Reduce the number of allocations required for AST attributes. In test cases,...

Reduce the number of allocations required for AST attributes. In test cases, the max resident memory changed from 65760k to 64476k which is 1.9% improvement. Allocations in grow_pod changed from 8847 to 4872 according to tcmalloc heap profiler. Overall running time remained the same.

Patch by Eugene Kosov

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@278812 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/AttrIterator.h

@@ -39,8 +39,7 @@ void operator delete[](void *Ptr, const clang::ASTContext &C, size_t);
 namespace clang {
 
 /// AttrVec - A vector of Attr, which is how they are stored on the AST.
-typedef SmallVector<Attr*, 2> AttrVec;
-typedef SmallVector<const Attr*, 2> ConstAttrVec;
+typedef SmallVector<Attr *, 4> AttrVec;
 
 /// specific_attr_iterator - Iterates over a subrange of an AttrVec, only
 /// providing attributes that are of a specific type.