X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FScalar%2FReassociate.cpp;h=6ef0c97d3753338bf3ff21da4f5040089f7c662a;hb=a33701098936ffba12326d96e98d388357f3e098;hp=4fcbf35f5675becf3883ec6a4ce5d0d93b6cdda9;hpb=24d6da5fedcf39891f7d8c5b031c01324b3db545;p=oota-llvm.git diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp index 4fcbf35f567..6ef0c97d375 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) // @@ -22,16 +22,23 @@ #define DEBUG_TYPE "reassociate" #include "llvm/Transforms/Scalar.h" +#include "llvm/Transforms/Utils/Local.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/Assembly/Writer.h" #include "llvm/Support/CFG.h" +#include "llvm/Support/IRBuilder.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/STLExtras.h" #include "llvm/ADT/Statistic.h" +#include "llvm/ADT/DenseMap.h" #include using namespace llvm; @@ -51,23 +58,73 @@ namespace { } } +#ifndef NDEBUG /// PrintOps - Print out the expression identified in the Ops list. /// -static void PrintOps(Instruction *I, const std::vector &Ops) { +static void PrintOps(Instruction *I, const SmallVectorImpl &Ops) { Module *M = I->getParent()->getParent()->getParent(); - cerr << Instruction::getOpcodeName(I->getOpcode()) << " " - << *Ops[0].Op->getType(); - for (unsigned i = 0, e = Ops.size(); i != e; ++i) - WriteAsOperand(*cerr.stream() << " ", Ops[i].Op, false, M) - << "," << Ops[i].Rank; -} - -namespace { + dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " " + << *Ops[0].Op->getType() << '\t'; + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + dbgs() << "[ "; + WriteAsOperand(dbgs(), Ops[i].Op, false, M); + dbgs() << ", #" << Ops[i].Rank << "] "; + } +} +#endif + +namespace { + /// \brief Utility class representing a base and exponent pair which form one + /// factor of some product. + struct Factor { + Value *Base; + unsigned Power; + + Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {} + + /// \brief Sort factors by their Base. + struct BaseSorter { + bool operator()(const Factor &LHS, const Factor &RHS) { + return LHS.Base < RHS.Base; + } + }; + + /// \brief Compare factors for equal bases. + struct BaseEqual { + bool operator()(const Factor &LHS, const Factor &RHS) { + return LHS.Base == RHS.Base; + } + }; + + /// \brief Sort factors in descending order by their power. + struct PowerDescendingSorter { + bool operator()(const Factor &LHS, const Factor &RHS) { + return LHS.Power > RHS.Power; + } + }; + + /// \brief Compare factors for equal powers. + struct PowerEqual { + bool operator()(const Factor &LHS, const Factor &RHS) { + return LHS.Power == RHS.Power; + } + }; + }; +} + +namespace { class Reassociate : public FunctionPass { - std::map RankMap; - std::map ValueRankMap; + DenseMap RankMap; + DenseMap, unsigned> ValueRankMap; + SmallVector RedoInsts; + SmallVector DeadInsts; bool MadeChange; public: + static char ID; // Pass identification, replacement for typeid + Reassociate() : FunctionPass(ID) { + initializeReassociatePass(*PassRegistry::getPassRegistry()); + } + bool runOnFunction(Function &F); virtual void getAnalysisUsage(AnalysisUsage &AU) const { @@ -76,43 +133,55 @@ namespace { private: void BuildRankMap(Function &F); unsigned getRank(Value *V); - void ReassociateExpression(BinaryOperator *I); - void RewriteExprTree(BinaryOperator *I, std::vector &Ops, + Value *ReassociateExpression(BinaryOperator *I); + void RewriteExprTree(BinaryOperator *I, SmallVectorImpl &Ops, unsigned Idx = 0); - Value *OptimizeExpression(BinaryOperator *I, std::vector &Ops); - void LinearizeExprTree(BinaryOperator *I, std::vector &Ops); + Value *OptimizeExpression(BinaryOperator *I, + SmallVectorImpl &Ops); + Value *OptimizeAdd(Instruction *I, SmallVectorImpl &Ops); + bool collectMultiplyFactors(SmallVectorImpl &Ops, + SmallVectorImpl &Factors); + Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder, + SmallVectorImpl &Factors); + Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl &Ops); + void LinearizeExprTree(BinaryOperator *I, SmallVectorImpl &Ops); void LinearizeExpr(BinaryOperator *I); Value *RemoveFactorFromExpression(Value *V, Value *Factor); - void ReassociateBB(BasicBlock *BB); - + void ReassociateInst(BasicBlock::iterator &BBI); + void RemoveDeadBinaryOp(Value *V); }; - - RegisterPass X("reassociate", "Reassociate expressions"); } +char Reassociate::ID = 0; +INITIALIZE_PASS(Reassociate, "reassociate", + "Reassociate expressions", false, false) + // 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) || !isa(Op) || !Op->use_empty()) + if (!Op || !isa(Op)) return; - + Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1); + + ValueRankMap.erase(Op); + DeadInsts.push_back(Op); RemoveDeadBinaryOp(LHS); RemoveDeadBinaryOp(RHS); } - static bool isUnmovableInstruction(Instruction *I) { if (I->getOpcode() == Instruction::PHI || + I->getOpcode() == Instruction::LandingPad || I->getOpcode() == Instruction::Alloca || I->getOpcode() == Instruction::Load || - I->getOpcode() == Instruction::Malloc || I->getOpcode() == Instruction::Invoke || - I->getOpcode() == Instruction::Call || - I->getOpcode() == Instruction::UDiv || + (I->getOpcode() == Instruction::Call && + !isa(I)) || + I->getOpcode() == Instruction::UDiv || I->getOpcode() == Instruction::SDiv || I->getOpcode() == Instruction::FDiv || I->getOpcode() == Instruction::URem || @@ -127,7 +196,7 @@ void Reassociate::BuildRankMap(Function &F) { // 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(), @@ -140,18 +209,19 @@ void Reassociate::BuildRankMap(Function &F) { // all different in the block. for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) if (isUnmovableInstruction(I)) - ValueRankMap[I] = ++BBRank; + 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. + } - unsigned &CachedRank = ValueRankMap[I]; - if (CachedRank) return CachedRank; // Rank already known? + if (unsigned Rank = ValueRankMap[I]) + return Rank; // 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 @@ -164,14 +234,14 @@ unsigned Reassociate::getRank(Value *V) { // 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() || + if (!I->getType()->isIntegerTy() || (!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I))) ++Rank; - //DOUT << "Calculated Rank[" << V->getName() << "] = " - // << Rank << "\n"; + //DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " + // << Rank << "\n"); - return CachedRank = Rank; + return ValueRankMap[I] = Rank; } /// isReassociableOp - Return true if V is an instruction of the specified @@ -185,13 +255,15 @@ static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) { /// LowerNegateToMultiply - Replace 0-X with X*-1. /// -static Instruction *LowerNegateToMultiply(Instruction *Neg) { - Constant *Cst = ConstantInt::getAllOnesValue(Neg->getType()); +static Instruction *LowerNegateToMultiply(Instruction *Neg, + DenseMap, unsigned> &ValueRankMap) { + Constant *Cst = Constant::getAllOnesValue(Neg->getType()); - std::string NegName = Neg->getName(); Neg->setName(""); - Instruction *Res = BinaryOperator::createMul(Neg->getOperand(1), Cst, NegName, - Neg); + Instruction *Res = BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg); + ValueRankMap.erase(Neg); + Res->takeName(Neg); Neg->replaceAllUsesWith(Res); + Res->setDebugLoc(Neg->getDebugLoc()); Neg->eraseFromParent(); return Res; } @@ -201,13 +273,14 @@ static Instruction *LowerNegateToMultiply(Instruction *Neg) { // 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?"); + BinaryOperator *LHS = isReassociableOp(I->getOperand(0), I->getOpcode()); + BinaryOperator *RHS = isReassociableOp(I->getOperand(1), I->getOpcode()); + assert(LHS && RHS && "Not an expression that needs linearization?"); - DOUT << "Linear" << *LHS << *RHS << *I; + DEBUG({ + dbgs() << "Linear:\n"; + dbgs() << '\t' << *LHS << "\t\n" << *RHS << "\t\n" << *I << '\n'; + }); // Move the RHS instruction to live immediately before I, avoiding breaking // dominator properties. @@ -218,19 +291,24 @@ void Reassociate::LinearizeExpr(BinaryOperator *I) { RHS->setOperand(0, LHS); I->setOperand(0, RHS); + // Conservatively clear all the optional flags, which may not hold + // after the reassociation. + I->clearSubclassOptionalData(); + LHS->clearSubclassOptionalData(); + RHS->clearSubclassOptionalData(); + ++NumLinear; MadeChange = true; - DOUT << "Linearized: " << *I; + DEBUG(dbgs() << "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 +/// form of 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 @@ -238,7 +316,7 @@ void Reassociate::LinearizeExpr(BinaryOperator *I) { /// caller MUST use something like RewriteExprTree to put the values back in. /// void Reassociate::LinearizeExprTree(BinaryOperator *I, - std::vector &Ops) { + SmallVectorImpl &Ops) { Value *LHS = I->getOperand(0), *RHS = I->getOperand(1); unsigned Opcode = I->getOpcode(); @@ -250,11 +328,11 @@ void Reassociate::LinearizeExprTree(BinaryOperator *I, // 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)); + LHS = LowerNegateToMultiply(cast(LHS), ValueRankMap); LHSBO = isReassociableOp(LHS, Opcode); } if (!RHSBO && RHS->hasOneUse() && BinaryOperator::isNeg(RHS)) { - RHS = LowerNegateToMultiply(cast(RHS)); + RHS = LowerNegateToMultiply(cast(RHS), ValueRankMap); RHSBO = isReassociableOp(RHS, Opcode); } } @@ -265,21 +343,22 @@ void Reassociate::LinearizeExprTree(BinaryOperator *I, // 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; - } else { - // Turn X+(Y+Z) -> (Y+Z)+X - std::swap(LHSBO, RHSBO); - std::swap(LHS, RHS); - bool Success = !I->swapOperands(); - assert(Success && "swapOperands failed"); - MadeChange = true; } + + // Turn X+(Y+Z) -> (Y+Z)+X + std::swap(LHSBO, RHSBO); + std::swap(LHS, RHS); + bool Success = !I->swapOperands(); + assert(Success && "swapOperands failed"); + (void)Success; + MadeChange = true; } else if (RHSBO) { - // Turn (A+B)+(C+D) -> (((A+B)+C)+D). This guarantees the the RHS is not + // Turn (A+B)+(C+D) -> (((A+B)+C)+D). This guarantees the RHS is not // part of the expression tree. LinearizeExpr(I); LHS = LHSBO = cast(I->getOperand(0)); @@ -300,7 +379,7 @@ void Reassociate::LinearizeExprTree(BinaryOperator *I, // 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())); } @@ -309,19 +388,25 @@ void Reassociate::LinearizeExprTree(BinaryOperator *I, // linearized and optimized, emit them in-order. This function is written to be // tail recursive. void Reassociate::RewriteExprTree(BinaryOperator *I, - std::vector &Ops, + 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); - DOUT << "RA: " << *I; + DEBUG(dbgs() << "RA: " << *I << '\n'); I->setOperand(0, Ops[i].Op); I->setOperand(1, Ops[i+1].Op); - DOUT << "TO: " << *I; + + // Clear all the optional flags, which may not hold after the + // reassociation if the expression involved more than just this operation. + if (Ops.size() != 2) + I->clearSubclassOptionalData(); + + DEBUG(dbgs() << "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); @@ -331,31 +416,36 @@ void Reassociate::RewriteExprTree(BinaryOperator *I, assert(i+2 < Ops.size() && "Ops index out of range!"); if (I->getOperand(1) != Ops[i].Op) { - DOUT << "RA: " << *I; + DEBUG(dbgs() << "RA: " << *I << '\n'); I->setOperand(1, Ops[i].Op); - DOUT << "TO: " << *I; + + // Conservatively clear all the optional flags, which may not hold + // after the reassociation. + I->clearSubclassOptionalData(); + + DEBUG(dbgs() << "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. -// +/// 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, @@ -363,7 +453,7 @@ 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()) { @@ -373,7 +463,7 @@ static Value *NegateValue(Value *V, Instruction *BI) { // 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 + // assured that the neg instructions we just inserted dominate the // instruction we are about to insert after them. // I->moveBefore(BI); @@ -381,76 +471,130 @@ static Value *NegateValue(Value *V, Instruction *BI) { 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){ + User *U = *UI; + if (!BinaryOperator::isNeg(U)) 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(U); + + // 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); +} + +/// 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) { - // 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); + New->setDebugLoc(Sub->getDebugLoc()); Sub->eraseFromParent(); - DOUT << "Negated: " << *New; + DEBUG(dbgs() << "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) { +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() && + (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))); - - std::string Name = Shl->getName(); Shl->setName(""); - Instruction *Mul = BinaryOperator::createMul(Shl->getOperand(0), MulCst, - Name, Shl); + + Instruction *Mul = + BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl); + ValueRankMap.erase(Shl); + Mul->takeName(Shl); Shl->replaceAllUsesWith(Mul); + Mul->setDebugLoc(Shl->getDebugLoc()); 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. -static unsigned FindInOperandList(std::vector &Ops, unsigned i, +/// FindInOperandList - 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 + // Scan backwards. for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) if (Ops[j].Op == X) return j; @@ -459,72 +603,538 @@ static unsigned FindInOperandList(std::vector &Ops, unsigned 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, std::vector &Ops) { +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); + return BinaryOperator::CreateAdd(V2, V1, "tmp", I); } -/// RemoveFactorFromExpression - If V is an expression tree that is a +/// 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; - - std::vector Factors; + + SmallVector Factors; LinearizeExprTree(BO, Factors); bool FoundFactor = false; - for (unsigned i = 0, e = Factors.size(); i != e; ++i) + 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; } - - if (Factors.size() == 1) return Factors[0].Op; - - RewriteExprTree(BO, Factors); - return BO; + + 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); + DeadInsts.push_back(BO); + V = Factors[0].Op; + } else { + RewriteExprTree(BO, Factors); + V = BO; + } + + if (NeedsNegate) + V = BinaryOperator::CreateNeg(V, "neg", InsertPt); + + return V; } /// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively /// add its operands as factors, otherwise add V to the list of factors. +/// +/// Ops is the top-level list of add operands we're trying to factor. static void FindSingleUseMultiplyFactors(Value *V, - std::vector &Factors) { + SmallVectorImpl &Factors, + const SmallVectorImpl &Ops, + bool IsRoot) { BinaryOperator *BO; - if ((!V->hasOneUse() && !V->use_empty()) || + if (!(V->hasOneUse() || V->use_empty()) || // More than one use. !(BO = dyn_cast(V)) || BO->getOpcode() != Instruction::Mul) { Factors.push_back(V); return; } - + + // If this value has a single use because it is another input to the add + // tree we're reassociating and we dropped its use, it actually has two + // uses and we can't factor it. + if (!IsRoot) { + for (unsigned i = 0, e = Ops.size(); i != e; ++i) + if (Ops[i].Op == V) { + 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); + FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops, false); + FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops, false); +} + +/// 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 + RedoInsts.push_back(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, Ops, true); + 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->isNegative() && !CI->isMinValue(true)) { + 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; i != Ops.size(); ++i) { + // Only try to remove factors from expressions we're allowed to. + BinaryOperator *BOp = dyn_cast(Ops[i].Op); + if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty()) + continue; + + if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) { + // The factorized operand may occur several times. Convert them all in + // one fell swoop. + for (unsigned j = Ops.size(); j != i;) { + --j; + if (Ops[j].Op == Ops[i].Op) { + NewMulOps.push_back(V); + Ops.erase(Ops.begin()+j); + } + } + --i; + } + } + + // 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"); + (void)NumAddedValues; + RedoInsts.push_back(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. + RedoInsts.push_back(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; +} + +namespace { + /// \brief Predicate tests whether a ValueEntry's op is in a map. + struct IsValueInMap { + const DenseMap ⤅ + + IsValueInMap(const DenseMap &Map) : Map(Map) {} + + bool operator()(const ValueEntry &Entry) { + return Map.find(Entry.Op) != Map.end(); + } + }; +} + +/// \brief Build up a vector of value/power pairs factoring a product. +/// +/// Given a series of multiplication operands, build a vector of factors and +/// the powers each is raised to when forming the final product. Sort them in +/// the order of descending power. +/// +/// (x*x) -> [(x, 2)] +/// ((x*x)*x) -> [(x, 3)] +/// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)] +/// +/// \returns Whether any factors have a power greater than one. +bool Reassociate::collectMultiplyFactors(SmallVectorImpl &Ops, + SmallVectorImpl &Factors) { + unsigned FactorPowerSum = 0; + DenseMap FactorCounts; + for (unsigned LastIdx = 0, Idx = 0, Size = Ops.size(); Idx < Size; ++Idx) { + // Note that 'use_empty' uses means the only use is in the linearized tree + // represented by Ops -- we remove the values from the actual operations to + // reduce their use count. + if (!Ops[Idx].Op->use_empty()) { + if (LastIdx == Idx) + ++LastIdx; + continue; + } + if (LastIdx == Idx || Ops[LastIdx].Op != Ops[Idx].Op) { + LastIdx = Idx; + continue; + } + // Track for simplification all factors which occur 2 or more times. + DenseMap::iterator CountIt; + bool Inserted; + llvm::tie(CountIt, Inserted) + = FactorCounts.insert(std::make_pair(Ops[Idx].Op, 2)); + if (Inserted) { + FactorPowerSum += 2; + Factors.push_back(Factor(Ops[Idx].Op, 2)); + } else { + ++CountIt->second; + ++FactorPowerSum; + } + } + // We can only simplify factors if the sum of the powers of our simplifiable + // factors is 4 or higher. When that is the case, we will *always* have + // a simplification. This is an important invariant to prevent cyclicly + // trying to simplify already minimal formations. + if (FactorPowerSum < 4) + return false; + + // Remove all the operands which are in the map. + Ops.erase(std::remove_if(Ops.begin(), Ops.end(), IsValueInMap(FactorCounts)), + Ops.end()); + + // Record the adjusted power for the simplification factors. We add back into + // the Ops list any values with an odd power, and make the power even. This + // allows the outer-most multiplication tree to remain in tact during + // simplification. + unsigned OldOpsSize = Ops.size(); + for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) { + Factors[Idx].Power = FactorCounts[Factors[Idx].Base]; + if (Factors[Idx].Power & 1) { + Ops.push_back(ValueEntry(getRank(Factors[Idx].Base), Factors[Idx].Base)); + --Factors[Idx].Power; + --FactorPowerSum; + } + } + // None of the adjustments above should have reduced the sum of factor powers + // below our mininum of '4'. + assert(FactorPowerSum >= 4); + + // Patch up the sort of the ops vector by sorting the factors we added back + // onto the back, and merging the two sequences. + if (OldOpsSize != Ops.size()) { + SmallVectorImpl::iterator MiddleIt = Ops.begin() + OldOpsSize; + std::sort(MiddleIt, Ops.end()); + std::inplace_merge(Ops.begin(), MiddleIt, Ops.end()); + } + + std::sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter()); + return true; +} + +/// \brief Build a tree of multiplies, computing the product of Ops. +static Value *buildMultiplyTree(IRBuilder<> &Builder, + SmallVectorImpl &Ops) { + if (Ops.size() == 1) + return Ops.back(); + + Value *LHS = Ops.pop_back_val(); + do { + LHS = Builder.CreateMul(LHS, Ops.pop_back_val()); + } while (!Ops.empty()); + + return LHS; +} + +/// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*... +/// +/// Given a vector of values raised to various powers, where no two values are +/// equal and the powers are sorted in decreasing order, compute the minimal +/// DAG of multiplies to compute the final product, and return that product +/// value. +Value *Reassociate::buildMinimalMultiplyDAG(IRBuilder<> &Builder, + SmallVectorImpl &Factors) { + assert(Factors[0].Power); + SmallVector OuterProduct; + for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size(); + Idx < Size && Factors[Idx].Power > 0; ++Idx) { + if (Factors[Idx].Power != Factors[LastIdx].Power) { + LastIdx = Idx; + continue; + } + + // We want to multiply across all the factors with the same power so that + // we can raise them to that power as a single entity. Build a mini tree + // for that. + SmallVector InnerProduct; + InnerProduct.push_back(Factors[LastIdx].Base); + do { + InnerProduct.push_back(Factors[Idx].Base); + ++Idx; + } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power); + + // Reset the base value of the first factor to the new expression tree. + // We'll remove all the factors with the same power in a second pass. + Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct); + RedoInsts.push_back(Factors[LastIdx].Base); + + LastIdx = Idx; + } + // Unique factors with equal powers -- we've folded them into the first one's + // base. + Factors.erase(std::unique(Factors.begin(), Factors.end(), + Factor::PowerEqual()), + Factors.end()); + + // Iteratively collect the base of each factor with an add power into the + // outer product, and halve each power in preparation for squaring the + // expression. + for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) { + if (Factors[Idx].Power & 1) + OuterProduct.push_back(Factors[Idx].Base); + Factors[Idx].Power >>= 1; + } + if (Factors[0].Power) { + Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors); + OuterProduct.push_back(SquareRoot); + OuterProduct.push_back(SquareRoot); + } + if (OuterProduct.size() == 1) + return OuterProduct.front(); + + Value *V = buildMultiplyTree(Builder, OuterProduct); + RedoInsts.push_back(V); + return V; +} + +Value *Reassociate::OptimizeMul(BinaryOperator *I, + SmallVectorImpl &Ops) { + // We can only optimize the multiplies when there is a chain of more than + // three, such that a balanced tree might require fewer total multiplies. + if (Ops.size() < 4) + return 0; + + // Try to turn linear trees of multiplies without other uses of the + // intermediate stages into minimal multiply DAGs with perfect sub-expression + // re-use. + SmallVector Factors; + if (!collectMultiplyFactors(Ops, Factors)) + return 0; // All distinct factors, so nothing left for us to do. + + IRBuilder<> Builder(I); + Value *V = buildMinimalMultiplyDAG(Builder, Factors); + if (Ops.empty()) + return V; + + ValueEntry NewEntry = ValueEntry(getRank(V), V); + Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry); + return 0; +} Value *Reassociate::OptimizeExpression(BinaryOperator *I, - std::vector &Ops) { + 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(); @@ -537,272 +1147,158 @@ Value *Reassociate::OptimizeExpression(BinaryOperator *I, switch (Opcode) { default: break; case Instruction::And: - if (CstVal->isNullValue()) { // ... & 0 -> 0 - ++NumAnnihil; + if (CstVal->isZero()) // X & 0 -> 0 return CstVal; - } else if (CstVal->isAllOnesValue()) { // ... & -1 -> ... + if (CstVal->isAllOnesValue()) // X & -1 -> X Ops.pop_back(); - } break; case Instruction::Mul: - if (CstVal->isNullValue()) { // ... * 0 -> 0 + if (CstVal->isZero()) { // X * 0 -> 0 ++NumAnnihil; return CstVal; - } else if (cast(CstVal)->getZExtValue() == 1) { - Ops.pop_back(); // ... * 1 -> ... } + + if (cast(CstVal)->isOne()) + Ops.pop_back(); // X * 1 -> X break; case Instruction::Or: - if (CstVal->isAllOnesValue()) { // ... | -1 -> -1 - ++NumAnnihil; + if (CstVal->isAllOnesValue()) // X | -1 -> -1 return CstVal; - } // FALLTHROUGH! case Instruction::Add: case Instruction::Xor: - if (CstVal->isNullValue()) // ... [|^+] 0 -> ... + if (CstVal->isZero()) // X [|^+] 0 -> X Ops.pop_back(); break; } if (Ops.size() == 1) return Ops[0].Op; - // Handle destructive annihilation do to identities between elements in the + // Handle destructive annihilation due to identities between elements in the // argument list here. + unsigned NumOps = Ops.size(); switch (Opcode) { default: break; case Instruction::And: case Instruction::Or: case Instruction::Xor: - // 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 - ++NumAnnihil; - return Constant::getNullValue(X->getType()); - } else if (Opcode == Instruction::Or) { // ...|X|~X = -1 - ++NumAnnihil; - return ConstantInt::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. - Ops.erase(Ops.begin()+i); - --i; --e; - IterateOptimization = true; - ++NumAnnihil; - } else { - assert(Opcode == Instruction::Xor); - if (e == 2) { - ++NumAnnihil; - return Constant::getNullValue(Ops[0].Op->getType()); - } - // ... X^X -> ... - Ops.erase(Ops.begin()+i, Ops.begin()+i+2); - i -= 1; e -= 2; - IterateOptimization = true; - ++NumAnnihil; - } - } - } + if (Value *Result = OptimizeAndOrXor(Opcode, Ops)) + return Result; break; case Instruction::Add: - // Scan the operand lists looking for X and -X pairs. If we find any, we - // can simplify the expression. X+-X == 0. - for (unsigned i = 0, e = Ops.size(); i != e; ++i) { - assert(i < Ops.size()); - // Check for X and -X in the operand list. - if (BinaryOperator::isNeg(Ops[i].Op)) { - Value *X = BinaryOperator::getNegArgument(Ops[i].Op); - unsigned FoundX = FindInOperandList(Ops, i, X); - if (FoundX != i) { - // Remove X and -X from the operand list. - if (Ops.size() == 2) { - ++NumAnnihil; - return Constant::getNullValue(X->getType()); - } else { - Ops.erase(Ops.begin()+i); - if (i < FoundX) - --FoundX; - else - --i; // Need to back up an extra one. - Ops.erase(Ops.begin()+FoundX); - IterateOptimization = true; - ++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. - std::map FactorOccurrences; - unsigned MaxOcc = 0; - Value *MaxOccVal = 0; - for (unsigned i = 0, e = Ops.size(); i != e; ++i) { - if (BinaryOperator *BOp = dyn_cast(Ops[i].Op)) { - if (BOp->getOpcode() == Instruction::Mul && BOp->use_empty()) { - // Compute all of the factors of this added value. - std::vector Factors; - FindSingleUseMultiplyFactors(BOp, Factors); - assert(Factors.size() > 1 && "Bad linearize!"); - - // Add one to FactorOccurrences for each unique factor in this op. - if (Factors.size() == 2) { - unsigned Occ = ++FactorOccurrences[Factors[0]]; - if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[0]; } - if (Factors[0] != Factors[1]) { // Don't double count A*A. - Occ = ++FactorOccurrences[Factors[1]]; - if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[1]; } - } - } else { - std::set Duplicates; - for (unsigned i = 0, e = Factors.size(); i != e; ++i) { - if (Duplicates.insert(Factors[i]).second) { - unsigned Occ = ++FactorOccurrences[Factors[i]]; - if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[i]; } - } - } - } - } - } - } + if (Value *Result = OptimizeAdd(I, Ops)) + return Result; + break; - // If any factor occurred more than one time, we can pull it out. - if (MaxOcc > 1) { - DOUT << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << "\n"; - - // 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); - std::vector 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); - Value *V2 = BinaryOperator::createMul(V, MaxOccVal, "tmp", I); - - // Now that we have inserted V and its sole use, 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)) - if (NumAddedValues > 1) - ReassociateExpression(cast(V)); - - ++NumFactor; - - if (Ops.size() == 0) - return V2; - - // Add the new value to the list of things being added. - Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2)); - - // Rewrite the tree so that there is now a use of V. - RewriteExprTree(I, Ops); - return OptimizeExpression(I, Ops); - } + case Instruction::Mul: + if (Value *Result = OptimizeMul(I, Ops)) + return Result; break; - //case Instruction::Mul: } - if (IterateOptimization) + if (IterateOptimization || Ops.size() != NumOps) return OptimizeExpression(I, Ops); return 0; } +/// ReassociateInst - Inspect and reassociate the instruction at the +/// given position, post-incrementing the position. +void Reassociate::ReassociateInst(BasicBlock::iterator &BBI) { + Instruction *BI = BBI++; + if (BI->getOpcode() == Instruction::Shl && + isa(BI->getOperand(1))) + if (Instruction *NI = ConvertShiftToMul(BI, ValueRankMap)) { + MadeChange = true; + BI = NI; + } -/// ReassociateBB - Inspect all of the instructions in this basic block, -/// reassociating them as we go. -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)) { - MadeChange = true; - BI = NI; - } + // Floating point binary operators are not associative, but we can still + // commute (some) of them, to canonicalize the order of their operands. + // This can potentially expose more CSE opportunities, and makes writing + // other transformations simpler. + if (isa(BI) && + (BI->getType()->isFloatingPointTy() || BI->getType()->isVectorTy())) { + // FAdd and FMul can be commuted. + if (BI->getOpcode() != Instruction::FMul && + BI->getOpcode() != Instruction::FAdd) + return; - // 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. - - // 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 (!BinaryOperator::isNeg(BI)) { - if (Instruction *NI = BreakUpSubtract(BI)) { - MadeChange = true; - BI = NI; - } - } else { - // 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); - MadeChange = true; - } - } + Value *LHS = BI->getOperand(0); + Value *RHS = BI->getOperand(1); + unsigned LHSRank = getRank(LHS); + unsigned RHSRank = getRank(RHS); + + // Sort the operands by rank. + if (RHSRank < LHSRank) { + BI->setOperand(0, RHS); + BI->setOperand(1, LHS); } - // If this instruction is a commutative binary operator, process it. - if (!BI->isAssociative()) continue; - BinaryOperator *I = cast(BI); + return; + } - // 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; + // Do not reassociate operations that we do not understand. + if (!isa(BI)) + return; - // 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; + // Do not reassociate boolean (i1) expressions. We want to preserve the + // original order of evaluation for short-circuited comparisons that + // SimplifyCFG has folded to AND/OR expressions. If the expression + // is not further optimized, it is likely to be transformed back to a + // short-circuited form for code gen, and the source order may have been + // optimized for the most likely conditions. + if (BI->getType()->isIntegerTy(1)) + return; - ReassociateExpression(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); + // Reset the BBI iterator in case BreakUpSubtract changed the + // instruction it points to. + BBI = BI; + ++BBI; + 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()) return; + 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())) + return; + + // 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) + return; + + ReassociateExpression(I); } -void Reassociate::ReassociateExpression(BinaryOperator *I) { - - // First, walk the expression tree, linearizing the tree, collecting - std::vector Ops; +Value *Reassociate::ReassociateExpression(BinaryOperator *I) { + + // First, walk the expression tree, linearizing the tree, collecting the + // operand information. + SmallVector Ops; LinearizeExprTree(I, Ops); - - DOUT << "RAIn:\t"; DEBUG(PrintOps(I, Ops)); DOUT << "\n"; - + + DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\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 @@ -810,18 +1306,21 @@ void Reassociate::ReassociateExpression(BinaryOperator *I) { // 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. - DOUT << "Reassoc to scalar: " << *V << "\n"; + DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n'); I->replaceAllUsesWith(V); + if (Instruction *VI = dyn_cast(V)) + VI->setDebugLoc(I->getDebugLoc()); RemoveDeadBinaryOp(I); - return; + ++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 @@ -830,24 +1329,27 @@ void Reassociate::ReassociateExpression(BinaryOperator *I) { cast(I->use_back())->getOpcode() == Instruction::Add && isa(Ops.back().Op) && cast(Ops.back().Op)->isAllOnesValue()) { - Ops.insert(Ops.begin(), Ops.back()); - Ops.pop_back(); + ValueEntry Tmp = Ops.pop_back_val(); + Ops.insert(Ops.begin(), Tmp); } - - DOUT << "RAOut:\t"; DEBUG(PrintOps(I, Ops)); DOUT << "\n"; - + + DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n'); + if (Ops.size() == 1) { // This expression tree simplified to something that isn't a tree, // eliminate it. I->replaceAllUsesWith(Ops[0].Op); + if (Instruction *OI = dyn_cast(Ops[0].Op)) + OI->setDebugLoc(I->getDebugLoc()); RemoveDeadBinaryOp(I); - } else { - // Now that we ordered and optimized the expressions, splat them back into - // the expression tree, removing any unneeded nodes. - RewriteExprTree(I, Ops); + 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; +} bool Reassociate::runOnFunction(Function &F) { // Recalculate the rank map for F @@ -855,11 +1357,24 @@ bool Reassociate::runOnFunction(Function &F) { MadeChange = false; for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) - ReassociateBB(FI); + for (BasicBlock::iterator BBI = FI->begin(); BBI != FI->end(); ) + ReassociateInst(BBI); + + // Now that we're done, revisit any instructions which are likely to + // have secondary reassociation opportunities. + while (!RedoInsts.empty()) + if (Value *V = RedoInsts.pop_back_val()) { + BasicBlock::iterator BBI = cast(V); + ReassociateInst(BBI); + } + + // Now that we're done, delete any instructions which are no longer used. + while (!DeadInsts.empty()) + if (Value *V = DeadInsts.pop_back_val()) + RecursivelyDeleteTriviallyDeadInstructions(V); - // We are done with the rank map... + // We are done with the rank map. RankMap.clear(); ValueRankMap.clear(); return MadeChange; } -