Make constant evaluation for pointer comparisons work correctly for some uncommon cases. <rdar://problem/10962435>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154794 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 6 deletions

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 4a06e74615..4839c29976 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -5088,14 +5088,26 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
         }
       }
 
+      // The comparison here must be unsigned, and performed with the same
+      // width as the pointer.
+      // FIXME: Knowing the base is the same for the LHS and RHS isn't enough
+      // for relational operators.
+      unsigned PtrSize = Info.Ctx.getTypeSize(LHSTy);
+      uint64_t CompareLHS = LHSOffset.getQuantity();
+      uint64_t CompareRHS = RHSOffset.getQuantity();
+      assert(PtrSize <= 64 && "Unexpected pointer width");
+      uint64_t Mask = ~0ULL >> (64 - PtrSize);
+      CompareLHS &= Mask;
+      CompareRHS &= Mask;
+
       switch (E->getOpcode()) {
       default: llvm_unreachable("missing comparison operator");
-      case BO_LT: return Success(LHSOffset < RHSOffset, E);
-      case BO_GT: return Success(LHSOffset > RHSOffset, E);
-      case BO_LE: return Success(LHSOffset <= RHSOffset, E);
-      case BO_GE: return Success(LHSOffset >= RHSOffset, E);
-      case BO_EQ: return Success(LHSOffset == RHSOffset, E);
-      case BO_NE: return Success(LHSOffset != RHSOffset, E);
+      case BO_LT: return Success(CompareLHS < CompareRHS, E);
+      case BO_GT: return Success(CompareLHS > CompareRHS, E);
+      case BO_LE: return Success(CompareLHS <= CompareRHS, E);
+      case BO_GE: return Success(CompareLHS >= CompareRHS, E);
+      case BO_EQ: return Success(CompareLHS == CompareRHS, E);
+      case BO_NE: return Success(CompareLHS != CompareRHS, E);
       }
     }
   }