[clang] [llvm] [Clang][ABI][X86] Do not emit zeroext/signext for return values (PR #232729)

[Nikita Popov via cfe-commits]

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@@ -2838,7 +2850,9 @@ ABIArgInfo X86_64ABIInfo::classifyReturnType(QualType RetTy) const {
 
       if (RetTy->isIntegralOrEnumerationType() &&
           isPromotableIntegerTypeForABI(RetTy))
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nikic wrote:

If you're wondering why this peculiar `isPromotableIntegerTypeForABI()` check is here even though `shouldExtendReturnType()` will also check it, the reason is that Clang uses `iN` for `_BitInt(N)` if N <= 32, but always uses `i64` if `32 < N <= 64`. This seems peculiar and possibly unintended, but I've left it alone for now.

https://github.com/llvm/llvm-project/pull/232729