constexpr: evaluation support for nullptr comparisons.

llvm-svn: 150521

2 files changed, 24 insertions, 3 deletions

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 787e722a7cb..e33ca6dc650 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -4612,6 +4612,16 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
     return Success(E->getOpcode() == BO_EQ ? Equal : !Equal, E);
   }
 
+  if (LHSTy->isNullPtrType()) {
+    assert(E->isComparisonOp() && "unexpected nullptr operation");
+    assert(RHSTy->isNullPtrType() && "missing pointer conversion");
+    // C++11 [expr.rel]p4, [expr.eq]p3: If two operands of type std::nullptr_t
+    // are compared, the result is true of the operator is <=, >= or ==, and
+    // false otherwise.
+    BinaryOperator::Opcode Opcode = E->getOpcode();
+    return Success(Opcode == BO_EQ || Opcode == BO_LE || Opcode == BO_GE, E);
+  }
+
   if (!LHSTy->isIntegralOrEnumerationType() ||
       !RHSTy->isIntegralOrEnumerationType()) {
     // We can't continue from here for non-integral types.
diff --git a/clang/test/SemaCXX/nullptr.cpp b/clang/test/SemaCXX/nullptr.cpp
index 0e6771b57fc..91757cf51ed 100644
--- a/clang/test/SemaCXX/nullptr.cpp
+++ b/clang/test/SemaCXX/nullptr.cpp
@@ -113,15 +113,26 @@ int array0[__is_scalar(nullptr_t)? 1 : -1];
 int array1[__is_pod(nullptr_t)? 1 : -1];
 int array2[sizeof(nullptr_t) == sizeof(void*)? 1 : -1];
 
-// FIXME: when we implement constexpr, this will be testable.
-#if 0
 int relational0[nullptr < nullptr? -1 : 1];
 int relational1[nullptr > nullptr? -1 : 1];
 int relational2[nullptr <= nullptr? 1 : -1];
 int relational3[nullptr >= nullptr? 1 : -1];
 int equality[nullptr == nullptr? 1 : -1];
 int inequality[nullptr != nullptr? -1 : 1];
-#endif
+
+int relational0_a[0 < nullptr? -1 : 1];
+int relational1_a[0 > nullptr? -1 : 1];
+int relational2_a[0 <= nullptr? 1 : -1];
+int relational3_a[0 >= nullptr? 1 : -1];
+int equality_a[0 == nullptr? 1 : -1];
+int inequality_a[0 != nullptr? -1 : 1];
+
+int relationalnullptr_b[nullptr < 0? -1 : 1];
+int relational1_b[nullptr > 0? -1 : 1];
+int relational2_b[nullptr <= 0? 1 : -1];
+int relational3_b[nullptr >= 0? 1 : -1];
+int equality_b[nullptr == 0? 1 : -1];
+int inequality_b[nullptr != 0? -1 : 1];
 
 namespace overloading {
   int &f1(int*);