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 #include "llvm/Transforms/Scalar.h"
24 #include "llvm/ADT/DenseMap.h"
25 #include "llvm/ADT/PostOrderIterator.h"
26 #include "llvm/ADT/STLExtras.h"
27 #include "llvm/ADT/SetVector.h"
28 #include "llvm/ADT/Statistic.h"
29 #include "llvm/IR/CFG.h"
30 #include "llvm/IR/Constants.h"
31 #include "llvm/IR/DerivedTypes.h"
32 #include "llvm/IR/Function.h"
33 #include "llvm/IR/IRBuilder.h"
34 #include "llvm/IR/Instructions.h"
35 #include "llvm/IR/IntrinsicInst.h"
36 #include "llvm/IR/ValueHandle.h"
37 #include "llvm/Pass.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Support/raw_ostream.h"
40 #include "llvm/Transforms/Utils/Local.h"
44 #define DEBUG_TYPE "reassociate"
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 Ops[i].Op->printAsOperand(dbgs(), 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;
114 /// Utility class representing a non-constant Xor-operand. We classify
115 /// non-constant Xor-Operands into two categories:
116 /// C1) The operand is in the form "X & C", where C is a constant and C != ~0
118 /// C2.1) The operand is in the form of "X | C", where C is a non-zero
120 /// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
121 /// operand as "E | 0"
126 bool isInvalid() const { return SymbolicPart == nullptr; }
127 bool isOrExpr() const { return isOr; }
128 Value *getValue() const { return OrigVal; }
129 Value *getSymbolicPart() const { return SymbolicPart; }
130 unsigned getSymbolicRank() const { return SymbolicRank; }
131 const APInt &getConstPart() const { return ConstPart; }
133 void Invalidate() { SymbolicPart = OrigVal = nullptr; }
134 void setSymbolicRank(unsigned R) { SymbolicRank = R; }
136 // Sort the XorOpnd-Pointer in ascending order of symbolic-value-rank.
137 // The purpose is twofold:
138 // 1) Cluster together the operands sharing the same symbolic-value.
139 // 2) Operand having smaller symbolic-value-rank is permuted earlier, which
140 // could potentially shorten crital path, and expose more loop-invariants.
141 // Note that values' rank are basically defined in RPO order (FIXME).
142 // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
143 // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
144 // "z" in the order of X-Y-Z is better than any other orders.
145 struct PtrSortFunctor {
146 bool operator()(XorOpnd * const &LHS, XorOpnd * const &RHS) {
147 return LHS->getSymbolicRank() < RHS->getSymbolicRank();
154 unsigned SymbolicRank;
160 class Reassociate : public FunctionPass {
161 DenseMap<BasicBlock*, unsigned> RankMap;
162 DenseMap<AssertingVH<Value>, unsigned> ValueRankMap;
163 SetVector<AssertingVH<Instruction> > RedoInsts;
166 static char ID; // Pass identification, replacement for typeid
167 Reassociate() : FunctionPass(ID) {
168 initializeReassociatePass(*PassRegistry::getPassRegistry());
171 bool runOnFunction(Function &F) override;
173 void getAnalysisUsage(AnalysisUsage &AU) const override {
174 AU.setPreservesCFG();
177 void BuildRankMap(Function &F);
178 unsigned getRank(Value *V);
179 void canonicalizeOperands(Instruction *I);
180 void ReassociateExpression(BinaryOperator *I);
181 void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
182 Value *OptimizeExpression(BinaryOperator *I,
183 SmallVectorImpl<ValueEntry> &Ops);
184 Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
185 Value *OptimizeXor(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
186 bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, APInt &ConstOpnd,
188 bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
189 APInt &ConstOpnd, Value *&Res);
190 bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
191 SmallVectorImpl<Factor> &Factors);
192 Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
193 SmallVectorImpl<Factor> &Factors);
194 Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
195 Value *RemoveFactorFromExpression(Value *V, Value *Factor);
196 void EraseInst(Instruction *I);
197 void OptimizeInst(Instruction *I);
198 Instruction *canonicalizeNegConstExpr(Instruction *I);
202 XorOpnd::XorOpnd(Value *V) {
203 assert(!isa<ConstantInt>(V) && "No ConstantInt");
205 Instruction *I = dyn_cast<Instruction>(V);
208 if (I && (I->getOpcode() == Instruction::Or ||
209 I->getOpcode() == Instruction::And)) {
210 Value *V0 = I->getOperand(0);
211 Value *V1 = I->getOperand(1);
212 if (isa<ConstantInt>(V0))
215 if (ConstantInt *C = dyn_cast<ConstantInt>(V1)) {
216 ConstPart = C->getValue();
218 isOr = (I->getOpcode() == Instruction::Or);
223 // view the operand as "V | 0"
225 ConstPart = APInt::getNullValue(V->getType()->getIntegerBitWidth());
229 char Reassociate::ID = 0;
230 INITIALIZE_PASS(Reassociate, "reassociate",
231 "Reassociate expressions", false, false)
233 // Public interface to the Reassociate pass
234 FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
236 /// isReassociableOp - Return true if V is an instruction of the specified
237 /// opcode and if it only has one use.
238 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
239 if (V->hasOneUse() && isa<Instruction>(V) &&
240 cast<Instruction>(V)->getOpcode() == Opcode &&
241 (!isa<FPMathOperator>(V) ||
242 cast<Instruction>(V)->hasUnsafeAlgebra()))
243 return cast<BinaryOperator>(V);
247 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1,
249 if (V->hasOneUse() && isa<Instruction>(V) &&
250 (cast<Instruction>(V)->getOpcode() == Opcode1 ||
251 cast<Instruction>(V)->getOpcode() == Opcode2) &&
252 (!isa<FPMathOperator>(V) ||
253 cast<Instruction>(V)->hasUnsafeAlgebra()))
254 return cast<BinaryOperator>(V);
258 static bool isUnmovableInstruction(Instruction *I) {
259 switch (I->getOpcode()) {
260 case Instruction::PHI:
261 case Instruction::LandingPad:
262 case Instruction::Alloca:
263 case Instruction::Load:
264 case Instruction::Invoke:
265 case Instruction::UDiv:
266 case Instruction::SDiv:
267 case Instruction::FDiv:
268 case Instruction::URem:
269 case Instruction::SRem:
270 case Instruction::FRem:
272 case Instruction::Call:
273 return !isa<DbgInfoIntrinsic>(I);
279 void Reassociate::BuildRankMap(Function &F) {
282 // Assign distinct ranks to function arguments.
283 for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I) {
284 ValueRankMap[&*I] = ++i;
285 DEBUG(dbgs() << "Calculated Rank[" << I->getName() << "] = " << i << "\n");
288 ReversePostOrderTraversal<Function*> RPOT(&F);
289 for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
290 E = RPOT.end(); I != E; ++I) {
292 unsigned BBRank = RankMap[BB] = ++i << 16;
294 // Walk the basic block, adding precomputed ranks for any instructions that
295 // we cannot move. This ensures that the ranks for these instructions are
296 // all different in the block.
297 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
298 if (isUnmovableInstruction(I))
299 ValueRankMap[&*I] = ++BBRank;
303 unsigned Reassociate::getRank(Value *V) {
304 Instruction *I = dyn_cast<Instruction>(V);
306 if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
307 return 0; // Otherwise it's a global or constant, rank 0.
310 if (unsigned Rank = ValueRankMap[I])
311 return Rank; // Rank already known?
313 // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
314 // we can reassociate expressions for code motion! Since we do not recurse
315 // for PHI nodes, we cannot have infinite recursion here, because there
316 // cannot be loops in the value graph that do not go through PHI nodes.
317 unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
318 for (unsigned i = 0, e = I->getNumOperands();
319 i != e && Rank != MaxRank; ++i)
320 Rank = std::max(Rank, getRank(I->getOperand(i)));
322 // If this is a not or neg instruction, do not count it for rank. This
323 // assures us that X and ~X will have the same rank.
324 Type *Ty = V->getType();
325 if ((!Ty->isIntegerTy() && !Ty->isFloatingPointTy()) ||
326 (!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I) &&
327 !BinaryOperator::isFNeg(I)))
330 DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " << Rank << "\n");
332 return ValueRankMap[I] = Rank;
335 // Canonicalize constants to RHS. Otherwise, sort the operands by rank.
336 void Reassociate::canonicalizeOperands(Instruction *I) {
337 assert(isa<BinaryOperator>(I) && "Expected binary operator.");
338 assert(I->isCommutative() && "Expected commutative operator.");
340 Value *LHS = I->getOperand(0);
341 Value *RHS = I->getOperand(1);
342 unsigned LHSRank = getRank(LHS);
343 unsigned RHSRank = getRank(RHS);
345 if (isa<Constant>(RHS))
348 if (isa<Constant>(LHS) || RHSRank < LHSRank)
349 cast<BinaryOperator>(I)->swapOperands();
352 static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name,
353 Instruction *InsertBefore, Value *FlagsOp) {
354 if (S1->getType()->isIntegerTy())
355 return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore);
357 BinaryOperator *Res =
358 BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore);
359 Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
364 static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name,
365 Instruction *InsertBefore, Value *FlagsOp) {
366 if (S1->getType()->isIntegerTy())
367 return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore);
369 BinaryOperator *Res =
370 BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore);
371 Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
376 static BinaryOperator *CreateNeg(Value *S1, const Twine &Name,
377 Instruction *InsertBefore, Value *FlagsOp) {
378 if (S1->getType()->isIntegerTy())
379 return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
381 BinaryOperator *Res = BinaryOperator::CreateFNeg(S1, Name, InsertBefore);
382 Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
387 /// LowerNegateToMultiply - Replace 0-X with X*-1.
389 static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) {
390 Type *Ty = Neg->getType();
391 Constant *NegOne = Ty->isIntegerTy() ? ConstantInt::getAllOnesValue(Ty)
392 : ConstantFP::get(Ty, -1.0);
394 BinaryOperator *Res = CreateMul(Neg->getOperand(1), NegOne, "", Neg, Neg);
395 Neg->setOperand(1, Constant::getNullValue(Ty)); // Drop use of op.
397 Neg->replaceAllUsesWith(Res);
398 Res->setDebugLoc(Neg->getDebugLoc());
402 /// CarmichaelShift - Returns k such that lambda(2^Bitwidth) = 2^k, where lambda
403 /// is the Carmichael function. This means that x^(2^k) === 1 mod 2^Bitwidth for
404 /// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic.
405 /// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every
406 /// even x in Bitwidth-bit arithmetic.
407 static unsigned CarmichaelShift(unsigned Bitwidth) {
413 /// IncorporateWeight - Add the extra weight 'RHS' to the existing weight 'LHS',
414 /// reducing the combined weight using any special properties of the operation.
415 /// The existing weight LHS represents the computation X op X op ... op X where
416 /// X occurs LHS times. The combined weight represents X op X op ... op X with
417 /// X occurring LHS + RHS times. If op is "Xor" for example then the combined
418 /// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even;
419 /// the routine returns 1 in LHS in the first case, and 0 in LHS in the second.
420 static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) {
421 // If we were working with infinite precision arithmetic then the combined
422 // weight would be LHS + RHS. But we are using finite precision arithmetic,
423 // and the APInt sum LHS + RHS may not be correct if it wraps (it is correct
424 // for nilpotent operations and addition, but not for idempotent operations
425 // and multiplication), so it is important to correctly reduce the combined
426 // weight back into range if wrapping would be wrong.
428 // If RHS is zero then the weight didn't change.
429 if (RHS.isMinValue())
431 // If LHS is zero then the combined weight is RHS.
432 if (LHS.isMinValue()) {
436 // From this point on we know that neither LHS nor RHS is zero.
438 if (Instruction::isIdempotent(Opcode)) {
439 // Idempotent means X op X === X, so any non-zero weight is equivalent to a
440 // weight of 1. Keeping weights at zero or one also means that wrapping is
442 assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
443 return; // Return a weight of 1.
445 if (Instruction::isNilpotent(Opcode)) {
446 // Nilpotent means X op X === 0, so reduce weights modulo 2.
447 assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
448 LHS = 0; // 1 + 1 === 0 modulo 2.
451 if (Opcode == Instruction::Add || Opcode == Instruction::FAdd) {
452 // TODO: Reduce the weight by exploiting nsw/nuw?
457 assert((Opcode == Instruction::Mul || Opcode == Instruction::FMul) &&
458 "Unknown associative operation!");
459 unsigned Bitwidth = LHS.getBitWidth();
460 // If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth
461 // can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth
462 // bit number x, since either x is odd in which case x^CM = 1, or x is even in
463 // which case both x^W and x^(W - CM) are zero. By subtracting off multiples
464 // of CM like this weights can always be reduced to the range [0, CM+Bitwidth)
465 // which by a happy accident means that they can always be represented using
467 // TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than
468 // the Carmichael number).
470 /// CM - The value of Carmichael's lambda function.
471 APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth));
472 // Any weight W >= Threshold can be replaced with W - CM.
473 APInt Threshold = CM + Bitwidth;
474 assert(LHS.ult(Threshold) && RHS.ult(Threshold) && "Weights not reduced!");
475 // For Bitwidth 4 or more the following sum does not overflow.
477 while (LHS.uge(Threshold))
480 // To avoid problems with overflow do everything the same as above but using
482 unsigned CM = 1U << CarmichaelShift(Bitwidth);
483 unsigned Threshold = CM + Bitwidth;
484 assert(LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold &&
485 "Weights not reduced!");
486 unsigned Total = LHS.getZExtValue() + RHS.getZExtValue();
487 while (Total >= Threshold)
493 typedef std::pair<Value*, APInt> RepeatedValue;
495 /// LinearizeExprTree - Given an associative binary expression, return the leaf
496 /// nodes in Ops along with their weights (how many times the leaf occurs). The
497 /// original expression is the same as
498 /// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
500 /// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
504 /// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
506 /// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
508 /// This routine may modify the function, in which case it returns 'true'. The
509 /// changes it makes may well be destructive, changing the value computed by 'I'
510 /// to something completely different. Thus if the routine returns 'true' then
511 /// you MUST either replace I with a new expression computed from the Ops array,
512 /// or use RewriteExprTree to put the values back in.
514 /// A leaf node is either not a binary operation of the same kind as the root
515 /// node 'I' (i.e. is not a binary operator at all, or is, but with a different
516 /// opcode), or is the same kind of binary operator but has a use which either
517 /// does not belong to the expression, or does belong to the expression but is
518 /// a leaf node. Every leaf node has at least one use that is a non-leaf node
519 /// of the expression, while for non-leaf nodes (except for the root 'I') every
520 /// use is a non-leaf node of the expression.
523 /// expression graph node names
533 /// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
534 /// that order) (C, 1), (E, 1), (F, 2), (G, 2).
536 /// The expression is maximal: if some instruction is a binary operator of the
537 /// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
538 /// then the instruction also belongs to the expression, is not a leaf node of
539 /// it, and its operands also belong to the expression (but may be leaf nodes).
541 /// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
542 /// order to ensure that every non-root node in the expression has *exactly one*
543 /// use by a non-leaf node of the expression. This destruction means that the
544 /// caller MUST either replace 'I' with a new expression or use something like
545 /// RewriteExprTree to put the values back in if the routine indicates that it
546 /// made a change by returning 'true'.
548 /// In the above example either the right operand of A or the left operand of B
549 /// will be replaced by undef. If it is B's operand then this gives:
553 /// + + | A, B - operand of B replaced with undef
559 /// Note that such undef operands can only be reached by passing through 'I'.
560 /// For example, if you visit operands recursively starting from a leaf node
561 /// then you will never see such an undef operand unless you get back to 'I',
562 /// which requires passing through a phi node.
564 /// Note that this routine may also mutate binary operators of the wrong type
565 /// that have all uses inside the expression (i.e. only used by non-leaf nodes
566 /// of the expression) if it can turn them into binary operators of the right
567 /// type and thus make the expression bigger.
569 static bool LinearizeExprTree(BinaryOperator *I,
570 SmallVectorImpl<RepeatedValue> &Ops) {
571 DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
572 unsigned Bitwidth = I->getType()->getScalarType()->getPrimitiveSizeInBits();
573 unsigned Opcode = I->getOpcode();
574 assert(I->isAssociative() && I->isCommutative() &&
575 "Expected an associative and commutative operation!");
577 // Visit all operands of the expression, keeping track of their weight (the
578 // number of paths from the expression root to the operand, or if you like
579 // the number of times that operand occurs in the linearized expression).
580 // For example, if I = X + A, where X = A + B, then I, X and B have weight 1
581 // while A has weight two.
583 // Worklist of non-leaf nodes (their operands are in the expression too) along
584 // with their weights, representing a certain number of paths to the operator.
585 // If an operator occurs in the worklist multiple times then we found multiple
586 // ways to get to it.
587 SmallVector<std::pair<BinaryOperator*, APInt>, 8> Worklist; // (Op, Weight)
588 Worklist.push_back(std::make_pair(I, APInt(Bitwidth, 1)));
589 bool Changed = false;
591 // Leaves of the expression are values that either aren't the right kind of
592 // operation (eg: a constant, or a multiply in an add tree), or are, but have
593 // some uses that are not inside the expression. For example, in I = X + X,
594 // X = A + B, the value X has two uses (by I) that are in the expression. If
595 // X has any other uses, for example in a return instruction, then we consider
596 // X to be a leaf, and won't analyze it further. When we first visit a value,
597 // if it has more than one use then at first we conservatively consider it to
598 // be a leaf. Later, as the expression is explored, we may discover some more
599 // uses of the value from inside the expression. If all uses turn out to be
600 // from within the expression (and the value is a binary operator of the right
601 // kind) then the value is no longer considered to be a leaf, and its operands
604 // Leaves - Keeps track of the set of putative leaves as well as the number of
605 // paths to each leaf seen so far.
606 typedef DenseMap<Value*, APInt> LeafMap;
607 LeafMap Leaves; // Leaf -> Total weight so far.
608 SmallVector<Value*, 8> LeafOrder; // Ensure deterministic leaf output order.
611 SmallPtrSet<Value*, 8> Visited; // For sanity checking the iteration scheme.
613 while (!Worklist.empty()) {
614 std::pair<BinaryOperator*, APInt> P = Worklist.pop_back_val();
615 I = P.first; // We examine the operands of this binary operator.
617 for (unsigned OpIdx = 0; OpIdx < 2; ++OpIdx) { // Visit operands.
618 Value *Op = I->getOperand(OpIdx);
619 APInt Weight = P.second; // Number of paths to this operand.
620 DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n");
621 assert(!Op->use_empty() && "No uses, so how did we get to it?!");
623 // If this is a binary operation of the right kind with only one use then
624 // add its operands to the expression.
625 if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
626 assert(Visited.insert(Op).second && "Not first visit!");
627 DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n");
628 Worklist.push_back(std::make_pair(BO, Weight));
632 // Appears to be a leaf. Is the operand already in the set of leaves?
633 LeafMap::iterator It = Leaves.find(Op);
634 if (It == Leaves.end()) {
635 // Not in the leaf map. Must be the first time we saw this operand.
636 assert(Visited.insert(Op).second && "Not first visit!");
637 if (!Op->hasOneUse()) {
638 // This value has uses not accounted for by the expression, so it is
639 // not safe to modify. Mark it as being a leaf.
640 DEBUG(dbgs() << "ADD USES LEAF: " << *Op << " (" << Weight << ")\n");
641 LeafOrder.push_back(Op);
645 // No uses outside the expression, try morphing it.
646 } else if (It != Leaves.end()) {
647 // Already in the leaf map.
648 assert(Visited.count(Op) && "In leaf map but not visited!");
650 // Update the number of paths to the leaf.
651 IncorporateWeight(It->second, Weight, Opcode);
653 #if 0 // TODO: Re-enable once PR13021 is fixed.
654 // The leaf already has one use from inside the expression. As we want
655 // exactly one such use, drop this new use of the leaf.
656 assert(!Op->hasOneUse() && "Only one use, but we got here twice!");
657 I->setOperand(OpIdx, UndefValue::get(I->getType()));
660 // If the leaf is a binary operation of the right kind and we now see
661 // that its multiple original uses were in fact all by nodes belonging
662 // to the expression, then no longer consider it to be a leaf and add
663 // its operands to the expression.
664 if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
665 DEBUG(dbgs() << "UNLEAF: " << *Op << " (" << It->second << ")\n");
666 Worklist.push_back(std::make_pair(BO, It->second));
672 // If we still have uses that are not accounted for by the expression
673 // then it is not safe to modify the value.
674 if (!Op->hasOneUse())
677 // No uses outside the expression, try morphing it.
679 Leaves.erase(It); // Since the value may be morphed below.
682 // At this point we have a value which, first of all, is not a binary
683 // expression of the right kind, and secondly, is only used inside the
684 // expression. This means that it can safely be modified. See if we
685 // can usefully morph it into an expression of the right kind.
686 assert((!isa<Instruction>(Op) ||
687 cast<Instruction>(Op)->getOpcode() != Opcode
688 || (isa<FPMathOperator>(Op) &&
689 !cast<Instruction>(Op)->hasUnsafeAlgebra())) &&
690 "Should have been handled above!");
691 assert(Op->hasOneUse() && "Has uses outside the expression tree!");
693 // If this is a multiply expression, turn any internal negations into
694 // multiplies by -1 so they can be reassociated.
695 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op))
696 if ((Opcode == Instruction::Mul && BinaryOperator::isNeg(BO)) ||
697 (Opcode == Instruction::FMul && BinaryOperator::isFNeg(BO))) {
698 DEBUG(dbgs() << "MORPH LEAF: " << *Op << " (" << Weight << ") TO ");
699 BO = LowerNegateToMultiply(BO);
700 DEBUG(dbgs() << *BO << '\n');
701 Worklist.push_back(std::make_pair(BO, Weight));
706 // Failed to morph into an expression of the right type. This really is
708 DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n");
709 assert(!isReassociableOp(Op, Opcode) && "Value was morphed?");
710 LeafOrder.push_back(Op);
715 // The leaves, repeated according to their weights, represent the linearized
716 // form of the expression.
717 for (unsigned i = 0, e = LeafOrder.size(); i != e; ++i) {
718 Value *V = LeafOrder[i];
719 LeafMap::iterator It = Leaves.find(V);
720 if (It == Leaves.end())
721 // Node initially thought to be a leaf wasn't.
723 assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!");
724 APInt Weight = It->second;
725 if (Weight.isMinValue())
726 // Leaf already output or weight reduction eliminated it.
728 // Ensure the leaf is only output once.
730 Ops.push_back(std::make_pair(V, Weight));
733 // For nilpotent operations or addition there may be no operands, for example
734 // because the expression was "X xor X" or consisted of 2^Bitwidth additions:
735 // in both cases the weight reduces to 0 causing the value to be skipped.
737 Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
738 assert(Identity && "Associative operation without identity!");
739 Ops.push_back(std::make_pair(Identity, APInt(Bitwidth, 1)));
745 // RewriteExprTree - Now that the operands for this expression tree are
746 // linearized and optimized, emit them in-order.
747 void Reassociate::RewriteExprTree(BinaryOperator *I,
748 SmallVectorImpl<ValueEntry> &Ops) {
749 assert(Ops.size() > 1 && "Single values should be used directly!");
751 // Since our optimizations should never increase the number of operations, the
752 // new expression can usually be written reusing the existing binary operators
753 // from the original expression tree, without creating any new instructions,
754 // though the rewritten expression may have a completely different topology.
755 // We take care to not change anything if the new expression will be the same
756 // as the original. If more than trivial changes (like commuting operands)
757 // were made then we are obliged to clear out any optional subclass data like
760 /// NodesToRewrite - Nodes from the original expression available for writing
761 /// the new expression into.
762 SmallVector<BinaryOperator*, 8> NodesToRewrite;
763 unsigned Opcode = I->getOpcode();
764 BinaryOperator *Op = I;
766 /// NotRewritable - The operands being written will be the leaves of the new
767 /// expression and must not be used as inner nodes (via NodesToRewrite) by
768 /// mistake. Inner nodes are always reassociable, and usually leaves are not
769 /// (if they were they would have been incorporated into the expression and so
770 /// would not be leaves), so most of the time there is no danger of this. But
771 /// in rare cases a leaf may become reassociable if an optimization kills uses
772 /// of it, or it may momentarily become reassociable during rewriting (below)
773 /// due it being removed as an operand of one of its uses. Ensure that misuse
774 /// of leaf nodes as inner nodes cannot occur by remembering all of the future
775 /// leaves and refusing to reuse any of them as inner nodes.
776 SmallPtrSet<Value*, 8> NotRewritable;
777 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
778 NotRewritable.insert(Ops[i].Op);
780 // ExpressionChanged - Non-null if the rewritten expression differs from the
781 // original in some non-trivial way, requiring the clearing of optional flags.
782 // Flags are cleared from the operator in ExpressionChanged up to I inclusive.
783 BinaryOperator *ExpressionChanged = nullptr;
784 for (unsigned i = 0; ; ++i) {
785 // The last operation (which comes earliest in the IR) is special as both
786 // operands will come from Ops, rather than just one with the other being
788 if (i+2 == Ops.size()) {
789 Value *NewLHS = Ops[i].Op;
790 Value *NewRHS = Ops[i+1].Op;
791 Value *OldLHS = Op->getOperand(0);
792 Value *OldRHS = Op->getOperand(1);
794 if (NewLHS == OldLHS && NewRHS == OldRHS)
795 // Nothing changed, leave it alone.
798 if (NewLHS == OldRHS && NewRHS == OldLHS) {
799 // The order of the operands was reversed. Swap them.
800 DEBUG(dbgs() << "RA: " << *Op << '\n');
802 DEBUG(dbgs() << "TO: " << *Op << '\n');
808 // The new operation differs non-trivially from the original. Overwrite
809 // the old operands with the new ones.
810 DEBUG(dbgs() << "RA: " << *Op << '\n');
811 if (NewLHS != OldLHS) {
812 BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
813 if (BO && !NotRewritable.count(BO))
814 NodesToRewrite.push_back(BO);
815 Op->setOperand(0, NewLHS);
817 if (NewRHS != OldRHS) {
818 BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
819 if (BO && !NotRewritable.count(BO))
820 NodesToRewrite.push_back(BO);
821 Op->setOperand(1, NewRHS);
823 DEBUG(dbgs() << "TO: " << *Op << '\n');
825 ExpressionChanged = Op;
832 // Not the last operation. The left-hand side will be a sub-expression
833 // while the right-hand side will be the current element of Ops.
834 Value *NewRHS = Ops[i].Op;
835 if (NewRHS != Op->getOperand(1)) {
836 DEBUG(dbgs() << "RA: " << *Op << '\n');
837 if (NewRHS == Op->getOperand(0)) {
838 // The new right-hand side was already present as the left operand. If
839 // we are lucky then swapping the operands will sort out both of them.
842 // Overwrite with the new right-hand side.
843 BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
844 if (BO && !NotRewritable.count(BO))
845 NodesToRewrite.push_back(BO);
846 Op->setOperand(1, NewRHS);
847 ExpressionChanged = Op;
849 DEBUG(dbgs() << "TO: " << *Op << '\n');
854 // Now deal with the left-hand side. If this is already an operation node
855 // from the original expression then just rewrite the rest of the expression
857 BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode);
858 if (BO && !NotRewritable.count(BO)) {
863 // Otherwise, grab a spare node from the original expression and use that as
864 // the left-hand side. If there are no nodes left then the optimizers made
865 // an expression with more nodes than the original! This usually means that
866 // they did something stupid but it might mean that the problem was just too
867 // hard (finding the mimimal number of multiplications needed to realize a
868 // multiplication expression is NP-complete). Whatever the reason, smart or
869 // stupid, create a new node if there are none left.
870 BinaryOperator *NewOp;
871 if (NodesToRewrite.empty()) {
872 Constant *Undef = UndefValue::get(I->getType());
873 NewOp = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
874 Undef, Undef, "", I);
875 if (NewOp->getType()->isFloatingPointTy())
876 NewOp->setFastMathFlags(I->getFastMathFlags());
878 NewOp = NodesToRewrite.pop_back_val();
881 DEBUG(dbgs() << "RA: " << *Op << '\n');
882 Op->setOperand(0, NewOp);
883 DEBUG(dbgs() << "TO: " << *Op << '\n');
884 ExpressionChanged = Op;
890 // If the expression changed non-trivially then clear out all subclass data
891 // starting from the operator specified in ExpressionChanged, and compactify
892 // the operators to just before the expression root to guarantee that the
893 // expression tree is dominated by all of Ops.
894 if (ExpressionChanged)
896 // Preserve FastMathFlags.
897 if (isa<FPMathOperator>(I)) {
898 FastMathFlags Flags = I->getFastMathFlags();
899 ExpressionChanged->clearSubclassOptionalData();
900 ExpressionChanged->setFastMathFlags(Flags);
902 ExpressionChanged->clearSubclassOptionalData();
904 if (ExpressionChanged == I)
906 ExpressionChanged->moveBefore(I);
907 ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->user_begin());
910 // Throw away any left over nodes from the original expression.
911 for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)
912 RedoInsts.insert(NodesToRewrite[i]);
915 /// NegateValue - Insert instructions before the instruction pointed to by BI,
916 /// that computes the negative version of the value specified. The negative
917 /// version of the value is returned, and BI is left pointing at the instruction
918 /// that should be processed next by the reassociation pass.
919 static Value *NegateValue(Value *V, Instruction *BI) {
920 if (Constant *C = dyn_cast<Constant>(V)) {
921 if (C->getType()->isFPOrFPVectorTy()) {
922 return ConstantExpr::getFNeg(C);
924 return ConstantExpr::getNeg(C);
928 // We are trying to expose opportunity for reassociation. One of the things
929 // that we want to do to achieve this is to push a negation as deep into an
930 // expression chain as possible, to expose the add instructions. In practice,
931 // this means that we turn this:
932 // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
933 // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
934 // the constants. We assume that instcombine will clean up the mess later if
935 // we introduce tons of unnecessary negation instructions.
937 if (BinaryOperator *I =
938 isReassociableOp(V, Instruction::Add, Instruction::FAdd)) {
939 // Push the negates through the add.
940 I->setOperand(0, NegateValue(I->getOperand(0), BI));
941 I->setOperand(1, NegateValue(I->getOperand(1), BI));
943 // We must move the add instruction here, because the neg instructions do
944 // not dominate the old add instruction in general. By moving it, we are
945 // assured that the neg instructions we just inserted dominate the
946 // instruction we are about to insert after them.
949 I->setName(I->getName()+".neg");
953 // Okay, we need to materialize a negated version of V with an instruction.
954 // Scan the use lists of V to see if we have one already.
955 for (User *U : V->users()) {
956 if (!BinaryOperator::isNeg(U) && !BinaryOperator::isFNeg(U))
959 // We found one! Now we have to make sure that the definition dominates
960 // this use. We do this by moving it to the entry block (if it is a
961 // non-instruction value) or right after the definition. These negates will
962 // be zapped by reassociate later, so we don't need much finesse here.
963 BinaryOperator *TheNeg = cast<BinaryOperator>(U);
965 // Verify that the negate is in this function, V might be a constant expr.
966 if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
969 BasicBlock::iterator InsertPt;
970 if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
971 if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
972 InsertPt = II->getNormalDest()->begin();
974 InsertPt = InstInput;
977 while (isa<PHINode>(InsertPt)) ++InsertPt;
979 InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
981 TheNeg->moveBefore(InsertPt);
985 // Insert a 'neg' instruction that subtracts the value from zero to get the
987 return CreateNeg(V, V->getName() + ".neg", BI, BI);
990 /// ShouldBreakUpSubtract - Return true if we should break up this subtract of
991 /// X-Y into (X + -Y).
992 static bool ShouldBreakUpSubtract(Instruction *Sub) {
993 // If this is a negation, we can't split it up!
994 if (BinaryOperator::isNeg(Sub) || BinaryOperator::isFNeg(Sub))
997 // Don't breakup X - undef.
998 if (isa<UndefValue>(Sub->getOperand(1)))
1001 // Don't bother to break this up unless either the LHS is an associable add or
1002 // subtract or if this is only used by one.
1003 Value *V0 = Sub->getOperand(0);
1004 if (isReassociableOp(V0, Instruction::Add, Instruction::FAdd) ||
1005 isReassociableOp(V0, Instruction::Sub, Instruction::FSub))
1007 Value *V1 = Sub->getOperand(1);
1008 if (isReassociableOp(V1, Instruction::Add, Instruction::FAdd) ||
1009 isReassociableOp(V1, Instruction::Sub, Instruction::FSub))
1011 Value *VB = Sub->user_back();
1012 if (Sub->hasOneUse() &&
1013 (isReassociableOp(VB, Instruction::Add, Instruction::FAdd) ||
1014 isReassociableOp(VB, Instruction::Sub, Instruction::FSub)))
1020 /// BreakUpSubtract - If we have (X-Y), and if either X is an add, or if this is
1021 /// only used by an add, transform this into (X+(0-Y)) to promote better
1023 static BinaryOperator *BreakUpSubtract(Instruction *Sub) {
1024 // Convert a subtract into an add and a neg instruction. This allows sub
1025 // instructions to be commuted with other add instructions.
1027 // Calculate the negative value of Operand 1 of the sub instruction,
1028 // and set it as the RHS of the add instruction we just made.
1030 Value *NegVal = NegateValue(Sub->getOperand(1), Sub);
1031 BinaryOperator *New = CreateAdd(Sub->getOperand(0), NegVal, "", Sub, Sub);
1032 Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op.
1033 Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op.
1036 // Everyone now refers to the add instruction.
1037 Sub->replaceAllUsesWith(New);
1038 New->setDebugLoc(Sub->getDebugLoc());
1040 DEBUG(dbgs() << "Negated: " << *New << '\n');
1044 /// ConvertShiftToMul - If this is a shift of a reassociable multiply or is used
1045 /// by one, change this into a multiply by a constant to assist with further
1047 static BinaryOperator *ConvertShiftToMul(Instruction *Shl) {
1048 Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
1049 MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
1051 BinaryOperator *Mul =
1052 BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
1053 Shl->setOperand(0, UndefValue::get(Shl->getType())); // Drop use of op.
1056 // Everyone now refers to the mul instruction.
1057 Shl->replaceAllUsesWith(Mul);
1058 Mul->setDebugLoc(Shl->getDebugLoc());
1060 // We can safely preserve the nuw flag in all cases. It's also safe to turn a
1061 // nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special
1063 bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap();
1064 bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap();
1066 Mul->setHasNoSignedWrap(true);
1067 Mul->setHasNoUnsignedWrap(NUW);
1071 /// FindInOperandList - Scan backwards and forwards among values with the same
1072 /// rank as element i to see if X exists. If X does not exist, return i. This
1073 /// is useful when scanning for 'x' when we see '-x' because they both get the
1075 static unsigned FindInOperandList(SmallVectorImpl<ValueEntry> &Ops, unsigned i,
1077 unsigned XRank = Ops[i].Rank;
1078 unsigned e = Ops.size();
1079 for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
1082 if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
1083 if (Instruction *I2 = dyn_cast<Instruction>(X))
1084 if (I1->isIdenticalTo(I2))
1088 for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
1091 if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
1092 if (Instruction *I2 = dyn_cast<Instruction>(X))
1093 if (I1->isIdenticalTo(I2))
1099 /// EmitAddTreeOfValues - Emit a tree of add instructions, summing Ops together
1100 /// and returning the result. Insert the tree before I.
1101 static Value *EmitAddTreeOfValues(Instruction *I,
1102 SmallVectorImpl<WeakVH> &Ops){
1103 if (Ops.size() == 1) return Ops.back();
1105 Value *V1 = Ops.back();
1107 Value *V2 = EmitAddTreeOfValues(I, Ops);
1108 return CreateAdd(V2, V1, "tmp", I, I);
1111 /// RemoveFactorFromExpression - If V is an expression tree that is a
1112 /// multiplication sequence, and if this sequence contains a multiply by Factor,
1113 /// remove Factor from the tree and return the new tree.
1114 Value *Reassociate::RemoveFactorFromExpression(Value *V, Value *Factor) {
1115 BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
1119 SmallVector<RepeatedValue, 8> Tree;
1120 MadeChange |= LinearizeExprTree(BO, Tree);
1121 SmallVector<ValueEntry, 8> Factors;
1122 Factors.reserve(Tree.size());
1123 for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
1124 RepeatedValue E = Tree[i];
1125 Factors.append(E.second.getZExtValue(),
1126 ValueEntry(getRank(E.first), E.first));
1129 bool FoundFactor = false;
1130 bool NeedsNegate = false;
1131 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1132 if (Factors[i].Op == Factor) {
1134 Factors.erase(Factors.begin()+i);
1138 // If this is a negative version of this factor, remove it.
1139 if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor)) {
1140 if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
1141 if (FC1->getValue() == -FC2->getValue()) {
1142 FoundFactor = NeedsNegate = true;
1143 Factors.erase(Factors.begin()+i);
1146 } else if (ConstantFP *FC1 = dyn_cast<ConstantFP>(Factor)) {
1147 if (ConstantFP *FC2 = dyn_cast<ConstantFP>(Factors[i].Op)) {
1148 APFloat F1(FC1->getValueAPF());
1149 APFloat F2(FC2->getValueAPF());
1151 if (F1.compare(F2) == APFloat::cmpEqual) {
1152 FoundFactor = NeedsNegate = true;
1153 Factors.erase(Factors.begin() + i);
1161 // Make sure to restore the operands to the expression tree.
1162 RewriteExprTree(BO, Factors);
1166 BasicBlock::iterator InsertPt = BO; ++InsertPt;
1168 // If this was just a single multiply, remove the multiply and return the only
1169 // remaining operand.
1170 if (Factors.size() == 1) {
1171 RedoInsts.insert(BO);
1174 RewriteExprTree(BO, Factors);
1179 V = CreateNeg(V, "neg", InsertPt, BO);
1184 /// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively
1185 /// add its operands as factors, otherwise add V to the list of factors.
1187 /// Ops is the top-level list of add operands we're trying to factor.
1188 static void FindSingleUseMultiplyFactors(Value *V,
1189 SmallVectorImpl<Value*> &Factors,
1190 const SmallVectorImpl<ValueEntry> &Ops) {
1191 BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
1193 Factors.push_back(V);
1197 // Otherwise, add the LHS and RHS to the list of factors.
1198 FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops);
1199 FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops);
1202 /// OptimizeAndOrXor - Optimize a series of operands to an 'and', 'or', or 'xor'
1203 /// instruction. This optimizes based on identities. If it can be reduced to
1204 /// a single Value, it is returned, otherwise the Ops list is mutated as
1206 static Value *OptimizeAndOrXor(unsigned Opcode,
1207 SmallVectorImpl<ValueEntry> &Ops) {
1208 // Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
1209 // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
1210 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1211 // First, check for X and ~X in the operand list.
1212 assert(i < Ops.size());
1213 if (BinaryOperator::isNot(Ops[i].Op)) { // Cannot occur for ^.
1214 Value *X = BinaryOperator::getNotArgument(Ops[i].Op);
1215 unsigned FoundX = FindInOperandList(Ops, i, X);
1217 if (Opcode == Instruction::And) // ...&X&~X = 0
1218 return Constant::getNullValue(X->getType());
1220 if (Opcode == Instruction::Or) // ...|X|~X = -1
1221 return Constant::getAllOnesValue(X->getType());
1225 // Next, check for duplicate pairs of values, which we assume are next to
1226 // each other, due to our sorting criteria.
1227 assert(i < Ops.size());
1228 if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
1229 if (Opcode == Instruction::And || Opcode == Instruction::Or) {
1230 // Drop duplicate values for And and Or.
1231 Ops.erase(Ops.begin()+i);
1237 // Drop pairs of values for Xor.
1238 assert(Opcode == Instruction::Xor);
1240 return Constant::getNullValue(Ops[0].Op->getType());
1243 Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
1251 /// Helper funciton of CombineXorOpnd(). It creates a bitwise-and
1252 /// instruction with the given two operands, and return the resulting
1253 /// instruction. There are two special cases: 1) if the constant operand is 0,
1254 /// it will return NULL. 2) if the constant is ~0, the symbolic operand will
1256 static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd,
1257 const APInt &ConstOpnd) {
1258 if (ConstOpnd != 0) {
1259 if (!ConstOpnd.isAllOnesValue()) {
1260 LLVMContext &Ctx = Opnd->getType()->getContext();
1262 I = BinaryOperator::CreateAnd(Opnd, ConstantInt::get(Ctx, ConstOpnd),
1263 "and.ra", InsertBefore);
1264 I->setDebugLoc(InsertBefore->getDebugLoc());
1272 // Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
1273 // into "R ^ C", where C would be 0, and R is a symbolic value.
1275 // If it was successful, true is returned, and the "R" and "C" is returned
1276 // via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
1277 // and both "Res" and "ConstOpnd" remain unchanged.
1279 bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
1280 APInt &ConstOpnd, Value *&Res) {
1281 // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
1282 // = ((x | c1) ^ c1) ^ (c1 ^ c2)
1283 // = (x & ~c1) ^ (c1 ^ c2)
1284 // It is useful only when c1 == c2.
1285 if (Opnd1->isOrExpr() && Opnd1->getConstPart() != 0) {
1286 if (!Opnd1->getValue()->hasOneUse())
1289 const APInt &C1 = Opnd1->getConstPart();
1290 if (C1 != ConstOpnd)
1293 Value *X = Opnd1->getSymbolicPart();
1294 Res = createAndInstr(I, X, ~C1);
1295 // ConstOpnd was C2, now C1 ^ C2.
1298 if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1299 RedoInsts.insert(T);
1306 // Helper function of OptimizeXor(). It tries to simplify
1307 // "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
1310 // If it was successful, true is returned, and the "R" and "C" is returned
1311 // via "Res" and "ConstOpnd", respectively (If the entire expression is
1312 // evaluated to a constant, the Res is set to NULL); otherwise, false is
1313 // returned, and both "Res" and "ConstOpnd" remain unchanged.
1314 bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
1315 APInt &ConstOpnd, Value *&Res) {
1316 Value *X = Opnd1->getSymbolicPart();
1317 if (X != Opnd2->getSymbolicPart())
1320 // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
1321 int DeadInstNum = 1;
1322 if (Opnd1->getValue()->hasOneUse())
1324 if (Opnd2->getValue()->hasOneUse())
1328 // (x | c1) ^ (x & c2)
1329 // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
1330 // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
1331 // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
1333 if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
1334 if (Opnd2->isOrExpr())
1335 std::swap(Opnd1, Opnd2);
1337 const APInt &C1 = Opnd1->getConstPart();
1338 const APInt &C2 = Opnd2->getConstPart();
1339 APInt C3((~C1) ^ C2);
1341 // Do not increase code size!
1342 if (C3 != 0 && !C3.isAllOnesValue()) {
1343 int NewInstNum = ConstOpnd != 0 ? 1 : 2;
1344 if (NewInstNum > DeadInstNum)
1348 Res = createAndInstr(I, X, C3);
1351 } else if (Opnd1->isOrExpr()) {
1352 // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
1354 const APInt &C1 = Opnd1->getConstPart();
1355 const APInt &C2 = Opnd2->getConstPart();
1358 // Do not increase code size
1359 if (C3 != 0 && !C3.isAllOnesValue()) {
1360 int NewInstNum = ConstOpnd != 0 ? 1 : 2;
1361 if (NewInstNum > DeadInstNum)
1365 Res = createAndInstr(I, X, C3);
1368 // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
1370 const APInt &C1 = Opnd1->getConstPart();
1371 const APInt &C2 = Opnd2->getConstPart();
1373 Res = createAndInstr(I, X, C3);
1376 // Put the original operands in the Redo list; hope they will be deleted
1378 if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1379 RedoInsts.insert(T);
1380 if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
1381 RedoInsts.insert(T);
1386 /// Optimize a series of operands to an 'xor' instruction. If it can be reduced
1387 /// to a single Value, it is returned, otherwise the Ops list is mutated as
1389 Value *Reassociate::OptimizeXor(Instruction *I,
1390 SmallVectorImpl<ValueEntry> &Ops) {
1391 if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
1394 if (Ops.size() == 1)
1397 SmallVector<XorOpnd, 8> Opnds;
1398 SmallVector<XorOpnd*, 8> OpndPtrs;
1399 Type *Ty = Ops[0].Op->getType();
1400 APInt ConstOpnd(Ty->getIntegerBitWidth(), 0);
1402 // Step 1: Convert ValueEntry to XorOpnd
1403 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1404 Value *V = Ops[i].Op;
1405 if (!isa<ConstantInt>(V)) {
1407 O.setSymbolicRank(getRank(O.getSymbolicPart()));
1410 ConstOpnd ^= cast<ConstantInt>(V)->getValue();
1413 // NOTE: From this point on, do *NOT* add/delete element to/from "Opnds".
1414 // It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate
1415 // the "OpndPtrs" as well. For the similar reason, do not fuse this loop
1416 // with the previous loop --- the iterator of the "Opnds" may be invalidated
1417 // when new elements are added to the vector.
1418 for (unsigned i = 0, e = Opnds.size(); i != e; ++i)
1419 OpndPtrs.push_back(&Opnds[i]);
1421 // Step 2: Sort the Xor-Operands in a way such that the operands containing
1422 // the same symbolic value cluster together. For instance, the input operand
1423 // sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
1424 // ("x | 123", "x & 789", "y & 456").
1425 std::stable_sort(OpndPtrs.begin(), OpndPtrs.end(), XorOpnd::PtrSortFunctor());
1427 // Step 3: Combine adjacent operands
1428 XorOpnd *PrevOpnd = nullptr;
1429 bool Changed = false;
1430 for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
1431 XorOpnd *CurrOpnd = OpndPtrs[i];
1432 // The combined value
1435 // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
1436 if (ConstOpnd != 0 && CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
1439 *CurrOpnd = XorOpnd(CV);
1441 CurrOpnd->Invalidate();
1446 if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
1447 PrevOpnd = CurrOpnd;
1451 // step 3.2: When previous and current operands share the same symbolic
1452 // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
1454 if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
1455 // Remove previous operand
1456 PrevOpnd->Invalidate();
1458 *CurrOpnd = XorOpnd(CV);
1459 PrevOpnd = CurrOpnd;
1461 CurrOpnd->Invalidate();
1468 // Step 4: Reassemble the Ops
1471 for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
1472 XorOpnd &O = Opnds[i];
1475 ValueEntry VE(getRank(O.getValue()), O.getValue());
1478 if (ConstOpnd != 0) {
1479 Value *C = ConstantInt::get(Ty->getContext(), ConstOpnd);
1480 ValueEntry VE(getRank(C), C);
1483 int Sz = Ops.size();
1485 return Ops.back().Op;
1487 assert(ConstOpnd == 0);
1488 return ConstantInt::get(Ty->getContext(), ConstOpnd);
1495 /// OptimizeAdd - Optimize a series of operands to an 'add' instruction. This
1496 /// optimizes based on identities. If it can be reduced to a single Value, it
1497 /// is returned, otherwise the Ops list is mutated as necessary.
1498 Value *Reassociate::OptimizeAdd(Instruction *I,
1499 SmallVectorImpl<ValueEntry> &Ops) {
1500 // Scan the operand lists looking for X and -X pairs. If we find any, we
1501 // can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it,
1503 // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
1505 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1506 Value *TheOp = Ops[i].Op;
1507 // Check to see if we've seen this operand before. If so, we factor all
1508 // instances of the operand together. Due to our sorting criteria, we know
1509 // that these need to be next to each other in the vector.
1510 if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
1511 // Rescan the list, remove all instances of this operand from the expr.
1512 unsigned NumFound = 0;
1514 Ops.erase(Ops.begin()+i);
1516 } while (i != Ops.size() && Ops[i].Op == TheOp);
1518 DEBUG(dbgs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n');
1521 // Insert a new multiply.
1522 Type *Ty = TheOp->getType();
1523 Constant *C = Ty->isIntegerTy() ? ConstantInt::get(Ty, NumFound)
1524 : ConstantFP::get(Ty, NumFound);
1525 Instruction *Mul = CreateMul(TheOp, C, "factor", I, I);
1527 // Now that we have inserted a multiply, optimize it. This allows us to
1528 // handle cases that require multiple factoring steps, such as this:
1529 // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
1530 RedoInsts.insert(Mul);
1532 // If every add operand was a duplicate, return the multiply.
1536 // Otherwise, we had some input that didn't have the dupe, such as
1537 // "A + A + B" -> "A*2 + B". Add the new multiply to the list of
1538 // things being added by this operation.
1539 Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
1546 // Check for X and -X or X and ~X in the operand list.
1547 if (!BinaryOperator::isNeg(TheOp) && !BinaryOperator::isFNeg(TheOp) &&
1548 !BinaryOperator::isNot(TheOp))
1552 if (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp))
1553 X = BinaryOperator::getNegArgument(TheOp);
1554 else if (BinaryOperator::isNot(TheOp))
1555 X = BinaryOperator::getNotArgument(TheOp);
1557 unsigned FoundX = FindInOperandList(Ops, i, X);
1561 // Remove X and -X from the operand list.
1562 if (Ops.size() == 2 &&
1563 (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp)))
1564 return Constant::getNullValue(X->getType());
1566 // Remove X and ~X from the operand list.
1567 if (Ops.size() == 2 && BinaryOperator::isNot(TheOp))
1568 return Constant::getAllOnesValue(X->getType());
1570 Ops.erase(Ops.begin()+i);
1574 --i; // Need to back up an extra one.
1575 Ops.erase(Ops.begin()+FoundX);
1577 --i; // Revisit element.
1578 e -= 2; // Removed two elements.
1580 // if X and ~X we append -1 to the operand list.
1581 if (BinaryOperator::isNot(TheOp)) {
1582 Value *V = Constant::getAllOnesValue(X->getType());
1583 Ops.insert(Ops.end(), ValueEntry(getRank(V), V));
1588 // Scan the operand list, checking to see if there are any common factors
1589 // between operands. Consider something like A*A+A*B*C+D. We would like to
1590 // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
1591 // To efficiently find this, we count the number of times a factor occurs
1592 // for any ADD operands that are MULs.
1593 DenseMap<Value*, unsigned> FactorOccurrences;
1595 // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
1596 // where they are actually the same multiply.
1597 unsigned MaxOcc = 0;
1598 Value *MaxOccVal = nullptr;
1599 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1600 BinaryOperator *BOp =
1601 isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1605 // Compute all of the factors of this added value.
1606 SmallVector<Value*, 8> Factors;
1607 FindSingleUseMultiplyFactors(BOp, Factors, Ops);
1608 assert(Factors.size() > 1 && "Bad linearize!");
1610 // Add one to FactorOccurrences for each unique factor in this op.
1611 SmallPtrSet<Value*, 8> Duplicates;
1612 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1613 Value *Factor = Factors[i];
1614 if (!Duplicates.insert(Factor).second)
1617 unsigned Occ = ++FactorOccurrences[Factor];
1623 // If Factor is a negative constant, add the negated value as a factor
1624 // because we can percolate the negate out. Watch for minint, which
1625 // cannot be positivified.
1626 if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor)) {
1627 if (CI->isNegative() && !CI->isMinValue(true)) {
1628 Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
1629 assert(!Duplicates.count(Factor) &&
1630 "Shouldn't have two constant factors, missed a canonicalize");
1631 unsigned Occ = ++FactorOccurrences[Factor];
1637 } else if (ConstantFP *CF = dyn_cast<ConstantFP>(Factor)) {
1638 if (CF->isNegative()) {
1639 APFloat F(CF->getValueAPF());
1641 Factor = ConstantFP::get(CF->getContext(), F);
1642 assert(!Duplicates.count(Factor) &&
1643 "Shouldn't have two constant factors, missed a canonicalize");
1644 unsigned Occ = ++FactorOccurrences[Factor];
1654 // If any factor occurred more than one time, we can pull it out.
1656 DEBUG(dbgs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
1659 // Create a new instruction that uses the MaxOccVal twice. If we don't do
1660 // this, we could otherwise run into situations where removing a factor
1661 // from an expression will drop a use of maxocc, and this can cause
1662 // RemoveFactorFromExpression on successive values to behave differently.
1663 Instruction *DummyInst =
1664 I->getType()->isIntegerTy()
1665 ? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal)
1666 : BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal);
1668 SmallVector<WeakVH, 4> NewMulOps;
1669 for (unsigned i = 0; i != Ops.size(); ++i) {
1670 // Only try to remove factors from expressions we're allowed to.
1671 BinaryOperator *BOp =
1672 isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1676 if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
1677 // The factorized operand may occur several times. Convert them all in
1679 for (unsigned j = Ops.size(); j != i;) {
1681 if (Ops[j].Op == Ops[i].Op) {
1682 NewMulOps.push_back(V);
1683 Ops.erase(Ops.begin()+j);
1690 // No need for extra uses anymore.
1693 unsigned NumAddedValues = NewMulOps.size();
1694 Value *V = EmitAddTreeOfValues(I, NewMulOps);
1696 // Now that we have inserted the add tree, optimize it. This allows us to
1697 // handle cases that require multiple factoring steps, such as this:
1698 // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
1699 assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
1700 (void)NumAddedValues;
1701 if (Instruction *VI = dyn_cast<Instruction>(V))
1702 RedoInsts.insert(VI);
1704 // Create the multiply.
1705 Instruction *V2 = CreateMul(V, MaxOccVal, "tmp", I, I);
1707 // Rerun associate on the multiply in case the inner expression turned into
1708 // a multiply. We want to make sure that we keep things in canonical form.
1709 RedoInsts.insert(V2);
1711 // If every add operand included the factor (e.g. "A*B + A*C"), then the
1712 // entire result expression is just the multiply "A*(B+C)".
1716 // Otherwise, we had some input that didn't have the factor, such as
1717 // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
1718 // things being added by this operation.
1719 Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
1725 /// \brief Build up a vector of value/power pairs factoring a product.
1727 /// Given a series of multiplication operands, build a vector of factors and
1728 /// the powers each is raised to when forming the final product. Sort them in
1729 /// the order of descending power.
1731 /// (x*x) -> [(x, 2)]
1732 /// ((x*x)*x) -> [(x, 3)]
1733 /// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
1735 /// \returns Whether any factors have a power greater than one.
1736 bool Reassociate::collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
1737 SmallVectorImpl<Factor> &Factors) {
1738 // FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this.
1739 // Compute the sum of powers of simplifiable factors.
1740 unsigned FactorPowerSum = 0;
1741 for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) {
1742 Value *Op = Ops[Idx-1].Op;
1744 // Count the number of occurrences of this value.
1746 for (; Idx < Size && Ops[Idx].Op == Op; ++Idx)
1748 // Track for simplification all factors which occur 2 or more times.
1750 FactorPowerSum += Count;
1753 // We can only simplify factors if the sum of the powers of our simplifiable
1754 // factors is 4 or higher. When that is the case, we will *always* have
1755 // a simplification. This is an important invariant to prevent cyclicly
1756 // trying to simplify already minimal formations.
1757 if (FactorPowerSum < 4)
1760 // Now gather the simplifiable factors, removing them from Ops.
1762 for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) {
1763 Value *Op = Ops[Idx-1].Op;
1765 // Count the number of occurrences of this value.
1767 for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx)
1771 // Move an even number of occurrences to Factors.
1774 FactorPowerSum += Count;
1775 Factors.push_back(Factor(Op, Count));
1776 Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count);
1779 // None of the adjustments above should have reduced the sum of factor powers
1780 // below our mininum of '4'.
1781 assert(FactorPowerSum >= 4);
1783 std::stable_sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter());
1787 /// \brief Build a tree of multiplies, computing the product of Ops.
1788 static Value *buildMultiplyTree(IRBuilder<> &Builder,
1789 SmallVectorImpl<Value*> &Ops) {
1790 if (Ops.size() == 1)
1793 Value *LHS = Ops.pop_back_val();
1795 if (LHS->getType()->isIntegerTy())
1796 LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
1798 LHS = Builder.CreateFMul(LHS, Ops.pop_back_val());
1799 } while (!Ops.empty());
1804 /// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
1806 /// Given a vector of values raised to various powers, where no two values are
1807 /// equal and the powers are sorted in decreasing order, compute the minimal
1808 /// DAG of multiplies to compute the final product, and return that product
1810 Value *Reassociate::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
1811 SmallVectorImpl<Factor> &Factors) {
1812 assert(Factors[0].Power);
1813 SmallVector<Value *, 4> OuterProduct;
1814 for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
1815 Idx < Size && Factors[Idx].Power > 0; ++Idx) {
1816 if (Factors[Idx].Power != Factors[LastIdx].Power) {
1821 // We want to multiply across all the factors with the same power so that
1822 // we can raise them to that power as a single entity. Build a mini tree
1824 SmallVector<Value *, 4> InnerProduct;
1825 InnerProduct.push_back(Factors[LastIdx].Base);
1827 InnerProduct.push_back(Factors[Idx].Base);
1829 } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
1831 // Reset the base value of the first factor to the new expression tree.
1832 // We'll remove all the factors with the same power in a second pass.
1833 Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
1834 if (Instruction *MI = dyn_cast<Instruction>(M))
1835 RedoInsts.insert(MI);
1839 // Unique factors with equal powers -- we've folded them into the first one's
1841 Factors.erase(std::unique(Factors.begin(), Factors.end(),
1842 Factor::PowerEqual()),
1845 // Iteratively collect the base of each factor with an add power into the
1846 // outer product, and halve each power in preparation for squaring the
1848 for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
1849 if (Factors[Idx].Power & 1)
1850 OuterProduct.push_back(Factors[Idx].Base);
1851 Factors[Idx].Power >>= 1;
1853 if (Factors[0].Power) {
1854 Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
1855 OuterProduct.push_back(SquareRoot);
1856 OuterProduct.push_back(SquareRoot);
1858 if (OuterProduct.size() == 1)
1859 return OuterProduct.front();
1861 Value *V = buildMultiplyTree(Builder, OuterProduct);
1865 Value *Reassociate::OptimizeMul(BinaryOperator *I,
1866 SmallVectorImpl<ValueEntry> &Ops) {
1867 // We can only optimize the multiplies when there is a chain of more than
1868 // three, such that a balanced tree might require fewer total multiplies.
1872 // Try to turn linear trees of multiplies without other uses of the
1873 // intermediate stages into minimal multiply DAGs with perfect sub-expression
1875 SmallVector<Factor, 4> Factors;
1876 if (!collectMultiplyFactors(Ops, Factors))
1877 return nullptr; // All distinct factors, so nothing left for us to do.
1879 IRBuilder<> Builder(I);
1880 Value *V = buildMinimalMultiplyDAG(Builder, Factors);
1884 ValueEntry NewEntry = ValueEntry(getRank(V), V);
1885 Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry);
1889 Value *Reassociate::OptimizeExpression(BinaryOperator *I,
1890 SmallVectorImpl<ValueEntry> &Ops) {
1891 // Now that we have the linearized expression tree, try to optimize it.
1892 // Start by folding any constants that we found.
1893 Constant *Cst = nullptr;
1894 unsigned Opcode = I->getOpcode();
1895 while (!Ops.empty() && isa<Constant>(Ops.back().Op)) {
1896 Constant *C = cast<Constant>(Ops.pop_back_val().Op);
1897 Cst = Cst ? ConstantExpr::get(Opcode, C, Cst) : C;
1899 // If there was nothing but constants then we are done.
1903 // Put the combined constant back at the end of the operand list, except if
1904 // there is no point. For example, an add of 0 gets dropped here, while a
1905 // multiplication by zero turns the whole expression into zero.
1906 if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) {
1907 if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType()))
1909 Ops.push_back(ValueEntry(0, Cst));
1912 if (Ops.size() == 1) return Ops[0].Op;
1914 // Handle destructive annihilation due to identities between elements in the
1915 // argument list here.
1916 unsigned NumOps = Ops.size();
1919 case Instruction::And:
1920 case Instruction::Or:
1921 if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
1925 case Instruction::Xor:
1926 if (Value *Result = OptimizeXor(I, Ops))
1930 case Instruction::Add:
1931 case Instruction::FAdd:
1932 if (Value *Result = OptimizeAdd(I, Ops))
1936 case Instruction::Mul:
1937 case Instruction::FMul:
1938 if (Value *Result = OptimizeMul(I, Ops))
1943 if (Ops.size() != NumOps)
1944 return OptimizeExpression(I, Ops);
1948 /// EraseInst - Zap the given instruction, adding interesting operands to the
1950 void Reassociate::EraseInst(Instruction *I) {
1951 assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
1952 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
1953 // Erase the dead instruction.
1954 ValueRankMap.erase(I);
1955 RedoInsts.remove(I);
1956 I->eraseFromParent();
1957 // Optimize its operands.
1958 SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
1959 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1960 if (Instruction *Op = dyn_cast<Instruction>(Ops[i])) {
1961 // If this is a node in an expression tree, climb to the expression root
1962 // and add that since that's where optimization actually happens.
1963 unsigned Opcode = Op->getOpcode();
1964 while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode &&
1965 Visited.insert(Op).second)
1966 Op = Op->user_back();
1967 RedoInsts.insert(Op);
1971 // Canonicalize expressions of the following form:
1972 // x + (-Constant * y) -> x - (Constant * y)
1973 // x - (-Constant * y) -> x + (Constant * y)
1974 Instruction *Reassociate::canonicalizeNegConstExpr(Instruction *I) {
1975 if (!I->hasOneUse() || I->getType()->isVectorTy())
1978 // Must be a mul, fmul, or fdiv instruction.
1979 unsigned Opcode = I->getOpcode();
1980 if (Opcode != Instruction::Mul && Opcode != Instruction::FMul &&
1981 Opcode != Instruction::FDiv)
1984 // Must have at least one constant operand.
1985 Constant *C0 = dyn_cast<Constant>(I->getOperand(0));
1986 Constant *C1 = dyn_cast<Constant>(I->getOperand(1));
1990 // Must be a negative ConstantInt or ConstantFP.
1991 Constant *C = C0 ? C0 : C1;
1992 unsigned ConstIdx = C0 ? 0 : 1;
1993 if (auto *CI = dyn_cast<ConstantInt>(C)) {
1994 if (!CI->isNegative())
1996 } else if (auto *CF = dyn_cast<ConstantFP>(C)) {
1997 if (!CF->isNegative())
2002 // User must be a binary operator with one or more uses.
2003 Instruction *User = I->user_back();
2004 if (!isa<BinaryOperator>(User) || !User->getNumUses())
2007 unsigned UserOpcode = User->getOpcode();
2008 if (UserOpcode != Instruction::Add && UserOpcode != Instruction::FAdd &&
2009 UserOpcode != Instruction::Sub && UserOpcode != Instruction::FSub)
2012 // Subtraction is not commutative. Explicitly, the following transform is
2013 // not valid: (-Constant * y) - x -> x + (Constant * y)
2014 if (!User->isCommutative() && User->getOperand(1) != I)
2017 // Change the sign of the constant.
2018 if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
2019 I->setOperand(ConstIdx, ConstantInt::get(CI->getContext(), -CI->getValue()));
2021 ConstantFP *CF = cast<ConstantFP>(C);
2022 APFloat Val = CF->getValueAPF();
2024 I->setOperand(ConstIdx, ConstantFP::get(CF->getContext(), Val));
2027 // Canonicalize I to RHS to simplify the next bit of logic. E.g.,
2028 // ((-Const*y) + x) -> (x + (-Const*y)).
2029 if (User->getOperand(0) == I && User->isCommutative())
2030 cast<BinaryOperator>(User)->swapOperands();
2032 Value *Op0 = User->getOperand(0);
2033 Value *Op1 = User->getOperand(1);
2035 switch(UserOpcode) {
2037 llvm_unreachable("Unexpected Opcode!");
2038 case Instruction::Add:
2039 NI = BinaryOperator::CreateSub(Op0, Op1);
2041 case Instruction::Sub:
2042 NI = BinaryOperator::CreateAdd(Op0, Op1);
2044 case Instruction::FAdd:
2045 NI = BinaryOperator::CreateFSub(Op0, Op1);
2046 NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
2048 case Instruction::FSub:
2049 NI = BinaryOperator::CreateFAdd(Op0, Op1);
2050 NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
2054 NI->insertBefore(User);
2055 NI->setName(User->getName());
2056 User->replaceAllUsesWith(NI);
2057 NI->setDebugLoc(I->getDebugLoc());
2058 RedoInsts.insert(I);
2063 /// OptimizeInst - Inspect and optimize the given instruction. Note that erasing
2064 /// instructions is not allowed.
2065 void Reassociate::OptimizeInst(Instruction *I) {
2066 // Only consider operations that we understand.
2067 if (!isa<BinaryOperator>(I))
2070 if (I->getOpcode() == Instruction::Shl && isa<ConstantInt>(I->getOperand(1)))
2071 // If an operand of this shift is a reassociable multiply, or if the shift
2072 // is used by a reassociable multiply or add, turn into a multiply.
2073 if (isReassociableOp(I->getOperand(0), Instruction::Mul) ||
2075 (isReassociableOp(I->user_back(), Instruction::Mul) ||
2076 isReassociableOp(I->user_back(), Instruction::Add)))) {
2077 Instruction *NI = ConvertShiftToMul(I);
2078 RedoInsts.insert(I);
2083 // Canonicalize negative constants out of expressions.
2084 if (Instruction *Res = canonicalizeNegConstExpr(I))
2087 // Commute binary operators, to canonicalize the order of their operands.
2088 // This can potentially expose more CSE opportunities, and makes writing other
2089 // transformations simpler.
2090 if (I->isCommutative())
2091 canonicalizeOperands(I);
2093 // Don't optimize vector instructions.
2094 if (I->getType()->isVectorTy())
2097 // Don't optimize floating point instructions that don't have unsafe algebra.
2098 if (I->getType()->isFloatingPointTy() && !I->hasUnsafeAlgebra())
2101 // Do not reassociate boolean (i1) expressions. We want to preserve the
2102 // original order of evaluation for short-circuited comparisons that
2103 // SimplifyCFG has folded to AND/OR expressions. If the expression
2104 // is not further optimized, it is likely to be transformed back to a
2105 // short-circuited form for code gen, and the source order may have been
2106 // optimized for the most likely conditions.
2107 if (I->getType()->isIntegerTy(1))
2110 // If this is a subtract instruction which is not already in negate form,
2111 // see if we can convert it to X+-Y.
2112 if (I->getOpcode() == Instruction::Sub) {
2113 if (ShouldBreakUpSubtract(I)) {
2114 Instruction *NI = BreakUpSubtract(I);
2115 RedoInsts.insert(I);
2118 } else if (BinaryOperator::isNeg(I)) {
2119 // Otherwise, this is a negation. See if the operand is a multiply tree
2120 // and if this is not an inner node of a multiply tree.
2121 if (isReassociableOp(I->getOperand(1), Instruction::Mul) &&
2123 !isReassociableOp(I->user_back(), Instruction::Mul))) {
2124 Instruction *NI = LowerNegateToMultiply(I);
2125 RedoInsts.insert(I);
2130 } else if (I->getOpcode() == Instruction::FSub) {
2131 if (ShouldBreakUpSubtract(I)) {
2132 Instruction *NI = BreakUpSubtract(I);
2133 RedoInsts.insert(I);
2136 } else if (BinaryOperator::isFNeg(I)) {
2137 // Otherwise, this is a negation. See if the operand is a multiply tree
2138 // and if this is not an inner node of a multiply tree.
2139 if (isReassociableOp(I->getOperand(1), Instruction::FMul) &&
2141 !isReassociableOp(I->user_back(), Instruction::FMul))) {
2142 Instruction *NI = LowerNegateToMultiply(I);
2143 RedoInsts.insert(I);
2150 // If this instruction is an associative binary operator, process it.
2151 if (!I->isAssociative()) return;
2152 BinaryOperator *BO = cast<BinaryOperator>(I);
2154 // If this is an interior node of a reassociable tree, ignore it until we
2155 // get to the root of the tree, to avoid N^2 analysis.
2156 unsigned Opcode = BO->getOpcode();
2157 if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode)
2160 // If this is an add tree that is used by a sub instruction, ignore it
2161 // until we process the subtract.
2162 if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
2163 cast<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub)
2165 if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd &&
2166 cast<Instruction>(BO->user_back())->getOpcode() == Instruction::FSub)
2169 ReassociateExpression(BO);
2172 void Reassociate::ReassociateExpression(BinaryOperator *I) {
2173 assert(!I->getType()->isVectorTy() &&
2174 "Reassociation of vector instructions is not supported.");
2176 // First, walk the expression tree, linearizing the tree, collecting the
2177 // operand information.
2178 SmallVector<RepeatedValue, 8> Tree;
2179 MadeChange |= LinearizeExprTree(I, Tree);
2180 SmallVector<ValueEntry, 8> Ops;
2181 Ops.reserve(Tree.size());
2182 for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
2183 RepeatedValue E = Tree[i];
2184 Ops.append(E.second.getZExtValue(),
2185 ValueEntry(getRank(E.first), E.first));
2188 DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
2190 // Now that we have linearized the tree to a list and have gathered all of
2191 // the operands and their ranks, sort the operands by their rank. Use a
2192 // stable_sort so that values with equal ranks will have their relative
2193 // positions maintained (and so the compiler is deterministic). Note that
2194 // this sorts so that the highest ranking values end up at the beginning of
2196 std::stable_sort(Ops.begin(), Ops.end());
2198 // OptimizeExpression - Now that we have the expression tree in a convenient
2199 // sorted form, optimize it globally if possible.
2200 if (Value *V = OptimizeExpression(I, Ops)) {
2202 // Self-referential expression in unreachable code.
2204 // This expression tree simplified to something that isn't a tree,
2206 DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
2207 I->replaceAllUsesWith(V);
2208 if (Instruction *VI = dyn_cast<Instruction>(V))
2209 VI->setDebugLoc(I->getDebugLoc());
2210 RedoInsts.insert(I);
2215 // We want to sink immediates as deeply as possible except in the case where
2216 // this is a multiply tree used only by an add, and the immediate is a -1.
2217 // In this case we reassociate to put the negation on the outside so that we
2218 // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
2219 if (I->hasOneUse()) {
2220 if (I->getOpcode() == Instruction::Mul &&
2221 cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
2222 isa<ConstantInt>(Ops.back().Op) &&
2223 cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
2224 ValueEntry Tmp = Ops.pop_back_val();
2225 Ops.insert(Ops.begin(), Tmp);
2226 } else if (I->getOpcode() == Instruction::FMul &&
2227 cast<Instruction>(I->user_back())->getOpcode() ==
2228 Instruction::FAdd &&
2229 isa<ConstantFP>(Ops.back().Op) &&
2230 cast<ConstantFP>(Ops.back().Op)->isExactlyValue(-1.0)) {
2231 ValueEntry Tmp = Ops.pop_back_val();
2232 Ops.insert(Ops.begin(), Tmp);
2236 DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
2238 if (Ops.size() == 1) {
2240 // Self-referential expression in unreachable code.
2243 // This expression tree simplified to something that isn't a tree,
2245 I->replaceAllUsesWith(Ops[0].Op);
2246 if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
2247 OI->setDebugLoc(I->getDebugLoc());
2248 RedoInsts.insert(I);
2252 // Now that we ordered and optimized the expressions, splat them back into
2253 // the expression tree, removing any unneeded nodes.
2254 RewriteExprTree(I, Ops);
2257 bool Reassociate::runOnFunction(Function &F) {
2258 if (skipOptnoneFunction(F))
2261 // Calculate the rank map for F
2265 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
2266 // Optimize every instruction in the basic block.
2267 for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE; )
2268 if (isInstructionTriviallyDead(II)) {
2272 assert(II->getParent() == BI && "Moved to a different block!");
2276 // If this produced extra instructions to optimize, handle them now.
2277 while (!RedoInsts.empty()) {
2278 Instruction *I = RedoInsts.pop_back_val();
2279 if (isInstructionTriviallyDead(I))
2286 // We are done with the rank map.
2288 ValueRankMap.clear();