"derived loop"),
cl::init(100));
-static RegisterPass<ScalarEvolution>
-R("scalar-evolution", "Scalar Evolution Analysis", false, true);
+INITIALIZE_PASS(ScalarEvolution, "scalar-evolution",
+ "Scalar Evolution Analysis", false, true);
char ScalarEvolution::ID = 0;
//===----------------------------------------------------------------------===//
// Fold if the operand is constant.
if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
return getConstant(
- cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(), Ty)));
+ cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(),
+ getEffectiveSCEVType(Ty))));
// trunc(trunc(x)) --> trunc(x)
if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
return getAddRecExpr(Operands, AddRec->getLoop());
}
- // The cast wasn't folded; create an explicit cast node.
- // Recompute the insert position, as it may have been invalidated.
- if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
+ // As a special case, fold trunc(undef) to undef. We don't want to
+ // know too much about SCEVUnknowns, but this special case is handy
+ // and harmless.
+ if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
+ if (isa<UndefValue>(U->getValue()))
+ return getSCEV(UndefValue::get(Ty));
+
+ // The cast wasn't folded; create an explicit cast node. We can reuse
+ // the existing insert position since if we get here, we won't have
+ // made any changes which would invalidate it.
SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
Op, Ty);
UniqueSCEVs.InsertNode(S, IP);
Ty = getEffectiveSCEVType(Ty);
// Fold if the operand is constant.
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op)) {
- const Type *IntTy = getEffectiveSCEVType(Ty);
- Constant *C = ConstantExpr::getZExt(SC->getValue(), IntTy);
- if (IntTy != Ty) C = ConstantExpr::getIntToPtr(C, Ty);
- return getConstant(cast<ConstantInt>(C));
- }
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
+ return getConstant(
+ cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(),
+ getEffectiveSCEVType(Ty))));
// zext(zext(x)) --> zext(x)
if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
Ty = getEffectiveSCEVType(Ty);
// Fold if the operand is constant.
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op)) {
- const Type *IntTy = getEffectiveSCEVType(Ty);
- Constant *C = ConstantExpr::getSExt(SC->getValue(), IntTy);
- if (IntTy != Ty) C = ConstantExpr::getIntToPtr(C, Ty);
- return getConstant(cast<ConstantInt>(C));
- }
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
+ return getConstant(
+ cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(),
+ getEffectiveSCEVType(Ty))));
// sext(sext(x)) --> sext(x)
if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
return getAddRecExpr(Ops, AR->getLoop());
}
+ // As a special case, fold anyext(undef) to undef. We don't want to
+ // know too much about SCEVUnknowns, but this special case is handy
+ // and harmless.
+ if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Op))
+ if (isa<UndefValue>(U->getValue()))
+ return getSCEV(UndefValue::get(Ty));
+
// If the expression is obviously signed, use the sext cast value.
if (isa<SCEVSMaxExpr>(Op))
return SExt;
ScalarEvolution &SE) {
bool Interesting = false;
- // Iterate over the add operands.
- for (unsigned i = 0, e = NumOperands; i != e; ++i) {
+ // Iterate over the add operands. They are sorted, with constants first.
+ unsigned i = 0;
+ while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
+ ++i;
+ // Pull a buried constant out to the outside.
+ if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
+ Interesting = true;
+ AccumulatedConstant += Scale * C->getValue()->getValue();
+ }
+
+ // Next comes everything else. We're especially interested in multiplies
+ // here, but they're in the middle, so just visit the rest with one loop.
+ for (; i != NumOperands; ++i) {
const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
APInt NewScale =
Interesting = true;
}
}
- } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
- // Pull a buried constant out to the outside.
- if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
- Interesting = true;
- AccumulatedConstant += Scale * C->getValue()->getValue();
} else {
// An ordinary operand. Update the map.
std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
// If we have an add, expand the add operands onto the end of the operands
// list.
- Ops.insert(Ops.end(), Add->op_begin(), Add->op_end());
Ops.erase(Ops.begin()+Idx);
+ Ops.append(Add->op_begin(), Add->op_end());
DeletedAdd = true;
}
AddRec->op_end());
AddRecOps[0] = getAddExpr(LIOps);
- // It's tempting to propagate NUW/NSW flags here, but nuw/nsw addition
- // is not associative so this isn't necessarily safe.
- const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop);
+ // Build the new addrec. Propagate the NUW and NSW flags if both the
+ // outer add and the inner addrec are guaranteed to have no overflow.
+ const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop,
+ HasNUW && AddRec->hasNoUnsignedWrap(),
+ HasNSW && AddRec->hasNoSignedWrap());
// If all of the other operands were loop invariant, we are done.
if (Ops.size() == 1) return NewRec;
AddRec->op_end());
for (unsigned i = 0, e = OtherAddRec->getNumOperands(); i != e; ++i) {
if (i >= NewOps.size()) {
- NewOps.insert(NewOps.end(), OtherAddRec->op_begin()+i,
+ NewOps.append(OtherAddRec->op_begin()+i,
OtherAddRec->op_end());
break;
}
while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
// If we have an mul, expand the mul operands onto the end of the operands
// list.
- Ops.insert(Ops.end(), Mul->op_begin(), Mul->op_end());
Ops.erase(Ops.begin()+Idx);
+ Ops.append(Mul->op_begin(), Mul->op_end());
DeletedMul = true;
}
for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
- // It's tempting to propagate the NSW flag here, but nsw multiplication
- // is not associative so this isn't necessarily safe.
+ // Build the new addrec. Propagate the NUW and NSW flags if both the
+ // outer mul and the inner addrec are guaranteed to have no overflow.
const SCEV *NewRec = getAddRecExpr(NewOps, AddRec->getLoop(),
HasNUW && AddRec->hasNoUnsignedWrap(),
- /*HasNSW=*/false);
+ HasNSW && AddRec->hasNoSignedWrap());
// If all of the other operands were loop invariant, we are done.
if (Ops.size() == 1) return NewRec;
Operands.push_back(Start);
if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
if (StepChrec->getLoop() == L) {
- Operands.insert(Operands.end(), StepChrec->op_begin(),
- StepChrec->op_end());
+ Operands.append(StepChrec->op_begin(), StepChrec->op_end());
return getAddRecExpr(Operands, L);
}
if (Idx < Ops.size()) {
bool DeletedSMax = false;
while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
- Ops.insert(Ops.end(), SMax->op_begin(), SMax->op_end());
Ops.erase(Ops.begin()+Idx);
+ Ops.append(SMax->op_begin(), SMax->op_end());
DeletedSMax = true;
}
if (Idx < Ops.size()) {
bool DeletedUMax = false;
while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
- Ops.insert(Ops.end(), UMax->op_begin(), UMax->op_end());
Ops.erase(Ops.begin()+Idx);
+ Ops.append(UMax->op_begin(), UMax->op_end());
DeletedUMax = true;
}
///
const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS,
const SCEV *RHS) {
+ // Fast path: X - X --> 0.
+ if (LHS == RHS)
+ return getConstant(LHS->getType(), 0);
+
// X - Y --> X + -Y
return getAddExpr(LHS, getNegativeSCEV(RHS));
}
///
const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
- bool InBounds = GEP->isInBounds();
+ // Don't blindly transfer the inbounds flag from the GEP instruction to the
+ // Add expression, because the Instruction may be guarded by control flow
+ // and the no-overflow bits may not be valid for the expression in any
+ // context.
+
const Type *IntPtrTy = getEffectiveSCEVType(GEP->getType());
Value *Base = GEP->getOperand(0);
// Don't attempt to analyze GEPs over unsized objects.
if (const StructType *STy = dyn_cast<StructType>(*GTI++)) {
// For a struct, add the member offset.
unsigned FieldNo = cast<ConstantInt>(Index)->getZExtValue();
- TotalOffset = getAddExpr(TotalOffset,
- getOffsetOfExpr(STy, FieldNo),
- /*HasNUW=*/false, /*HasNSW=*/InBounds);
+ const SCEV *FieldOffset = getOffsetOfExpr(STy, FieldNo);
+
+ // Add the field offset to the running total offset.
+ TotalOffset = getAddExpr(TotalOffset, FieldOffset);
} else {
// For an array, add the element offset, explicitly scaled.
- const SCEV *LocalOffset = getSCEV(Index);
+ const SCEV *ElementSize = getSizeOfExpr(*GTI);
+ const SCEV *IndexS = getSCEV(Index);
// Getelementptr indices are signed.
- LocalOffset = getTruncateOrSignExtend(LocalOffset, IntPtrTy);
- // Lower "inbounds" GEPs to NSW arithmetic.
- LocalOffset = getMulExpr(LocalOffset, getSizeOfExpr(*GTI),
- /*HasNUW=*/false, /*HasNSW=*/InBounds);
- TotalOffset = getAddExpr(TotalOffset, LocalOffset,
- /*HasNUW=*/false, /*HasNSW=*/InBounds);
+ IndexS = getTruncateOrSignExtend(IndexS, IntPtrTy);
+
+ // Multiply the index by the element size to compute the element offset.
+ const SCEV *LocalOffset = getMulExpr(IndexS, ElementSize);
+
+ // Add the element offset to the running total offset.
+ TotalOffset = getAddExpr(TotalOffset, LocalOffset);
}
}
- return getAddExpr(getSCEV(Base), TotalOffset,
- /*HasNUW=*/false, /*HasNSW=*/InBounds);
+
+ // Get the SCEV for the GEP base.
+ const SCEV *BaseS = getSCEV(Base);
+
+ // Add the total offset from all the GEP indices to the base.
+ return getAddExpr(BaseS, TotalOffset);
}
/// GetMinTrailingZeros - Determine the minimum number of zero bits that S is
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
if (!C->getValue()->isZero())
ConservativeResult =
- ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0));
+ ConservativeResult.intersectWith(
+ ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
// TODO: non-affine addrec
if (AddRec->isAffine()) {
Operator *U = cast<Operator>(V);
switch (Opcode) {
case Instruction::Add:
- // Don't transfer the NSW and NUW bits from the Add instruction to the
- // Add expression, because the Instruction may be guarded by control
- // flow and the no-overflow bits may not be valid for the expression in
- // any context.
return getAddExpr(getSCEV(U->getOperand(0)),
getSCEV(U->getOperand(1)));
case Instruction::Mul:
- // Don't transfer the NSW and NUW bits from the Mul instruction to the
- // Mul expression, as with Add.
return getMulExpr(getSCEV(U->getOperand(0)),
getSCEV(U->getOperand(1)));
case Instruction::UDiv:
ConstantEvolutionLoopExitValue.erase(PN);
}
+ // If there's a SCEVUnknown tying this value into the SCEV
+ // space, remove it from the folding set map. The SCEVUnknown
+ // object and any other SCEV objects which reference it
+ // (transitively) remain allocated, effectively leaked until
+ // the underlying BumpPtrAllocator is freed.
+ //
+ // This permits SCEV pointers to be used as keys in maps
+ // such as the ValuesAtScopes map.
+ FoldingSetNodeID ID;
+ ID.AddInteger(scUnknown);
+ ID.AddPointer(I);
+ void *IP;
+ if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
+ UniqueSCEVs.RemoveNode(S);
+
+ // This isn't necessary, but we might as well remove the
+ // value from the ValuesAtScopes map too.
+ ValuesAtScopes.erase(S);
+ }
+
PushDefUseChildren(I, Worklist);
}
}
// constant or derived from a PHI node themselves.
PHINode *PHI = 0;
for (unsigned Op = 0, e = I->getNumOperands(); Op != e; ++Op)
- if (!(isa<Constant>(I->getOperand(Op)) ||
- isa<GlobalValue>(I->getOperand(Op)))) {
+ if (!isa<Constant>(I->getOperand(Op))) {
PHINode *P = getConstantEvolvingPHI(I->getOperand(Op), L);
if (P == 0) return 0; // Not evolving from PHI
if (PHI == 0)
const TargetData *TD) {
if (isa<PHINode>(V)) return PHIVal;
if (Constant *C = dyn_cast<Constant>(V)) return C;
- if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) return GV;
Instruction *I = cast<Instruction>(V);
- std::vector<Constant*> Operands;
- Operands.resize(I->getNumOperands());
+ std::vector<Constant*> Operands(I->getNumOperands());
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
Operands[i] = EvaluateExpression(I->getOperand(i), PHIVal, TD);
return RetVal = 0; // Must be a constant.
Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
- PHINode *PN2 = getConstantEvolvingPHI(BEValue, L);
- if (PN2 != PN)
+ if (getConstantEvolvingPHI(BEValue, L) != PN &&
+ !isa<Constant>(BEValue))
return RetVal = 0; // Not derived from same PHI.
// Execute the loop symbolically to determine the exit value.
PHINode *PN = getConstantEvolvingPHI(Cond, L);
if (PN == 0) return getCouldNotCompute();
- // Since the loop is canonicalized, the PHI node must have two entries. One
- // entry must be a constant (coming in from outside of the loop), and the
+ // If the loop is canonicalized, the PHI will have exactly two entries.
+ // That's the only form we support here.
+ if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
+
+ // One entry must be a constant (coming in from outside of the loop), and the
// second must be derived from the same PHI.
bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
Constant *StartCST =
if (StartCST == 0) return getCouldNotCompute(); // Must be a constant.
Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
- PHINode *PN2 = getConstantEvolvingPHI(BEValue, L);
- if (PN2 != PN) return getCouldNotCompute(); // Not derived from same PHI.
+ if (getConstantEvolvingPHI(BEValue, L) != PN &&
+ !isa<Constant>(BEValue))
+ return getCouldNotCompute(); // Not derived from same PHI.
// Okay, we find a PHI node that defines the trip count of this loop. Execute
// the loop symbolically to determine when the condition gets a value of
// the arguments into constants, and if so, try to constant propagate the
// result. This is particularly useful for computing loop exit values.
if (CanConstantFold(I)) {
- std::vector<Constant*> Operands;
- Operands.reserve(I->getNumOperands());
+ SmallVector<Constant *, 4> Operands;
+ bool MadeImprovement = false;
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
Value *Op = I->getOperand(i);
if (Constant *C = dyn_cast<Constant>(Op)) {
Operands.push_back(C);
- } else {
- // If any of the operands is non-constant and if they are
- // non-integer and non-pointer, don't even try to analyze them
- // with scev techniques.
- if (!isSCEVable(Op->getType()))
- return V;
-
- const SCEV *OpV = getSCEVAtScope(Op, L);
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV)) {
- Constant *C = SC->getValue();
- if (C->getType() != Op->getType())
- C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
- Op->getType(),
- false),
- C, Op->getType());
- Operands.push_back(C);
- } else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV)) {
- if (Constant *C = dyn_cast<Constant>(SU->getValue())) {
- if (C->getType() != Op->getType())
- C =
- ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
- Op->getType(),
- false),
- C, Op->getType());
- Operands.push_back(C);
- } else
- return V;
- } else {
- return V;
- }
+ continue;
}
+
+ // If any of the operands is non-constant and if they are
+ // non-integer and non-pointer, don't even try to analyze them
+ // with scev techniques.
+ if (!isSCEVable(Op->getType()))
+ return V;
+
+ const SCEV *OrigV = getSCEV(Op);
+ const SCEV *OpV = getSCEVAtScope(OrigV, L);
+ MadeImprovement |= OrigV != OpV;
+
+ Constant *C = 0;
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV))
+ C = SC->getValue();
+ if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV))
+ C = dyn_cast<Constant>(SU->getValue());
+ if (!C) return V;
+ if (C->getType() != Op->getType())
+ C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
+ Op->getType(),
+ false),
+ C, Op->getType());
+ Operands.push_back(C);
}
- Constant *C = 0;
- if (const CmpInst *CI = dyn_cast<CmpInst>(I))
- C = ConstantFoldCompareInstOperands(CI->getPredicate(),
- Operands[0], Operands[1], TD);
- else
- C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
- &Operands[0], Operands.size(), TD);
- if (C)
+ // Check to see if getSCEVAtScope actually made an improvement.
+ if (MadeImprovement) {
+ Constant *C = 0;
+ if (const CmpInst *CI = dyn_cast<CmpInst>(I))
+ C = ConstantFoldCompareInstOperands(CI->getPredicate(),
+ Operands[0], Operands[1], TD);
+ else
+ C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
+ &Operands[0], Operands.size(), TD);
+ if (!C) return V;
return getSCEV(C);
+ }
}
}
// If this is a loop recurrence for a loop that does not contain L, then we
// are dealing with the final value computed by the loop.
if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
- if (!L || !AddRec->getLoop()->contains(L)) {
+ // First, attempt to evaluate each operand.
+ // Avoid performing the look-up in the common case where the specified
+ // expression has no loop-variant portions.
+ for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
+ const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
+ if (OpAtScope == AddRec->getOperand(i))
+ continue;
+
+ // Okay, at least one of these operands is loop variant but might be
+ // foldable. Build a new instance of the folded commutative expression.
+ SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
+ AddRec->op_begin()+i);
+ NewOps.push_back(OpAtScope);
+ for (++i; i != e; ++i)
+ NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
+
+ AddRec = cast<SCEVAddRecExpr>(getAddRecExpr(NewOps, AddRec->getLoop()));
+ break;
+ }
+
+ // If the scope is outside the addrec's loop, evaluate it by using the
+ // loop exit value of the addrec.
+ if (!AddRec->getLoop()->contains(L)) {
// To evaluate this recurrence, we need to know how many times the AddRec
// loop iterates. Compute this now.
const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
// Then, evaluate the AddRec.
return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
}
+
return AddRec;
}
return getCouldNotCompute();
}
-/// getLoopPredecessor - If the given loop's header has exactly one unique
-/// predecessor outside the loop, return it. Otherwise return null.
-/// This is less strict that the loop "preheader" concept, which requires
-/// the predecessor to have only one single successor.
-///
-BasicBlock *ScalarEvolution::getLoopPredecessor(const Loop *L) {
- BasicBlock *Header = L->getHeader();
- BasicBlock *Pred = 0;
- for (pred_iterator PI = pred_begin(Header), E = pred_end(Header);
- PI != E; ++PI)
- if (!L->contains(*PI)) {
- if (Pred && Pred != *PI) return 0; // Multiple predecessors.
- Pred = *PI;
- }
- return Pred;
-}
-
/// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB
/// (which may not be an immediate predecessor) which has exactly one
/// successor from which BB is reachable, or null if no such block is
// If the header has a unique predecessor outside the loop, it must be
// a block that has exactly one successor that can reach the loop.
if (Loop *L = LI->getLoopFor(BB))
- return std::make_pair(getLoopPredecessor(L), L->getHeader());
+ return std::make_pair(L->getLoopPredecessor(), L->getHeader());
return std::pair<BasicBlock *, BasicBlock *>();
}
// as there are predecessors that can be found that have unique successors
// leading to the original header.
for (std::pair<BasicBlock *, BasicBlock *>
- Pair(getLoopPredecessor(L), L->getHeader());
+ Pair(L->getLoopPredecessor(), L->getHeader());
Pair.first;
Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
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