[clang] [HLSL] Appropriately set function attribute optnone (PR #125937)

[Justin Bogner via cfe-commits]

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@@ -345,6 +345,9 @@ void clang::CodeGen::CGHLSLRuntime::setHLSLEntryAttributes(
                 WaveSizeAttr->getPreferred());
     Fn->addFnAttr(WaveSizeKindStr, WaveSizeStr);
   }
+  if (CGM.getCodeGenOpts().OptimizationLevel == 0) {
+    Fn->addFnAttr(llvm::Attribute::OptimizeNone);
+  }
   Fn->addFnAttr(llvm::Attribute::NoInline);
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bogner wrote:

Ok. I think a comment to the effect of "We need to manually set attributes here instead of relying on `SetLLVMFunctionAttributesForDefinition` to pick them up since these functions are injected by the compiler and won't go through the normal flow" (please reword as necessary to be accurate...) would be a good idea here.

https://github.com/llvm/llvm-project/pull/125937