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[SCEV] Distinguish between full and wrapping AddRec in proveNoWrapViaCR. #151966

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[SCEV] Distinguish between full and wrapping AddRec in proveNoWrapViaCR. #151966

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43 changes: 36 additions & 7 deletions llvm/lib/Analysis/ScalarEvolution.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5092,9 +5092,29 @@ ScalarEvolution::proveNoWrapViaConstantRanges(const SCEVAddRecExpr *AR) {
}

if (!AR->hasNoUnsignedWrap()) {
ConstantRange AddRecRange = getUnsignedRange(AR);
ConstantRange IncRange = getUnsignedRange(AR->getStepRecurrence(*this));

const SCEVAddRecExpr *NewAR = AR;
unsigned BitWidth = getTypeSizeInBits(AR->getType());
// For integer AddRecs, try to evaluate the AddRec in a type one bit wider
// than the original type, to be able to differentiate between the AddRec
// hitting the full range or wrapping.
const SCEV *Step = AR->getStepRecurrence(*this);
if (AR->getType()->isIntegerTy() && isKnownNonNegative(Step)) {
Type *WiderTy = IntegerType::get(getContext(), BitWidth + 1);
NewAR = cast<SCEVAddRecExpr>(
getAddRecExpr(getSignExtendExpr(AR->getStart(), WiderTy),
getZeroExtendExpr(Step, WiderTy), AR->getLoop(),
AR->getNoWrapFlags()));
ConstantRange AddRecRange = getUnsignedRange(NewAR);
// If the wider AddRec range matches the original range after stripping
// the top bit, the original AddRec does not self-wrap.
if (AddRecRange !=
AddRecRange.truncate(BitWidth).zeroExtend(BitWidth + 1))
NewAR = AR;
}
ConstantRange AddRecRange = getUnsignedRange(NewAR);
ConstantRange IncRange = getUnsignedRange(Step);
if (NewAR != AR)
IncRange = IncRange.zeroExtend(getTypeSizeInBits(NewAR->getType()));
auto NUWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
Instruction::Add, IncRange, OBO::NoUnsignedWrap);
if (NUWRegion.contains(AddRecRange))
Expand Down Expand Up @@ -8336,7 +8356,13 @@ const SCEV *ScalarEvolution::getPredicatedExitCount(

const SCEV *ScalarEvolution::getPredicatedBackedgeTakenCount(
const Loop *L, SmallVectorImpl<const SCEVPredicate *> &Preds) {
return getPredicatedBackedgeTakenInfo(L).getExact(L, this, &Preds);
auto *Res = getPredicatedBackedgeTakenInfo(L).getExact(L, this, &Preds);
if (!isa<SCEVCouldNotCompute>(Res) && Preds.empty()) {
auto I = BackedgeTakenCounts.find(L);
if (I != BackedgeTakenCounts.end() && !I->second.isComplete())
BackedgeTakenCounts.erase(I);
}
return Res;
}

const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L,
Expand Down Expand Up @@ -13858,7 +13884,8 @@ static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
SmallVector<const SCEVPredicate *, 4> Preds;
auto *PBT = SE->getPredicatedBackedgeTakenCount(L, Preds);
if (PBT != BTC) {
assert(!Preds.empty() && "Different predicated BTC, but no predicates");
assert((!Preds.empty() || PBT == SE->getBackedgeTakenCount(L)) &&
"Different predicated BTC, but no predicates");
OS << "Loop ";
L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
OS << ": ";
Expand All @@ -13877,7 +13904,8 @@ static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
auto *PredConstantMax =
SE->getPredicatedConstantMaxBackedgeTakenCount(L, Preds);
if (PredConstantMax != ConstantBTC) {
assert(!Preds.empty() &&
assert((!Preds.empty() ||
PredConstantMax == SE->getConstantMaxBackedgeTakenCount(L)) &&
"different predicated constant max BTC but no predicates");
OS << "Loop ";
L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
Expand All @@ -13897,7 +13925,8 @@ static void PrintLoopInfo(raw_ostream &OS, ScalarEvolution *SE,
auto *PredSymbolicMax =
SE->getPredicatedSymbolicMaxBackedgeTakenCount(L, Preds);
if (SymbolicBTC != PredSymbolicMax) {
assert(!Preds.empty() &&
assert((!Preds.empty() ||
PredSymbolicMax == SE->getSymbolicMaxBackedgeTakenCount(L)) &&
"Different predicated symbolic max BTC, but no predicates");
OS << "Loop ";
L->getHeader()->printAsOperand(OS, /*PrintType=*/false);
Expand Down
12 changes: 2 additions & 10 deletions llvm/test/Analysis/ScalarEvolution/exit-count-non-strict.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -153,26 +153,22 @@ define void @ule_from_zero_no_nuw(i32 %M, i32 %N) {
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: predicated exit count for loop: (1 + (zext i32 %M to i64))<nuw><nsw>
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-EMPTY:
; CHECK-NEXT: exit count for latch: %N
; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i32 -1
; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is %N
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: predicated symbolic max exit count for loop: (1 + (zext i32 %M to i64))<nuw><nsw>
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-EMPTY:
; CHECK-NEXT: symbolic max exit count for latch: %N
; CHECK-NEXT: Loop %loop: Predicated backedge-taken count is ((zext i32 %N to i64) umin (1 + (zext i32 %M to i64))<nuw><nsw>)
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-NEXT: Loop %loop: Predicated constant max backedge-taken count is i64 4294967295
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-NEXT: Loop %loop: Predicated symbolic max backedge-taken count is ((zext i32 %N to i64) umin (1 + (zext i32 %M to i64))<nuw><nsw>)
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-NEXT: Loop %loop: Trip multiple is 1
;
entry:
br label %loop
Expand All @@ -198,26 +194,22 @@ define void @le_from_zero_no_nuw(i32 %M, i32 %N) {
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: predicated exit count for loop: (1 + (zext i32 %M to i64))<nuw><nsw>
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-EMPTY:
; CHECK-NEXT: exit count for latch: %N
; CHECK-NEXT: Loop %loop: constant max backedge-taken count is i32 -1
; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is %N
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: predicated symbolic max exit count for loop: (1 + (zext i32 %M to i64))<nuw><nsw>
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-EMPTY:
; CHECK-NEXT: symbolic max exit count for latch: %N
; CHECK-NEXT: Loop %loop: Predicated backedge-taken count is ((zext i32 %N to i64) umin (1 + (zext i32 %M to i64))<nuw><nsw>)
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-NEXT: Loop %loop: Predicated constant max backedge-taken count is i64 4294967295
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-NEXT: Loop %loop: Predicated symbolic max backedge-taken count is ((zext i32 %N to i64) umin (1 + (zext i32 %M to i64))<nuw><nsw>)
; CHECK-NEXT: Predicates:
; CHECK-NEXT: {0,+,1}<%loop> Added Flags: <nusw>
; CHECK-NEXT: Loop %loop: Trip multiple is 1
;
entry:
br label %loop
Expand Down
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