From f0d3df39cbe1a3afaaabddbc5764b4057c713dd5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Steinbrink?= Date: Tue, 15 Jan 2019 21:53:37 +0100 Subject: [PATCH] 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. --- src/librustc/infer/lexical_region_resolve/mod.rs | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/src/librustc/infer/lexical_region_resolve/mod.rs b/src/librustc/infer/lexical_region_resolve/mod.rs index 39ce8cc621b4..24ead3740313 100644 --- a/src/librustc/infer/lexical_region_resolve/mod.rs +++ b/src/librustc/infer/lexical_region_resolve/mod.rs @@ -236,6 +236,14 @@ 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; @@ -275,12 +283,6 @@ 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(..))