From c45061bd0c0fdad4df8eea7e9e5af186d11427e5 Mon Sep 17 00:00:00 2001 From: Eli Friedman Date: Mon, 31 Oct 2011 22:54:30 +0000 Subject: [PATCH] Some minor comment changes in constant-folding comparisons. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@143391 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/AST/ExprConstant.cpp | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp index 5a65038a5f..574474df91 100644 --- a/lib/AST/ExprConstant.cpp +++ b/lib/AST/ExprConstant.cpp @@ -1983,12 +1983,13 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) { return false; // A constant address may compare equal to the address of a symbol. // The one exception is that address of an object cannot compare equal - // to the null pointer. + // to a null pointer constant. if ((!LHSValue.Base && !LHSValue.Offset.isZero()) || (!RHSValue.Base && !RHSValue.Offset.isZero())) return false; // It's implementation-defined whether distinct literals will have - // distinct addresses. We define it to be unspecified. + // distinct addresses. In clang, we do not guarantee the addresses are + // distinct. if (IsLiteralLValue(LHSValue) || IsLiteralLValue(RHSValue)) return false; // We can't tell whether weak symbols will end up pointing to the same @@ -1996,6 +1997,9 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) { if (IsWeakLValue(LHSValue) || IsWeakLValue(RHSValue)) return false; // Pointers with different bases cannot represent the same object. + // (Note that clang defaults to -fmerge-all-constants, which can + // lead to inconsistent results for comparisons involving the address + // of a constant; this generally doesn't matter in practice.) return Success(E->getOpcode() == BO_NE, E); } -- 2.40.0