//
// 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)
//
#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 <algorithm>
using namespace llvm;
-namespace {
- Statistic<> NumLinear ("reassociate","Number of insts linearized");
- Statistic<> NumChanged("reassociate","Number of insts reassociated");
- Statistic<> NumSwapped("reassociate","Number of insts with operands swapped");
- Statistic<> NumAnnihil("reassociate","Number of expr tree annihilated");
+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 {
struct ValueEntry {
unsigned Rank;
Value *Op;
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<ValueEntry> &Ops) {
+ Module *M = I->getParent()->getParent()->getParent();
+ 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 {
class Reassociate : public FunctionPass {
- std::map<BasicBlock*, unsigned> RankMap;
- std::map<Value*, unsigned> ValueRankMap;
+ DenseMap<BasicBlock*, unsigned> RankMap;
+ DenseMap<AssertingVH<>, 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 {
private:
void BuildRankMap(Function &F);
unsigned getRank(Value *V);
- void RewriteExprTree(BinaryOperator *I, unsigned Idx,
- std::vector<ValueEntry> &Ops);
- void OptimizeExpression(unsigned Opcode, std::vector<ValueEntry> &Ops);
- void LinearizeExprTree(BinaryOperator *I, std::vector<ValueEntry> &Ops);
+ Value *ReassociateExpression(BinaryOperator *I);
+ void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops,
+ unsigned Idx = 0);
+ Value *OptimizeExpression(BinaryOperator *I,
+ SmallVectorImpl<ValueEntry> &Ops);
+ Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
+ void LinearizeExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
void LinearizeExpr(BinaryOperator *I);
+ Value *RemoveFactorFromExpression(Value *V, Value *Factor);
void ReassociateBB(BasicBlock *BB);
+
+ void RemoveDeadBinaryOp(Value *V);
};
-
- RegisterOpt<Reassociate> X("reassociate", "Reassociate expressions");
}
+char Reassociate::ID = 0;
+static RegisterPass<Reassociate> 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<Instruction>(V);
+ if (!Op || !isa<BinaryOperator>(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::Malloc ||
I->getOpcode() == Instruction::Invoke ||
- I->getOpcode() == Instruction::Call ||
- I->getOpcode() == Instruction::Div ||
- I->getOpcode() == Instruction::Rem)
+ (I->getOpcode() == Instruction::Call &&
+ !isa<DbgInfoIntrinsic>(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;
}
// 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<Function*> RPOT(&F);
for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
// 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<Argument>(V)) return ValueRankMap[V]; // Function argument...
-
Instruction *I = dyn_cast<Instruction>(V);
- if (I == 0) return 0; // Otherwise it's a global or constant, rank 0.
+ if (I == 0) {
+ if (isa<Argument>(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
// 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()->isIntegral() ||
+ if (!I->getType()->isIntegerTy() ||
(!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I)))
++Rank;
- //DEBUG(std::cerr << "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
/// opcode and if it only has one use.
static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
- if (V->hasOneUse() && isa<Instruction>(V) &&
+ if ((V->hasOneUse() || V->use_empty()) && isa<Instruction>(V) &&
cast<Instruction>(V)->getOpcode() == Opcode)
return cast<BinaryOperator>(V);
return 0;
/// LowerNegateToMultiply - Replace 0-X with X*-1.
///
-static Instruction *LowerNegateToMultiply(Instruction *Neg) {
- Constant *Cst;
- if (Neg->getType()->isFloatingPoint())
- Cst = ConstantFP::get(Neg->getType(), -1);
- else
- Cst = ConstantInt::getAllOnesValue(Neg->getType());
-
- std::string NegName = Neg->getName(); Neg->setName("");
- Instruction *Res = BinaryOperator::createMul(Neg->getOperand(1), Cst, NegName,
- Neg);
+static Instruction *LowerNegateToMultiply(Instruction *Neg,
+ DenseMap<AssertingVH<>, unsigned> &ValueRankMap) {
+ Constant *Cst = Constant::getAllOnesValue(Neg->getType());
+
+ Instruction *Res = BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
+ ValueRankMap.erase(Neg);
+ Res->takeName(Neg);
Neg->replaceAllUsesWith(Res);
Neg->eraseFromParent();
return Res;
isReassociableOp(RHS, I->getOpcode()) &&
"Not an expression that needs linearization?");
- DEBUG(std::cerr << "Linear" << *LHS << *RHS << *I);
+ DEBUG(dbgs() << "Linear" << *LHS << '\n' << *RHS << '\n' << *I << '\n');
// Move the RHS instruction to live immediately before I, avoiding breaking
// dominator properties.
++NumLinear;
MadeChange = true;
- DEBUG(std::cerr << "Linearized: " << *I);
+ DEBUG(dbgs() << "Linearized: " << *I << '\n');
// If D is part of this expression tree, tail recurse.
if (isReassociableOp(I->getOperand(1), I->getOpcode()))
/// 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.
///
-/// This returns the rank of the RHS operand, which is known to be the highest
-/// rank value in the expression tree.
+/// 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,
- std::vector<ValueEntry> &Ops) {
+ SmallVectorImpl<ValueEntry> &Ops) {
Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
unsigned Opcode = I->getOpcode();
// 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<Instruction>(LHS));
+ LHS = LowerNegateToMultiply(cast<Instruction>(LHS), ValueRankMap);
LHSBO = isReassociableOp(LHS, Opcode);
}
if (!RHSBO && RHS->hasOneUse() && BinaryOperator::isNeg(RHS)) {
- RHS = LowerNegateToMultiply(cast<Instruction>(RHS));
+ RHS = LowerNegateToMultiply(cast<Instruction>(RHS), ValueRankMap);
RHSBO = isReassociableOp(RHS, Opcode);
}
}
// 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");
+ Success = false;
+ 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<BinaryOperator>(I->getOperand(0));
// 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, unsigned i,
- std::vector<ValueEntry> &Ops) {
+void Reassociate::RewriteExprTree(BinaryOperator *I,
+ SmallVectorImpl<ValueEntry> &Ops,
+ unsigned i) {
if (i+2 == Ops.size()) {
if (I->getOperand(0) != Ops[i].Op ||
I->getOperand(1) != Ops[i+1].Op) {
- DEBUG(std::cerr << "RA: " << *I);
+ Value *OldLHS = I->getOperand(0);
+ DEBUG(dbgs() << "RA: " << *I << '\n');
I->setOperand(0, Ops[i].Op);
I->setOperand(1, Ops[i+1].Op);
- DEBUG(std::cerr << "TO: " << *I);
+ 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);
}
return;
}
assert(i+2 < Ops.size() && "Ops index out of range!");
if (I->getOperand(1) != Ops[i].Op) {
- DEBUG(std::cerr << "RA: " << *I);
+ DEBUG(dbgs() << "RA: " << *I << '\n');
I->setOperand(1, Ops[i].Op);
- DEBUG(std::cerr << "TO: " << *I);
+ DEBUG(dbgs() << "TO: " << *I << '\n');
MadeChange = true;
++NumChanged;
}
- RewriteExprTree(cast<BinaryOperator>(I->getOperand(0)), i+1, Ops);
+
+ BinaryOperator *LHS = cast<BinaryOperator>(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);
}
// that should be processed next by the reassociation pass.
//
static Value *NegateValue(Value *V, Instruction *BI) {
+ if (Constant *C = dyn_cast<Constant>(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,
// 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<Instruction>(V))
if (I->getOpcode() == Instruction::Add && I->hasOneUse()) {
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<BinaryOperator>(*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<Instruction>(V)) {
+ if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
+ InsertPt = II->getNormalDest()->begin();
+ } else {
+ InsertPt = InstInput;
+ ++InsertPt;
+ }
+ while (isa<PHINode>(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<AssertingVH<>, 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(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) {
- if (!isReassociableOp(Shl->getOperand(0), Instruction::Mul) &&
- !(Shl->hasOneUse() && isReassociableOp(Shl->use_back(),Instruction::Mul)))
- return 0;
-
- Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
- MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
-
- std::string Name = Shl->getName(); Shl->setName("");
- Instruction *Mul = BinaryOperator::createMul(Shl->getOperand(0), MulCst,
- Name, Shl);
- Shl->replaceAllUsesWith(Mul);
- Shl->eraseFromParent();
- return Mul;
+static Instruction *ConvertShiftToMul(Instruction *Shl,
+ DenseMap<AssertingVH<>, 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<Constant>(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.
-static unsigned FindInOperandList(std::vector<ValueEntry> &Ops, unsigned i,
+// 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<ValueEntry> &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;
return i;
}
-void Reassociate::OptimizeExpression(unsigned Opcode,
- std::vector<ValueEntry> &Ops) {
+/// 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<Value*> &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<ValueEntry, 8> 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<ConstantInt>(Factor))
+ if (ConstantInt *FC2 = dyn_cast<ConstantInt>(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;
+}
+
+/// 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<Value*> &Factors) {
+ BinaryOperator *BO;
+ if ((!V->hasOneUse() && !V->use_empty()) ||
+ !(BO = dyn_cast<BinaryOperator>(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);
+}
+
+/// 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<ValueEntry> &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<ValueEntry> &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<IntegerType>(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<BinaryOperator>(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<Value*, unsigned> 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<BinaryOperator>(Ops[i].Op);
+ if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
+ continue;
+
+ // Compute all of the factors of this added value.
+ SmallVector<Value*, 8> Factors;
+ FindSingleUseMultiplyFactors(BOp, Factors);
+ assert(Factors.size() > 1 && "Bad linearize!");
+
+ // Add one to FactorOccurrences for each unique factor in this op.
+ SmallPtrSet<Value*, 8> 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<ConstantInt>(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<Value*, 4> NewMulOps;
+ for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+ // Only try to remove factors from expressions we're allowed to.
+ BinaryOperator *BOp = dyn_cast<BinaryOperator>(Ops[i].Op);
+ if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
+ continue;
+
+ 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");
+ (void)NumAddedValues;
+ V = ReassociateExpression(cast<BinaryOperator>(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<BinaryOperator>(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<ValueEntry> &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;
+ if (Ops.size() == 1) return Ops[0].Op;
+ unsigned Opcode = I->getOpcode();
+
if (Constant *V1 = dyn_cast<Constant>(Ops[Ops.size()-2].Op))
if (Constant *V2 = dyn_cast<Constant>(Ops.back().Op)) {
Ops.pop_back();
Ops.back().Op = ConstantExpr::get(Opcode, V1, V2);
- OptimizeExpression(Opcode, Ops);
- return;
+ return OptimizeExpression(I, Ops);
}
// Check for destructive annihilation due to a constant being used.
- if (ConstantIntegral *CstVal = dyn_cast<ConstantIntegral>(Ops.back().Op))
+ if (ConstantInt *CstVal = dyn_cast<ConstantInt>(Ops.back().Op))
switch (Opcode) {
default: break;
case Instruction::And:
- if (CstVal->isNullValue()) { // ... & 0 -> 0
- Ops[0].Op = CstVal;
- Ops.erase(Ops.begin()+1, Ops.end());
- ++NumAnnihil;
- return;
- } else if (CstVal->isAllOnesValue()) { // ... & -1 -> ...
+ if (CstVal->isZero()) // X & 0 -> 0
+ return CstVal;
+ if (CstVal->isAllOnesValue()) // X & -1 -> X
Ops.pop_back();
- }
break;
case Instruction::Mul:
- if (CstVal->isNullValue()) { // ... * 0 -> 0
- Ops[0].Op = CstVal;
- Ops.erase(Ops.begin()+1, Ops.end());
+ if (CstVal->isZero()) { // X * 0 -> 0
++NumAnnihil;
- return;
- } else if (cast<ConstantInt>(CstVal)->getRawValue() == 1) {
- Ops.pop_back(); // ... * 1 -> ...
+ return CstVal;
}
+
+ if (cast<ConstantInt>(CstVal)->isOne())
+ Ops.pop_back(); // X * 1 -> X
break;
case Instruction::Or:
- if (CstVal->isAllOnesValue()) { // ... | -1 -> -1
- Ops[0].Op = CstVal;
- Ops.erase(Ops.begin()+1, Ops.end());
- ++NumAnnihil;
- return;
- }
+ 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;
+ 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.
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
- Ops[0].Op = Constant::getNullValue(X->getType());
- Ops.erase(Ops.begin()+1, Ops.end());
- ++NumAnnihil;
- return;
- } else if (Opcode == Instruction::Or) { // ...|X|~X = -1
- Ops[0].Op = ConstantIntegral::getAllOnesValue(X->getType());
- Ops.erase(Ops.begin()+1, Ops.end());
- ++NumAnnihil;
- return;
- }
- }
- }
-
- // 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) {
- Ops[0].Op = Constant::getNullValue(Ops[0].Op->getType());
- Ops.erase(Ops.begin()+1, Ops.end());
- ++NumAnnihil;
- return;
- }
- // ... X^X -> ...
- Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
- i -= 1; e -= 2;
- IterateOptimization = true;
- ++NumAnnihil;
- }
- }
- }
+ 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;
+ }
- 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) {
- Ops[0].Op = Constant::getNullValue(X->getType());
- Ops.pop_back();
- ++NumAnnihil;
- return;
- } 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.
- }
- }
- }
- }
break;
//case Instruction::Mul:
}
if (IterateOptimization)
- OptimizeExpression(Opcode, Ops);
+ return OptimizeExpression(I, Ops);
+ return 0;
}
-/// PrintOps - Print out the expression identified in the Ops list.
-///
-static void PrintOps(unsigned Opcode, const std::vector<ValueEntry> &Ops,
- BasicBlock *BB) {
- Module *M = BB->getParent()->getParent();
- std::cerr << Instruction::getOpcodeName(Opcode) << " "
- << *Ops[0].Op->getType();
- for (unsigned i = 0, e = Ops.size(); i != e; ++i)
- WriteAsOperand(std::cerr << " ", Ops[i].Op, false, true, M)
- << "," << Ops[i].Rank;
-}
/// ReassociateBB - Inspect all of the instructions in this basic block,
/// reassociating them as we go.
void Reassociate::ReassociateBB(BasicBlock *BB) {
- for (BasicBlock::iterator BI = BB->begin(); BI != BB->end(); ++BI) {
+ for (BasicBlock::iterator BBI = BB->begin(); BBI != BB->end(); ) {
+ Instruction *BI = BBI++;
if (BI->getOpcode() == Instruction::Shl &&
isa<ConstantInt>(BI->getOperand(1)))
- if (Instruction *NI = ConvertShiftToMul(BI)) {
+ if (Instruction *NI = ConvertShiftToMul(BI, ValueRankMap)) {
MadeChange = true;
BI = NI;
}
// Reject cases where it is pointless to do this.
- if (!isa<BinaryOperator>(BI) || BI->getType()->isFloatingPoint())
+ if (!isa<BinaryOperator>(BI) || BI->getType()->isFloatingPointTy() ||
+ isa<VectorType>(BI->getType()))
continue; // Floating point ops are not associative.
+ // 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))
+ continue;
+
// 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 {
+ 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);
+ BI = LowerNegateToMultiply(BI, ValueRankMap);
MadeChange = true;
}
}
cast<Instruction>(I->use_back())->getOpcode() == Instruction::Sub)
continue;
- // First, walk the expression tree, linearizing the tree, collecting
- std::vector<ValueEntry> Ops;
- LinearizeExprTree(I, Ops);
-
- DEBUG(std::cerr << "RAIn:\t"; PrintOps(I->getOpcode(), Ops, BB);
- std::cerr << "\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.
- OptimizeExpression(I->getOpcode(), Ops);
-
- // 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<Instruction>(I->use_back())->getOpcode() == Instruction::Add &&
- isa<ConstantInt>(Ops.back().Op) &&
- cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
- Ops.insert(Ops.begin(), Ops.back());
- Ops.pop_back();
- }
-
- DEBUG(std::cerr << "RAOut:\t"; PrintOps(I->getOpcode(), Ops, BB);
- std::cerr << "\n");
+ ReassociateExpression(I);
+ }
+}
- if (Ops.size() == 1) {
- // This expression tree simplified to something that isn't a tree,
- // eliminate it.
- I->replaceAllUsesWith(Ops[0].Op);
- } else {
- // Now that we ordered and optimized the expressions, splat them back into
- // the expression tree, removing any unneeded nodes.
- RewriteExprTree(I, 0, Ops);
- }
+Value *Reassociate::ReassociateExpression(BinaryOperator *I) {
+
+ // First, walk the expression tree, linearizing the tree, collecting the
+ // operand information.
+ SmallVector<ValueEntry, 8> Ops;
+ LinearizeExprTree(I, Ops);
+
+ 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
+ // 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(dbgs() << "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<Instruction>(I->use_back())->getOpcode() == Instruction::Add &&
+ isa<ConstantInt>(Ops.back().Op) &&
+ cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
+ ValueEntry Tmp = Ops.pop_back_val();
+ Ops.insert(Ops.begin(), Tmp);
+ }
+
+ 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);
+ 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;
}
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
ReassociateBB(FI);
- // We are done with the rank map...
+ // We are done with the rank map.
RankMap.clear();
ValueRankMap.clear();
return MadeChange;
projects / oota-llvm.git / blobdiff