getMulExpr(WideMaxBECount,
getZeroExtendExpr(Step, WideTy)));
if (SAdd == OperandExtendedAdd) {
- // Cache knowledge of AR NSW, which is propagated to this AddRec.
- const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
+ // If AR wraps around then
+ //
+ // abs(Step) * MaxBECount > unsigned-max(AR->getType())
+ // => SAdd != OperandExtendedAdd
+ //
+ // Thus (AR is not NW => SAdd != OperandExtendedAdd) <=>
+ // (SAdd == OperandExtendedAdd => AR is NW)
+
+ const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
+
// Return the expression with the addrec on the outside.
return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this),
getZeroExtendExpr(Step, Ty),
--- /dev/null
+; RUN: opt -analyze -scalar-evolution -scalar-evolution < %s | FileCheck %s
+
+define void @bad.nsw() {
+; CHECK-LABEL: Classifying expressions for: @bad.nsw
+; CHECK-LABEL: Classifying expressions for: @bad.nsw
+ entry:
+ br label %loop
+
+ loop:
+ %i = phi i8 [ -1, %entry ], [ %i.inc, %loop ]
+; CHECK: %i = phi i8 [ -1, %entry ], [ %i.inc, %loop ]
+; CHECK-NEXT: --> {-1,+,-128}<nw><%loop>
+; CHECK-NOT: --> {-1,+,-128}<nsw><%loop>
+
+ %counter = phi i8 [ 0, %entry ], [ %counter.inc, %loop ]
+
+ %i.inc = add i8 %i, -128
+ %i.sext = sext i8 %i to i16
+
+ %counter.inc = add i8 %counter, 1
+ %continue = icmp eq i8 %counter, 1
+ br i1 %continue, label %exit, label %loop
+
+ exit:
+ ret void
+}