Bad codegen for widen followed by ARM vdupq_n_* #137407
Description
Code
I tried this code:
use std::arch::aarch64::*; #[no_mangle] pub unsafe fn half_dup(x: u16) -> uint16x8_t { vaddq_u16(vreinterpretq_u16_u32(vdupq_n_u32(x as u32)), vdupq_n_u16(1)) }I expected to see this happen: The compiled output would use the dup instruction
Instead, this happened: The compiled output uses a bunch of movs instead
Version it worked on
It most recently worked on: Rust 1.81.0
Version with regression
rustc --version --verbose:
rustc 1.82.0 (f6e511eec 2024-10-15) binary: rustc commit-hash: f6e511eec7342f59a25f7c0534f1dbea00d01b14 commit-date: 2024-10-15 host: x86_64-unknown-linux-gnu release: 1.82.0 LLVM version: 19.1.1 and
rustc 1.87.0-nightly (f280acf4c 2025-02-19) binary: rustc commit-hash: f280acf4c743806abbbbcfe65050ac52ec4bdec0 commit-date: 2025-02-19 host: x86_64-unknown-linux-gnu release: 1.87.0-nightly LLVM version: 20.1.0