ziglang/zig

Compiler gets stuck in Infinite (so far) loop

Validark opened this issue · 4 comments

Validark commented

Zig Version

0.13.0-dev.75+5c9eb4081

Steps to Reproduce and Observed Behavior

https://zig.godbolt.org/z/GYdeh839e

Compiling this code for Zen 4:

export fn popCount(x: @Vector(8, u64)) u64 {
    return @reduce(.Add, @popCount(x));
}

Takes forever (so far). I have reproduced this on my machine for the version indicated (0.13.0-dev.75+5c9eb4081), and also noted that it times out 0.11.0 and 0.12.0 in compiler explorer.

Expected Behavior

The program to terminate at some point, preferably compiling the code!

xdBronch commented

this isnt reproducing for me locally on 0.13.0-dev.201+86d8688c7. fixed in the llvm 18 upgrade maybe?

mlugg commented

Indeed, this spits out an LLVM assertion on my pre-LLVM18 build:

LLVM Emit Object... zig: /home/mlugg/llvm17/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp:982: void {anonymous}::SelectionDAGLegalize::LegalizeOp(llvm::SDNode*): Assertion `(TLI.getTypeAction(*DAG.getContext(), Op.getValueType()) == TargetLowering::TypeLegal || Op.getOpcode() == ISD::TargetConstant || Op.getOpcode() == ISD::Register) && "Unexpected illegal type!"' failed.

I'm willing to bet this was indeed fixed with the LLVM 18 upgrade, but to be sure, I will wait for someone with a debug build of a post-LLVM18 compiler to confirm that no assertion is tripped.

mikdusan commented

that's a dupe: andrew filed llvm/llvm-project#90356 and fixed in 18.1.x

confirmed:

  • zig 0.12.0 w/ llvm-17.0.6 release+assert trips assertion
  • zig 0.12.0 w/ llvm-17.0.6 release spins infinite
  • zig master w/ llvm-18.1.5 release+assert does not trip assertion (builds object)
  • zig master w/ llvm-18.1.5 release builds object
mlugg commented

Cool!