llvm backend fails to build multiple var args behavior tests on s390x-linux

[nektro]

Zig Version

0.14.0-dev.1509+fb81522e0

Steps to Reproduce and Observed Behavior

$ ./build/stage3/bin/zig test test/behavior.zig -target s390x-linux-musl --test-cmd qemu-s390x --test-cmd-bin

LLVM ERROR: Cannot select: 0xc7c3270: i32,ch = vaarg 0xd585ec0, FrameIndex:i64<1>, SrcValue:ch<0xa52d3a0>, TargetConstant:i32<4>, var_args.zig:114:13
  0xcea2cc0: i64 = FrameIndex<1>
  0xde9d860: i32 = TargetConstant<4>
In function: behavior.var_args.test.simple variadic function.S.simple
Aborted (core dumped)

LLVM ERROR: Cannot select: 0xf633a90: i64,ch = vaarg 0xdde0ca0:1, FrameIndex:i64<3>, SrcValue:ch<0xbc25aa0>, TargetConstant:i32<8>, var_args.zig:178:17
  0xdfa63d0: i64 = FrameIndex<3>
  0xf004670: i32 = TargetConstant<8>
In function: behavior.var_args.test.coerce reference to var arg.S.addPtr
Aborted (core dumped)

LLVM ERROR: Cannot select: 0xc3c2790: i32,ch = vaarg 0x4df2dd0, 0xc4d6f40, SrcValue:ch<0x5af3bf0>, TargetConstant:i32<4>, var_args.zig:222:21
  0xc4d6f40: i64,ch = CopyFromReg 0x4df2dd0, Register:i64 %17, var_args.zig:222:21
    0xdc765e0: i64 = Register %17
  0xc3f76f0: i32 = TargetConstant<4>
In function: behavior.var_args.test.variadic functions.S.vprintf
Aborted (core dumped)

LLVM ERROR: Cannot select: 0xcc62280: i32,ch = vaarg 0xca5cd60:1, FrameIndex:i64<5>, SrcValue:ch<0xa936340>, TargetConstant:i32<4>, var_args.zig:258:17
  0xd288b10: i64 = FrameIndex<5>
  0xe5927b0: i32 = TargetConstant<4>
In function: behavior.var_args.test.copy VaList.S.add
Aborted (core dumped)

LLVM ERROR: Cannot select: 0xf022ac0: i32,ch = vaarg 0xec43c40:1, FrameIndex:i64<1>, SrcValue:ch<0xb211820>, TargetConstant:i32<4>, var_args.zig:294:13
  0xec50ac0: i64 = FrameIndex<1>
  0xd8baa40: i32 = TargetConstant<4>
In function: behavior.var_args.test.unused VaList arg.S.thirdArg
Aborted (core dumped)

Expected Behavior

tests passing

[Vexu]

The var arg instructions in LLVM don't work properly on most targets because clang doesn't use them. Reimplementing them ourselves like clang does would fix this as well.

[alexrp]

I don't think this is an upstream bug. I believe we need to emit code similar to Clang: https://github.com/llvm/llvm-project/blob/1bb52e94621d2cba4f34504697cb0ea83805cb98/clang/lib/CodeGen/Targets/SystemZ.cpp#L246

[Vexu]

That's what I meant by clang not using the va_arg instruction, I ran into it when originally implementing the feature and it's the reason why VaList is disabled on many targets.

[alexrp]

docs
└─ langref
   └─ install generated to doc/langref.html
      └─ run exe docgen (langref.html)
         └─ WriteFile test_defining_variadic_function.out
            └─ run exe doctest (test_defining_variadic_function.out) failure
LLVM ERROR: Cannot select: t8: i32,ch = vaarg t4:1, FrameIndex:i64<3>, SrcValue:ch<0x5fb3670>, TargetConstant:i32<4>, test_defining_variadic_function.zig:11:9
In function: test_defining_variadic_function.add

The following command crashed:
../../../build/debug/bin/zig test ../../../doc/langref/test_defining_variadic_function.zig --zig-lib-dir ../../../lib
error: test failed
error: process exited with error code 1
failed command: /home/ci/zig/.zig-cache/o/4c62e7bce68e4f1586a52bbc316521a7/doctest --zig /home/ci/zig/build/debug/bin/zig --cache-root /home/ci/zig/.zig-cache --zig-lib-dir /home/ci/zig/lib/ -i /home/ci/zig/doc/langref/test_defining_variadic_function.zig -o /home/ci/zig/.zig-cache/o/6e81b0fe13a78fa6f77626332e334669/test_defining_variadic_function.out