diff options
| author | Richard Smith <richard-llvm@metafoo.co.uk> | 2012-02-08 06:14:53 +0000 |
|---|---|---|
| committer | Richard Smith <richard-llvm@metafoo.co.uk> | 2012-02-08 06:14:53 +0000 |
| commit | 925d8e7c0f18e03dc4bc634b3c6c1ec09373d993 (patch) | |
| tree | 2ac97fec24c62997c666aaa809b4125557aa1fd6 /lib/AST/ExprConstant.cpp | |
| parent | 31a3702618ab49578542cffee20ba0c8859b9d1e (diff) | |
Implement the agreed resolution to DR1457: a signed left shift of a 1 bit into
the sign bit doesn't have undefined behavior, but a signed left shift of a 1 bit
out of the sign bit still does. As promised to Howard :)
The suppression of the potential constant expression checking in system headers
is also removed, since the problem it was working around is gone.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150059 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/AST/ExprConstant.cpp')
| -rw-r--r-- | lib/AST/ExprConstant.cpp | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp index e33d22a4aa..410406788d 100644 --- a/lib/AST/ExprConstant.cpp +++ b/lib/AST/ExprConstant.cpp @@ -4704,12 +4704,11 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) { << RHS << E->getType() << LHS.getBitWidth(); } else if (LHS.isSigned()) { // C++11 [expr.shift]p2: A signed left shift must have a non-negative - // operand, and must not overflow. + // operand, and must not overflow the corresponding unsigned type. if (LHS.isNegative()) CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS; - else if (LHS.countLeadingZeros() <= SA) - HandleOverflow(Info, E, LHS.extend(LHS.getBitWidth() + SA) << SA, - E->getType()); + else if (LHS.countLeadingZeros() < SA) + CCEDiag(E, diag::note_constexpr_lshift_discards); } return Success(LHS << SA, E); |