Per Richard's comments on r154794, add the checks necessary to handle constant-folding relational comparisons safely in case the user is using -fwrapv or equivalent.
llvm-svn: 154849
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 4839c29..66a88b0 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -5090,8 +5090,6 @@
// 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();
@@ -5100,6 +5098,19 @@
CompareLHS &= Mask;
CompareRHS &= Mask;
+ // If there is a base and this is a relational operator, we can only
+ // compare pointers within the object in question; otherwise, the result
+ // depends on where the object is located in memory.
+ if (!LHSValue.Base.isNull() && E->isRelationalOp()) {
+ QualType BaseTy = getType(LHSValue.Base);
+ if (BaseTy->isIncompleteType())
+ return Error(E);
+ CharUnits Size = Info.Ctx.getTypeSizeInChars(BaseTy);
+ uint64_t OffsetLimit = Size.getQuantity();
+ if (CompareLHS > OffsetLimit || CompareRHS > OffsetLimit)
+ return Error(E);
+ }
+
switch (E->getOpcode()) {
default: llvm_unreachable("missing comparison operator");
case BO_LT: return Success(CompareLHS < CompareRHS, E);