[clang] [llvm] [LLVMABI][AARCH64] Add support for simple direct return case (PR #216437)

[Andy Kaylor via llvm-commits]

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@@ -352,6 +352,9 @@ bool CodeGenModule::shouldUseLLVMABILowering(unsigned CallingConv) const {
   if (T.isBPF())
     return true;
 
+  if (T.getArch() == llvm::Triple::aarch64 && !T.isOSWindows())
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andykaylor wrote:

I didn't realize they were so similar. Clang has a separate `TargetCodeGenInfo` class for Windows, so I just assumed the differences would be significant, but I just looked at the implementation, and I see that the same `AArch64ABIInfo` class is used for both. I did see that there is some Windows-specific handling in the ABI class, but, as you say, not much.

I'll enable this for Windows in an upcoming PR and start extending the testing to Windows targets.

https://github.com/llvm/llvm-project/pull/216437