[clang] [HLSL] Codegen for `cbuffer` declarations without embedded arrays or structs (PR #119755)

[Helena Kotas via cfe-commits]

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@@ -164,18 +164,18 @@ Decl *SemaHLSL::ActOnStartBuffer(Scope *BufferScope, bool CBuffer,
   return Result;
 }
 
-// Calculate the size of a legacy cbuffer type based on
+// Calculate the size of a legacy cbuffer type in bytes based on
 // https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-packing-rules
 static unsigned calculateLegacyCbufferSize(const ASTContext &Context,
                                            QualType T) {
   unsigned Size = 0;
-  constexpr unsigned CBufferAlign = 128;
+  constexpr unsigned CBufferAlign = 16;
   if (const RecordType *RT = T->getAs<RecordType>()) {
     const RecordDecl *RD = RT->getDecl();
     for (const FieldDecl *Field : RD->fields()) {
       QualType Ty = Field->getType();
       unsigned FieldSize = calculateLegacyCbufferSize(Context, Ty);
-      unsigned FieldAlign = 32;
+      unsigned FieldAlign = 4;
       if (Ty->isAggregateType())
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hekota wrote:

This is not the correct alignment, it does not work for 16-bit types and probably not for 64-bit types either.
I have filed a bug here: llvm/llvm-project#119641


https://github.com/llvm/llvm-project/pull/119755