X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FScalar%2FReassociate.cpp;h=71d787a839a73b380d514f7e33bc8de145839494;hb=ed5cb593efa6faaa8ed6dca36d5d200fb832496c;hp=d00423edf5affd14d22c3af61780be5c14699cf5;hpb=0975ed5f4ef7264b45995241717055f8a116bb27;p=oota-llvm.git diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp index d00423edf5a..71d787a839a 100644 --- a/lib/Transforms/Scalar/Reassociate.cpp +++ b/lib/Transforms/Scalar/Reassociate.cpp @@ -2,13 +2,13 @@ // // The LLVM Compiler Infrastructure // -// This file was developed by the LLVM research group and is distributed under -// the University of Illinois Open Source License. See LICENSE.TXT for details. +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This pass reassociates commutative expressions in an order that is designed -// to promote better constant propagation, GCSE, LICM, PRE... +// to promote better constant propagation, GCSE, LICM, PRE, etc. // // For example: 4 + (x + 5) -> x + (4 + 5) // @@ -23,25 +23,62 @@ #define DEBUG_TYPE "reassociate" #include "llvm/Transforms/Scalar.h" #include "llvm/Constants.h" +#include "llvm/DerivedTypes.h" #include "llvm/Function.h" #include "llvm/Instructions.h" +#include "llvm/IntrinsicInst.h" #include "llvm/Pass.h" -#include "llvm/Type.h" +#include "llvm/Assembly/Writer.h" #include "llvm/Support/CFG.h" #include "llvm/Support/Debug.h" +#include "llvm/Support/ValueHandle.h" +#include "llvm/Support/raw_ostream.h" #include "llvm/ADT/PostOrderIterator.h" #include "llvm/ADT/Statistic.h" +#include "llvm/ADT/DenseMap.h" +#include using namespace llvm; +STATISTIC(NumLinear , "Number of insts linearized"); +STATISTIC(NumChanged, "Number of insts reassociated"); +STATISTIC(NumAnnihil, "Number of expr tree annihilated"); +STATISTIC(NumFactor , "Number of multiplies factored"); + namespace { - Statistic<> NumLinear ("reassociate","Number of insts linearized"); - Statistic<> NumChanged("reassociate","Number of insts reassociated"); - Statistic<> NumSwapped("reassociate","Number of insts with operands swapped"); + struct ValueEntry { + unsigned Rank; + Value *Op; + ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {} + }; + inline bool operator<(const ValueEntry &LHS, const ValueEntry &RHS) { + return LHS.Rank > RHS.Rank; // Sort so that highest rank goes to start. + } +} +#ifndef NDEBUG +/// PrintOps - Print out the expression identified in the Ops list. +/// +static void PrintOps(Instruction *I, const SmallVectorImpl &Ops) { + Module *M = I->getParent()->getParent()->getParent(); + errs() << Instruction::getOpcodeName(I->getOpcode()) << " " + << *Ops[0].Op->getType() << '\t'; + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + errs() << "[ "; + WriteAsOperand(errs(), Ops[i].Op, false, M); + errs() << ", #" << Ops[i].Rank << "] "; + } +} +#endif + +namespace { class Reassociate : public FunctionPass { - std::map RankMap; - std::map ValueRankMap; + DenseMap RankMap; + DenseMap, unsigned> ValueRankMap; + bool MadeChange; public: + static char ID; // Pass identification, replacement for typeid + Reassociate() : FunctionPass(&ID) {} + bool runOnFunction(Function &F); virtual void getAnalysisUsage(AnalysisUsage &AU) const { @@ -50,128 +87,298 @@ namespace { private: void BuildRankMap(Function &F); unsigned getRank(Value *V); - bool ReassociateExpr(BinaryOperator *I); - bool ReassociateBB(BasicBlock *BB); + Value *ReassociateExpression(BinaryOperator *I); + void RewriteExprTree(BinaryOperator *I, SmallVectorImpl &Ops, + unsigned Idx = 0); + Value *OptimizeExpression(BinaryOperator *I, + SmallVectorImpl &Ops); + Value *OptimizeAdd(Instruction *I, SmallVectorImpl &Ops); + void LinearizeExprTree(BinaryOperator *I, SmallVectorImpl &Ops); + void LinearizeExpr(BinaryOperator *I); + Value *RemoveFactorFromExpression(Value *V, Value *Factor); + void ReassociateBB(BasicBlock *BB); + + void RemoveDeadBinaryOp(Value *V); }; - - RegisterOpt X("reassociate", "Reassociate expressions"); } +char Reassociate::ID = 0; +static RegisterPass X("reassociate", "Reassociate expressions"); + // Public interface to the Reassociate pass FunctionPass *llvm::createReassociatePass() { return new Reassociate(); } +void Reassociate::RemoveDeadBinaryOp(Value *V) { + Instruction *Op = dyn_cast(V); + if (!Op || !isa(Op) || !Op->use_empty()) + return; + + Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1); + + ValueRankMap.erase(Op); + Op->eraseFromParent(); + RemoveDeadBinaryOp(LHS); + RemoveDeadBinaryOp(RHS); +} + + +static bool isUnmovableInstruction(Instruction *I) { + if (I->getOpcode() == Instruction::PHI || + I->getOpcode() == Instruction::Alloca || + I->getOpcode() == Instruction::Load || + I->getOpcode() == Instruction::Invoke || + (I->getOpcode() == Instruction::Call && + !isa(I)) || + I->getOpcode() == Instruction::UDiv || + I->getOpcode() == Instruction::SDiv || + I->getOpcode() == Instruction::FDiv || + I->getOpcode() == Instruction::URem || + I->getOpcode() == Instruction::SRem || + I->getOpcode() == Instruction::FRem) + return true; + return false; +} + void Reassociate::BuildRankMap(Function &F) { unsigned i = 2; // Assign distinct ranks to function arguments for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I) - ValueRankMap[I] = ++i; + ValueRankMap[&*I] = ++i; ReversePostOrderTraversal RPOT(&F); for (ReversePostOrderTraversal::rpo_iterator I = RPOT.begin(), - E = RPOT.end(); I != E; ++I) - RankMap[*I] = ++i << 16; + E = RPOT.end(); I != E; ++I) { + BasicBlock *BB = *I; + unsigned BBRank = RankMap[BB] = ++i << 16; + + // Walk the basic block, adding precomputed ranks for any instructions that + // we cannot move. This ensures that the ranks for these instructions are + // all different in the block. + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) + if (isUnmovableInstruction(I)) + ValueRankMap[&*I] = ++BBRank; + } } unsigned Reassociate::getRank(Value *V) { - if (isa(V)) return ValueRankMap[V]; // Function argument... - Instruction *I = dyn_cast(V); - if (I == 0) return 0; // Otherwise it's a global or constant, rank 0. + if (I == 0) { + if (isa(V)) return ValueRankMap[V]; // Function argument. + return 0; // Otherwise it's a global or constant, rank 0. + } + + if (unsigned Rank = ValueRankMap[I]) + return Rank; // Rank already known? - unsigned &CachedRank = ValueRankMap[I]; - if (CachedRank) return CachedRank; // Rank already known? - // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that // we can reassociate expressions for code motion! Since we do not recurse // for PHI nodes, we cannot have infinite recursion here, because there // cannot be loops in the value graph that do not go through PHI nodes. - // - if (I->getOpcode() == Instruction::PHI || - I->getOpcode() == Instruction::Alloca || - I->getOpcode() == Instruction::Malloc || isa(I) || - I->mayWriteToMemory()) // Cannot move inst if it writes to memory! - return RankMap[I->getParent()]; - - // If not, compute it! unsigned Rank = 0, MaxRank = RankMap[I->getParent()]; for (unsigned i = 0, e = I->getNumOperands(); i != e && Rank != MaxRank; ++i) Rank = std::max(Rank, getRank(I->getOperand(i))); - - DEBUG(std::cerr << "Calculated Rank[" << V->getName() << "] = " - << Rank+1 << "\n"); - - return CachedRank = Rank+1; + + // If this is a not or neg instruction, do not count it for rank. This + // assures us that X and ~X will have the same rank. + if (!I->getType()->isInteger() || + (!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I))) + ++Rank; + + //DEBUG(errs() << "Calculated Rank[" << V->getName() << "] = " + // << Rank << "\n"); + + return ValueRankMap[I] = Rank; } +/// isReassociableOp - Return true if V is an instruction of the specified +/// opcode and if it only has one use. +static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) { + if ((V->hasOneUse() || V->use_empty()) && isa(V) && + cast(V)->getOpcode() == Opcode) + return cast(V); + return 0; +} -bool Reassociate::ReassociateExpr(BinaryOperator *I) { - Value *LHS = I->getOperand(0); - Value *RHS = I->getOperand(1); - unsigned LHSRank = getRank(LHS); - unsigned RHSRank = getRank(RHS); +/// LowerNegateToMultiply - Replace 0-X with X*-1. +/// +static Instruction *LowerNegateToMultiply(Instruction *Neg, + DenseMap, unsigned> &ValueRankMap) { + Constant *Cst = Constant::getAllOnesValue(Neg->getType()); - bool Changed = false; + Instruction *Res = BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg); + ValueRankMap.erase(Neg); + Res->takeName(Neg); + Neg->replaceAllUsesWith(Res); + Neg->eraseFromParent(); + return Res; +} - // Make sure the LHS of the operand always has the greater rank... - if (LHSRank < RHSRank) { - bool Success = !I->swapOperands(); - assert(Success && "swapOperands failed"); +// Given an expression of the form '(A+B)+(D+C)', turn it into '(((A+B)+C)+D)'. +// Note that if D is also part of the expression tree that we recurse to +// linearize it as well. Besides that case, this does not recurse into A,B, or +// C. +void Reassociate::LinearizeExpr(BinaryOperator *I) { + BinaryOperator *LHS = cast(I->getOperand(0)); + BinaryOperator *RHS = cast(I->getOperand(1)); + assert(isReassociableOp(LHS, I->getOpcode()) && + isReassociableOp(RHS, I->getOpcode()) && + "Not an expression that needs linearization?"); + + DEBUG(errs() << "Linear" << *LHS << '\n' << *RHS << '\n' << *I << '\n'); + + // Move the RHS instruction to live immediately before I, avoiding breaking + // dominator properties. + RHS->moveBefore(I); + + // Move operands around to do the linearization. + I->setOperand(1, RHS->getOperand(0)); + RHS->setOperand(0, LHS); + I->setOperand(0, RHS); + ++NumLinear; + MadeChange = true; + DEBUG(errs() << "Linearized: " << *I << '\n'); + + // If D is part of this expression tree, tail recurse. + if (isReassociableOp(I->getOperand(1), I->getOpcode())) + LinearizeExpr(I); +} + + +/// LinearizeExprTree - Given an associative binary expression tree, traverse +/// all of the uses putting it into canonical form. This forces a left-linear +/// form of the the expression (((a+b)+c)+d), and collects information about the +/// rank of the non-tree operands. +/// +/// NOTE: These intentionally destroys the expression tree operands (turning +/// them into undef values) to reduce #uses of the values. This means that the +/// caller MUST use something like RewriteExprTree to put the values back in. +/// +void Reassociate::LinearizeExprTree(BinaryOperator *I, + SmallVectorImpl &Ops) { + Value *LHS = I->getOperand(0), *RHS = I->getOperand(1); + unsigned Opcode = I->getOpcode(); + + // First step, linearize the expression if it is in ((A+B)+(C+D)) form. + BinaryOperator *LHSBO = isReassociableOp(LHS, Opcode); + BinaryOperator *RHSBO = isReassociableOp(RHS, Opcode); + + // If this is a multiply expression tree and it contains internal negations, + // transform them into multiplies by -1 so they can be reassociated. + if (I->getOpcode() == Instruction::Mul) { + if (!LHSBO && LHS->hasOneUse() && BinaryOperator::isNeg(LHS)) { + LHS = LowerNegateToMultiply(cast(LHS), ValueRankMap); + LHSBO = isReassociableOp(LHS, Opcode); + } + if (!RHSBO && RHS->hasOneUse() && BinaryOperator::isNeg(RHS)) { + RHS = LowerNegateToMultiply(cast(RHS), ValueRankMap); + RHSBO = isReassociableOp(RHS, Opcode); + } + } + + if (!LHSBO) { + if (!RHSBO) { + // Neither the LHS or RHS as part of the tree, thus this is a leaf. As + // such, just remember these operands and their rank. + Ops.push_back(ValueEntry(getRank(LHS), LHS)); + Ops.push_back(ValueEntry(getRank(RHS), RHS)); + + // Clear the leaves out. + I->setOperand(0, UndefValue::get(I->getType())); + I->setOperand(1, UndefValue::get(I->getType())); + return; + } + + // Turn X+(Y+Z) -> (Y+Z)+X + std::swap(LHSBO, RHSBO); std::swap(LHS, RHS); - std::swap(LHSRank, RHSRank); - Changed = true; - ++NumSwapped; - DEBUG(std::cerr << "Transposed: " << *I - /* << " Result BB: " << I->getParent()*/); + bool Success = !I->swapOperands(); + assert(Success && "swapOperands failed"); + Success = false; + MadeChange = true; + } else if (RHSBO) { + // Turn (A+B)+(C+D) -> (((A+B)+C)+D). This guarantees the the RHS is not + // part of the expression tree. + LinearizeExpr(I); + LHS = LHSBO = cast(I->getOperand(0)); + RHS = I->getOperand(1); + RHSBO = 0; } - // If the LHS is the same operator as the current one is, and if we are the - // only expression using it... - // - if (BinaryOperator *LHSI = dyn_cast(LHS)) - if (LHSI->getOpcode() == I->getOpcode() && LHSI->hasOneUse()) { - // If the rank of our current RHS is less than the rank of the LHS's LHS, - // then we reassociate the two instructions... - - unsigned TakeOp = 0; - if (BinaryOperator *IOp = dyn_cast(LHSI->getOperand(0))) - if (IOp->getOpcode() == LHSI->getOpcode()) - TakeOp = 1; // Hoist out non-tree portion - - if (RHSRank < getRank(LHSI->getOperand(TakeOp))) { - // Convert ((a + 12) + 10) into (a + (12 + 10)) - I->setOperand(0, LHSI->getOperand(TakeOp)); - LHSI->setOperand(TakeOp, RHS); - I->setOperand(1, LHSI); - - // Move the LHS expression forward, to ensure that it is dominated by - // its operands. - LHSI->getParent()->getInstList().remove(LHSI); - I->getParent()->getInstList().insert(I, LHSI); - - ++NumChanged; - DEBUG(std::cerr << "Reassociated: " << *I/* << " Result BB: " - << I->getParent()*/); - - // Since we modified the RHS instruction, make sure that we recheck it. - ReassociateExpr(LHSI); - ReassociateExpr(I); - return true; - } + // Okay, now we know that the LHS is a nested expression and that the RHS is + // not. Perform reassociation. + assert(!isReassociableOp(RHS, Opcode) && "LinearizeExpr failed!"); + + // Move LHS right before I to make sure that the tree expression dominates all + // values. + LHSBO->moveBefore(I); + + // Linearize the expression tree on the LHS. + LinearizeExprTree(LHSBO, Ops); + + // Remember the RHS operand and its rank. + Ops.push_back(ValueEntry(getRank(RHS), RHS)); + + // Clear the RHS leaf out. + I->setOperand(1, UndefValue::get(I->getType())); +} + +// RewriteExprTree - Now that the operands for this expression tree are +// linearized and optimized, emit them in-order. This function is written to be +// tail recursive. +void Reassociate::RewriteExprTree(BinaryOperator *I, + SmallVectorImpl &Ops, + unsigned i) { + if (i+2 == Ops.size()) { + if (I->getOperand(0) != Ops[i].Op || + I->getOperand(1) != Ops[i+1].Op) { + Value *OldLHS = I->getOperand(0); + DEBUG(errs() << "RA: " << *I << '\n'); + I->setOperand(0, Ops[i].Op); + I->setOperand(1, Ops[i+1].Op); + DEBUG(errs() << "TO: " << *I << '\n'); + MadeChange = true; + ++NumChanged; + + // If we reassociated a tree to fewer operands (e.g. (1+a+2) -> (a+3) + // delete the extra, now dead, nodes. + RemoveDeadBinaryOp(OldLHS); } + return; + } + assert(i+2 < Ops.size() && "Ops index out of range!"); - return Changed; + if (I->getOperand(1) != Ops[i].Op) { + DEBUG(errs() << "RA: " << *I << '\n'); + I->setOperand(1, Ops[i].Op); + DEBUG(errs() << "TO: " << *I << '\n'); + MadeChange = true; + ++NumChanged; + } + + BinaryOperator *LHS = cast(I->getOperand(0)); + assert(LHS->getOpcode() == I->getOpcode() && + "Improper expression tree!"); + + // Compactify the tree instructions together with each other to guarantee + // that the expression tree is dominated by all of Ops. + LHS->moveBefore(I); + RewriteExprTree(LHS, Ops, i+1); } + // NegateValue - Insert instructions before the instruction pointed to by BI, // that computes the negative version of the value specified. The negative // version of the value is returned, and BI is left pointing at the instruction // that should be processed next by the reassociation pass. // static Value *NegateValue(Value *V, Instruction *BI) { + if (Constant *C = dyn_cast(V)) + return ConstantExpr::getNeg(C); + // We are trying to expose opportunity for reassociation. One of the things // that we want to do to achieve this is to push a negation as deep into an // expression chain as possible, to expose the add instructions. In practice, @@ -179,149 +386,639 @@ static Value *NegateValue(Value *V, Instruction *BI) { // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate // the constants. We assume that instcombine will clean up the mess later if - // we introduce tons of unnecessary negation instructions... + // we introduce tons of unnecessary negation instructions. // if (Instruction *I = dyn_cast(V)) if (I->getOpcode() == Instruction::Add && I->hasOneUse()) { - Value *RHS = NegateValue(I->getOperand(1), BI); - Value *LHS = NegateValue(I->getOperand(0), BI); + // Push the negates through the add. + I->setOperand(0, NegateValue(I->getOperand(0), BI)); + I->setOperand(1, NegateValue(I->getOperand(1), BI)); - // We must actually insert a new add instruction here, because the neg - // instructions do not dominate the old add instruction in general. By - // adding it now, we are assured that the neg instructions we just - // inserted dominate the instruction we are about to insert after them. + // We must move the add instruction here, because the neg instructions do + // not dominate the old add instruction in general. By moving it, we are + // assured that the neg instructions we just inserted dominate the + // instruction we are about to insert after them. // - return BinaryOperator::create(Instruction::Add, LHS, RHS, - I->getName()+".neg", BI); + I->moveBefore(BI); + I->setName(I->getName()+".neg"); + return I; } + + // Okay, we need to materialize a negated version of V with an instruction. + // Scan the use lists of V to see if we have one already. + for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){ + if (!BinaryOperator::isNeg(*UI)) continue; + + // We found one! Now we have to make sure that the definition dominates + // this use. We do this by moving it to the entry block (if it is a + // non-instruction value) or right after the definition. These negates will + // be zapped by reassociate later, so we don't need much finesse here. + BinaryOperator *TheNeg = cast(*UI); + + // Verify that the negate is in this function, V might be a constant expr. + if (TheNeg->getParent()->getParent() != BI->getParent()->getParent()) + continue; + + BasicBlock::iterator InsertPt; + if (Instruction *InstInput = dyn_cast(V)) { + if (InvokeInst *II = dyn_cast(InstInput)) { + InsertPt = II->getNormalDest()->begin(); + } else { + InsertPt = InstInput; + ++InsertPt; + } + while (isa(InsertPt)) ++InsertPt; + } else { + InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin(); + } + TheNeg->moveBefore(InsertPt); + return TheNeg; + } // Insert a 'neg' instruction that subtracts the value from zero to get the // negation. - // - return BinaryOperator::createNeg(V, V->getName() + ".neg", BI); + return BinaryOperator::CreateNeg(V, V->getName() + ".neg", BI); } -/// isReassociableOp - Return true if V is an instruction of the specified -/// opcode and if it only has one use. -static bool isReassociableOp(Value *V, unsigned Opcode) { - return V->hasOneUse() && isa(V) && - cast(V)->getOpcode() == Opcode; +/// ShouldBreakUpSubtract - Return true if we should break up this subtract of +/// X-Y into (X + -Y). +static bool ShouldBreakUpSubtract(Instruction *Sub) { + // If this is a negation, we can't split it up! + if (BinaryOperator::isNeg(Sub)) + return false; + + // Don't bother to break this up unless either the LHS is an associable add or + // subtract or if this is only used by one. + if (isReassociableOp(Sub->getOperand(0), Instruction::Add) || + isReassociableOp(Sub->getOperand(0), Instruction::Sub)) + return true; + if (isReassociableOp(Sub->getOperand(1), Instruction::Add) || + isReassociableOp(Sub->getOperand(1), Instruction::Sub)) + return true; + if (Sub->hasOneUse() && + (isReassociableOp(Sub->use_back(), Instruction::Add) || + isReassociableOp(Sub->use_back(), Instruction::Sub))) + return true; + + return false; } /// BreakUpSubtract - If we have (X-Y), and if either X is an add, or if this is /// only used by an add, transform this into (X+(0-Y)) to promote better /// reassociation. -static Instruction *BreakUpSubtract(Instruction *Sub) { - // Reject cases where it is pointless to do this. - if (Sub->getType()->isFloatingPoint()) - return 0; // Floating point adds are not associative. - - // Don't bother to break this up unless either the LHS is an associable add or - // if this is only used by one. - if (!isReassociableOp(Sub->getOperand(0), Instruction::Add) && - !isReassociableOp(Sub->getOperand(1), Instruction::Add) && - !(Sub->hasOneUse() &&isReassociableOp(Sub->use_back(), Instruction::Add))) - return 0; - - // Convert a subtract into an add and a neg instruction... so that sub - // instructions can be commuted with other add instructions... +static Instruction *BreakUpSubtract(Instruction *Sub, + DenseMap, unsigned> &ValueRankMap) { + // Convert a subtract into an add and a neg instruction. This allows sub + // instructions to be commuted with other add instructions. // - // Calculate the negative value of Operand 1 of the sub instruction... - // and set it as the RHS of the add instruction we just made... + // Calculate the negative value of Operand 1 of the sub instruction, + // and set it as the RHS of the add instruction we just made. // - std::string Name = Sub->getName(); - Sub->setName(""); Value *NegVal = NegateValue(Sub->getOperand(1), Sub); Instruction *New = - BinaryOperator::createAdd(Sub->getOperand(0), NegVal, Name, Sub); + BinaryOperator::CreateAdd(Sub->getOperand(0), NegVal, "", Sub); + New->takeName(Sub); // Everyone now refers to the add instruction. + ValueRankMap.erase(Sub); Sub->replaceAllUsesWith(New); Sub->eraseFromParent(); - - DEBUG(std::cerr << "Negated: " << *New); + + DEBUG(errs() << "Negated: " << *New << '\n'); return New; } /// ConvertShiftToMul - If this is a shift of a reassociable multiply or is used /// by one, change this into a multiply by a constant to assist with further /// reassociation. -static Instruction *ConvertShiftToMul(Instruction *Shl) { - if (!isReassociableOp(Shl->getOperand(0), Instruction::Mul) && - !(Shl->hasOneUse() && isReassociableOp(Shl->use_back(),Instruction::Mul))) +static Instruction *ConvertShiftToMul(Instruction *Shl, + DenseMap, unsigned> &ValueRankMap) { + // If an operand of this shift is a reassociable multiply, or if the shift + // is used by a reassociable multiply or add, turn into a multiply. + if (isReassociableOp(Shl->getOperand(0), Instruction::Mul) || + (Shl->hasOneUse() && + (isReassociableOp(Shl->use_back(), Instruction::Mul) || + isReassociableOp(Shl->use_back(), Instruction::Add)))) { + Constant *MulCst = ConstantInt::get(Shl->getType(), 1); + MulCst = ConstantExpr::getShl(MulCst, cast(Shl->getOperand(1))); + + Instruction *Mul = + BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl); + ValueRankMap.erase(Shl); + Mul->takeName(Shl); + Shl->replaceAllUsesWith(Mul); + Shl->eraseFromParent(); + return Mul; + } + return 0; +} + +// Scan backwards and forwards among values with the same rank as element i to +// see if X exists. If X does not exist, return i. This is useful when +// scanning for 'x' when we see '-x' because they both get the same rank. +static unsigned FindInOperandList(SmallVectorImpl &Ops, unsigned i, + Value *X) { + unsigned XRank = Ops[i].Rank; + unsigned e = Ops.size(); + for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) + if (Ops[j].Op == X) + return j; + // Scan backwards. + for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) + if (Ops[j].Op == X) + return j; + return i; +} + +/// EmitAddTreeOfValues - Emit a tree of add instructions, summing Ops together +/// and returning the result. Insert the tree before I. +static Value *EmitAddTreeOfValues(Instruction *I, SmallVectorImpl &Ops){ + if (Ops.size() == 1) return Ops.back(); + + Value *V1 = Ops.back(); + Ops.pop_back(); + Value *V2 = EmitAddTreeOfValues(I, Ops); + return BinaryOperator::CreateAdd(V2, V1, "tmp", I); +} + +/// RemoveFactorFromExpression - If V is an expression tree that is a +/// multiplication sequence, and if this sequence contains a multiply by Factor, +/// remove Factor from the tree and return the new tree. +Value *Reassociate::RemoveFactorFromExpression(Value *V, Value *Factor) { + BinaryOperator *BO = isReassociableOp(V, Instruction::Mul); + if (!BO) return 0; + + SmallVector Factors; + LinearizeExprTree(BO, Factors); + + bool FoundFactor = false; + bool NeedsNegate = false; + for (unsigned i = 0, e = Factors.size(); i != e; ++i) { + if (Factors[i].Op == Factor) { + FoundFactor = true; + Factors.erase(Factors.begin()+i); + break; + } + + // If this is a negative version of this factor, remove it. + if (ConstantInt *FC1 = dyn_cast(Factor)) + if (ConstantInt *FC2 = dyn_cast(Factors[i].Op)) + if (FC1->getValue() == -FC2->getValue()) { + FoundFactor = NeedsNegate = true; + Factors.erase(Factors.begin()+i); + break; + } + } + + if (!FoundFactor) { + // Make sure to restore the operands to the expression tree. + RewriteExprTree(BO, Factors); return 0; + } + + BasicBlock::iterator InsertPt = BO; ++InsertPt; + + // If this was just a single multiply, remove the multiply and return the only + // remaining operand. + if (Factors.size() == 1) { + ValueRankMap.erase(BO); + BO->eraseFromParent(); + V = Factors[0].Op; + } else { + RewriteExprTree(BO, Factors); + V = BO; + } + + if (NeedsNegate) + V = BinaryOperator::CreateNeg(V, "neg", InsertPt); + + return V; +} - Constant *MulCst = ConstantInt::get(Shl->getType(), 1); - MulCst = ConstantExpr::getShl(MulCst, cast(Shl->getOperand(1))); +/// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively +/// add its operands as factors, otherwise add V to the list of factors. +static void FindSingleUseMultiplyFactors(Value *V, + SmallVectorImpl &Factors) { + BinaryOperator *BO; + if ((!V->hasOneUse() && !V->use_empty()) || + !(BO = dyn_cast(V)) || + BO->getOpcode() != Instruction::Mul) { + Factors.push_back(V); + return; + } + + // Otherwise, add the LHS and RHS to the list of factors. + FindSingleUseMultiplyFactors(BO->getOperand(1), Factors); + FindSingleUseMultiplyFactors(BO->getOperand(0), Factors); +} - std::string Name = Shl->getName(); Shl->setName(""); - Instruction *Mul = BinaryOperator::createMul(Shl->getOperand(0), MulCst, - Name, Shl); - Shl->replaceAllUsesWith(Mul); - Shl->eraseFromParent(); - return Mul; +/// OptimizeAndOrXor - Optimize a series of operands to an 'and', 'or', or 'xor' +/// instruction. This optimizes based on identities. If it can be reduced to +/// a single Value, it is returned, otherwise the Ops list is mutated as +/// necessary. +static Value *OptimizeAndOrXor(unsigned Opcode, + SmallVectorImpl &Ops) { + // Scan the operand lists looking for X and ~X pairs, along with X,X pairs. + // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1. + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + // First, check for X and ~X in the operand list. + assert(i < Ops.size()); + if (BinaryOperator::isNot(Ops[i].Op)) { // Cannot occur for ^. + Value *X = BinaryOperator::getNotArgument(Ops[i].Op); + unsigned FoundX = FindInOperandList(Ops, i, X); + if (FoundX != i) { + if (Opcode == Instruction::And) // ...&X&~X = 0 + return Constant::getNullValue(X->getType()); + + if (Opcode == Instruction::Or) // ...|X|~X = -1 + return Constant::getAllOnesValue(X->getType()); + } + } + + // Next, check for duplicate pairs of values, which we assume are next to + // each other, due to our sorting criteria. + assert(i < Ops.size()); + if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) { + if (Opcode == Instruction::And || Opcode == Instruction::Or) { + // Drop duplicate values for And and Or. + Ops.erase(Ops.begin()+i); + --i; --e; + ++NumAnnihil; + continue; + } + + // Drop pairs of values for Xor. + assert(Opcode == Instruction::Xor); + if (e == 2) + return Constant::getNullValue(Ops[0].Op->getType()); + + // Y ^ X^X -> Y + Ops.erase(Ops.begin()+i, Ops.begin()+i+2); + i -= 1; e -= 2; + ++NumAnnihil; + } + } + return 0; +} + +/// OptimizeAdd - Optimize a series of operands to an 'add' instruction. This +/// optimizes based on identities. If it can be reduced to a single Value, it +/// is returned, otherwise the Ops list is mutated as necessary. +Value *Reassociate::OptimizeAdd(Instruction *I, + SmallVectorImpl &Ops) { + // Scan the operand lists looking for X and -X pairs. If we find any, we + // can simplify the expression. X+-X == 0. While we're at it, scan for any + // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z. + // + // TODO: We could handle "X + ~X" -> "-1" if we wanted, since "-X = ~X+1". + // + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + Value *TheOp = Ops[i].Op; + // Check to see if we've seen this operand before. If so, we factor all + // instances of the operand together. Due to our sorting criteria, we know + // that these need to be next to each other in the vector. + if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) { + // Rescan the list, remove all instances of this operand from the expr. + unsigned NumFound = 0; + do { + Ops.erase(Ops.begin()+i); + ++NumFound; + } while (i != Ops.size() && Ops[i].Op == TheOp); + + DEBUG(errs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n'); + ++NumFactor; + + // Insert a new multiply. + Value *Mul = ConstantInt::get(cast(I->getType()), NumFound); + Mul = BinaryOperator::CreateMul(TheOp, Mul, "factor", I); + + // Now that we have inserted a multiply, optimize it. This allows us to + // handle cases that require multiple factoring steps, such as this: + // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6 + Mul = ReassociateExpression(cast(Mul)); + + // If every add operand was a duplicate, return the multiply. + if (Ops.empty()) + return Mul; + + // Otherwise, we had some input that didn't have the dupe, such as + // "A + A + B" -> "A*2 + B". Add the new multiply to the list of + // things being added by this operation. + Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul)); + + --i; + e = Ops.size(); + continue; + } + + // Check for X and -X in the operand list. + if (!BinaryOperator::isNeg(TheOp)) + continue; + + Value *X = BinaryOperator::getNegArgument(TheOp); + unsigned FoundX = FindInOperandList(Ops, i, X); + if (FoundX == i) + continue; + + // Remove X and -X from the operand list. + if (Ops.size() == 2) + return Constant::getNullValue(X->getType()); + + Ops.erase(Ops.begin()+i); + if (i < FoundX) + --FoundX; + else + --i; // Need to back up an extra one. + Ops.erase(Ops.begin()+FoundX); + ++NumAnnihil; + --i; // Revisit element. + e -= 2; // Removed two elements. + } + + // Scan the operand list, checking to see if there are any common factors + // between operands. Consider something like A*A+A*B*C+D. We would like to + // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies. + // To efficiently find this, we count the number of times a factor occurs + // for any ADD operands that are MULs. + DenseMap FactorOccurrences; + + // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4) + // where they are actually the same multiply. + unsigned MaxOcc = 0; + Value *MaxOccVal = 0; + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + BinaryOperator *BOp = dyn_cast(Ops[i].Op); + if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty()) + continue; + + // Compute all of the factors of this added value. + SmallVector Factors; + FindSingleUseMultiplyFactors(BOp, Factors); + assert(Factors.size() > 1 && "Bad linearize!"); + + // Add one to FactorOccurrences for each unique factor in this op. + SmallPtrSet Duplicates; + for (unsigned i = 0, e = Factors.size(); i != e; ++i) { + Value *Factor = Factors[i]; + if (!Duplicates.insert(Factor)) continue; + + unsigned Occ = ++FactorOccurrences[Factor]; + if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factor; } + + // If Factor is a negative constant, add the negated value as a factor + // because we can percolate the negate out. Watch for minint, which + // cannot be positivified. + if (ConstantInt *CI = dyn_cast(Factor)) + if (CI->getValue().isNegative() && !CI->getValue().isMinSignedValue()) { + Factor = ConstantInt::get(CI->getContext(), -CI->getValue()); + assert(!Duplicates.count(Factor) && + "Shouldn't have two constant factors, missed a canonicalize"); + + unsigned Occ = ++FactorOccurrences[Factor]; + if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factor; } + } + } + } + + // If any factor occurred more than one time, we can pull it out. + if (MaxOcc > 1) { + DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n'); + ++NumFactor; + + // Create a new instruction that uses the MaxOccVal twice. If we don't do + // this, we could otherwise run into situations where removing a factor + // from an expression will drop a use of maxocc, and this can cause + // RemoveFactorFromExpression on successive values to behave differently. + Instruction *DummyInst = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal); + SmallVector NewMulOps; + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) { + NewMulOps.push_back(V); + Ops.erase(Ops.begin()+i); + --i; --e; + } + } + + // No need for extra uses anymore. + delete DummyInst; + + unsigned NumAddedValues = NewMulOps.size(); + Value *V = EmitAddTreeOfValues(I, NewMulOps); + + // Now that we have inserted the add tree, optimize it. This allows us to + // handle cases that require multiple factoring steps, such as this: + // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C)) + assert(NumAddedValues > 1 && "Each occurrence should contribute a value"); + V = ReassociateExpression(cast(V)); + + // Create the multiply. + Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I); + + // Rerun associate on the multiply in case the inner expression turned into + // a multiply. We want to make sure that we keep things in canonical form. + V2 = ReassociateExpression(cast(V2)); + + // If every add operand included the factor (e.g. "A*B + A*C"), then the + // entire result expression is just the multiply "A*(B+C)". + if (Ops.empty()) + return V2; + + // Otherwise, we had some input that didn't have the factor, such as + // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of + // things being added by this operation. + Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2)); + } + + return 0; +} + +Value *Reassociate::OptimizeExpression(BinaryOperator *I, + SmallVectorImpl &Ops) { + // Now that we have the linearized expression tree, try to optimize it. + // Start by folding any constants that we found. + bool IterateOptimization = false; + if (Ops.size() == 1) return Ops[0].Op; + + unsigned Opcode = I->getOpcode(); + + if (Constant *V1 = dyn_cast(Ops[Ops.size()-2].Op)) + if (Constant *V2 = dyn_cast(Ops.back().Op)) { + Ops.pop_back(); + Ops.back().Op = ConstantExpr::get(Opcode, V1, V2); + return OptimizeExpression(I, Ops); + } + + // Check for destructive annihilation due to a constant being used. + if (ConstantInt *CstVal = dyn_cast(Ops.back().Op)) + switch (Opcode) { + default: break; + case Instruction::And: + if (CstVal->isZero()) // X & 0 -> 0 + return CstVal; + if (CstVal->isAllOnesValue()) // X & -1 -> X + Ops.pop_back(); + break; + case Instruction::Mul: + if (CstVal->isZero()) { // X * 0 -> 0 + ++NumAnnihil; + return CstVal; + } + + if (cast(CstVal)->isOne()) + Ops.pop_back(); // X * 1 -> X + break; + case Instruction::Or: + if (CstVal->isAllOnesValue()) // X | -1 -> -1 + return CstVal; + // FALLTHROUGH! + case Instruction::Add: + case Instruction::Xor: + if (CstVal->isZero()) // X [|^+] 0 -> X + Ops.pop_back(); + break; + } + if (Ops.size() == 1) return Ops[0].Op; + + // Handle destructive annihilation due to identities between elements in the + // argument list here. + switch (Opcode) { + default: break; + case Instruction::And: + case Instruction::Or: + case Instruction::Xor: { + unsigned NumOps = Ops.size(); + if (Value *Result = OptimizeAndOrXor(Opcode, Ops)) + return Result; + IterateOptimization |= Ops.size() != NumOps; + break; + } + + case Instruction::Add: { + unsigned NumOps = Ops.size(); + if (Value *Result = OptimizeAdd(I, Ops)) + return Result; + IterateOptimization |= Ops.size() != NumOps; + } + + break; + //case Instruction::Mul: + } + + if (IterateOptimization) + return OptimizeExpression(I, Ops); + return 0; } /// ReassociateBB - Inspect all of the instructions in this basic block, /// reassociating them as we go. -bool Reassociate::ReassociateBB(BasicBlock *BB) { - bool Changed = false; - for (BasicBlock::iterator BI = BB->begin(); BI != BB->end(); ++BI) { - // If this is a subtract instruction which is not already in negate form, - // see if we can convert it to X+-Y. - if (BI->getOpcode() == Instruction::Sub && !BinaryOperator::isNeg(BI)) - if (Instruction *NI = BreakUpSubtract(BI)) { - Changed = true; - BI = NI; - } +void Reassociate::ReassociateBB(BasicBlock *BB) { + for (BasicBlock::iterator BBI = BB->begin(); BBI != BB->end(); ) { + Instruction *BI = BBI++; if (BI->getOpcode() == Instruction::Shl && isa(BI->getOperand(1))) - if (Instruction *NI = ConvertShiftToMul(BI)) { - Changed = true; + if (Instruction *NI = ConvertShiftToMul(BI, ValueRankMap)) { + MadeChange = true; BI = NI; } - // If this instruction is a commutative binary operator, and the ranks of - // the two operands are sorted incorrectly, fix it now. - // - if (BI->isAssociative()) { - DEBUG(std::cerr << "Reassociating: " << *BI); - BinaryOperator *I = cast(BI); - if (!I->use_empty()) { - // Make sure that we don't have a tree-shaped computation. If we do, - // linearize it. Convert (A+B)+(C+D) into ((A+B)+C)+D - // - Instruction *LHSI = dyn_cast(I->getOperand(0)); - Instruction *RHSI = dyn_cast(I->getOperand(1)); - if (LHSI && (int)LHSI->getOpcode() == I->getOpcode() && - RHSI && (int)RHSI->getOpcode() == I->getOpcode() && - RHSI->hasOneUse()) { - // Insert a new temporary instruction... (A+B)+C - BinaryOperator *Tmp = BinaryOperator::create(I->getOpcode(), LHSI, - RHSI->getOperand(0), - RHSI->getName()+".ra", - BI); - BI = Tmp; - I->setOperand(0, Tmp); - I->setOperand(1, RHSI->getOperand(1)); - - // Process the temporary instruction for reassociation now. - I = Tmp; - ++NumLinear; - Changed = true; - DEBUG(std::cerr << "Linearized: " << *I/* << " Result BB: " << BB*/); - } + // Reject cases where it is pointless to do this. + if (!isa(BI) || BI->getType()->isFloatingPoint() || + isa(BI->getType())) + continue; // Floating point ops are not associative. - // Make sure that this expression is correctly reassociated with respect - // to it's used values... - // - Changed |= ReassociateExpr(I); + // If this is a subtract instruction which is not already in negate form, + // see if we can convert it to X+-Y. + if (BI->getOpcode() == Instruction::Sub) { + if (ShouldBreakUpSubtract(BI)) { + BI = BreakUpSubtract(BI, ValueRankMap); + MadeChange = true; + } else if (BinaryOperator::isNeg(BI)) { + // Otherwise, this is a negation. See if the operand is a multiply tree + // and if this is not an inner node of a multiply tree. + if (isReassociableOp(BI->getOperand(1), Instruction::Mul) && + (!BI->hasOneUse() || + !isReassociableOp(BI->use_back(), Instruction::Mul))) { + BI = LowerNegateToMultiply(BI, ValueRankMap); + MadeChange = true; + } } } + + // If this instruction is a commutative binary operator, process it. + if (!BI->isAssociative()) continue; + BinaryOperator *I = cast(BI); + + // If this is an interior node of a reassociable tree, ignore it until we + // get to the root of the tree, to avoid N^2 analysis. + if (I->hasOneUse() && isReassociableOp(I->use_back(), I->getOpcode())) + continue; + + // If this is an add tree that is used by a sub instruction, ignore it + // until we process the subtract. + if (I->hasOneUse() && I->getOpcode() == Instruction::Add && + cast(I->use_back())->getOpcode() == Instruction::Sub) + continue; + + ReassociateExpression(I); } +} - return Changed; +Value *Reassociate::ReassociateExpression(BinaryOperator *I) { + + // First, walk the expression tree, linearizing the tree, collecting the + // operand information. + SmallVector Ops; + LinearizeExprTree(I, Ops); + + DEBUG(errs() << "RAIn:\t"; PrintOps(I, Ops); errs() << '\n'); + + // Now that we have linearized the tree to a list and have gathered all of + // the operands and their ranks, sort the operands by their rank. Use a + // stable_sort so that values with equal ranks will have their relative + // positions maintained (and so the compiler is deterministic). Note that + // this sorts so that the highest ranking values end up at the beginning of + // the vector. + std::stable_sort(Ops.begin(), Ops.end()); + + // OptimizeExpression - Now that we have the expression tree in a convenient + // sorted form, optimize it globally if possible. + if (Value *V = OptimizeExpression(I, Ops)) { + // This expression tree simplified to something that isn't a tree, + // eliminate it. + DEBUG(errs() << "Reassoc to scalar: " << *V << '\n'); + I->replaceAllUsesWith(V); + RemoveDeadBinaryOp(I); + ++NumAnnihil; + return V; + } + + // We want to sink immediates as deeply as possible except in the case where + // this is a multiply tree used only by an add, and the immediate is a -1. + // In this case we reassociate to put the negation on the outside so that we + // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y + if (I->getOpcode() == Instruction::Mul && I->hasOneUse() && + cast(I->use_back())->getOpcode() == Instruction::Add && + isa(Ops.back().Op) && + cast(Ops.back().Op)->isAllOnesValue()) { + ValueEntry Tmp = Ops.pop_back_val(); + Ops.insert(Ops.begin(), Tmp); + } + + DEBUG(errs() << "RAOut:\t"; PrintOps(I, Ops); errs() << '\n'); + + if (Ops.size() == 1) { + // This expression tree simplified to something that isn't a tree, + // eliminate it. + I->replaceAllUsesWith(Ops[0].Op); + RemoveDeadBinaryOp(I); + return Ops[0].Op; + } + + // Now that we ordered and optimized the expressions, splat them back into + // the expression tree, removing any unneeded nodes. + RewriteExprTree(I, Ops); + return I; } @@ -329,13 +1026,13 @@ bool Reassociate::runOnFunction(Function &F) { // Recalculate the rank map for F BuildRankMap(F); - bool Changed = false; + MadeChange = false; for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) - Changed |= ReassociateBB(FI); + ReassociateBB(FI); - // We are done with the rank map... + // We are done with the rank map. RankMap.clear(); ValueRankMap.clear(); - return Changed; + return MadeChange; }