1 //===- Reassociate.cpp - Reassociate binary expressions -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass reassociates commutative expressions in an order that is designed
11 // to promote better constant propagation, GCSE, LICM, PRE, etc.
13 // For example: 4 + (x + 5) -> x + (4 + 5)
15 // In the implementation of this algorithm, constants are assigned rank = 0,
16 // function arguments are rank = 1, and other values are assigned ranks
17 // corresponding to the reverse post order traversal of current function
18 // (starting at 2), which effectively gives values in deep loops higher rank
19 // than values not in loops.
21 //===----------------------------------------------------------------------===//
23 #define DEBUG_TYPE "reassociate"
24 #include "llvm/Transforms/Scalar.h"
25 #include "llvm/Transforms/Utils/Local.h"
26 #include "llvm/Constants.h"
27 #include "llvm/DerivedTypes.h"
28 #include "llvm/Function.h"
29 #include "llvm/Instructions.h"
30 #include "llvm/IntrinsicInst.h"
31 #include "llvm/Pass.h"
32 #include "llvm/Assembly/Writer.h"
33 #include "llvm/Support/CFG.h"
34 #include "llvm/Support/IRBuilder.h"
35 #include "llvm/Support/Debug.h"
36 #include "llvm/Support/ValueHandle.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include "llvm/ADT/PostOrderIterator.h"
39 #include "llvm/ADT/STLExtras.h"
40 #include "llvm/ADT/Statistic.h"
41 #include "llvm/ADT/DenseMap.h"
45 STATISTIC(NumLinear , "Number of insts linearized");
46 STATISTIC(NumChanged, "Number of insts reassociated");
47 STATISTIC(NumAnnihil, "Number of expr tree annihilated");
48 STATISTIC(NumFactor , "Number of multiplies factored");
54 ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {}
56 inline bool operator<(const ValueEntry &LHS, const ValueEntry &RHS) {
57 return LHS.Rank > RHS.Rank; // Sort so that highest rank goes to start.
62 /// PrintOps - Print out the expression identified in the Ops list.
64 static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
65 Module *M = I->getParent()->getParent()->getParent();
66 dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
67 << *Ops[0].Op->getType() << '\t';
68 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
70 WriteAsOperand(dbgs(), Ops[i].Op, false, M);
71 dbgs() << ", #" << Ops[i].Rank << "] ";
77 /// \brief Utility class representing a base and exponent pair which form one
78 /// factor of some product.
83 Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {}
85 /// \brief Sort factors by their Base.
87 bool operator()(const Factor &LHS, const Factor &RHS) {
88 return LHS.Base < RHS.Base;
92 /// \brief Compare factors for equal bases.
94 bool operator()(const Factor &LHS, const Factor &RHS) {
95 return LHS.Base == RHS.Base;
99 /// \brief Sort factors in descending order by their power.
100 struct PowerDescendingSorter {
101 bool operator()(const Factor &LHS, const Factor &RHS) {
102 return LHS.Power > RHS.Power;
106 /// \brief Compare factors for equal powers.
108 bool operator()(const Factor &LHS, const Factor &RHS) {
109 return LHS.Power == RHS.Power;
116 class Reassociate : public FunctionPass {
117 DenseMap<BasicBlock*, unsigned> RankMap;
118 DenseMap<AssertingVH<Value>, unsigned> ValueRankMap;
119 SmallVector<WeakVH, 8> RedoInsts;
120 SmallVector<WeakVH, 8> DeadInsts;
123 static char ID; // Pass identification, replacement for typeid
124 Reassociate() : FunctionPass(ID) {
125 initializeReassociatePass(*PassRegistry::getPassRegistry());
128 bool runOnFunction(Function &F);
130 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
131 AU.setPreservesCFG();
134 void BuildRankMap(Function &F);
135 unsigned getRank(Value *V);
136 Value *ReassociateExpression(BinaryOperator *I);
137 void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops,
139 Value *OptimizeExpression(BinaryOperator *I,
140 SmallVectorImpl<ValueEntry> &Ops);
141 Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
142 bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
143 SmallVectorImpl<Factor> &Factors);
144 Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
145 SmallVectorImpl<Factor> &Factors);
146 Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
147 void LinearizeExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
148 void LinearizeExpr(BinaryOperator *I);
149 Value *RemoveFactorFromExpression(Value *V, Value *Factor);
150 void ReassociateInst(BasicBlock::iterator &BBI);
152 void RemoveDeadBinaryOp(Value *V);
156 char Reassociate::ID = 0;
157 INITIALIZE_PASS(Reassociate, "reassociate",
158 "Reassociate expressions", false, false)
160 // Public interface to the Reassociate pass
161 FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
163 void Reassociate::RemoveDeadBinaryOp(Value *V) {
164 Instruction *Op = dyn_cast<Instruction>(V);
165 if (!Op || !isa<BinaryOperator>(Op))
168 Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1);
170 ValueRankMap.erase(Op);
171 DeadInsts.push_back(Op);
172 RemoveDeadBinaryOp(LHS);
173 RemoveDeadBinaryOp(RHS);
177 static bool isUnmovableInstruction(Instruction *I) {
178 if (I->getOpcode() == Instruction::PHI ||
179 I->getOpcode() == Instruction::Alloca ||
180 I->getOpcode() == Instruction::Load ||
181 I->getOpcode() == Instruction::Invoke ||
182 (I->getOpcode() == Instruction::Call &&
183 !isa<DbgInfoIntrinsic>(I)) ||
184 I->getOpcode() == Instruction::UDiv ||
185 I->getOpcode() == Instruction::SDiv ||
186 I->getOpcode() == Instruction::FDiv ||
187 I->getOpcode() == Instruction::URem ||
188 I->getOpcode() == Instruction::SRem ||
189 I->getOpcode() == Instruction::FRem)
194 void Reassociate::BuildRankMap(Function &F) {
197 // Assign distinct ranks to function arguments
198 for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
199 ValueRankMap[&*I] = ++i;
201 ReversePostOrderTraversal<Function*> RPOT(&F);
202 for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
203 E = RPOT.end(); I != E; ++I) {
205 unsigned BBRank = RankMap[BB] = ++i << 16;
207 // Walk the basic block, adding precomputed ranks for any instructions that
208 // we cannot move. This ensures that the ranks for these instructions are
209 // all different in the block.
210 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
211 if (isUnmovableInstruction(I))
212 ValueRankMap[&*I] = ++BBRank;
216 unsigned Reassociate::getRank(Value *V) {
217 Instruction *I = dyn_cast<Instruction>(V);
219 if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
220 return 0; // Otherwise it's a global or constant, rank 0.
223 if (unsigned Rank = ValueRankMap[I])
224 return Rank; // Rank already known?
226 // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
227 // we can reassociate expressions for code motion! Since we do not recurse
228 // for PHI nodes, we cannot have infinite recursion here, because there
229 // cannot be loops in the value graph that do not go through PHI nodes.
230 unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
231 for (unsigned i = 0, e = I->getNumOperands();
232 i != e && Rank != MaxRank; ++i)
233 Rank = std::max(Rank, getRank(I->getOperand(i)));
235 // If this is a not or neg instruction, do not count it for rank. This
236 // assures us that X and ~X will have the same rank.
237 if (!I->getType()->isIntegerTy() ||
238 (!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I)))
241 //DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = "
244 return ValueRankMap[I] = Rank;
247 /// isReassociableOp - Return true if V is an instruction of the specified
248 /// opcode and if it only has one use.
249 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
250 if ((V->hasOneUse() || V->use_empty()) && isa<Instruction>(V) &&
251 cast<Instruction>(V)->getOpcode() == Opcode)
252 return cast<BinaryOperator>(V);
256 /// LowerNegateToMultiply - Replace 0-X with X*-1.
258 static Instruction *LowerNegateToMultiply(Instruction *Neg,
259 DenseMap<AssertingVH<Value>, unsigned> &ValueRankMap) {
260 Constant *Cst = Constant::getAllOnesValue(Neg->getType());
262 Instruction *Res = BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
263 ValueRankMap.erase(Neg);
265 Neg->replaceAllUsesWith(Res);
266 Res->setDebugLoc(Neg->getDebugLoc());
267 Neg->eraseFromParent();
271 // Given an expression of the form '(A+B)+(D+C)', turn it into '(((A+B)+C)+D)'.
272 // Note that if D is also part of the expression tree that we recurse to
273 // linearize it as well. Besides that case, this does not recurse into A,B, or
275 void Reassociate::LinearizeExpr(BinaryOperator *I) {
276 BinaryOperator *LHS = cast<BinaryOperator>(I->getOperand(0));
277 BinaryOperator *RHS = cast<BinaryOperator>(I->getOperand(1));
278 assert(isReassociableOp(LHS, I->getOpcode()) &&
279 isReassociableOp(RHS, I->getOpcode()) &&
280 "Not an expression that needs linearization?");
282 DEBUG(dbgs() << "Linear" << *LHS << '\n' << *RHS << '\n' << *I << '\n');
284 // Move the RHS instruction to live immediately before I, avoiding breaking
285 // dominator properties.
288 // Move operands around to do the linearization.
289 I->setOperand(1, RHS->getOperand(0));
290 RHS->setOperand(0, LHS);
291 I->setOperand(0, RHS);
293 // Conservatively clear all the optional flags, which may not hold
294 // after the reassociation.
295 I->clearSubclassOptionalData();
296 LHS->clearSubclassOptionalData();
297 RHS->clearSubclassOptionalData();
301 DEBUG(dbgs() << "Linearized: " << *I << '\n');
303 // If D is part of this expression tree, tail recurse.
304 if (isReassociableOp(I->getOperand(1), I->getOpcode()))
309 /// LinearizeExprTree - Given an associative binary expression tree, traverse
310 /// all of the uses putting it into canonical form. This forces a left-linear
311 /// form of the expression (((a+b)+c)+d), and collects information about the
312 /// rank of the non-tree operands.
314 /// NOTE: These intentionally destroys the expression tree operands (turning
315 /// them into undef values) to reduce #uses of the values. This means that the
316 /// caller MUST use something like RewriteExprTree to put the values back in.
318 void Reassociate::LinearizeExprTree(BinaryOperator *I,
319 SmallVectorImpl<ValueEntry> &Ops) {
320 Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
321 unsigned Opcode = I->getOpcode();
323 // First step, linearize the expression if it is in ((A+B)+(C+D)) form.
324 BinaryOperator *LHSBO = isReassociableOp(LHS, Opcode);
325 BinaryOperator *RHSBO = isReassociableOp(RHS, Opcode);
327 // If this is a multiply expression tree and it contains internal negations,
328 // transform them into multiplies by -1 so they can be reassociated.
329 if (I->getOpcode() == Instruction::Mul) {
330 if (!LHSBO && LHS->hasOneUse() && BinaryOperator::isNeg(LHS)) {
331 LHS = LowerNegateToMultiply(cast<Instruction>(LHS), ValueRankMap);
332 LHSBO = isReassociableOp(LHS, Opcode);
334 if (!RHSBO && RHS->hasOneUse() && BinaryOperator::isNeg(RHS)) {
335 RHS = LowerNegateToMultiply(cast<Instruction>(RHS), ValueRankMap);
336 RHSBO = isReassociableOp(RHS, Opcode);
342 // Neither the LHS or RHS as part of the tree, thus this is a leaf. As
343 // such, just remember these operands and their rank.
344 Ops.push_back(ValueEntry(getRank(LHS), LHS));
345 Ops.push_back(ValueEntry(getRank(RHS), RHS));
347 // Clear the leaves out.
348 I->setOperand(0, UndefValue::get(I->getType()));
349 I->setOperand(1, UndefValue::get(I->getType()));
353 // Turn X+(Y+Z) -> (Y+Z)+X
354 std::swap(LHSBO, RHSBO);
356 bool Success = !I->swapOperands();
357 assert(Success && "swapOperands failed");
361 // Turn (A+B)+(C+D) -> (((A+B)+C)+D). This guarantees the RHS is not
362 // part of the expression tree.
364 LHS = LHSBO = cast<BinaryOperator>(I->getOperand(0));
365 RHS = I->getOperand(1);
369 // Okay, now we know that the LHS is a nested expression and that the RHS is
370 // not. Perform reassociation.
371 assert(!isReassociableOp(RHS, Opcode) && "LinearizeExpr failed!");
373 // Move LHS right before I to make sure that the tree expression dominates all
375 LHSBO->moveBefore(I);
377 // Linearize the expression tree on the LHS.
378 LinearizeExprTree(LHSBO, Ops);
380 // Remember the RHS operand and its rank.
381 Ops.push_back(ValueEntry(getRank(RHS), RHS));
383 // Clear the RHS leaf out.
384 I->setOperand(1, UndefValue::get(I->getType()));
387 // RewriteExprTree - Now that the operands for this expression tree are
388 // linearized and optimized, emit them in-order. This function is written to be
390 void Reassociate::RewriteExprTree(BinaryOperator *I,
391 SmallVectorImpl<ValueEntry> &Ops,
393 if (i+2 == Ops.size()) {
394 if (I->getOperand(0) != Ops[i].Op ||
395 I->getOperand(1) != Ops[i+1].Op) {
396 Value *OldLHS = I->getOperand(0);
397 DEBUG(dbgs() << "RA: " << *I << '\n');
398 I->setOperand(0, Ops[i].Op);
399 I->setOperand(1, Ops[i+1].Op);
401 // Clear all the optional flags, which may not hold after the
402 // reassociation if the expression involved more than just this operation.
404 I->clearSubclassOptionalData();
406 DEBUG(dbgs() << "TO: " << *I << '\n');
410 // If we reassociated a tree to fewer operands (e.g. (1+a+2) -> (a+3)
411 // delete the extra, now dead, nodes.
412 RemoveDeadBinaryOp(OldLHS);
416 assert(i+2 < Ops.size() && "Ops index out of range!");
418 if (I->getOperand(1) != Ops[i].Op) {
419 DEBUG(dbgs() << "RA: " << *I << '\n');
420 I->setOperand(1, Ops[i].Op);
422 // Conservatively clear all the optional flags, which may not hold
423 // after the reassociation.
424 I->clearSubclassOptionalData();
426 DEBUG(dbgs() << "TO: " << *I << '\n');
431 BinaryOperator *LHS = cast<BinaryOperator>(I->getOperand(0));
432 assert(LHS->getOpcode() == I->getOpcode() &&
433 "Improper expression tree!");
435 // Compactify the tree instructions together with each other to guarantee
436 // that the expression tree is dominated by all of Ops.
438 RewriteExprTree(LHS, Ops, i+1);
443 // NegateValue - Insert instructions before the instruction pointed to by BI,
444 // that computes the negative version of the value specified. The negative
445 // version of the value is returned, and BI is left pointing at the instruction
446 // that should be processed next by the reassociation pass.
448 static Value *NegateValue(Value *V, Instruction *BI) {
449 if (Constant *C = dyn_cast<Constant>(V))
450 return ConstantExpr::getNeg(C);
452 // We are trying to expose opportunity for reassociation. One of the things
453 // that we want to do to achieve this is to push a negation as deep into an
454 // expression chain as possible, to expose the add instructions. In practice,
455 // this means that we turn this:
456 // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
457 // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
458 // the constants. We assume that instcombine will clean up the mess later if
459 // we introduce tons of unnecessary negation instructions.
461 if (Instruction *I = dyn_cast<Instruction>(V))
462 if (I->getOpcode() == Instruction::Add && I->hasOneUse()) {
463 // Push the negates through the add.
464 I->setOperand(0, NegateValue(I->getOperand(0), BI));
465 I->setOperand(1, NegateValue(I->getOperand(1), BI));
467 // We must move the add instruction here, because the neg instructions do
468 // not dominate the old add instruction in general. By moving it, we are
469 // assured that the neg instructions we just inserted dominate the
470 // instruction we are about to insert after them.
473 I->setName(I->getName()+".neg");
477 // Okay, we need to materialize a negated version of V with an instruction.
478 // Scan the use lists of V to see if we have one already.
479 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
481 if (!BinaryOperator::isNeg(U)) continue;
483 // We found one! Now we have to make sure that the definition dominates
484 // this use. We do this by moving it to the entry block (if it is a
485 // non-instruction value) or right after the definition. These negates will
486 // be zapped by reassociate later, so we don't need much finesse here.
487 BinaryOperator *TheNeg = cast<BinaryOperator>(U);
489 // Verify that the negate is in this function, V might be a constant expr.
490 if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
493 BasicBlock::iterator InsertPt;
494 if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
495 if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
496 InsertPt = II->getNormalDest()->begin();
498 InsertPt = InstInput;
501 while (isa<PHINode>(InsertPt)) ++InsertPt;
503 InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
505 TheNeg->moveBefore(InsertPt);
509 // Insert a 'neg' instruction that subtracts the value from zero to get the
511 return BinaryOperator::CreateNeg(V, V->getName() + ".neg", BI);
514 /// ShouldBreakUpSubtract - Return true if we should break up this subtract of
515 /// X-Y into (X + -Y).
516 static bool ShouldBreakUpSubtract(Instruction *Sub) {
517 // If this is a negation, we can't split it up!
518 if (BinaryOperator::isNeg(Sub))
521 // Don't bother to break this up unless either the LHS is an associable add or
522 // subtract or if this is only used by one.
523 if (isReassociableOp(Sub->getOperand(0), Instruction::Add) ||
524 isReassociableOp(Sub->getOperand(0), Instruction::Sub))
526 if (isReassociableOp(Sub->getOperand(1), Instruction::Add) ||
527 isReassociableOp(Sub->getOperand(1), Instruction::Sub))
529 if (Sub->hasOneUse() &&
530 (isReassociableOp(Sub->use_back(), Instruction::Add) ||
531 isReassociableOp(Sub->use_back(), Instruction::Sub)))
537 /// BreakUpSubtract - If we have (X-Y), and if either X is an add, or if this is
538 /// only used by an add, transform this into (X+(0-Y)) to promote better
540 static Instruction *BreakUpSubtract(Instruction *Sub,
541 DenseMap<AssertingVH<Value>, unsigned> &ValueRankMap) {
542 // Convert a subtract into an add and a neg instruction. This allows sub
543 // instructions to be commuted with other add instructions.
545 // Calculate the negative value of Operand 1 of the sub instruction,
546 // and set it as the RHS of the add instruction we just made.
548 Value *NegVal = NegateValue(Sub->getOperand(1), Sub);
550 BinaryOperator::CreateAdd(Sub->getOperand(0), NegVal, "", Sub);
553 // Everyone now refers to the add instruction.
554 ValueRankMap.erase(Sub);
555 Sub->replaceAllUsesWith(New);
556 New->setDebugLoc(Sub->getDebugLoc());
557 Sub->eraseFromParent();
559 DEBUG(dbgs() << "Negated: " << *New << '\n');
563 /// ConvertShiftToMul - If this is a shift of a reassociable multiply or is used
564 /// by one, change this into a multiply by a constant to assist with further
566 static Instruction *ConvertShiftToMul(Instruction *Shl,
567 DenseMap<AssertingVH<Value>, unsigned> &ValueRankMap) {
568 // If an operand of this shift is a reassociable multiply, or if the shift
569 // is used by a reassociable multiply or add, turn into a multiply.
570 if (isReassociableOp(Shl->getOperand(0), Instruction::Mul) ||
572 (isReassociableOp(Shl->use_back(), Instruction::Mul) ||
573 isReassociableOp(Shl->use_back(), Instruction::Add)))) {
574 Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
575 MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
578 BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
579 ValueRankMap.erase(Shl);
581 Shl->replaceAllUsesWith(Mul);
582 Mul->setDebugLoc(Shl->getDebugLoc());
583 Shl->eraseFromParent();
589 // Scan backwards and forwards among values with the same rank as element i to
590 // see if X exists. If X does not exist, return i. This is useful when
591 // scanning for 'x' when we see '-x' because they both get the same rank.
592 static unsigned FindInOperandList(SmallVectorImpl<ValueEntry> &Ops, unsigned i,
594 unsigned XRank = Ops[i].Rank;
595 unsigned e = Ops.size();
596 for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j)
600 for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j)
606 /// EmitAddTreeOfValues - Emit a tree of add instructions, summing Ops together
607 /// and returning the result. Insert the tree before I.
608 static Value *EmitAddTreeOfValues(Instruction *I, SmallVectorImpl<Value*> &Ops){
609 if (Ops.size() == 1) return Ops.back();
611 Value *V1 = Ops.back();
613 Value *V2 = EmitAddTreeOfValues(I, Ops);
614 return BinaryOperator::CreateAdd(V2, V1, "tmp", I);
617 /// RemoveFactorFromExpression - If V is an expression tree that is a
618 /// multiplication sequence, and if this sequence contains a multiply by Factor,
619 /// remove Factor from the tree and return the new tree.
620 Value *Reassociate::RemoveFactorFromExpression(Value *V, Value *Factor) {
621 BinaryOperator *BO = isReassociableOp(V, Instruction::Mul);
624 SmallVector<ValueEntry, 8> Factors;
625 LinearizeExprTree(BO, Factors);
627 bool FoundFactor = false;
628 bool NeedsNegate = false;
629 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
630 if (Factors[i].Op == Factor) {
632 Factors.erase(Factors.begin()+i);
636 // If this is a negative version of this factor, remove it.
637 if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor))
638 if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
639 if (FC1->getValue() == -FC2->getValue()) {
640 FoundFactor = NeedsNegate = true;
641 Factors.erase(Factors.begin()+i);
647 // Make sure to restore the operands to the expression tree.
648 RewriteExprTree(BO, Factors);
652 BasicBlock::iterator InsertPt = BO; ++InsertPt;
654 // If this was just a single multiply, remove the multiply and return the only
655 // remaining operand.
656 if (Factors.size() == 1) {
657 ValueRankMap.erase(BO);
658 DeadInsts.push_back(BO);
661 RewriteExprTree(BO, Factors);
666 V = BinaryOperator::CreateNeg(V, "neg", InsertPt);
671 /// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively
672 /// add its operands as factors, otherwise add V to the list of factors.
674 /// Ops is the top-level list of add operands we're trying to factor.
675 static void FindSingleUseMultiplyFactors(Value *V,
676 SmallVectorImpl<Value*> &Factors,
677 const SmallVectorImpl<ValueEntry> &Ops,
680 if (!(V->hasOneUse() || V->use_empty()) || // More than one use.
681 !(BO = dyn_cast<BinaryOperator>(V)) ||
682 BO->getOpcode() != Instruction::Mul) {
683 Factors.push_back(V);
687 // If this value has a single use because it is another input to the add
688 // tree we're reassociating and we dropped its use, it actually has two
689 // uses and we can't factor it.
691 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
692 if (Ops[i].Op == V) {
693 Factors.push_back(V);
699 // Otherwise, add the LHS and RHS to the list of factors.
700 FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops, false);
701 FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops, false);
704 /// OptimizeAndOrXor - Optimize a series of operands to an 'and', 'or', or 'xor'
705 /// instruction. This optimizes based on identities. If it can be reduced to
706 /// a single Value, it is returned, otherwise the Ops list is mutated as
708 static Value *OptimizeAndOrXor(unsigned Opcode,
709 SmallVectorImpl<ValueEntry> &Ops) {
710 // Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
711 // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
712 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
713 // First, check for X and ~X in the operand list.
714 assert(i < Ops.size());
715 if (BinaryOperator::isNot(Ops[i].Op)) { // Cannot occur for ^.
716 Value *X = BinaryOperator::getNotArgument(Ops[i].Op);
717 unsigned FoundX = FindInOperandList(Ops, i, X);
719 if (Opcode == Instruction::And) // ...&X&~X = 0
720 return Constant::getNullValue(X->getType());
722 if (Opcode == Instruction::Or) // ...|X|~X = -1
723 return Constant::getAllOnesValue(X->getType());
727 // Next, check for duplicate pairs of values, which we assume are next to
728 // each other, due to our sorting criteria.
729 assert(i < Ops.size());
730 if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
731 if (Opcode == Instruction::And || Opcode == Instruction::Or) {
732 // Drop duplicate values for And and Or.
733 Ops.erase(Ops.begin()+i);
739 // Drop pairs of values for Xor.
740 assert(Opcode == Instruction::Xor);
742 return Constant::getNullValue(Ops[0].Op->getType());
745 Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
753 /// OptimizeAdd - Optimize a series of operands to an 'add' instruction. This
754 /// optimizes based on identities. If it can be reduced to a single Value, it
755 /// is returned, otherwise the Ops list is mutated as necessary.
756 Value *Reassociate::OptimizeAdd(Instruction *I,
757 SmallVectorImpl<ValueEntry> &Ops) {
758 // Scan the operand lists looking for X and -X pairs. If we find any, we
759 // can simplify the expression. X+-X == 0. While we're at it, scan for any
760 // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
762 // TODO: We could handle "X + ~X" -> "-1" if we wanted, since "-X = ~X+1".
764 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
765 Value *TheOp = Ops[i].Op;
766 // Check to see if we've seen this operand before. If so, we factor all
767 // instances of the operand together. Due to our sorting criteria, we know
768 // that these need to be next to each other in the vector.
769 if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
770 // Rescan the list, remove all instances of this operand from the expr.
771 unsigned NumFound = 0;
773 Ops.erase(Ops.begin()+i);
775 } while (i != Ops.size() && Ops[i].Op == TheOp);
777 DEBUG(errs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n');
780 // Insert a new multiply.
781 Value *Mul = ConstantInt::get(cast<IntegerType>(I->getType()), NumFound);
782 Mul = BinaryOperator::CreateMul(TheOp, Mul, "factor", I);
784 // Now that we have inserted a multiply, optimize it. This allows us to
785 // handle cases that require multiple factoring steps, such as this:
786 // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
787 RedoInsts.push_back(Mul);
789 // If every add operand was a duplicate, return the multiply.
793 // Otherwise, we had some input that didn't have the dupe, such as
794 // "A + A + B" -> "A*2 + B". Add the new multiply to the list of
795 // things being added by this operation.
796 Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
803 // Check for X and -X in the operand list.
804 if (!BinaryOperator::isNeg(TheOp))
807 Value *X = BinaryOperator::getNegArgument(TheOp);
808 unsigned FoundX = FindInOperandList(Ops, i, X);
812 // Remove X and -X from the operand list.
814 return Constant::getNullValue(X->getType());
816 Ops.erase(Ops.begin()+i);
820 --i; // Need to back up an extra one.
821 Ops.erase(Ops.begin()+FoundX);
823 --i; // Revisit element.
824 e -= 2; // Removed two elements.
827 // Scan the operand list, checking to see if there are any common factors
828 // between operands. Consider something like A*A+A*B*C+D. We would like to
829 // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
830 // To efficiently find this, we count the number of times a factor occurs
831 // for any ADD operands that are MULs.
832 DenseMap<Value*, unsigned> FactorOccurrences;
834 // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
835 // where they are actually the same multiply.
837 Value *MaxOccVal = 0;
838 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
839 BinaryOperator *BOp = dyn_cast<BinaryOperator>(Ops[i].Op);
840 if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
843 // Compute all of the factors of this added value.
844 SmallVector<Value*, 8> Factors;
845 FindSingleUseMultiplyFactors(BOp, Factors, Ops, true);
846 assert(Factors.size() > 1 && "Bad linearize!");
848 // Add one to FactorOccurrences for each unique factor in this op.
849 SmallPtrSet<Value*, 8> Duplicates;
850 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
851 Value *Factor = Factors[i];
852 if (!Duplicates.insert(Factor)) continue;
854 unsigned Occ = ++FactorOccurrences[Factor];
855 if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factor; }
857 // If Factor is a negative constant, add the negated value as a factor
858 // because we can percolate the negate out. Watch for minint, which
859 // cannot be positivified.
860 if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor))
861 if (CI->isNegative() && !CI->isMinValue(true)) {
862 Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
863 assert(!Duplicates.count(Factor) &&
864 "Shouldn't have two constant factors, missed a canonicalize");
866 unsigned Occ = ++FactorOccurrences[Factor];
867 if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factor; }
872 // If any factor occurred more than one time, we can pull it out.
874 DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
877 // Create a new instruction that uses the MaxOccVal twice. If we don't do
878 // this, we could otherwise run into situations where removing a factor
879 // from an expression will drop a use of maxocc, and this can cause
880 // RemoveFactorFromExpression on successive values to behave differently.
881 Instruction *DummyInst = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal);
882 SmallVector<Value*, 4> NewMulOps;
883 for (unsigned i = 0; i != Ops.size(); ++i) {
884 // Only try to remove factors from expressions we're allowed to.
885 BinaryOperator *BOp = dyn_cast<BinaryOperator>(Ops[i].Op);
886 if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
889 if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
890 // The factorized operand may occur several times. Convert them all in
892 for (unsigned j = Ops.size(); j != i;) {
894 if (Ops[j].Op == Ops[i].Op) {
895 NewMulOps.push_back(V);
896 Ops.erase(Ops.begin()+j);
903 // No need for extra uses anymore.
906 unsigned NumAddedValues = NewMulOps.size();
907 Value *V = EmitAddTreeOfValues(I, NewMulOps);
909 // Now that we have inserted the add tree, optimize it. This allows us to
910 // handle cases that require multiple factoring steps, such as this:
911 // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
912 assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
913 (void)NumAddedValues;
914 V = ReassociateExpression(cast<BinaryOperator>(V));
916 // Create the multiply.
917 Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
919 // Rerun associate on the multiply in case the inner expression turned into
920 // a multiply. We want to make sure that we keep things in canonical form.
921 V2 = ReassociateExpression(cast<BinaryOperator>(V2));
923 // If every add operand included the factor (e.g. "A*B + A*C"), then the
924 // entire result expression is just the multiply "A*(B+C)".
928 // Otherwise, we had some input that didn't have the factor, such as
929 // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
930 // things being added by this operation.
931 Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
938 /// \brief Predicate tests whether a ValueEntry's op is in a map.
939 struct IsValueInMap {
940 const DenseMap<Value *, unsigned> ⤅
942 IsValueInMap(const DenseMap<Value *, unsigned> &Map) : Map(Map) {}
944 bool operator()(const ValueEntry &Entry) {
945 return Map.find(Entry.Op) != Map.end();
950 /// \brief Build up a vector of value/power pairs factoring a product.
952 /// Given a series of multiplication operands, build a vector of factors and
953 /// the powers each is raised to when forming the final product. Sort them in
954 /// the order of descending power.
956 /// (x*x) -> [(x, 2)]
957 /// ((x*x)*x) -> [(x, 3)]
958 /// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
960 /// \returns Whether any factors have a power greater than one.
961 bool Reassociate::collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
962 SmallVectorImpl<Factor> &Factors) {
963 unsigned FactorPowerSum = 0;
964 DenseMap<Value *, unsigned> FactorCounts;
965 for (unsigned LastIdx = 0, Idx = 0, Size = Ops.size(); Idx < Size; ++Idx) {
966 // Note that 'use_empty' uses means the only use is in the linearized tree
967 // represented by Ops -- we remove the values from the actual operations to
968 // reduce their use count.
969 if (!Ops[Idx].Op->use_empty()) {
974 if (LastIdx == Idx || Ops[LastIdx].Op != Ops[Idx].Op) {
978 // Track for simplification all factors which occur 2 or more times.
979 DenseMap<Value *, unsigned>::iterator CountIt;
981 llvm::tie(CountIt, Inserted)
982 = FactorCounts.insert(std::make_pair(Ops[Idx].Op, 2));
985 Factors.push_back(Factor(Ops[Idx].Op, 2));
991 // We can only simplify factors if the sum of the powers of our simplifiable
992 // factors is 4 or higher. When that is the case, we will *always* have
993 // a simplification. This is an important invariant to prevent cyclicly
994 // trying to simplify already minimal formations.
995 if (FactorPowerSum < 4)
998 // Remove all the operands which are in the map.
999 Ops.erase(std::remove_if(Ops.begin(), Ops.end(), IsValueInMap(FactorCounts)),
1002 // Record the adjusted power for the simplification factors. We add back into
1003 // the Ops list any values with an odd power, and make the power even. This
1004 // allows the outer-most multiplication tree to remain in tact during
1006 unsigned OldOpsSize = Ops.size();
1007 for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
1008 Factors[Idx].Power = FactorCounts[Factors[Idx].Base];
1009 if (Factors[Idx].Power & 1) {
1010 Ops.push_back(ValueEntry(getRank(Factors[Idx].Base), Factors[Idx].Base));
1011 --Factors[Idx].Power;
1015 // None of the adjustments above should have reduced the sum of factor powers
1016 // below our mininum of '4'.
1017 assert(FactorPowerSum >= 4);
1019 // Patch up the sort of the ops vector by sorting the factors we added back
1020 // onto the back, and merging the two sequences.
1021 if (OldOpsSize != Ops.size()) {
1022 SmallVectorImpl<ValueEntry>::iterator MiddleIt = Ops.begin() + OldOpsSize;
1023 std::sort(MiddleIt, Ops.end());
1024 std::inplace_merge(Ops.begin(), MiddleIt, Ops.end());
1027 std::sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter());
1031 /// \brief Build a tree of multiplies, computing the product of Ops.
1032 static Value *buildMultiplyTree(IRBuilder<> &Builder,
1033 SmallVectorImpl<Value*> &Ops) {
1034 if (Ops.size() == 1)
1037 Value *LHS = Ops.pop_back_val();
1039 LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
1040 } while (!Ops.empty());
1045 /// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
1047 /// Given a vector of values raised to various powers, where no two values are
1048 /// equal and the powers are sorted in decreasing order, compute the minimal
1049 /// DAG of multiplies to compute the final product, and return that product
1051 Value *Reassociate::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
1052 SmallVectorImpl<Factor> &Factors) {
1053 assert(Factors[0].Power);
1054 SmallVector<Value *, 4> OuterProduct;
1055 for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
1056 Idx < Size && Factors[Idx].Power > 0; ++Idx) {
1057 if (Factors[Idx].Power != Factors[LastIdx].Power) {
1062 // We want to multiply across all the factors with the same power so that
1063 // we can raise them to that power as a single entity. Build a mini tree
1065 SmallVector<Value *, 4> InnerProduct;
1066 InnerProduct.push_back(Factors[LastIdx].Base);
1068 InnerProduct.push_back(Factors[Idx].Base);
1070 } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
1072 // Reset the base value of the first factor to the new expression tree.
1073 // We'll remove all the factors with the same power in a second pass.
1074 Factors[LastIdx].Base
1075 = ReassociateExpression(
1076 cast<BinaryOperator>(buildMultiplyTree(Builder, InnerProduct)));
1080 // Unique factors with equal powers -- we've folded them into the first one's
1082 Factors.erase(std::unique(Factors.begin(), Factors.end(),
1083 Factor::PowerEqual()),
1086 // Iteratively collect the base of each factor with an add power into the
1087 // outer product, and halve each power in preparation for squaring the
1089 for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
1090 if (Factors[Idx].Power & 1)
1091 OuterProduct.push_back(Factors[Idx].Base);
1092 Factors[Idx].Power >>= 1;
1094 if (Factors[0].Power) {
1095 Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
1096 OuterProduct.push_back(SquareRoot);
1097 OuterProduct.push_back(SquareRoot);
1099 if (OuterProduct.size() == 1)
1100 return OuterProduct.front();
1102 return ReassociateExpression(
1103 cast<BinaryOperator>(buildMultiplyTree(Builder, OuterProduct)));
1106 Value *Reassociate::OptimizeMul(BinaryOperator *I,
1107 SmallVectorImpl<ValueEntry> &Ops) {
1108 // We can only optimize the multiplies when there is a chain of more than
1109 // three, such that a balanced tree might require fewer total multiplies.
1113 // Try to turn linear trees of multiplies without other uses of the
1114 // intermediate stages into minimal multiply DAGs with perfect sub-expression
1116 SmallVector<Factor, 4> Factors;
1117 if (!collectMultiplyFactors(Ops, Factors))
1118 return 0; // All distinct factors, so nothing left for us to do.
1120 IRBuilder<> Builder(I);
1121 Value *V = buildMinimalMultiplyDAG(Builder, Factors);
1125 ValueEntry NewEntry = ValueEntry(getRank(V), V);
1126 Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry);
1130 Value *Reassociate::OptimizeExpression(BinaryOperator *I,
1131 SmallVectorImpl<ValueEntry> &Ops) {
1132 // Now that we have the linearized expression tree, try to optimize it.
1133 // Start by folding any constants that we found.
1134 bool IterateOptimization = false;
1135 if (Ops.size() == 1) return Ops[0].Op;
1137 unsigned Opcode = I->getOpcode();
1139 if (Constant *V1 = dyn_cast<Constant>(Ops[Ops.size()-2].Op))
1140 if (Constant *V2 = dyn_cast<Constant>(Ops.back().Op)) {
1142 Ops.back().Op = ConstantExpr::get(Opcode, V1, V2);
1143 return OptimizeExpression(I, Ops);
1146 // Check for destructive annihilation due to a constant being used.
1147 if (ConstantInt *CstVal = dyn_cast<ConstantInt>(Ops.back().Op))
1150 case Instruction::And:
1151 if (CstVal->isZero()) // X & 0 -> 0
1153 if (CstVal->isAllOnesValue()) // X & -1 -> X
1156 case Instruction::Mul:
1157 if (CstVal->isZero()) { // X * 0 -> 0
1162 if (cast<ConstantInt>(CstVal)->isOne())
1163 Ops.pop_back(); // X * 1 -> X
1165 case Instruction::Or:
1166 if (CstVal->isAllOnesValue()) // X | -1 -> -1
1169 case Instruction::Add:
1170 case Instruction::Xor:
1171 if (CstVal->isZero()) // X [|^+] 0 -> X
1175 if (Ops.size() == 1) return Ops[0].Op;
1177 // Handle destructive annihilation due to identities between elements in the
1178 // argument list here.
1179 unsigned NumOps = Ops.size();
1182 case Instruction::And:
1183 case Instruction::Or:
1184 case Instruction::Xor:
1185 if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
1189 case Instruction::Add:
1190 if (Value *Result = OptimizeAdd(I, Ops))
1194 case Instruction::Mul:
1195 if (Value *Result = OptimizeMul(I, Ops))
1200 if (IterateOptimization || Ops.size() != NumOps)
1201 return OptimizeExpression(I, Ops);
1206 /// ReassociateInst - Inspect and reassociate the instruction at the
1207 /// given position, post-incrementing the position.
1208 void Reassociate::ReassociateInst(BasicBlock::iterator &BBI) {
1209 Instruction *BI = BBI++;
1210 if (BI->getOpcode() == Instruction::Shl &&
1211 isa<ConstantInt>(BI->getOperand(1)))
1212 if (Instruction *NI = ConvertShiftToMul(BI, ValueRankMap)) {
1217 // Reject cases where it is pointless to do this.
1218 if (!isa<BinaryOperator>(BI) || BI->getType()->isFloatingPointTy() ||
1219 BI->getType()->isVectorTy())
1220 return; // Floating point ops are not associative.
1222 // Do not reassociate boolean (i1) expressions. We want to preserve the
1223 // original order of evaluation for short-circuited comparisons that
1224 // SimplifyCFG has folded to AND/OR expressions. If the expression
1225 // is not further optimized, it is likely to be transformed back to a
1226 // short-circuited form for code gen, and the source order may have been
1227 // optimized for the most likely conditions.
1228 if (BI->getType()->isIntegerTy(1))
1231 // If this is a subtract instruction which is not already in negate form,
1232 // see if we can convert it to X+-Y.
1233 if (BI->getOpcode() == Instruction::Sub) {
1234 if (ShouldBreakUpSubtract(BI)) {
1235 BI = BreakUpSubtract(BI, ValueRankMap);
1236 // Reset the BBI iterator in case BreakUpSubtract changed the
1237 // instruction it points to.
1241 } else if (BinaryOperator::isNeg(BI)) {
1242 // Otherwise, this is a negation. See if the operand is a multiply tree
1243 // and if this is not an inner node of a multiply tree.
1244 if (isReassociableOp(BI->getOperand(1), Instruction::Mul) &&
1245 (!BI->hasOneUse() ||
1246 !isReassociableOp(BI->use_back(), Instruction::Mul))) {
1247 BI = LowerNegateToMultiply(BI, ValueRankMap);
1253 // If this instruction is a commutative binary operator, process it.
1254 if (!BI->isAssociative()) return;
1255 BinaryOperator *I = cast<BinaryOperator>(BI);
1257 // If this is an interior node of a reassociable tree, ignore it until we
1258 // get to the root of the tree, to avoid N^2 analysis.
1259 if (I->hasOneUse() && isReassociableOp(I->use_back(), I->getOpcode()))
1262 // If this is an add tree that is used by a sub instruction, ignore it
1263 // until we process the subtract.
1264 if (I->hasOneUse() && I->getOpcode() == Instruction::Add &&
1265 cast<Instruction>(I->use_back())->getOpcode() == Instruction::Sub)
1268 ReassociateExpression(I);
1271 Value *Reassociate::ReassociateExpression(BinaryOperator *I) {
1273 // First, walk the expression tree, linearizing the tree, collecting the
1274 // operand information.
1275 SmallVector<ValueEntry, 8> Ops;
1276 LinearizeExprTree(I, Ops);
1278 DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
1280 // Now that we have linearized the tree to a list and have gathered all of
1281 // the operands and their ranks, sort the operands by their rank. Use a
1282 // stable_sort so that values with equal ranks will have their relative
1283 // positions maintained (and so the compiler is deterministic). Note that
1284 // this sorts so that the highest ranking values end up at the beginning of
1286 std::stable_sort(Ops.begin(), Ops.end());
1288 // OptimizeExpression - Now that we have the expression tree in a convenient
1289 // sorted form, optimize it globally if possible.
1290 if (Value *V = OptimizeExpression(I, Ops)) {
1291 // This expression tree simplified to something that isn't a tree,
1293 DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
1294 I->replaceAllUsesWith(V);
1295 if (Instruction *VI = dyn_cast<Instruction>(V))
1296 VI->setDebugLoc(I->getDebugLoc());
1297 RemoveDeadBinaryOp(I);
1302 // We want to sink immediates as deeply as possible except in the case where
1303 // this is a multiply tree used only by an add, and the immediate is a -1.
1304 // In this case we reassociate to put the negation on the outside so that we
1305 // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
1306 if (I->getOpcode() == Instruction::Mul && I->hasOneUse() &&
1307 cast<Instruction>(I->use_back())->getOpcode() == Instruction::Add &&
1308 isa<ConstantInt>(Ops.back().Op) &&
1309 cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
1310 ValueEntry Tmp = Ops.pop_back_val();
1311 Ops.insert(Ops.begin(), Tmp);
1314 DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
1316 if (Ops.size() == 1) {
1317 // This expression tree simplified to something that isn't a tree,
1319 I->replaceAllUsesWith(Ops[0].Op);
1320 if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
1321 OI->setDebugLoc(I->getDebugLoc());
1322 RemoveDeadBinaryOp(I);
1326 // Now that we ordered and optimized the expressions, splat them back into
1327 // the expression tree, removing any unneeded nodes.
1328 RewriteExprTree(I, Ops);
1333 bool Reassociate::runOnFunction(Function &F) {
1334 // Recalculate the rank map for F
1338 for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
1339 for (BasicBlock::iterator BBI = FI->begin(); BBI != FI->end(); )
1340 ReassociateInst(BBI);
1342 // Now that we're done, revisit any instructions which are likely to
1343 // have secondary reassociation opportunities.
1344 while (!RedoInsts.empty())
1345 if (Value *V = RedoInsts.pop_back_val()) {
1346 BasicBlock::iterator BBI = cast<Instruction>(V);
1347 ReassociateInst(BBI);
1350 // Now that we're done, delete any instructions which are no longer used.
1351 while (!DeadInsts.empty())
1352 if (Value *V = DeadInsts.pop_back_val())
1353 RecursivelyDeleteTriviallyDeadInstructions(V);
1355 // We are done with the rank map.
1357 ValueRankMap.clear();