[SPIR-V] Fix static const in push constants (microsoft#6403)

Struct lowering is slightly different for push constants, and we didn't checked if the field was static or not. In SPIR-V, when a field is const static, we either replace all loads by a the immediate (when usage is `Struct::field`), or create a global variable we initialize to the correct value and reference instead. The field is then ignored from the struct definition, and this variable is used. This hasn't changed with this commit, I just made push-buffers use the same logic. Fixed microsoft#6006 --------- Signed-off-by: Nathan Gauër <[email protected]>
EpicGames · Mar 13, 2024 · 63db29e · 63db29e
1 parent 3fc84bf
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diff --git a/tools/clang/lib/SPIRV/DeclResultIdMapper.cpp b/tools/clang/lib/SPIRV/DeclResultIdMapper.cpp
@@ -1347,6 +1347,13 @@ SpirvVariable *DeclResultIdMapper::createStructOrStructArrayVarOfExplicitLayout(
     const auto *declDecl = cast<DeclaratorDecl>(subDecl);
     auto varType = declDecl->getType();
     if (const auto *fieldVar = dyn_cast<VarDecl>(subDecl)) {
+
+      // Static variables are not part of the struct from a layout perspective.
+      // Thus, they should not be listed in the struct fields.
+      if (fieldVar->getStorageClass() == StorageClass::SC_Static) {
+        continue;
+      }
+
       if (isResourceType(varType)) {
         createExternVar(fieldVar);
         continue;

diff --git a/tools/clang/test/CodeGenSPIRV/vk.push-constant.static.hlsl b/tools/clang/test/CodeGenSPIRV/vk.push-constant.static.hlsl
@@ -0,0 +1,34 @@
+// RUN: %dxc -T vs_6_0 -E main -fcgl  %s -spirv | FileCheck %s
+
+struct S
+{
+  const static uint a = 1;
+  uint b;
+};
+
+// CHECK:                                          OpMemberName %type_PushConstant_S 0 "b"
+// CHECK:                   %type_PushConstant_S = OpTypeStruct %uint
+// CHECK: %_ptr_PushConstant_type_PushConstant_S = OpTypePointer PushConstant %type_PushConstant_S
+
+[[vk::push_constant]] S s;
+// CHECK: %a = OpVariable %_ptr_Private_uint Private
+// CHECK: %s = OpVariable %_ptr_PushConstant_type_PushConstant_S PushConstant
+
+// CHECK: OpStore %a %uint_1
+
+[numthreads(1,1,1)]
+void main()
+{
+  uint32_t v = s.b;
+// CHECK:               %v = OpVariable %_ptr_Function_uint Function
+// CHECK:  [[ptr:%[0-9]+]] = OpAccessChain %_ptr_PushConstant_uint %s %int_0
+// CHECK: [[load:%[0-9]+]] = OpLoad %uint [[ptr]]
+// CHECK:                    OpStore %v [[load]]
+
+  uint32_t w = S::a;
+// CHECK:                    OpStore %w %uint_1
+
+  uint32_t x = s.a;
+// CHECK: [[load:%[0-9]+]] = OpLoad %uint %a
+// CHECK:                    OpStore %x [[load]]
+}