Regression: tests/codegen/issues/issue-101082.rs fails with -Ctarget-cpu=x86-64-v3 #131563
Description
Code
I tried this test with -Ctarget-cpu=x86-64-v3 (which we have on by default in the upcoming RHEL 10):
tests/codegen/issues/issue-101082.rs
//@ compile-flags: -O #![crate_type = "lib"] #[no_mangle] pub fn test() -> usize { // CHECK-LABEL: @test( // CHECK: ret {{i64|i32}} 165 let values = [23, 16, 54, 3, 60, 9]; let mut acc = 0; for item in values { acc += item; } acc }I expected to see this happen: FileCheck pass
Instead, this happened:
issue-101082.rs:8:12: error: CHECK: expected string not found in input As of rustc 1.83.0-nightly (52fd99839 2024-10-10), that LLVM IR is:
; Function Attrs: nofree norecurse nosync nounwind nonlazybind memory(inaccessiblemem: write) uwtable define noundef i64 @test() unnamed_addr #0 personality ptr @rust_eh_personality { start: %iter = alloca [64 x i8], align 8 call void @llvm.lifetime.start.p0(i64 64, ptr nonnull %iter) store i64 23, ptr %iter, align 8 %_3.sroa.0.sroa.4.0.iter.sroa_idx = getelementptr inbounds i8, ptr %iter, i64 8 store i64 16, ptr %_3.sroa.0.sroa.4.0.iter.sroa_idx, align 8 %_3.sroa.0.sroa.5.0.iter.sroa_idx = getelementptr inbounds i8, ptr %iter, i64 16 store i64 54, ptr %_3.sroa.0.sroa.5.0.iter.sroa_idx, align 8 %_3.sroa.0.sroa.6.0.iter.sroa_idx = getelementptr inbounds i8, ptr %iter, i64 24 store i64 3, ptr %_3.sroa.0.sroa.6.0.iter.sroa_idx, align 8 %_3.sroa.0.sroa.7.0.iter.sroa_idx = getelementptr inbounds i8, ptr %iter, i64 32 store i64 60, ptr %_3.sroa.0.sroa.7.0.iter.sroa_idx, align 8 %_3.sroa.0.sroa.8.0.iter.sroa_idx = getelementptr inbounds i8, ptr %iter, i64 40 store i64 9, ptr %_3.sroa.0.sroa.8.0.iter.sroa_idx, align 8 %unmaskedload = load <4 x i64>, ptr %iter, align 8, !alias.scope !3 %0 = getelementptr inbounds i8, ptr %iter, i64 32 %unmaskedload10 = load <4 x i64>, ptr %0, align 8, !alias.scope !3 %1 = add <4 x i64> %unmaskedload10, %unmaskedload %2 = shufflevector <4 x i64> %1, <4 x i64> %unmaskedload, <4 x i32> <i32 0, i32 1, i32 6, i32 7> %3 = tail call i64 @llvm.vector.reduce.add.v4i64(<4 x i64> %2) call void @llvm.lifetime.end.p0(i64 64, ptr nonnull %iter) ret i64 %3 }Reducing to x86-64-v2 does get the expected output:
; Function Attrs: nofree norecurse nosync nounwind nonlazybind memory(inaccessiblemem: write) uwtable define noundef i64 @test() unnamed_addr #0 personality ptr @rust_eh_personality { start: ret i64 165 }Version it worked on
It most recently worked on: Rust 1.79.0
Version with regression
rustc --version --verbose:
rustc 1.80.0 (051478957 2024-07-21) binary: rustc commit-hash: 051478957371ee0084a7c0913941d2a8c4757bb9 commit-date: 2024-07-21 host: x86_64-unknown-linux-gnu release: 1.80.0 LLVM version: 18.1.7 Note that the original issue #101082 was fixed by an LLVM upgrade. That version didn't change between 1.79.0 and 1.80.0, but there were some additional cherry-picks: rust-lang/llvm-project@rustc-1.79.0...rustc-1.80.0
However, cargo-bisect-rustc narrowed down to something else.
Bisection
searched nightlies: from nightly-2024-04-28 to nightly-2024-10-11
regressed nightly: nightly-2024-05-26
searched commit range: 36153f1...1ba35e9
regressed commit: 48f0011 (#121571)
bisected with cargo-bisect-rustc v0.6.9
Host triple: x86_64-unknown-linux-gnu
Reproduce with:
cargo bisect-rustc --script test.sh --start 1.79.0#!/bin/sh rustc --emit=llvm-ir -O -Ctarget-cpu=x86-64-v3 -o- issue-101082.rs | FileCheck issue-101082.rs@rustbot modify labels: +A-codegen +regression-from-stable-to-stable -regression-untriaged