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Auto merge of #57697 - dotdash:fast_lex_reg_resol_item_bodies, r=nagisa

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Use a faster early exit during region expansion

Turns out that the equality check for regions is rather expensive, and
the current early exit check works in such a way, that the comparison is
even done twice. As we only really care about the case of equal scopes,
we can perform a faster, more specialized check and move it up one
level, so we can eventually skip the additional full comparison as well.
This commit is contained in:
bors 2019-01-20 16:24:27 +00:00
commit 794e22862c
1 changed files with 8 additions and 6 deletions
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14
src/librustc/infer/lexical_region_resolve/mod.rs
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@ -241,6 +241,14 @@ impl<'cx, 'gcx, 'tcx> LexicalResolver<'cx, 'gcx, 'tcx> {
match *b_data {
VarValue::Value(cur_region) => {
// Identical scopes can show up quite often, if the fixed point
// iteration converges slowly, skip them
if let (ReScope(a_scope), ReScope(cur_scope)) = (a_region, cur_region) {
if a_scope == cur_scope {
return false;
}
}
let mut lub = self.lub_concrete_regions(a_region, cur_region);
if lub == cur_region {
return false;
@ -280,12 +288,6 @@ impl<'cx, 'gcx, 'tcx> LexicalResolver<'cx, 'gcx, 'tcx> {
fn lub_concrete_regions(&self, a: Region<'tcx>, b: Region<'tcx>) -> Region<'tcx> {
let tcx = self.tcx();
// Equal scopes can show up quite often, if the fixed point
// iteration converges slowly, skip them
if a == b {
return a;
}
match (a, b) {
(&ty::ReClosureBound(..), _)
| (_, &ty::ReClosureBound(..))