[Fix] (MG_Backend/DirectVulkan): key the sampled-set walk-skip on a program lifetime id, not the recyclable GL name, so a deleted+recreated program can't false-hit the cache

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.cpp

@@ -3406,11 +3406,11 @@ void main() {
         // elides re-resolving *which* textures are sampled, never their layout handling.
         auto& sampledTextures = m_sampledTexturesScratch;
         {
-            const Uint programIndex = program.GetExternalIndex();
+            const Uint64 programLifetimeId = program.GetLifetimeId();
             const Uint32 programVersion = program.GetBackendStateVersion();
             const Uint64 bindGeneration = MG_State::pGLContext->GetTextureBindGeneration();
             const Bool sampledSetUnchanged =
-                m_lastSampledSetValid && m_lastSampledSetProgramIndex == programIndex &&
+                m_lastSampledSetValid && m_lastSampledSetProgramLifetimeId == programLifetimeId &&
                 m_lastSampledSetProgramVersion == programVersion &&
                 m_lastSampledSetTransformFlags == transformFlags &&
                 m_lastSampledSetBindGeneration == bindGeneration;
@@ -3419,7 +3419,7 @@ void main() {
                     m_uniformManager->CollectSampledTextures(program, programObj, sampledTextures);
                 MOBILEGL_ASSERT(hasSampledTextures, "%s: CollectSampledTextures failed", __func__);
                 m_lastSampledSetValid = true;
-                m_lastSampledSetProgramIndex = programIndex;
+                m_lastSampledSetProgramLifetimeId = programLifetimeId;
                 m_lastSampledSetProgramVersion = programVersion;
                 m_lastSampledSetTransformFlags = transformFlags;
                 m_lastSampledSetBindGeneration = bindGeneration;

MobileGL/MG_Backend/DirectVulkan/Renderer/VulkanRenderer.h

@@ -404,15 +404,16 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         Vector<DeferredDepthMipmapCleanup> m_deferredDepthMipmapCleanup;
 
         // Skip the per-draw CollectSampledTextures walk (~5% of the render thread) when the sampled
-        // texture SET is provably unchanged from the previous draw: same program (external index +
+        // texture SET is provably unchanged from the previous draw: same program (lifetime id +
         // backend-state version, which covers sampler-uniform reassignment / relink) and transform
         // flags, and no texture bind/unbind/delete since (GetTextureBindGeneration). On a hit,
         // m_sampledTexturesScratch still holds the previous draw's list and steps 2-4 (feedback /
         // layout probe / transition) re-run on it, so layout correctness is unaffected - only the GL
-        // walk is skipped. Reset per command-buffer recording so a reused program/FBO address can't
-        // outlive a frame.
+        // walk is skipped. The program lifetime id (never reused, unlike the GL name) and the
+        // monotonic bind generation make the key ABA-proof; the per-command-buffer reset is a cheap
+        // belt-and-suspenders.
         Bool m_lastSampledSetValid = false;
-        Uint m_lastSampledSetProgramIndex = 0;
+        Uint64 m_lastSampledSetProgramLifetimeId = 0;
         Uint32 m_lastSampledSetProgramVersion = 0;
         ProgramFactory::CompileOptionFlags m_lastSampledSetTransformFlags = {};
         Uint64 m_lastSampledSetBindGeneration = 0;

MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp

@@ -7,6 +7,7 @@
 // End of Source File Header
 
 #include "ProgramObject.h"
+#include <atomic>
 #include <MG_Backend/BackendObjects.h>
 #include <MG_State/GLState/VertexArrayState/VertexArrayObject.h>
 #include <MG_Util/Converters/GLToStr/GLEnumConverter.h>
@@ -122,6 +123,12 @@ namespace {
 }
 
 namespace MobileGL::MG_State::GLState {
+    static std::atomic<Uint64> s_nextProgramLifetimeId = 1;
+
+    Uint64 ProgramObject::AllocateLifetimeId() {
+        return s_nextProgramLifetimeId.fetch_add(1, std::memory_order_relaxed);
+    }
+
     void ProgramObject::ResetLinkArtifacts() {
         // Relinking regenerates the SPIR-V, so any backend-cached state keyed on
         // m_backendStateVersion (e.g. the content-hash memo) must be invalidated,

MobileGL/MG_State/GLState/ProgramState/ProgramObject.h

@@ -16,7 +16,7 @@
 namespace MobileGL::MG_State::GLState {
     class ProgramObject {
     public:
-        ProgramObject(Uint externalIndex) : m_externalIndex(externalIndex) {}
+        ProgramObject(Uint externalIndex) : m_externalIndex(externalIndex), m_lifetimeId(AllocateLifetimeId()) {}
         bool ShaderIsAttached(const SharedPtr<ShaderObject>& shader);
         bool AttachShader(const SharedPtr<ShaderObject>& shader);
         SizeT DetachShader(const SharedPtr<ShaderObject>& shader);
@@ -340,6 +340,11 @@ namespace MobileGL::MG_State::GLState {
         }
 
         Uint GetExternalIndex() const { return m_externalIndex; }
+        // Globally-unique, never-reused id for this program object's lifetime. Unlike the GL
+        // name (external index), which is freed to a LIFO list and immediately handed back by
+        // the next glCreateProgram, this distinguishes a deleted-and-recreated program from the
+        // original, so an identity cache can't false-hit on name recycling.
+        Uint64 GetLifetimeId() const { return m_lifetimeId; }
 
     private:
         void ResetLinkArtifacts();
@@ -349,7 +354,10 @@ namespace MobileGL::MG_State::GLState {
         void AddDefaultFragmentShaderIfMissing();
         Bool ValidateFragmentOutputLocations();
 
+        static Uint64 AllocateLifetimeId();
+
         const Uint m_externalIndex = 0;
+        const Uint64 m_lifetimeId = 0;
         Vector<SharedPtr<ShaderObject>> m_shaders;
         Vector<SharedPtr<ShaderObject>> m_detachedShaders; // Store detached shaders and remove on next link