Add codegen support for __null

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@61314 91177308-0d34-0410-b5e6-96231b3b80d8

lib/AST/ExprConstant.cpp

@@ -416,6 +416,12 @@ public:
     return true;
   }
   
+  bool VisitGNUNullExpr(const GNUNullExpr *E) {
+    Result = APSInt::getNullValue(getIntTypeSizeInBits(E->getType()));
+    Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
+    return true;
+  }
+    
   bool VisitCXXZeroInitValueExpr(const CXXZeroInitValueExpr *E) {
     Result = APSInt::getNullValue(getIntTypeSizeInBits(E->getType()));
     Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());

lib/CodeGen/CGExprScalar.cpp

@@ -113,6 +113,9 @@ public:
   Value *VisitCXXZeroInitValueExpr(const CXXZeroInitValueExpr *E) {
     return llvm::Constant::getNullValue(ConvertType(E->getType()));
   }
+  Value *VisitGNUNullExpr(const GNUNullExpr *E) {
+    return llvm::Constant::getNullValue(ConvertType(E->getType()));
+  }
   Value *VisitTypesCompatibleExpr(const TypesCompatibleExpr *E) {
     return llvm::ConstantInt::get(ConvertType(E->getType()),
                                   CGF.getContext().typesAreCompatible(

test/CodeGenCXX/__null.cpp

@@ -0,0 +1,9 @@
+// RUN: clang %s -emit-llvm -o %t
+
+int* a = __null;
+int b = __null;
+
+void f() {
+  int* c = __null;
+  int d = __null;
+}

test/SemaCXX/__null.cpp

@@ -8,4 +8,7 @@ void f() {
 
   // Verify statically that __null is the right size
   int a[sizeof(typeof(__null)) == sizeof(void*)? 1 : -1];
+  
+  // Verify that null is evaluated as 0.
+  int b[__null ? -1 : 1];
 }