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[GSB] Don't use archetype anchor ordering when merging equivalence classes.

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When we merge equivalence classes (by choosing a new representative),
we already prefer the potential archetype with the shorter nesting
depth. However, barring that, we were preferring the potential
archetype that is a better archetype anchor. At one point we depended
on this, but now it's an extra cost that has the side effect of
building more potential archetypes than we really need at this stage.

Eliminate the compareDependentTypes() check when merging equivalence
classes. The intent is that we only need to form archetype anchors
when enumerating requirements or canonicalizing---not during the
normal "solving" path of the GSB.
This commit is contained in:
Doug Gregor
2017-06-27 22:53:33 -07:00
parent a8181630a7
commit d9b9604326
3 changed files with 8 additions and 14 deletions
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12
lib/AST/GenericSignatureBuilder.cpp
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@@ -1690,8 +1690,6 @@ PotentialArchetype *PotentialArchetype::getArchetypeAnchor(
equivClass->archetypeAnchorCache.numMembers
== equivClass->members.size()) {
++NumArchetypeAnchorCacheHits;
assert(equivClass->archetypeAnchorCache.anchor->getNestingDepth()
<= rep->getNestingDepth());
return equivClass->archetypeAnchorCache.anchor;
}
@@ -1710,8 +1708,6 @@ PotentialArchetype *PotentialArchetype::getArchetypeAnchor(
}
#endif
assert(anchor->getNestingDepth() <= rep->getNestingDepth());
// Record the cache miss and update the cache.
++NumArchetypeAnchorCacheMisses;
equivClass->archetypeAnchorCache.anchor = anchor;
@@ -3331,11 +3327,9 @@ GenericSignatureBuilder::addSameTypeRequirementBetweenArchetypes(
unsigned nestingDepth2 = T2->getNestingDepth();
// Decide which potential archetype is to be considered the representative.
// We prefer potential archetypes with lower nesting depths (because it
// prevents us from unnecessarily building deeply nested potential archetypes)
// and prefer anchors because it's a minor optimization.
if (nestingDepth2 < nestingDepth1 ||
compareDependentTypes(&T2, &T1) < 0) {
// We prefer potential archetypes with lower nesting depths, because it
// prevents us from unnecessarily building deeply nested potential archetypes.
if (nestingDepth2 < nestingDepth1) {
std::swap(T1, T2);
std::swap(OrigT1, OrigT2);
}