Found here: #105344 (comment)

Code:

#![feature(portable_simd)] fn main() { use core::simd::Simd; let a = Simd::from_array([0, 4, 1, 5]); let b = Simd::from_array([2, 6, 3, 7]); let (x, y) = a.deinterleave(b); assert_eq!(x.to_array(), [0, 1, 2, 3]); assert_eq!(y.to_array(), [4, 5, 6, 7]); }

Invocation:

$ rustc +nightly --version rustc 1.67.0-nightly (e1d819583 2022-12-05) binary: rustc commit-hash: e1d819583f0bf13b016b119c1c2c43e6d3979450 commit-date: 2022-12-05 host: x86_64-unknown-linux-gnu release: 1.67.0-nightly LLVM version: 15.0.4 Compiler returned: 0 $ rustc +nightly --edition 2021 -C opt-level=3 -Zmir-opt-level=3 -C no-prepopulate-passes

Causes an LLVM ICE:

Invalid bitcast %27 = bitcast <4 x i32> %22 to [4 x i32], !dbg !268 Invalid bitcast %31 = bitcast <4 x i32> %26 to [4 x i32], !dbg !280 in function _ZN7example4main17h82e1f57aed922fc8E LLVM ERROR: Broken function found, compilation aborted! Compiler returned: 101 

This reproduces easily on Godbolt.

The invalid bitcast is introduced by codgen for the MIR statement _1 = (_25.0: [i32; 4]); on line 151.

Local _25 has type std::simd::Simd<i32, 4>. I believe the bitcast is introduced here, but I don't think this path is even intended to handle Simd types. I'm not exactly sure what the bug here is either, ie I have no idea how this was supposed to be codegened.

@rustbot label +A-codegen +A-llvm +I-ICE +T-compiler