llvm: assertion triggered when casting non-register-sized integer to float

[jacobly0]

export fn entry() void {
    var a: u15 = 42;
    var b: f32 = @floatFromInt(a);
    _ = b;
}

$ zig build-obj repro.zig -mcpu x86_64+avx512f
LLVM Emit Object... zig: llvm/include/llvm/CodeGen/ValueTypes.h:300: MVT llvm::EVT::getSimpleVT() const: Assertion `isSimple() && "Expected a SimpleValueType!"' failed.
Aborted (core dumped)

This bug is currently triggered by this code when compiling the compiler under the proper circumstances (don't look at the cast direction too closely 🙄).

upstream: llvm/llvm-project#68068

[andrewrk]

Is this a regression? I notice the fix has not made its way into the release/17.x branch.

[jacobly0]

It has been a bug since at least 16.0.0 15.0.7.

[andrewrk]

Gotcha, thanks for checking. Pushing a workaround shortly.

[andrewrk]

Related: #17514

Master branch behavior tests are already tripping another assertion.

[andrewrk]

Workaround landed in ab4d6bf; leaving open to remove the workaround after upgrading to LLVM 18.

[auxiliaire]

Hi, this is still an issue on master branch with LLVM 18 (from apt.llvm.org, Ubuntu 22.04).

/home/v/Projects/zig/zig/src/zig_llvm.cpp:1350:72: error: ‘WebKit_JS’ is not a member of ‘llvm::CallingConv’
 1350 | static_assert((CallingConv::ID)ZigLLVM_WebKit_JS == llvm::CallingConv::WebKit_JS, "");
      |                                                                        ^~~~~~~~~
make[2]: *** [CMakeFiles/zigcpp.dir/build.make:76: CMakeFiles/zigcpp.dir/src/zig_llvm.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:91: CMakeFiles/zigcpp.dir/all] Error 2
make: *** [Makefile:136: all] Error 2

Built with: cmake .. -DCMAKE_PREFIX_PATH="/usr/lib/llvm-18;/usr/lib" -DCMAKE_BUILD_TYPE=Release

[nektro]

LLVM 18 isnt released yet

[auxiliaire]

I can confirm that it works with LLVM 17. This was the source of confusion (from apt.llvm.org):

To install the latest stable version:

bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)"

Which actually installs LLVM 18.

[nektro]

the error you got is additionally odd because cmake should have told you 18 wasnt allowed much sooner than that assert

[auxiliaire]

Yeah, I had plenty of such assert. Just quoted the last one. Also had the same error after switching to 14, but that was maybe because I forgot to clean the build dir. I don't know.

[andrewrk]

Fixed with the merge of LLVM 19 branch in c6ad452.

[Rexicon226]

This should not be closed yet, the test was not re-enabled.
Ignore me, I confused myself with the issue numbers :).