id = 1779
title = "PowerPC AltiVec source vector subnormal values are not flushed to zero"
state = "closed"
created_at = "2023-07-22T21:17:19.526Z"
closed_at = "2023-09-07T15:43:08.538Z"
labels = ["Closed::Fixed", "target: ppc"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/1779"
host-os = "Ubuntu 20.04"
host-arch = "x86-64"
qemu-version = "7.0.0"
guest-os = "Ubuntu"
guest-arch = "PowerPC"
description = """AltiVec specifies that source and result vectors are flushed to zero (in NJ mode).  Only result vectors are flushed to zero."""
reproduce = """1. Compile the attached Rust program (e.g. `cargo +nightly build --target powerpc-unknown-linux-gnu`)
2. Run the program and expect assertions to pass.
3. See assertions fail."""
additional = """See the offending Rust program:

```
#![feature(stdsimd, powerpc_target_feature)]

use std::arch::powerpc::*;

#[target_feature(enable = "altivec")]
unsafe fn add(x: f32, y: f32) -> f32 {
    let array: [f32; 4] = unsafe { std::mem::transmute(vec_add(vec_splats(x), vec_splats(y))) };
    array[0]
}

pub fn main() {
    let result = unsafe { add(-1.0857398e-38, 0.) };
    assert_eq!(result, 0.);

    // if the input is flushed, the result will be +0
    // if only the output is flushed, the result is -0
    assert!(result.is_sign_positive());
}
```"""