bool proveNoWrapByVaryingStart(const SCEV *Start, const SCEV *Step,
const Loop *L);
+ /// Try to prove NSW or NUW on \p AR relying on ConstantRange manipulation.
+ SCEV::NoWrapFlags proveNoWrapViaConstantRanges(const SCEVAddRecExpr *AR);
+
bool isMonotonicPredicateImpl(const SCEVAddRecExpr *LHS,
ICmpInst::Predicate Pred, bool &Increasing);
unsigned BitWidth = getTypeSizeInBits(AR->getType());
const Loop *L = AR->getLoop();
+ if (!AR->hasNoUnsignedWrap()) {
+ auto NewFlags = proveNoWrapViaConstantRanges(AR);
+ const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(NewFlags);
+ }
+
// If we have special knowledge that this addrec won't overflow,
// we don't need to do any further analysis.
if (AR->hasNoUnsignedWrap())
unsigned BitWidth = getTypeSizeInBits(AR->getType());
const Loop *L = AR->getLoop();
+ if (!AR->hasNoSignedWrap()) {
+ auto NewFlags = proveNoWrapViaConstantRanges(AR);
+ const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(NewFlags);
+ }
+
// If we have special knowledge that this addrec won't overflow,
// we don't need to do any further analysis.
if (AR->hasNoSignedWrap())
};
} // end anonymous namespace
+SCEV::NoWrapFlags
+ScalarEvolution::proveNoWrapViaConstantRanges(const SCEVAddRecExpr *AR) {
+ if (!AR->isAffine())
+ return SCEV::FlagAnyWrap;
+
+ typedef OverflowingBinaryOperator OBO;
+ SCEV::NoWrapFlags Result = SCEV::FlagAnyWrap;
+
+ if (!AR->hasNoSignedWrap()) {
+ ConstantRange AddRecRange = getSignedRange(AR);
+ ConstantRange IncRange = getSignedRange(AR->getStepRecurrence(*this));
+
+ auto NSWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
+ Instruction::Add, IncRange, OBO::NoSignedWrap);
+ if (NSWRegion.contains(AddRecRange))
+ Result = ScalarEvolution::setFlags(Result, SCEV::FlagNSW);
+ }
+
+ if (!AR->hasNoUnsignedWrap()) {
+ ConstantRange AddRecRange = getUnsignedRange(AR);
+ ConstantRange IncRange = getUnsignedRange(AR->getStepRecurrence(*this));
+
+ auto NUWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
+ Instruction::Add, IncRange, OBO::NoUnsignedWrap);
+ if (NUWRegion.contains(AddRecRange))
+ Result = ScalarEvolution::setFlags(Result, SCEV::FlagNUW);
+ }
+
+ return Result;
+}
+
const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) {
const Loop *L = LI.getLoopFor(PN->getParent());
if (!L || L->getHeader() != PN->getParent())
leave:
ret void
}
+
+define void @f2(i1 %c) {
+; CHECK-LABEL: Classifying expressions for: @f2
+entry:
+ %start = select i1 %c, i32 127, i32 0
+ %step = select i1 %c, i32 -1, i32 1
+ br label %loop
+
+loop:
+ %loop.iv = phi i32 [ 0, %entry ], [ %loop.iv.inc, %loop ]
+ %iv = phi i32 [ %start, %entry ], [ %iv.next, %loop ]
+ %iv.sext = sext i32 %iv to i64
+ %iv.next = add i32 %iv, %step
+; CHECK: %iv.sext = sext i32 %iv to i64
+; CHECK-NEXT: --> {(sext i32 %start to i64),+,(sext i32 %step to i64)}<nsw><%loop>
+ %loop.iv.inc = add i32 %loop.iv, 1
+ %be.cond = icmp ne i32 %loop.iv.inc, 128
+ br i1 %be.cond, label %loop, label %leave
+
+leave:
+ ret void
+}
+
+define void @f3(i1 %c) {
+; CHECK-LABEL: Classifying expressions for: @f3
+entry:
+
+; NB! the i16 type (as opposed to i32), the choice of the constant 509
+; and the trip count are all related and not arbitrary. We want an
+; add recurrence that will look like it can unsign-overflow *unless*
+; SCEV is able to see the correlation between the two selects feeding
+; into the initial value and the step increment.
+
+ %start = select i1 %c, i16 1000, i16 0
+ %step = select i1 %c, i16 1, i16 509
+ br label %loop
+
+loop:
+ %loop.iv = phi i16 [ 0, %entry ], [ %loop.iv.inc, %loop ]
+ %iv = phi i16 [ %start, %entry ], [ %iv.next, %loop ]
+ %iv.zext = zext i16 %iv to i64
+; CHECK: %iv.zext = zext i16 %iv to i64
+; CHECK-NEXT: --> {(zext i16 %start to i64),+,(zext i16 %step to i64)}<nuw><%loop>
+ %iv.next = add i16 %iv, %step
+ %loop.iv.inc = add i16 %loop.iv, 1
+ %be.cond = icmp ne i16 %loop.iv.inc, 128
+ br i1 %be.cond, label %loop, label %leave
+
+leave:
+ ret void
+}