[llvm-bugs] [Bug 47836] New: [Windows][AArch64] Returning structures from functions has wrong ABI

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=47836

            Bug ID: 47836
           Summary: [Windows][AArch64] Returning structures from functions
                    has wrong ABI
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: myriachan at gmail.com
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

Created attachment 24056
  --> https://bugs.llvm.org/attachment.cgi?id=24056&action=edit
source files to reproduce

Clang++ has an incorrect ABI for Windows ARM64.  When returning a non-POD type
from a function in Windows, the function is expected to return the hidden
destination pointer in X0.  This will crash in certain scenarios when MSVC
compiles some translation units and Clang++ others.

This is equivalent to the following existing bug, but for ARM64 instead of
x86/x86-64.  I have not checked ARM32 Windows.
https://bugs.llvm.org/show_bug.cgi?id=15556

clang-cl --target=arm64-pc-windows-msvc /c /MT /GS vectorbug-clang-side.cpp
cl /c /MT /GS vectorbug-msvc-side.cpp
link /DEBUG /OUT:vectorbug.exe vectorbug-msvc-side.obj vectorbug-clang-side.obj
libcmt.lib kernel32.lib

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