X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FScalarEvolution.cpp;h=d615c752b0444f4c91ec9284fe109ddab3736fad;hb=73b43b9b549a75fb0015c825df68abd95705a67c;hp=122dba3e6ac08b4b8bd0476a47e17069327d5e6c;hpb=a089b104218c46803a1af374f6c441df885e54c2;p=oota-llvm.git diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index 122dba3e6ac..d615c752b04 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -95,16 +95,14 @@ STATISTIC(NumTripCountsNotComputed, STATISTIC(NumBruteForceTripCountsComputed, "Number of loops with trip counts computed by force"); -cl::opt +static cl::opt MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden, cl::desc("Maximum number of iterations SCEV will " "symbolically execute a constant derived loop"), cl::init(100)); -namespace { - RegisterPass - R("scalar-evolution", "Scalar Evolution Analysis"); -} +static RegisterPass +R("scalar-evolution", "Scalar Evolution Analysis", false, true); char ScalarEvolution::ID = 0; //===----------------------------------------------------------------------===// @@ -134,6 +132,12 @@ uint32_t SCEV::getBitWidth() const { return 0; } +bool SCEV::isZero() const { + if (const SCEVConstant *SC = dyn_cast(this)) + return SC->getValue()->isZero(); + return false; +} + SCEVCouldNotCompute::SCEVCouldNotCompute() : SCEV(scCouldNotCompute) {} @@ -320,6 +324,8 @@ replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym, return SE.getMulExpr(NewOps); else if (isa(this)) return SE.getSMaxExpr(NewOps); + else if (isa(this)) + return SE.getUMaxExpr(NewOps); else assert(0 && "Unknown commutative expr!"); } @@ -429,7 +435,7 @@ namespace { /// than the complexity of the RHS. This comparator is used to canonicalize /// expressions. struct VISIBILITY_HIDDEN SCEVComplexityCompare { - bool operator()(SCEV *LHS, SCEV *RHS) { + bool operator()(const SCEV *LHS, const SCEV *RHS) const { return LHS->getSCEVType() < RHS->getSCEVType(); } }; @@ -450,7 +456,7 @@ static void GroupByComplexity(std::vector &Ops) { if (Ops.size() == 2) { // This is the common case, which also happens to be trivially simple. // Special case it. - if (Ops[0]->getSCEVType() > Ops[1]->getSCEVType()) + if (SCEVComplexityCompare()(Ops[1], Ops[0])) std::swap(Ops[0], Ops[1]); return; } @@ -492,35 +498,29 @@ SCEVHandle ScalarEvolution::getIntegerSCEV(int Val, const Type *Ty) { if (Val == 0) C = Constant::getNullValue(Ty); else if (Ty->isFloatingPoint()) - C = ConstantFP::get(Ty, APFloat(Ty==Type::FloatTy ? APFloat::IEEEsingle : - APFloat::IEEEdouble, Val)); + C = ConstantFP::get(APFloat(Ty==Type::FloatTy ? APFloat::IEEEsingle : + APFloat::IEEEdouble, Val)); else C = ConstantInt::get(Ty, Val); return getUnknown(C); } -/// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the -/// input value to the specified type. If the type must be extended, it is zero -/// extended. -static SCEVHandle getTruncateOrZeroExtend(const SCEVHandle &V, const Type *Ty, - ScalarEvolution &SE) { - const Type *SrcTy = V->getType(); - assert(SrcTy->isInteger() && Ty->isInteger() && - "Cannot truncate or zero extend with non-integer arguments!"); - if (SrcTy->getPrimitiveSizeInBits() == Ty->getPrimitiveSizeInBits()) - return V; // No conversion - if (SrcTy->getPrimitiveSizeInBits() > Ty->getPrimitiveSizeInBits()) - return SE.getTruncateExpr(V, Ty); - return SE.getZeroExtendExpr(V, Ty); -} - /// getNegativeSCEV - Return a SCEV corresponding to -V = -1*V /// SCEVHandle ScalarEvolution::getNegativeSCEV(const SCEVHandle &V) { if (SCEVConstant *VC = dyn_cast(V)) return getUnknown(ConstantExpr::getNeg(VC->getValue())); - return getMulExpr(V, getIntegerSCEV(-1, V->getType())); + return getMulExpr(V, getConstant(ConstantInt::getAllOnesValue(V->getType()))); +} + +/// getNotSCEV - Return a SCEV corresponding to ~V = -1-V +SCEVHandle ScalarEvolution::getNotSCEV(const SCEVHandle &V) { + if (SCEVConstant *VC = dyn_cast(V)) + return getUnknown(ConstantExpr::getNot(VC->getValue())); + + SCEVHandle AllOnes = getConstant(ConstantInt::getAllOnesValue(V->getType())); + return getMinusSCEV(AllOnes, V); } /// getMinusSCEV - Return a SCEV corresponding to LHS - RHS. @@ -576,7 +576,7 @@ static SCEVHandle BinomialCoefficient(SCEVHandle It, unsigned K, #endif const IntegerType *DividendTy = IntegerType::get(DividendBits); - const SCEVHandle ExIt = SE.getZeroExtendExpr(It, DividendTy); + const SCEVHandle ExIt = SE.getTruncateOrZeroExtend(It, DividendTy); // The final number of bits we need to perform the division is the maximum of // dividend and divisor bitwidths. @@ -598,7 +598,12 @@ static SCEVHandle BinomialCoefficient(SCEVHandle It, unsigned K, Dividend *= N-(K-1); if (DividendTy != DivisionTy) Dividend = Dividend.zext(DivisionTy->getBitWidth()); - return SE.getConstant(Dividend.udiv(Divisor).trunc(It->getBitWidth())); + + APInt Result = Dividend.udiv(Divisor); + if (Result.getBitWidth() != It->getBitWidth()) + Result = Result.trunc(It->getBitWidth()); + + return SE.getConstant(Result); } SCEVHandle Dividend = ExIt; @@ -606,11 +611,12 @@ static SCEVHandle BinomialCoefficient(SCEVHandle It, unsigned K, Dividend = SE.getMulExpr(Dividend, SE.getMinusSCEV(ExIt, SE.getIntegerSCEV(i, DividendTy))); - if (DividendTy != DivisionTy) - Dividend = SE.getZeroExtendExpr(Dividend, DivisionTy); - return - SE.getTruncateExpr(SE.getUDivExpr(Dividend, SE.getConstant(Divisor)), - It->getType()); + + return SE.getTruncateOrZeroExtend( + SE.getUDivExpr( + SE.getTruncateOrZeroExtend(Dividend, DivisionTy), + SE.getConstant(Divisor) + ), It->getType()); } /// evaluateAtIteration - Return the value of this chain of recurrences at @@ -694,6 +700,21 @@ SCEVHandle ScalarEvolution::getSignExtendExpr(const SCEVHandle &Op, const Type * return Result; } +/// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion +/// of the input value to the specified type. If the type must be +/// extended, it is zero extended. +SCEVHandle ScalarEvolution::getTruncateOrZeroExtend(const SCEVHandle &V, + const Type *Ty) { + const Type *SrcTy = V->getType(); + assert(SrcTy->isInteger() && Ty->isInteger() && + "Cannot truncate or zero extend with non-integer arguments!"); + if (SrcTy->getPrimitiveSizeInBits() == Ty->getPrimitiveSizeInBits()) + return V; // No conversion + if (SrcTy->getPrimitiveSizeInBits() > Ty->getPrimitiveSizeInBits()) + return getTruncateExpr(V, Ty); + return getZeroExtendExpr(V, Ty); +} + // get - Get a canonical add expression, or something simpler if possible. SCEVHandle ScalarEvolution::getAddExpr(std::vector &Ops) { assert(!Ops.empty() && "Cannot get empty add!"); @@ -709,19 +730,12 @@ SCEVHandle ScalarEvolution::getAddExpr(std::vector &Ops) { assert(Idx < Ops.size()); while (SCEVConstant *RHSC = dyn_cast(Ops[Idx])) { // We found two constants, fold them together! - Constant *Fold = ConstantInt::get(LHSC->getValue()->getValue() + - RHSC->getValue()->getValue()); - if (ConstantInt *CI = dyn_cast(Fold)) { - Ops[0] = getConstant(CI); - Ops.erase(Ops.begin()+1); // Erase the folded element - if (Ops.size() == 1) return Ops[0]; - LHSC = cast(Ops[0]); - } else { - // If we couldn't fold the expression, move to the next constant. Note - // that this is impossible to happen in practice because we always - // constant fold constant ints to constant ints. - ++Idx; - } + ConstantInt *Fold = ConstantInt::get(LHSC->getValue()->getValue() + + RHSC->getValue()->getValue()); + Ops[0] = getConstant(Fold); + Ops.erase(Ops.begin()+1); // Erase the folded element + if (Ops.size() == 1) return Ops[0]; + LHSC = cast(Ops[0]); } // If we are left with a constant zero being added, strip it off. @@ -950,19 +964,12 @@ SCEVHandle ScalarEvolution::getMulExpr(std::vector &Ops) { ++Idx; while (SCEVConstant *RHSC = dyn_cast(Ops[Idx])) { // We found two constants, fold them together! - Constant *Fold = ConstantInt::get(LHSC->getValue()->getValue() * - RHSC->getValue()->getValue()); - if (ConstantInt *CI = dyn_cast(Fold)) { - Ops[0] = getConstant(CI); - Ops.erase(Ops.begin()+1); // Erase the folded element - if (Ops.size() == 1) return Ops[0]; - LHSC = cast(Ops[0]); - } else { - // If we couldn't fold the expression, move to the next constant. Note - // that this is impossible to happen in practice because we always - // constant fold constant ints to constant ints. - ++Idx; - } + ConstantInt *Fold = ConstantInt::get(LHSC->getValue()->getValue() * + RHSC->getValue()->getValue()); + Ops[0] = getConstant(Fold); + Ops.erase(Ops.begin()+1); // Erase the folded element + if (Ops.size() == 1) return Ops[0]; + LHSC = cast(Ops[0]); } // If we are left with a constant one being multiplied, strip it off. @@ -1135,11 +1142,10 @@ SCEVHandle ScalarEvolution::getAddRecExpr(std::vector &Operands, const Loop *L) { if (Operands.size() == 1) return Operands[0]; - if (SCEVConstant *StepC = dyn_cast(Operands.back())) - if (StepC->getValue()->isZero()) { - Operands.pop_back(); - return getAddRecExpr(Operands, L); // { X,+,0 } --> X - } + if (Operands.back()->isZero()) { + Operands.pop_back(); + return getAddRecExpr(Operands, L); // { X,+,0 } --> X + } SCEVAddRecExpr *&Result = (*SCEVAddRecExprs)[std::make_pair(L, std::vector(Operands.begin(), @@ -1170,20 +1176,13 @@ SCEVHandle ScalarEvolution::getSMaxExpr(std::vector Ops) { assert(Idx < Ops.size()); while (SCEVConstant *RHSC = dyn_cast(Ops[Idx])) { // We found two constants, fold them together! - Constant *Fold = ConstantInt::get( + ConstantInt *Fold = ConstantInt::get( APIntOps::smax(LHSC->getValue()->getValue(), RHSC->getValue()->getValue())); - if (ConstantInt *CI = dyn_cast(Fold)) { - Ops[0] = getConstant(CI); - Ops.erase(Ops.begin()+1); // Erase the folded element - if (Ops.size() == 1) return Ops[0]; - LHSC = cast(Ops[0]); - } else { - // If we couldn't fold the expression, move to the next constant. Note - // that this is impossible to happen in practice because we always - // constant fold constant ints to constant ints. - ++Idx; - } + Ops[0] = getConstant(Fold); + Ops.erase(Ops.begin()+1); // Erase the folded element + if (Ops.size() == 1) return Ops[0]; + LHSC = cast(Ops[0]); } // If we are left with a constant -inf, strip it off. @@ -1226,7 +1225,7 @@ SCEVHandle ScalarEvolution::getSMaxExpr(std::vector Ops) { assert(!Ops.empty() && "Reduced smax down to nothing!"); - // Okay, it looks like we really DO need an add expr. Check to see if we + // Okay, it looks like we really DO need an smax expr. Check to see if we // already have one, otherwise create a new one. std::vector SCEVOps(Ops.begin(), Ops.end()); SCEVCommutativeExpr *&Result = (*SCEVCommExprs)[std::make_pair(scSMaxExpr, @@ -1235,6 +1234,86 @@ SCEVHandle ScalarEvolution::getSMaxExpr(std::vector Ops) { return Result; } +SCEVHandle ScalarEvolution::getUMaxExpr(const SCEVHandle &LHS, + const SCEVHandle &RHS) { + std::vector Ops; + Ops.push_back(LHS); + Ops.push_back(RHS); + return getUMaxExpr(Ops); +} + +SCEVHandle ScalarEvolution::getUMaxExpr(std::vector Ops) { + assert(!Ops.empty() && "Cannot get empty umax!"); + if (Ops.size() == 1) return Ops[0]; + + // Sort by complexity, this groups all similar expression types together. + GroupByComplexity(Ops); + + // If there are any constants, fold them together. + unsigned Idx = 0; + if (SCEVConstant *LHSC = dyn_cast(Ops[0])) { + ++Idx; + assert(Idx < Ops.size()); + while (SCEVConstant *RHSC = dyn_cast(Ops[Idx])) { + // We found two constants, fold them together! + ConstantInt *Fold = ConstantInt::get( + APIntOps::umax(LHSC->getValue()->getValue(), + RHSC->getValue()->getValue())); + Ops[0] = getConstant(Fold); + Ops.erase(Ops.begin()+1); // Erase the folded element + if (Ops.size() == 1) return Ops[0]; + LHSC = cast(Ops[0]); + } + + // If we are left with a constant zero, strip it off. + if (cast(Ops[0])->getValue()->isMinValue(false)) { + Ops.erase(Ops.begin()); + --Idx; + } + } + + if (Ops.size() == 1) return Ops[0]; + + // Find the first UMax + while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr) + ++Idx; + + // Check to see if one of the operands is a UMax. If so, expand its operands + // onto our operand list, and recurse to simplify. + if (Idx < Ops.size()) { + bool DeletedUMax = false; + while (SCEVUMaxExpr *UMax = dyn_cast(Ops[Idx])) { + Ops.insert(Ops.end(), UMax->op_begin(), UMax->op_end()); + Ops.erase(Ops.begin()+Idx); + DeletedUMax = true; + } + + if (DeletedUMax) + return getUMaxExpr(Ops); + } + + // Okay, check to see if the same value occurs in the operand list twice. If + // so, delete one. Since we sorted the list, these values are required to + // be adjacent. + for (unsigned i = 0, e = Ops.size()-1; i != e; ++i) + if (Ops[i] == Ops[i+1]) { // X umax Y umax Y --> X umax Y + Ops.erase(Ops.begin()+i, Ops.begin()+i+1); + --i; --e; + } + + if (Ops.size() == 1) return Ops[0]; + + assert(!Ops.empty() && "Reduced umax down to nothing!"); + + // Okay, it looks like we really DO need a umax expr. Check to see if we + // already have one, otherwise create a new one. + std::vector SCEVOps(Ops.begin(), Ops.end()); + SCEVCommutativeExpr *&Result = (*SCEVCommExprs)[std::make_pair(scUMaxExpr, + SCEVOps)]; + if (Result == 0) Result = new SCEVUMaxExpr(Ops); + return Result; +} + SCEVHandle ScalarEvolution::getUnknown(Value *V) { if (ConstantInt *CI = dyn_cast(V)) return getConstant(CI); @@ -1606,6 +1685,14 @@ static uint32_t GetMinTrailingZeros(SCEVHandle S) { return MinOpRes; } + if (SCEVUMaxExpr *M = dyn_cast(S)) { + // The result is the min of all operands results. + uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0)); + for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i) + MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i))); + return MinOpRes; + } + // SCEVUDivExpr, SCEVUnknown return 0; } @@ -1617,96 +1704,125 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) { if (!isa(V->getType())) return SE.getUnknown(V); - if (Instruction *I = dyn_cast(V)) { - switch (I->getOpcode()) { - case Instruction::Add: - return SE.getAddExpr(getSCEV(I->getOperand(0)), - getSCEV(I->getOperand(1))); - case Instruction::Mul: - return SE.getMulExpr(getSCEV(I->getOperand(0)), - getSCEV(I->getOperand(1))); - case Instruction::UDiv: - return SE.getUDivExpr(getSCEV(I->getOperand(0)), - getSCEV(I->getOperand(1))); - case Instruction::Sub: - return SE.getMinusSCEV(getSCEV(I->getOperand(0)), - getSCEV(I->getOperand(1))); - case Instruction::Or: - // If the RHS of the Or is a constant, we may have something like: - // X*4+1 which got turned into X*4|1. Handle this as an Add so loop - // optimizations will transparently handle this case. - // - // In order for this transformation to be safe, the LHS must be of the - // form X*(2^n) and the Or constant must be less than 2^n. - if (ConstantInt *CI = dyn_cast(I->getOperand(1))) { - SCEVHandle LHS = getSCEV(I->getOperand(0)); - const APInt &CIVal = CI->getValue(); - if (GetMinTrailingZeros(LHS) >= - (CIVal.getBitWidth() - CIVal.countLeadingZeros())) - return SE.getAddExpr(LHS, getSCEV(I->getOperand(1))); - } - break; - case Instruction::Xor: - // If the RHS of the xor is a signbit, then this is just an add. - // Instcombine turns add of signbit into xor as a strength reduction step. - if (ConstantInt *CI = dyn_cast(I->getOperand(1))) { - if (CI->getValue().isSignBit()) - return SE.getAddExpr(getSCEV(I->getOperand(0)), - getSCEV(I->getOperand(1))); - } - break; - - case Instruction::Shl: - // Turn shift left of a constant amount into a multiply. - if (ConstantInt *SA = dyn_cast(I->getOperand(1))) { - uint32_t BitWidth = cast(V->getType())->getBitWidth(); - Constant *X = ConstantInt::get( - APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth))); - return SE.getMulExpr(getSCEV(I->getOperand(0)), getSCEV(X)); - } - break; - - case Instruction::Trunc: - return SE.getTruncateExpr(getSCEV(I->getOperand(0)), I->getType()); - - case Instruction::ZExt: - return SE.getZeroExtendExpr(getSCEV(I->getOperand(0)), I->getType()); - - case Instruction::SExt: - return SE.getSignExtendExpr(getSCEV(I->getOperand(0)), I->getType()); - - case Instruction::BitCast: - // BitCasts are no-op casts so we just eliminate the cast. - if (I->getType()->isInteger() && - I->getOperand(0)->getType()->isInteger()) - return getSCEV(I->getOperand(0)); - break; - - case Instruction::PHI: - return createNodeForPHI(cast(I)); - - case Instruction::Select: - // This could be an SCEVSMax that was lowered earlier. Try to recover it. - if (ICmpInst *ICI = dyn_cast(I->getOperand(0))) { - Value *LHS = ICI->getOperand(0); - Value *RHS = ICI->getOperand(1); - switch (ICI->getPredicate()) { - case ICmpInst::ICMP_SLT: - case ICmpInst::ICMP_SLE: - std::swap(LHS, RHS); - // fall through - case ICmpInst::ICMP_SGT: - case ICmpInst::ICMP_SGE: - if (LHS == I->getOperand(1) && RHS == I->getOperand(2)) - return SE.getSMaxExpr(getSCEV(LHS), getSCEV(RHS)); - default: - break; - } - } + unsigned Opcode = Instruction::UserOp1; + if (Instruction *I = dyn_cast(V)) + Opcode = I->getOpcode(); + else if (ConstantExpr *CE = dyn_cast(V)) + Opcode = CE->getOpcode(); + else + return SE.getUnknown(V); - default: // We cannot analyze this expression. - break; + User *U = cast(V); + switch (Opcode) { + case Instruction::Add: + return SE.getAddExpr(getSCEV(U->getOperand(0)), + getSCEV(U->getOperand(1))); + case Instruction::Mul: + return SE.getMulExpr(getSCEV(U->getOperand(0)), + getSCEV(U->getOperand(1))); + case Instruction::UDiv: + return SE.getUDivExpr(getSCEV(U->getOperand(0)), + getSCEV(U->getOperand(1))); + case Instruction::Sub: + return SE.getMinusSCEV(getSCEV(U->getOperand(0)), + getSCEV(U->getOperand(1))); + case Instruction::Or: + // If the RHS of the Or is a constant, we may have something like: + // X*4+1 which got turned into X*4|1. Handle this as an Add so loop + // optimizations will transparently handle this case. + // + // In order for this transformation to be safe, the LHS must be of the + // form X*(2^n) and the Or constant must be less than 2^n. + if (ConstantInt *CI = dyn_cast(U->getOperand(1))) { + SCEVHandle LHS = getSCEV(U->getOperand(0)); + const APInt &CIVal = CI->getValue(); + if (GetMinTrailingZeros(LHS) >= + (CIVal.getBitWidth() - CIVal.countLeadingZeros())) + return SE.getAddExpr(LHS, getSCEV(U->getOperand(1))); } + break; + case Instruction::Xor: + // If the RHS of the xor is a signbit, then this is just an add. + // Instcombine turns add of signbit into xor as a strength reduction step. + if (ConstantInt *CI = dyn_cast(U->getOperand(1))) { + if (CI->getValue().isSignBit()) + return SE.getAddExpr(getSCEV(U->getOperand(0)), + getSCEV(U->getOperand(1))); + else if (CI->isAllOnesValue()) + return SE.getNotSCEV(getSCEV(U->getOperand(0))); + } + break; + + case Instruction::Shl: + // Turn shift left of a constant amount into a multiply. + if (ConstantInt *SA = dyn_cast(U->getOperand(1))) { + uint32_t BitWidth = cast(V->getType())->getBitWidth(); + Constant *X = ConstantInt::get( + APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth))); + return SE.getMulExpr(getSCEV(U->getOperand(0)), getSCEV(X)); + } + break; + + case Instruction::Trunc: + return SE.getTruncateExpr(getSCEV(U->getOperand(0)), U->getType()); + + case Instruction::ZExt: + return SE.getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType()); + + case Instruction::SExt: + return SE.getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType()); + + case Instruction::BitCast: + // BitCasts are no-op casts so we just eliminate the cast. + if (U->getType()->isInteger() && + U->getOperand(0)->getType()->isInteger()) + return getSCEV(U->getOperand(0)); + break; + + case Instruction::PHI: + return createNodeForPHI(cast(U)); + + case Instruction::Select: + // This could be a smax or umax that was lowered earlier. + // Try to recover it. + if (ICmpInst *ICI = dyn_cast(U->getOperand(0))) { + Value *LHS = ICI->getOperand(0); + Value *RHS = ICI->getOperand(1); + switch (ICI->getPredicate()) { + case ICmpInst::ICMP_SLT: + case ICmpInst::ICMP_SLE: + std::swap(LHS, RHS); + // fall through + case ICmpInst::ICMP_SGT: + case ICmpInst::ICMP_SGE: + if (LHS == U->getOperand(1) && RHS == U->getOperand(2)) + return SE.getSMaxExpr(getSCEV(LHS), getSCEV(RHS)); + else if (LHS == U->getOperand(2) && RHS == U->getOperand(1)) + // -smax(-x, -y) == smin(x, y). + return SE.getNegativeSCEV(SE.getSMaxExpr( + SE.getNegativeSCEV(getSCEV(LHS)), + SE.getNegativeSCEV(getSCEV(RHS)))); + break; + case ICmpInst::ICMP_ULT: + case ICmpInst::ICMP_ULE: + std::swap(LHS, RHS); + // fall through + case ICmpInst::ICMP_UGT: + case ICmpInst::ICMP_UGE: + if (LHS == U->getOperand(1) && RHS == U->getOperand(2)) + return SE.getUMaxExpr(getSCEV(LHS), getSCEV(RHS)); + else if (LHS == U->getOperand(2) && RHS == U->getOperand(1)) + // ~umax(~x, ~y) == umin(x, y) + return SE.getNotSCEV(SE.getUMaxExpr(SE.getNotSCEV(getSCEV(LHS)), + SE.getNotSCEV(getSCEV(RHS)))); + break; + default: + break; + } + } + + default: // We cannot analyze this expression. + break; } return SE.getUnknown(V); @@ -1786,7 +1902,7 @@ SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) { ICmpInst *ExitCond = dyn_cast(ExitBr->getCondition()); - // If its not an integer comparison then compute it the hard way. + // If it's not an integer comparison then compute it the hard way. // Note that ICmpInst deals with pointer comparisons too so we must check // the type of the operand. if (ExitCond == 0 || isa(ExitCond->getOperand(0)->getType())) @@ -1819,8 +1935,8 @@ SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) { // At this point, we would like to compute how many iterations of the // loop the predicate will return true for these inputs. - if (LHS->isLoopInvariant(L) && !RHS->isLoopInvariant(L)) { - // If there is a loop-invariant, force it into the RHS. + if (isa(LHS) && !isa(RHS)) { + // If there is a constant, force it into the RHS. std::swap(LHS, RHS); Cond = ICmpInst::getSwappedPredicate(Cond); } @@ -1880,8 +1996,8 @@ SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) { break; } case ICmpInst::ICMP_UGT: { - SCEVHandle TC = HowManyLessThans(SE.getNegativeSCEV(LHS), - SE.getNegativeSCEV(RHS), L, false); + SCEVHandle TC = HowManyLessThans(SE.getNotSCEV(LHS), + SE.getNotSCEV(RHS), L, false); if (!isa(TC)) return TC; break; } @@ -1945,7 +2061,7 @@ GetAddressedElementFromGlobal(GlobalVariable *GV, } /// ComputeLoadConstantCompareIterationCount - Given an exit condition of -/// 'icmp op load X, cst', try to se if we can compute the trip count. +/// 'icmp op load X, cst', try to see if we can compute the trip count. SCEVHandle ScalarEvolutionsImpl:: ComputeLoadConstantCompareIterationCount(LoadInst *LI, Constant *RHS, const Loop *L, @@ -2045,13 +2161,14 @@ static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) { Instruction *I = dyn_cast(V); if (I == 0 || !L->contains(I->getParent())) return 0; - if (PHINode *PN = dyn_cast(I)) + if (PHINode *PN = dyn_cast(I)) { if (L->getHeader() == I->getParent()) return PN; else // We don't currently keep track of the control flow needed to evaluate // PHIs, so we cannot handle PHIs inside of loops. return 0; + } // If we won't be able to constant fold this expression even if the operands // are constants, return early. @@ -2081,8 +2198,6 @@ static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) { /// reason, return null. static Constant *EvaluateExpression(Value *V, Constant *PHIVal) { if (isa(V)) return PHIVal; - if (GlobalValue *GV = dyn_cast(V)) - return GV; if (Constant *C = dyn_cast(V)) return C; Instruction *I = cast(V); @@ -2212,7 +2327,7 @@ SCEVHandle ScalarEvolutionsImpl::getSCEVAtScope(SCEV *V, const Loop *L) { if (isa(V)) return V; - // If this instruction is evolves from a constant-evolving PHI, compute the + // If this instruction is evolved from a constant-evolving PHI, compute the // exit value from the loop without using SCEVs. if (SCEVUnknown *SU = dyn_cast(V)) { if (Instruction *I = dyn_cast(SU->getValue())) { @@ -2308,6 +2423,8 @@ SCEVHandle ScalarEvolutionsImpl::getSCEVAtScope(SCEV *V, const Loop *L) { return SE.getMulExpr(NewOps); if (isa(Comm)) return SE.getSMaxExpr(NewOps); + if (isa(Comm)) + return SE.getUMaxExpr(NewOps); assert(0 && "Unknown commutative SCEV type!"); } } @@ -2333,8 +2450,8 @@ SCEVHandle ScalarEvolutionsImpl::getSCEVAtScope(SCEV *V, const Loop *L) { // loop iterates. Compute this now. SCEVHandle IterationCount = getIterationCount(AddRec->getLoop()); if (IterationCount == UnknownValue) return UnknownValue; - IterationCount = getTruncateOrZeroExtend(IterationCount, - AddRec->getType(), SE); + IterationCount = SE.getTruncateOrZeroExtend(IterationCount, + AddRec->getType()); // If the value is affine, simplify the expression evaluation to just // Start + Step*IterationCount. @@ -2449,9 +2566,9 @@ SCEVHandle ScalarEvolutionsImpl::HowFarToZero(SCEV *V, const Loop *L) { if (SCEVConstant *StartC = dyn_cast(Start)) { ConstantInt *StartCC = StartC->getValue(); Constant *StartNegC = ConstantExpr::getNeg(StartCC); - Constant *Rem = ConstantExpr::getSRem(StartNegC, StepC->getValue()); + Constant *Rem = ConstantExpr::getURem(StartNegC, StepC->getValue()); if (Rem->isNullValue()) { - Constant *Result =ConstantExpr::getSDiv(StartNegC,StepC->getValue()); + Constant *Result = ConstantExpr::getUDiv(StartNegC,StepC->getValue()); return SE.getUnknown(Result); } } @@ -2478,9 +2595,8 @@ SCEVHandle ScalarEvolutionsImpl::HowFarToZero(SCEV *V, const Loop *L) { // value at this index. When solving for "X*X != 5", for example, we // should not accept a root of 2. SCEVHandle Val = AddRec->evaluateAtIteration(R1, SE); - if (SCEVConstant *EvalVal = dyn_cast(Val)) - if (EvalVal->getValue()->isZero()) - return R1; // We found a quadratic root! + if (Val->isZero()) + return R1; // We found a quadratic root! } } } @@ -2499,11 +2615,8 @@ SCEVHandle ScalarEvolutionsImpl::HowFarToNonZero(SCEV *V, const Loop *L) { // If the value is a constant, check to see if it is known to be non-zero // already. If so, the backedge will execute zero times. if (SCEVConstant *C = dyn_cast(V)) { - Constant *Zero = Constant::getNullValue(C->getValue()->getType()); - Constant *NonZero = - ConstantExpr::getICmp(ICmpInst::ICMP_NE, C->getValue(), Zero); - if (NonZero == ConstantInt::getTrue()) - return getSCEV(Zero); + if (!C->getValue()->isNullValue()) + return SE.getIntegerSCEV(0, C->getType()); return UnknownValue; // Otherwise it will loop infinitely. } @@ -2525,21 +2638,27 @@ HowManyLessThans(SCEV *LHS, SCEV *RHS, const Loop *L, bool isSigned) { return UnknownValue; if (AddRec->isAffine()) { - // The number of iterations for "{n,+,1} < m", is m-n. However, we don't - // know that m is >= n on input to the loop. If it is, the condition - // returns true zero times. To handle both cases, we return SMAX(0, m-n). - // FORNOW: We only support unit strides. SCEVHandle One = SE.getIntegerSCEV(1, RHS->getType()); if (AddRec->getOperand(1) != One) return UnknownValue; - SCEVHandle Iters = SE.getMinusSCEV(RHS, AddRec->getOperand(0)); + // We know the LHS is of the form {n,+,1} and the RHS is some loop-invariant + // m. So, we count the number of iterations in which {n,+,1} < m is true. + // Note that we cannot simply return max(m-n,0) because it's not safe to + // treat m-n as signed nor unsigned due to overflow possibility. - if (isSigned) - return SE.getSMaxExpr(SE.getIntegerSCEV(0, RHS->getType()), Iters); - else - return Iters; + // First, we get the value of the LHS in the first iteration: n + SCEVHandle Start = AddRec->getOperand(0); + + // Then, we get the value of the LHS in the first iteration in which the + // above condition doesn't hold. This equals to max(m,n). + SCEVHandle End = isSigned ? SE.getSMaxExpr(RHS, Start) + : SE.getUMaxExpr(RHS, Start); + + // Finally, we subtract these two values to get the number of times the + // backedge is executed: max(m,n)-n. + return SE.getMinusSCEV(End, Start); } return UnknownValue;