Track in the AST whether the operand to a UnaryOperator can overflow and then use that logic when evaluating constant expressions and emitting codegen.
llvm-svn: 322074
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index c462150..668c572 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -162,13 +162,13 @@
// we can elide the overflow check.
if (!Op.mayHaveIntegerOverflow())
return true;
-
- // If a unary op has a widened operand, the op cannot overflow.
- if (const auto *UO = dyn_cast<UnaryOperator>(Op.E))
- return IsWidenedIntegerOp(Ctx, UO->getSubExpr());
-
- // We usually don't need overflow checks for binops with widened operands.
- // Multiplication with promoted unsigned operands is a special case.
+
+ // If a unary op has a widened operand, the op cannot overflow.
+ if (const auto *UO = dyn_cast<UnaryOperator>(Op.E))
+ return !UO->canOverflow();
+
+ // We usually don't need overflow checks for binops with widened operands.
+ // Multiplication with promoted unsigned operands is a special case.
const auto *BO = cast<BinaryOperator>(Op.E);
auto OptionalLHSTy = getUnwidenedIntegerType(Ctx, BO->getLHS());
if (!OptionalLHSTy)
@@ -1870,13 +1870,13 @@
return Builder.CreateAdd(InVal, Amount, Name);
case LangOptions::SOB_Undefined:
if (!CGF.SanOpts.has(SanitizerKind::SignedIntegerOverflow))
- return Builder.CreateNSWAdd(InVal, Amount, Name);
- // Fall through.
- case LangOptions::SOB_Trapping:
- if (IsWidenedIntegerOp(CGF.getContext(), E->getSubExpr()))
- return Builder.CreateNSWAdd(InVal, Amount, Name);
- return EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, InVal, IsInc));
- }
+ return Builder.CreateNSWAdd(InVal, Amount, Name);
+ // Fall through.
+ case LangOptions::SOB_Trapping:
+ if (!E->canOverflow())
+ return Builder.CreateNSWAdd(InVal, Amount, Name);
+ return EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, InVal, IsInc));
+ }
llvm_unreachable("Unknown SignedOverflowBehaviorTy");
}
@@ -1952,17 +1952,15 @@
value = Builder.getTrue();
// Most common case by far: integer increment.
- } else if (type->isIntegerType()) {
- // Note that signed integer inc/dec with width less than int can't
- // overflow because of promotion rules; we're just eliding a few steps here.
- bool CanOverflow = value->getType()->getIntegerBitWidth() >=
- CGF.IntTy->getIntegerBitWidth();
- if (CanOverflow && type->isSignedIntegerOrEnumerationType()) {
- value = EmitIncDecConsiderOverflowBehavior(E, value, isInc);
- } else if (CanOverflow && type->isUnsignedIntegerType() &&
- CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) {
- value =
- EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, value, isInc));
+ } else if (type->isIntegerType()) {
+ // Note that signed integer inc/dec with width less than int can't
+ // overflow because of promotion rules; we're just eliding a few steps here.
+ if (E->canOverflow() && type->isSignedIntegerOrEnumerationType()) {
+ value = EmitIncDecConsiderOverflowBehavior(E, value, isInc);
+ } else if (E->canOverflow() && type->isUnsignedIntegerType() &&
+ CGF.SanOpts.has(SanitizerKind::UnsignedIntegerOverflow)) {
+ value =
+ EmitOverflowCheckedBinOp(createBinOpInfoFromIncDec(E, value, isInc));
} else {
llvm::Value *amt = llvm::ConstantInt::get(value->getType(), amount, true);
value = Builder.CreateAdd(value, amt, isInc ? "inc" : "dec");