[all-commits] [llvm/llvm-project] 760910: [Arm64EC] Improve alignment mangling in arm64ec th...

[Eli Friedman via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 760910ddb918d77e7632be1678f69909384d69ae
      https://github.com/llvm/llvm-project/commit/760910ddb918d77e7632be1678f69909384d69ae
  Author: Eli Friedman <efriedma at quicinc.com>
  Date:   2024-04-26 (Fri, 26 Apr 2024)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64Arm64ECCallLowering.cpp
    M llvm/test/CodeGen/AArch64/arm64ec-entry-thunks.ll
    M llvm/test/CodeGen/AArch64/arm64ec-exit-thunks.ll

  Log Message:
  -----------
  [Arm64EC] Improve alignment mangling in arm64ec thunks. (#90115)

In some cases, MSVC's mangling for arm64ec thunks includes the alignment
of a struct. I added some code to try to match... but it never really
worked right. The issues:

- Alignment is only mangled if it's 16 or more (I guess the default is
supposed to be 8).
- Alignment isn't mangled on return values (since the memory is
allocated by the caller).

The current patch leaves hooks to make alignment mangling work... but
doesn't actually ever mangle alignment: clang never actually encodes a
relevant alignment into the IR. Once we get clang to emit the real
size/alignment of structs, we can start emitting it.



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