint32> once;
+    ASSERT_TRUE(ShaderCompiler::DecoratePositionInvariantForVulkan(ToVector(kPlainVertexSpirv), once));
+    Vector<Uint32> twice;
+    ASSERT_TRUE(ShaderCompiler::DecoratePositionInvariantForVulkan(once, twice));
+    EXPECT_EQ(CountInvariantMemberDecorations(twice), 1u);
+}
+
+TEST(DecoratePositionInvariant, OutputStaysAReflectableModule) {
+    Vector<Uint32> output;
+    ASSERT_TRUE(ShaderCompiler::DecoratePositionInvariantForVulkan(ToVector(kPlainVertexSpirv), output));
+
+    SpvReflectShaderModule module{};
+    ASSERT_EQ(spvReflectCreateShaderModule(output.size() * sizeof(Uint32), output.data(), &module),
+              SPV_REFLECT_RESULT_SUCCESS);
+    EXPECT_EQ(module.entry_point_count, 1u);
+    spvReflectDestroyShaderModule(&module);
+}
+
+TEST(DecoratePositionInvariant, RejectsGarbageInput) {
+    const Vector<Uint32> notSpirv{0xdeadbeefu, 0u, 0u, 0u, 0u};
+    Vector<Uint32> output;
+    EXPECT_FALSE(ShaderCompiler::DecoratePositionInvariantForVulkan(notSpirv, output));
+}

MobileGL/MG_Test/Texture/TextureTest.cpp

@@ -1427,6 +1427,95 @@ TEST_F(TextureTest, TextureStorage1DAndSubImageModifyNamedObjectOnly) {
     EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
 }
 
+// Building a mip chain top-down - upload level N, then level 0 - must not destroy the levels
+// already uploaded. AllocateLevel used to resize() the storage down to level+1 on every call, so
+// the level-0 upload truncated the chain to a single level; the higher level then read back as
+// {0,0,0}, IsComplete() rejected the zero-then-nonzero pattern, and DirectGLES answered that by
+// skipping the texture's sync entirely. This is the shape KHR-GL33.texture_repeat_mode uses, and
+// it accounted for 108 CTS failures in every GL version.
+TEST_F(TextureTest, TexImage2DOnLevelZeroKeepsAnAlreadyUploadedHigherLevel) {
+    GLuint texture = 0;
+    MG_Impl::GLImpl::GenTextures(1, &texture);
+    MG_Impl::GLImpl::BindTexture(GL_TEXTURE_2D, texture);
+
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 1, GL_RGBA8, 49, 23, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 98, 46, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+
+    const auto textureObject = MG_State::pGLContext->GetTextureObject(texture);
+    auto* mipmapObject = static_cast<MG_State::GLState::TextureObjectMipmap*>(textureObject.get());
+    ASSERT_NE(mipmapObject, nullptr);
+    EXPECT_EQ(mipmapObject->GetMipmapLevelCount(), 2u);
+    EXPECT_EQ(mipmapObject->GetMipmapTexelSize(TextureUploadTarget::Texture2D, 0), IntVec3(98, 46, 1));
+    EXPECT_EQ(mipmapObject->GetMipmapTexelSize(TextureUploadTarget::Texture2D, 1), IntVec3(49, 23, 1));
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+}
+
+// The other half of the contract: respecifying a level 0 that already held an image still drops
+// the chain, exactly as before. Minecraft rebinds the block-atlas name and calls glTexImage2D on
+// level 0 before uploading the new levels; leaving the previous chain in place would strand a tail
+// at the wrong sizes and - because Mojang terminates its chains with a 0x0 level - reproduce the
+// same incomplete-texture black atlas the fix above exists to prevent.
+TEST_F(TextureTest, TexImage2DRespecifyingAnExistingLevelZeroDropsTheStaleChain) {
+    GLuint texture = 0;
+    MG_Impl::GLImpl::GenTextures(1, &texture);
+    MG_Impl::GLImpl::BindTexture(GL_TEXTURE_2D, texture);
+
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 8, 8, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 1, GL_RGBA8, 4, 4, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 2, GL_RGBA8, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+
+    const auto textureObject = MG_State::pGLContext->GetTextureObject(texture);
+    auto* mipmapObject = static_cast<MG_State::GLState::TextureObjectMipmap*>(textureObject.get());
+    ASSERT_NE(mipmapObject, nullptr);
+    ASSERT_EQ(mipmapObject->GetMipmapLevelCount(), 3u);
+
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 16, 16, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+
+    EXPECT_EQ(mipmapObject->GetMipmapLevelCount(), 1u);
+    EXPECT_EQ(mipmapObject->GetMipmapTexelSize(TextureUploadTarget::Texture2D, 0), IntVec3(16, 16, 1));
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+}
+
+// Same-size respecification has to drop the chain too. The Mipmap Levels video setting rebuilds
+// the atlas at identical dimensions with a different level count, so a size-change-only test would
+// let the old tail survive.
+TEST_F(TextureTest, TexImage2DRespecifyingLevelZeroAtTheSameSizeStillDropsTheChain) {
+    GLuint texture = 0;
+    MG_Impl::GLImpl::GenTextures(1, &texture);
+    MG_Impl::GLImpl::BindTexture(GL_TEXTURE_2D, texture);
+
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 8, 8, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 1, GL_RGBA8, 4, 4, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 8, 8, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+
+    const auto textureObject = MG_State::pGLContext->GetTextureObject(texture);
+    auto* mipmapObject = static_cast<MG_State::GLState::TextureObjectMipmap*>(textureObject.get());
+    ASSERT_NE(mipmapObject, nullptr);
+    EXPECT_EQ(mipmapObject->GetMipmapLevelCount(), 1u);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+}
+
+// glTexStorage2D defines exactly `levels` levels. AllocateStorage only grows now, so the immutable
+// path has to drop a longer pre-existing chain explicitly.
+TEST_F(TextureTest, TexStorage2DTrimsALongerPreExistingMipChain) {
+    GLuint texture = 0;
+    MG_Impl::GLImpl::GenTextures(1, &texture);
+    MG_Impl::GLImpl::BindTexture(GL_TEXTURE_2D, texture);
+
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 8, 8, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 1, GL_RGBA8, 4, 4, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 2, GL_RGBA8, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    MG_Impl::GLImpl::TexImage2D(GL_TEXTURE_2D, 3, GL_RGBA8, 1, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+
+    MG_Impl::GLImpl::TexStorage2D(GL_TEXTURE_2D, 2, GL_RGBA8, 8, 8);
+
+    const auto textureObject = MG_State::pGLContext->GetTextureObject(texture);
+    auto* mipmapObject = static_cast<MG_State::GLState::TextureObjectMipmap*>(textureObject.get());
+    ASSERT_NE(mipmapObject, nullptr);
+    EXPECT_EQ(mipmapObject->GetMipmapLevelCount(), 2u);
+    EXPECT_EQ(MG_Impl::GLImpl::GetError(), GL_NO_ERROR);
+}
+
 // glTexImage2D used to reject every GL_COMPRESSED_* internal format with GL_INVALID_ENUM, because
 // none of them mapped to a TextureInternalFormat and the "unknown format" gate fired. They now
 // resolve to the uncompressed storage that backs them - what GL prescribes for the generic formats,

MobileGL/MG_Util/ShaderTranspiler/ShaderCompiler.cpp

@@ -16,6 +16,7 @@
 #include "SpirvPasses/FlattenInterfaceStructPass.h"
 #include "SpirvPasses/RenameSamplerFunctionParameterPass.h"
 #include "SpirvPasses/DecomposeWorkgroupVec3Pass.h"
+#include "SpirvPasses/DecoratePositionInvariantPass.h"
 #include "SpirvPasses/LowerDrawParametersPass.h"
 #include "SpirvPasses/RebaseInstanceIndexPass.h"
 #include "SpirvPasses/StripUboMemberRelaxedPrecisionPass.h"
@@ -347,71 +348,14 @@ namespace MobileGL {
 
             bool ShaderCompiler::DecoratePositionInvariantForVulkan(const Vector<Uint32>& inputBinary,
                                                                     Vector<uint32_t>& outputBinary) {
-                static constexpr Uint32 kHeaderWords = 5;
+                using namespace spvtools;
-                static constexpr Uint32 kOpDecorate = 71;
+                OptimizerOptions options;
-                static constexpr Uint32 kOpMemberDecorate = 72;
+                options.set_run_validator(false);
-                static constexpr Uint32 kDecorationInvariant = 18;
-                static constexpr Uint32 kDecorationBuiltIn = 11;
-                static constexpr Uint32 kBuiltInPosition = 0;
-                if (inputBinary.size() < kHeaderWords) {
-                    return false;
-                }
 
-                // First pass: find targets that already carry Invariant so we never duplicate.
+                Optimizer optimizer(SPV_ENV_VULKAN_1_1);
-                struct MemberKey {
+                optimizer.RegisterPass(DecoratePositionInvariantPass::CreateDecoratePositionInvariantPass());
-                    Uint32 id;
-                    Uint32 member;
-                    bool operator==(const MemberKey& o) const { return id == o.id && member == o.member; }
-                };
-                Vector<Uint32> invariantIds;
-                Vector<MemberKey> invariantMembers;
-                for (SizeT i = kHeaderWords; i < inputBinary.size();) {
-                    const Uint32 word0 = inputBinary[i];
-                    const Uint32 opcode = word0 & 0xFFFFu;
-                    const Uint32 length = word0 >> 16;
-                    if (length == 0 || i + length > inputBinary.size()) {
-                        return false;
-                    }
-                    if (opcode == kOpDecorate && length >= 3 && inputBinary[i + 2] == kDecorationInvariant) {
-                        invariantIds.push_back(inputBinary[i + 1]);
-                    } else if (opcode == kOpMemberDecorate && length >= 4 &&
-                               inputBinary[i + 3] == kDecorationInvariant) {
-                        invariantMembers.push_back({inputBinary[i + 1], inputBinary[i + 2]});
-                    }
-                    i += length;
-                }
 
-                outputBinary.clear();
+                return optimizer.Run(inputBinary.data(), inputBinary.size(), &outputBinary, options);
-                outputBinary.reserve(inputBinary.size() + 8);
-                outputBinary.insert(outputBinary.end(), inputBinary.begin(), inputBinary.begin() + kHeaderWords);
-                for (SizeT i = kHeaderWords; i < inputBinary.size();) {
-                    const Uint32 word0 = inputBinary[i];
-                    const Uint32 opcode = word0 & 0xFFFFu;
-                    const Uint32 length = word0 >> 16;
-                    outputBinary.insert(outputBinary.end(), inputBinary.begin() + i,
-                                        inputBinary.begin() + i + length);
-                    if (opcode == kOpDecorate && length == 4 &&
-                        inputBinary[i + 2] == kDecorationBuiltIn && inputBinary[i + 3] == kBuiltInPosition) {
-                        const Uint32 target = inputBinary[i + 1];
-                        if (std::find(invariantIds.begin(), invariantIds.end(), target) == invariantIds.end()) {
-                            outputBinary.push_back((3u << 16) | kOpDecorate);
-                            outputBinary.push_back(target);
-                            outputBinary.push_back(kDecorationInvariant);
-                        }
-                    } else if (opcode == kOpMemberDecorate && length == 5 &&
-                               inputBinary[i + 3] == kDecorationBuiltIn && inputBinary[i + 4] == kBuiltInPosition) {
-                        const MemberKey key{inputBinary[i + 1], inputBinary[i + 2]};
-                        if (std::find(invariantMembers.begin(), invariantMembers.end(), key) ==
-                            invariantMembers.end()) {
-                            outputBinary.push_back((4u << 16) | kOpMemberDecorate);
-                            outputBinary.push_back(key.id);
-                            outputBinary.push_back(key.member);
-                            outputBinary.push_back(kDecorationInvariant);
-                        }
-                    }
-                    i += length;
-                }
-                return true;
             }
 
             bool ShaderCompiler::UseUnformattedFloatStorageImagesForVulkan(

MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/DecoratePositionInvariantPass.cpp

@@ -0,0 +1,139 @@
+// MobileGL - MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/DecoratePositionInvariantPass.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 "DecoratePositionInvariantPass.h"
+
+#include "spirv.hpp"
+#include "source/opt/instruction.h"
+#include "source/opt/ir_context.h"
+#include "source/util/make_unique.h"
+
+#include <algorithm>
+#include <vector>
+
+namespace MobileGL {
+    namespace MG_Util {
+        namespace ShaderTranspiler {
+            namespace {
+                using spvtools::opt::Instruction;
+                using spvtools::opt::IRContext;
+                using spvtools::opt::Operand;
+
+                // Identifies one member of a decorated struct (gl_PerVertex's Position slot).
+                struct MemberKey {
+                    uint32_t id = 0;
+                    uint32_t member = 0;
+                    bool operator==(const MemberKey& other) const {
+                        return id == other.id && member == other.member;
+                    }
+                };
+
+                // OpDecorate      <target-id> <decoration> [literals...]
+                // OpMemberDecorate <struct-id> <member> <decoration> [literals...]
+                constexpr uint32_t kDecorateTargetOperand = 0;
+                constexpr uint32_t kDecorateDecorationOperand = 1;
+                constexpr uint32_t kDecorateBuiltInOperand = 2;
+                constexpr uint32_t kMemberDecorateStructOperand = 0;
+                constexpr uint32_t kMemberDecorateMemberOperand = 1;
+                constexpr uint32_t kMemberDecorateDecorationOperand = 2;
+                constexpr uint32_t kMemberDecorateBuiltInOperand = 3;
+            } // namespace
+
+            spvtools::opt::Pass::Status DecoratePositionInvariantPass::Process() {
+                auto* irContext = context();
+
+                // Collect first: AddAnnotationInst mutates the list being walked.
+                std::vector<uint32_t> invariantIds;
+                std::vector<MemberKey> invariantMembers;
+                std::vector<uint32_t> positionIds;
+                std::vector<MemberKey> positionMembers;
+
+                for (const Instruction& annotation : irContext->annotations()) {
+                    if (annotation.opcode() == spv::Op::OpDecorate) {
+                        if (annotation.NumInOperands() <= kDecorateDecorationOperand) {
+                            continue;
+                        }
+                        const auto decoration = static_cast<spv::Decoration>(
+                            annotation.GetSingleWordInOperand(kDecorateDecorationOperand));
+                        const uint32_t target = annotation.GetSingleWordInOperand(kDecorateTargetOperand);
+                        if (decoration == spv::Decoration::Invariant) {
+                            invariantIds.push_back(target);
+                        } else if (decoration == spv::Decoration::BuiltIn &&
+                                   annotation.NumInOperands() > kDecorateBuiltInOperand &&
+                                   static_cast<spv::BuiltIn>(annotation.GetSingleWordInOperand(
+                                       kDecorateBuiltInOperand)) == spv::BuiltIn::Position) {
+                            positionIds.push_back(target);
+                        }
+                    } else if (annotation.opcode() == spv::Op::OpMemberDecorate) {
+                        if (annotation.NumInOperands() <= kMemberDecorateDecorationOperand) {
+                            continue;
+                        }
+                        const auto decoration = static_cast<spv::Decoration>(
+                            annotation.GetSingleWordInOperand(kMemberDecorateDecorationOperand));
+                        const MemberKey key{
+                            annotation.GetSingleWordInOperand(kMemberDecorateStructOperand),
+                            annotation.GetSingleWordInOperand(kMemberDecorateMemberOperand)};
+                        if (decoration == spv::Decoration::Invariant) {
+                            invariantMembers.push_back(key);
+                        } else if (decoration == spv::Decoration::BuiltIn &&
+                                   annotation.NumInOperands() > kMemberDecorateBuiltInOperand &&
+                                   static_cast<spv::BuiltIn>(annotation.GetSingleWordInOperand(
+                                       kMemberDecorateBuiltInOperand)) == spv::BuiltIn::Position) {
+                            positionMembers.push_back(key);
+                        }
+                    }
+                }
+
+                Bool changed = false;
+
+                for (const uint32_t target : positionIds) {
+                    if (std::find(invariantIds.begin(), invariantIds.end(), target) != invariantIds.end()) {
+                        continue;
+                    }
+                    irContext->AddAnnotationInst(spvtools::MakeUnique<Instruction>(
+                        irContext, spv::Op::OpDecorate, 0, 0,
+                        std::initializer_list<Operand>{
+                            {SPV_OPERAND_TYPE_ID, {target}},
+                            {SPV_OPERAND_TYPE_DECORATION,
+                             {static_cast<uint32_t>(spv::Decoration::Invariant)}}}));
+                    // Guard against a second Position decoration on the same target.
+                    invariantIds.push_back(target);
+                    changed = true;
+                }
+
+                for (const MemberKey& key : positionMembers) {
+                    if (std::find(invariantMembers.begin(), invariantMembers.end(), key) !=
+                        invariantMembers.end()) {
+                        continue;
+                    }
+                    irContext->AddAnnotationInst(spvtools::MakeUnique<Instruction>(
+                        irContext, spv::Op::OpMemberDecorate, 0, 0,
+                        std::initializer_list<Operand>{
+                            {SPV_OPERAND_TYPE_ID, {key.id}},
+                            {SPV_OPERAND_TYPE_LITERAL_INTEGER, {key.member}},
+                            {SPV_OPERAND_TYPE_DECORATION,
+                             {static_cast<uint32_t>(spv::Decoration::Invariant)}}}));
+                    invariantMembers.push_back(key);
+                    changed = true;
+                }
+
+                if (!changed) {
+                    return Status::SuccessWithoutChange;
+                }
+
+                irContext->InvalidateAnalysesExceptFor(IRContext::kAnalysisNone);
+                return Status::SuccessWithChange;
+            }
+
+            spvtools::Optimizer::PassToken
+            DecoratePositionInvariantPass::CreateDecoratePositionInvariantPass() {
+                return spvtools::Optimizer::PassToken(MakeUnique<DecoratePositionInvariantPass>());
+            }
+        } // namespace ShaderTranspiler
+    } // namespace MG_Util
+} // namespace MobileGL

MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/DecoratePositionInvariantPass.h

@@ -0,0 +1,35 @@
+// MobileGL - MobileGL/MG_Util/ShaderTranspiler/SpirvPasses/DecoratePositionInvariantPass.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 "source/opt/pass.h"
+#include "spirv-tools/optimizer.hpp"
+
+#include <Includes.h>
+
+namespace MobileGL {
+    namespace MG_Util {
+        namespace ShaderTranspiler {
+            // Adds the Invariant decoration to every Position builtin output. GL apps
+            // routinely rely on cross-program position invariance for multi-pass equality
+            // depth tests - MC 26.3's OIT re-draws the cloud geometry with GEQUAL against the
+            // depth its own first pass wrote - and a driver that optimizes each pipeline
+            // separately may otherwise vary the position math between passes, dropping whole
+            // primitives from the later ones. Both the plain (OpDecorate on a Position
+            // variable) and the block-member (OpMemberDecorate on gl_PerVertex) spellings are
+            // handled; targets that already carry Invariant are left alone. DirectVulkan only.
+            class DecoratePositionInvariantPass : public spvtools::opt::Pass {
+            public:
+                const char* name() const override { return "decorate-position-invariant"; }
+                Status Process() override;
+
+                static spvtools::Optimizer::PassToken CreateDecoratePositionInvariantPass();
+            };
+        } // namespace ShaderTranspiler
+    } // namespace MG_Util
+} // namespace MobileGL