Author: benlangmuir
Date: Fri Apr 10 17:25:42 2015
New Revision: 234655
URL: http://llvm.org/viewvc/llvm-project?rev=234655&view=rev
Log:
Workaround a performance issue with modules + PCH
More fallout from r228234; when looking up an identifier in a PCH that
imports the Cocoa module on Darwin, it was taking 2 to 5 seconds
because we were hammering the MapVector::erase() function, which is
O(n). For now, just clear() the contained SmallVector to get back to
0.25 - 0.5 seconds. This is probably not the long-term fix, because
without modules or without PCH the performance is more like 0.02
seconds.
Modified:
cfe/trunk/lib/Serialization/ASTReader.cpp
Modified: cfe/trunk/lib/Serialization/ASTReader.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTReader.cpp?rev=234655&r1=234654&r2=234655&view=diff
==============================================================================
--- cfe/trunk/lib/Serialization/ASTReader.cpp (original)
+++ cfe/trunk/lib/Serialization/ASTReader.cpp Fri Apr 10 17:25:42 2015
@@ -8668,7 +8668,10 @@ void ASTReader::pushExternalDeclIntoScop
if (It != PendingFakeLookupResults.end()) {
for (auto *ND : PendingFakeLookupResults[II])
SemaObj->IdResolver.RemoveDecl(ND);
- PendingFakeLookupResults.erase(It);
+ // FIXME: this works around module+PCH performance issue.
+ // Rather than erase the result from the map, which is O(n), just clear
+ // the vector of NamedDecls.
+ It->second.clear();
}
}
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