[clang] [CIR] Add basic support for operator new (PR #145802)

[Andy Kaylor via cfe-commits]

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@@ -95,6 +95,7 @@ CIRGenModule::CIRGenModule(mlir::MLIRContext &mlirContext,
   // TODO(CIR): Should be updated once TypeSizeInfoAttr is upstreamed
   const unsigned sizeTypeSize =
       astContext.getTypeSize(astContext.getSignedSizeType());
+  SizeSizeInBytes = astContext.toCharUnitsFromBits(sizeTypeSize).getQuantity();
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andykaylor wrote:

> Ah, huh... that is undefined behavior...

Oh, right. You caught me thinking like a C programmer (very old habit). I'm pretty sure that is the intent of the original code though. This part, at least, I can confidently fix. I agree with @bcardosolopes about the long-term solution, but I will avoid introducing this union for now.

https://github.com/llvm/llvm-project/pull/145802