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Auto merge of #84915 - Mark-Simulacrum:bitset-xor-eq, r=jackh726

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Retain data in vectorized registers for longer

This seems to be a mild performance improvement on the keccak crate at least, though not sure it'll show up more broadly.
This commit is contained in:
bors 2021-05-05 01:23:01 +00:00
commit 45ccf91070
1 changed files with 7 additions and 3 deletions
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10
compiler/rustc_index/src/bit_set.rs
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@ -355,14 +355,18 @@ fn bitwise<Op>(out_vec: &mut [Word], in_vec: &[Word], op: Op) -> bool
Op: Fn(Word, Word) -> Word,
{
assert_eq!(out_vec.len(), in_vec.len());
let mut changed = false;
let mut changed = 0;
for (out_elem, in_elem) in iter::zip(out_vec, in_vec) {
let old_val = *out_elem;
let new_val = op(old_val, *in_elem);
*out_elem = new_val;
changed |= old_val != new_val;
// This is essentially equivalent to a != with changed being a bool, but
// in practice this code gets auto-vectorized by the compiler for most
// operators. Using != here causes us to generate quite poor code as the
// compiler tries to go back to a boolean on each loop iteration.
changed |= old_val ^ new_val;
}
changed
changed != 0
}
const SPARSE_MAX: usize = 8;