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Special-case ReEmpty in expand_node().

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This wins 6% on `unicode_normalization`, by avoiding a call to
`lub_concrete_regions()` and a `Region` equality test.
This commit is contained in:
Nicholas Nethercote 2019-10-10 13:06:12 +11:00
parent 53e739305a
commit 59e41edcc1
1 changed files with 9 additions and 1 deletions
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10
src/librustc/infer/lexical_region_resolve/mod.rs
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@ -360,13 +360,21 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
match *b_data {
VarValue::Value(cur_region) => {
// Identical scopes can show up quite often, if the fixed point
// iteration converges slowly, skip them
// iteration converges slowly. Skip them. This is purely an
// optimization.
if let (ReScope(a_scope), ReScope(cur_scope)) = (a_region, cur_region) {
if a_scope == cur_scope {
return false;
}
}
// This is a specialized version of the `lub_concrete_regions`
// check below for a common case, here purely as an
// optimization.
if let ReEmpty = a_region {
return false;
}
let mut lub = self.lub_concrete_regions(a_region, cur_region);
if lub == cur_region {
return false;