Left shifts of negative values are defined if -fwrapv is set

This means we shouldn't emit ubsan detection code or warn.
Fixes PR25552.

llvm-svn: 278786

2 files changed, 3 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index f3936873359..700b5374ad9 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -2714,7 +2714,8 @@ Value *ScalarExprEmitter::EmitShl(const BinOpInfo &Ops) {
     RHS = Builder.CreateIntCast(RHS, Ops.LHS->getType(), false, "sh_prom");
 
   bool SanitizeBase = CGF.SanOpts.has(SanitizerKind::ShiftBase) &&
-                      Ops.Ty->hasSignedIntegerRepresentation();
+                      Ops.Ty->hasSignedIntegerRepresentation() &&
+                      !CGF.getLangOpts().isSignedOverflowDefined();
   bool SanitizeExponent = CGF.SanOpts.has(SanitizerKind::ShiftExponent);
   // OpenCL 6.3j: shift values are effectively % word size of LHS.
   if (CGF.getLangOpts().OpenCL)
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 78fa995e256..41c8a4c52a1 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -8670,7 +8670,7 @@ static void DiagnoseBadShiftValues(Sema& S, ExprResult &LHS, ExprResult &RHS,
 
   // If LHS does not have a signed type and non-negative value
   // then, the behavior is undefined. Warn about it.
-  if (Left.isNegative()) {
+  if (Left.isNegative() && !S.getLangOpts().isSignedOverflowDefined()) {
     S.DiagRuntimeBehavior(Loc, LHS.get(),
                           S.PDiag(diag::warn_shift_lhs_negative)
                             << LHS.get()->getSourceRange());