[OpenCL] Correct NULL constant handling after applying default AS

[Anastasia]

Summary

In OpenCL2.0 s6.5 all pointers are implicitly in generic address space unless address space is explicitly specified.

Correct the behavior of NULL constant detection - generic AS void pointer should be accepted as a valid NULL constant.

[Anastasia]

r255346

lib/AST/Expr.cpp

Expr::isNullPointerConstant(ASTContext &Ctx,
   }
 
   // Strip off a cast to void*, if it exists. Except in C++.
   if (const ExplicitCastExpr *CE = dyn_cast<ExplicitCastExpr>(this)) {
     if (!Ctx.getLangOpts().CPlusPlus) {
       // Check that it is a cast to void*.
       if (const PointerType *PT = CE->getType()->getAs<PointerType>()) {
         QualType Pointee = PT->getPointeeType();
-        if (!Pointee.hasQualifiers() &&
-            Pointee->isVoidType() &&                              // to void*
-            CE->getSubExpr()->getType()->isIntegerType())         // from int.
+        Qualifiers Q = Pointee.getQualifiers();
+        // in OpenCL v2.0 generic address space acts as a placeholder
+        // and should be ignored.
+        bool IsASValid = true;
+        if (Ctx.getLangOpts().OpenCLVersion >= 200) {
+          if (Pointee.getAddressSpace() == LangAS::opencl_generic)
+            Q.removeAddressSpace();
+          else
+            IsASValid = false;
+        }
+
+        if (IsASValid && !Q.hasQualifiers() &&
+            Pointee->isVoidType() &&                      // to void*
+            CE->getSubExpr()->getType()->isIntegerType()) // from int.
           return CE->getSubExpr()->isNullPointerConstant(Ctx, NPC);
       }
     }
   } else if (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(this)) {
     // Ignore the ImplicitCastExpr type entirely.
     return ICE->getSubExpr()->isNullPointerConstant(Ctx, NPC);
   } else if (const ParenExpr *PE = dyn_cast<ParenExpr>(this)) {
     // Accept ((void*)0) as a null pointer constant, as many other

lib/Sema/SemaExpr.cpp

if (Context.typesAreCompatible(LCanPointeeTy.getUnqualifiedType(),
           && !LHSIsNull && !RHSIsNull)
         diagnoseFunctionPointerToVoidComparison(*this, Loc, LHS, RHS,
                                                 /*isError*/false);
     } else {
       // Invalid
       diagnoseDistinctPointerComparison(*this, Loc, LHS, RHS, /*isError*/false);
     }
     if (LCanPointeeTy != RCanPointeeTy) {
-      if (getLangOpts().OpenCL) {
+      // Treat NULL constant as a special case in OpenCL
+      if (getLangOpts().OpenCL && !LHSIsNull && !RHSIsNull) {
         const PointerType *LHSPtr = LHSType->getAs<PointerType>();
         if (!LHSPtr->isAddressSpaceOverlapping(*RHSType->getAs<PointerType>())) {
           Diag(Loc,
                diag::err_typecheck_op_on_nonoverlapping_address_space_pointers)
               << LHSType << RHSType << 0 /* comparison */
               << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
         }
       }

test/SemaOpenCL/null_literal.cl

+// RUN: %clang_cc1 -verify %s
+// RUN: %clang_cc1 -cl-std=CL2.0 -DCL20 -verify %s
+
+#define NULL ((void*)0)
+
+void foo(){
+
+global int* ptr1 = NULL;
+
+global int* ptr2 = (global void*)0;
+
+constant int* ptr3 = NULL;
+
+constant int* ptr4 = (global void*)0; // expected-error{{initializing '__constant int *' with an expression of type '__global void *' changes address space of pointer}}
+
+#ifdef CL20
+// accept explicitly pointer to generic address space in OpenCL v2.0
+global int* ptr5 = (generic void*)0;
+#endif
+
+global int* ptr6 = (local void*)0; // expected-error{{initializing '__global int *' with an expression of type '__local void *' changes address space of pointer}}
+
+bool cmp = ptr1 == NULL;
+
+cmp = ptr1 == (local void*)0; // expected-error{{comparison between  ('__global int *' and '__local void *') which are pointers to non-overlapping address spaces}}
+
+cmp = ptr3 == NULL;
+
+}