[Sonicadvance1]

This gets the HostFeaturesHash matching between Linux and arm64ec.

wow64 is the odd one out as it doesn't support AVX, it's the only flag that differs. We need to get wow64 AVX support wired up.

[Sonicadvance1]

A note, on SVE supporting targets the flags will still differ between Linux and wine because SVE is currently hard disabled on Wine due to the inability to save predicates.

[mstorsjo]

The commit for enabling preserve_all on Windows targets, since llvm/llvm-project#166436, doesn't work fully unfortunately.

While that PR did make it possible to use preserve_all and preserve_most on Windows targets in general, it doesn't seem to work properly if unwind info generation is enabled (as it is by default for such targets). The code generation ends up backing up x9 on the stack, and tries to represent this in unwind info, where it is unrepresentable (only registers >= x19 can be handled there).

The problematic thing is that this only shows up if using a Clang built with asserts enabled. With Clang without asserts, it silently builds an object file, where the unwind info is bogus compared with the function.

Building fails on FEXCore/Source/Interface/Core/Interpreter/Fallbacks/StringCompareFallbacks.cpp, External/SoftFloat-3e/src/s_normRoundPackToExtF80.c and FEXCore/Source/Interface/Core/Interpreter/Fallbacks/InterpreterFallbacks.cpp, with assert failures like this:

clang: ../lib/MC/MCWin64EH.cpp:1429: void ARM64EmitUnwindCode(llvm::MCStreamer&, const llvm::WinEH::Instruction&): Assertion `inst.Register >= 19 && "Saved registers must be >= 19"' failed.

The issue is reproducible with a small reduced test case like this:

long a, b;
int c, e;
char d;
__attribute__((preserve_all)) void f();
__attribute__((preserve_all)) void g() {
  d = a;
  c -= d;
  long h, i = b >> -d;
  h = b << d;
  f(e, 0, i, h, 0);
}

$ clang -target aarch64-windows-msvc -O2 repro.c -c
clang: ../lib/MC/MCWin64EH.cpp:1413: void ARM64EmitUnwindCode(llvm::MCStreamer&, const llvm::WinEH::Instruction&): Assertion `inst.Register >= 19 && "Saved reg must be >= 19"' failed.

The same happens for both aarch64-windows-msvc and aarch64-windows-gnu (aka aarch64-w64-mingw32) targets, and happens the same for both preserve_all and preserve_most. Building these source files with -fno-asynchronous-unwind-tables does avoid hitting the assert though.

If building with a version of Clang without asserts, building succeeds, but the unwind info doesn't match the actual code:

$ llvm-objdump -d repro.o 

repro.o:        file format coff-arm64

Disassembly of section .text:

0000000000000000 <g>:
       0: f81f0fe9      str     x9, [sp, #-0x10]!
       4: 90000008      adrp    x8, 0x0 <g>
       8: 90000011      adrp    x17, 0x0 <g>
       c: 90000006      adrp    x6, 0x0 <g>
      10: b9400108      ldr     w8, [x8]
[...]
$ llvm-readobj --unwind repro.o 

File: repro.o
Format: COFF-ARM64
Arch: aarch64
AddressSize: 64bit
UnwindInformation [
  RuntimeFunction {
    Function: g (0x0)
    ExceptionRecord: .xdata (0x0)
    ExceptionData {
      FunctionLength: 84
      Version: 0
      ExceptionData: No
      EpiloguePacked: Yes
      EpilogueOffset: 0
      ByteCodeLength: 4
      Prologue [
        0xd4c1              ; str x25, [sp, #-16]!
        0xe4                ; end
      ]
    }
  }
]

I posted a note about this at llvm/llvm-project#166436 (comment), but perhaps it would warrant a new issue in llvm of its own.