Eliminate the branching in QualType::getTypePtr() by providing a

common base for ExtQuals and Type that stores the underlying type
pointer. This results in a 2% performance win for -emit-llvm on a
typical C file, with 1% memory growth in the AST.

Note that there is an API change in this optimization:
QualType::getTypePtr() can no longer be invoked on a NULL
QualType. If the QualType might be NULL, use
QualType::getTypePtrOrNull(). I've audited all uses of getTypePtr() in
the code base and changed the appropriate uses over to
getTypePtrOrNull(). 

A future optimization opportunity would be to distinguish between
cast/dyn_cast and cast_or_null/dyn_cast_or_null; for the former, we
could use getTypePtr() rather than getTypePtrOrNull(), to take another
branch out of the cast/dyn_cast implementation.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@121489 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 1 deletions

diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 4e0a7b783b..5fe95bfed4 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -2772,6 +2772,9 @@ QualType ASTReader::ReadTypeRecord(unsigned Index) {
     }
     QualType PointeeType = GetType(Record[0]);
     QualType ClassType = GetType(Record[1]);
+    if (PointeeType.isNull() || ClassType.isNull())
+      return QualType();
+    
     return Context->getMemberPointerType(PointeeType, ClassType.getTypePtr());
   }
 
@@ -4368,7 +4371,10 @@ ASTReader::ReadNestedNameSpecifier(const RecordData &Record, unsigned &Idx) {
 
     case NestedNameSpecifier::TypeSpec:
     case NestedNameSpecifier::TypeSpecWithTemplate: {
-      Type *T = GetType(Record[Idx++]).getTypePtr();
+      Type *T = GetType(Record[Idx++]).getTypePtrOrNull();
+      if (!T)
+        return 0;
+      
       bool Template = Record[Idx++];
       NNS = NestedNameSpecifier::Create(*Context, Prev, Template, T);
       break;