Missing warning about `target_feature` when using for `core::arch::x86_64` functions

[tesuji]

I tried this code: https://rust.godbolt.org/z/b9A7oP

extern crate core;

use core::arch::x86_64::__m128;
use core::arch::x86_64::_mm_extract_ps;
use core::arch::x86_64::_mm_hadd_ps;

pub unsafe fn add_reduce(a: __m128, b: __m128) -> f32 {
    let c = _mm_hadd_ps(a, b);
    f32::from_bits(_mm_extract_ps(c, 0) as u32)
}

I expect to see this happens: rustc lint about missing target_feature in add_reduce when using _mm_extract_ps.

Instead this happen: There is no warning and functions are not inlined.

Meta

• rustc 1.46.0-nightly (3503f56 2020-07-02) x86_64-unknown-linux-gnu

[jonas-schievink]

You need to use #[target_feature(enable = "sse4.1")] on the function, or the compiler won't be able to inline things

[tesuji]

Adding that attribute has no effect: https://rust.godbolt.org/z/VGswwX

Edit: Oh, I have to add it in function, not module level.

[tesuji]

Anyway, I thought that the compiler could warn me about missing the target_feature attribute when using
those functions.

[tesuji]

Will be closed by #73461 when it get merged.