LLVM  7.0.0svn
Reassociate.cpp
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1 //===- Reassociate.cpp - Reassociate binary expressions -------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass reassociates commutative expressions in an order that is designed
11 // to promote better constant propagation, GCSE, LICM, PRE, etc.
12 //
13 // For example: 4 + (x + 5) -> x + (4 + 5)
14 //
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.
20 //
21 //===----------------------------------------------------------------------===//
22 
24 #include "llvm/ADT/APFloat.h"
25 #include "llvm/ADT/APInt.h"
26 #include "llvm/ADT/DenseMap.h"
28 #include "llvm/ADT/SetVector.h"
29 #include "llvm/ADT/SmallPtrSet.h"
30 #include "llvm/ADT/SmallSet.h"
31 #include "llvm/ADT/SmallVector.h"
32 #include "llvm/ADT/Statistic.h"
35 #include "llvm/IR/Argument.h"
36 #include "llvm/IR/BasicBlock.h"
37 #include "llvm/IR/CFG.h"
38 #include "llvm/IR/Constant.h"
39 #include "llvm/IR/Constants.h"
40 #include "llvm/IR/Function.h"
41 #include "llvm/IR/IRBuilder.h"
42 #include "llvm/IR/InstrTypes.h"
43 #include "llvm/IR/Instruction.h"
44 #include "llvm/IR/Instructions.h"
45 #include "llvm/IR/Operator.h"
46 #include "llvm/IR/PassManager.h"
47 #include "llvm/IR/PatternMatch.h"
48 #include "llvm/IR/Type.h"
49 #include "llvm/IR/User.h"
50 #include "llvm/IR/Value.h"
51 #include "llvm/IR/ValueHandle.h"
52 #include "llvm/Pass.h"
53 #include "llvm/Support/Casting.h"
54 #include "llvm/Support/Debug.h"
57 #include "llvm/Transforms/Scalar.h"
59 #include <algorithm>
60 #include <cassert>
61 #include <utility>
62 
63 using namespace llvm;
64 using namespace reassociate;
65 
66 #define DEBUG_TYPE "reassociate"
67 
68 STATISTIC(NumChanged, "Number of insts reassociated");
69 STATISTIC(NumAnnihil, "Number of expr tree annihilated");
70 STATISTIC(NumFactor , "Number of multiplies factored");
71 
72 #ifndef NDEBUG
73 /// Print out the expression identified in the Ops list.
75  Module *M = I->getModule();
76  dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
77  << *Ops[0].Op->getType() << '\t';
78  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
79  dbgs() << "[ ";
80  Ops[i].Op->printAsOperand(dbgs(), false, M);
81  dbgs() << ", #" << Ops[i].Rank << "] ";
82  }
83 }
84 #endif
85 
86 /// Utility class representing a non-constant Xor-operand. We classify
87 /// non-constant Xor-Operands into two categories:
88 /// C1) The operand is in the form "X & C", where C is a constant and C != ~0
89 /// C2)
90 /// C2.1) The operand is in the form of "X | C", where C is a non-zero
91 /// constant.
92 /// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
93 /// operand as "E | 0"
95 public:
96  XorOpnd(Value *V);
97 
98  bool isInvalid() const { return SymbolicPart == nullptr; }
99  bool isOrExpr() const { return isOr; }
100  Value *getValue() const { return OrigVal; }
101  Value *getSymbolicPart() const { return SymbolicPart; }
102  unsigned getSymbolicRank() const { return SymbolicRank; }
103  const APInt &getConstPart() const { return ConstPart; }
104 
105  void Invalidate() { SymbolicPart = OrigVal = nullptr; }
106  void setSymbolicRank(unsigned R) { SymbolicRank = R; }
107 
108 private:
109  Value *OrigVal;
110  Value *SymbolicPart;
111  APInt ConstPart;
112  unsigned SymbolicRank;
113  bool isOr;
114 };
115 
117  assert(!isa<ConstantInt>(V) && "No ConstantInt");
118  OrigVal = V;
120  SymbolicRank = 0;
121 
122  if (I && (I->getOpcode() == Instruction::Or ||
123  I->getOpcode() == Instruction::And)) {
124  Value *V0 = I->getOperand(0);
125  Value *V1 = I->getOperand(1);
126  const APInt *C;
127  if (match(V0, PatternMatch::m_APInt(C)))
128  std::swap(V0, V1);
129 
130  if (match(V1, PatternMatch::m_APInt(C))) {
131  ConstPart = *C;
132  SymbolicPart = V0;
133  isOr = (I->getOpcode() == Instruction::Or);
134  return;
135  }
136  }
137 
138  // view the operand as "V | 0"
139  SymbolicPart = V;
140  ConstPart = APInt::getNullValue(V->getType()->getScalarSizeInBits());
141  isOr = true;
142 }
143 
144 /// Return true if V is an instruction of the specified opcode and if it
145 /// only has one use.
146 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
147  auto *I = dyn_cast<Instruction>(V);
148  if (I && I->hasOneUse() && I->getOpcode() == Opcode)
149  if (!isa<FPMathOperator>(I) || I->isFast())
150  return cast<BinaryOperator>(I);
151  return nullptr;
152 }
153 
154 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1,
155  unsigned Opcode2) {
156  auto *I = dyn_cast<Instruction>(V);
157  if (I && I->hasOneUse() &&
158  (I->getOpcode() == Opcode1 || I->getOpcode() == Opcode2))
159  if (!isa<FPMathOperator>(I) || I->isFast())
160  return cast<BinaryOperator>(I);
161  return nullptr;
162 }
163 
164 void ReassociatePass::BuildRankMap(Function &F,
166  unsigned Rank = 2;
167 
168  // Assign distinct ranks to function arguments.
169  for (auto &Arg : F.args()) {
170  ValueRankMap[&Arg] = ++Rank;
171  DEBUG(dbgs() << "Calculated Rank[" << Arg.getName() << "] = " << Rank
172  << "\n");
173  }
174 
175  // Traverse basic blocks in ReversePostOrder
176  for (BasicBlock *BB : RPOT) {
177  unsigned BBRank = RankMap[BB] = ++Rank << 16;
178 
179  // Walk the basic block, adding precomputed ranks for any instructions that
180  // we cannot move. This ensures that the ranks for these instructions are
181  // all different in the block.
182  for (Instruction &I : *BB)
183  if (mayBeMemoryDependent(I))
184  ValueRankMap[&I] = ++BBRank;
185  }
186 }
187 
188 unsigned ReassociatePass::getRank(Value *V) {
190  if (!I) {
191  if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
192  return 0; // Otherwise it's a global or constant, rank 0.
193  }
194 
195  if (unsigned Rank = ValueRankMap[I])
196  return Rank; // Rank already known?
197 
198  // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
199  // we can reassociate expressions for code motion! Since we do not recurse
200  // for PHI nodes, we cannot have infinite recursion here, because there
201  // cannot be loops in the value graph that do not go through PHI nodes.
202  unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
203  for (unsigned i = 0, e = I->getNumOperands();
204  i != e && Rank != MaxRank; ++i)
205  Rank = std::max(Rank, getRank(I->getOperand(i)));
206 
207  // If this is a not or neg instruction, do not count it for rank. This
208  // assures us that X and ~X will have the same rank.
211  ++Rank;
212 
213  DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " << Rank << "\n");
214 
215  return ValueRankMap[I] = Rank;
216 }
217 
218 // Canonicalize constants to RHS. Otherwise, sort the operands by rank.
219 void ReassociatePass::canonicalizeOperands(Instruction *I) {
220  assert(isa<BinaryOperator>(I) && "Expected binary operator.");
221  assert(I->isCommutative() && "Expected commutative operator.");
222 
223  Value *LHS = I->getOperand(0);
224  Value *RHS = I->getOperand(1);
225  if (LHS == RHS || isa<Constant>(RHS))
226  return;
227  if (isa<Constant>(LHS) || getRank(RHS) < getRank(LHS))
228  cast<BinaryOperator>(I)->swapOperands();
229 }
230 
231 static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name,
232  Instruction *InsertBefore, Value *FlagsOp) {
233  if (S1->getType()->isIntOrIntVectorTy())
234  return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore);
235  else {
236  BinaryOperator *Res =
237  BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore);
238  Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
239  return Res;
240  }
241 }
242 
243 static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name,
244  Instruction *InsertBefore, Value *FlagsOp) {
245  if (S1->getType()->isIntOrIntVectorTy())
246  return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore);
247  else {
248  BinaryOperator *Res =
249  BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore);
250  Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
251  return Res;
252  }
253 }
254 
256  Instruction *InsertBefore, Value *FlagsOp) {
257  if (S1->getType()->isIntOrIntVectorTy())
258  return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
259  else {
260  BinaryOperator *Res = BinaryOperator::CreateFNeg(S1, Name, InsertBefore);
261  Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
262  return Res;
263  }
264 }
265 
266 /// Replace 0-X with X*-1.
268  Type *Ty = Neg->getType();
269  Constant *NegOne = Ty->isIntOrIntVectorTy() ?
271 
272  BinaryOperator *Res = CreateMul(Neg->getOperand(1), NegOne, "", Neg, Neg);
273  Neg->setOperand(1, Constant::getNullValue(Ty)); // Drop use of op.
274  Res->takeName(Neg);
275  Neg->replaceAllUsesWith(Res);
276  Res->setDebugLoc(Neg->getDebugLoc());
277  return Res;
278 }
279 
280 /// Returns k such that lambda(2^Bitwidth) = 2^k, where lambda is the Carmichael
281 /// function. This means that x^(2^k) === 1 mod 2^Bitwidth for
282 /// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic.
283 /// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every
284 /// even x in Bitwidth-bit arithmetic.
285 static unsigned CarmichaelShift(unsigned Bitwidth) {
286  if (Bitwidth < 3)
287  return Bitwidth - 1;
288  return Bitwidth - 2;
289 }
290 
291 /// Add the extra weight 'RHS' to the existing weight 'LHS',
292 /// reducing the combined weight using any special properties of the operation.
293 /// The existing weight LHS represents the computation X op X op ... op X where
294 /// X occurs LHS times. The combined weight represents X op X op ... op X with
295 /// X occurring LHS + RHS times. If op is "Xor" for example then the combined
296 /// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even;
297 /// the routine returns 1 in LHS in the first case, and 0 in LHS in the second.
298 static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) {
299  // If we were working with infinite precision arithmetic then the combined
300  // weight would be LHS + RHS. But we are using finite precision arithmetic,
301  // and the APInt sum LHS + RHS may not be correct if it wraps (it is correct
302  // for nilpotent operations and addition, but not for idempotent operations
303  // and multiplication), so it is important to correctly reduce the combined
304  // weight back into range if wrapping would be wrong.
305 
306  // If RHS is zero then the weight didn't change.
307  if (RHS.isMinValue())
308  return;
309  // If LHS is zero then the combined weight is RHS.
310  if (LHS.isMinValue()) {
311  LHS = RHS;
312  return;
313  }
314  // From this point on we know that neither LHS nor RHS is zero.
315 
316  if (Instruction::isIdempotent(Opcode)) {
317  // Idempotent means X op X === X, so any non-zero weight is equivalent to a
318  // weight of 1. Keeping weights at zero or one also means that wrapping is
319  // not a problem.
320  assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
321  return; // Return a weight of 1.
322  }
323  if (Instruction::isNilpotent(Opcode)) {
324  // Nilpotent means X op X === 0, so reduce weights modulo 2.
325  assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
326  LHS = 0; // 1 + 1 === 0 modulo 2.
327  return;
328  }
329  if (Opcode == Instruction::Add || Opcode == Instruction::FAdd) {
330  // TODO: Reduce the weight by exploiting nsw/nuw?
331  LHS += RHS;
332  return;
333  }
334 
335  assert((Opcode == Instruction::Mul || Opcode == Instruction::FMul) &&
336  "Unknown associative operation!");
337  unsigned Bitwidth = LHS.getBitWidth();
338  // If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth
339  // can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth
340  // bit number x, since either x is odd in which case x^CM = 1, or x is even in
341  // which case both x^W and x^(W - CM) are zero. By subtracting off multiples
342  // of CM like this weights can always be reduced to the range [0, CM+Bitwidth)
343  // which by a happy accident means that they can always be represented using
344  // Bitwidth bits.
345  // TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than
346  // the Carmichael number).
347  if (Bitwidth > 3) {
348  /// CM - The value of Carmichael's lambda function.
349  APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth));
350  // Any weight W >= Threshold can be replaced with W - CM.
351  APInt Threshold = CM + Bitwidth;
352  assert(LHS.ult(Threshold) && RHS.ult(Threshold) && "Weights not reduced!");
353  // For Bitwidth 4 or more the following sum does not overflow.
354  LHS += RHS;
355  while (LHS.uge(Threshold))
356  LHS -= CM;
357  } else {
358  // To avoid problems with overflow do everything the same as above but using
359  // a larger type.
360  unsigned CM = 1U << CarmichaelShift(Bitwidth);
361  unsigned Threshold = CM + Bitwidth;
362  assert(LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold &&
363  "Weights not reduced!");
364  unsigned Total = LHS.getZExtValue() + RHS.getZExtValue();
365  while (Total >= Threshold)
366  Total -= CM;
367  LHS = Total;
368  }
369 }
370 
371 using RepeatedValue = std::pair<Value*, APInt>;
372 
373 /// Given an associative binary expression, return the leaf
374 /// nodes in Ops along with their weights (how many times the leaf occurs). The
375 /// original expression is the same as
376 /// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
377 /// op
378 /// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
379 /// op
380 /// ...
381 /// op
382 /// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
383 ///
384 /// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
385 ///
386 /// This routine may modify the function, in which case it returns 'true'. The
387 /// changes it makes may well be destructive, changing the value computed by 'I'
388 /// to something completely different. Thus if the routine returns 'true' then
389 /// you MUST either replace I with a new expression computed from the Ops array,
390 /// or use RewriteExprTree to put the values back in.
391 ///
392 /// A leaf node is either not a binary operation of the same kind as the root
393 /// node 'I' (i.e. is not a binary operator at all, or is, but with a different
394 /// opcode), or is the same kind of binary operator but has a use which either
395 /// does not belong to the expression, or does belong to the expression but is
396 /// a leaf node. Every leaf node has at least one use that is a non-leaf node
397 /// of the expression, while for non-leaf nodes (except for the root 'I') every
398 /// use is a non-leaf node of the expression.
399 ///
400 /// For example:
401 /// expression graph node names
402 ///
403 /// + | I
404 /// / \ |
405 /// + + | A, B
406 /// / \ / \ |
407 /// * + * | C, D, E
408 /// / \ / \ / \ |
409 /// + * | F, G
410 ///
411 /// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
412 /// that order) (C, 1), (E, 1), (F, 2), (G, 2).
413 ///
414 /// The expression is maximal: if some instruction is a binary operator of the
415 /// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
416 /// then the instruction also belongs to the expression, is not a leaf node of
417 /// it, and its operands also belong to the expression (but may be leaf nodes).
418 ///
419 /// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
420 /// order to ensure that every non-root node in the expression has *exactly one*
421 /// use by a non-leaf node of the expression. This destruction means that the
422 /// caller MUST either replace 'I' with a new expression or use something like
423 /// RewriteExprTree to put the values back in if the routine indicates that it
424 /// made a change by returning 'true'.
425 ///
426 /// In the above example either the right operand of A or the left operand of B
427 /// will be replaced by undef. If it is B's operand then this gives:
428 ///
429 /// + | I
430 /// / \ |
431 /// + + | A, B - operand of B replaced with undef
432 /// / \ \ |
433 /// * + * | C, D, E
434 /// / \ / \ / \ |
435 /// + * | F, G
436 ///
437 /// Note that such undef operands can only be reached by passing through 'I'.
438 /// For example, if you visit operands recursively starting from a leaf node
439 /// then you will never see such an undef operand unless you get back to 'I',
440 /// which requires passing through a phi node.
441 ///
442 /// Note that this routine may also mutate binary operators of the wrong type
443 /// that have all uses inside the expression (i.e. only used by non-leaf nodes
444 /// of the expression) if it can turn them into binary operators of the right
445 /// type and thus make the expression bigger.
448  DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
449  unsigned Bitwidth = I->getType()->getScalarType()->getPrimitiveSizeInBits();
450  unsigned Opcode = I->getOpcode();
451  assert(I->isAssociative() && I->isCommutative() &&
452  "Expected an associative and commutative operation!");
453 
454  // Visit all operands of the expression, keeping track of their weight (the
455  // number of paths from the expression root to the operand, or if you like
456  // the number of times that operand occurs in the linearized expression).
457  // For example, if I = X + A, where X = A + B, then I, X and B have weight 1
458  // while A has weight two.
459 
460  // Worklist of non-leaf nodes (their operands are in the expression too) along
461  // with their weights, representing a certain number of paths to the operator.
462  // If an operator occurs in the worklist multiple times then we found multiple
463  // ways to get to it.
464  SmallVector<std::pair<BinaryOperator*, APInt>, 8> Worklist; // (Op, Weight)
465  Worklist.push_back(std::make_pair(I, APInt(Bitwidth, 1)));
466  bool Changed = false;
467 
468  // Leaves of the expression are values that either aren't the right kind of
469  // operation (eg: a constant, or a multiply in an add tree), or are, but have
470  // some uses that are not inside the expression. For example, in I = X + X,
471  // X = A + B, the value X has two uses (by I) that are in the expression. If
472  // X has any other uses, for example in a return instruction, then we consider
473  // X to be a leaf, and won't analyze it further. When we first visit a value,
474  // if it has more than one use then at first we conservatively consider it to
475  // be a leaf. Later, as the expression is explored, we may discover some more
476  // uses of the value from inside the expression. If all uses turn out to be
477  // from within the expression (and the value is a binary operator of the right
478  // kind) then the value is no longer considered to be a leaf, and its operands
479  // are explored.
480 
481  // Leaves - Keeps track of the set of putative leaves as well as the number of
482  // paths to each leaf seen so far.
483  using LeafMap = DenseMap<Value *, APInt>;
484  LeafMap Leaves; // Leaf -> Total weight so far.
485  SmallVector<Value *, 8> LeafOrder; // Ensure deterministic leaf output order.
486 
487 #ifndef NDEBUG
488  SmallPtrSet<Value *, 8> Visited; // For sanity checking the iteration scheme.
489 #endif
490  while (!Worklist.empty()) {
491  std::pair<BinaryOperator*, APInt> P = Worklist.pop_back_val();
492  I = P.first; // We examine the operands of this binary operator.
493 
494  for (unsigned OpIdx = 0; OpIdx < 2; ++OpIdx) { // Visit operands.
495  Value *Op = I->getOperand(OpIdx);
496  APInt Weight = P.second; // Number of paths to this operand.
497  DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n");
498  assert(!Op->use_empty() && "No uses, so how did we get to it?!");
499 
500  // If this is a binary operation of the right kind with only one use then
501  // add its operands to the expression.
502  if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
503  assert(Visited.insert(Op).second && "Not first visit!");
504  DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n");
505  Worklist.push_back(std::make_pair(BO, Weight));
506  continue;
507  }
508 
509  // Appears to be a leaf. Is the operand already in the set of leaves?
510  LeafMap::iterator It = Leaves.find(Op);
511  if (It == Leaves.end()) {
512  // Not in the leaf map. Must be the first time we saw this operand.
513  assert(Visited.insert(Op).second && "Not first visit!");
514  if (!Op->hasOneUse()) {
515  // This value has uses not accounted for by the expression, so it is
516  // not safe to modify. Mark it as being a leaf.
517  DEBUG(dbgs() << "ADD USES LEAF: " << *Op << " (" << Weight << ")\n");
518  LeafOrder.push_back(Op);
519  Leaves[Op] = Weight;
520  continue;
521  }
522  // No uses outside the expression, try morphing it.
523  } else {
524  // Already in the leaf map.
525  assert(It != Leaves.end() && Visited.count(Op) &&
526  "In leaf map but not visited!");
527 
528  // Update the number of paths to the leaf.
529  IncorporateWeight(It->second, Weight, Opcode);
530 
531 #if 0 // TODO: Re-enable once PR13021 is fixed.
532  // The leaf already has one use from inside the expression. As we want
533  // exactly one such use, drop this new use of the leaf.
534  assert(!Op->hasOneUse() && "Only one use, but we got here twice!");
535  I->setOperand(OpIdx, UndefValue::get(I->getType()));
536  Changed = true;
537 
538  // If the leaf is a binary operation of the right kind and we now see
539  // that its multiple original uses were in fact all by nodes belonging
540  // to the expression, then no longer consider it to be a leaf and add
541  // its operands to the expression.
542  if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
543  DEBUG(dbgs() << "UNLEAF: " << *Op << " (" << It->second << ")\n");
544  Worklist.push_back(std::make_pair(BO, It->second));
545  Leaves.erase(It);
546  continue;
547  }
548 #endif
549 
550  // If we still have uses that are not accounted for by the expression
551  // then it is not safe to modify the value.
552  if (!Op->hasOneUse())
553  continue;
554 
555  // No uses outside the expression, try morphing it.
556  Weight = It->second;
557  Leaves.erase(It); // Since the value may be morphed below.
558  }
559 
560  // At this point we have a value which, first of all, is not a binary
561  // expression of the right kind, and secondly, is only used inside the
562  // expression. This means that it can safely be modified. See if we
563  // can usefully morph it into an expression of the right kind.
564  assert((!isa<Instruction>(Op) ||
565  cast<Instruction>(Op)->getOpcode() != Opcode
566  || (isa<FPMathOperator>(Op) &&
567  !cast<Instruction>(Op)->isFast())) &&
568  "Should have been handled above!");
569  assert(Op->hasOneUse() && "Has uses outside the expression tree!");
570 
571  // If this is a multiply expression, turn any internal negations into
572  // multiplies by -1 so they can be reassociated.
573  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op))
574  if ((Opcode == Instruction::Mul && BinaryOperator::isNeg(BO)) ||
575  (Opcode == Instruction::FMul && BinaryOperator::isFNeg(BO))) {
576  DEBUG(dbgs() << "MORPH LEAF: " << *Op << " (" << Weight << ") TO ");
577  BO = LowerNegateToMultiply(BO);
578  DEBUG(dbgs() << *BO << '\n');
579  Worklist.push_back(std::make_pair(BO, Weight));
580  Changed = true;
581  continue;
582  }
583 
584  // Failed to morph into an expression of the right type. This really is
585  // a leaf.
586  DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n");
587  assert(!isReassociableOp(Op, Opcode) && "Value was morphed?");
588  LeafOrder.push_back(Op);
589  Leaves[Op] = Weight;
590  }
591  }
592 
593  // The leaves, repeated according to their weights, represent the linearized
594  // form of the expression.
595  for (unsigned i = 0, e = LeafOrder.size(); i != e; ++i) {
596  Value *V = LeafOrder[i];
597  LeafMap::iterator It = Leaves.find(V);
598  if (It == Leaves.end())
599  // Node initially thought to be a leaf wasn't.
600  continue;
601  assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!");
602  APInt Weight = It->second;
603  if (Weight.isMinValue())
604  // Leaf already output or weight reduction eliminated it.
605  continue;
606  // Ensure the leaf is only output once.
607  It->second = 0;
608  Ops.push_back(std::make_pair(V, Weight));
609  }
610 
611  // For nilpotent operations or addition there may be no operands, for example
612  // because the expression was "X xor X" or consisted of 2^Bitwidth additions:
613  // in both cases the weight reduces to 0 causing the value to be skipped.
614  if (Ops.empty()) {
615  Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
616  assert(Identity && "Associative operation without identity!");
617  Ops.emplace_back(Identity, APInt(Bitwidth, 1));
618  }
619 
620  return Changed;
621 }
622 
623 /// Now that the operands for this expression tree are
624 /// linearized and optimized, emit them in-order.
625 void ReassociatePass::RewriteExprTree(BinaryOperator *I,
627  assert(Ops.size() > 1 && "Single values should be used directly!");
628 
629  // Since our optimizations should never increase the number of operations, the
630  // new expression can usually be written reusing the existing binary operators
631  // from the original expression tree, without creating any new instructions,
632  // though the rewritten expression may have a completely different topology.
633  // We take care to not change anything if the new expression will be the same
634  // as the original. If more than trivial changes (like commuting operands)
635  // were made then we are obliged to clear out any optional subclass data like
636  // nsw flags.
637 
638  /// NodesToRewrite - Nodes from the original expression available for writing
639  /// the new expression into.
640  SmallVector<BinaryOperator*, 8> NodesToRewrite;
641  unsigned Opcode = I->getOpcode();
642  BinaryOperator *Op = I;
643 
644  /// NotRewritable - The operands being written will be the leaves of the new
645  /// expression and must not be used as inner nodes (via NodesToRewrite) by
646  /// mistake. Inner nodes are always reassociable, and usually leaves are not
647  /// (if they were they would have been incorporated into the expression and so
648  /// would not be leaves), so most of the time there is no danger of this. But
649  /// in rare cases a leaf may become reassociable if an optimization kills uses
650  /// of it, or it may momentarily become reassociable during rewriting (below)
651  /// due it being removed as an operand of one of its uses. Ensure that misuse
652  /// of leaf nodes as inner nodes cannot occur by remembering all of the future
653  /// leaves and refusing to reuse any of them as inner nodes.
654  SmallPtrSet<Value*, 8> NotRewritable;
655  for (unsigned i = 0, e = Ops.size(); i != e; ++i)
656  NotRewritable.insert(Ops[i].Op);
657 
658  // ExpressionChanged - Non-null if the rewritten expression differs from the
659  // original in some non-trivial way, requiring the clearing of optional flags.
660  // Flags are cleared from the operator in ExpressionChanged up to I inclusive.
661  BinaryOperator *ExpressionChanged = nullptr;
662  for (unsigned i = 0; ; ++i) {
663  // The last operation (which comes earliest in the IR) is special as both
664  // operands will come from Ops, rather than just one with the other being
665  // a subexpression.
666  if (i+2 == Ops.size()) {
667  Value *NewLHS = Ops[i].Op;
668  Value *NewRHS = Ops[i+1].Op;
669  Value *OldLHS = Op->getOperand(0);
670  Value *OldRHS = Op->getOperand(1);
671 
672  if (NewLHS == OldLHS && NewRHS == OldRHS)
673  // Nothing changed, leave it alone.
674  break;
675 
676  if (NewLHS == OldRHS && NewRHS == OldLHS) {
677  // The order of the operands was reversed. Swap them.
678  DEBUG(dbgs() << "RA: " << *Op << '\n');
679  Op->swapOperands();
680  DEBUG(dbgs() << "TO: " << *Op << '\n');
681  MadeChange = true;
682  ++NumChanged;
683  break;
684  }
685 
686  // The new operation differs non-trivially from the original. Overwrite
687  // the old operands with the new ones.
688  DEBUG(dbgs() << "RA: " << *Op << '\n');
689  if (NewLHS != OldLHS) {
690  BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
691  if (BO && !NotRewritable.count(BO))
692  NodesToRewrite.push_back(BO);
693  Op->setOperand(0, NewLHS);
694  }
695  if (NewRHS != OldRHS) {
696  BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
697  if (BO && !NotRewritable.count(BO))
698  NodesToRewrite.push_back(BO);
699  Op->setOperand(1, NewRHS);
700  }
701  DEBUG(dbgs() << "TO: " << *Op << '\n');
702 
703  ExpressionChanged = Op;
704  MadeChange = true;
705  ++NumChanged;
706 
707  break;
708  }
709 
710  // Not the last operation. The left-hand side will be a sub-expression
711  // while the right-hand side will be the current element of Ops.
712  Value *NewRHS = Ops[i].Op;
713  if (NewRHS != Op->getOperand(1)) {
714  DEBUG(dbgs() << "RA: " << *Op << '\n');
715  if (NewRHS == Op->getOperand(0)) {
716  // The new right-hand side was already present as the left operand. If
717  // we are lucky then swapping the operands will sort out both of them.
718  Op->swapOperands();
719  } else {
720  // Overwrite with the new right-hand side.
721  BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
722  if (BO && !NotRewritable.count(BO))
723  NodesToRewrite.push_back(BO);
724  Op->setOperand(1, NewRHS);
725  ExpressionChanged = Op;
726  }
727  DEBUG(dbgs() << "TO: " << *Op << '\n');
728  MadeChange = true;
729  ++NumChanged;
730  }
731 
732  // Now deal with the left-hand side. If this is already an operation node
733  // from the original expression then just rewrite the rest of the expression
734  // into it.
735  BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode);
736  if (BO && !NotRewritable.count(BO)) {
737  Op = BO;
738  continue;
739  }
740 
741  // Otherwise, grab a spare node from the original expression and use that as
742  // the left-hand side. If there are no nodes left then the optimizers made
743  // an expression with more nodes than the original! This usually means that
744  // they did something stupid but it might mean that the problem was just too
745  // hard (finding the mimimal number of multiplications needed to realize a
746  // multiplication expression is NP-complete). Whatever the reason, smart or
747  // stupid, create a new node if there are none left.
748  BinaryOperator *NewOp;
749  if (NodesToRewrite.empty()) {
752  Undef, Undef, "", I);
753  if (NewOp->getType()->isFPOrFPVectorTy())
754  NewOp->setFastMathFlags(I->getFastMathFlags());
755  } else {
756  NewOp = NodesToRewrite.pop_back_val();
757  }
758 
759  DEBUG(dbgs() << "RA: " << *Op << '\n');
760  Op->setOperand(0, NewOp);
761  DEBUG(dbgs() << "TO: " << *Op << '\n');
762  ExpressionChanged = Op;
763  MadeChange = true;
764  ++NumChanged;
765  Op = NewOp;
766  }
767 
768  // If the expression changed non-trivially then clear out all subclass data
769  // starting from the operator specified in ExpressionChanged, and compactify
770  // the operators to just before the expression root to guarantee that the
771  // expression tree is dominated by all of Ops.
772  if (ExpressionChanged)
773  do {
774  // Preserve FastMathFlags.
775  if (isa<FPMathOperator>(I)) {
776  FastMathFlags Flags = I->getFastMathFlags();
777  ExpressionChanged->clearSubclassOptionalData();
778  ExpressionChanged->setFastMathFlags(Flags);
779  } else
780  ExpressionChanged->clearSubclassOptionalData();
781 
782  if (ExpressionChanged == I)
783  break;
784  ExpressionChanged->moveBefore(I);
785  ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->user_begin());
786  } while (true);
787 
788  // Throw away any left over nodes from the original expression.
789  for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)
790  RedoInsts.insert(NodesToRewrite[i]);
791 }
792 
793 /// Insert instructions before the instruction pointed to by BI,
794 /// that computes the negative version of the value specified. The negative
795 /// version of the value is returned, and BI is left pointing at the instruction
796 /// that should be processed next by the reassociation pass.
797 /// Also add intermediate instructions to the redo list that are modified while
798 /// pushing the negates through adds. These will be revisited to see if
799 /// additional opportunities have been exposed.
802  if (auto *C = dyn_cast<Constant>(V))
805 
806  // We are trying to expose opportunity for reassociation. One of the things
807  // that we want to do to achieve this is to push a negation as deep into an
808  // expression chain as possible, to expose the add instructions. In practice,
809  // this means that we turn this:
810  // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
811  // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
812  // the constants. We assume that instcombine will clean up the mess later if
813  // we introduce tons of unnecessary negation instructions.
814  //
815  if (BinaryOperator *I =
816  isReassociableOp(V, Instruction::Add, Instruction::FAdd)) {
817  // Push the negates through the add.
818  I->setOperand(0, NegateValue(I->getOperand(0), BI, ToRedo));
819  I->setOperand(1, NegateValue(I->getOperand(1), BI, ToRedo));
820  if (I->getOpcode() == Instruction::Add) {
821  I->setHasNoUnsignedWrap(false);
822  I->setHasNoSignedWrap(false);
823  }
824 
825  // We must move the add instruction here, because the neg instructions do
826  // not dominate the old add instruction in general. By moving it, we are
827  // assured that the neg instructions we just inserted dominate the
828  // instruction we are about to insert after them.
829  //
830  I->moveBefore(BI);
831  I->setName(I->getName()+".neg");
832 
833  // Add the intermediate negates to the redo list as processing them later
834  // could expose more reassociating opportunities.
835  ToRedo.insert(I);
836  return I;
837  }
838 
839  // Okay, we need to materialize a negated version of V with an instruction.
840  // Scan the use lists of V to see if we have one already.
841  for (User *U : V->users()) {
843  continue;
844 
845  // We found one! Now we have to make sure that the definition dominates
846  // this use. We do this by moving it to the entry block (if it is a
847  // non-instruction value) or right after the definition. These negates will
848  // be zapped by reassociate later, so we don't need much finesse here.
849  BinaryOperator *TheNeg = cast<BinaryOperator>(U);
850 
851  // Verify that the negate is in this function, V might be a constant expr.
852  if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
853  continue;
854 
855  BasicBlock::iterator InsertPt;
856  if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
857  if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
858  InsertPt = II->getNormalDest()->begin();
859  } else {
860  InsertPt = ++InstInput->getIterator();
861  }
862  while (isa<PHINode>(InsertPt)) ++InsertPt;
863  } else {
864  InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
865  }
866  TheNeg->moveBefore(&*InsertPt);
867  if (TheNeg->getOpcode() == Instruction::Sub) {
868  TheNeg->setHasNoUnsignedWrap(false);
869  TheNeg->setHasNoSignedWrap(false);
870  } else {
871  TheNeg->andIRFlags(BI);
872  }
873  ToRedo.insert(TheNeg);
874  return TheNeg;
875  }
876 
877  // Insert a 'neg' instruction that subtracts the value from zero to get the
878  // negation.
879  BinaryOperator *NewNeg = CreateNeg(V, V->getName() + ".neg", BI, BI);
880  ToRedo.insert(NewNeg);
881  return NewNeg;
882 }
883 
884 /// Return true if we should break up this subtract of X-Y into (X + -Y).
886  // If this is a negation, we can't split it up!
888  return false;
889 
890  // Don't breakup X - undef.
891  if (isa<UndefValue>(Sub->getOperand(1)))
892  return false;
893 
894  // Don't bother to break this up unless either the LHS is an associable add or
895  // subtract or if this is only used by one.
896  Value *V0 = Sub->getOperand(0);
897  if (isReassociableOp(V0, Instruction::Add, Instruction::FAdd) ||
898  isReassociableOp(V0, Instruction::Sub, Instruction::FSub))
899  return true;
900  Value *V1 = Sub->getOperand(1);
901  if (isReassociableOp(V1, Instruction::Add, Instruction::FAdd) ||
902  isReassociableOp(V1, Instruction::Sub, Instruction::FSub))
903  return true;
904  Value *VB = Sub->user_back();
905  if (Sub->hasOneUse() &&
906  (isReassociableOp(VB, Instruction::Add, Instruction::FAdd) ||
907  isReassociableOp(VB, Instruction::Sub, Instruction::FSub)))
908  return true;
909 
910  return false;
911 }
912 
913 /// If we have (X-Y), and if either X is an add, or if this is only used by an
914 /// add, transform this into (X+(0-Y)) to promote better reassociation.
915 static BinaryOperator *
917  // Convert a subtract into an add and a neg instruction. This allows sub
918  // instructions to be commuted with other add instructions.
919  //
920  // Calculate the negative value of Operand 1 of the sub instruction,
921  // and set it as the RHS of the add instruction we just made.
922  Value *NegVal = NegateValue(Sub->getOperand(1), Sub, ToRedo);
923  BinaryOperator *New = CreateAdd(Sub->getOperand(0), NegVal, "", Sub, Sub);
924  Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op.
925  Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op.
926  New->takeName(Sub);
927 
928  // Everyone now refers to the add instruction.
929  Sub->replaceAllUsesWith(New);
930  New->setDebugLoc(Sub->getDebugLoc());
931 
932  DEBUG(dbgs() << "Negated: " << *New << '\n');
933  return New;
934 }
935 
936 /// If this is a shift of a reassociable multiply or is used by one, change
937 /// this into a multiply by a constant to assist with further reassociation.
939  Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
940  MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
941 
942  BinaryOperator *Mul =
943  BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
944  Shl->setOperand(0, UndefValue::get(Shl->getType())); // Drop use of op.
945  Mul->takeName(Shl);
946 
947  // Everyone now refers to the mul instruction.
948  Shl->replaceAllUsesWith(Mul);
949  Mul->setDebugLoc(Shl->getDebugLoc());
950 
951  // We can safely preserve the nuw flag in all cases. It's also safe to turn a
952  // nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special
953  // handling.
954  bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap();
955  bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap();
956  if (NSW && NUW)
957  Mul->setHasNoSignedWrap(true);
958  Mul->setHasNoUnsignedWrap(NUW);
959  return Mul;
960 }
961 
962 /// Scan backwards and forwards among values with the same rank as element i
963 /// to see if X exists. If X does not exist, return i. This is useful when
964 /// scanning for 'x' when we see '-x' because they both get the same rank.
966  unsigned i, Value *X) {
967  unsigned XRank = Ops[i].Rank;
968  unsigned e = Ops.size();
969  for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
970  if (Ops[j].Op == X)
971  return j;
972  if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
973  if (Instruction *I2 = dyn_cast<Instruction>(X))
974  if (I1->isIdenticalTo(I2))
975  return j;
976  }
977  // Scan backwards.
978  for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
979  if (Ops[j].Op == X)
980  return j;
981  if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
982  if (Instruction *I2 = dyn_cast<Instruction>(X))
983  if (I1->isIdenticalTo(I2))
984  return j;
985  }
986  return i;
987 }
988 
989 /// Emit a tree of add instructions, summing Ops together
990 /// and returning the result. Insert the tree before I.
993  if (Ops.size() == 1) return Ops.back();
994 
995  Value *V1 = Ops.back();
996  Ops.pop_back();
997  Value *V2 = EmitAddTreeOfValues(I, Ops);
998  return CreateAdd(V2, V1, "reass.add", I, I);
999 }
1000 
1001 /// If V is an expression tree that is a multiplication sequence,
1002 /// and if this sequence contains a multiply by Factor,
1003 /// remove Factor from the tree and return the new tree.
1004 Value *ReassociatePass::RemoveFactorFromExpression(Value *V, Value *Factor) {
1005  BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
1006  if (!BO)
1007  return nullptr;
1008 
1010  MadeChange |= LinearizeExprTree(BO, Tree);
1012  Factors.reserve(Tree.size());
1013  for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
1014  RepeatedValue E = Tree[i];
1015  Factors.append(E.second.getZExtValue(),
1016  ValueEntry(getRank(E.first), E.first));
1017  }
1018 
1019  bool FoundFactor = false;
1020  bool NeedsNegate = false;
1021  for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1022  if (Factors[i].Op == Factor) {
1023  FoundFactor = true;
1024  Factors.erase(Factors.begin()+i);
1025  break;
1026  }
1027 
1028  // If this is a negative version of this factor, remove it.
1029  if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor)) {
1030  if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
1031  if (FC1->getValue() == -FC2->getValue()) {
1032  FoundFactor = NeedsNegate = true;
1033  Factors.erase(Factors.begin()+i);
1034  break;
1035  }
1036  } else if (ConstantFP *FC1 = dyn_cast<ConstantFP>(Factor)) {
1037  if (ConstantFP *FC2 = dyn_cast<ConstantFP>(Factors[i].Op)) {
1038  const APFloat &F1 = FC1->getValueAPF();
1039  APFloat F2(FC2->getValueAPF());
1040  F2.changeSign();
1041  if (F1.compare(F2) == APFloat::cmpEqual) {
1042  FoundFactor = NeedsNegate = true;
1043  Factors.erase(Factors.begin() + i);
1044  break;
1045  }
1046  }
1047  }
1048  }
1049 
1050  if (!FoundFactor) {
1051  // Make sure to restore the operands to the expression tree.
1052  RewriteExprTree(BO, Factors);
1053  return nullptr;
1054  }
1055 
1056  BasicBlock::iterator InsertPt = ++BO->getIterator();
1057 
1058  // If this was just a single multiply, remove the multiply and return the only
1059  // remaining operand.
1060  if (Factors.size() == 1) {
1061  RedoInsts.insert(BO);
1062  V = Factors[0].Op;
1063  } else {
1064  RewriteExprTree(BO, Factors);
1065  V = BO;
1066  }
1067 
1068  if (NeedsNegate)
1069  V = CreateNeg(V, "neg", &*InsertPt, BO);
1070 
1071  return V;
1072 }
1073 
1074 /// If V is a single-use multiply, recursively add its operands as factors,
1075 /// otherwise add V to the list of factors.
1076 ///
1077 /// Ops is the top-level list of add operands we're trying to factor.
1079  SmallVectorImpl<Value*> &Factors) {
1080  BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
1081  if (!BO) {
1082  Factors.push_back(V);
1083  return;
1084  }
1085 
1086  // Otherwise, add the LHS and RHS to the list of factors.
1087  FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
1088  FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
1089 }
1090 
1091 /// Optimize a series of operands to an 'and', 'or', or 'xor' instruction.
1092 /// This optimizes based on identities. If it can be reduced to a single Value,
1093 /// it is returned, otherwise the Ops list is mutated as necessary.
1094 static Value *OptimizeAndOrXor(unsigned Opcode,
1096  // Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
1097  // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
1098  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1099  // First, check for X and ~X in the operand list.
1100  assert(i < Ops.size());
1101  if (BinaryOperator::isNot(Ops[i].Op)) { // Cannot occur for ^.
1102  Value *X = BinaryOperator::getNotArgument(Ops[i].Op);
1103  unsigned FoundX = FindInOperandList(Ops, i, X);
1104  if (FoundX != i) {
1105  if (Opcode == Instruction::And) // ...&X&~X = 0
1106  return Constant::getNullValue(X->getType());
1107 
1108  if (Opcode == Instruction::Or) // ...|X|~X = -1
1109  return Constant::getAllOnesValue(X->getType());
1110  }
1111  }
1112 
1113  // Next, check for duplicate pairs of values, which we assume are next to
1114  // each other, due to our sorting criteria.
1115  assert(i < Ops.size());
1116  if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
1117  if (Opcode == Instruction::And || Opcode == Instruction::Or) {
1118  // Drop duplicate values for And and Or.
1119  Ops.erase(Ops.begin()+i);
1120  --i; --e;
1121  ++NumAnnihil;
1122  continue;
1123  }
1124 
1125  // Drop pairs of values for Xor.
1126  assert(Opcode == Instruction::Xor);
1127  if (e == 2)
1128  return Constant::getNullValue(Ops[0].Op->getType());
1129 
1130  // Y ^ X^X -> Y
1131  Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
1132  i -= 1; e -= 2;
1133  ++NumAnnihil;
1134  }
1135  }
1136  return nullptr;
1137 }
1138 
1139 /// Helper function of CombineXorOpnd(). It creates a bitwise-and
1140 /// instruction with the given two operands, and return the resulting
1141 /// instruction. There are two special cases: 1) if the constant operand is 0,
1142 /// it will return NULL. 2) if the constant is ~0, the symbolic operand will
1143 /// be returned.
1144 static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd,
1145  const APInt &ConstOpnd) {
1146  if (ConstOpnd.isNullValue())
1147  return nullptr;
1148 
1149  if (ConstOpnd.isAllOnesValue())
1150  return Opnd;
1151 
1152  Instruction *I = BinaryOperator::CreateAnd(
1153  Opnd, ConstantInt::get(Opnd->getType(), ConstOpnd), "and.ra",
1154  InsertBefore);
1155  I->setDebugLoc(InsertBefore->getDebugLoc());
1156  return I;
1157 }
1158 
1159 // Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
1160 // into "R ^ C", where C would be 0, and R is a symbolic value.
1161 //
1162 // If it was successful, true is returned, and the "R" and "C" is returned
1163 // via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
1164 // and both "Res" and "ConstOpnd" remain unchanged.
1165 bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
1166  APInt &ConstOpnd, Value *&Res) {
1167  // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
1168  // = ((x | c1) ^ c1) ^ (c1 ^ c2)
1169  // = (x & ~c1) ^ (c1 ^ c2)
1170  // It is useful only when c1 == c2.
1171  if (!Opnd1->isOrExpr() || Opnd1->getConstPart().isNullValue())
1172  return false;
1173 
1174  if (!Opnd1->getValue()->hasOneUse())
1175  return false;
1176 
1177  const APInt &C1 = Opnd1->getConstPart();
1178  if (C1 != ConstOpnd)
1179  return false;
1180 
1181  Value *X = Opnd1->getSymbolicPart();
1182  Res = createAndInstr(I, X, ~C1);
1183  // ConstOpnd was C2, now C1 ^ C2.
1184  ConstOpnd ^= C1;
1185 
1186  if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1187  RedoInsts.insert(T);
1188  return true;
1189 }
1190 
1191 // Helper function of OptimizeXor(). It tries to simplify
1192 // "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
1193 // symbolic value.
1194 //
1195 // If it was successful, true is returned, and the "R" and "C" is returned
1196 // via "Res" and "ConstOpnd", respectively (If the entire expression is
1197 // evaluated to a constant, the Res is set to NULL); otherwise, false is
1198 // returned, and both "Res" and "ConstOpnd" remain unchanged.
1199 bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
1200  XorOpnd *Opnd2, APInt &ConstOpnd,
1201  Value *&Res) {
1202  Value *X = Opnd1->getSymbolicPart();
1203  if (X != Opnd2->getSymbolicPart())
1204  return false;
1205 
1206  // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
1207  int DeadInstNum = 1;
1208  if (Opnd1->getValue()->hasOneUse())
1209  DeadInstNum++;
1210  if (Opnd2->getValue()->hasOneUse())
1211  DeadInstNum++;
1212 
1213  // Xor-Rule 2:
1214  // (x | c1) ^ (x & c2)
1215  // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
1216  // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
1217  // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
1218  //
1219  if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
1220  if (Opnd2->isOrExpr())
1221  std::swap(Opnd1, Opnd2);
1222 
1223  const APInt &C1 = Opnd1->getConstPart();
1224  const APInt &C2 = Opnd2->getConstPart();
1225  APInt C3((~C1) ^ C2);
1226 
1227  // Do not increase code size!
1228  if (!C3.isNullValue() && !C3.isAllOnesValue()) {
1229  int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
1230  if (NewInstNum > DeadInstNum)
1231  return false;
1232  }
1233 
1234  Res = createAndInstr(I, X, C3);
1235  ConstOpnd ^= C1;
1236  } else if (Opnd1->isOrExpr()) {
1237  // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
1238  //
1239  const APInt &C1 = Opnd1->getConstPart();
1240  const APInt &C2 = Opnd2->getConstPart();
1241  APInt C3 = C1 ^ C2;
1242 
1243  // Do not increase code size
1244  if (!C3.isNullValue() && !C3.isAllOnesValue()) {
1245  int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
1246  if (NewInstNum > DeadInstNum)
1247  return false;
1248  }
1249 
1250  Res = createAndInstr(I, X, C3);
1251  ConstOpnd ^= C3;
1252  } else {
1253  // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
1254  //
1255  const APInt &C1 = Opnd1->getConstPart();
1256  const APInt &C2 = Opnd2->getConstPart();
1257  APInt C3 = C1 ^ C2;
1258  Res = createAndInstr(I, X, C3);
1259  }
1260 
1261  // Put the original operands in the Redo list; hope they will be deleted
1262  // as dead code.
1263  if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1264  RedoInsts.insert(T);
1265  if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
1266  RedoInsts.insert(T);
1267 
1268  return true;
1269 }
1270 
1271 /// Optimize a series of operands to an 'xor' instruction. If it can be reduced
1272 /// to a single Value, it is returned, otherwise the Ops list is mutated as
1273 /// necessary.
1274 Value *ReassociatePass::OptimizeXor(Instruction *I,
1276  if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
1277  return V;
1278 
1279  if (Ops.size() == 1)
1280  return nullptr;
1281 
1283  SmallVector<XorOpnd*, 8> OpndPtrs;
1284  Type *Ty = Ops[0].Op->getType();
1285  APInt ConstOpnd(Ty->getScalarSizeInBits(), 0);
1286 
1287  // Step 1: Convert ValueEntry to XorOpnd
1288  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1289  Value *V = Ops[i].Op;
1290  const APInt *C;
1291  // TODO: Support non-splat vectors.
1292  if (match(V, PatternMatch::m_APInt(C))) {
1293  ConstOpnd ^= *C;
1294  } else {
1295  XorOpnd O(V);
1296  O.setSymbolicRank(getRank(O.getSymbolicPart()));
1297  Opnds.push_back(O);
1298  }
1299  }
1300 
1301  // NOTE: From this point on, do *NOT* add/delete element to/from "Opnds".
1302  // It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate
1303  // the "OpndPtrs" as well. For the similar reason, do not fuse this loop
1304  // with the previous loop --- the iterator of the "Opnds" may be invalidated
1305  // when new elements are added to the vector.
1306  for (unsigned i = 0, e = Opnds.size(); i != e; ++i)
1307  OpndPtrs.push_back(&Opnds[i]);
1308 
1309  // Step 2: Sort the Xor-Operands in a way such that the operands containing
1310  // the same symbolic value cluster together. For instance, the input operand
1311  // sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
1312  // ("x | 123", "x & 789", "y & 456").
1313  //
1314  // The purpose is twofold:
1315  // 1) Cluster together the operands sharing the same symbolic-value.
1316  // 2) Operand having smaller symbolic-value-rank is permuted earlier, which
1317  // could potentially shorten crital path, and expose more loop-invariants.
1318  // Note that values' rank are basically defined in RPO order (FIXME).
1319  // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
1320  // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
1321  // "z" in the order of X-Y-Z is better than any other orders.
1322  std::stable_sort(OpndPtrs.begin(), OpndPtrs.end(),
1323  [](XorOpnd *LHS, XorOpnd *RHS) {
1324  return LHS->getSymbolicRank() < RHS->getSymbolicRank();
1325  });
1326 
1327  // Step 3: Combine adjacent operands
1328  XorOpnd *PrevOpnd = nullptr;
1329  bool Changed = false;
1330  for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
1331  XorOpnd *CurrOpnd = OpndPtrs[i];
1332  // The combined value
1333  Value *CV;
1334 
1335  // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
1336  if (!ConstOpnd.isNullValue() &&
1337  CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
1338  Changed = true;
1339  if (CV)
1340  *CurrOpnd = XorOpnd(CV);
1341  else {
1342  CurrOpnd->Invalidate();
1343  continue;
1344  }
1345  }
1346 
1347  if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
1348  PrevOpnd = CurrOpnd;
1349  continue;
1350  }
1351 
1352  // step 3.2: When previous and current operands share the same symbolic
1353  // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
1354  if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
1355  // Remove previous operand
1356  PrevOpnd->Invalidate();
1357  if (CV) {
1358  *CurrOpnd = XorOpnd(CV);
1359  PrevOpnd = CurrOpnd;
1360  } else {
1361  CurrOpnd->Invalidate();
1362  PrevOpnd = nullptr;
1363  }
1364  Changed = true;
1365  }
1366  }
1367 
1368  // Step 4: Reassemble the Ops
1369  if (Changed) {
1370  Ops.clear();
1371  for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
1372  XorOpnd &O = Opnds[i];
1373  if (O.isInvalid())
1374  continue;
1375  ValueEntry VE(getRank(O.getValue()), O.getValue());
1376  Ops.push_back(VE);
1377  }
1378  if (!ConstOpnd.isNullValue()) {
1379  Value *C = ConstantInt::get(Ty, ConstOpnd);
1380  ValueEntry VE(getRank(C), C);
1381  Ops.push_back(VE);
1382  }
1383  unsigned Sz = Ops.size();
1384  if (Sz == 1)
1385  return Ops.back().Op;
1386  if (Sz == 0) {
1387  assert(ConstOpnd.isNullValue());
1388  return ConstantInt::get(Ty, ConstOpnd);
1389  }
1390  }
1391 
1392  return nullptr;
1393 }
1394 
1395 /// Optimize a series of operands to an 'add' instruction. This
1396 /// optimizes based on identities. If it can be reduced to a single Value, it
1397 /// is returned, otherwise the Ops list is mutated as necessary.
1398 Value *ReassociatePass::OptimizeAdd(Instruction *I,
1400  // Scan the operand lists looking for X and -X pairs. If we find any, we
1401  // can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it,
1402  // scan for any
1403  // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
1404 
1405  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1406  Value *TheOp = Ops[i].Op;
1407  // Check to see if we've seen this operand before. If so, we factor all
1408  // instances of the operand together. Due to our sorting criteria, we know
1409  // that these need to be next to each other in the vector.
1410  if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
1411  // Rescan the list, remove all instances of this operand from the expr.
1412  unsigned NumFound = 0;
1413  do {
1414  Ops.erase(Ops.begin()+i);
1415  ++NumFound;
1416  } while (i != Ops.size() && Ops[i].Op == TheOp);
1417 
1418  DEBUG(dbgs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n');
1419  ++NumFactor;
1420 
1421  // Insert a new multiply.
1422  Type *Ty = TheOp->getType();
1423  Constant *C = Ty->isIntOrIntVectorTy() ?
1424  ConstantInt::get(Ty, NumFound) : ConstantFP::get(Ty, NumFound);
1425  Instruction *Mul = CreateMul(TheOp, C, "factor", I, I);
1426 
1427  // Now that we have inserted a multiply, optimize it. This allows us to
1428  // handle cases that require multiple factoring steps, such as this:
1429  // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
1430  RedoInsts.insert(Mul);
1431 
1432  // If every add operand was a duplicate, return the multiply.
1433  if (Ops.empty())
1434  return Mul;
1435 
1436  // Otherwise, we had some input that didn't have the dupe, such as
1437  // "A + A + B" -> "A*2 + B". Add the new multiply to the list of
1438  // things being added by this operation.
1439  Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
1440 
1441  --i;
1442  e = Ops.size();
1443  continue;
1444  }
1445 
1446  // Check for X and -X or X and ~X in the operand list.
1447  if (!BinaryOperator::isNeg(TheOp) && !BinaryOperator::isFNeg(TheOp) &&
1448  !BinaryOperator::isNot(TheOp))
1449  continue;
1450 
1451  Value *X = nullptr;
1452  if (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp))
1453  X = BinaryOperator::getNegArgument(TheOp);
1454  else if (BinaryOperator::isNot(TheOp))
1455  X = BinaryOperator::getNotArgument(TheOp);
1456 
1457  unsigned FoundX = FindInOperandList(Ops, i, X);
1458  if (FoundX == i)
1459  continue;
1460 
1461  // Remove X and -X from the operand list.
1462  if (Ops.size() == 2 &&
1463  (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp)))
1464  return Constant::getNullValue(X->getType());
1465 
1466  // Remove X and ~X from the operand list.
1467  if (Ops.size() == 2 && BinaryOperator::isNot(TheOp))
1468  return Constant::getAllOnesValue(X->getType());
1469 
1470  Ops.erase(Ops.begin()+i);
1471  if (i < FoundX)
1472  --FoundX;
1473  else
1474  --i; // Need to back up an extra one.
1475  Ops.erase(Ops.begin()+FoundX);
1476  ++NumAnnihil;
1477  --i; // Revisit element.
1478  e -= 2; // Removed two elements.
1479 
1480  // if X and ~X we append -1 to the operand list.
1481  if (BinaryOperator::isNot(TheOp)) {
1483  Ops.insert(Ops.end(), ValueEntry(getRank(V), V));
1484  e += 1;
1485  }
1486  }
1487 
1488  // Scan the operand list, checking to see if there are any common factors
1489  // between operands. Consider something like A*A+A*B*C+D. We would like to
1490  // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
1491  // To efficiently find this, we count the number of times a factor occurs
1492  // for any ADD operands that are MULs.
1493  DenseMap<Value*, unsigned> FactorOccurrences;
1494 
1495  // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
1496  // where they are actually the same multiply.
1497  unsigned MaxOcc = 0;
1498  Value *MaxOccVal = nullptr;
1499  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1500  BinaryOperator *BOp =
1501  isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1502  if (!BOp)
1503  continue;
1504 
1505  // Compute all of the factors of this added value.
1506  SmallVector<Value*, 8> Factors;
1507  FindSingleUseMultiplyFactors(BOp, Factors);
1508  assert(Factors.size() > 1 && "Bad linearize!");
1509 
1510  // Add one to FactorOccurrences for each unique factor in this op.
1511  SmallPtrSet<Value*, 8> Duplicates;
1512  for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1513  Value *Factor = Factors[i];
1514  if (!Duplicates.insert(Factor).second)
1515  continue;
1516 
1517  unsigned Occ = ++FactorOccurrences[Factor];
1518  if (Occ > MaxOcc) {
1519  MaxOcc = Occ;
1520  MaxOccVal = Factor;
1521  }
1522 
1523  // If Factor is a negative constant, add the negated value as a factor
1524  // because we can percolate the negate out. Watch for minint, which
1525  // cannot be positivified.
1526  if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor)) {
1527  if (CI->isNegative() && !CI->isMinValue(true)) {
1528  Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
1529  if (!Duplicates.insert(Factor).second)
1530  continue;
1531  unsigned Occ = ++FactorOccurrences[Factor];
1532  if (Occ > MaxOcc) {
1533  MaxOcc = Occ;
1534  MaxOccVal = Factor;
1535  }
1536  }
1537  } else if (ConstantFP *CF = dyn_cast<ConstantFP>(Factor)) {
1538  if (CF->isNegative()) {
1539  APFloat F(CF->getValueAPF());
1540  F.changeSign();
1541  Factor = ConstantFP::get(CF->getContext(), F);
1542  if (!Duplicates.insert(Factor).second)
1543  continue;
1544  unsigned Occ = ++FactorOccurrences[Factor];
1545  if (Occ > MaxOcc) {
1546  MaxOcc = Occ;
1547  MaxOccVal = Factor;
1548  }
1549  }
1550  }
1551  }
1552  }
1553 
1554  // If any factor occurred more than one time, we can pull it out.
1555  if (MaxOcc > 1) {
1556  DEBUG(dbgs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
1557  ++NumFactor;
1558 
1559  // Create a new instruction that uses the MaxOccVal twice. If we don't do
1560  // this, we could otherwise run into situations where removing a factor
1561  // from an expression will drop a use of maxocc, and this can cause
1562  // RemoveFactorFromExpression on successive values to behave differently.
1563  Instruction *DummyInst =
1564  I->getType()->isIntOrIntVectorTy()
1565  ? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal)
1566  : BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal);
1567 
1569  for (unsigned i = 0; i != Ops.size(); ++i) {
1570  // Only try to remove factors from expressions we're allowed to.
1571  BinaryOperator *BOp =
1572  isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1573  if (!BOp)
1574  continue;
1575 
1576  if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
1577  // The factorized operand may occur several times. Convert them all in
1578  // one fell swoop.
1579  for (unsigned j = Ops.size(); j != i;) {
1580  --j;
1581  if (Ops[j].Op == Ops[i].Op) {
1582  NewMulOps.push_back(V);
1583  Ops.erase(Ops.begin()+j);
1584  }
1585  }
1586  --i;
1587  }
1588  }
1589 
1590  // No need for extra uses anymore.
1591  DummyInst->deleteValue();
1592 
1593  unsigned NumAddedValues = NewMulOps.size();
1594  Value *V = EmitAddTreeOfValues(I, NewMulOps);
1595 
1596  // Now that we have inserted the add tree, optimize it. This allows us to
1597  // handle cases that require multiple factoring steps, such as this:
1598  // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
1599  assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
1600  (void)NumAddedValues;
1601  if (Instruction *VI = dyn_cast<Instruction>(V))
1602  RedoInsts.insert(VI);
1603 
1604  // Create the multiply.
1605  Instruction *V2 = CreateMul(V, MaxOccVal, "reass.mul", I, I);
1606 
1607  // Rerun associate on the multiply in case the inner expression turned into
1608  // a multiply. We want to make sure that we keep things in canonical form.
1609  RedoInsts.insert(V2);
1610 
1611  // If every add operand included the factor (e.g. "A*B + A*C"), then the
1612  // entire result expression is just the multiply "A*(B+C)".
1613  if (Ops.empty())
1614  return V2;
1615 
1616  // Otherwise, we had some input that didn't have the factor, such as
1617  // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
1618  // things being added by this operation.
1619  Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
1620  }
1621 
1622  return nullptr;
1623 }
1624 
1625 /// \brief Build up a vector of value/power pairs factoring a product.
1626 ///
1627 /// Given a series of multiplication operands, build a vector of factors and
1628 /// the powers each is raised to when forming the final product. Sort them in
1629 /// the order of descending power.
1630 ///
1631 /// (x*x) -> [(x, 2)]
1632 /// ((x*x)*x) -> [(x, 3)]
1633 /// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
1634 ///
1635 /// \returns Whether any factors have a power greater than one.
1637  SmallVectorImpl<Factor> &Factors) {
1638  // FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this.
1639  // Compute the sum of powers of simplifiable factors.
1640  unsigned FactorPowerSum = 0;
1641  for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) {
1642  Value *Op = Ops[Idx-1].Op;
1643 
1644  // Count the number of occurrences of this value.
1645  unsigned Count = 1;
1646  for (; Idx < Size && Ops[Idx].Op == Op; ++Idx)
1647  ++Count;
1648  // Track for simplification all factors which occur 2 or more times.
1649  if (Count > 1)
1650  FactorPowerSum += Count;
1651  }
1652 
1653  // We can only simplify factors if the sum of the powers of our simplifiable
1654  // factors is 4 or higher. When that is the case, we will *always* have
1655  // a simplification. This is an important invariant to prevent cyclicly
1656  // trying to simplify already minimal formations.
1657  if (FactorPowerSum < 4)
1658  return false;
1659 
1660  // Now gather the simplifiable factors, removing them from Ops.
1661  FactorPowerSum = 0;
1662  for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) {
1663  Value *Op = Ops[Idx-1].Op;
1664 
1665  // Count the number of occurrences of this value.
1666  unsigned Count = 1;
1667  for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx)
1668  ++Count;
1669  if (Count == 1)
1670  continue;
1671  // Move an even number of occurrences to Factors.
1672  Count &= ~1U;
1673  Idx -= Count;
1674  FactorPowerSum += Count;
1675  Factors.push_back(Factor(Op, Count));
1676  Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count);
1677  }
1678 
1679  // None of the adjustments above should have reduced the sum of factor powers
1680  // below our mininum of '4'.
1681  assert(FactorPowerSum >= 4);
1682 
1683  std::stable_sort(Factors.begin(), Factors.end(),
1684  [](const Factor &LHS, const Factor &RHS) {
1685  return LHS.Power > RHS.Power;
1686  });
1687  return true;
1688 }
1689 
1690 /// \brief Build a tree of multiplies, computing the product of Ops.
1692  SmallVectorImpl<Value*> &Ops) {
1693  if (Ops.size() == 1)
1694  return Ops.back();
1695 
1696  Value *LHS = Ops.pop_back_val();
1697  do {
1698  if (LHS->getType()->isIntOrIntVectorTy())
1699  LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
1700  else
1701  LHS = Builder.CreateFMul(LHS, Ops.pop_back_val());
1702  } while (!Ops.empty());
1703 
1704  return LHS;
1705 }
1706 
1707 /// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
1708 ///
1709 /// Given a vector of values raised to various powers, where no two values are
1710 /// equal and the powers are sorted in decreasing order, compute the minimal
1711 /// DAG of multiplies to compute the final product, and return that product
1712 /// value.
1713 Value *
1714 ReassociatePass::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
1715  SmallVectorImpl<Factor> &Factors) {
1716  assert(Factors[0].Power);
1717  SmallVector<Value *, 4> OuterProduct;
1718  for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
1719  Idx < Size && Factors[Idx].Power > 0; ++Idx) {
1720  if (Factors[Idx].Power != Factors[LastIdx].Power) {
1721  LastIdx = Idx;
1722  continue;
1723  }
1724 
1725  // We want to multiply across all the factors with the same power so that
1726  // we can raise them to that power as a single entity. Build a mini tree
1727  // for that.
1728  SmallVector<Value *, 4> InnerProduct;
1729  InnerProduct.push_back(Factors[LastIdx].Base);
1730  do {
1731  InnerProduct.push_back(Factors[Idx].Base);
1732  ++Idx;
1733  } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
1734 
1735  // Reset the base value of the first factor to the new expression tree.
1736  // We'll remove all the factors with the same power in a second pass.
1737  Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
1738  if (Instruction *MI = dyn_cast<Instruction>(M))
1739  RedoInsts.insert(MI);
1740 
1741  LastIdx = Idx;
1742  }
1743  // Unique factors with equal powers -- we've folded them into the first one's
1744  // base.
1745  Factors.erase(std::unique(Factors.begin(), Factors.end(),
1746  [](const Factor &LHS, const Factor &RHS) {
1747  return LHS.Power == RHS.Power;
1748  }),
1749  Factors.end());
1750 
1751  // Iteratively collect the base of each factor with an add power into the
1752  // outer product, and halve each power in preparation for squaring the
1753  // expression.
1754  for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
1755  if (Factors[Idx].Power & 1)
1756  OuterProduct.push_back(Factors[Idx].Base);
1757  Factors[Idx].Power >>= 1;
1758  }
1759  if (Factors[0].Power) {
1760  Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
1761  OuterProduct.push_back(SquareRoot);
1762  OuterProduct.push_back(SquareRoot);
1763  }
1764  if (OuterProduct.size() == 1)
1765  return OuterProduct.front();
1766 
1767  Value *V = buildMultiplyTree(Builder, OuterProduct);
1768  return V;
1769 }
1770 
1771 Value *ReassociatePass::OptimizeMul(BinaryOperator *I,
1773  // We can only optimize the multiplies when there is a chain of more than
1774  // three, such that a balanced tree might require fewer total multiplies.
1775  if (Ops.size() < 4)
1776  return nullptr;
1777 
1778  // Try to turn linear trees of multiplies without other uses of the
1779  // intermediate stages into minimal multiply DAGs with perfect sub-expression
1780  // re-use.
1781  SmallVector<Factor, 4> Factors;
1782  if (!collectMultiplyFactors(Ops, Factors))
1783  return nullptr; // All distinct factors, so nothing left for us to do.
1784 
1785  IRBuilder<> Builder(I);
1786  // The reassociate transformation for FP operations is performed only
1787  // if unsafe algebra is permitted by FastMathFlags. Propagate those flags
1788  // to the newly generated operations.
1789  if (auto FPI = dyn_cast<FPMathOperator>(I))
1790  Builder.setFastMathFlags(FPI->getFastMathFlags());
1791 
1792  Value *V = buildMinimalMultiplyDAG(Builder, Factors);
1793  if (Ops.empty())
1794  return V;
1795 
1796  ValueEntry NewEntry = ValueEntry(getRank(V), V);
1797  Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry);
1798  return nullptr;
1799 }
1800 
1801 Value *ReassociatePass::OptimizeExpression(BinaryOperator *I,
1803  // Now that we have the linearized expression tree, try to optimize it.
1804  // Start by folding any constants that we found.
1805  Constant *Cst = nullptr;
1806  unsigned Opcode = I->getOpcode();
1807  while (!Ops.empty() && isa<Constant>(Ops.back().Op)) {
1808  Constant *C = cast<Constant>(Ops.pop_back_val().Op);
1809  Cst = Cst ? ConstantExpr::get(Opcode, C, Cst) : C;
1810  }
1811  // If there was nothing but constants then we are done.
1812  if (Ops.empty())
1813  return Cst;
1814 
1815  // Put the combined constant back at the end of the operand list, except if
1816  // there is no point. For example, an add of 0 gets dropped here, while a
1817  // multiplication by zero turns the whole expression into zero.
1818  if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) {
1819  if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType()))
1820  return Cst;
1821  Ops.push_back(ValueEntry(0, Cst));
1822  }
1823 
1824  if (Ops.size() == 1) return Ops[0].Op;
1825 
1826  // Handle destructive annihilation due to identities between elements in the
1827  // argument list here.
1828  unsigned NumOps = Ops.size();
1829  switch (Opcode) {
1830  default: break;
1831  case Instruction::And:
1832  case Instruction::Or:
1833  if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
1834  return Result;
1835  break;
1836 
1837  case Instruction::Xor:
1838  if (Value *Result = OptimizeXor(I, Ops))
1839  return Result;
1840  break;
1841 
1842  case Instruction::Add:
1843  case Instruction::FAdd:
1844  if (Value *Result = OptimizeAdd(I, Ops))
1845  return Result;
1846  break;
1847 
1848  case Instruction::Mul:
1849  case Instruction::FMul:
1850  if (Value *Result = OptimizeMul(I, Ops))
1851  return Result;
1852  break;
1853  }
1854 
1855  if (Ops.size() != NumOps)
1856  return OptimizeExpression(I, Ops);
1857  return nullptr;
1858 }
1859 
1860 // Remove dead instructions and if any operands are trivially dead add them to
1861 // Insts so they will be removed as well.
1862 void ReassociatePass::RecursivelyEraseDeadInsts(
1864  assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
1865  SmallVector<Value *, 4> Ops(I->op_begin(), I->op_end());
1866  ValueRankMap.erase(I);
1867  Insts.remove(I);
1868  RedoInsts.remove(I);
1869  I->eraseFromParent();
1870  for (auto Op : Ops)
1871  if (Instruction *OpInst = dyn_cast<Instruction>(Op))
1872  if (OpInst->use_empty())
1873  Insts.insert(OpInst);
1874 }
1875 
1876 /// Zap the given instruction, adding interesting operands to the work list.
1877 void ReassociatePass::EraseInst(Instruction *I) {
1878  assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
1879  DEBUG(dbgs() << "Erasing dead inst: "; I->dump());
1880 
1881  SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
1882  // Erase the dead instruction.
1883  ValueRankMap.erase(I);
1884  RedoInsts.remove(I);
1885  I->eraseFromParent();
1886  // Optimize its operands.
1887  SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
1888  for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1889  if (Instruction *Op = dyn_cast<Instruction>(Ops[i])) {
1890  // If this is a node in an expression tree, climb to the expression root
1891  // and add that since that's where optimization actually happens.
1892  unsigned Opcode = Op->getOpcode();
1893  while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode &&
1894  Visited.insert(Op).second)
1895  Op = Op->user_back();
1896  RedoInsts.insert(Op);
1897  }
1898 
1899  MadeChange = true;
1900 }
1901 
1902 // Canonicalize expressions of the following form:
1903 // x + (-Constant * y) -> x - (Constant * y)
1904 // x - (-Constant * y) -> x + (Constant * y)
1905 Instruction *ReassociatePass::canonicalizeNegConstExpr(Instruction *I) {
1906  if (!I->hasOneUse() || I->getType()->isVectorTy())
1907  return nullptr;
1908 
1909  // Must be a fmul or fdiv instruction.
1910  unsigned Opcode = I->getOpcode();
1911  if (Opcode != Instruction::FMul && Opcode != Instruction::FDiv)
1912  return nullptr;
1913 
1914  auto *C0 = dyn_cast<ConstantFP>(I->getOperand(0));
1915  auto *C1 = dyn_cast<ConstantFP>(I->getOperand(1));
1916 
1917  // Both operands are constant, let it get constant folded away.
1918  if (C0 && C1)
1919  return nullptr;
1920 
1921  ConstantFP *CF = C0 ? C0 : C1;
1922 
1923  // Must have one constant operand.
1924  if (!CF)
1925  return nullptr;
1926 
1927  // Must be a negative ConstantFP.
1928  if (!CF->isNegative())
1929  return nullptr;
1930 
1931  // User must be a binary operator with one or more uses.
1932  Instruction *User = I->user_back();
1933  if (!isa<BinaryOperator>(User) || User->use_empty())
1934  return nullptr;
1935 
1936  unsigned UserOpcode = User->getOpcode();
1937  if (UserOpcode != Instruction::FAdd && UserOpcode != Instruction::FSub)
1938  return nullptr;
1939 
1940  // Subtraction is not commutative. Explicitly, the following transform is
1941  // not valid: (-Constant * y) - x -> x + (Constant * y)
1942  if (!User->isCommutative() && User->getOperand(1) != I)
1943  return nullptr;
1944 
1945  // Don't canonicalize x + (-Constant * y) -> x - (Constant * y), if the
1946  // resulting subtract will be broken up later. This can get us into an
1947  // infinite loop during reassociation.
1948  if (UserOpcode == Instruction::FAdd && ShouldBreakUpSubtract(User))
1949  return nullptr;
1950 
1951  // Change the sign of the constant.
1952  APFloat Val = CF->getValueAPF();
1953  Val.changeSign();
1954  I->setOperand(C0 ? 0 : 1, ConstantFP::get(CF->getContext(), Val));
1955 
1956  // Canonicalize I to RHS to simplify the next bit of logic. E.g.,
1957  // ((-Const*y) + x) -> (x + (-Const*y)).
1958  if (User->getOperand(0) == I && User->isCommutative())
1959  cast<BinaryOperator>(User)->swapOperands();
1960 
1961  Value *Op0 = User->getOperand(0);
1962  Value *Op1 = User->getOperand(1);
1963  BinaryOperator *NI;
1964  switch (UserOpcode) {
1965  default:
1966  llvm_unreachable("Unexpected Opcode!");
1967  case Instruction::FAdd:
1968  NI = BinaryOperator::CreateFSub(Op0, Op1);
1969  NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
1970  break;
1971  case Instruction::FSub:
1972  NI = BinaryOperator::CreateFAdd(Op0, Op1);
1973  NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
1974  break;
1975  }
1976 
1977  NI->insertBefore(User);
1978  NI->setName(User->getName());
1979  User->replaceAllUsesWith(NI);
1980  NI->setDebugLoc(I->getDebugLoc());
1981  RedoInsts.insert(I);
1982  MadeChange = true;
1983  return NI;
1984 }
1985 
1986 /// Inspect and optimize the given instruction. Note that erasing
1987 /// instructions is not allowed.
1988 void ReassociatePass::OptimizeInst(Instruction *I) {
1989  // Only consider operations that we understand.
1990  if (!isa<BinaryOperator>(I))
1991  return;
1992 
1993  if (I->getOpcode() == Instruction::Shl && isa<ConstantInt>(I->getOperand(1)))
1994  // If an operand of this shift is a reassociable multiply, or if the shift
1995  // is used by a reassociable multiply or add, turn into a multiply.
1996  if (isReassociableOp(I->getOperand(0), Instruction::Mul) ||
1997  (I->hasOneUse() &&
1998  (isReassociableOp(I->user_back(), Instruction::Mul) ||
2000  Instruction *NI = ConvertShiftToMul(I);
2001  RedoInsts.insert(I);
2002  MadeChange = true;
2003  I = NI;
2004  }
2005 
2006  // Canonicalize negative constants out of expressions.
2007  if (Instruction *Res = canonicalizeNegConstExpr(I))
2008  I = Res;
2009 
2010  // Commute binary operators, to canonicalize the order of their operands.
2011  // This can potentially expose more CSE opportunities, and makes writing other
2012  // transformations simpler.
2013  if (I->isCommutative())
2014  canonicalizeOperands(I);
2015 
2016  // Don't optimize floating-point instructions unless they are 'fast'.
2017  if (I->getType()->isFPOrFPVectorTy() && !I->isFast())
2018  return;
2019 
2020  // Do not reassociate boolean (i1) expressions. We want to preserve the
2021  // original order of evaluation for short-circuited comparisons that
2022  // SimplifyCFG has folded to AND/OR expressions. If the expression
2023  // is not further optimized, it is likely to be transformed back to a
2024  // short-circuited form for code gen, and the source order may have been
2025  // optimized for the most likely conditions.
2026  if (I->getType()->isIntegerTy(1))
2027  return;
2028 
2029  // If this is a subtract instruction which is not already in negate form,
2030  // see if we can convert it to X+-Y.
2031  if (I->getOpcode() == Instruction::Sub) {
2032  if (ShouldBreakUpSubtract(I)) {
2033  Instruction *NI = BreakUpSubtract(I, RedoInsts);
2034  RedoInsts.insert(I);
2035  MadeChange = true;
2036  I = NI;
2037  } else if (BinaryOperator::isNeg(I)) {
2038  // Otherwise, this is a negation. See if the operand is a multiply tree
2039  // and if this is not an inner node of a multiply tree.
2040  if (isReassociableOp(I->getOperand(1), Instruction::Mul) &&
2041  (!I->hasOneUse() ||
2042  !isReassociableOp(I->user_back(), Instruction::Mul))) {
2044  // If the negate was simplified, revisit the users to see if we can
2045  // reassociate further.
2046  for (User *U : NI->users()) {
2047  if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
2048  RedoInsts.insert(Tmp);
2049  }
2050  RedoInsts.insert(I);
2051  MadeChange = true;
2052  I = NI;
2053  }
2054  }
2055  } else if (I->getOpcode() == Instruction::FSub) {
2056  if (ShouldBreakUpSubtract(I)) {
2057  Instruction *NI = BreakUpSubtract(I, RedoInsts);
2058  RedoInsts.insert(I);
2059  MadeChange = true;
2060  I = NI;
2061  } else if (BinaryOperator::isFNeg(I)) {
2062  // Otherwise, this is a negation. See if the operand is a multiply tree
2063  // and if this is not an inner node of a multiply tree.
2064  if (isReassociableOp(I->getOperand(1), Instruction::FMul) &&
2065  (!I->hasOneUse() ||
2066  !isReassociableOp(I->user_back(), Instruction::FMul))) {
2067  // If the negate was simplified, revisit the users to see if we can
2068  // reassociate further.
2070  for (User *U : NI->users()) {
2071  if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
2072  RedoInsts.insert(Tmp);
2073  }
2074  RedoInsts.insert(I);
2075  MadeChange = true;
2076  I = NI;
2077  }
2078  }
2079  }
2080 
2081  // If this instruction is an associative binary operator, process it.
2082  if (!I->isAssociative()) return;
2083  BinaryOperator *BO = cast<BinaryOperator>(I);
2084 
2085  // If this is an interior node of a reassociable tree, ignore it until we
2086  // get to the root of the tree, to avoid N^2 analysis.
2087  unsigned Opcode = BO->getOpcode();
2088  if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode) {
2089  // During the initial run we will get to the root of the tree.
2090  // But if we get here while we are redoing instructions, there is no
2091  // guarantee that the root will be visited. So Redo later
2092  if (BO->user_back() != BO &&
2093  BO->getParent() == BO->user_back()->getParent())
2094  RedoInsts.insert(BO->user_back());
2095  return;
2096  }
2097 
2098  // If this is an add tree that is used by a sub instruction, ignore it
2099  // until we process the subtract.
2100  if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
2101  cast<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub)
2102  return;
2103  if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd &&
2104  cast<Instruction>(BO->user_back())->getOpcode() == Instruction::FSub)
2105  return;
2106 
2107  ReassociateExpression(BO);
2108 }
2109 
2110 void ReassociatePass::ReassociateExpression(BinaryOperator *I) {
2111  // First, walk the expression tree, linearizing the tree, collecting the
2112  // operand information.
2114  MadeChange |= LinearizeExprTree(I, Tree);
2116  Ops.reserve(Tree.size());
2117  for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
2118  RepeatedValue E = Tree[i];
2119  Ops.append(E.second.getZExtValue(),
2120  ValueEntry(getRank(E.first), E.first));
2121  }
2122 
2123  DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
2124 
2125  // Now that we have linearized the tree to a list and have gathered all of
2126  // the operands and their ranks, sort the operands by their rank. Use a
2127  // stable_sort so that values with equal ranks will have their relative
2128  // positions maintained (and so the compiler is deterministic). Note that
2129  // this sorts so that the highest ranking values end up at the beginning of
2130  // the vector.
2131  std::stable_sort(Ops.begin(), Ops.end());
2132 
2133  // Now that we have the expression tree in a convenient
2134  // sorted form, optimize it globally if possible.
2135  if (Value *V = OptimizeExpression(I, Ops)) {
2136  if (V == I)
2137  // Self-referential expression in unreachable code.
2138  return;
2139  // This expression tree simplified to something that isn't a tree,
2140  // eliminate it.
2141  DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
2142  I->replaceAllUsesWith(V);
2143  if (Instruction *VI = dyn_cast<Instruction>(V))
2144  if (I->getDebugLoc())
2145  VI->setDebugLoc(I->getDebugLoc());
2146  RedoInsts.insert(I);
2147  ++NumAnnihil;
2148  return;
2149  }
2150 
2151  // We want to sink immediates as deeply as possible except in the case where
2152  // this is a multiply tree used only by an add, and the immediate is a -1.
2153  // In this case we reassociate to put the negation on the outside so that we
2154  // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
2155  if (I->hasOneUse()) {
2156  if (I->getOpcode() == Instruction::Mul &&
2157  cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
2158  isa<ConstantInt>(Ops.back().Op) &&
2159  cast<ConstantInt>(Ops.back().Op)->isMinusOne()) {
2160  ValueEntry Tmp = Ops.pop_back_val();
2161  Ops.insert(Ops.begin(), Tmp);
2162  } else if (I->getOpcode() == Instruction::FMul &&
2163  cast<Instruction>(I->user_back())->getOpcode() ==
2164  Instruction::FAdd &&
2165  isa<ConstantFP>(Ops.back().Op) &&
2166  cast<ConstantFP>(Ops.back().Op)->isExactlyValue(-1.0)) {
2167  ValueEntry Tmp = Ops.pop_back_val();
2168  Ops.insert(Ops.begin(), Tmp);
2169  }
2170  }
2171 
2172  DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
2173 
2174  if (Ops.size() == 1) {
2175  if (Ops[0].Op == I)
2176  // Self-referential expression in unreachable code.
2177  return;
2178 
2179  // This expression tree simplified to something that isn't a tree,
2180  // eliminate it.
2181  I->replaceAllUsesWith(Ops[0].Op);
2182  if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
2183  OI->setDebugLoc(I->getDebugLoc());
2184  RedoInsts.insert(I);
2185  return;
2186  }
2187 
2188  if (Ops.size() > 2 && Ops.size() <= GlobalReassociateLimit) {
2189  // Find the pair with the highest count in the pairmap and move it to the
2190  // back of the list so that it can later be CSE'd.
2191  // example:
2192  // a*b*c*d*e
2193  // if c*e is the most "popular" pair, we can express this as
2194  // (((c*e)*d)*b)*a
2195  unsigned Max = 1;
2196  unsigned BestRank = 0;
2197  std::pair<unsigned, unsigned> BestPair;
2198  unsigned Idx = I->getOpcode() - Instruction::BinaryOpsBegin;
2199  for (unsigned i = 0; i < Ops.size() - 1; ++i)
2200  for (unsigned j = i + 1; j < Ops.size(); ++j) {
2201  unsigned Score = 0;
2202  Value *Op0 = Ops[i].Op;
2203  Value *Op1 = Ops[j].Op;
2204  if (std::less<Value *>()(Op1, Op0))
2205  std::swap(Op0, Op1);
2206  auto it = PairMap[Idx].find({Op0, Op1});
2207  if (it != PairMap[Idx].end())
2208  Score += it->second;
2209 
2210  unsigned MaxRank = std::max(Ops[i].Rank, Ops[j].Rank);
2211  if (Score > Max || (Score == Max && MaxRank < BestRank)) {
2212  BestPair = {i, j};
2213  Max = Score;
2214  BestRank = MaxRank;
2215  }
2216  }
2217  if (Max > 1) {
2218  auto Op0 = Ops[BestPair.first];
2219  auto Op1 = Ops[BestPair.second];
2220  Ops.erase(&Ops[BestPair.second]);
2221  Ops.erase(&Ops[BestPair.first]);
2222  Ops.push_back(Op0);
2223  Ops.push_back(Op1);
2224  }
2225  }
2226  // Now that we ordered and optimized the expressions, splat them back into
2227  // the expression tree, removing any unneeded nodes.
2228  RewriteExprTree(I, Ops);
2229 }
2230 
2231 void
2232 ReassociatePass::BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT) {
2233  // Make a "pairmap" of how often each operand pair occurs.
2234  for (BasicBlock *BI : RPOT) {
2235  for (Instruction &I : *BI) {
2236  if (!I.isAssociative())
2237  continue;
2238 
2239  // Ignore nodes that aren't at the root of trees.
2240  if (I.hasOneUse() && I.user_back()->getOpcode() == I.getOpcode())
2241  continue;
2242 
2243  // Collect all operands in a single reassociable expression.
2244  // Since Reassociate has already been run once, we can assume things
2245  // are already canonical according to Reassociation's regime.
2246  SmallVector<Value *, 8> Worklist = { I.getOperand(0), I.getOperand(1) };
2248  while (!Worklist.empty() && Ops.size() <= GlobalReassociateLimit) {
2249  Value *Op = Worklist.pop_back_val();
2251  if (!OpI || OpI->getOpcode() != I.getOpcode() || !OpI->hasOneUse()) {
2252  Ops.push_back(Op);
2253  continue;
2254  }
2255  // Be paranoid about self-referencing expressions in unreachable code.
2256  if (OpI->getOperand(0) != OpI)
2257  Worklist.push_back(OpI->getOperand(0));
2258  if (OpI->getOperand(1) != OpI)
2259  Worklist.push_back(OpI->getOperand(1));
2260  }
2261  // Skip extremely long expressions.
2262  if (Ops.size() > GlobalReassociateLimit)
2263  continue;
2264 
2265  // Add all pairwise combinations of operands to the pair map.
2266  unsigned BinaryIdx = I.getOpcode() - Instruction::BinaryOpsBegin;
2268  for (unsigned i = 0; i < Ops.size() - 1; ++i) {
2269  for (unsigned j = i + 1; j < Ops.size(); ++j) {
2270  // Canonicalize operand orderings.
2271  Value *Op0 = Ops[i];
2272  Value *Op1 = Ops[j];
2273  if (std::less<Value *>()(Op1, Op0))
2274  std::swap(Op0, Op1);
2275  if (!Visited.insert({Op0, Op1}).second)
2276  continue;
2277  auto res = PairMap[BinaryIdx].insert({{Op0, Op1}, 1});
2278  if (!res.second)
2279  ++res.first->second;
2280  }
2281  }
2282  }
2283  }
2284 }
2285 
2287  // Get the functions basic blocks in Reverse Post Order. This order is used by
2288  // BuildRankMap to pre calculate ranks correctly. It also excludes dead basic
2289  // blocks (it has been seen that the analysis in this pass could hang when
2290  // analysing dead basic blocks).
2292 
2293  // Calculate the rank map for F.
2294  BuildRankMap(F, RPOT);
2295 
2296  // Build the pair map before running reassociate.
2297  // Technically this would be more accurate if we did it after one round
2298  // of reassociation, but in practice it doesn't seem to help much on
2299  // real-world code, so don't waste the compile time running reassociate
2300  // twice.
2301  // If a user wants, they could expicitly run reassociate twice in their
2302  // pass pipeline for further potential gains.
2303  // It might also be possible to update the pair map during runtime, but the
2304  // overhead of that may be large if there's many reassociable chains.
2305  BuildPairMap(RPOT);
2306 
2307  MadeChange = false;
2308 
2309  // Traverse the same blocks that were analysed by BuildRankMap.
2310  for (BasicBlock *BI : RPOT) {
2311  assert(RankMap.count(&*BI) && "BB should be ranked.");
2312  // Optimize every instruction in the basic block.
2313  for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;)
2314  if (isInstructionTriviallyDead(&*II)) {
2315  EraseInst(&*II++);
2316  } else {
2317  OptimizeInst(&*II);
2318  assert(II->getParent() == &*BI && "Moved to a different block!");
2319  ++II;
2320  }
2321 
2322  // Make a copy of all the instructions to be redone so we can remove dead
2323  // instructions.
2324  SetVector<AssertingVH<Instruction>> ToRedo(RedoInsts);
2325  // Iterate over all instructions to be reevaluated and remove trivially dead
2326  // instructions. If any operand of the trivially dead instruction becomes
2327  // dead mark it for deletion as well. Continue this process until all
2328  // trivially dead instructions have been removed.
2329  while (!ToRedo.empty()) {
2330  Instruction *I = ToRedo.pop_back_val();
2331  if (isInstructionTriviallyDead(I)) {
2332  RecursivelyEraseDeadInsts(I, ToRedo);
2333  MadeChange = true;
2334  }
2335  }
2336 
2337  // Now that we have removed dead instructions, we can reoptimize the
2338  // remaining instructions.
2339  while (!RedoInsts.empty()) {
2340  Instruction *I = RedoInsts.pop_back_val();
2342  EraseInst(I);
2343  else
2344  OptimizeInst(I);
2345  }
2346  }
2347 
2348  // We are done with the rank map and pair map.
2349  RankMap.clear();
2350  ValueRankMap.clear();
2351  for (auto &Entry : PairMap)
2352  Entry.clear();
2353 
2354  if (MadeChange) {
2355  PreservedAnalyses PA;
2356  PA.preserveSet<CFGAnalyses>();
2357  PA.preserve<GlobalsAA>();
2358  return PA;
2359  }
2360 
2361  return PreservedAnalyses::all();
2362 }
2363 
2364 namespace {
2365 
2366  class ReassociateLegacyPass : public FunctionPass {
2367  ReassociatePass Impl;
2368 
2369  public:
2370  static char ID; // Pass identification, replacement for typeid
2371 
2372  ReassociateLegacyPass() : FunctionPass(ID) {
2374  }
2375 
2376  bool runOnFunction(Function &F) override {
2377  if (skipFunction(F))
2378  return false;
2379 
2380  FunctionAnalysisManager DummyFAM;
2381  auto PA = Impl.run(F, DummyFAM);
2382  return !PA.areAllPreserved();
2383  }
2384 
2385  void getAnalysisUsage(AnalysisUsage &AU) const override {
2386  AU.setPreservesCFG();
2388  }
2389  };
2390 
2391 } // end anonymous namespace
2392 
2393 char ReassociateLegacyPass::ID = 0;
2394 
2395 INITIALIZE_PASS(ReassociateLegacyPass, "reassociate",
2396  "Reassociate expressions", false, false)
2397 
2398 // Public interface to the Reassociate pass
2400  return new ReassociateLegacyPass();
2401 }
Legacy wrapper pass to provide the GlobalsAAResult object.
uint64_t CallInst * C
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:67
void push_back(const T &Elt)
Definition: SmallVector.h:212
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:245
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
void setFastMathFlags(FastMathFlags FMF)
Convenience function for setting multiple fast-math flags on this instruction, which must be an opera...
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
uint64_t getZExtValue() const
Get zero extended value.
Definition: APInt.h:1542
GCNRegPressure max(const GCNRegPressure &P1, const GCNRegPressure &P2)
LLVM_NODISCARD T pop_back_val()
Definition: SetVector.h:228
static BinaryOperator * LowerNegateToMultiply(Instruction *Neg)
Replace 0-X with X*-1.
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
BinaryOps getOpcode() const
Definition: InstrTypes.h:523
INITIALIZE_PASS(ReassociateLegacyPass, "reassociate", "Reassociate expressions", false, false) FunctionPass *llvm
This is the interface for a simple mod/ref and alias analysis over globals.
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:63
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:136
bool isIdempotent() const
Return true if the instruction is idempotent:
Definition: Instruction.h:470
Utility class representing a non-constant Xor-operand.
Definition: Reassociate.cpp:94
static Constant * getBinOpIdentity(unsigned Opcode, Type *Ty)
Return the identity for the given binary operation, i.e.
Definition: Constants.cpp:2239
nary reassociate
Utility class representing a base and exponent pair which form one factor of some product...
Definition: Reassociate.h:59
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:738
void deleteValue()
Delete a pointer to a generic Value.
Definition: Value.cpp:99
STATISTIC(NumFunctions, "Total number of functions")
F(f)
static unsigned FindInOperandList(const SmallVectorImpl< ValueEntry > &Ops, unsigned i, Value *X)
Scan backwards and forwards among values with the same rank as element i to see if X exists...
std::pair< Value *, APInt > RepeatedValue
bool isVectorTy() const
True if this is an instance of VectorType.
Definition: Type.h:227
void changeSign()
Definition: APFloat.h:1050
void reserve(size_type N)
Definition: SmallVector.h:378
Reassociate commutative expressions.
Definition: Reassociate.h:71
op_iterator op_begin()
Definition: User.h:214
unsigned getBitWidth() const
Return the number of bits in the APInt.
Definition: APInt.h:1488
static Constant * getNullValue(Type *Ty)
Constructor to create a &#39;0&#39; constant of arbitrary type.
Definition: Constants.cpp:232
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:252
bool swapOperands()
Exchange the two operands to this instruction.
void dump() const
Support for debugging, callable in GDB: V->dump()
Definition: AsmWriter.cpp:3648
bool match(Val *V, const Pattern &P)
Definition: PatternMatch.h:49
static const Value * getNegArgument(const Value *BinOp)
Helper functions to extract the unary argument of a NEG, FNEG or NOT operation implemented via Sub...
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
bool isNilpotent() const
Return true if the instruction is nilpotent:
Definition: Instruction.h:484
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:42
static bool collectMultiplyFactors(SmallVectorImpl< ValueEntry > &Ops, SmallVectorImpl< Factor > &Factors)
Build up a vector of value/power pairs factoring a product.
bool isIntegerTy() const
True if this is an instance of IntegerType.
Definition: Type.h:197
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:707
FunctionPass * createReassociatePass()
static BinaryOperator * BreakUpSubtract(Instruction *Sub, SetVector< AssertingVH< Instruction >> &ToRedo)
If we have (X-Y), and if either X is an add, or if this is only used by an add, transform this into (...
void setName(const Twine &Name)
Change the name of the value.
Definition: Value.cpp:295
This file implements a class to represent arbitrary precision integral constant values and operations...
static Constant * get(unsigned Opcode, Constant *C1, Constant *C2, unsigned Flags=0, Type *OnlyIfReducedTy=nullptr)
get - Return a binary or shift operator constant expression, folding if possible. ...
Definition: Constants.cpp:1747
static Value * OptimizeAndOrXor(unsigned Opcode, SmallVectorImpl< ValueEntry > &Ops)
Optimize a series of operands to an &#39;and&#39;, &#39;or&#39;, or &#39;xor&#39; instruction.
FastMathFlags getFastMathFlags() const
Convenience function for getting all the fast-math flags, which must be an operator which supports th...
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
bool getBoolValue() const
Convert APInt to a boolean value.
Definition: APInt.h:471
bool isNegative() const
Return true if the sign bit is set.
Definition: Constants.h:305
void andIRFlags(const Value *V)
Logical &#39;and&#39; of any supported wrapping, exact, and fast-math flags of V and this instruction...
static Value * createAndInstr(Instruction *InsertBefore, Value *Opnd, const APInt &ConstOpnd)
Helper function of CombineXorOpnd().
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:126
auto lower_bound(R &&Range, ForwardIt I) -> decltype(adl_begin(Range))
Provide wrappers to std::lower_bound which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:910
bool isIntOrIntVectorTy() const
Return true if this is an integer type or a vector of integer types.
Definition: Type.h:203
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:439
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:301
static BinaryOperator * CreateAdd(Value *S1, Value *S2, const Twine &Name, Instruction *InsertBefore, Value *FlagsOp)
static const Value * getNotArgument(const Value *BinOp)
Value * getOperand(unsigned i) const
Definition: User.h:154
Type * getScalarType() const
If this is a vector type, return the element type, otherwise return &#39;this&#39;.
Definition: Type.h:301
const BasicBlock & getEntryBlock() const
Definition: Function.h:618
static bool runOnFunction(Function &F, bool PostInlining)
#define P(N)
static Constant * getFNeg(Constant *C)
Definition: Constants.cpp:2139
bool isAllOnesValue() const
Determine if all bits are set.
Definition: APInt.h:389
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
apint_match m_APInt(const APInt *&Res)
Match a ConstantInt or splatted ConstantVector, binding the specified pointer to the contained APInt...
Definition: PatternMatch.h:260
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:282
bool areAllPreserved() const
Test whether all analyses are preserved (and none are abandoned).
Definition: PassManager.h:321
void insertBefore(Instruction *InsertPos)
Insert an unlinked instruction into a basic block immediately before the specified instruction...
Definition: Instruction.cpp:73
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
bool ult(const APInt &RHS) const
Unsigned less than comparison.
Definition: APInt.h:1164
const char * getOpcodeName() const
Definition: Instruction.h:128
static Value * EmitAddTreeOfValues(Instruction *I, SmallVectorImpl< WeakTrackingVH > &Ops)
Emit a tree of add instructions, summing Ops together and returning the result.
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:42
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator begin()
Definition: SmallVector.h:116
SmallSet - This maintains a set of unique values, optimizing for the case when the set is small (less...
Definition: SmallSet.h:36
This file contains the declarations for the subclasses of Constant, which represent the different fla...
ConstantFP - Floating Point Values [float, double].
Definition: Constants.h:264
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:371
static APInt getOneBitSet(unsigned numBits, unsigned BitNo)
Return an APInt with exactly one bit set in the result.
Definition: APInt.h:581
bool isAssociative() const LLVM_READONLY
Return true if the instruction is associative:
Represent the analysis usage information of a pass.
op_iterator op_end()
Definition: User.h:216
This file declares a class to represent arbitrary precision floating point values and provide a varie...
bool isFast() const
Determine whether all fast-math-flags are set.
Analysis pass providing a never-invalidated alias analysis result.
Value * getSymbolicPart() const
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
static bool isNot(const Value *V)
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:382
self_iterator getIterator()
Definition: ilist_node.h:82
std::pair< NoneType, bool > insert(const T &V)
insert - Insert an element into the set if it isn&#39;t already there.
Definition: SmallSet.h:81
static Constant * getAllOnesValue(Type *Ty)
Get the all ones value.
Definition: Constants.cpp:286
NUW NUW NUW NUW Exact static Exact BinaryOperator * CreateNeg(Value *Op, const Twine &Name="", Instruction *InsertBefore=nullptr)
Helper functions to construct and inspect unary operations (NEG and NOT) via binary operators SUB and...
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1356
iterator erase(const_iterator CI)
Definition: SmallVector.h:447
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
static unsigned CarmichaelShift(unsigned Bitwidth)
Returns k such that lambda(2^Bitwidth) = 2^k, where lambda is the Carmichael function.
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
Value * CreateMul(Value *LHS, Value *RHS, const Twine &Name="", bool HasNUW=false, bool HasNSW=false)
Definition: IRBuilder.h:976
const APInt & getConstPart() const
const APFloat & getValueAPF() const
Definition: Constants.h:299
static BinaryOperator * CreateFNeg(Value *Op, const Twine &Name="", Instruction *InsertBefore=nullptr)
void setHasNoSignedWrap(bool b=true)
Set or clear the nsw flag on this instruction, which must be an operator which supports this flag...
Iterator for intrusive lists based on ilist_node.
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
This is the shared class of boolean and integer constants.
Definition: Constants.h:84
unsigned getScalarSizeInBits() const LLVM_READONLY
If this is a vector type, return the getPrimitiveSizeInBits value for the element type...
Definition: Type.cpp:130
static Value * NegateValue(Value *V, Instruction *BI, SetVector< AssertingVH< Instruction >> &ToRedo)
Insert instructions before the instruction pointed to by BI, that computes the negative version of th...
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:862
unsigned getSymbolicRank() const
Instruction * user_back()
Specialize the methods defined in Value, as we know that an instruction can only be used by other ins...
Definition: Instruction.h:64
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:383
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:585
void setSymbolicRank(unsigned R)
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:285
static Constant * get(Type *Ty, double V)
This returns a ConstantFP, or a vector containing a splat of a ConstantFP, for the specified value in...
Definition: Constants.cpp:648
Value handle that asserts if the Value is deleted.
Definition: ValueHandle.h:238
bool isCommutative() const
Return true if the instruction is commutative:
Definition: Instruction.h:452
void setOperand(unsigned i, Value *Val)
Definition: User.h:159
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:923
const Module * getModule() const
Return the module owning the function this instruction belongs to or nullptr it the function does not...
Definition: Instruction.cpp:55
static bool isNeg(const Value *V)
Check if the given Value is a NEG, FNeg, or NOT instruction.
Class for arbitrary precision integers.
Definition: APInt.h:69
static Value * buildMultiplyTree(IRBuilder<> &Builder, SmallVectorImpl< Value *> &Ops)
Build a tree of multiplies, computing the product of Ops.
static BinaryOperator * Create(BinaryOps Op, Value *S1, Value *S2, const Twine &Name=Twine(), Instruction *InsertBefore=nullptr)
Construct a binary instruction, given the opcode and the two operands.
iterator_range< user_iterator > users()
Definition: Value.h:405
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:114
iterator insert(iterator I, T &&Elt)
Definition: SmallVector.h:480
void append(in_iter in_start, in_iter in_end)
Add the specified range to the end of the SmallVector.
Definition: SmallVector.h:396
amdgpu Simplify well known AMD library false Value Value * Arg
static void FindSingleUseMultiplyFactors(Value *V, SmallVectorImpl< Value *> &Factors)
If V is a single-use multiply, recursively add its operands as factors, otherwise add V to the list o...
static Constant * getNeg(Constant *C, bool HasNUW=false, bool HasNSW=false)
Definition: Constants.cpp:2132
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:120
iterator insert(iterator where, pointer New)
Definition: ilist.h:241
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:285
bool mayBeMemoryDependent(const Instruction &I)
Returns true if the result or effects of the given instructions I depend on or influence global memor...
void emplace_back(ArgTypes &&... Args)
Definition: SmallVector.h:654
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
static bool isFNeg(const Value *V, bool IgnoreZeroSign=false)
void preserveSet()
Mark an analysis set as preserved.
Definition: PassManager.h:189
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:224
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:108
static void PrintOps(Instruction *I, const SmallVectorImpl< ValueEntry > &Ops)
Print out the expression identified in the Ops list.
Definition: Reassociate.cpp:74
static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode)
Add the extra weight &#39;RHS&#39; to the existing weight &#39;LHS&#39;, reducing the combined weight using any speci...
#define I(x, y, z)
Definition: MD5.cpp:58
bool empty() const
Determine if the SetVector is empty or not.
Definition: SetVector.h:73
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
static Constant * getShl(Constant *C1, Constant *C2, bool HasNUW=false, bool HasNSW=false)
Definition: Constants.cpp:2222
void preserve()
Mark an analysis as preserved.
Definition: PassManager.h:174
static BinaryOperator * CreateNeg(Value *S1, const Twine &Name, Instruction *InsertBefore, Value *FlagsOp)
bool isMinValue() const
Determine if this is the smallest unsigned value.
Definition: APInt.h:430
bool isFPOrFPVectorTy() const
Return true if this is a FP type or a vector of FP.
Definition: Type.h:185
static int const Threshold
TODO: Write a new FunctionPass AliasAnalysis so that it can keep a cache.
void setHasNoUnsignedWrap(bool b=true)
Set or clear the nsw flag on this instruction, which must be an operator which supports this flag...
static BinaryOperator * ConvertShiftToMul(Instruction *Shl)
If this is a shift of a reassociable multiply or is used by one, change this into a multiply by a con...
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
user_iterator user_begin()
Definition: Value.h:381
void initializeReassociateLegacyPassPass(PassRegistry &)
unsigned getPrimitiveSizeInBits() const LLVM_READONLY
Return the basic size of this type if it is a primitive type.
Definition: Type.cpp:115
bool isInstructionTriviallyDead(Instruction *I, const TargetLibraryInfo *TLI=nullptr)
Return true if the result produced by the instruction is not used, and the instruction has no side ef...
Definition: Local.cpp:346
LLVM Value Representation.
Definition: Value.h:73
A vector that has set insertion semantics.
Definition: SetVector.h:41
void clearSubclassOptionalData()
Clear the optional flags contained in this value.
Definition: Value.h:481
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
void setFastMathFlags(FastMathFlags NewFMF)
Set the fast-math flags to be used with generated fp-math operators.
Definition: IRBuilder.h:221
void moveBefore(Instruction *MovePos)
Unlink this instruction from its current basic block and insert it into the basic block that MovePos ...
Definition: Instruction.cpp:86
static BinaryOperator * isReassociableOp(Value *V, unsigned Opcode)
Return true if V is an instruction of the specified opcode and if it only has one use...
Invoke instruction.
#define DEBUG(X)
Definition: Debug.h:118
IRTranslator LLVM IR MI
bool hasOneUse() const
Return true if there is exactly one user of this value.
Definition: Value.h:418
Convenience struct for specifying and reasoning about fast-math flags.
Definition: Operator.h:160
A container for analyses that lazily runs them and caches their results.
static bool ShouldBreakUpSubtract(Instruction *Sub)
Return true if we should break up this subtract of X-Y into (X + -Y).
static APInt getNullValue(unsigned numBits)
Get the &#39;0&#39; value.
Definition: APInt.h:562
This header defines various interfaces for pass management in LLVM.
static BinaryOperator * CreateMul(Value *S1, Value *S2, const Twine &Name, Instruction *InsertBefore, Value *FlagsOp)
Value * CreateFMul(Value *LHS, Value *RHS, const Twine &Name="", MDNode *FPMathTag=nullptr)
Definition: IRBuilder.h:990
static Constant * getBinOpAbsorber(unsigned Opcode, Type *Ty)
Return the absorbing element for the given binary operation, i.e.
Definition: Constants.cpp:2258
static bool LinearizeExprTree(BinaryOperator *I, SmallVectorImpl< RepeatedValue > &Ops)
Given an associative binary expression, return the leaf nodes in Ops along with their weights (how ma...
bool use_empty() const
Definition: Value.h:328
iterator_range< arg_iterator > args()
Definition: Function.h:667
bool isNullValue() const
Determine if all bits are clear.
Definition: APInt.h:399
cmpResult compare(const APFloat &RHS) const
Definition: APFloat.h:1102
const BasicBlock * getParent() const
Definition: Instruction.h:67
PreservedAnalyses run(Function &F, FunctionAnalysisManager &)