[clang] [HLSL] Constant buffers codegen (PR #124886)

[Helena Kotas via cfe-commits]

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@@ -56,9 +75,18 @@ llvm::Type *DirectXTargetCodeGenInfo::getHLSLType(CodeGenModule &CGM,
 
     return llvm::TargetExtType::get(Ctx, TypeName, {ElemType}, Ints);
   }
-  case llvm::dxil::ResourceClass::CBuffer:
-    llvm_unreachable("dx.CBuffer handles are not implemented yet");
-    break;
+  case llvm::dxil::ResourceClass::CBuffer: {
+    QualType ContainedTy = ResType->getContainedType();
+    if (ContainedTy.isNull() || !ContainedTy->isStructureType())
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hekota wrote:

The pattern has been to return `nullptr` for types we don't know how to convert. An assert with message "Generic handling of HLSL types is not supported." will fire in `CGHLSLRuntime::convertHLSLSpecificType` if the converted type is null.

https://github.com/llvm/llvm-project/pull/124886