Implement caching for the linkage and visibility calculations of
declarations.
The motivation for this patch is that linkage/visibility computations
are linear in the number of redeclarations of an entity, and we've run
into a case where a single translation unit has > 6500 redeclarations
of the same (unused!) external variable. Since each redeclaration
involves a linkage check, the resulting quadratic behavior makes Clang
slow to a crawl. With this change, a simple test with 512
redeclarations of a variable syntax-checks ~20x faster than
before.
That said, I hate this change, and will probably end up reverting it
in a few hours. Reasons to hate it:
- It makes NamedDecl larger, since we don't have enough free bits in
Decl to squeeze in the extra information about caching.
- There are way too many places where we need to invalidate this
cache, because the visibility of a declaration can change due to
redeclarations (!). Despite self-hosting and passing the testsuite,
I have no confidence that I've found all of places where this cache
needs to be invalidated.
llvm-svn: 120808
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index b1e46a6..c21dfc2 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -383,7 +383,7 @@
// FunctionDecl's body is handled last at ASTDeclReader::Visit,
// after everything else is read.
- FD->setStorageClass((StorageClass)Record[Idx++]);
+ FD->SClass = (StorageClass)Record[Idx++];
FD->setStorageClassAsWritten((StorageClass)Record[Idx++]);
FD->setInlineSpecified(Record[Idx++]);
FD->setVirtualAsWritten(Record[Idx++]);
@@ -650,7 +650,7 @@
void ASTDeclReader::VisitVarDecl(VarDecl *VD) {
VisitDeclaratorDecl(VD);
VisitRedeclarable(VD);
- VD->setStorageClass((StorageClass)Record[Idx++]);
+ VD->SClass = (StorageClass)Record[Idx++];
VD->setStorageClassAsWritten((StorageClass)Record[Idx++]);
VD->setThreadSpecified(Record[Idx++]);
VD->setCXXDirectInitializer(Record[Idx++]);