1 //===- Reassociate.cpp - Reassociate binary expressions -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass reassociates commutative expressions in an order that is designed
11 // to promote better constant propagation, GCSE, LICM, PRE, etc.
13 // For example: 4 + (x + 5) -> x + (4 + 5)
15 // In the implementation of this algorithm, constants are assigned rank = 0,
16 // function arguments are rank = 1, and other values are assigned ranks
17 // corresponding to the reverse post order traversal of current function
18 // (starting at 2), which effectively gives values in deep loops higher rank
19 // than values not in loops.
21 //===----------------------------------------------------------------------===//
23 #define DEBUG_TYPE "reassociate"
24 #include "llvm/Transforms/Scalar.h"
25 #include "llvm/ADT/DenseMap.h"
26 #include "llvm/ADT/PostOrderIterator.h"
27 #include "llvm/ADT/STLExtras.h"
28 #include "llvm/ADT/SetVector.h"
29 #include "llvm/ADT/Statistic.h"
30 #include "llvm/Assembly/Writer.h"
31 #include "llvm/IR/Constants.h"
32 #include "llvm/IR/DerivedTypes.h"
33 #include "llvm/IR/Function.h"
34 #include "llvm/IR/IRBuilder.h"
35 #include "llvm/IR/Instructions.h"
36 #include "llvm/IR/IntrinsicInst.h"
37 #include "llvm/Pass.h"
38 #include "llvm/Support/CFG.h"
39 #include "llvm/Support/Debug.h"
40 #include "llvm/Support/ValueHandle.h"
41 #include "llvm/Support/raw_ostream.h"
42 #include "llvm/Transforms/Utils/Local.h"
46 STATISTIC(NumChanged, "Number of insts reassociated");
47 STATISTIC(NumAnnihil, "Number of expr tree annihilated");
48 STATISTIC(NumFactor , "Number of multiplies factored");
54 ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {}
56 inline bool operator<(const ValueEntry &LHS, const ValueEntry &RHS) {
57 return LHS.Rank > RHS.Rank; // Sort so that highest rank goes to start.
62 /// PrintOps - Print out the expression identified in the Ops list.
64 static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
65 Module *M = I->getParent()->getParent()->getParent();
66 dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
67 << *Ops[0].Op->getType() << '\t';
68 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
70 WriteAsOperand(dbgs(), Ops[i].Op, false, M);
71 dbgs() << ", #" << Ops[i].Rank << "] ";
77 /// \brief Utility class representing a base and exponent pair which form one
78 /// factor of some product.
83 Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {}
85 /// \brief Sort factors by their Base.
87 bool operator()(const Factor &LHS, const Factor &RHS) {
88 return LHS.Base < RHS.Base;
92 /// \brief Compare factors for equal bases.
94 bool operator()(const Factor &LHS, const Factor &RHS) {
95 return LHS.Base == RHS.Base;
99 /// \brief Sort factors in descending order by their power.
100 struct PowerDescendingSorter {
101 bool operator()(const Factor &LHS, const Factor &RHS) {
102 return LHS.Power > RHS.Power;
106 /// \brief Compare factors for equal powers.
108 bool operator()(const Factor &LHS, const Factor &RHS) {
109 return LHS.Power == RHS.Power;
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"
125 const XorOpnd &operator=(const XorOpnd &That);
127 bool isInvalid() const { return SymbolicPart == 0; }
128 bool isOrExpr() const { return isOr; }
129 Value *getValue() const { return OrigVal; }
130 Value *getSymbolicPart() const { return SymbolicPart; }
131 unsigned getSymbolicRank() const { return SymbolicRank; }
132 const APInt &getConstPart() const { return ConstPart; }
134 void Invalidate() { SymbolicPart = OrigVal = 0; }
135 void setSymbolicRank(unsigned R) { SymbolicRank = R; }
137 // Sort the XorOpnd-Pointer in ascending order of symbolic-value-rank.
138 // The purpose is twofold:
139 // 1) Cluster together the operands sharing the same symbolic-value.
140 // 2) Operand having smaller symbolic-value-rank is permuted earlier, which
141 // could potentially shorten crital path, and expose more loop-invariants.
142 // Note that values' rank are basically defined in RPO order (FIXME).
143 // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
144 // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
145 // "z" in the order of X-Y-Z is better than any other orders.
146 class PtrSortFunctor {
150 PtrSortFunctor(ArrayRef<XorOpnd> Array) : A(Array) {}
151 bool operator()(unsigned LHSIndex, unsigned RHSIndex) {
152 return A[LHSIndex].getSymbolicRank() < A[RHSIndex].getSymbolicRank();
159 unsigned SymbolicRank;
165 class Reassociate : public FunctionPass {
166 DenseMap<BasicBlock*, unsigned> RankMap;
167 DenseMap<AssertingVH<Value>, unsigned> ValueRankMap;
168 SetVector<AssertingVH<Instruction> > RedoInsts;
171 static char ID; // Pass identification, replacement for typeid
172 Reassociate() : FunctionPass(ID) {
173 initializeReassociatePass(*PassRegistry::getPassRegistry());
176 bool runOnFunction(Function &F);
178 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
179 AU.setPreservesCFG();
182 void BuildRankMap(Function &F);
183 unsigned getRank(Value *V);
184 void ReassociateExpression(BinaryOperator *I);
185 void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
186 Value *OptimizeExpression(BinaryOperator *I,
187 SmallVectorImpl<ValueEntry> &Ops);
188 Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
189 Value *OptimizeXor(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
190 bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, APInt &ConstOpnd,
192 bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
193 APInt &ConstOpnd, Value *&Res);
194 bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
195 SmallVectorImpl<Factor> &Factors);
196 Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
197 SmallVectorImpl<Factor> &Factors);
198 Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
199 Value *RemoveFactorFromExpression(Value *V, Value *Factor);
200 void EraseInst(Instruction *I);
201 void OptimizeInst(Instruction *I);
205 XorOpnd::XorOpnd(Value *V) {
206 assert(!isa<ConstantInt>(V) && "No ConstantInt");
208 Instruction *I = dyn_cast<Instruction>(V);
211 if (I && (I->getOpcode() == Instruction::Or ||
212 I->getOpcode() == Instruction::And)) {
213 Value *V0 = I->getOperand(0);
214 Value *V1 = I->getOperand(1);
215 if (isa<ConstantInt>(V0))
218 if (ConstantInt *C = dyn_cast<ConstantInt>(V1)) {
219 ConstPart = C->getValue();
221 isOr = (I->getOpcode() == Instruction::Or);
226 // view the operand as "V | 0"
228 ConstPart = APInt::getNullValue(V->getType()->getIntegerBitWidth());
232 const XorOpnd &XorOpnd::operator=(const XorOpnd &That) {
233 OrigVal = That.OrigVal;
234 SymbolicPart = That.SymbolicPart;
235 ConstPart = That.ConstPart;
236 SymbolicRank = That.SymbolicRank;
241 char Reassociate::ID = 0;
242 INITIALIZE_PASS(Reassociate, "reassociate",
243 "Reassociate expressions", false, false)
245 // Public interface to the Reassociate pass
246 FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
248 /// isReassociableOp - Return true if V is an instruction of the specified
249 /// opcode and if it only has one use.
250 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
251 if (V->hasOneUse() && isa<Instruction>(V) &&
252 cast<Instruction>(V)->getOpcode() == Opcode)
253 return cast<BinaryOperator>(V);
257 static bool isUnmovableInstruction(Instruction *I) {
258 if (I->getOpcode() == Instruction::PHI ||
259 I->getOpcode() == Instruction::LandingPad ||
260 I->getOpcode() == Instruction::Alloca ||
261 I->getOpcode() == Instruction::Load ||
262 I->getOpcode() == Instruction::Invoke ||
263 (I->getOpcode() == Instruction::Call &&
264 !isa<DbgInfoIntrinsic>(I)) ||
265 I->getOpcode() == Instruction::UDiv ||
266 I->getOpcode() == Instruction::SDiv ||
267 I->getOpcode() == Instruction::FDiv ||
268 I->getOpcode() == Instruction::URem ||
269 I->getOpcode() == Instruction::SRem ||
270 I->getOpcode() == Instruction::FRem)
275 void Reassociate::BuildRankMap(Function &F) {
278 // Assign distinct ranks to function arguments
279 for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
280 ValueRankMap[&*I] = ++i;
282 ReversePostOrderTraversal<Function*> RPOT(&F);
283 for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
284 E = RPOT.end(); I != E; ++I) {
286 unsigned BBRank = RankMap[BB] = ++i << 16;
288 // Walk the basic block, adding precomputed ranks for any instructions that
289 // we cannot move. This ensures that the ranks for these instructions are
290 // all different in the block.
291 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
292 if (isUnmovableInstruction(I))
293 ValueRankMap[&*I] = ++BBRank;
297 unsigned Reassociate::getRank(Value *V) {
298 Instruction *I = dyn_cast<Instruction>(V);
300 if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
301 return 0; // Otherwise it's a global or constant, rank 0.
304 if (unsigned Rank = ValueRankMap[I])
305 return Rank; // Rank already known?
307 // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
308 // we can reassociate expressions for code motion! Since we do not recurse
309 // for PHI nodes, we cannot have infinite recursion here, because there
310 // cannot be loops in the value graph that do not go through PHI nodes.
311 unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
312 for (unsigned i = 0, e = I->getNumOperands();
313 i != e && Rank != MaxRank; ++i)
314 Rank = std::max(Rank, getRank(I->getOperand(i)));
316 // If this is a not or neg instruction, do not count it for rank. This
317 // assures us that X and ~X will have the same rank.
318 if (!I->getType()->isIntegerTy() ||
319 (!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I)))
322 //DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = "
325 return ValueRankMap[I] = Rank;
328 /// LowerNegateToMultiply - Replace 0-X with X*-1.
330 static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) {
331 Constant *Cst = Constant::getAllOnesValue(Neg->getType());
333 BinaryOperator *Res =
334 BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
335 Neg->setOperand(1, Constant::getNullValue(Neg->getType())); // Drop use of op.
337 Neg->replaceAllUsesWith(Res);
338 Res->setDebugLoc(Neg->getDebugLoc());
342 /// CarmichaelShift - Returns k such that lambda(2^Bitwidth) = 2^k, where lambda
343 /// is the Carmichael function. This means that x^(2^k) === 1 mod 2^Bitwidth for
344 /// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic.
345 /// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every
346 /// even x in Bitwidth-bit arithmetic.
347 static unsigned CarmichaelShift(unsigned Bitwidth) {
353 /// IncorporateWeight - Add the extra weight 'RHS' to the existing weight 'LHS',
354 /// reducing the combined weight using any special properties of the operation.
355 /// The existing weight LHS represents the computation X op X op ... op X where
356 /// X occurs LHS times. The combined weight represents X op X op ... op X with
357 /// X occurring LHS + RHS times. If op is "Xor" for example then the combined
358 /// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even;
359 /// the routine returns 1 in LHS in the first case, and 0 in LHS in the second.
360 static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) {
361 // If we were working with infinite precision arithmetic then the combined
362 // weight would be LHS + RHS. But we are using finite precision arithmetic,
363 // and the APInt sum LHS + RHS may not be correct if it wraps (it is correct
364 // for nilpotent operations and addition, but not for idempotent operations
365 // and multiplication), so it is important to correctly reduce the combined
366 // weight back into range if wrapping would be wrong.
368 // If RHS is zero then the weight didn't change.
369 if (RHS.isMinValue())
371 // If LHS is zero then the combined weight is RHS.
372 if (LHS.isMinValue()) {
376 // From this point on we know that neither LHS nor RHS is zero.
378 if (Instruction::isIdempotent(Opcode)) {
379 // Idempotent means X op X === X, so any non-zero weight is equivalent to a
380 // weight of 1. Keeping weights at zero or one also means that wrapping is
382 assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
383 return; // Return a weight of 1.
385 if (Instruction::isNilpotent(Opcode)) {
386 // Nilpotent means X op X === 0, so reduce weights modulo 2.
387 assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
388 LHS = 0; // 1 + 1 === 0 modulo 2.
391 if (Opcode == Instruction::Add) {
392 // TODO: Reduce the weight by exploiting nsw/nuw?
397 assert(Opcode == Instruction::Mul && "Unknown associative operation!");
398 unsigned Bitwidth = LHS.getBitWidth();
399 // If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth
400 // can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth
401 // bit number x, since either x is odd in which case x^CM = 1, or x is even in
402 // which case both x^W and x^(W - CM) are zero. By subtracting off multiples
403 // of CM like this weights can always be reduced to the range [0, CM+Bitwidth)
404 // which by a happy accident means that they can always be represented using
406 // TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than
407 // the Carmichael number).
409 /// CM - The value of Carmichael's lambda function.
410 APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth));
411 // Any weight W >= Threshold can be replaced with W - CM.
412 APInt Threshold = CM + Bitwidth;
413 assert(LHS.ult(Threshold) && RHS.ult(Threshold) && "Weights not reduced!");
414 // For Bitwidth 4 or more the following sum does not overflow.
416 while (LHS.uge(Threshold))
419 // To avoid problems with overflow do everything the same as above but using
421 unsigned CM = 1U << CarmichaelShift(Bitwidth);
422 unsigned Threshold = CM + Bitwidth;
423 assert(LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold &&
424 "Weights not reduced!");
425 unsigned Total = LHS.getZExtValue() + RHS.getZExtValue();
426 while (Total >= Threshold)
432 typedef std::pair<Value*, APInt> RepeatedValue;
434 /// LinearizeExprTree - Given an associative binary expression, return the leaf
435 /// nodes in Ops along with their weights (how many times the leaf occurs). The
436 /// original expression is the same as
437 /// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
439 /// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
443 /// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
445 /// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
447 /// This routine may modify the function, in which case it returns 'true'. The
448 /// changes it makes may well be destructive, changing the value computed by 'I'
449 /// to something completely different. Thus if the routine returns 'true' then
450 /// you MUST either replace I with a new expression computed from the Ops array,
451 /// or use RewriteExprTree to put the values back in.
453 /// A leaf node is either not a binary operation of the same kind as the root
454 /// node 'I' (i.e. is not a binary operator at all, or is, but with a different
455 /// opcode), or is the same kind of binary operator but has a use which either
456 /// does not belong to the expression, or does belong to the expression but is
457 /// a leaf node. Every leaf node has at least one use that is a non-leaf node
458 /// of the expression, while for non-leaf nodes (except for the root 'I') every
459 /// use is a non-leaf node of the expression.
462 /// expression graph node names
472 /// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
473 /// that order) (C, 1), (E, 1), (F, 2), (G, 2).
475 /// The expression is maximal: if some instruction is a binary operator of the
476 /// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
477 /// then the instruction also belongs to the expression, is not a leaf node of
478 /// it, and its operands also belong to the expression (but may be leaf nodes).
480 /// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
481 /// order to ensure that every non-root node in the expression has *exactly one*
482 /// use by a non-leaf node of the expression. This destruction means that the
483 /// caller MUST either replace 'I' with a new expression or use something like
484 /// RewriteExprTree to put the values back in if the routine indicates that it
485 /// made a change by returning 'true'.
487 /// In the above example either the right operand of A or the left operand of B
488 /// will be replaced by undef. If it is B's operand then this gives:
492 /// + + | A, B - operand of B replaced with undef
498 /// Note that such undef operands can only be reached by passing through 'I'.
499 /// For example, if you visit operands recursively starting from a leaf node
500 /// then you will never see such an undef operand unless you get back to 'I',
501 /// which requires passing through a phi node.
503 /// Note that this routine may also mutate binary operators of the wrong type
504 /// that have all uses inside the expression (i.e. only used by non-leaf nodes
505 /// of the expression) if it can turn them into binary operators of the right
506 /// type and thus make the expression bigger.
508 static bool LinearizeExprTree(BinaryOperator *I,
509 SmallVectorImpl<RepeatedValue> &Ops) {
510 DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
511 unsigned Bitwidth = I->getType()->getScalarType()->getPrimitiveSizeInBits();
512 unsigned Opcode = I->getOpcode();
513 assert(Instruction::isAssociative(Opcode) &&
514 Instruction::isCommutative(Opcode) &&
515 "Expected an associative and commutative operation!");
517 // Visit all operands of the expression, keeping track of their weight (the
518 // number of paths from the expression root to the operand, or if you like
519 // the number of times that operand occurs in the linearized expression).
520 // For example, if I = X + A, where X = A + B, then I, X and B have weight 1
521 // while A has weight two.
523 // Worklist of non-leaf nodes (their operands are in the expression too) along
524 // with their weights, representing a certain number of paths to the operator.
525 // If an operator occurs in the worklist multiple times then we found multiple
526 // ways to get to it.
527 SmallVector<std::pair<BinaryOperator*, APInt>, 8> Worklist; // (Op, Weight)
528 Worklist.push_back(std::make_pair(I, APInt(Bitwidth, 1)));
529 bool MadeChange = false;
531 // Leaves of the expression are values that either aren't the right kind of
532 // operation (eg: a constant, or a multiply in an add tree), or are, but have
533 // some uses that are not inside the expression. For example, in I = X + X,
534 // X = A + B, the value X has two uses (by I) that are in the expression. If
535 // X has any other uses, for example in a return instruction, then we consider
536 // X to be a leaf, and won't analyze it further. When we first visit a value,
537 // if it has more than one use then at first we conservatively consider it to
538 // be a leaf. Later, as the expression is explored, we may discover some more
539 // uses of the value from inside the expression. If all uses turn out to be
540 // from within the expression (and the value is a binary operator of the right
541 // kind) then the value is no longer considered to be a leaf, and its operands
544 // Leaves - Keeps track of the set of putative leaves as well as the number of
545 // paths to each leaf seen so far.
546 typedef DenseMap<Value*, APInt> LeafMap;
547 LeafMap Leaves; // Leaf -> Total weight so far.
548 SmallVector<Value*, 8> LeafOrder; // Ensure deterministic leaf output order.
551 SmallPtrSet<Value*, 8> Visited; // For sanity checking the iteration scheme.
553 while (!Worklist.empty()) {
554 std::pair<BinaryOperator*, APInt> P = Worklist.pop_back_val();
555 I = P.first; // We examine the operands of this binary operator.
557 for (unsigned OpIdx = 0; OpIdx < 2; ++OpIdx) { // Visit operands.
558 Value *Op = I->getOperand(OpIdx);
559 APInt Weight = P.second; // Number of paths to this operand.
560 DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n");
561 assert(!Op->use_empty() && "No uses, so how did we get to it?!");
563 // If this is a binary operation of the right kind with only one use then
564 // add its operands to the expression.
565 if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
566 assert(Visited.insert(Op) && "Not first visit!");
567 DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n");
568 Worklist.push_back(std::make_pair(BO, Weight));
572 // Appears to be a leaf. Is the operand already in the set of leaves?
573 LeafMap::iterator It = Leaves.find(Op);
574 if (It == Leaves.end()) {
575 // Not in the leaf map. Must be the first time we saw this operand.
576 assert(Visited.insert(Op) && "Not first visit!");
577 if (!Op->hasOneUse()) {
578 // This value has uses not accounted for by the expression, so it is
579 // not safe to modify. Mark it as being a leaf.
580 DEBUG(dbgs() << "ADD USES LEAF: " << *Op << " (" << Weight << ")\n");
581 LeafOrder.push_back(Op);
585 // No uses outside the expression, try morphing it.
586 } else if (It != Leaves.end()) {
587 // Already in the leaf map.
588 assert(Visited.count(Op) && "In leaf map but not visited!");
590 // Update the number of paths to the leaf.
591 IncorporateWeight(It->second, Weight, Opcode);
593 #if 0 // TODO: Re-enable once PR13021 is fixed.
594 // The leaf already has one use from inside the expression. As we want
595 // exactly one such use, drop this new use of the leaf.
596 assert(!Op->hasOneUse() && "Only one use, but we got here twice!");
597 I->setOperand(OpIdx, UndefValue::get(I->getType()));
600 // If the leaf is a binary operation of the right kind and we now see
601 // that its multiple original uses were in fact all by nodes belonging
602 // to the expression, then no longer consider it to be a leaf and add
603 // its operands to the expression.
604 if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
605 DEBUG(dbgs() << "UNLEAF: " << *Op << " (" << It->second << ")\n");
606 Worklist.push_back(std::make_pair(BO, It->second));
612 // If we still have uses that are not accounted for by the expression
613 // then it is not safe to modify the value.
614 if (!Op->hasOneUse())
617 // No uses outside the expression, try morphing it.
619 Leaves.erase(It); // Since the value may be morphed below.
622 // At this point we have a value which, first of all, is not a binary
623 // expression of the right kind, and secondly, is only used inside the
624 // expression. This means that it can safely be modified. See if we
625 // can usefully morph it into an expression of the right kind.
626 assert((!isa<Instruction>(Op) ||
627 cast<Instruction>(Op)->getOpcode() != Opcode) &&
628 "Should have been handled above!");
629 assert(Op->hasOneUse() && "Has uses outside the expression tree!");
631 // If this is a multiply expression, turn any internal negations into
632 // multiplies by -1 so they can be reassociated.
633 BinaryOperator *BO = dyn_cast<BinaryOperator>(Op);
634 if (Opcode == Instruction::Mul && BO && BinaryOperator::isNeg(BO)) {
635 DEBUG(dbgs() << "MORPH LEAF: " << *Op << " (" << Weight << ") TO ");
636 BO = LowerNegateToMultiply(BO);
637 DEBUG(dbgs() << *BO << 'n');
638 Worklist.push_back(std::make_pair(BO, Weight));
643 // Failed to morph into an expression of the right type. This really is
645 DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n");
646 assert(!isReassociableOp(Op, Opcode) && "Value was morphed?");
647 LeafOrder.push_back(Op);
652 // The leaves, repeated according to their weights, represent the linearized
653 // form of the expression.
654 for (unsigned i = 0, e = LeafOrder.size(); i != e; ++i) {
655 Value *V = LeafOrder[i];
656 LeafMap::iterator It = Leaves.find(V);
657 if (It == Leaves.end())
658 // Node initially thought to be a leaf wasn't.
660 assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!");
661 APInt Weight = It->second;
662 if (Weight.isMinValue())
663 // Leaf already output or weight reduction eliminated it.
665 // Ensure the leaf is only output once.
667 Ops.push_back(std::make_pair(V, Weight));
670 // For nilpotent operations or addition there may be no operands, for example
671 // because the expression was "X xor X" or consisted of 2^Bitwidth additions:
672 // in both cases the weight reduces to 0 causing the value to be skipped.
674 Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
675 assert(Identity && "Associative operation without identity!");
676 Ops.push_back(std::make_pair(Identity, APInt(Bitwidth, 1)));
682 // RewriteExprTree - Now that the operands for this expression tree are
683 // linearized and optimized, emit them in-order.
684 void Reassociate::RewriteExprTree(BinaryOperator *I,
685 SmallVectorImpl<ValueEntry> &Ops) {
686 assert(Ops.size() > 1 && "Single values should be used directly!");
688 // Since our optimizations should never increase the number of operations, the
689 // new expression can usually be written reusing the existing binary operators
690 // from the original expression tree, without creating any new instructions,
691 // though the rewritten expression may have a completely different topology.
692 // We take care to not change anything if the new expression will be the same
693 // as the original. If more than trivial changes (like commuting operands)
694 // were made then we are obliged to clear out any optional subclass data like
697 /// NodesToRewrite - Nodes from the original expression available for writing
698 /// the new expression into.
699 SmallVector<BinaryOperator*, 8> NodesToRewrite;
700 unsigned Opcode = I->getOpcode();
701 BinaryOperator *Op = I;
703 /// NotRewritable - The operands being written will be the leaves of the new
704 /// expression and must not be used as inner nodes (via NodesToRewrite) by
705 /// mistake. Inner nodes are always reassociable, and usually leaves are not
706 /// (if they were they would have been incorporated into the expression and so
707 /// would not be leaves), so most of the time there is no danger of this. But
708 /// in rare cases a leaf may become reassociable if an optimization kills uses
709 /// of it, or it may momentarily become reassociable during rewriting (below)
710 /// due it being removed as an operand of one of its uses. Ensure that misuse
711 /// of leaf nodes as inner nodes cannot occur by remembering all of the future
712 /// leaves and refusing to reuse any of them as inner nodes.
713 SmallPtrSet<Value*, 8> NotRewritable;
714 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
715 NotRewritable.insert(Ops[i].Op);
717 // ExpressionChanged - Non-null if the rewritten expression differs from the
718 // original in some non-trivial way, requiring the clearing of optional flags.
719 // Flags are cleared from the operator in ExpressionChanged up to I inclusive.
720 BinaryOperator *ExpressionChanged = 0;
721 for (unsigned i = 0; ; ++i) {
722 // The last operation (which comes earliest in the IR) is special as both
723 // operands will come from Ops, rather than just one with the other being
725 if (i+2 == Ops.size()) {
726 Value *NewLHS = Ops[i].Op;
727 Value *NewRHS = Ops[i+1].Op;
728 Value *OldLHS = Op->getOperand(0);
729 Value *OldRHS = Op->getOperand(1);
731 if (NewLHS == OldLHS && NewRHS == OldRHS)
732 // Nothing changed, leave it alone.
735 if (NewLHS == OldRHS && NewRHS == OldLHS) {
736 // The order of the operands was reversed. Swap them.
737 DEBUG(dbgs() << "RA: " << *Op << '\n');
739 DEBUG(dbgs() << "TO: " << *Op << '\n');
745 // The new operation differs non-trivially from the original. Overwrite
746 // the old operands with the new ones.
747 DEBUG(dbgs() << "RA: " << *Op << '\n');
748 if (NewLHS != OldLHS) {
749 BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
750 if (BO && !NotRewritable.count(BO))
751 NodesToRewrite.push_back(BO);
752 Op->setOperand(0, NewLHS);
754 if (NewRHS != OldRHS) {
755 BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
756 if (BO && !NotRewritable.count(BO))
757 NodesToRewrite.push_back(BO);
758 Op->setOperand(1, NewRHS);
760 DEBUG(dbgs() << "TO: " << *Op << '\n');
762 ExpressionChanged = Op;
769 // Not the last operation. The left-hand side will be a sub-expression
770 // while the right-hand side will be the current element of Ops.
771 Value *NewRHS = Ops[i].Op;
772 if (NewRHS != Op->getOperand(1)) {
773 DEBUG(dbgs() << "RA: " << *Op << '\n');
774 if (NewRHS == Op->getOperand(0)) {
775 // The new right-hand side was already present as the left operand. If
776 // we are lucky then swapping the operands will sort out both of them.
779 // Overwrite with the new right-hand side.
780 BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
781 if (BO && !NotRewritable.count(BO))
782 NodesToRewrite.push_back(BO);
783 Op->setOperand(1, NewRHS);
784 ExpressionChanged = Op;
786 DEBUG(dbgs() << "TO: " << *Op << '\n');
791 // Now deal with the left-hand side. If this is already an operation node
792 // from the original expression then just rewrite the rest of the expression
794 BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode);
795 if (BO && !NotRewritable.count(BO)) {
800 // Otherwise, grab a spare node from the original expression and use that as
801 // the left-hand side. If there are no nodes left then the optimizers made
802 // an expression with more nodes than the original! This usually means that
803 // they did something stupid but it might mean that the problem was just too
804 // hard (finding the mimimal number of multiplications needed to realize a
805 // multiplication expression is NP-complete). Whatever the reason, smart or
806 // stupid, create a new node if there are none left.
807 BinaryOperator *NewOp;
808 if (NodesToRewrite.empty()) {
809 Constant *Undef = UndefValue::get(I->getType());
810 NewOp = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
811 Undef, Undef, "", I);
813 NewOp = NodesToRewrite.pop_back_val();
816 DEBUG(dbgs() << "RA: " << *Op << '\n');
817 Op->setOperand(0, NewOp);
818 DEBUG(dbgs() << "TO: " << *Op << '\n');
819 ExpressionChanged = Op;
825 // If the expression changed non-trivially then clear out all subclass data
826 // starting from the operator specified in ExpressionChanged, and compactify
827 // the operators to just before the expression root to guarantee that the
828 // expression tree is dominated by all of Ops.
829 if (ExpressionChanged)
831 ExpressionChanged->clearSubclassOptionalData();
832 if (ExpressionChanged == I)
834 ExpressionChanged->moveBefore(I);
835 ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->use_begin());
838 // Throw away any left over nodes from the original expression.
839 for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)
840 RedoInsts.insert(NodesToRewrite[i]);
843 /// NegateValue - Insert instructions before the instruction pointed to by BI,
844 /// that computes the negative version of the value specified. The negative
845 /// version of the value is returned, and BI is left pointing at the instruction
846 /// that should be processed next by the reassociation pass.
847 static Value *NegateValue(Value *V, Instruction *BI) {
848 if (Constant *C = dyn_cast<Constant>(V))
849 return ConstantExpr::getNeg(C);
851 // We are trying to expose opportunity for reassociation. One of the things
852 // that we want to do to achieve this is to push a negation as deep into an
853 // expression chain as possible, to expose the add instructions. In practice,
854 // this means that we turn this:
855 // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
856 // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
857 // the constants. We assume that instcombine will clean up the mess later if
858 // we introduce tons of unnecessary negation instructions.
860 if (BinaryOperator *I = isReassociableOp(V, Instruction::Add)) {
861 // Push the negates through the add.
862 I->setOperand(0, NegateValue(I->getOperand(0), BI));
863 I->setOperand(1, NegateValue(I->getOperand(1), BI));
865 // We must move the add instruction here, because the neg instructions do
866 // not dominate the old add instruction in general. By moving it, we are
867 // assured that the neg instructions we just inserted dominate the
868 // instruction we are about to insert after them.
871 I->setName(I->getName()+".neg");
875 // Okay, we need to materialize a negated version of V with an instruction.
876 // Scan the use lists of V to see if we have one already.
877 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
879 if (!BinaryOperator::isNeg(U)) continue;
881 // We found one! Now we have to make sure that the definition dominates
882 // this use. We do this by moving it to the entry block (if it is a
883 // non-instruction value) or right after the definition. These negates will
884 // be zapped by reassociate later, so we don't need much finesse here.
885 BinaryOperator *TheNeg = cast<BinaryOperator>(U);
887 // Verify that the negate is in this function, V might be a constant expr.
888 if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
891 BasicBlock::iterator InsertPt;
892 if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
893 if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
894 InsertPt = II->getNormalDest()->begin();
896 InsertPt = InstInput;
899 while (isa<PHINode>(InsertPt)) ++InsertPt;
901 InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
903 TheNeg->moveBefore(InsertPt);
907 // Insert a 'neg' instruction that subtracts the value from zero to get the
909 return BinaryOperator::CreateNeg(V, V->getName() + ".neg", BI);
912 /// ShouldBreakUpSubtract - Return true if we should break up this subtract of
913 /// X-Y into (X + -Y).
914 static bool ShouldBreakUpSubtract(Instruction *Sub) {
915 // If this is a negation, we can't split it up!
916 if (BinaryOperator::isNeg(Sub))
919 // Don't bother to break this up unless either the LHS is an associable add or
920 // subtract or if this is only used by one.
921 if (isReassociableOp(Sub->getOperand(0), Instruction::Add) ||
922 isReassociableOp(Sub->getOperand(0), Instruction::Sub))
924 if (isReassociableOp(Sub->getOperand(1), Instruction::Add) ||
925 isReassociableOp(Sub->getOperand(1), Instruction::Sub))
927 if (Sub->hasOneUse() &&
928 (isReassociableOp(Sub->use_back(), Instruction::Add) ||
929 isReassociableOp(Sub->use_back(), Instruction::Sub)))
935 /// BreakUpSubtract - If we have (X-Y), and if either X is an add, or if this is
936 /// only used by an add, transform this into (X+(0-Y)) to promote better
938 static BinaryOperator *BreakUpSubtract(Instruction *Sub) {
939 // Convert a subtract into an add and a neg instruction. This allows sub
940 // instructions to be commuted with other add instructions.
942 // Calculate the negative value of Operand 1 of the sub instruction,
943 // and set it as the RHS of the add instruction we just made.
945 Value *NegVal = NegateValue(Sub->getOperand(1), Sub);
946 BinaryOperator *New =
947 BinaryOperator::CreateAdd(Sub->getOperand(0), NegVal, "", Sub);
948 Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op.
949 Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op.
952 // Everyone now refers to the add instruction.
953 Sub->replaceAllUsesWith(New);
954 New->setDebugLoc(Sub->getDebugLoc());
956 DEBUG(dbgs() << "Negated: " << *New << '\n');
960 /// ConvertShiftToMul - If this is a shift of a reassociable multiply or is used
961 /// by one, change this into a multiply by a constant to assist with further
963 static BinaryOperator *ConvertShiftToMul(Instruction *Shl) {
964 Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
965 MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
967 BinaryOperator *Mul =
968 BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
969 Shl->setOperand(0, UndefValue::get(Shl->getType())); // Drop use of op.
971 Shl->replaceAllUsesWith(Mul);
972 Mul->setDebugLoc(Shl->getDebugLoc());
976 /// FindInOperandList - Scan backwards and forwards among values with the same
977 /// rank as element i to see if X exists. If X does not exist, return i. This
978 /// is useful when scanning for 'x' when we see '-x' because they both get the
980 static unsigned FindInOperandList(SmallVectorImpl<ValueEntry> &Ops, unsigned i,
982 unsigned XRank = Ops[i].Rank;
983 unsigned e = Ops.size();
984 for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j)
988 for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j)
994 /// EmitAddTreeOfValues - Emit a tree of add instructions, summing Ops together
995 /// and returning the result. Insert the tree before I.
996 static Value *EmitAddTreeOfValues(Instruction *I,
997 SmallVectorImpl<WeakVH> &Ops){
998 if (Ops.size() == 1) return Ops.back();
1000 Value *V1 = Ops.back();
1002 Value *V2 = EmitAddTreeOfValues(I, Ops);
1003 return BinaryOperator::CreateAdd(V2, V1, "tmp", I);
1006 /// RemoveFactorFromExpression - If V is an expression tree that is a
1007 /// multiplication sequence, and if this sequence contains a multiply by Factor,
1008 /// remove Factor from the tree and return the new tree.
1009 Value *Reassociate::RemoveFactorFromExpression(Value *V, Value *Factor) {
1010 BinaryOperator *BO = isReassociableOp(V, Instruction::Mul);
1013 SmallVector<RepeatedValue, 8> Tree;
1014 MadeChange |= LinearizeExprTree(BO, Tree);
1015 SmallVector<ValueEntry, 8> Factors;
1016 Factors.reserve(Tree.size());
1017 for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
1018 RepeatedValue E = Tree[i];
1019 Factors.append(E.second.getZExtValue(),
1020 ValueEntry(getRank(E.first), E.first));
1023 bool FoundFactor = false;
1024 bool NeedsNegate = false;
1025 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1026 if (Factors[i].Op == Factor) {
1028 Factors.erase(Factors.begin()+i);
1032 // If this is a negative version of this factor, remove it.
1033 if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor))
1034 if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
1035 if (FC1->getValue() == -FC2->getValue()) {
1036 FoundFactor = NeedsNegate = true;
1037 Factors.erase(Factors.begin()+i);
1043 // Make sure to restore the operands to the expression tree.
1044 RewriteExprTree(BO, Factors);
1048 BasicBlock::iterator InsertPt = BO; ++InsertPt;
1050 // If this was just a single multiply, remove the multiply and return the only
1051 // remaining operand.
1052 if (Factors.size() == 1) {
1053 RedoInsts.insert(BO);
1056 RewriteExprTree(BO, Factors);
1061 V = BinaryOperator::CreateNeg(V, "neg", InsertPt);
1066 /// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively
1067 /// add its operands as factors, otherwise add V to the list of factors.
1069 /// Ops is the top-level list of add operands we're trying to factor.
1070 static void FindSingleUseMultiplyFactors(Value *V,
1071 SmallVectorImpl<Value*> &Factors,
1072 const SmallVectorImpl<ValueEntry> &Ops) {
1073 BinaryOperator *BO = isReassociableOp(V, Instruction::Mul);
1075 Factors.push_back(V);
1079 // Otherwise, add the LHS and RHS to the list of factors.
1080 FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops);
1081 FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops);
1084 /// OptimizeAndOrXor - Optimize a series of operands to an 'and', 'or', or 'xor'
1085 /// instruction. This optimizes based on identities. If it can be reduced to
1086 /// a single Value, it is returned, otherwise the Ops list is mutated as
1088 static Value *OptimizeAndOrXor(unsigned Opcode,
1089 SmallVectorImpl<ValueEntry> &Ops) {
1090 // Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
1091 // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
1092 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1093 // First, check for X and ~X in the operand list.
1094 assert(i < Ops.size());
1095 if (BinaryOperator::isNot(Ops[i].Op)) { // Cannot occur for ^.
1096 Value *X = BinaryOperator::getNotArgument(Ops[i].Op);
1097 unsigned FoundX = FindInOperandList(Ops, i, X);
1099 if (Opcode == Instruction::And) // ...&X&~X = 0
1100 return Constant::getNullValue(X->getType());
1102 if (Opcode == Instruction::Or) // ...|X|~X = -1
1103 return Constant::getAllOnesValue(X->getType());
1107 // Next, check for duplicate pairs of values, which we assume are next to
1108 // each other, due to our sorting criteria.
1109 assert(i < Ops.size());
1110 if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
1111 if (Opcode == Instruction::And || Opcode == Instruction::Or) {
1112 // Drop duplicate values for And and Or.
1113 Ops.erase(Ops.begin()+i);
1119 // Drop pairs of values for Xor.
1120 assert(Opcode == Instruction::Xor);
1122 return Constant::getNullValue(Ops[0].Op->getType());
1125 Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
1133 /// Helper funciton of CombineXorOpnd(). It creates a bitwise-and
1134 /// instruction with the given two operands, and return the resulting
1135 /// instruction. There are two special cases: 1) if the constant operand is 0,
1136 /// it will return NULL. 2) if the constant is ~0, the symbolic operand will
1138 static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd,
1139 const APInt &ConstOpnd) {
1140 if (ConstOpnd != 0) {
1141 if (!ConstOpnd.isAllOnesValue()) {
1142 LLVMContext &Ctx = Opnd->getType()->getContext();
1144 I = BinaryOperator::CreateAnd(Opnd, ConstantInt::get(Ctx, ConstOpnd),
1145 "and.ra", InsertBefore);
1146 I->setDebugLoc(InsertBefore->getDebugLoc());
1154 // Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
1155 // into "R ^ C", where C would be 0, and R is a symbolic value.
1157 // If it was successful, true is returned, and the "R" and "C" is returned
1158 // via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
1159 // and both "Res" and "ConstOpnd" remain unchanged.
1161 bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
1162 APInt &ConstOpnd, Value *&Res) {
1163 // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
1164 // = ((x | c1) ^ c1) ^ (c1 ^ c2)
1165 // = (x & ~c1) ^ (c1 ^ c2)
1166 // It is useful only when c1 == c2.
1167 if (Opnd1->isOrExpr() && Opnd1->getConstPart() != 0) {
1168 if (!Opnd1->getValue()->hasOneUse())
1171 const APInt &C1 = Opnd1->getConstPart();
1172 if (C1 != ConstOpnd)
1175 Value *X = Opnd1->getSymbolicPart();
1176 Res = createAndInstr(I, X, ~C1);
1177 // ConstOpnd was C2, now C1 ^ C2.
1180 if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1181 RedoInsts.insert(T);
1188 // Helper function of OptimizeXor(). It tries to simplify
1189 // "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
1192 // If it was successful, true is returned, and the "R" and "C" is returned
1193 // via "Res" and "ConstOpnd", respectively (If the entire expression is
1194 // evaluated to a constant, the Res is set to NULL); otherwise, false is
1195 // returned, and both "Res" and "ConstOpnd" remain unchanged.
1196 bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
1197 APInt &ConstOpnd, Value *&Res) {
1198 Value *X = Opnd1->getSymbolicPart();
1199 if (X != Opnd2->getSymbolicPart())
1202 const APInt &C1 = Opnd1->getConstPart();
1203 const APInt &C2 = Opnd2->getConstPart();
1205 // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
1206 int DeadInstNum = 1;
1207 if (Opnd1->getValue()->hasOneUse())
1209 if (Opnd2->getValue()->hasOneUse())
1213 // (x | c1) ^ (x & c2)
1214 // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
1215 // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
1216 // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
1218 if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
1219 if (Opnd2->isOrExpr())
1220 std::swap(Opnd1, Opnd2);
1222 APInt C3((~C1) ^ C2);
1224 // Do not increase code size!
1225 if (C3 != 0 && !C3.isAllOnesValue()) {
1226 int NewInstNum = ConstOpnd != 0 ? 1 : 2;
1227 if (NewInstNum > DeadInstNum)
1231 Res = createAndInstr(I, X, C3);
1234 } else if (Opnd1->isOrExpr()) {
1235 // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
1239 // Do not increase code size
1240 if (C3 != 0 && !C3.isAllOnesValue()) {
1241 int NewInstNum = ConstOpnd != 0 ? 1 : 2;
1242 if (NewInstNum > DeadInstNum)
1246 Res = createAndInstr(I, X, C3);
1249 // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
1252 Res = createAndInstr(I, X, C3);
1255 // Put the original operands in the Redo list; hope they will be deleted
1257 if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1258 RedoInsts.insert(T);
1259 if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
1260 RedoInsts.insert(T);
1265 /// Optimize a series of operands to an 'xor' instruction. If it can be reduced
1266 /// to a single Value, it is returned, otherwise the Ops list is mutated as
1268 Value *Reassociate::OptimizeXor(Instruction *I,
1269 SmallVectorImpl<ValueEntry> &Ops) {
1270 if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
1273 if (Ops.size() == 1)
1276 SmallVector<XorOpnd, 8> Opnds;
1277 SmallVector<unsigned, 8> OpndIndices;
1278 Type *Ty = Ops[0].Op->getType();
1279 APInt ConstOpnd(Ty->getIntegerBitWidth(), 0);
1281 // Step 1: Convert ValueEntry to XorOpnd
1282 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1283 Value *V = Ops[i].Op;
1284 if (!isa<ConstantInt>(V)) {
1286 O.setSymbolicRank(getRank(O.getSymbolicPart()));
1288 OpndIndices.push_back(Opnds.size() - 1);
1290 ConstOpnd ^= cast<ConstantInt>(V)->getValue();
1293 // Step 2: Sort the Xor-Operands in a way such that the operands containing
1294 // the same symbolic value cluster together. For instance, the input operand
1295 // sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
1296 // ("x | 123", "x & 789", "y & 456").
1297 std::sort(OpndIndices.begin(), OpndIndices.end(),
1298 XorOpnd::PtrSortFunctor(Opnds));
1300 // Step 3: Combine adjacent operands
1301 XorOpnd *PrevOpnd = 0;
1302 bool Changed = false;
1303 for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
1304 XorOpnd *CurrOpnd = &Opnds[OpndIndices[i]];
1305 // The combined value
1308 // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
1309 if (ConstOpnd != 0 && CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
1312 *CurrOpnd = XorOpnd(CV);
1314 CurrOpnd->Invalidate();
1319 if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
1320 PrevOpnd = CurrOpnd;
1324 // step 3.2: When previous and current operands share the same symbolic
1325 // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
1327 if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
1328 // Remove previous operand
1329 PrevOpnd->Invalidate();
1331 *CurrOpnd = XorOpnd(CV);
1332 PrevOpnd = CurrOpnd;
1334 CurrOpnd->Invalidate();
1341 // Step 4: Reassemble the Ops
1344 for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
1345 XorOpnd &O = Opnds[i];
1348 ValueEntry VE(getRank(O.getValue()), O.getValue());
1351 if (ConstOpnd != 0) {
1352 Value *C = ConstantInt::get(Ty->getContext(), ConstOpnd);
1353 ValueEntry VE(getRank(C), C);
1356 int Sz = Ops.size();
1358 return Ops.back().Op;
1360 assert(ConstOpnd == 0);
1361 return ConstantInt::get(Ty->getContext(), ConstOpnd);
1368 /// OptimizeAdd - Optimize a series of operands to an 'add' instruction. This
1369 /// optimizes based on identities. If it can be reduced to a single Value, it
1370 /// is returned, otherwise the Ops list is mutated as necessary.
1371 Value *Reassociate::OptimizeAdd(Instruction *I,
1372 SmallVectorImpl<ValueEntry> &Ops) {
1373 // Scan the operand lists looking for X and -X pairs. If we find any, we
1374 // can simplify the expression. X+-X == 0. While we're at it, scan for any
1375 // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
1377 // TODO: We could handle "X + ~X" -> "-1" if we wanted, since "-X = ~X+1".
1379 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1380 Value *TheOp = Ops[i].Op;
1381 // Check to see if we've seen this operand before. If so, we factor all
1382 // instances of the operand together. Due to our sorting criteria, we know
1383 // that these need to be next to each other in the vector.
1384 if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
1385 // Rescan the list, remove all instances of this operand from the expr.
1386 unsigned NumFound = 0;
1388 Ops.erase(Ops.begin()+i);
1390 } while (i != Ops.size() && Ops[i].Op == TheOp);
1392 DEBUG(errs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n');
1395 // Insert a new multiply.
1396 Value *Mul = ConstantInt::get(cast<IntegerType>(I->getType()), NumFound);
1397 Mul = BinaryOperator::CreateMul(TheOp, Mul, "factor", I);
1399 // Now that we have inserted a multiply, optimize it. This allows us to
1400 // handle cases that require multiple factoring steps, such as this:
1401 // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
1402 RedoInsts.insert(cast<Instruction>(Mul));
1404 // If every add operand was a duplicate, return the multiply.
1408 // Otherwise, we had some input that didn't have the dupe, such as
1409 // "A + A + B" -> "A*2 + B". Add the new multiply to the list of
1410 // things being added by this operation.
1411 Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
1418 // Check for X and -X in the operand list.
1419 if (!BinaryOperator::isNeg(TheOp))
1422 Value *X = BinaryOperator::getNegArgument(TheOp);
1423 unsigned FoundX = FindInOperandList(Ops, i, X);
1427 // Remove X and -X from the operand list.
1428 if (Ops.size() == 2)
1429 return Constant::getNullValue(X->getType());
1431 Ops.erase(Ops.begin()+i);
1435 --i; // Need to back up an extra one.
1436 Ops.erase(Ops.begin()+FoundX);
1438 --i; // Revisit element.
1439 e -= 2; // Removed two elements.
1442 // Scan the operand list, checking to see if there are any common factors
1443 // between operands. Consider something like A*A+A*B*C+D. We would like to
1444 // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
1445 // To efficiently find this, we count the number of times a factor occurs
1446 // for any ADD operands that are MULs.
1447 DenseMap<Value*, unsigned> FactorOccurrences;
1449 // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
1450 // where they are actually the same multiply.
1451 unsigned MaxOcc = 0;
1452 Value *MaxOccVal = 0;
1453 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1454 BinaryOperator *BOp = isReassociableOp(Ops[i].Op, Instruction::Mul);
1458 // Compute all of the factors of this added value.
1459 SmallVector<Value*, 8> Factors;
1460 FindSingleUseMultiplyFactors(BOp, Factors, Ops);
1461 assert(Factors.size() > 1 && "Bad linearize!");
1463 // Add one to FactorOccurrences for each unique factor in this op.
1464 SmallPtrSet<Value*, 8> Duplicates;
1465 for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1466 Value *Factor = Factors[i];
1467 if (!Duplicates.insert(Factor)) continue;
1469 unsigned Occ = ++FactorOccurrences[Factor];
1470 if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factor; }
1472 // If Factor is a negative constant, add the negated value as a factor
1473 // because we can percolate the negate out. Watch for minint, which
1474 // cannot be positivified.
1475 if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor))
1476 if (CI->isNegative() && !CI->isMinValue(true)) {
1477 Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
1478 assert(!Duplicates.count(Factor) &&
1479 "Shouldn't have two constant factors, missed a canonicalize");
1481 unsigned Occ = ++FactorOccurrences[Factor];
1482 if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factor; }
1487 // If any factor occurred more than one time, we can pull it out.
1489 DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
1492 // Create a new instruction that uses the MaxOccVal twice. If we don't do
1493 // this, we could otherwise run into situations where removing a factor
1494 // from an expression will drop a use of maxocc, and this can cause
1495 // RemoveFactorFromExpression on successive values to behave differently.
1496 Instruction *DummyInst = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal);
1497 SmallVector<WeakVH, 4> NewMulOps;
1498 for (unsigned i = 0; i != Ops.size(); ++i) {
1499 // Only try to remove factors from expressions we're allowed to.
1500 BinaryOperator *BOp = isReassociableOp(Ops[i].Op, Instruction::Mul);
1504 if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
1505 // The factorized operand may occur several times. Convert them all in
1507 for (unsigned j = Ops.size(); j != i;) {
1509 if (Ops[j].Op == Ops[i].Op) {
1510 NewMulOps.push_back(V);
1511 Ops.erase(Ops.begin()+j);
1518 // No need for extra uses anymore.
1521 unsigned NumAddedValues = NewMulOps.size();
1522 Value *V = EmitAddTreeOfValues(I, NewMulOps);
1524 // Now that we have inserted the add tree, optimize it. This allows us to
1525 // handle cases that require multiple factoring steps, such as this:
1526 // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
1527 assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
1528 (void)NumAddedValues;
1529 if (Instruction *VI = dyn_cast<Instruction>(V))
1530 RedoInsts.insert(VI);
1532 // Create the multiply.
1533 Instruction *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
1535 // Rerun associate on the multiply in case the inner expression turned into
1536 // a multiply. We want to make sure that we keep things in canonical form.
1537 RedoInsts.insert(V2);
1539 // If every add operand included the factor (e.g. "A*B + A*C"), then the
1540 // entire result expression is just the multiply "A*(B+C)".
1544 // Otherwise, we had some input that didn't have the factor, such as
1545 // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
1546 // things being added by this operation.
1547 Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
1554 /// \brief Predicate tests whether a ValueEntry's op is in a map.
1555 struct IsValueInMap {
1556 const DenseMap<Value *, unsigned> ⤅
1558 IsValueInMap(const DenseMap<Value *, unsigned> &Map) : Map(Map) {}
1560 bool operator()(const ValueEntry &Entry) {
1561 return Map.find(Entry.Op) != Map.end();
1566 /// \brief Build up a vector of value/power pairs factoring a product.
1568 /// Given a series of multiplication operands, build a vector of factors and
1569 /// the powers each is raised to when forming the final product. Sort them in
1570 /// the order of descending power.
1572 /// (x*x) -> [(x, 2)]
1573 /// ((x*x)*x) -> [(x, 3)]
1574 /// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
1576 /// \returns Whether any factors have a power greater than one.
1577 bool Reassociate::collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
1578 SmallVectorImpl<Factor> &Factors) {
1579 // FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this.
1580 // Compute the sum of powers of simplifiable factors.
1581 unsigned FactorPowerSum = 0;
1582 for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) {
1583 Value *Op = Ops[Idx-1].Op;
1585 // Count the number of occurrences of this value.
1587 for (; Idx < Size && Ops[Idx].Op == Op; ++Idx)
1589 // Track for simplification all factors which occur 2 or more times.
1591 FactorPowerSum += Count;
1594 // We can only simplify factors if the sum of the powers of our simplifiable
1595 // factors is 4 or higher. When that is the case, we will *always* have
1596 // a simplification. This is an important invariant to prevent cyclicly
1597 // trying to simplify already minimal formations.
1598 if (FactorPowerSum < 4)
1601 // Now gather the simplifiable factors, removing them from Ops.
1603 for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) {
1604 Value *Op = Ops[Idx-1].Op;
1606 // Count the number of occurrences of this value.
1608 for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx)
1612 // Move an even number of occurrences to Factors.
1615 FactorPowerSum += Count;
1616 Factors.push_back(Factor(Op, Count));
1617 Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count);
1620 // None of the adjustments above should have reduced the sum of factor powers
1621 // below our mininum of '4'.
1622 assert(FactorPowerSum >= 4);
1624 std::sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter());
1628 /// \brief Build a tree of multiplies, computing the product of Ops.
1629 static Value *buildMultiplyTree(IRBuilder<> &Builder,
1630 SmallVectorImpl<Value*> &Ops) {
1631 if (Ops.size() == 1)
1634 Value *LHS = Ops.pop_back_val();
1636 LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
1637 } while (!Ops.empty());
1642 /// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
1644 /// Given a vector of values raised to various powers, where no two values are
1645 /// equal and the powers are sorted in decreasing order, compute the minimal
1646 /// DAG of multiplies to compute the final product, and return that product
1648 Value *Reassociate::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
1649 SmallVectorImpl<Factor> &Factors) {
1650 assert(Factors[0].Power);
1651 SmallVector<Value *, 4> OuterProduct;
1652 for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
1653 Idx < Size && Factors[Idx].Power > 0; ++Idx) {
1654 if (Factors[Idx].Power != Factors[LastIdx].Power) {
1659 // We want to multiply across all the factors with the same power so that
1660 // we can raise them to that power as a single entity. Build a mini tree
1662 SmallVector<Value *, 4> InnerProduct;
1663 InnerProduct.push_back(Factors[LastIdx].Base);
1665 InnerProduct.push_back(Factors[Idx].Base);
1667 } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
1669 // Reset the base value of the first factor to the new expression tree.
1670 // We'll remove all the factors with the same power in a second pass.
1671 Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
1672 if (Instruction *MI = dyn_cast<Instruction>(M))
1673 RedoInsts.insert(MI);
1677 // Unique factors with equal powers -- we've folded them into the first one's
1679 Factors.erase(std::unique(Factors.begin(), Factors.end(),
1680 Factor::PowerEqual()),
1683 // Iteratively collect the base of each factor with an add power into the
1684 // outer product, and halve each power in preparation for squaring the
1686 for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
1687 if (Factors[Idx].Power & 1)
1688 OuterProduct.push_back(Factors[Idx].Base);
1689 Factors[Idx].Power >>= 1;
1691 if (Factors[0].Power) {
1692 Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
1693 OuterProduct.push_back(SquareRoot);
1694 OuterProduct.push_back(SquareRoot);
1696 if (OuterProduct.size() == 1)
1697 return OuterProduct.front();
1699 Value *V = buildMultiplyTree(Builder, OuterProduct);
1703 Value *Reassociate::OptimizeMul(BinaryOperator *I,
1704 SmallVectorImpl<ValueEntry> &Ops) {
1705 // We can only optimize the multiplies when there is a chain of more than
1706 // three, such that a balanced tree might require fewer total multiplies.
1710 // Try to turn linear trees of multiplies without other uses of the
1711 // intermediate stages into minimal multiply DAGs with perfect sub-expression
1713 SmallVector<Factor, 4> Factors;
1714 if (!collectMultiplyFactors(Ops, Factors))
1715 return 0; // All distinct factors, so nothing left for us to do.
1717 IRBuilder<> Builder(I);
1718 Value *V = buildMinimalMultiplyDAG(Builder, Factors);
1722 ValueEntry NewEntry = ValueEntry(getRank(V), V);
1723 Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry);
1727 Value *Reassociate::OptimizeExpression(BinaryOperator *I,
1728 SmallVectorImpl<ValueEntry> &Ops) {
1729 // Now that we have the linearized expression tree, try to optimize it.
1730 // Start by folding any constants that we found.
1732 unsigned Opcode = I->getOpcode();
1733 while (!Ops.empty() && isa<Constant>(Ops.back().Op)) {
1734 Constant *C = cast<Constant>(Ops.pop_back_val().Op);
1735 Cst = Cst ? ConstantExpr::get(Opcode, C, Cst) : C;
1737 // If there was nothing but constants then we are done.
1741 // Put the combined constant back at the end of the operand list, except if
1742 // there is no point. For example, an add of 0 gets dropped here, while a
1743 // multiplication by zero turns the whole expression into zero.
1744 if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) {
1745 if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType()))
1747 Ops.push_back(ValueEntry(0, Cst));
1750 if (Ops.size() == 1) return Ops[0].Op;
1752 // Handle destructive annihilation due to identities between elements in the
1753 // argument list here.
1754 unsigned NumOps = Ops.size();
1757 case Instruction::And:
1758 case Instruction::Or:
1759 if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
1763 case Instruction::Xor:
1764 if (Value *Result = OptimizeXor(I, Ops))
1768 case Instruction::Add:
1769 if (Value *Result = OptimizeAdd(I, Ops))
1773 case Instruction::Mul:
1774 if (Value *Result = OptimizeMul(I, Ops))
1779 if (Ops.size() != NumOps)
1780 return OptimizeExpression(I, Ops);
1784 /// EraseInst - Zap the given instruction, adding interesting operands to the
1786 void Reassociate::EraseInst(Instruction *I) {
1787 assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
1788 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
1789 // Erase the dead instruction.
1790 ValueRankMap.erase(I);
1791 RedoInsts.remove(I);
1792 I->eraseFromParent();
1793 // Optimize its operands.
1794 SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
1795 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1796 if (Instruction *Op = dyn_cast<Instruction>(Ops[i])) {
1797 // If this is a node in an expression tree, climb to the expression root
1798 // and add that since that's where optimization actually happens.
1799 unsigned Opcode = Op->getOpcode();
1800 while (Op->hasOneUse() && Op->use_back()->getOpcode() == Opcode &&
1802 Op = Op->use_back();
1803 RedoInsts.insert(Op);
1807 /// OptimizeInst - Inspect and optimize the given instruction. Note that erasing
1808 /// instructions is not allowed.
1809 void Reassociate::OptimizeInst(Instruction *I) {
1810 // Only consider operations that we understand.
1811 if (!isa<BinaryOperator>(I))
1814 if (I->getOpcode() == Instruction::Shl &&
1815 isa<ConstantInt>(I->getOperand(1)))
1816 // If an operand of this shift is a reassociable multiply, or if the shift
1817 // is used by a reassociable multiply or add, turn into a multiply.
1818 if (isReassociableOp(I->getOperand(0), Instruction::Mul) ||
1820 (isReassociableOp(I->use_back(), Instruction::Mul) ||
1821 isReassociableOp(I->use_back(), Instruction::Add)))) {
1822 Instruction *NI = ConvertShiftToMul(I);
1823 RedoInsts.insert(I);
1828 // Floating point binary operators are not associative, but we can still
1829 // commute (some) of them, to canonicalize the order of their operands.
1830 // This can potentially expose more CSE opportunities, and makes writing
1831 // other transformations simpler.
1832 if ((I->getType()->isFloatingPointTy() || I->getType()->isVectorTy())) {
1833 // FAdd and FMul can be commuted.
1834 if (I->getOpcode() != Instruction::FMul &&
1835 I->getOpcode() != Instruction::FAdd)
1838 Value *LHS = I->getOperand(0);
1839 Value *RHS = I->getOperand(1);
1840 unsigned LHSRank = getRank(LHS);
1841 unsigned RHSRank = getRank(RHS);
1843 // Sort the operands by rank.
1844 if (RHSRank < LHSRank) {
1845 I->setOperand(0, RHS);
1846 I->setOperand(1, LHS);
1852 // Do not reassociate boolean (i1) expressions. We want to preserve the
1853 // original order of evaluation for short-circuited comparisons that
1854 // SimplifyCFG has folded to AND/OR expressions. If the expression
1855 // is not further optimized, it is likely to be transformed back to a
1856 // short-circuited form for code gen, and the source order may have been
1857 // optimized for the most likely conditions.
1858 if (I->getType()->isIntegerTy(1))
1861 // If this is a subtract instruction which is not already in negate form,
1862 // see if we can convert it to X+-Y.
1863 if (I->getOpcode() == Instruction::Sub) {
1864 if (ShouldBreakUpSubtract(I)) {
1865 Instruction *NI = BreakUpSubtract(I);
1866 RedoInsts.insert(I);
1869 } else if (BinaryOperator::isNeg(I)) {
1870 // Otherwise, this is a negation. See if the operand is a multiply tree
1871 // and if this is not an inner node of a multiply tree.
1872 if (isReassociableOp(I->getOperand(1), Instruction::Mul) &&
1874 !isReassociableOp(I->use_back(), Instruction::Mul))) {
1875 Instruction *NI = LowerNegateToMultiply(I);
1876 RedoInsts.insert(I);
1883 // If this instruction is an associative binary operator, process it.
1884 if (!I->isAssociative()) return;
1885 BinaryOperator *BO = cast<BinaryOperator>(I);
1887 // If this is an interior node of a reassociable tree, ignore it until we
1888 // get to the root of the tree, to avoid N^2 analysis.
1889 unsigned Opcode = BO->getOpcode();
1890 if (BO->hasOneUse() && BO->use_back()->getOpcode() == Opcode)
1893 // If this is an add tree that is used by a sub instruction, ignore it
1894 // until we process the subtract.
1895 if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
1896 cast<Instruction>(BO->use_back())->getOpcode() == Instruction::Sub)
1899 ReassociateExpression(BO);
1902 void Reassociate::ReassociateExpression(BinaryOperator *I) {
1904 // First, walk the expression tree, linearizing the tree, collecting the
1905 // operand information.
1906 SmallVector<RepeatedValue, 8> Tree;
1907 MadeChange |= LinearizeExprTree(I, Tree);
1908 SmallVector<ValueEntry, 8> Ops;
1909 Ops.reserve(Tree.size());
1910 for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
1911 RepeatedValue E = Tree[i];
1912 Ops.append(E.second.getZExtValue(),
1913 ValueEntry(getRank(E.first), E.first));
1916 DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
1918 // Now that we have linearized the tree to a list and have gathered all of
1919 // the operands and their ranks, sort the operands by their rank. Use a
1920 // stable_sort so that values with equal ranks will have their relative
1921 // positions maintained (and so the compiler is deterministic). Note that
1922 // this sorts so that the highest ranking values end up at the beginning of
1924 std::stable_sort(Ops.begin(), Ops.end());
1926 // OptimizeExpression - Now that we have the expression tree in a convenient
1927 // sorted form, optimize it globally if possible.
1928 if (Value *V = OptimizeExpression(I, Ops)) {
1930 // Self-referential expression in unreachable code.
1932 // This expression tree simplified to something that isn't a tree,
1934 DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
1935 I->replaceAllUsesWith(V);
1936 if (Instruction *VI = dyn_cast<Instruction>(V))
1937 VI->setDebugLoc(I->getDebugLoc());
1938 RedoInsts.insert(I);
1943 // We want to sink immediates as deeply as possible except in the case where
1944 // this is a multiply tree used only by an add, and the immediate is a -1.
1945 // In this case we reassociate to put the negation on the outside so that we
1946 // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
1947 if (I->getOpcode() == Instruction::Mul && I->hasOneUse() &&
1948 cast<Instruction>(I->use_back())->getOpcode() == Instruction::Add &&
1949 isa<ConstantInt>(Ops.back().Op) &&
1950 cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
1951 ValueEntry Tmp = Ops.pop_back_val();
1952 Ops.insert(Ops.begin(), Tmp);
1955 DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
1957 if (Ops.size() == 1) {
1959 // Self-referential expression in unreachable code.
1962 // This expression tree simplified to something that isn't a tree,
1964 I->replaceAllUsesWith(Ops[0].Op);
1965 if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
1966 OI->setDebugLoc(I->getDebugLoc());
1967 RedoInsts.insert(I);
1971 // Now that we ordered and optimized the expressions, splat them back into
1972 // the expression tree, removing any unneeded nodes.
1973 RewriteExprTree(I, Ops);
1976 bool Reassociate::runOnFunction(Function &F) {
1977 // Calculate the rank map for F
1981 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
1982 // Optimize every instruction in the basic block.
1983 for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE; )
1984 if (isInstructionTriviallyDead(II)) {
1988 assert(II->getParent() == BI && "Moved to a different block!");
1992 // If this produced extra instructions to optimize, handle them now.
1993 while (!RedoInsts.empty()) {
1994 Instruction *I = RedoInsts.pop_back_val();
1995 if (isInstructionTriviallyDead(I))
2002 // We are done with the rank map.
2004 ValueRankMap.clear();