Fix Area Lights PBR crash: split sampler2D function parameters

CMakeLists.txt

@@ -65,7 +65,7 @@ FetchContent_Declare(metal-cpp
     EXCLUDE_FROM_ALL)
 FetchContent_Declare(SPIRV-Cross
     GIT_REPOSITORY https://github.com/BabylonJS/SPIRV-Cross.git
-    GIT_TAG 866e5edcc3407997a3ed62f3edf492f91bcb2629
+    GIT_TAG a512817ddbcd879a3929aef7d1d762871bdf8635
     EXCLUDE_FROM_ALL)
 
 # --------------------------------------------------

Plugins/ShaderCompiler/Source/ShaderCompilerDXBC.cpp

@@ -107,6 +107,7 @@ namespace Babylon::Plugins
         std::map<std::string, std::string> vertexAttributeRenaming = {};
         ShaderCompilerTraversers::AssignLocationsAndNamesToVertexVaryingsD3D(program, ids, vertexAttributeRenaming);
         ShaderCompilerTraversers::SplitSamplersIntoSamplersAndTextures(program, ids);
+        ShaderCompilerTraversers::SplitSamplerFunctionParameters(program, ids);
         ShaderCompilerTraversers::InvertYDerivativeOperands(program);
 
         // clang-format off

Plugins/ShaderCompiler/Source/ShaderCompilerDXIL.cpp

@@ -183,6 +183,7 @@ namespace Babylon::Plugins
         std::map<std::string, std::string> vertexAttributeRenaming = {};
         ShaderCompilerTraversers::AssignLocationsAndNamesToVertexVaryingsD3D(program, ids, vertexAttributeRenaming);
         ShaderCompilerTraversers::SplitSamplersIntoSamplersAndTextures(program, ids);
+        ShaderCompilerTraversers::SplitSamplerFunctionParameters(program, ids);
         ShaderCompilerTraversers::InvertYDerivativeOperands(program);
 
         // clang-format off

Plugins/ShaderCompiler/Source/ShaderCompilerMetal.cpp

@@ -108,6 +108,7 @@ namespace Babylon::Plugins
         std::map<std::string, std::string> vertexAttributeRenaming = {};
         ShaderCompilerTraversers::AssignLocationsAndNamesToVertexVaryingsMetal(program, ids, vertexAttributeRenaming);
         ShaderCompilerTraversers::SplitSamplersIntoSamplersAndTextures(program, ids);
+        ShaderCompilerTraversers::SplitSamplerFunctionParameters(program, ids);
         ShaderCompilerTraversers::InvertYDerivativeOperands(program);
 
         std::string vertexMSL(vertexSource.data(), vertexSource.size());

Plugins/ShaderCompiler/Source/ShaderCompilerTraversers.h

@@ -78,6 +78,32 @@ namespace Babylon::ShaderCompilerTraversers
     /// the expectations of native platforms.
     void SplitSamplersIntoSamplersAndTextures(glslang::TProgram& program, IdGenerator& ids);
 
+    /// Split combined `sampler2D`/`samplerCube`/etc. function parameters of user-defined
+    /// functions into separate texture and sampler parameters. Must be called AFTER
+    /// SplitSamplersIntoSamplersAndTextures.
+    ///
+    /// The GLSL emitted by Babylon.js contains user functions that take combined
+    /// samplers as parameters and pass uniform samplers to them at the call site, e.g.
+    ///
+    ///     vec3 fetch(sampler2D s, vec2 uv) { return texture(s, uv).rgb; }
+    ///     void main() { ... fetch(myUniformSampler, uv); }
+    ///
+    /// glslang's SPIR-V emitter requires opaque (sampler) function arguments to be
+    /// l-values (it calls `accessChainGetLValue()` on them). After
+    /// SplitSamplersIntoSamplersAndTextures has rewritten the call-site sampler argument
+    /// into an `EOpConstructTextureSampler(t, s)` aggregate (an r-value), glslang
+    /// asserts at `SpvBuilder.cpp:accessChainGetLValue()`. See TPC #1584 for details.
+    ///
+    /// This pass fixes the assert by:
+    ///   1. Rewriting each user function with sampler parameters: each `sampler2D s`
+    ///      parameter becomes two parameters `texture2D sTexture, sampler s`, and every
+    ///      reference to the original `s` in the body becomes an
+    ///      `EOpConstructTextureSampler(sTexture, s)` aggregate.
+    ///   2. Rewriting every call site to such functions: the single
+    ///      `EOpConstructTextureSampler(t, s)` argument is replaced with two separate
+    ///      arguments (t and s).
+    void SplitSamplerFunctionParameters(glslang::TProgram& program, IdGenerator& ids);
+
     /// Invert dFdy operands similar to bgfx_shader.sh
     /// https://github.com/bkaradzic/bgfx/blob/7be225bf490bb1cd231cfb4abf7e617bf35b59cb/src/bgfx_shader.sh#L44-L45
     /// https://github.com/bkaradzic/bgfx/blob/7be225bf490bb1cd231cfb4abf7e617bf35b59cb/src/bgfx_shader.sh#L62-L65

Plugins/ShaderCompiler/Source/ShaderCompilerVulkan.cpp

@@ -83,6 +83,7 @@ namespace Babylon::Plugins
         std::map<std::string, std::string> vertexAttributeRenaming = {};
         ShaderCompilerTraversers::AssignLocationsAndNamesToVertexVaryingsD3D(program, ids, vertexAttributeRenaming);
         ShaderCompilerTraversers::SplitSamplersIntoSamplersAndTextures(program, ids);
+        ShaderCompilerTraversers::SplitSamplerFunctionParameters(program, ids);
         ShaderCompilerTraversers::InvertYDerivativeOperands(program);
 
         std::vector<uint32_t> spirvVS;