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// We're testing x86 target specific features
//@only-target: x86_64 i686
//! rsqrt and rcp SSE/AVX operations are approximate. We use that as license to treat them as
//! non-deterministic. Ensure that we do indeed see random results within the expected error bounds.
#[cfg(target_arch = "x86")]
use std::arch::x86::*;
#[cfg(target_arch = "x86_64")]
use std::arch::x86_64::*;
use std::collections::HashSet;
fn main() {
let mut vals = HashSet::new();
for _ in 0..50 {
unsafe {
// Compute the inverse square root of 4.0, four times.
let a = _mm_setr_ps(4.0, 4.0, 4.0, 4.0);
let exact = 0.5;
let r = _mm_rsqrt_ps(a);
let r: [f32; 4] = std::mem::transmute(r);
// Check the results.
for r in r {
vals.insert(r.to_bits());
// Ensure the relative error is less than 2^-12.
let rel_error = (r - exact) / exact;
let log_error = rel_error.abs().log2();
assert!(
rel_error == 0.0 || log_error < -12.0,
"got an error of {rel_error} = 2^{log_error}"
);
}
}
}
// Ensure we saw a bunch of different results.
assert!(vals.len() >= 50);
}
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