bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

sort_candidates: avoid the second comparison if possible.

Browse source 
This is a performance win for `unicode-normalization`.

The commit also removes the closure, which isn't necessary. And
reformulates the comparison into a form I find easier to read.
This commit is contained in:
Nicholas Nethercote 2022-06-08 17:02:06 +10:00
parent 7e4ec35d0c
commit c4cd04480b
1 changed files with 18 additions and 24 deletions
Download patch file Download diff file Expand all files Collapse all files

42
compiler/rustc_mir_build/src/build/matches/test.rs
View file

@ -632,39 +632,33 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
} }
(&TestKind::Range(test), &PatKind::Range(pat)) => { (&TestKind::Range(test), &PatKind::Range(pat)) => {
use std::cmp::Ordering::*;
if test == pat { if test == pat {
self.candidate_without_match_pair(match_pair_index, candidate); self.candidate_without_match_pair(match_pair_index, candidate);
return Some(0); return Some(0);
} }
let no_overlap = (|| { let tcx = self.tcx;
use rustc_hir::RangeEnd::*; let test_ty = test.lo.ty();
use std::cmp::Ordering::*;
let tcx = self.tcx; // For performance, it's important to only do the second
// `compare_const_vals` if necessary.
let test_ty = test.lo.ty(); let no_overlap = if matches!(
let lo = compare_const_vals(tcx, test.lo, pat.hi, self.param_env, test_ty)?; (compare_const_vals(tcx, test.hi, pat.lo, self.param_env, test_ty)?, test.end),
let hi = compare_const_vals(tcx, test.hi, pat.lo, self.param_env, test_ty)?; (Less, _) | (Equal, RangeEnd::Excluded) // test < pat
) || matches!(
match (test.end, pat.end, lo, hi) { (compare_const_vals(tcx, test.lo, pat.hi, self.param_env, test_ty)?, pat.end),
// pat < test (Greater, _) | (Equal, RangeEnd::Excluded) // test > pat
(_, _, Greater, _) | ) {
(_, Excluded, Equal, _) |
// pat > test
(_, _, _, Less) |
(Excluded, _, _, Equal) => Some(true),
_ => Some(false),
}
})();
if let Some(true) = no_overlap {
// Testing range does not overlap with pattern range,
// so the pattern can be matched only if this test fails.
Some(1) Some(1)
} else { } else {
None None
} };
// If the testing range does not overlap with pattern range,
// the pattern can be matched only if this test fails.
no_overlap
} }
(&TestKind::Range(range), &PatKind::Constant { value }) => { (&TestKind::Range(range), &PatKind::Constant { value }) => {