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/Analysis/GlobalsModRef.h"
30 #include "llvm/Analysis/ValueTracking.h"
31 #include "llvm/IR/CFG.h"
32 #include "llvm/IR/Constants.h"
33 #include "llvm/IR/DerivedTypes.h"
34 #include "llvm/IR/Function.h"
35 #include "llvm/IR/IRBuilder.h"
36 #include "llvm/IR/Instructions.h"
37 #include "llvm/IR/IntrinsicInst.h"
38 #include "llvm/IR/ValueHandle.h"
39 #include "llvm/Pass.h"
40 #include "llvm/Support/Debug.h"
41 #include "llvm/Support/raw_ostream.h"
42 #include "llvm/Transforms/Utils/Local.h"
46 #define DEBUG_TYPE "reassociate"
48 STATISTIC(NumChanged, "Number of insts reassociated");
49 STATISTIC(NumAnnihil, "Number of expr tree annihilated");
50 STATISTIC(NumFactor , "Number of multiplies factored");
56 ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {}
58 inline bool operator<(const ValueEntry &LHS, const ValueEntry &RHS) {
59 return LHS.Rank > RHS.Rank; // Sort so that highest rank goes to start.
64 /// Print out the expression identified in the Ops list.
66 static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
67 Module *M = I->getModule();
68 dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
69 << *Ops[0].Op->getType() << '\t';
70 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
72 Ops[i].Op->printAsOperand(dbgs(), false, M);
73 dbgs() << ", #" << Ops[i].Rank << "] ";
79 /// \brief Utility class representing a base and exponent pair which form one
80 /// factor of some product.
85 Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {}
87 /// \brief Sort factors in descending order by their power.
88 struct PowerDescendingSorter {
89 bool operator()(const Factor &LHS, const Factor &RHS) {
90 return LHS.Power > RHS.Power;
94 /// \brief Compare factors for equal powers.
96 bool operator()(const Factor &LHS, const Factor &RHS) {
97 return LHS.Power == RHS.Power;
102 /// Utility class representing a non-constant Xor-operand. We classify
103 /// non-constant Xor-Operands into two categories:
104 /// C1) The operand is in the form "X & C", where C is a constant and C != ~0
106 /// C2.1) The operand is in the form of "X | C", where C is a non-zero
108 /// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
109 /// operand as "E | 0"
114 bool isInvalid() const { return SymbolicPart == nullptr; }
115 bool isOrExpr() const { return isOr; }
116 Value *getValue() const { return OrigVal; }
117 Value *getSymbolicPart() const { return SymbolicPart; }
118 unsigned getSymbolicRank() const { return SymbolicRank; }
119 const APInt &getConstPart() const { return ConstPart; }
121 void Invalidate() { SymbolicPart = OrigVal = nullptr; }
122 void setSymbolicRank(unsigned R) { SymbolicRank = R; }
124 // Sort the XorOpnd-Pointer in ascending order of symbolic-value-rank.
125 // The purpose is twofold:
126 // 1) Cluster together the operands sharing the same symbolic-value.
127 // 2) Operand having smaller symbolic-value-rank is permuted earlier, which
128 // could potentially shorten crital path, and expose more loop-invariants.
129 // Note that values' rank are basically defined in RPO order (FIXME).
130 // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
131 // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
132 // "z" in the order of X-Y-Z is better than any other orders.
133 struct PtrSortFunctor {
134 bool operator()(XorOpnd * const &LHS, XorOpnd * const &RHS) {
135 return LHS->getSymbolicRank() < RHS->getSymbolicRank();
142 unsigned SymbolicRank;
148 class Reassociate : public FunctionPass {
149 DenseMap<BasicBlock*, unsigned> RankMap;
150 DenseMap<AssertingVH<Value>, unsigned> ValueRankMap;
151 SetVector<AssertingVH<Instruction> > RedoInsts;
154 static char ID; // Pass identification, replacement for typeid
155 Reassociate() : FunctionPass(ID) {
156 initializeReassociatePass(*PassRegistry::getPassRegistry());
159 bool runOnFunction(Function &F) override;
161 void getAnalysisUsage(AnalysisUsage &AU) const override {
162 AU.setPreservesCFG();
163 AU.addPreserved<GlobalsAAWrapperPass>();
166 void BuildRankMap(Function &F);
167 unsigned getRank(Value *V);
168 void canonicalizeOperands(Instruction *I);
169 void ReassociateExpression(BinaryOperator *I);
170 void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
171 Value *OptimizeExpression(BinaryOperator *I,
172 SmallVectorImpl<ValueEntry> &Ops);
173 Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
174 Value *OptimizeXor(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
175 bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, APInt &ConstOpnd,
177 bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
178 APInt &ConstOpnd, Value *&Res);
179 bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
180 SmallVectorImpl<Factor> &Factors);
181 Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
182 SmallVectorImpl<Factor> &Factors);
183 Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
184 Value *RemoveFactorFromExpression(Value *V, Value *Factor);
185 void EraseInst(Instruction *I);
186 void RecursivelyEraseDeadInsts(Instruction *I,
187 SetVector<AssertingVH<Instruction>> &Insts);
188 void OptimizeInst(Instruction *I);
189 Instruction *canonicalizeNegConstExpr(Instruction *I);
193 XorOpnd::XorOpnd(Value *V) {
194 assert(!isa<ConstantInt>(V) && "No ConstantInt");
196 Instruction *I = dyn_cast<Instruction>(V);
199 if (I && (I->getOpcode() == Instruction::Or ||
200 I->getOpcode() == Instruction::And)) {
201 Value *V0 = I->getOperand(0);
202 Value *V1 = I->getOperand(1);
203 if (isa<ConstantInt>(V0))
206 if (ConstantInt *C = dyn_cast<ConstantInt>(V1)) {
207 ConstPart = C->getValue();
209 isOr = (I->getOpcode() == Instruction::Or);
214 // view the operand as "V | 0"
216 ConstPart = APInt::getNullValue(V->getType()->getIntegerBitWidth());
220 char Reassociate::ID = 0;
221 INITIALIZE_PASS(Reassociate, "reassociate",
222 "Reassociate expressions", false, false)
224 // Public interface to the Reassociate pass
225 FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
227 /// Return true if V is an instruction of the specified opcode and if it
228 /// only has one use.
229 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
230 if (V->hasOneUse() && isa<Instruction>(V) &&
231 cast<Instruction>(V)->getOpcode() == Opcode &&
232 (!isa<FPMathOperator>(V) ||
233 cast<Instruction>(V)->hasUnsafeAlgebra()))
234 return cast<BinaryOperator>(V);
238 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1,
240 if (V->hasOneUse() && isa<Instruction>(V) &&
241 (cast<Instruction>(V)->getOpcode() == Opcode1 ||
242 cast<Instruction>(V)->getOpcode() == Opcode2) &&
243 (!isa<FPMathOperator>(V) ||
244 cast<Instruction>(V)->hasUnsafeAlgebra()))
245 return cast<BinaryOperator>(V);
249 void Reassociate::BuildRankMap(Function &F) {
252 // Assign distinct ranks to function arguments.
253 for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I) {
254 ValueRankMap[&*I] = ++i;
255 DEBUG(dbgs() << "Calculated Rank[" << I->getName() << "] = " << i << "\n");
258 ReversePostOrderTraversal<Function*> RPOT(&F);
259 for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
260 E = RPOT.end(); I != E; ++I) {
262 unsigned BBRank = RankMap[BB] = ++i << 16;
264 // Walk the basic block, adding precomputed ranks for any instructions that
265 // we cannot move. This ensures that the ranks for these instructions are
266 // all different in the block.
267 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
268 if (mayBeMemoryDependent(*I))
269 ValueRankMap[&*I] = ++BBRank;
273 unsigned Reassociate::getRank(Value *V) {
274 Instruction *I = dyn_cast<Instruction>(V);
276 if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
277 return 0; // Otherwise it's a global or constant, rank 0.
280 if (unsigned Rank = ValueRankMap[I])
281 return Rank; // Rank already known?
283 // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
284 // we can reassociate expressions for code motion! Since we do not recurse
285 // for PHI nodes, we cannot have infinite recursion here, because there
286 // cannot be loops in the value graph that do not go through PHI nodes.
287 unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
288 for (unsigned i = 0, e = I->getNumOperands();
289 i != e && Rank != MaxRank; ++i)
290 Rank = std::max(Rank, getRank(I->getOperand(i)));
292 // If this is a not or neg instruction, do not count it for rank. This
293 // assures us that X and ~X will have the same rank.
294 if (!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I) &&
295 !BinaryOperator::isFNeg(I))
298 DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " << Rank << "\n");
300 return ValueRankMap[I] = Rank;
303 // Canonicalize constants to RHS. Otherwise, sort the operands by rank.
304 void Reassociate::canonicalizeOperands(Instruction *I) {
305 assert(isa<BinaryOperator>(I) && "Expected binary operator.");
306 assert(I->isCommutative() && "Expected commutative operator.");
308 Value *LHS = I->getOperand(0);
309 Value *RHS = I->getOperand(1);
310 unsigned LHSRank = getRank(LHS);
311 unsigned RHSRank = getRank(RHS);
313 if (isa<Constant>(RHS))
316 if (isa<Constant>(LHS) || RHSRank < LHSRank)
317 cast<BinaryOperator>(I)->swapOperands();
320 static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name,
321 Instruction *InsertBefore, Value *FlagsOp) {
322 if (S1->getType()->isIntOrIntVectorTy())
323 return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore);
325 BinaryOperator *Res =
326 BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore);
327 Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
332 static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name,
333 Instruction *InsertBefore, Value *FlagsOp) {
334 if (S1->getType()->isIntOrIntVectorTy())
335 return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore);
337 BinaryOperator *Res =
338 BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore);
339 Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
344 static BinaryOperator *CreateNeg(Value *S1, const Twine &Name,
345 Instruction *InsertBefore, Value *FlagsOp) {
346 if (S1->getType()->isIntOrIntVectorTy())
347 return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
349 BinaryOperator *Res = BinaryOperator::CreateFNeg(S1, Name, InsertBefore);
350 Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
355 /// Replace 0-X with X*-1.
356 static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) {
357 Type *Ty = Neg->getType();
358 Constant *NegOne = Ty->isIntOrIntVectorTy() ?
359 ConstantInt::getAllOnesValue(Ty) : ConstantFP::get(Ty, -1.0);
361 BinaryOperator *Res = CreateMul(Neg->getOperand(1), NegOne, "", Neg, Neg);
362 Neg->setOperand(1, Constant::getNullValue(Ty)); // Drop use of op.
364 Neg->replaceAllUsesWith(Res);
365 Res->setDebugLoc(Neg->getDebugLoc());
369 /// Returns k such that lambda(2^Bitwidth) = 2^k, where lambda is the Carmichael
370 /// function. This means that x^(2^k) === 1 mod 2^Bitwidth for
371 /// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic.
372 /// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every
373 /// even x in Bitwidth-bit arithmetic.
374 static unsigned CarmichaelShift(unsigned Bitwidth) {
380 /// Add the extra weight 'RHS' to the existing weight 'LHS',
381 /// reducing the combined weight using any special properties of the operation.
382 /// The existing weight LHS represents the computation X op X op ... op X where
383 /// X occurs LHS times. The combined weight represents X op X op ... op X with
384 /// X occurring LHS + RHS times. If op is "Xor" for example then the combined
385 /// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even;
386 /// the routine returns 1 in LHS in the first case, and 0 in LHS in the second.
387 static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) {
388 // If we were working with infinite precision arithmetic then the combined
389 // weight would be LHS + RHS. But we are using finite precision arithmetic,
390 // and the APInt sum LHS + RHS may not be correct if it wraps (it is correct
391 // for nilpotent operations and addition, but not for idempotent operations
392 // and multiplication), so it is important to correctly reduce the combined
393 // weight back into range if wrapping would be wrong.
395 // If RHS is zero then the weight didn't change.
396 if (RHS.isMinValue())
398 // If LHS is zero then the combined weight is RHS.
399 if (LHS.isMinValue()) {
403 // From this point on we know that neither LHS nor RHS is zero.
405 if (Instruction::isIdempotent(Opcode)) {
406 // Idempotent means X op X === X, so any non-zero weight is equivalent to a
407 // weight of 1. Keeping weights at zero or one also means that wrapping is
409 assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
410 return; // Return a weight of 1.
412 if (Instruction::isNilpotent(Opcode)) {
413 // Nilpotent means X op X === 0, so reduce weights modulo 2.
414 assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
415 LHS = 0; // 1 + 1 === 0 modulo 2.
418 if (Opcode == Instruction::Add || Opcode == Instruction::FAdd) {
419 // TODO: Reduce the weight by exploiting nsw/nuw?
424 assert((Opcode == Instruction::Mul || Opcode == Instruction::FMul) &&
425 "Unknown associative operation!");
426 unsigned Bitwidth = LHS.getBitWidth();
427 // If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth
428 // can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth
429 // bit number x, since either x is odd in which case x^CM = 1, or x is even in
430 // which case both x^W and x^(W - CM) are zero. By subtracting off multiples
431 // of CM like this weights can always be reduced to the range [0, CM+Bitwidth)
432 // which by a happy accident means that they can always be represented using
434 // TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than
435 // the Carmichael number).
437 /// CM - The value of Carmichael's lambda function.
438 APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth));
439 // Any weight W >= Threshold can be replaced with W - CM.
440 APInt Threshold = CM + Bitwidth;
441 assert(LHS.ult(Threshold) && RHS.ult(Threshold) && "Weights not reduced!");
442 // For Bitwidth 4 or more the following sum does not overflow.
444 while (LHS.uge(Threshold))
447 // To avoid problems with overflow do everything the same as above but using
449 unsigned CM = 1U << CarmichaelShift(Bitwidth);
450 unsigned Threshold = CM + Bitwidth;
451 assert(LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold &&
452 "Weights not reduced!");
453 unsigned Total = LHS.getZExtValue() + RHS.getZExtValue();
454 while (Total >= Threshold)
460 typedef std::pair<Value*, APInt> RepeatedValue;
462 /// Given an associative binary expression, return the leaf
463 /// nodes in Ops along with their weights (how many times the leaf occurs). The
464 /// original expression is the same as
465 /// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
467 /// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
471 /// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
473 /// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
475 /// This routine may modify the function, in which case it returns 'true'. The
476 /// changes it makes may well be destructive, changing the value computed by 'I'
477 /// to something completely different. Thus if the routine returns 'true' then
478 /// you MUST either replace I with a new expression computed from the Ops array,
479 /// or use RewriteExprTree to put the values back in.
481 /// A leaf node is either not a binary operation of the same kind as the root
482 /// node 'I' (i.e. is not a binary operator at all, or is, but with a different
483 /// opcode), or is the same kind of binary operator but has a use which either
484 /// does not belong to the expression, or does belong to the expression but is
485 /// a leaf node. Every leaf node has at least one use that is a non-leaf node
486 /// of the expression, while for non-leaf nodes (except for the root 'I') every
487 /// use is a non-leaf node of the expression.
490 /// expression graph node names
500 /// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
501 /// that order) (C, 1), (E, 1), (F, 2), (G, 2).
503 /// The expression is maximal: if some instruction is a binary operator of the
504 /// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
505 /// then the instruction also belongs to the expression, is not a leaf node of
506 /// it, and its operands also belong to the expression (but may be leaf nodes).
508 /// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
509 /// order to ensure that every non-root node in the expression has *exactly one*
510 /// use by a non-leaf node of the expression. This destruction means that the
511 /// caller MUST either replace 'I' with a new expression or use something like
512 /// RewriteExprTree to put the values back in if the routine indicates that it
513 /// made a change by returning 'true'.
515 /// In the above example either the right operand of A or the left operand of B
516 /// will be replaced by undef. If it is B's operand then this gives:
520 /// + + | A, B - operand of B replaced with undef
526 /// Note that such undef operands can only be reached by passing through 'I'.
527 /// For example, if you visit operands recursively starting from a leaf node
528 /// then you will never see such an undef operand unless you get back to 'I',
529 /// which requires passing through a phi node.
531 /// Note that this routine may also mutate binary operators of the wrong type
532 /// that have all uses inside the expression (i.e. only used by non-leaf nodes
533 /// of the expression) if it can turn them into binary operators of the right
534 /// type and thus make the expression bigger.
536 static bool LinearizeExprTree(BinaryOperator *I,
537 SmallVectorImpl<RepeatedValue> &Ops) {
538 DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
539 unsigned Bitwidth = I->getType()->getScalarType()->getPrimitiveSizeInBits();
540 unsigned Opcode = I->getOpcode();
541 assert(I->isAssociative() && I->isCommutative() &&
542 "Expected an associative and commutative operation!");
544 // Visit all operands of the expression, keeping track of their weight (the
545 // number of paths from the expression root to the operand, or if you like
546 // the number of times that operand occurs in the linearized expression).
547 // For example, if I = X + A, where X = A + B, then I, X and B have weight 1
548 // while A has weight two.
550 // Worklist of non-leaf nodes (their operands are in the expression too) along
551 // with their weights, representing a certain number of paths to the operator.
552 // If an operator occurs in the worklist multiple times then we found multiple
553 // ways to get to it.
554 SmallVector<std::pair<BinaryOperator*, APInt>, 8> Worklist; // (Op, Weight)
555 Worklist.push_back(std::make_pair(I, APInt(Bitwidth, 1)));
556 bool Changed = false;
558 // Leaves of the expression are values that either aren't the right kind of
559 // operation (eg: a constant, or a multiply in an add tree), or are, but have
560 // some uses that are not inside the expression. For example, in I = X + X,
561 // X = A + B, the value X has two uses (by I) that are in the expression. If
562 // X has any other uses, for example in a return instruction, then we consider
563 // X to be a leaf, and won't analyze it further. When we first visit a value,
564 // if it has more than one use then at first we conservatively consider it to
565 // be a leaf. Later, as the expression is explored, we may discover some more
566 // uses of the value from inside the expression. If all uses turn out to be
567 // from within the expression (and the value is a binary operator of the right
568 // kind) then the value is no longer considered to be a leaf, and its operands
571 // Leaves - Keeps track of the set of putative leaves as well as the number of
572 // paths to each leaf seen so far.
573 typedef DenseMap<Value*, APInt> LeafMap;
574 LeafMap Leaves; // Leaf -> Total weight so far.
575 SmallVector<Value*, 8> LeafOrder; // Ensure deterministic leaf output order.
578 SmallPtrSet<Value*, 8> Visited; // For sanity checking the iteration scheme.
580 while (!Worklist.empty()) {
581 std::pair<BinaryOperator*, APInt> P = Worklist.pop_back_val();
582 I = P.first; // We examine the operands of this binary operator.
584 for (unsigned OpIdx = 0; OpIdx < 2; ++OpIdx) { // Visit operands.
585 Value *Op = I->getOperand(OpIdx);
586 APInt Weight = P.second; // Number of paths to this operand.
587 DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n");
588 assert(!Op->use_empty() && "No uses, so how did we get to it?!");
590 // If this is a binary operation of the right kind with only one use then
591 // add its operands to the expression.
592 if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
593 assert(Visited.insert(Op).second && "Not first visit!");
594 DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n");
595 Worklist.push_back(std::make_pair(BO, Weight));
599 // Appears to be a leaf. Is the operand already in the set of leaves?
600 LeafMap::iterator It = Leaves.find(Op);
601 if (It == Leaves.end()) {
602 // Not in the leaf map. Must be the first time we saw this operand.
603 assert(Visited.insert(Op).second && "Not first visit!");
604 if (!Op->hasOneUse()) {
605 // This value has uses not accounted for by the expression, so it is
606 // not safe to modify. Mark it as being a leaf.
607 DEBUG(dbgs() << "ADD USES LEAF: " << *Op << " (" << Weight << ")\n");
608 LeafOrder.push_back(Op);
612 // No uses outside the expression, try morphing it.
613 } else if (It != Leaves.end()) {
614 // Already in the leaf map.
615 assert(Visited.count(Op) && "In leaf map but not visited!");
617 // Update the number of paths to the leaf.
618 IncorporateWeight(It->second, Weight, Opcode);
620 #if 0 // TODO: Re-enable once PR13021 is fixed.
621 // The leaf already has one use from inside the expression. As we want
622 // exactly one such use, drop this new use of the leaf.
623 assert(!Op->hasOneUse() && "Only one use, but we got here twice!");
624 I->setOperand(OpIdx, UndefValue::get(I->getType()));
627 // If the leaf is a binary operation of the right kind and we now see
628 // that its multiple original uses were in fact all by nodes belonging
629 // to the expression, then no longer consider it to be a leaf and add
630 // its operands to the expression.
631 if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
632 DEBUG(dbgs() << "UNLEAF: " << *Op << " (" << It->second << ")\n");
633 Worklist.push_back(std::make_pair(BO, It->second));
639 // If we still have uses that are not accounted for by the expression
640 // then it is not safe to modify the value.
641 if (!Op->hasOneUse())
644 // No uses outside the expression, try morphing it.
646 Leaves.erase(It); // Since the value may be morphed below.
649 // At this point we have a value which, first of all, is not a binary
650 // expression of the right kind, and secondly, is only used inside the
651 // expression. This means that it can safely be modified. See if we
652 // can usefully morph it into an expression of the right kind.
653 assert((!isa<Instruction>(Op) ||
654 cast<Instruction>(Op)->getOpcode() != Opcode
655 || (isa<FPMathOperator>(Op) &&
656 !cast<Instruction>(Op)->hasUnsafeAlgebra())) &&
657 "Should have been handled above!");
658 assert(Op->hasOneUse() && "Has uses outside the expression tree!");
660 // If this is a multiply expression, turn any internal negations into
661 // multiplies by -1 so they can be reassociated.
662 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op))
663 if ((Opcode == Instruction::Mul && BinaryOperator::isNeg(BO)) ||
664 (Opcode == Instruction::FMul && BinaryOperator::isFNeg(BO))) {
665 DEBUG(dbgs() << "MORPH LEAF: " << *Op << " (" << Weight << ") TO ");
666 BO = LowerNegateToMultiply(BO);
667 DEBUG(dbgs() << *BO << '\n');
668 Worklist.push_back(std::make_pair(BO, Weight));
673 // Failed to morph into an expression of the right type. This really is
675 DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n");
676 assert(!isReassociableOp(Op, Opcode) && "Value was morphed?");
677 LeafOrder.push_back(Op);
682 // The leaves, repeated according to their weights, represent the linearized
683 // form of the expression.
684 for (unsigned i = 0, e = LeafOrder.size(); i != e; ++i) {
685 Value *V = LeafOrder[i];
686 LeafMap::iterator It = Leaves.find(V);
687 if (It == Leaves.end())
688 // Node initially thought to be a leaf wasn't.
690 assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!");
691 APInt Weight = It->second;
692 if (Weight.isMinValue())
693 // Leaf already output or weight reduction eliminated it.
695 // Ensure the leaf is only output once.
697 Ops.push_back(std::make_pair(V, Weight));
700 // For nilpotent operations or addition there may be no operands, for example
701 // because the expression was "X xor X" or consisted of 2^Bitwidth additions:
702 // in both cases the weight reduces to 0 causing the value to be skipped.
704 Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
705 assert(Identity && "Associative operation without identity!");
706 Ops.emplace_back(Identity, APInt(Bitwidth, 1));
712 /// Now that the operands for this expression tree are
713 /// linearized and optimized, emit them in-order.
714 void Reassociate::RewriteExprTree(BinaryOperator *I,
715 SmallVectorImpl<ValueEntry> &Ops) {
716 assert(Ops.size() > 1 && "Single values should be used directly!");
718 // Since our optimizations should never increase the number of operations, the
719 // new expression can usually be written reusing the existing binary operators
720 // from the original expression tree, without creating any new instructions,
721 // though the rewritten expression may have a completely different topology.
722 // We take care to not change anything if the new expression will be the same
723 // as the original. If more than trivial changes (like commuting operands)
724 // were made then we are obliged to clear out any optional subclass data like
727 /// NodesToRewrite - Nodes from the original expression available for writing
728 /// the new expression into.
729 SmallVector<BinaryOperator*, 8> NodesToRewrite;
730 unsigned Opcode = I->getOpcode();
731 BinaryOperator *Op = I;
733 /// NotRewritable - The operands being written will be the leaves of the new
734 /// expression and must not be used as inner nodes (via NodesToRewrite) by
735 /// mistake. Inner nodes are always reassociable, and usually leaves are not
736 /// (if they were they would have been incorporated into the expression and so
737 /// would not be leaves), so most of the time there is no danger of this. But
738 /// in rare cases a leaf may become reassociable if an optimization kills uses
739 /// of it, or it may momentarily become reassociable during rewriting (below)
740 /// due it being removed as an operand of one of its uses. Ensure that misuse
741 /// of leaf nodes as inner nodes cannot occur by remembering all of the future
742 /// leaves and refusing to reuse any of them as inner nodes.
743 SmallPtrSet<Value*, 8> NotRewritable;
744 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
745 NotRewritable.insert(Ops[i].Op);
747 // ExpressionChanged - Non-null if the rewritten expression differs from the
748 // original in some non-trivial way, requiring the clearing of optional flags.
749 // Flags are cleared from the operator in ExpressionChanged up to I inclusive.
750 BinaryOperator *ExpressionChanged = nullptr;
751 for (unsigned i = 0; ; ++i) {
752 // The last operation (which comes earliest in the IR) is special as both
753 // operands will come from Ops, rather than just one with the other being
755 if (i+2 == Ops.size()) {
756 Value *NewLHS = Ops[i].Op;
757 Value *NewRHS = Ops[i+1].Op;
758 Value *OldLHS = Op->getOperand(0);
759 Value *OldRHS = Op->getOperand(1);
761 if (NewLHS == OldLHS && NewRHS == OldRHS)
762 // Nothing changed, leave it alone.
765 if (NewLHS == OldRHS && NewRHS == OldLHS) {
766 // The order of the operands was reversed. Swap them.
767 DEBUG(dbgs() << "RA: " << *Op << '\n');
769 DEBUG(dbgs() << "TO: " << *Op << '\n');
775 // The new operation differs non-trivially from the original. Overwrite
776 // the old operands with the new ones.
777 DEBUG(dbgs() << "RA: " << *Op << '\n');
778 if (NewLHS != OldLHS) {
779 BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
780 if (BO && !NotRewritable.count(BO))
781 NodesToRewrite.push_back(BO);
782 Op->setOperand(0, NewLHS);
784 if (NewRHS != OldRHS) {
785 BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
786 if (BO && !NotRewritable.count(BO))
787 NodesToRewrite.push_back(BO);
788 Op->setOperand(1, NewRHS);
790 DEBUG(dbgs() << "TO: " << *Op << '\n');
792 ExpressionChanged = Op;
799 // Not the last operation. The left-hand side will be a sub-expression
800 // while the right-hand side will be the current element of Ops.
801 Value *NewRHS = Ops[i].Op;
802 if (NewRHS != Op->getOperand(1)) {
803 DEBUG(dbgs() << "RA: " << *Op << '\n');
804 if (NewRHS == Op->getOperand(0)) {
805 // The new right-hand side was already present as the left operand. If
806 // we are lucky then swapping the operands will sort out both of them.
809 // Overwrite with the new right-hand side.
810 BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
811 if (BO && !NotRewritable.count(BO))
812 NodesToRewrite.push_back(BO);
813 Op->setOperand(1, NewRHS);
814 ExpressionChanged = Op;
816 DEBUG(dbgs() << "TO: " << *Op << '\n');
821 // Now deal with the left-hand side. If this is already an operation node
822 // from the original expression then just rewrite the rest of the expression
824 BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode);
825 if (BO && !NotRewritable.count(BO)) {
830 // Otherwise, grab a spare node from the original expression and use that as
831 // the left-hand side. If there are no nodes left then the optimizers made
832 // an expression with more nodes than the original! This usually means that
833 // they did something stupid but it might mean that the problem was just too
834 // hard (finding the mimimal number of multiplications needed to realize a
835 // multiplication expression is NP-complete). Whatever the reason, smart or
836 // stupid, create a new node if there are none left.
837 BinaryOperator *NewOp;
838 if (NodesToRewrite.empty()) {
839 Constant *Undef = UndefValue::get(I->getType());
840 NewOp = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
841 Undef, Undef, "", I);
842 if (NewOp->getType()->isFPOrFPVectorTy())
843 NewOp->setFastMathFlags(I->getFastMathFlags());
845 NewOp = NodesToRewrite.pop_back_val();
848 DEBUG(dbgs() << "RA: " << *Op << '\n');
849 Op->setOperand(0, NewOp);
850 DEBUG(dbgs() << "TO: " << *Op << '\n');
851 ExpressionChanged = Op;
857 // If the expression changed non-trivially then clear out all subclass data
858 // starting from the operator specified in ExpressionChanged, and compactify
859 // the operators to just before the expression root to guarantee that the
860 // expression tree is dominated by all of Ops.
861 if (ExpressionChanged)
863 // Preserve FastMathFlags.
864 if (isa<FPMathOperator>(I)) {
865 FastMathFlags Flags = I->getFastMathFlags();
866 ExpressionChanged->clearSubclassOptionalData();
867 ExpressionChanged->setFastMathFlags(Flags);
869 ExpressionChanged->clearSubclassOptionalData();
871 if (ExpressionChanged == I)
873 ExpressionChanged->moveBefore(I);
874 ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->user_begin());
877 // Throw away any left over nodes from the original expression.
878 for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)
879 RedoInsts.insert(NodesToRewrite[i]);
882 /// Insert instructions before the instruction pointed to by BI,
883 /// that computes the negative version of the value specified. The negative
884 /// version of the value is returned, and BI is left pointing at the instruction
885 /// that should be processed next by the reassociation pass.
886 /// Also add intermediate instructions to the redo list that are modified while
887 /// pushing the negates through adds. These will be revisited to see if
888 /// additional opportunities have been exposed.
889 static Value *NegateValue(Value *V, Instruction *BI,
890 SetVector<AssertingVH<Instruction>> &ToRedo) {
891 if (Constant *C = dyn_cast<Constant>(V)) {
892 if (C->getType()->isFPOrFPVectorTy()) {
893 return ConstantExpr::getFNeg(C);
895 return ConstantExpr::getNeg(C);
899 // We are trying to expose opportunity for reassociation. One of the things
900 // that we want to do to achieve this is to push a negation as deep into an
901 // expression chain as possible, to expose the add instructions. In practice,
902 // this means that we turn this:
903 // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
904 // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
905 // the constants. We assume that instcombine will clean up the mess later if
906 // we introduce tons of unnecessary negation instructions.
908 if (BinaryOperator *I =
909 isReassociableOp(V, Instruction::Add, Instruction::FAdd)) {
910 // Push the negates through the add.
911 I->setOperand(0, NegateValue(I->getOperand(0), BI, ToRedo));
912 I->setOperand(1, NegateValue(I->getOperand(1), BI, ToRedo));
913 if (I->getOpcode() == Instruction::Add) {
914 I->setHasNoUnsignedWrap(false);
915 I->setHasNoSignedWrap(false);
918 // We must move the add instruction here, because the neg instructions do
919 // not dominate the old add instruction in general. By moving it, we are
920 // assured that the neg instructions we just inserted dominate the
921 // instruction we are about to insert after them.
924 I->setName(I->getName()+".neg");
926 // Add the intermediate negates to the redo list as processing them later
927 // could expose more reassociating opportunities.
932 // Okay, we need to materialize a negated version of V with an instruction.
933 // Scan the use lists of V to see if we have one already.
934 for (User *U : V->users()) {
935 if (!BinaryOperator::isNeg(U) && !BinaryOperator::isFNeg(U))
938 // We found one! Now we have to make sure that the definition dominates
939 // this use. We do this by moving it to the entry block (if it is a
940 // non-instruction value) or right after the definition. These negates will
941 // be zapped by reassociate later, so we don't need much finesse here.
942 BinaryOperator *TheNeg = cast<BinaryOperator>(U);
944 // Verify that the negate is in this function, V might be a constant expr.
945 if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
948 BasicBlock::iterator InsertPt;
949 if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
950 if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
951 InsertPt = II->getNormalDest()->begin();
953 InsertPt = ++InstInput->getIterator();
955 while (isa<PHINode>(InsertPt)) ++InsertPt;
957 InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
959 TheNeg->moveBefore(&*InsertPt);
960 if (TheNeg->getOpcode() == Instruction::Sub) {
961 TheNeg->setHasNoUnsignedWrap(false);
962 TheNeg->setHasNoSignedWrap(false);
964 TheNeg->andIRFlags(BI);
966 ToRedo.insert(TheNeg);
970 // Insert a 'neg' instruction that subtracts the value from zero to get the
972 BinaryOperator *NewNeg = CreateNeg(V, V->getName() + ".neg", BI, BI);
973 ToRedo.insert(NewNeg);
977 /// Return true if we should break up this subtract of X-Y into (X + -Y).
978 static bool ShouldBreakUpSubtract(Instruction *Sub) {
979 // If this is a negation, we can't split it up!
980 if (BinaryOperator::isNeg(Sub) || BinaryOperator::isFNeg(Sub))
983 // Don't breakup X - undef.
984 if (isa<UndefValue>(Sub->getOperand(1)))
987 // Don't bother to break this up unless either the LHS is an associable add or
988 // subtract or if this is only used by one.
989 Value *V0 = Sub->getOperand(0);
990 if (isReassociableOp(V0, Instruction::Add, Instruction::FAdd) ||
991 isReassociableOp(V0, Instruction::Sub, Instruction::FSub))
993 Value *V1 = Sub->getOperand(1);
994 if (isReassociableOp(V1, Instruction::Add, Instruction::FAdd) ||
995 isReassociableOp(V1, Instruction::Sub, Instruction::FSub))
997 Value *VB = Sub->user_back();
998 if (Sub->hasOneUse() &&
999 (isReassociableOp(VB, Instruction::Add, Instruction::FAdd) ||
1000 isReassociableOp(VB, Instruction::Sub, Instruction::FSub)))
1006 /// If we have (X-Y), and if either X is an add, or if this is only used by an
1007 /// add, transform this into (X+(0-Y)) to promote better reassociation.
1008 static BinaryOperator *
1009 BreakUpSubtract(Instruction *Sub, SetVector<AssertingVH<Instruction>> &ToRedo) {
1010 // Convert a subtract into an add and a neg instruction. This allows sub
1011 // instructions to be commuted with other add instructions.
1013 // Calculate the negative value of Operand 1 of the sub instruction,
1014 // and set it as the RHS of the add instruction we just made.
1016 Value *NegVal = NegateValue(Sub->getOperand(1), Sub, ToRedo);
1017 BinaryOperator *New = CreateAdd(Sub->getOperand(0), NegVal, "", Sub, Sub);
1018 Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op.
1019 Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op.
1022 // Everyone now refers to the add instruction.
1023 Sub->replaceAllUsesWith(New);
1024 New->setDebugLoc(Sub->getDebugLoc());
1026 DEBUG(dbgs() << "Negated: " << *New << '\n');
1030 /// If this is a shift of a reassociable multiply or is used by one, change
1031 /// this into a multiply by a constant to assist with further reassociation.
1032 static BinaryOperator *ConvertShiftToMul(Instruction *Shl) {
1033 Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
1034 MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
1036 BinaryOperator *Mul =
1037 BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
1038 Shl->setOperand(0, UndefValue::get(Shl->getType())); // Drop use of op.
1041 // Everyone now refers to the mul instruction.
1042 Shl->replaceAllUsesWith(Mul);
1043 Mul->setDebugLoc(Shl->getDebugLoc());
1045 // We can safely preserve the nuw flag in all cases. It's also safe to turn a
1046 // nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special
1048 bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap();
1049 bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap();
1051 Mul->setHasNoSignedWrap(true);
1052 Mul->setHasNoUnsignedWrap(NUW);
1056 /// Scan backwards and forwards among values with the same rank as element i
1057 /// to see if X exists. If X does not exist, return i. This is useful when
1058 /// scanning for 'x' when we see '-x' because they both get the same rank.
1059 static unsigned FindInOperandList(SmallVectorImpl<ValueEntry> &Ops, unsigned i,
1061 unsigned XRank = Ops[i].Rank;
1062 unsigned e = Ops.size();
1063 for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
1066 if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
1067 if (Instruction *I2 = dyn_cast<Instruction>(X))
1068 if (I1->isIdenticalTo(I2))
1072 for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
1075 if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
1076 if (Instruction *I2 = dyn_cast<Instruction>(X))
1077 if (I1->isIdenticalTo(I2))
1083 /// Emit a tree of add instructions, summing Ops together
1084 /// and returning the result. Insert the tree before I.
1085 static Value *EmitAddTreeOfValues(Instruction *I,
1086 SmallVectorImpl<WeakVH> &Ops){
1087 if (Ops.size() == 1) return Ops.back();
1089 Value *V1 = Ops.back();
1091 Value *V2 = EmitAddTreeOfValues(I, Ops);
1092 return CreateAdd(V2, V1, "tmp", I, I);
1095 /// If V is an expression tree that is a multiplication sequence,
1096 /// and if this sequence contains a multiply by Factor,
1097 /// remove Factor from the tree and return the new tree.
1098 Value *Reassociate::RemoveFactorFromExpression(Value *V, Value *Factor) {
1099 BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
1103 SmallVector<RepeatedValue, 8> Tree;
1104 MadeChange |= LinearizeExprTree(BO, Tree);
1105 SmallVector<ValueEntry, 8> Factors;
1106 Factors.reserve(Tree.size());
1107 for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
1108 RepeatedValue E = Tree[i];
1109 Factors.append(E.second.getZExtValue(),
1110 ValueEntry(getRank(E.first), E.first));
1113 bool FoundFactor = false;
1114 bool NeedsNegate = false;
1115 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1116 if (Factors[i].Op == Factor) {
1118 Factors.erase(Factors.begin()+i);
1122 // If this is a negative version of this factor, remove it.
1123 if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor)) {
1124 if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
1125 if (FC1->getValue() == -FC2->getValue()) {
1126 FoundFactor = NeedsNegate = true;
1127 Factors.erase(Factors.begin()+i);
1130 } else if (ConstantFP *FC1 = dyn_cast<ConstantFP>(Factor)) {
1131 if (ConstantFP *FC2 = dyn_cast<ConstantFP>(Factors[i].Op)) {
1132 APFloat F1(FC1->getValueAPF());
1133 APFloat F2(FC2->getValueAPF());
1135 if (F1.compare(F2) == APFloat::cmpEqual) {
1136 FoundFactor = NeedsNegate = true;
1137 Factors.erase(Factors.begin() + i);
1145 // Make sure to restore the operands to the expression tree.
1146 RewriteExprTree(BO, Factors);
1150 BasicBlock::iterator InsertPt = ++BO->getIterator();
1152 // If this was just a single multiply, remove the multiply and return the only
1153 // remaining operand.
1154 if (Factors.size() == 1) {
1155 RedoInsts.insert(BO);
1158 RewriteExprTree(BO, Factors);
1163 V = CreateNeg(V, "neg", &*InsertPt, BO);
1168 /// If V is a single-use multiply, recursively add its operands as factors,
1169 /// otherwise add V to the list of factors.
1171 /// Ops is the top-level list of add operands we're trying to factor.
1172 static void FindSingleUseMultiplyFactors(Value *V,
1173 SmallVectorImpl<Value*> &Factors,
1174 const SmallVectorImpl<ValueEntry> &Ops) {
1175 BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
1177 Factors.push_back(V);
1181 // Otherwise, add the LHS and RHS to the list of factors.
1182 FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops);
1183 FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops);
1186 /// Optimize a series of operands to an 'and', 'or', or 'xor' instruction.
1187 /// This optimizes based on identities. If it can be reduced to a single Value,
1188 /// it is returned, otherwise the Ops list is mutated as necessary.
1189 static Value *OptimizeAndOrXor(unsigned Opcode,
1190 SmallVectorImpl<ValueEntry> &Ops) {
1191 // Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
1192 // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
1193 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1194 // First, check for X and ~X in the operand list.
1195 assert(i < Ops.size());
1196 if (BinaryOperator::isNot(Ops[i].Op)) { // Cannot occur for ^.
1197 Value *X = BinaryOperator::getNotArgument(Ops[i].Op);
1198 unsigned FoundX = FindInOperandList(Ops, i, X);
1200 if (Opcode == Instruction::And) // ...&X&~X = 0
1201 return Constant::getNullValue(X->getType());
1203 if (Opcode == Instruction::Or) // ...|X|~X = -1
1204 return Constant::getAllOnesValue(X->getType());
1208 // Next, check for duplicate pairs of values, which we assume are next to
1209 // each other, due to our sorting criteria.
1210 assert(i < Ops.size());
1211 if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
1212 if (Opcode == Instruction::And || Opcode == Instruction::Or) {
1213 // Drop duplicate values for And and Or.
1214 Ops.erase(Ops.begin()+i);
1220 // Drop pairs of values for Xor.
1221 assert(Opcode == Instruction::Xor);
1223 return Constant::getNullValue(Ops[0].Op->getType());
1226 Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
1234 /// Helper function of CombineXorOpnd(). It creates a bitwise-and
1235 /// instruction with the given two operands, and return the resulting
1236 /// instruction. There are two special cases: 1) if the constant operand is 0,
1237 /// it will return NULL. 2) if the constant is ~0, the symbolic operand will
1239 static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd,
1240 const APInt &ConstOpnd) {
1241 if (ConstOpnd != 0) {
1242 if (!ConstOpnd.isAllOnesValue()) {
1243 LLVMContext &Ctx = Opnd->getType()->getContext();
1245 I = BinaryOperator::CreateAnd(Opnd, ConstantInt::get(Ctx, ConstOpnd),
1246 "and.ra", InsertBefore);
1247 I->setDebugLoc(InsertBefore->getDebugLoc());
1255 // Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
1256 // into "R ^ C", where C would be 0, and R is a symbolic value.
1258 // If it was successful, true is returned, and the "R" and "C" is returned
1259 // via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
1260 // and both "Res" and "ConstOpnd" remain unchanged.
1262 bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
1263 APInt &ConstOpnd, Value *&Res) {
1264 // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
1265 // = ((x | c1) ^ c1) ^ (c1 ^ c2)
1266 // = (x & ~c1) ^ (c1 ^ c2)
1267 // It is useful only when c1 == c2.
1268 if (Opnd1->isOrExpr() && Opnd1->getConstPart() != 0) {
1269 if (!Opnd1->getValue()->hasOneUse())
1272 const APInt &C1 = Opnd1->getConstPart();
1273 if (C1 != ConstOpnd)
1276 Value *X = Opnd1->getSymbolicPart();
1277 Res = createAndInstr(I, X, ~C1);
1278 // ConstOpnd was C2, now C1 ^ C2.
1281 if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1282 RedoInsts.insert(T);
1289 // Helper function of OptimizeXor(). It tries to simplify
1290 // "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
1293 // If it was successful, true is returned, and the "R" and "C" is returned
1294 // via "Res" and "ConstOpnd", respectively (If the entire expression is
1295 // evaluated to a constant, the Res is set to NULL); otherwise, false is
1296 // returned, and both "Res" and "ConstOpnd" remain unchanged.
1297 bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
1298 APInt &ConstOpnd, Value *&Res) {
1299 Value *X = Opnd1->getSymbolicPart();
1300 if (X != Opnd2->getSymbolicPart())
1303 // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
1304 int DeadInstNum = 1;
1305 if (Opnd1->getValue()->hasOneUse())
1307 if (Opnd2->getValue()->hasOneUse())
1311 // (x | c1) ^ (x & c2)
1312 // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
1313 // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
1314 // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
1316 if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
1317 if (Opnd2->isOrExpr())
1318 std::swap(Opnd1, Opnd2);
1320 const APInt &C1 = Opnd1->getConstPart();
1321 const APInt &C2 = Opnd2->getConstPart();
1322 APInt C3((~C1) ^ C2);
1324 // Do not increase code size!
1325 if (C3 != 0 && !C3.isAllOnesValue()) {
1326 int NewInstNum = ConstOpnd != 0 ? 1 : 2;
1327 if (NewInstNum > DeadInstNum)
1331 Res = createAndInstr(I, X, C3);
1334 } else if (Opnd1->isOrExpr()) {
1335 // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
1337 const APInt &C1 = Opnd1->getConstPart();
1338 const APInt &C2 = Opnd2->getConstPart();
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 // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
1353 const APInt &C1 = Opnd1->getConstPart();
1354 const APInt &C2 = Opnd2->getConstPart();
1356 Res = createAndInstr(I, X, C3);
1359 // Put the original operands in the Redo list; hope they will be deleted
1361 if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1362 RedoInsts.insert(T);
1363 if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
1364 RedoInsts.insert(T);
1369 /// Optimize a series of operands to an 'xor' instruction. If it can be reduced
1370 /// to a single Value, it is returned, otherwise the Ops list is mutated as
1372 Value *Reassociate::OptimizeXor(Instruction *I,
1373 SmallVectorImpl<ValueEntry> &Ops) {
1374 if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
1377 if (Ops.size() == 1)
1380 SmallVector<XorOpnd, 8> Opnds;
1381 SmallVector<XorOpnd*, 8> OpndPtrs;
1382 Type *Ty = Ops[0].Op->getType();
1383 APInt ConstOpnd(Ty->getIntegerBitWidth(), 0);
1385 // Step 1: Convert ValueEntry to XorOpnd
1386 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1387 Value *V = Ops[i].Op;
1388 if (!isa<ConstantInt>(V)) {
1390 O.setSymbolicRank(getRank(O.getSymbolicPart()));
1393 ConstOpnd ^= cast<ConstantInt>(V)->getValue();
1396 // NOTE: From this point on, do *NOT* add/delete element to/from "Opnds".
1397 // It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate
1398 // the "OpndPtrs" as well. For the similar reason, do not fuse this loop
1399 // with the previous loop --- the iterator of the "Opnds" may be invalidated
1400 // when new elements are added to the vector.
1401 for (unsigned i = 0, e = Opnds.size(); i != e; ++i)
1402 OpndPtrs.push_back(&Opnds[i]);
1404 // Step 2: Sort the Xor-Operands in a way such that the operands containing
1405 // the same symbolic value cluster together. For instance, the input operand
1406 // sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
1407 // ("x | 123", "x & 789", "y & 456").
1408 std::stable_sort(OpndPtrs.begin(), OpndPtrs.end(), XorOpnd::PtrSortFunctor());
1410 // Step 3: Combine adjacent operands
1411 XorOpnd *PrevOpnd = nullptr;
1412 bool Changed = false;
1413 for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
1414 XorOpnd *CurrOpnd = OpndPtrs[i];
1415 // The combined value
1418 // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
1419 if (ConstOpnd != 0 && CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
1422 *CurrOpnd = XorOpnd(CV);
1424 CurrOpnd->Invalidate();
1429 if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
1430 PrevOpnd = CurrOpnd;
1434 // step 3.2: When previous and current operands share the same symbolic
1435 // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
1437 if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
1438 // Remove previous operand
1439 PrevOpnd->Invalidate();
1441 *CurrOpnd = XorOpnd(CV);
1442 PrevOpnd = CurrOpnd;
1444 CurrOpnd->Invalidate();
1451 // Step 4: Reassemble the Ops
1454 for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
1455 XorOpnd &O = Opnds[i];
1458 ValueEntry VE(getRank(O.getValue()), O.getValue());
1461 if (ConstOpnd != 0) {
1462 Value *C = ConstantInt::get(Ty->getContext(), ConstOpnd);
1463 ValueEntry VE(getRank(C), C);
1466 int Sz = Ops.size();
1468 return Ops.back().Op;
1470 assert(ConstOpnd == 0);
1471 return ConstantInt::get(Ty->getContext(), ConstOpnd);
1478 /// Optimize a series of operands to an 'add' instruction. This
1479 /// optimizes based on identities. If it can be reduced to a single Value, it
1480 /// is returned, otherwise the Ops list is mutated as necessary.
1481 Value *Reassociate::OptimizeAdd(Instruction *I,
1482 SmallVectorImpl<ValueEntry> &Ops) {
1483 // Scan the operand lists looking for X and -X pairs. If we find any, we
1484 // can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it,
1486 // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
1488 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1489 Value *TheOp = Ops[i].Op;
1490 // Check to see if we've seen this operand before. If so, we factor all
1491 // instances of the operand together. Due to our sorting criteria, we know
1492 // that these need to be next to each other in the vector.
1493 if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
1494 // Rescan the list, remove all instances of this operand from the expr.
1495 unsigned NumFound = 0;
1497 Ops.erase(Ops.begin()+i);
1499 } while (i != Ops.size() && Ops[i].Op == TheOp);
1501 DEBUG(dbgs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n');
1504 // Insert a new multiply.
1505 Type *Ty = TheOp->getType();
1506 Constant *C = Ty->isIntOrIntVectorTy() ?
1507 ConstantInt::get(Ty, NumFound) : ConstantFP::get(Ty, NumFound);
1508 Instruction *Mul = CreateMul(TheOp, C, "factor", I, I);
1510 // Now that we have inserted a multiply, optimize it. This allows us to
1511 // handle cases that require multiple factoring steps, such as this:
1512 // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
1513 RedoInsts.insert(Mul);
1515 // If every add operand was a duplicate, return the multiply.
1519 // Otherwise, we had some input that didn't have the dupe, such as
1520 // "A + A + B" -> "A*2 + B". Add the new multiply to the list of
1521 // things being added by this operation.
1522 Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
1529 // Check for X and -X or X and ~X in the operand list.
1530 if (!BinaryOperator::isNeg(TheOp) && !BinaryOperator::isFNeg(TheOp) &&
1531 !BinaryOperator::isNot(TheOp))
1535 if (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp))
1536 X = BinaryOperator::getNegArgument(TheOp);
1537 else if (BinaryOperator::isNot(TheOp))
1538 X = BinaryOperator::getNotArgument(TheOp);
1540 unsigned FoundX = FindInOperandList(Ops, i, X);
1544 // Remove X and -X from the operand list.
1545 if (Ops.size() == 2 &&
1546 (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp)))
1547 return Constant::getNullValue(X->getType());
1549 // Remove X and ~X from the operand list.
1550 if (Ops.size() == 2 && BinaryOperator::isNot(TheOp))
1551 return Constant::getAllOnesValue(X->getType());
1553 Ops.erase(Ops.begin()+i);
1557 --i; // Need to back up an extra one.
1558 Ops.erase(Ops.begin()+FoundX);
1560 --i; // Revisit element.
1561 e -= 2; // Removed two elements.
1563 // if X and ~X we append -1 to the operand list.
1564 if (BinaryOperator::isNot(TheOp)) {
1565 Value *V = Constant::getAllOnesValue(X->getType());
1566 Ops.insert(Ops.end(), ValueEntry(getRank(V), V));
1571 // Scan the operand list, checking to see if there are any common factors
1572 // between operands. Consider something like A*A+A*B*C+D. We would like to
1573 // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
1574 // To efficiently find this, we count the number of times a factor occurs
1575 // for any ADD operands that are MULs.
1576 DenseMap<Value*, unsigned> FactorOccurrences;
1578 // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
1579 // where they are actually the same multiply.
1580 unsigned MaxOcc = 0;
1581 Value *MaxOccVal = nullptr;
1582 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1583 BinaryOperator *BOp =
1584 isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1588 // Compute all of the factors of this added value.
1589 SmallVector<Value*, 8> Factors;
1590 FindSingleUseMultiplyFactors(BOp, Factors, Ops);
1591 assert(Factors.size() > 1 && "Bad linearize!");
1593 // Add one to FactorOccurrences for each unique factor in this op.
1594 SmallPtrSet<Value*, 8> Duplicates;
1595 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1596 Value *Factor = Factors[i];
1597 if (!Duplicates.insert(Factor).second)
1600 unsigned Occ = ++FactorOccurrences[Factor];
1606 // If Factor is a negative constant, add the negated value as a factor
1607 // because we can percolate the negate out. Watch for minint, which
1608 // cannot be positivified.
1609 if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor)) {
1610 if (CI->isNegative() && !CI->isMinValue(true)) {
1611 Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
1612 assert(!Duplicates.count(Factor) &&
1613 "Shouldn't have two constant factors, missed a canonicalize");
1614 unsigned Occ = ++FactorOccurrences[Factor];
1620 } else if (ConstantFP *CF = dyn_cast<ConstantFP>(Factor)) {
1621 if (CF->isNegative()) {
1622 APFloat F(CF->getValueAPF());
1624 Factor = ConstantFP::get(CF->getContext(), F);
1625 assert(!Duplicates.count(Factor) &&
1626 "Shouldn't have two constant factors, missed a canonicalize");
1627 unsigned Occ = ++FactorOccurrences[Factor];
1637 // If any factor occurred more than one time, we can pull it out.
1639 DEBUG(dbgs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
1642 // Create a new instruction that uses the MaxOccVal twice. If we don't do
1643 // this, we could otherwise run into situations where removing a factor
1644 // from an expression will drop a use of maxocc, and this can cause
1645 // RemoveFactorFromExpression on successive values to behave differently.
1646 Instruction *DummyInst =
1647 I->getType()->isIntOrIntVectorTy()
1648 ? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal)
1649 : BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal);
1651 SmallVector<WeakVH, 4> NewMulOps;
1652 for (unsigned i = 0; i != Ops.size(); ++i) {
1653 // Only try to remove factors from expressions we're allowed to.
1654 BinaryOperator *BOp =
1655 isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1659 if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
1660 // The factorized operand may occur several times. Convert them all in
1662 for (unsigned j = Ops.size(); j != i;) {
1664 if (Ops[j].Op == Ops[i].Op) {
1665 NewMulOps.push_back(V);
1666 Ops.erase(Ops.begin()+j);
1673 // No need for extra uses anymore.
1676 unsigned NumAddedValues = NewMulOps.size();
1677 Value *V = EmitAddTreeOfValues(I, NewMulOps);
1679 // Now that we have inserted the add tree, optimize it. This allows us to
1680 // handle cases that require multiple factoring steps, such as this:
1681 // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
1682 assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
1683 (void)NumAddedValues;
1684 if (Instruction *VI = dyn_cast<Instruction>(V))
1685 RedoInsts.insert(VI);
1687 // Create the multiply.
1688 Instruction *V2 = CreateMul(V, MaxOccVal, "tmp", I, I);
1690 // Rerun associate on the multiply in case the inner expression turned into
1691 // a multiply. We want to make sure that we keep things in canonical form.
1692 RedoInsts.insert(V2);
1694 // If every add operand included the factor (e.g. "A*B + A*C"), then the
1695 // entire result expression is just the multiply "A*(B+C)".
1699 // Otherwise, we had some input that didn't have the factor, such as
1700 // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
1701 // things being added by this operation.
1702 Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
1708 /// \brief Build up a vector of value/power pairs factoring a product.
1710 /// Given a series of multiplication operands, build a vector of factors and
1711 /// the powers each is raised to when forming the final product. Sort them in
1712 /// the order of descending power.
1714 /// (x*x) -> [(x, 2)]
1715 /// ((x*x)*x) -> [(x, 3)]
1716 /// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
1718 /// \returns Whether any factors have a power greater than one.
1719 bool Reassociate::collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
1720 SmallVectorImpl<Factor> &Factors) {
1721 // FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this.
1722 // Compute the sum of powers of simplifiable factors.
1723 unsigned FactorPowerSum = 0;
1724 for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) {
1725 Value *Op = Ops[Idx-1].Op;
1727 // Count the number of occurrences of this value.
1729 for (; Idx < Size && Ops[Idx].Op == Op; ++Idx)
1731 // Track for simplification all factors which occur 2 or more times.
1733 FactorPowerSum += Count;
1736 // We can only simplify factors if the sum of the powers of our simplifiable
1737 // factors is 4 or higher. When that is the case, we will *always* have
1738 // a simplification. This is an important invariant to prevent cyclicly
1739 // trying to simplify already minimal formations.
1740 if (FactorPowerSum < 4)
1743 // Now gather the simplifiable factors, removing them from Ops.
1745 for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) {
1746 Value *Op = Ops[Idx-1].Op;
1748 // Count the number of occurrences of this value.
1750 for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx)
1754 // Move an even number of occurrences to Factors.
1757 FactorPowerSum += Count;
1758 Factors.push_back(Factor(Op, Count));
1759 Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count);
1762 // None of the adjustments above should have reduced the sum of factor powers
1763 // below our mininum of '4'.
1764 assert(FactorPowerSum >= 4);
1766 std::stable_sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter());
1770 /// \brief Build a tree of multiplies, computing the product of Ops.
1771 static Value *buildMultiplyTree(IRBuilder<> &Builder,
1772 SmallVectorImpl<Value*> &Ops) {
1773 if (Ops.size() == 1)
1776 Value *LHS = Ops.pop_back_val();
1778 if (LHS->getType()->isIntOrIntVectorTy())
1779 LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
1781 LHS = Builder.CreateFMul(LHS, Ops.pop_back_val());
1782 } while (!Ops.empty());
1787 /// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
1789 /// Given a vector of values raised to various powers, where no two values are
1790 /// equal and the powers are sorted in decreasing order, compute the minimal
1791 /// DAG of multiplies to compute the final product, and return that product
1793 Value *Reassociate::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
1794 SmallVectorImpl<Factor> &Factors) {
1795 assert(Factors[0].Power);
1796 SmallVector<Value *, 4> OuterProduct;
1797 for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
1798 Idx < Size && Factors[Idx].Power > 0; ++Idx) {
1799 if (Factors[Idx].Power != Factors[LastIdx].Power) {
1804 // We want to multiply across all the factors with the same power so that
1805 // we can raise them to that power as a single entity. Build a mini tree
1807 SmallVector<Value *, 4> InnerProduct;
1808 InnerProduct.push_back(Factors[LastIdx].Base);
1810 InnerProduct.push_back(Factors[Idx].Base);
1812 } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
1814 // Reset the base value of the first factor to the new expression tree.
1815 // We'll remove all the factors with the same power in a second pass.
1816 Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
1817 if (Instruction *MI = dyn_cast<Instruction>(M))
1818 RedoInsts.insert(MI);
1822 // Unique factors with equal powers -- we've folded them into the first one's
1824 Factors.erase(std::unique(Factors.begin(), Factors.end(),
1825 Factor::PowerEqual()),
1828 // Iteratively collect the base of each factor with an add power into the
1829 // outer product, and halve each power in preparation for squaring the
1831 for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
1832 if (Factors[Idx].Power & 1)
1833 OuterProduct.push_back(Factors[Idx].Base);
1834 Factors[Idx].Power >>= 1;
1836 if (Factors[0].Power) {
1837 Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
1838 OuterProduct.push_back(SquareRoot);
1839 OuterProduct.push_back(SquareRoot);
1841 if (OuterProduct.size() == 1)
1842 return OuterProduct.front();
1844 Value *V = buildMultiplyTree(Builder, OuterProduct);
1848 Value *Reassociate::OptimizeMul(BinaryOperator *I,
1849 SmallVectorImpl<ValueEntry> &Ops) {
1850 // We can only optimize the multiplies when there is a chain of more than
1851 // three, such that a balanced tree might require fewer total multiplies.
1855 // Try to turn linear trees of multiplies without other uses of the
1856 // intermediate stages into minimal multiply DAGs with perfect sub-expression
1858 SmallVector<Factor, 4> Factors;
1859 if (!collectMultiplyFactors(Ops, Factors))
1860 return nullptr; // All distinct factors, so nothing left for us to do.
1862 IRBuilder<> Builder(I);
1863 Value *V = buildMinimalMultiplyDAG(Builder, Factors);
1867 ValueEntry NewEntry = ValueEntry(getRank(V), V);
1868 Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry);
1872 Value *Reassociate::OptimizeExpression(BinaryOperator *I,
1873 SmallVectorImpl<ValueEntry> &Ops) {
1874 // Now that we have the linearized expression tree, try to optimize it.
1875 // Start by folding any constants that we found.
1876 Constant *Cst = nullptr;
1877 unsigned Opcode = I->getOpcode();
1878 while (!Ops.empty() && isa<Constant>(Ops.back().Op)) {
1879 Constant *C = cast<Constant>(Ops.pop_back_val().Op);
1880 Cst = Cst ? ConstantExpr::get(Opcode, C, Cst) : C;
1882 // If there was nothing but constants then we are done.
1886 // Put the combined constant back at the end of the operand list, except if
1887 // there is no point. For example, an add of 0 gets dropped here, while a
1888 // multiplication by zero turns the whole expression into zero.
1889 if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) {
1890 if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType()))
1892 Ops.push_back(ValueEntry(0, Cst));
1895 if (Ops.size() == 1) return Ops[0].Op;
1897 // Handle destructive annihilation due to identities between elements in the
1898 // argument list here.
1899 unsigned NumOps = Ops.size();
1902 case Instruction::And:
1903 case Instruction::Or:
1904 if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
1908 case Instruction::Xor:
1909 if (Value *Result = OptimizeXor(I, Ops))
1913 case Instruction::Add:
1914 case Instruction::FAdd:
1915 if (Value *Result = OptimizeAdd(I, Ops))
1919 case Instruction::Mul:
1920 case Instruction::FMul:
1921 if (Value *Result = OptimizeMul(I, Ops))
1926 if (Ops.size() != NumOps)
1927 return OptimizeExpression(I, Ops);
1931 // Remove dead instructions and if any operands are trivially dead add them to
1932 // Insts so they will be removed as well.
1933 void Reassociate::RecursivelyEraseDeadInsts(
1934 Instruction *I, SetVector<AssertingVH<Instruction>> &Insts) {
1935 assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
1936 SmallVector<Value *, 4> Ops(I->op_begin(), I->op_end());
1937 ValueRankMap.erase(I);
1939 RedoInsts.remove(I);
1940 I->eraseFromParent();
1942 if (Instruction *OpInst = dyn_cast<Instruction>(Op))
1943 if (OpInst->use_empty())
1944 Insts.insert(OpInst);
1947 /// Zap the given instruction, adding interesting operands to the work list.
1948 void Reassociate::EraseInst(Instruction *I) {
1949 assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
1950 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
1951 // Erase the dead instruction.
1952 ValueRankMap.erase(I);
1953 RedoInsts.remove(I);
1954 I->eraseFromParent();
1955 // Optimize its operands.
1956 SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
1957 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1958 if (Instruction *Op = dyn_cast<Instruction>(Ops[i])) {
1959 // If this is a node in an expression tree, climb to the expression root
1960 // and add that since that's where optimization actually happens.
1961 unsigned Opcode = Op->getOpcode();
1962 while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode &&
1963 Visited.insert(Op).second)
1964 Op = Op->user_back();
1965 RedoInsts.insert(Op);
1969 // Canonicalize expressions of the following form:
1970 // x + (-Constant * y) -> x - (Constant * y)
1971 // x - (-Constant * y) -> x + (Constant * y)
1972 Instruction *Reassociate::canonicalizeNegConstExpr(Instruction *I) {
1973 if (!I->hasOneUse() || I->getType()->isVectorTy())
1976 // Must be a fmul or fdiv instruction.
1977 unsigned Opcode = I->getOpcode();
1978 if (Opcode != Instruction::FMul && Opcode != Instruction::FDiv)
1981 auto *C0 = dyn_cast<ConstantFP>(I->getOperand(0));
1982 auto *C1 = dyn_cast<ConstantFP>(I->getOperand(1));
1984 // Both operands are constant, let it get constant folded away.
1988 ConstantFP *CF = C0 ? C0 : C1;
1990 // Must have one constant operand.
1994 // Must be a negative ConstantFP.
1995 if (!CF->isNegative())
1998 // User must be a binary operator with one or more uses.
1999 Instruction *User = I->user_back();
2000 if (!isa<BinaryOperator>(User) || !User->hasNUsesOrMore(1))
2003 unsigned UserOpcode = User->getOpcode();
2004 if (UserOpcode != Instruction::FAdd && UserOpcode != Instruction::FSub)
2007 // Subtraction is not commutative. Explicitly, the following transform is
2008 // not valid: (-Constant * y) - x -> x + (Constant * y)
2009 if (!User->isCommutative() && User->getOperand(1) != I)
2012 // Change the sign of the constant.
2013 APFloat Val = CF->getValueAPF();
2015 I->setOperand(C0 ? 0 : 1, ConstantFP::get(CF->getContext(), Val));
2017 // Canonicalize I to RHS to simplify the next bit of logic. E.g.,
2018 // ((-Const*y) + x) -> (x + (-Const*y)).
2019 if (User->getOperand(0) == I && User->isCommutative())
2020 cast<BinaryOperator>(User)->swapOperands();
2022 Value *Op0 = User->getOperand(0);
2023 Value *Op1 = User->getOperand(1);
2025 switch (UserOpcode) {
2027 llvm_unreachable("Unexpected Opcode!");
2028 case Instruction::FAdd:
2029 NI = BinaryOperator::CreateFSub(Op0, Op1);
2030 NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
2032 case Instruction::FSub:
2033 NI = BinaryOperator::CreateFAdd(Op0, Op1);
2034 NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
2038 NI->insertBefore(User);
2039 NI->setName(User->getName());
2040 User->replaceAllUsesWith(NI);
2041 NI->setDebugLoc(I->getDebugLoc());
2042 RedoInsts.insert(I);
2047 /// Inspect and optimize the given instruction. Note that erasing
2048 /// instructions is not allowed.
2049 void Reassociate::OptimizeInst(Instruction *I) {
2050 // Only consider operations that we understand.
2051 if (!isa<BinaryOperator>(I))
2054 if (I->getOpcode() == Instruction::Shl && isa<ConstantInt>(I->getOperand(1)))
2055 // If an operand of this shift is a reassociable multiply, or if the shift
2056 // is used by a reassociable multiply or add, turn into a multiply.
2057 if (isReassociableOp(I->getOperand(0), Instruction::Mul) ||
2059 (isReassociableOp(I->user_back(), Instruction::Mul) ||
2060 isReassociableOp(I->user_back(), Instruction::Add)))) {
2061 Instruction *NI = ConvertShiftToMul(I);
2062 RedoInsts.insert(I);
2067 // Canonicalize negative constants out of expressions.
2068 if (Instruction *Res = canonicalizeNegConstExpr(I))
2071 // Commute binary operators, to canonicalize the order of their operands.
2072 // This can potentially expose more CSE opportunities, and makes writing other
2073 // transformations simpler.
2074 if (I->isCommutative())
2075 canonicalizeOperands(I);
2077 // TODO: We should optimize vector Xor instructions, but they are
2078 // currently unsupported.
2079 if (I->getType()->isVectorTy() && I->getOpcode() == Instruction::Xor)
2082 // Don't optimize floating point instructions that don't have unsafe algebra.
2083 if (I->getType()->isFPOrFPVectorTy() && !I->hasUnsafeAlgebra())
2086 // Do not reassociate boolean (i1) expressions. We want to preserve the
2087 // original order of evaluation for short-circuited comparisons that
2088 // SimplifyCFG has folded to AND/OR expressions. If the expression
2089 // is not further optimized, it is likely to be transformed back to a
2090 // short-circuited form for code gen, and the source order may have been
2091 // optimized for the most likely conditions.
2092 if (I->getType()->isIntegerTy(1))
2095 // If this is a subtract instruction which is not already in negate form,
2096 // see if we can convert it to X+-Y.
2097 if (I->getOpcode() == Instruction::Sub) {
2098 if (ShouldBreakUpSubtract(I)) {
2099 Instruction *NI = BreakUpSubtract(I, RedoInsts);
2100 RedoInsts.insert(I);
2103 } else if (BinaryOperator::isNeg(I)) {
2104 // Otherwise, this is a negation. See if the operand is a multiply tree
2105 // and if this is not an inner node of a multiply tree.
2106 if (isReassociableOp(I->getOperand(1), Instruction::Mul) &&
2108 !isReassociableOp(I->user_back(), Instruction::Mul))) {
2109 Instruction *NI = LowerNegateToMultiply(I);
2110 // If the negate was simplified, revisit the users to see if we can
2111 // reassociate further.
2112 for (User *U : NI->users()) {
2113 if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
2114 RedoInsts.insert(Tmp);
2116 RedoInsts.insert(I);
2121 } else if (I->getOpcode() == Instruction::FSub) {
2122 if (ShouldBreakUpSubtract(I)) {
2123 Instruction *NI = BreakUpSubtract(I, RedoInsts);
2124 RedoInsts.insert(I);
2127 } else if (BinaryOperator::isFNeg(I)) {
2128 // Otherwise, this is a negation. See if the operand is a multiply tree
2129 // and if this is not an inner node of a multiply tree.
2130 if (isReassociableOp(I->getOperand(1), Instruction::FMul) &&
2132 !isReassociableOp(I->user_back(), Instruction::FMul))) {
2133 // If the negate was simplified, revisit the users to see if we can
2134 // reassociate further.
2135 Instruction *NI = LowerNegateToMultiply(I);
2136 for (User *U : NI->users()) {
2137 if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
2138 RedoInsts.insert(Tmp);
2140 RedoInsts.insert(I);
2147 // If this instruction is an associative binary operator, process it.
2148 if (!I->isAssociative()) return;
2149 BinaryOperator *BO = cast<BinaryOperator>(I);
2151 // If this is an interior node of a reassociable tree, ignore it until we
2152 // get to the root of the tree, to avoid N^2 analysis.
2153 unsigned Opcode = BO->getOpcode();
2154 if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode) {
2155 // During the initial run we will get to the root of the tree.
2156 // But if we get here while we are redoing instructions, there is no
2157 // guarantee that the root will be visited. So Redo later
2158 if (BO->user_back() != BO &&
2159 BO->getParent() == BO->user_back()->getParent())
2160 RedoInsts.insert(BO->user_back());
2164 // If this is an add tree that is used by a sub instruction, ignore it
2165 // until we process the subtract.
2166 if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
2167 cast<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub)
2169 if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd &&
2170 cast<Instruction>(BO->user_back())->getOpcode() == Instruction::FSub)
2173 ReassociateExpression(BO);
2176 void Reassociate::ReassociateExpression(BinaryOperator *I) {
2177 // First, walk the expression tree, linearizing the tree, collecting the
2178 // operand information.
2179 SmallVector<RepeatedValue, 8> Tree;
2180 MadeChange |= LinearizeExprTree(I, Tree);
2181 SmallVector<ValueEntry, 8> Ops;
2182 Ops.reserve(Tree.size());
2183 for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
2184 RepeatedValue E = Tree[i];
2185 Ops.append(E.second.getZExtValue(),
2186 ValueEntry(getRank(E.first), E.first));
2189 DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
2191 // Now that we have linearized the tree to a list and have gathered all of
2192 // the operands and their ranks, sort the operands by their rank. Use a
2193 // stable_sort so that values with equal ranks will have their relative
2194 // positions maintained (and so the compiler is deterministic). Note that
2195 // this sorts so that the highest ranking values end up at the beginning of
2197 std::stable_sort(Ops.begin(), Ops.end());
2199 // Now that we have the expression tree in a convenient
2200 // sorted form, optimize it globally if possible.
2201 if (Value *V = OptimizeExpression(I, Ops)) {
2203 // Self-referential expression in unreachable code.
2205 // This expression tree simplified to something that isn't a tree,
2207 DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
2208 I->replaceAllUsesWith(V);
2209 if (Instruction *VI = dyn_cast<Instruction>(V))
2210 VI->setDebugLoc(I->getDebugLoc());
2211 RedoInsts.insert(I);
2216 // We want to sink immediates as deeply as possible except in the case where
2217 // this is a multiply tree used only by an add, and the immediate is a -1.
2218 // In this case we reassociate to put the negation on the outside so that we
2219 // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
2220 if (I->hasOneUse()) {
2221 if (I->getOpcode() == Instruction::Mul &&
2222 cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
2223 isa<ConstantInt>(Ops.back().Op) &&
2224 cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
2225 ValueEntry Tmp = Ops.pop_back_val();
2226 Ops.insert(Ops.begin(), Tmp);
2227 } else if (I->getOpcode() == Instruction::FMul &&
2228 cast<Instruction>(I->user_back())->getOpcode() ==
2229 Instruction::FAdd &&
2230 isa<ConstantFP>(Ops.back().Op) &&
2231 cast<ConstantFP>(Ops.back().Op)->isExactlyValue(-1.0)) {
2232 ValueEntry Tmp = Ops.pop_back_val();
2233 Ops.insert(Ops.begin(), Tmp);
2237 DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
2239 if (Ops.size() == 1) {
2241 // Self-referential expression in unreachable code.
2244 // This expression tree simplified to something that isn't a tree,
2246 I->replaceAllUsesWith(Ops[0].Op);
2247 if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
2248 OI->setDebugLoc(I->getDebugLoc());
2249 RedoInsts.insert(I);
2253 // Now that we ordered and optimized the expressions, splat them back into
2254 // the expression tree, removing any unneeded nodes.
2255 RewriteExprTree(I, Ops);
2258 bool Reassociate::runOnFunction(Function &F) {
2259 if (skipOptnoneFunction(F))
2262 // Calculate the rank map for F
2266 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
2267 // Optimize every instruction in the basic block.
2268 for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE; )
2269 if (isInstructionTriviallyDead(&*II)) {
2273 assert(II->getParent() == BI && "Moved to a different block!");
2277 // Make a copy of all the instructions to be redone so we can remove dead
2279 SetVector<AssertingVH<Instruction>> ToRedo(RedoInsts);
2280 // Iterate over all instructions to be reevaluated and remove trivially dead
2281 // instructions. If any operand of the trivially dead instruction becomes
2282 // dead mark it for deletion as well. Continue this process until all
2283 // trivially dead instructions have been removed.
2284 while (!ToRedo.empty()) {
2285 Instruction *I = ToRedo.pop_back_val();
2286 if (isInstructionTriviallyDead(I))
2287 RecursivelyEraseDeadInsts(I, ToRedo);
2290 // Now that we have removed dead instructions, we can reoptimize the
2291 // remaining instructions.
2292 while (!RedoInsts.empty()) {
2293 Instruction *I = RedoInsts.pop_back_val();
2294 if (isInstructionTriviallyDead(I))
2301 // We are done with the rank map.
2303 ValueRankMap.clear();