LLVM  4.0.0
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/DenseMap.h"
26 #include "llvm/ADT/STLExtras.h"
27 #include "llvm/ADT/SetVector.h"
28 #include "llvm/ADT/Statistic.h"
31 #include "llvm/IR/CFG.h"
32 #include "llvm/IR/Constants.h"
33 #include "llvm/IR/DerivedTypes.h"
34 #include "llvm/IR/Function.h"
35 #include "llvm/IR/IRBuilder.h"
36 #include "llvm/IR/Instructions.h"
37 #include "llvm/IR/IntrinsicInst.h"
38 #include "llvm/IR/ValueHandle.h"
39 #include "llvm/Pass.h"
40 #include "llvm/Support/Debug.h"
42 #include "llvm/Transforms/Scalar.h"
44 #include <algorithm>
45 using namespace llvm;
46 using namespace reassociate;
47 
48 #define DEBUG_TYPE "reassociate"
49 
50 STATISTIC(NumChanged, "Number of insts reassociated");
51 STATISTIC(NumAnnihil, "Number of expr tree annihilated");
52 STATISTIC(NumFactor , "Number of multiplies factored");
53 
54 #ifndef NDEBUG
55 /// Print out the expression identified in the Ops list.
56 ///
58  Module *M = I->getModule();
59  dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
60  << *Ops[0].Op->getType() << '\t';
61  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
62  dbgs() << "[ ";
63  Ops[i].Op->printAsOperand(dbgs(), false, M);
64  dbgs() << ", #" << Ops[i].Rank << "] ";
65  }
66 }
67 #endif
68 
69 /// Utility class representing a non-constant Xor-operand. We classify
70 /// non-constant Xor-Operands into two categories:
71 /// C1) The operand is in the form "X & C", where C is a constant and C != ~0
72 /// C2)
73 /// C2.1) The operand is in the form of "X | C", where C is a non-zero
74 /// constant.
75 /// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
76 /// operand as "E | 0"
78 public:
79  XorOpnd(Value *V);
80 
81  bool isInvalid() const { return SymbolicPart == nullptr; }
82  bool isOrExpr() const { return isOr; }
83  Value *getValue() const { return OrigVal; }
84  Value *getSymbolicPart() const { return SymbolicPart; }
85  unsigned getSymbolicRank() const { return SymbolicRank; }
86  const APInt &getConstPart() const { return ConstPart; }
87 
88  void Invalidate() { SymbolicPart = OrigVal = nullptr; }
89  void setSymbolicRank(unsigned R) { SymbolicRank = R; }
90 
91 private:
92  Value *OrigVal;
93  Value *SymbolicPart;
94  APInt ConstPart;
95  unsigned SymbolicRank;
96  bool isOr;
97 };
98 
100  assert(!isa<ConstantInt>(V) && "No ConstantInt");
101  OrigVal = V;
103  SymbolicRank = 0;
104 
105  if (I && (I->getOpcode() == Instruction::Or ||
106  I->getOpcode() == Instruction::And)) {
107  Value *V0 = I->getOperand(0);
108  Value *V1 = I->getOperand(1);
109  if (isa<ConstantInt>(V0))
110  std::swap(V0, V1);
111 
112  if (ConstantInt *C = dyn_cast<ConstantInt>(V1)) {
113  ConstPart = C->getValue();
114  SymbolicPart = V0;
115  isOr = (I->getOpcode() == Instruction::Or);
116  return;
117  }
118  }
119 
120  // view the operand as "V | 0"
121  SymbolicPart = V;
122  ConstPart = APInt::getNullValue(V->getType()->getIntegerBitWidth());
123  isOr = true;
124 }
125 
126 /// Return true if V is an instruction of the specified opcode and if it
127 /// only has one use.
128 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
129  if (V->hasOneUse() && isa<Instruction>(V) &&
130  cast<Instruction>(V)->getOpcode() == Opcode &&
131  (!isa<FPMathOperator>(V) ||
132  cast<Instruction>(V)->hasUnsafeAlgebra()))
133  return cast<BinaryOperator>(V);
134  return nullptr;
135 }
136 
137 static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1,
138  unsigned Opcode2) {
139  if (V->hasOneUse() && isa<Instruction>(V) &&
140  (cast<Instruction>(V)->getOpcode() == Opcode1 ||
141  cast<Instruction>(V)->getOpcode() == Opcode2) &&
142  (!isa<FPMathOperator>(V) ||
143  cast<Instruction>(V)->hasUnsafeAlgebra()))
144  return cast<BinaryOperator>(V);
145  return nullptr;
146 }
147 
148 void ReassociatePass::BuildRankMap(Function &F,
150  unsigned i = 2;
151 
152  // Assign distinct ranks to function arguments.
153  for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I) {
154  ValueRankMap[&*I] = ++i;
155  DEBUG(dbgs() << "Calculated Rank[" << I->getName() << "] = " << i << "\n");
156  }
157 
158  // Traverse basic blocks in ReversePostOrder
159  for (BasicBlock *BB : RPOT) {
160  unsigned BBRank = RankMap[BB] = ++i << 16;
161 
162  // Walk the basic block, adding precomputed ranks for any instructions that
163  // we cannot move. This ensures that the ranks for these instructions are
164  // all different in the block.
165  for (Instruction &I : *BB)
166  if (mayBeMemoryDependent(I))
167  ValueRankMap[&I] = ++BBRank;
168  }
169 }
170 
171 unsigned ReassociatePass::getRank(Value *V) {
173  if (!I) {
174  if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
175  return 0; // Otherwise it's a global or constant, rank 0.
176  }
177 
178  if (unsigned Rank = ValueRankMap[I])
179  return Rank; // Rank already known?
180 
181  // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
182  // we can reassociate expressions for code motion! Since we do not recurse
183  // for PHI nodes, we cannot have infinite recursion here, because there
184  // cannot be loops in the value graph that do not go through PHI nodes.
185  unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
186  for (unsigned i = 0, e = I->getNumOperands();
187  i != e && Rank != MaxRank; ++i)
188  Rank = std::max(Rank, getRank(I->getOperand(i)));
189 
190  // If this is a not or neg instruction, do not count it for rank. This
191  // assures us that X and ~X will have the same rank.
194  ++Rank;
195 
196  DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " << Rank << "\n");
197 
198  return ValueRankMap[I] = Rank;
199 }
200 
201 // Canonicalize constants to RHS. Otherwise, sort the operands by rank.
202 void ReassociatePass::canonicalizeOperands(Instruction *I) {
203  assert(isa<BinaryOperator>(I) && "Expected binary operator.");
204  assert(I->isCommutative() && "Expected commutative operator.");
205 
206  Value *LHS = I->getOperand(0);
207  Value *RHS = I->getOperand(1);
208  unsigned LHSRank = getRank(LHS);
209  unsigned RHSRank = getRank(RHS);
210 
211  if (isa<Constant>(RHS))
212  return;
213 
214  if (isa<Constant>(LHS) || RHSRank < LHSRank)
215  cast<BinaryOperator>(I)->swapOperands();
216 }
217 
218 static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name,
219  Instruction *InsertBefore, Value *FlagsOp) {
220  if (S1->getType()->isIntOrIntVectorTy())
221  return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore);
222  else {
223  BinaryOperator *Res =
224  BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore);
225  Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
226  return Res;
227  }
228 }
229 
230 static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name,
231  Instruction *InsertBefore, Value *FlagsOp) {
232  if (S1->getType()->isIntOrIntVectorTy())
233  return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore);
234  else {
235  BinaryOperator *Res =
236  BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore);
237  Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
238  return Res;
239  }
240 }
241 
243  Instruction *InsertBefore, Value *FlagsOp) {
244  if (S1->getType()->isIntOrIntVectorTy())
245  return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
246  else {
247  BinaryOperator *Res = BinaryOperator::CreateFNeg(S1, Name, InsertBefore);
248  Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
249  return Res;
250  }
251 }
252 
253 /// Replace 0-X with X*-1.
255  Type *Ty = Neg->getType();
256  Constant *NegOne = Ty->isIntOrIntVectorTy() ?
258 
259  BinaryOperator *Res = CreateMul(Neg->getOperand(1), NegOne, "", Neg, Neg);
260  Neg->setOperand(1, Constant::getNullValue(Ty)); // Drop use of op.
261  Res->takeName(Neg);
262  Neg->replaceAllUsesWith(Res);
263  Res->setDebugLoc(Neg->getDebugLoc());
264  return Res;
265 }
266 
267 /// Returns k such that lambda(2^Bitwidth) = 2^k, where lambda is the Carmichael
268 /// function. This means that x^(2^k) === 1 mod 2^Bitwidth for
269 /// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic.
270 /// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every
271 /// even x in Bitwidth-bit arithmetic.
272 static unsigned CarmichaelShift(unsigned Bitwidth) {
273  if (Bitwidth < 3)
274  return Bitwidth - 1;
275  return Bitwidth - 2;
276 }
277 
278 /// Add the extra weight 'RHS' to the existing weight 'LHS',
279 /// reducing the combined weight using any special properties of the operation.
280 /// The existing weight LHS represents the computation X op X op ... op X where
281 /// X occurs LHS times. The combined weight represents X op X op ... op X with
282 /// X occurring LHS + RHS times. If op is "Xor" for example then the combined
283 /// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even;
284 /// the routine returns 1 in LHS in the first case, and 0 in LHS in the second.
285 static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) {
286  // If we were working with infinite precision arithmetic then the combined
287  // weight would be LHS + RHS. But we are using finite precision arithmetic,
288  // and the APInt sum LHS + RHS may not be correct if it wraps (it is correct
289  // for nilpotent operations and addition, but not for idempotent operations
290  // and multiplication), so it is important to correctly reduce the combined
291  // weight back into range if wrapping would be wrong.
292 
293  // If RHS is zero then the weight didn't change.
294  if (RHS.isMinValue())
295  return;
296  // If LHS is zero then the combined weight is RHS.
297  if (LHS.isMinValue()) {
298  LHS = RHS;
299  return;
300  }
301  // From this point on we know that neither LHS nor RHS is zero.
302 
303  if (Instruction::isIdempotent(Opcode)) {
304  // Idempotent means X op X === X, so any non-zero weight is equivalent to a
305  // weight of 1. Keeping weights at zero or one also means that wrapping is
306  // not a problem.
307  assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
308  return; // Return a weight of 1.
309  }
310  if (Instruction::isNilpotent(Opcode)) {
311  // Nilpotent means X op X === 0, so reduce weights modulo 2.
312  assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
313  LHS = 0; // 1 + 1 === 0 modulo 2.
314  return;
315  }
316  if (Opcode == Instruction::Add || Opcode == Instruction::FAdd) {
317  // TODO: Reduce the weight by exploiting nsw/nuw?
318  LHS += RHS;
319  return;
320  }
321 
322  assert((Opcode == Instruction::Mul || Opcode == Instruction::FMul) &&
323  "Unknown associative operation!");
324  unsigned Bitwidth = LHS.getBitWidth();
325  // If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth
326  // can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth
327  // bit number x, since either x is odd in which case x^CM = 1, or x is even in
328  // which case both x^W and x^(W - CM) are zero. By subtracting off multiples
329  // of CM like this weights can always be reduced to the range [0, CM+Bitwidth)
330  // which by a happy accident means that they can always be represented using
331  // Bitwidth bits.
332  // TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than
333  // the Carmichael number).
334  if (Bitwidth > 3) {
335  /// CM - The value of Carmichael's lambda function.
336  APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth));
337  // Any weight W >= Threshold can be replaced with W - CM.
338  APInt Threshold = CM + Bitwidth;
339  assert(LHS.ult(Threshold) && RHS.ult(Threshold) && "Weights not reduced!");
340  // For Bitwidth 4 or more the following sum does not overflow.
341  LHS += RHS;
342  while (LHS.uge(Threshold))
343  LHS -= CM;
344  } else {
345  // To avoid problems with overflow do everything the same as above but using
346  // a larger type.
347  unsigned CM = 1U << CarmichaelShift(Bitwidth);
348  unsigned Threshold = CM + Bitwidth;
349  assert(LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold &&
350  "Weights not reduced!");
351  unsigned Total = LHS.getZExtValue() + RHS.getZExtValue();
352  while (Total >= Threshold)
353  Total -= CM;
354  LHS = Total;
355  }
356 }
357 
358 typedef std::pair<Value*, APInt> RepeatedValue;
359 
360 /// Given an associative binary expression, return the leaf
361 /// nodes in Ops along with their weights (how many times the leaf occurs). The
362 /// original expression is the same as
363 /// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
364 /// op
365 /// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
366 /// op
367 /// ...
368 /// op
369 /// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
370 ///
371 /// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
372 ///
373 /// This routine may modify the function, in which case it returns 'true'. The
374 /// changes it makes may well be destructive, changing the value computed by 'I'
375 /// to something completely different. Thus if the routine returns 'true' then
376 /// you MUST either replace I with a new expression computed from the Ops array,
377 /// or use RewriteExprTree to put the values back in.
378 ///
379 /// A leaf node is either not a binary operation of the same kind as the root
380 /// node 'I' (i.e. is not a binary operator at all, or is, but with a different
381 /// opcode), or is the same kind of binary operator but has a use which either
382 /// does not belong to the expression, or does belong to the expression but is
383 /// a leaf node. Every leaf node has at least one use that is a non-leaf node
384 /// of the expression, while for non-leaf nodes (except for the root 'I') every
385 /// use is a non-leaf node of the expression.
386 ///
387 /// For example:
388 /// expression graph node names
389 ///
390 /// + | I
391 /// / \ |
392 /// + + | A, B
393 /// / \ / \ |
394 /// * + * | C, D, E
395 /// / \ / \ / \ |
396 /// + * | F, G
397 ///
398 /// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
399 /// that order) (C, 1), (E, 1), (F, 2), (G, 2).
400 ///
401 /// The expression is maximal: if some instruction is a binary operator of the
402 /// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
403 /// then the instruction also belongs to the expression, is not a leaf node of
404 /// it, and its operands also belong to the expression (but may be leaf nodes).
405 ///
406 /// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
407 /// order to ensure that every non-root node in the expression has *exactly one*
408 /// use by a non-leaf node of the expression. This destruction means that the
409 /// caller MUST either replace 'I' with a new expression or use something like
410 /// RewriteExprTree to put the values back in if the routine indicates that it
411 /// made a change by returning 'true'.
412 ///
413 /// In the above example either the right operand of A or the left operand of B
414 /// will be replaced by undef. If it is B's operand then this gives:
415 ///
416 /// + | I
417 /// / \ |
418 /// + + | A, B - operand of B replaced with undef
419 /// / \ \ |
420 /// * + * | C, D, E
421 /// / \ / \ / \ |
422 /// + * | F, G
423 ///
424 /// Note that such undef operands can only be reached by passing through 'I'.
425 /// For example, if you visit operands recursively starting from a leaf node
426 /// then you will never see such an undef operand unless you get back to 'I',
427 /// which requires passing through a phi node.
428 ///
429 /// Note that this routine may also mutate binary operators of the wrong type
430 /// that have all uses inside the expression (i.e. only used by non-leaf nodes
431 /// of the expression) if it can turn them into binary operators of the right
432 /// type and thus make the expression bigger.
433 
436  DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
437  unsigned Bitwidth = I->getType()->getScalarType()->getPrimitiveSizeInBits();
438  unsigned Opcode = I->getOpcode();
439  assert(I->isAssociative() && I->isCommutative() &&
440  "Expected an associative and commutative operation!");
441 
442  // Visit all operands of the expression, keeping track of their weight (the
443  // number of paths from the expression root to the operand, or if you like
444  // the number of times that operand occurs in the linearized expression).
445  // For example, if I = X + A, where X = A + B, then I, X and B have weight 1
446  // while A has weight two.
447 
448  // Worklist of non-leaf nodes (their operands are in the expression too) along
449  // with their weights, representing a certain number of paths to the operator.
450  // If an operator occurs in the worklist multiple times then we found multiple
451  // ways to get to it.
452  SmallVector<std::pair<BinaryOperator*, APInt>, 8> Worklist; // (Op, Weight)
453  Worklist.push_back(std::make_pair(I, APInt(Bitwidth, 1)));
454  bool Changed = false;
455 
456  // Leaves of the expression are values that either aren't the right kind of
457  // operation (eg: a constant, or a multiply in an add tree), or are, but have
458  // some uses that are not inside the expression. For example, in I = X + X,
459  // X = A + B, the value X has two uses (by I) that are in the expression. If
460  // X has any other uses, for example in a return instruction, then we consider
461  // X to be a leaf, and won't analyze it further. When we first visit a value,
462  // if it has more than one use then at first we conservatively consider it to
463  // be a leaf. Later, as the expression is explored, we may discover some more
464  // uses of the value from inside the expression. If all uses turn out to be
465  // from within the expression (and the value is a binary operator of the right
466  // kind) then the value is no longer considered to be a leaf, and its operands
467  // are explored.
468 
469  // Leaves - Keeps track of the set of putative leaves as well as the number of
470  // paths to each leaf seen so far.
471  typedef DenseMap<Value*, APInt> LeafMap;
472  LeafMap Leaves; // Leaf -> Total weight so far.
473  SmallVector<Value*, 8> LeafOrder; // Ensure deterministic leaf output order.
474 
475 #ifndef NDEBUG
476  SmallPtrSet<Value*, 8> Visited; // For sanity checking the iteration scheme.
477 #endif
478  while (!Worklist.empty()) {
479  std::pair<BinaryOperator*, APInt> P = Worklist.pop_back_val();
480  I = P.first; // We examine the operands of this binary operator.
481 
482  for (unsigned OpIdx = 0; OpIdx < 2; ++OpIdx) { // Visit operands.
483  Value *Op = I->getOperand(OpIdx);
484  APInt Weight = P.second; // Number of paths to this operand.
485  DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n");
486  assert(!Op->use_empty() && "No uses, so how did we get to it?!");
487 
488  // If this is a binary operation of the right kind with only one use then
489  // add its operands to the expression.
490  if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
491  assert(Visited.insert(Op).second && "Not first visit!");
492  DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n");
493  Worklist.push_back(std::make_pair(BO, Weight));
494  continue;
495  }
496 
497  // Appears to be a leaf. Is the operand already in the set of leaves?
498  LeafMap::iterator It = Leaves.find(Op);
499  if (It == Leaves.end()) {
500  // Not in the leaf map. Must be the first time we saw this operand.
501  assert(Visited.insert(Op).second && "Not first visit!");
502  if (!Op->hasOneUse()) {
503  // This value has uses not accounted for by the expression, so it is
504  // not safe to modify. Mark it as being a leaf.
505  DEBUG(dbgs() << "ADD USES LEAF: " << *Op << " (" << Weight << ")\n");
506  LeafOrder.push_back(Op);
507  Leaves[Op] = Weight;
508  continue;
509  }
510  // No uses outside the expression, try morphing it.
511  } else {
512  // Already in the leaf map.
513  assert(It != Leaves.end() && Visited.count(Op) &&
514  "In leaf map but not visited!");
515 
516  // Update the number of paths to the leaf.
517  IncorporateWeight(It->second, Weight, Opcode);
518 
519 #if 0 // TODO: Re-enable once PR13021 is fixed.
520  // The leaf already has one use from inside the expression. As we want
521  // exactly one such use, drop this new use of the leaf.
522  assert(!Op->hasOneUse() && "Only one use, but we got here twice!");
523  I->setOperand(OpIdx, UndefValue::get(I->getType()));
524  Changed = true;
525 
526  // If the leaf is a binary operation of the right kind and we now see
527  // that its multiple original uses were in fact all by nodes belonging
528  // to the expression, then no longer consider it to be a leaf and add
529  // its operands to the expression.
530  if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) {
531  DEBUG(dbgs() << "UNLEAF: " << *Op << " (" << It->second << ")\n");
532  Worklist.push_back(std::make_pair(BO, It->second));
533  Leaves.erase(It);
534  continue;
535  }
536 #endif
537 
538  // If we still have uses that are not accounted for by the expression
539  // then it is not safe to modify the value.
540  if (!Op->hasOneUse())
541  continue;
542 
543  // No uses outside the expression, try morphing it.
544  Weight = It->second;
545  Leaves.erase(It); // Since the value may be morphed below.
546  }
547 
548  // At this point we have a value which, first of all, is not a binary
549  // expression of the right kind, and secondly, is only used inside the
550  // expression. This means that it can safely be modified. See if we
551  // can usefully morph it into an expression of the right kind.
552  assert((!isa<Instruction>(Op) ||
553  cast<Instruction>(Op)->getOpcode() != Opcode
554  || (isa<FPMathOperator>(Op) &&
555  !cast<Instruction>(Op)->hasUnsafeAlgebra())) &&
556  "Should have been handled above!");
557  assert(Op->hasOneUse() && "Has uses outside the expression tree!");
558 
559  // If this is a multiply expression, turn any internal negations into
560  // multiplies by -1 so they can be reassociated.
561  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op))
562  if ((Opcode == Instruction::Mul && BinaryOperator::isNeg(BO)) ||
563  (Opcode == Instruction::FMul && BinaryOperator::isFNeg(BO))) {
564  DEBUG(dbgs() << "MORPH LEAF: " << *Op << " (" << Weight << ") TO ");
565  BO = LowerNegateToMultiply(BO);
566  DEBUG(dbgs() << *BO << '\n');
567  Worklist.push_back(std::make_pair(BO, Weight));
568  Changed = true;
569  continue;
570  }
571 
572  // Failed to morph into an expression of the right type. This really is
573  // a leaf.
574  DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n");
575  assert(!isReassociableOp(Op, Opcode) && "Value was morphed?");
576  LeafOrder.push_back(Op);
577  Leaves[Op] = Weight;
578  }
579  }
580 
581  // The leaves, repeated according to their weights, represent the linearized
582  // form of the expression.
583  for (unsigned i = 0, e = LeafOrder.size(); i != e; ++i) {
584  Value *V = LeafOrder[i];
585  LeafMap::iterator It = Leaves.find(V);
586  if (It == Leaves.end())
587  // Node initially thought to be a leaf wasn't.
588  continue;
589  assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!");
590  APInt Weight = It->second;
591  if (Weight.isMinValue())
592  // Leaf already output or weight reduction eliminated it.
593  continue;
594  // Ensure the leaf is only output once.
595  It->second = 0;
596  Ops.push_back(std::make_pair(V, Weight));
597  }
598 
599  // For nilpotent operations or addition there may be no operands, for example
600  // because the expression was "X xor X" or consisted of 2^Bitwidth additions:
601  // in both cases the weight reduces to 0 causing the value to be skipped.
602  if (Ops.empty()) {
603  Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
604  assert(Identity && "Associative operation without identity!");
605  Ops.emplace_back(Identity, APInt(Bitwidth, 1));
606  }
607 
608  return Changed;
609 }
610 
611 /// Now that the operands for this expression tree are
612 /// linearized and optimized, emit them in-order.
613 void ReassociatePass::RewriteExprTree(BinaryOperator *I,
615  assert(Ops.size() > 1 && "Single values should be used directly!");
616 
617  // Since our optimizations should never increase the number of operations, the
618  // new expression can usually be written reusing the existing binary operators
619  // from the original expression tree, without creating any new instructions,
620  // though the rewritten expression may have a completely different topology.
621  // We take care to not change anything if the new expression will be the same
622  // as the original. If more than trivial changes (like commuting operands)
623  // were made then we are obliged to clear out any optional subclass data like
624  // nsw flags.
625 
626  /// NodesToRewrite - Nodes from the original expression available for writing
627  /// the new expression into.
628  SmallVector<BinaryOperator*, 8> NodesToRewrite;
629  unsigned Opcode = I->getOpcode();
630  BinaryOperator *Op = I;
631 
632  /// NotRewritable - The operands being written will be the leaves of the new
633  /// expression and must not be used as inner nodes (via NodesToRewrite) by
634  /// mistake. Inner nodes are always reassociable, and usually leaves are not
635  /// (if they were they would have been incorporated into the expression and so
636  /// would not be leaves), so most of the time there is no danger of this. But
637  /// in rare cases a leaf may become reassociable if an optimization kills uses
638  /// of it, or it may momentarily become reassociable during rewriting (below)
639  /// due it being removed as an operand of one of its uses. Ensure that misuse
640  /// of leaf nodes as inner nodes cannot occur by remembering all of the future
641  /// leaves and refusing to reuse any of them as inner nodes.
642  SmallPtrSet<Value*, 8> NotRewritable;
643  for (unsigned i = 0, e = Ops.size(); i != e; ++i)
644  NotRewritable.insert(Ops[i].Op);
645 
646  // ExpressionChanged - Non-null if the rewritten expression differs from the
647  // original in some non-trivial way, requiring the clearing of optional flags.
648  // Flags are cleared from the operator in ExpressionChanged up to I inclusive.
649  BinaryOperator *ExpressionChanged = nullptr;
650  for (unsigned i = 0; ; ++i) {
651  // The last operation (which comes earliest in the IR) is special as both
652  // operands will come from Ops, rather than just one with the other being
653  // a subexpression.
654  if (i+2 == Ops.size()) {
655  Value *NewLHS = Ops[i].Op;
656  Value *NewRHS = Ops[i+1].Op;
657  Value *OldLHS = Op->getOperand(0);
658  Value *OldRHS = Op->getOperand(1);
659 
660  if (NewLHS == OldLHS && NewRHS == OldRHS)
661  // Nothing changed, leave it alone.
662  break;
663 
664  if (NewLHS == OldRHS && NewRHS == OldLHS) {
665  // The order of the operands was reversed. Swap them.
666  DEBUG(dbgs() << "RA: " << *Op << '\n');
667  Op->swapOperands();
668  DEBUG(dbgs() << "TO: " << *Op << '\n');
669  MadeChange = true;
670  ++NumChanged;
671  break;
672  }
673 
674  // The new operation differs non-trivially from the original. Overwrite
675  // the old operands with the new ones.
676  DEBUG(dbgs() << "RA: " << *Op << '\n');
677  if (NewLHS != OldLHS) {
678  BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
679  if (BO && !NotRewritable.count(BO))
680  NodesToRewrite.push_back(BO);
681  Op->setOperand(0, NewLHS);
682  }
683  if (NewRHS != OldRHS) {
684  BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
685  if (BO && !NotRewritable.count(BO))
686  NodesToRewrite.push_back(BO);
687  Op->setOperand(1, NewRHS);
688  }
689  DEBUG(dbgs() << "TO: " << *Op << '\n');
690 
691  ExpressionChanged = Op;
692  MadeChange = true;
693  ++NumChanged;
694 
695  break;
696  }
697 
698  // Not the last operation. The left-hand side will be a sub-expression
699  // while the right-hand side will be the current element of Ops.
700  Value *NewRHS = Ops[i].Op;
701  if (NewRHS != Op->getOperand(1)) {
702  DEBUG(dbgs() << "RA: " << *Op << '\n');
703  if (NewRHS == Op->getOperand(0)) {
704  // The new right-hand side was already present as the left operand. If
705  // we are lucky then swapping the operands will sort out both of them.
706  Op->swapOperands();
707  } else {
708  // Overwrite with the new right-hand side.
709  BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
710  if (BO && !NotRewritable.count(BO))
711  NodesToRewrite.push_back(BO);
712  Op->setOperand(1, NewRHS);
713  ExpressionChanged = Op;
714  }
715  DEBUG(dbgs() << "TO: " << *Op << '\n');
716  MadeChange = true;
717  ++NumChanged;
718  }
719 
720  // Now deal with the left-hand side. If this is already an operation node
721  // from the original expression then just rewrite the rest of the expression
722  // into it.
723  BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode);
724  if (BO && !NotRewritable.count(BO)) {
725  Op = BO;
726  continue;
727  }
728 
729  // Otherwise, grab a spare node from the original expression and use that as
730  // the left-hand side. If there are no nodes left then the optimizers made
731  // an expression with more nodes than the original! This usually means that
732  // they did something stupid but it might mean that the problem was just too
733  // hard (finding the mimimal number of multiplications needed to realize a
734  // multiplication expression is NP-complete). Whatever the reason, smart or
735  // stupid, create a new node if there are none left.
736  BinaryOperator *NewOp;
737  if (NodesToRewrite.empty()) {
740  Undef, Undef, "", I);
741  if (NewOp->getType()->isFPOrFPVectorTy())
742  NewOp->setFastMathFlags(I->getFastMathFlags());
743  } else {
744  NewOp = NodesToRewrite.pop_back_val();
745  }
746 
747  DEBUG(dbgs() << "RA: " << *Op << '\n');
748  Op->setOperand(0, NewOp);
749  DEBUG(dbgs() << "TO: " << *Op << '\n');
750  ExpressionChanged = Op;
751  MadeChange = true;
752  ++NumChanged;
753  Op = NewOp;
754  }
755 
756  // If the expression changed non-trivially then clear out all subclass data
757  // starting from the operator specified in ExpressionChanged, and compactify
758  // the operators to just before the expression root to guarantee that the
759  // expression tree is dominated by all of Ops.
760  if (ExpressionChanged)
761  do {
762  // Preserve FastMathFlags.
763  if (isa<FPMathOperator>(I)) {
765  ExpressionChanged->clearSubclassOptionalData();
766  ExpressionChanged->setFastMathFlags(Flags);
767  } else
768  ExpressionChanged->clearSubclassOptionalData();
769 
770  if (ExpressionChanged == I)
771  break;
772  ExpressionChanged->moveBefore(I);
773  ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->user_begin());
774  } while (1);
775 
776  // Throw away any left over nodes from the original expression.
777  for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)
778  RedoInsts.insert(NodesToRewrite[i]);
779 }
780 
781 /// Insert instructions before the instruction pointed to by BI,
782 /// that computes the negative version of the value specified. The negative
783 /// version of the value is returned, and BI is left pointing at the instruction
784 /// that should be processed next by the reassociation pass.
785 /// Also add intermediate instructions to the redo list that are modified while
786 /// pushing the negates through adds. These will be revisited to see if
787 /// additional opportunities have been exposed.
790  if (Constant *C = dyn_cast<Constant>(V)) {
791  if (C->getType()->isFPOrFPVectorTy()) {
792  return ConstantExpr::getFNeg(C);
793  }
794  return ConstantExpr::getNeg(C);
795  }
796 
797 
798  // We are trying to expose opportunity for reassociation. One of the things
799  // that we want to do to achieve this is to push a negation as deep into an
800  // expression chain as possible, to expose the add instructions. In practice,
801  // this means that we turn this:
802  // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
803  // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
804  // the constants. We assume that instcombine will clean up the mess later if
805  // we introduce tons of unnecessary negation instructions.
806  //
807  if (BinaryOperator *I =
808  isReassociableOp(V, Instruction::Add, Instruction::FAdd)) {
809  // Push the negates through the add.
810  I->setOperand(0, NegateValue(I->getOperand(0), BI, ToRedo));
811  I->setOperand(1, NegateValue(I->getOperand(1), BI, ToRedo));
812  if (I->getOpcode() == Instruction::Add) {
813  I->setHasNoUnsignedWrap(false);
814  I->setHasNoSignedWrap(false);
815  }
816 
817  // We must move the add instruction here, because the neg instructions do
818  // not dominate the old add instruction in general. By moving it, we are
819  // assured that the neg instructions we just inserted dominate the
820  // instruction we are about to insert after them.
821  //
822  I->moveBefore(BI);
823  I->setName(I->getName()+".neg");
824 
825  // Add the intermediate negates to the redo list as processing them later
826  // could expose more reassociating opportunities.
827  ToRedo.insert(I);
828  return I;
829  }
830 
831  // Okay, we need to materialize a negated version of V with an instruction.
832  // Scan the use lists of V to see if we have one already.
833  for (User *U : V->users()) {
835  continue;
836 
837  // We found one! Now we have to make sure that the definition dominates
838  // this use. We do this by moving it to the entry block (if it is a
839  // non-instruction value) or right after the definition. These negates will
840  // be zapped by reassociate later, so we don't need much finesse here.
841  BinaryOperator *TheNeg = cast<BinaryOperator>(U);
842 
843  // Verify that the negate is in this function, V might be a constant expr.
844  if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
845  continue;
846 
847  BasicBlock::iterator InsertPt;
848  if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
849  if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
850  InsertPt = II->getNormalDest()->begin();
851  } else {
852  InsertPt = ++InstInput->getIterator();
853  }
854  while (isa<PHINode>(InsertPt)) ++InsertPt;
855  } else {
856  InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
857  }
858  TheNeg->moveBefore(&*InsertPt);
859  if (TheNeg->getOpcode() == Instruction::Sub) {
860  TheNeg->setHasNoUnsignedWrap(false);
861  TheNeg->setHasNoSignedWrap(false);
862  } else {
863  TheNeg->andIRFlags(BI);
864  }
865  ToRedo.insert(TheNeg);
866  return TheNeg;
867  }
868 
869  // Insert a 'neg' instruction that subtracts the value from zero to get the
870  // negation.
871  BinaryOperator *NewNeg = CreateNeg(V, V->getName() + ".neg", BI, BI);
872  ToRedo.insert(NewNeg);
873  return NewNeg;
874 }
875 
876 /// Return true if we should break up this subtract of X-Y into (X + -Y).
878  // If this is a negation, we can't split it up!
880  return false;
881 
882  // Don't breakup X - undef.
883  if (isa<UndefValue>(Sub->getOperand(1)))
884  return false;
885 
886  // Don't bother to break this up unless either the LHS is an associable add or
887  // subtract or if this is only used by one.
888  Value *V0 = Sub->getOperand(0);
889  if (isReassociableOp(V0, Instruction::Add, Instruction::FAdd) ||
890  isReassociableOp(V0, Instruction::Sub, Instruction::FSub))
891  return true;
892  Value *V1 = Sub->getOperand(1);
893  if (isReassociableOp(V1, Instruction::Add, Instruction::FAdd) ||
894  isReassociableOp(V1, Instruction::Sub, Instruction::FSub))
895  return true;
896  Value *VB = Sub->user_back();
897  if (Sub->hasOneUse() &&
898  (isReassociableOp(VB, Instruction::Add, Instruction::FAdd) ||
899  isReassociableOp(VB, Instruction::Sub, Instruction::FSub)))
900  return true;
901 
902  return false;
903 }
904 
905 /// If we have (X-Y), and if either X is an add, or if this is only used by an
906 /// add, transform this into (X+(0-Y)) to promote better reassociation.
907 static BinaryOperator *
909  // Convert a subtract into an add and a neg instruction. This allows sub
910  // instructions to be commuted with other add instructions.
911  //
912  // Calculate the negative value of Operand 1 of the sub instruction,
913  // and set it as the RHS of the add instruction we just made.
914  //
915  Value *NegVal = NegateValue(Sub->getOperand(1), Sub, ToRedo);
916  BinaryOperator *New = CreateAdd(Sub->getOperand(0), NegVal, "", Sub, Sub);
917  Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op.
918  Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op.
919  New->takeName(Sub);
920 
921  // Everyone now refers to the add instruction.
922  Sub->replaceAllUsesWith(New);
923  New->setDebugLoc(Sub->getDebugLoc());
924 
925  DEBUG(dbgs() << "Negated: " << *New << '\n');
926  return New;
927 }
928 
929 /// If this is a shift of a reassociable multiply or is used by one, change
930 /// this into a multiply by a constant to assist with further reassociation.
932  Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
933  MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
934 
935  BinaryOperator *Mul =
936  BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
937  Shl->setOperand(0, UndefValue::get(Shl->getType())); // Drop use of op.
938  Mul->takeName(Shl);
939 
940  // Everyone now refers to the mul instruction.
941  Shl->replaceAllUsesWith(Mul);
942  Mul->setDebugLoc(Shl->getDebugLoc());
943 
944  // We can safely preserve the nuw flag in all cases. It's also safe to turn a
945  // nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special
946  // handling.
947  bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap();
948  bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap();
949  if (NSW && NUW)
950  Mul->setHasNoSignedWrap(true);
951  Mul->setHasNoUnsignedWrap(NUW);
952  return Mul;
953 }
954 
955 /// Scan backwards and forwards among values with the same rank as element i
956 /// to see if X exists. If X does not exist, return i. This is useful when
957 /// scanning for 'x' when we see '-x' because they both get the same rank.
958 static unsigned FindInOperandList(SmallVectorImpl<ValueEntry> &Ops, unsigned i,
959  Value *X) {
960  unsigned XRank = Ops[i].Rank;
961  unsigned e = Ops.size();
962  for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
963  if (Ops[j].Op == X)
964  return j;
965  if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
966  if (Instruction *I2 = dyn_cast<Instruction>(X))
967  if (I1->isIdenticalTo(I2))
968  return j;
969  }
970  // Scan backwards.
971  for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
972  if (Ops[j].Op == X)
973  return j;
974  if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
975  if (Instruction *I2 = dyn_cast<Instruction>(X))
976  if (I1->isIdenticalTo(I2))
977  return j;
978  }
979  return i;
980 }
981 
982 /// Emit a tree of add instructions, summing Ops together
983 /// and returning the result. Insert the tree before I.
986  if (Ops.size() == 1) return Ops.back();
987 
988  Value *V1 = Ops.back();
989  Ops.pop_back();
990  Value *V2 = EmitAddTreeOfValues(I, Ops);
991  return CreateAdd(V2, V1, "tmp", I, I);
992 }
993 
994 /// If V is an expression tree that is a multiplication sequence,
995 /// and if this sequence contains a multiply by Factor,
996 /// remove Factor from the tree and return the new tree.
997 Value *ReassociatePass::RemoveFactorFromExpression(Value *V, Value *Factor) {
998  BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
999  if (!BO)
1000  return nullptr;
1001 
1003  MadeChange |= LinearizeExprTree(BO, Tree);
1005  Factors.reserve(Tree.size());
1006  for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
1007  RepeatedValue E = Tree[i];
1008  Factors.append(E.second.getZExtValue(),
1009  ValueEntry(getRank(E.first), E.first));
1010  }
1011 
1012  bool FoundFactor = false;
1013  bool NeedsNegate = false;
1014  for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1015  if (Factors[i].Op == Factor) {
1016  FoundFactor = true;
1017  Factors.erase(Factors.begin()+i);
1018  break;
1019  }
1020 
1021  // If this is a negative version of this factor, remove it.
1022  if (ConstantInt *FC1 = dyn_cast<ConstantInt>(Factor)) {
1023  if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op))
1024  if (FC1->getValue() == -FC2->getValue()) {
1025  FoundFactor = NeedsNegate = true;
1026  Factors.erase(Factors.begin()+i);
1027  break;
1028  }
1029  } else if (ConstantFP *FC1 = dyn_cast<ConstantFP>(Factor)) {
1030  if (ConstantFP *FC2 = dyn_cast<ConstantFP>(Factors[i].Op)) {
1031  const APFloat &F1 = FC1->getValueAPF();
1032  APFloat F2(FC2->getValueAPF());
1033  F2.changeSign();
1034  if (F1.compare(F2) == APFloat::cmpEqual) {
1035  FoundFactor = NeedsNegate = true;
1036  Factors.erase(Factors.begin() + i);
1037  break;
1038  }
1039  }
1040  }
1041  }
1042 
1043  if (!FoundFactor) {
1044  // Make sure to restore the operands to the expression tree.
1045  RewriteExprTree(BO, Factors);
1046  return nullptr;
1047  }
1048 
1049  BasicBlock::iterator InsertPt = ++BO->getIterator();
1050 
1051  // If this was just a single multiply, remove the multiply and return the only
1052  // remaining operand.
1053  if (Factors.size() == 1) {
1054  RedoInsts.insert(BO);
1055  V = Factors[0].Op;
1056  } else {
1057  RewriteExprTree(BO, Factors);
1058  V = BO;
1059  }
1060 
1061  if (NeedsNegate)
1062  V = CreateNeg(V, "neg", &*InsertPt, BO);
1063 
1064  return V;
1065 }
1066 
1067 /// If V is a single-use multiply, recursively add its operands as factors,
1068 /// otherwise add V to the list of factors.
1069 ///
1070 /// Ops is the top-level list of add operands we're trying to factor.
1072  SmallVectorImpl<Value*> &Factors,
1073  const SmallVectorImpl<ValueEntry> &Ops) {
1074  BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
1075  if (!BO) {
1076  Factors.push_back(V);
1077  return;
1078  }
1079 
1080  // Otherwise, add the LHS and RHS to the list of factors.
1081  FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops);
1082  FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops);
1083 }
1084 
1085 /// Optimize a series of operands to an 'and', 'or', or 'xor' instruction.
1086 /// This optimizes based on identities. If it can be reduced to a single Value,
1087 /// it is returned, otherwise the Ops list is mutated as necessary.
1088 static Value *OptimizeAndOrXor(unsigned Opcode,
1090  // Scan the operand lists looking for X and ~X pairs, along with X,X pairs.
1091  // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1.
1092  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1093  // First, check for X and ~X in the operand list.
1094  assert(i < Ops.size());
1095  if (BinaryOperator::isNot(Ops[i].Op)) { // Cannot occur for ^.
1096  Value *X = BinaryOperator::getNotArgument(Ops[i].Op);
1097  unsigned FoundX = FindInOperandList(Ops, i, X);
1098  if (FoundX != i) {
1099  if (Opcode == Instruction::And) // ...&X&~X = 0
1100  return Constant::getNullValue(X->getType());
1101 
1102  if (Opcode == Instruction::Or) // ...|X|~X = -1
1103  return Constant::getAllOnesValue(X->getType());
1104  }
1105  }
1106 
1107  // Next, check for duplicate pairs of values, which we assume are next to
1108  // each other, due to our sorting criteria.
1109  assert(i < Ops.size());
1110  if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) {
1111  if (Opcode == Instruction::And || Opcode == Instruction::Or) {
1112  // Drop duplicate values for And and Or.
1113  Ops.erase(Ops.begin()+i);
1114  --i; --e;
1115  ++NumAnnihil;
1116  continue;
1117  }
1118 
1119  // Drop pairs of values for Xor.
1120  assert(Opcode == Instruction::Xor);
1121  if (e == 2)
1122  return Constant::getNullValue(Ops[0].Op->getType());
1123 
1124  // Y ^ X^X -> Y
1125  Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
1126  i -= 1; e -= 2;
1127  ++NumAnnihil;
1128  }
1129  }
1130  return nullptr;
1131 }
1132 
1133 /// Helper function of CombineXorOpnd(). It creates a bitwise-and
1134 /// instruction with the given two operands, and return the resulting
1135 /// instruction. There are two special cases: 1) if the constant operand is 0,
1136 /// it will return NULL. 2) if the constant is ~0, the symbolic operand will
1137 /// be returned.
1138 static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd,
1139  const APInt &ConstOpnd) {
1140  if (ConstOpnd != 0) {
1141  if (!ConstOpnd.isAllOnesValue()) {
1142  LLVMContext &Ctx = Opnd->getType()->getContext();
1143  Instruction *I;
1144  I = BinaryOperator::CreateAnd(Opnd, ConstantInt::get(Ctx, ConstOpnd),
1145  "and.ra", InsertBefore);
1146  I->setDebugLoc(InsertBefore->getDebugLoc());
1147  return I;
1148  }
1149  return Opnd;
1150  }
1151  return nullptr;
1152 }
1153 
1154 // Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
1155 // into "R ^ C", where C would be 0, and R is a symbolic value.
1156 //
1157 // If it was successful, true is returned, and the "R" and "C" is returned
1158 // via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
1159 // and both "Res" and "ConstOpnd" remain unchanged.
1160 //
1161 bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
1162  APInt &ConstOpnd, Value *&Res) {
1163  // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
1164  // = ((x | c1) ^ c1) ^ (c1 ^ c2)
1165  // = (x & ~c1) ^ (c1 ^ c2)
1166  // It is useful only when c1 == c2.
1167  if (Opnd1->isOrExpr() && Opnd1->getConstPart() != 0) {
1168  if (!Opnd1->getValue()->hasOneUse())
1169  return false;
1170 
1171  const APInt &C1 = Opnd1->getConstPart();
1172  if (C1 != ConstOpnd)
1173  return false;
1174 
1175  Value *X = Opnd1->getSymbolicPart();
1176  Res = createAndInstr(I, X, ~C1);
1177  // ConstOpnd was C2, now C1 ^ C2.
1178  ConstOpnd ^= C1;
1179 
1180  if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1181  RedoInsts.insert(T);
1182  return true;
1183  }
1184  return false;
1185 }
1186 
1187 
1188 // Helper function of OptimizeXor(). It tries to simplify
1189 // "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
1190 // symbolic value.
1191 //
1192 // If it was successful, true is returned, and the "R" and "C" is returned
1193 // via "Res" and "ConstOpnd", respectively (If the entire expression is
1194 // evaluated to a constant, the Res is set to NULL); otherwise, false is
1195 // returned, and both "Res" and "ConstOpnd" remain unchanged.
1196 bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
1197  XorOpnd *Opnd2, APInt &ConstOpnd,
1198  Value *&Res) {
1199  Value *X = Opnd1->getSymbolicPart();
1200  if (X != Opnd2->getSymbolicPart())
1201  return false;
1202 
1203  // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
1204  int DeadInstNum = 1;
1205  if (Opnd1->getValue()->hasOneUse())
1206  DeadInstNum++;
1207  if (Opnd2->getValue()->hasOneUse())
1208  DeadInstNum++;
1209 
1210  // Xor-Rule 2:
1211  // (x | c1) ^ (x & c2)
1212  // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
1213  // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
1214  // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
1215  //
1216  if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
1217  if (Opnd2->isOrExpr())
1218  std::swap(Opnd1, Opnd2);
1219 
1220  const APInt &C1 = Opnd1->getConstPart();
1221  const APInt &C2 = Opnd2->getConstPart();
1222  APInt C3((~C1) ^ C2);
1223 
1224  // Do not increase code size!
1225  if (C3 != 0 && !C3.isAllOnesValue()) {
1226  int NewInstNum = ConstOpnd != 0 ? 1 : 2;
1227  if (NewInstNum > DeadInstNum)
1228  return false;
1229  }
1230 
1231  Res = createAndInstr(I, X, C3);
1232  ConstOpnd ^= C1;
1233 
1234  } else if (Opnd1->isOrExpr()) {
1235  // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
1236  //
1237  const APInt &C1 = Opnd1->getConstPart();
1238  const APInt &C2 = Opnd2->getConstPart();
1239  APInt C3 = C1 ^ C2;
1240 
1241  // Do not increase code size
1242  if (C3 != 0 && !C3.isAllOnesValue()) {
1243  int NewInstNum = ConstOpnd != 0 ? 1 : 2;
1244  if (NewInstNum > DeadInstNum)
1245  return false;
1246  }
1247 
1248  Res = createAndInstr(I, X, C3);
1249  ConstOpnd ^= C3;
1250  } else {
1251  // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
1252  //
1253  const APInt &C1 = Opnd1->getConstPart();
1254  const APInt &C2 = Opnd2->getConstPart();
1255  APInt C3 = C1 ^ C2;
1256  Res = createAndInstr(I, X, C3);
1257  }
1258 
1259  // Put the original operands in the Redo list; hope they will be deleted
1260  // as dead code.
1261  if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
1262  RedoInsts.insert(T);
1263  if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
1264  RedoInsts.insert(T);
1265 
1266  return true;
1267 }
1268 
1269 /// Optimize a series of operands to an 'xor' instruction. If it can be reduced
1270 /// to a single Value, it is returned, otherwise the Ops list is mutated as
1271 /// necessary.
1272 Value *ReassociatePass::OptimizeXor(Instruction *I,
1274  if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
1275  return V;
1276 
1277  if (Ops.size() == 1)
1278  return nullptr;
1279 
1281  SmallVector<XorOpnd*, 8> OpndPtrs;
1282  Type *Ty = Ops[0].Op->getType();
1283  APInt ConstOpnd(Ty->getIntegerBitWidth(), 0);
1284 
1285  // Step 1: Convert ValueEntry to XorOpnd
1286  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1287  Value *V = Ops[i].Op;
1288  if (!isa<ConstantInt>(V)) {
1289  XorOpnd O(V);
1290  O.setSymbolicRank(getRank(O.getSymbolicPart()));
1291  Opnds.push_back(O);
1292  } else
1293  ConstOpnd ^= cast<ConstantInt>(V)->getValue();
1294  }
1295 
1296  // NOTE: From this point on, do *NOT* add/delete element to/from "Opnds".
1297  // It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate
1298  // the "OpndPtrs" as well. For the similar reason, do not fuse this loop
1299  // with the previous loop --- the iterator of the "Opnds" may be invalidated
1300  // when new elements are added to the vector.
1301  for (unsigned i = 0, e = Opnds.size(); i != e; ++i)
1302  OpndPtrs.push_back(&Opnds[i]);
1303 
1304  // Step 2: Sort the Xor-Operands in a way such that the operands containing
1305  // the same symbolic value cluster together. For instance, the input operand
1306  // sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
1307  // ("x | 123", "x & 789", "y & 456").
1308  //
1309  // The purpose is twofold:
1310  // 1) Cluster together the operands sharing the same symbolic-value.
1311  // 2) Operand having smaller symbolic-value-rank is permuted earlier, which
1312  // could potentially shorten crital path, and expose more loop-invariants.
1313  // Note that values' rank are basically defined in RPO order (FIXME).
1314  // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
1315  // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
1316  // "z" in the order of X-Y-Z is better than any other orders.
1317  std::stable_sort(OpndPtrs.begin(), OpndPtrs.end(),
1318  [](XorOpnd *LHS, XorOpnd *RHS) {
1319  return LHS->getSymbolicRank() < RHS->getSymbolicRank();
1320  });
1321 
1322  // Step 3: Combine adjacent operands
1323  XorOpnd *PrevOpnd = nullptr;
1324  bool Changed = false;
1325  for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
1326  XorOpnd *CurrOpnd = OpndPtrs[i];
1327  // The combined value
1328  Value *CV;
1329 
1330  // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
1331  if (ConstOpnd != 0 && CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
1332  Changed = true;
1333  if (CV)
1334  *CurrOpnd = XorOpnd(CV);
1335  else {
1336  CurrOpnd->Invalidate();
1337  continue;
1338  }
1339  }
1340 
1341  if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
1342  PrevOpnd = CurrOpnd;
1343  continue;
1344  }
1345 
1346  // step 3.2: When previous and current operands share the same symbolic
1347  // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
1348  //
1349  if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
1350  // Remove previous operand
1351  PrevOpnd->Invalidate();
1352  if (CV) {
1353  *CurrOpnd = XorOpnd(CV);
1354  PrevOpnd = CurrOpnd;
1355  } else {
1356  CurrOpnd->Invalidate();
1357  PrevOpnd = nullptr;
1358  }
1359  Changed = true;
1360  }
1361  }
1362 
1363  // Step 4: Reassemble the Ops
1364  if (Changed) {
1365  Ops.clear();
1366  for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
1367  XorOpnd &O = Opnds[i];
1368  if (O.isInvalid())
1369  continue;
1370  ValueEntry VE(getRank(O.getValue()), O.getValue());
1371  Ops.push_back(VE);
1372  }
1373  if (ConstOpnd != 0) {
1374  Value *C = ConstantInt::get(Ty->getContext(), ConstOpnd);
1375  ValueEntry VE(getRank(C), C);
1376  Ops.push_back(VE);
1377  }
1378  int Sz = Ops.size();
1379  if (Sz == 1)
1380  return Ops.back().Op;
1381  else if (Sz == 0) {
1382  assert(ConstOpnd == 0);
1383  return ConstantInt::get(Ty->getContext(), ConstOpnd);
1384  }
1385  }
1386 
1387  return nullptr;
1388 }
1389 
1390 /// Optimize a series of operands to an 'add' instruction. This
1391 /// optimizes based on identities. If it can be reduced to a single Value, it
1392 /// is returned, otherwise the Ops list is mutated as necessary.
1393 Value *ReassociatePass::OptimizeAdd(Instruction *I,
1395  // Scan the operand lists looking for X and -X pairs. If we find any, we
1396  // can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it,
1397  // scan for any
1398  // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
1399 
1400  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1401  Value *TheOp = Ops[i].Op;
1402  // Check to see if we've seen this operand before. If so, we factor all
1403  // instances of the operand together. Due to our sorting criteria, we know
1404  // that these need to be next to each other in the vector.
1405  if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) {
1406  // Rescan the list, remove all instances of this operand from the expr.
1407  unsigned NumFound = 0;
1408  do {
1409  Ops.erase(Ops.begin()+i);
1410  ++NumFound;
1411  } while (i != Ops.size() && Ops[i].Op == TheOp);
1412 
1413  DEBUG(dbgs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n');
1414  ++NumFactor;
1415 
1416  // Insert a new multiply.
1417  Type *Ty = TheOp->getType();
1418  Constant *C = Ty->isIntOrIntVectorTy() ?
1419  ConstantInt::get(Ty, NumFound) : ConstantFP::get(Ty, NumFound);
1420  Instruction *Mul = CreateMul(TheOp, C, "factor", I, I);
1421 
1422  // Now that we have inserted a multiply, optimize it. This allows us to
1423  // handle cases that require multiple factoring steps, such as this:
1424  // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6
1425  RedoInsts.insert(Mul);
1426 
1427  // If every add operand was a duplicate, return the multiply.
1428  if (Ops.empty())
1429  return Mul;
1430 
1431  // Otherwise, we had some input that didn't have the dupe, such as
1432  // "A + A + B" -> "A*2 + B". Add the new multiply to the list of
1433  // things being added by this operation.
1434  Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul));
1435 
1436  --i;
1437  e = Ops.size();
1438  continue;
1439  }
1440 
1441  // Check for X and -X or X and ~X in the operand list.
1442  if (!BinaryOperator::isNeg(TheOp) && !BinaryOperator::isFNeg(TheOp) &&
1443  !BinaryOperator::isNot(TheOp))
1444  continue;
1445 
1446  Value *X = nullptr;
1447  if (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp))
1448  X = BinaryOperator::getNegArgument(TheOp);
1449  else if (BinaryOperator::isNot(TheOp))
1450  X = BinaryOperator::getNotArgument(TheOp);
1451 
1452  unsigned FoundX = FindInOperandList(Ops, i, X);
1453  if (FoundX == i)
1454  continue;
1455 
1456  // Remove X and -X from the operand list.
1457  if (Ops.size() == 2 &&
1458  (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp)))
1459  return Constant::getNullValue(X->getType());
1460 
1461  // Remove X and ~X from the operand list.
1462  if (Ops.size() == 2 && BinaryOperator::isNot(TheOp))
1463  return Constant::getAllOnesValue(X->getType());
1464 
1465  Ops.erase(Ops.begin()+i);
1466  if (i < FoundX)
1467  --FoundX;
1468  else
1469  --i; // Need to back up an extra one.
1470  Ops.erase(Ops.begin()+FoundX);
1471  ++NumAnnihil;
1472  --i; // Revisit element.
1473  e -= 2; // Removed two elements.
1474 
1475  // if X and ~X we append -1 to the operand list.
1476  if (BinaryOperator::isNot(TheOp)) {
1478  Ops.insert(Ops.end(), ValueEntry(getRank(V), V));
1479  e += 1;
1480  }
1481  }
1482 
1483  // Scan the operand list, checking to see if there are any common factors
1484  // between operands. Consider something like A*A+A*B*C+D. We would like to
1485  // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies.
1486  // To efficiently find this, we count the number of times a factor occurs
1487  // for any ADD operands that are MULs.
1488  DenseMap<Value*, unsigned> FactorOccurrences;
1489 
1490  // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4)
1491  // where they are actually the same multiply.
1492  unsigned MaxOcc = 0;
1493  Value *MaxOccVal = nullptr;
1494  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1495  BinaryOperator *BOp =
1496  isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1497  if (!BOp)
1498  continue;
1499 
1500  // Compute all of the factors of this added value.
1501  SmallVector<Value*, 8> Factors;
1502  FindSingleUseMultiplyFactors(BOp, Factors, Ops);
1503  assert(Factors.size() > 1 && "Bad linearize!");
1504 
1505  // Add one to FactorOccurrences for each unique factor in this op.
1506  SmallPtrSet<Value*, 8> Duplicates;
1507  for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
1508  Value *Factor = Factors[i];
1509  if (!Duplicates.insert(Factor).second)
1510  continue;
1511 
1512  unsigned Occ = ++FactorOccurrences[Factor];
1513  if (Occ > MaxOcc) {
1514  MaxOcc = Occ;
1515  MaxOccVal = Factor;
1516  }
1517 
1518  // If Factor is a negative constant, add the negated value as a factor
1519  // because we can percolate the negate out. Watch for minint, which
1520  // cannot be positivified.
1521  if (ConstantInt *CI = dyn_cast<ConstantInt>(Factor)) {
1522  if (CI->isNegative() && !CI->isMinValue(true)) {
1523  Factor = ConstantInt::get(CI->getContext(), -CI->getValue());
1524  if (!Duplicates.insert(Factor).second)
1525  continue;
1526  unsigned Occ = ++FactorOccurrences[Factor];
1527  if (Occ > MaxOcc) {
1528  MaxOcc = Occ;
1529  MaxOccVal = Factor;
1530  }
1531  }
1532  } else if (ConstantFP *CF = dyn_cast<ConstantFP>(Factor)) {
1533  if (CF->isNegative()) {
1534  APFloat F(CF->getValueAPF());
1535  F.changeSign();
1536  Factor = ConstantFP::get(CF->getContext(), F);
1537  if (!Duplicates.insert(Factor).second)
1538  continue;
1539  unsigned Occ = ++FactorOccurrences[Factor];
1540  if (Occ > MaxOcc) {
1541  MaxOcc = Occ;
1542  MaxOccVal = Factor;
1543  }
1544  }
1545  }
1546  }
1547  }
1548 
1549  // If any factor occurred more than one time, we can pull it out.
1550  if (MaxOcc > 1) {
1551  DEBUG(dbgs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
1552  ++NumFactor;
1553 
1554  // Create a new instruction that uses the MaxOccVal twice. If we don't do
1555  // this, we could otherwise run into situations where removing a factor
1556  // from an expression will drop a use of maxocc, and this can cause
1557  // RemoveFactorFromExpression on successive values to behave differently.
1558  Instruction *DummyInst =
1559  I->getType()->isIntOrIntVectorTy()
1560  ? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal)
1561  : BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal);
1562 
1563  SmallVector<WeakVH, 4> NewMulOps;
1564  for (unsigned i = 0; i != Ops.size(); ++i) {
1565  // Only try to remove factors from expressions we're allowed to.
1566  BinaryOperator *BOp =
1567  isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
1568  if (!BOp)
1569  continue;
1570 
1571  if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
1572  // The factorized operand may occur several times. Convert them all in
1573  // one fell swoop.
1574  for (unsigned j = Ops.size(); j != i;) {
1575  --j;
1576  if (Ops[j].Op == Ops[i].Op) {
1577  NewMulOps.push_back(V);
1578  Ops.erase(Ops.begin()+j);
1579  }
1580  }
1581  --i;
1582  }
1583  }
1584 
1585  // No need for extra uses anymore.
1586  delete DummyInst;
1587 
1588  unsigned NumAddedValues = NewMulOps.size();
1589  Value *V = EmitAddTreeOfValues(I, NewMulOps);
1590 
1591  // Now that we have inserted the add tree, optimize it. This allows us to
1592  // handle cases that require multiple factoring steps, such as this:
1593  // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
1594  assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
1595  (void)NumAddedValues;
1596  if (Instruction *VI = dyn_cast<Instruction>(V))
1597  RedoInsts.insert(VI);
1598 
1599  // Create the multiply.
1600  Instruction *V2 = CreateMul(V, MaxOccVal, "tmp", I, I);
1601 
1602  // Rerun associate on the multiply in case the inner expression turned into
1603  // a multiply. We want to make sure that we keep things in canonical form.
1604  RedoInsts.insert(V2);
1605 
1606  // If every add operand included the factor (e.g. "A*B + A*C"), then the
1607  // entire result expression is just the multiply "A*(B+C)".
1608  if (Ops.empty())
1609  return V2;
1610 
1611  // Otherwise, we had some input that didn't have the factor, such as
1612  // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
1613  // things being added by this operation.
1614  Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
1615  }
1616 
1617  return nullptr;
1618 }
1619 
1620 /// \brief Build up a vector of value/power pairs factoring a product.
1621 ///
1622 /// Given a series of multiplication operands, build a vector of factors and
1623 /// the powers each is raised to when forming the final product. Sort them in
1624 /// the order of descending power.
1625 ///
1626 /// (x*x) -> [(x, 2)]
1627 /// ((x*x)*x) -> [(x, 3)]
1628 /// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)]
1629 ///
1630 /// \returns Whether any factors have a power greater than one.
1631 bool ReassociatePass::collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
1632  SmallVectorImpl<Factor> &Factors) {
1633  // FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this.
1634  // Compute the sum of powers of simplifiable factors.
1635  unsigned FactorPowerSum = 0;
1636  for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) {
1637  Value *Op = Ops[Idx-1].Op;
1638 
1639  // Count the number of occurrences of this value.
1640  unsigned Count = 1;
1641  for (; Idx < Size && Ops[Idx].Op == Op; ++Idx)
1642  ++Count;
1643  // Track for simplification all factors which occur 2 or more times.
1644  if (Count > 1)
1645  FactorPowerSum += Count;
1646  }
1647 
1648  // We can only simplify factors if the sum of the powers of our simplifiable
1649  // factors is 4 or higher. When that is the case, we will *always* have
1650  // a simplification. This is an important invariant to prevent cyclicly
1651  // trying to simplify already minimal formations.
1652  if (FactorPowerSum < 4)
1653  return false;
1654 
1655  // Now gather the simplifiable factors, removing them from Ops.
1656  FactorPowerSum = 0;
1657  for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) {
1658  Value *Op = Ops[Idx-1].Op;
1659 
1660  // Count the number of occurrences of this value.
1661  unsigned Count = 1;
1662  for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx)
1663  ++Count;
1664  if (Count == 1)
1665  continue;
1666  // Move an even number of occurrences to Factors.
1667  Count &= ~1U;
1668  Idx -= Count;
1669  FactorPowerSum += Count;
1670  Factors.push_back(Factor(Op, Count));
1671  Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count);
1672  }
1673 
1674  // None of the adjustments above should have reduced the sum of factor powers
1675  // below our mininum of '4'.
1676  assert(FactorPowerSum >= 4);
1677 
1678  std::stable_sort(Factors.begin(), Factors.end(),
1679  [](const Factor &LHS, const Factor &RHS) {
1680  return LHS.Power > RHS.Power;
1681  });
1682  return true;
1683 }
1684 
1685 /// \brief Build a tree of multiplies, computing the product of Ops.
1687  SmallVectorImpl<Value*> &Ops) {
1688  if (Ops.size() == 1)
1689  return Ops.back();
1690 
1691  Value *LHS = Ops.pop_back_val();
1692  do {
1693  if (LHS->getType()->isIntOrIntVectorTy())
1694  LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
1695  else
1696  LHS = Builder.CreateFMul(LHS, Ops.pop_back_val());
1697  } while (!Ops.empty());
1698 
1699  return LHS;
1700 }
1701 
1702 /// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
1703 ///
1704 /// Given a vector of values raised to various powers, where no two values are
1705 /// equal and the powers are sorted in decreasing order, compute the minimal
1706 /// DAG of multiplies to compute the final product, and return that product
1707 /// value.
1708 Value *
1709 ReassociatePass::buildMinimalMultiplyDAG(IRBuilder<> &Builder,
1710  SmallVectorImpl<Factor> &Factors) {
1711  assert(Factors[0].Power);
1712  SmallVector<Value *, 4> OuterProduct;
1713  for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size();
1714  Idx < Size && Factors[Idx].Power > 0; ++Idx) {
1715  if (Factors[Idx].Power != Factors[LastIdx].Power) {
1716  LastIdx = Idx;
1717  continue;
1718  }
1719 
1720  // We want to multiply across all the factors with the same power so that
1721  // we can raise them to that power as a single entity. Build a mini tree
1722  // for that.
1723  SmallVector<Value *, 4> InnerProduct;
1724  InnerProduct.push_back(Factors[LastIdx].Base);
1725  do {
1726  InnerProduct.push_back(Factors[Idx].Base);
1727  ++Idx;
1728  } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power);
1729 
1730  // Reset the base value of the first factor to the new expression tree.
1731  // We'll remove all the factors with the same power in a second pass.
1732  Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
1733  if (Instruction *MI = dyn_cast<Instruction>(M))
1734  RedoInsts.insert(MI);
1735 
1736  LastIdx = Idx;
1737  }
1738  // Unique factors with equal powers -- we've folded them into the first one's
1739  // base.
1740  Factors.erase(std::unique(Factors.begin(), Factors.end(),
1741  [](const Factor &LHS, const Factor &RHS) {
1742  return LHS.Power == RHS.Power;
1743  }),
1744  Factors.end());
1745 
1746  // Iteratively collect the base of each factor with an add power into the
1747  // outer product, and halve each power in preparation for squaring the
1748  // expression.
1749  for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
1750  if (Factors[Idx].Power & 1)
1751  OuterProduct.push_back(Factors[Idx].Base);
1752  Factors[Idx].Power >>= 1;
1753  }
1754  if (Factors[0].Power) {
1755  Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors);
1756  OuterProduct.push_back(SquareRoot);
1757  OuterProduct.push_back(SquareRoot);
1758  }
1759  if (OuterProduct.size() == 1)
1760  return OuterProduct.front();
1761 
1762  Value *V = buildMultiplyTree(Builder, OuterProduct);
1763  return V;
1764 }
1765 
1766 Value *ReassociatePass::OptimizeMul(BinaryOperator *I,
1768  // We can only optimize the multiplies when there is a chain of more than
1769  // three, such that a balanced tree might require fewer total multiplies.
1770  if (Ops.size() < 4)
1771  return nullptr;
1772 
1773  // Try to turn linear trees of multiplies without other uses of the
1774  // intermediate stages into minimal multiply DAGs with perfect sub-expression
1775  // re-use.
1776  SmallVector<Factor, 4> Factors;
1777  if (!collectMultiplyFactors(Ops, Factors))
1778  return nullptr; // All distinct factors, so nothing left for us to do.
1779 
1780  IRBuilder<> Builder(I);
1781  // The reassociate transformation for FP operations is performed only
1782  // if unsafe algebra is permitted by FastMathFlags. Propagate those flags
1783  // to the newly generated operations.
1784  if (auto FPI = dyn_cast<FPMathOperator>(I))
1785  Builder.setFastMathFlags(FPI->getFastMathFlags());
1786 
1787  Value *V = buildMinimalMultiplyDAG(Builder, Factors);
1788  if (Ops.empty())
1789  return V;
1790 
1791  ValueEntry NewEntry = ValueEntry(getRank(V), V);
1792  Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry);
1793  return nullptr;
1794 }
1795 
1796 Value *ReassociatePass::OptimizeExpression(BinaryOperator *I,
1798  // Now that we have the linearized expression tree, try to optimize it.
1799  // Start by folding any constants that we found.
1800  Constant *Cst = nullptr;
1801  unsigned Opcode = I->getOpcode();
1802  while (!Ops.empty() && isa<Constant>(Ops.back().Op)) {
1803  Constant *C = cast<Constant>(Ops.pop_back_val().Op);
1804  Cst = Cst ? ConstantExpr::get(Opcode, C, Cst) : C;
1805  }
1806  // If there was nothing but constants then we are done.
1807  if (Ops.empty())
1808  return Cst;
1809 
1810  // Put the combined constant back at the end of the operand list, except if
1811  // there is no point. For example, an add of 0 gets dropped here, while a
1812  // multiplication by zero turns the whole expression into zero.
1813  if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) {
1814  if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType()))
1815  return Cst;
1816  Ops.push_back(ValueEntry(0, Cst));
1817  }
1818 
1819  if (Ops.size() == 1) return Ops[0].Op;
1820 
1821  // Handle destructive annihilation due to identities between elements in the
1822  // argument list here.
1823  unsigned NumOps = Ops.size();
1824  switch (Opcode) {
1825  default: break;
1826  case Instruction::And:
1827  case Instruction::Or:
1828  if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
1829  return Result;
1830  break;
1831 
1832  case Instruction::Xor:
1833  if (Value *Result = OptimizeXor(I, Ops))
1834  return Result;
1835  break;
1836 
1837  case Instruction::Add:
1838  case Instruction::FAdd:
1839  if (Value *Result = OptimizeAdd(I, Ops))
1840  return Result;
1841  break;
1842 
1843  case Instruction::Mul:
1844  case Instruction::FMul:
1845  if (Value *Result = OptimizeMul(I, Ops))
1846  return Result;
1847  break;
1848  }
1849 
1850  if (Ops.size() != NumOps)
1851  return OptimizeExpression(I, Ops);
1852  return nullptr;
1853 }
1854 
1855 // Remove dead instructions and if any operands are trivially dead add them to
1856 // Insts so they will be removed as well.
1857 void ReassociatePass::RecursivelyEraseDeadInsts(
1859  assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
1860  SmallVector<Value *, 4> Ops(I->op_begin(), I->op_end());
1861  ValueRankMap.erase(I);
1862  Insts.remove(I);
1863  RedoInsts.remove(I);
1864  I->eraseFromParent();
1865  for (auto Op : Ops)
1866  if (Instruction *OpInst = dyn_cast<Instruction>(Op))
1867  if (OpInst->use_empty())
1868  Insts.insert(OpInst);
1869 }
1870 
1871 /// Zap the given instruction, adding interesting operands to the work list.
1872 void ReassociatePass::EraseInst(Instruction *I) {
1873  assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
1874  DEBUG(dbgs() << "Erasing dead inst: "; I->dump());
1875 
1876  SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
1877  // Erase the dead instruction.
1878  ValueRankMap.erase(I);
1879  RedoInsts.remove(I);
1880  I->eraseFromParent();
1881  // Optimize its operands.
1882  SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes.
1883  for (unsigned i = 0, e = Ops.size(); i != e; ++i)
1884  if (Instruction *Op = dyn_cast<Instruction>(Ops[i])) {
1885  // If this is a node in an expression tree, climb to the expression root
1886  // and add that since that's where optimization actually happens.
1887  unsigned Opcode = Op->getOpcode();
1888  while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode &&
1889  Visited.insert(Op).second)
1890  Op = Op->user_back();
1891  RedoInsts.insert(Op);
1892  }
1893 }
1894 
1895 // Canonicalize expressions of the following form:
1896 // x + (-Constant * y) -> x - (Constant * y)
1897 // x - (-Constant * y) -> x + (Constant * y)
1898 Instruction *ReassociatePass::canonicalizeNegConstExpr(Instruction *I) {
1899  if (!I->hasOneUse() || I->getType()->isVectorTy())
1900  return nullptr;
1901 
1902  // Must be a fmul or fdiv instruction.
1903  unsigned Opcode = I->getOpcode();
1904  if (Opcode != Instruction::FMul && Opcode != Instruction::FDiv)
1905  return nullptr;
1906 
1907  auto *C0 = dyn_cast<ConstantFP>(I->getOperand(0));
1908  auto *C1 = dyn_cast<ConstantFP>(I->getOperand(1));
1909 
1910  // Both operands are constant, let it get constant folded away.
1911  if (C0 && C1)
1912  return nullptr;
1913 
1914  ConstantFP *CF = C0 ? C0 : C1;
1915 
1916  // Must have one constant operand.
1917  if (!CF)
1918  return nullptr;
1919 
1920  // Must be a negative ConstantFP.
1921  if (!CF->isNegative())
1922  return nullptr;
1923 
1924  // User must be a binary operator with one or more uses.
1925  Instruction *User = I->user_back();
1926  if (!isa<BinaryOperator>(User) || !User->hasNUsesOrMore(1))
1927  return nullptr;
1928 
1929  unsigned UserOpcode = User->getOpcode();
1930  if (UserOpcode != Instruction::FAdd && UserOpcode != Instruction::FSub)
1931  return nullptr;
1932 
1933  // Subtraction is not commutative. Explicitly, the following transform is
1934  // not valid: (-Constant * y) - x -> x + (Constant * y)
1935  if (!User->isCommutative() && User->getOperand(1) != I)
1936  return nullptr;
1937 
1938  // Change the sign of the constant.
1939  APFloat Val = CF->getValueAPF();
1940  Val.changeSign();
1941  I->setOperand(C0 ? 0 : 1, ConstantFP::get(CF->getContext(), Val));
1942 
1943  // Canonicalize I to RHS to simplify the next bit of logic. E.g.,
1944  // ((-Const*y) + x) -> (x + (-Const*y)).
1945  if (User->getOperand(0) == I && User->isCommutative())
1946  cast<BinaryOperator>(User)->swapOperands();
1947 
1948  Value *Op0 = User->getOperand(0);
1949  Value *Op1 = User->getOperand(1);
1950  BinaryOperator *NI;
1951  switch (UserOpcode) {
1952  default:
1953  llvm_unreachable("Unexpected Opcode!");
1954  case Instruction::FAdd:
1955  NI = BinaryOperator::CreateFSub(Op0, Op1);
1956  NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
1957  break;
1958  case Instruction::FSub:
1959  NI = BinaryOperator::CreateFAdd(Op0, Op1);
1960  NI->setFastMathFlags(cast<FPMathOperator>(User)->getFastMathFlags());
1961  break;
1962  }
1963 
1964  NI->insertBefore(User);
1965  NI->setName(User->getName());
1966  User->replaceAllUsesWith(NI);
1967  NI->setDebugLoc(I->getDebugLoc());
1968  RedoInsts.insert(I);
1969  MadeChange = true;
1970  return NI;
1971 }
1972 
1973 /// Inspect and optimize the given instruction. Note that erasing
1974 /// instructions is not allowed.
1975 void ReassociatePass::OptimizeInst(Instruction *I) {
1976  // Only consider operations that we understand.
1977  if (!isa<BinaryOperator>(I))
1978  return;
1979 
1980  if (I->getOpcode() == Instruction::Shl && isa<ConstantInt>(I->getOperand(1)))
1981  // If an operand of this shift is a reassociable multiply, or if the shift
1982  // is used by a reassociable multiply or add, turn into a multiply.
1983  if (isReassociableOp(I->getOperand(0), Instruction::Mul) ||
1984  (I->hasOneUse() &&
1985  (isReassociableOp(I->user_back(), Instruction::Mul) ||
1987  Instruction *NI = ConvertShiftToMul(I);
1988  RedoInsts.insert(I);
1989  MadeChange = true;
1990  I = NI;
1991  }
1992 
1993  // Canonicalize negative constants out of expressions.
1994  if (Instruction *Res = canonicalizeNegConstExpr(I))
1995  I = Res;
1996 
1997  // Commute binary operators, to canonicalize the order of their operands.
1998  // This can potentially expose more CSE opportunities, and makes writing other
1999  // transformations simpler.
2000  if (I->isCommutative())
2001  canonicalizeOperands(I);
2002 
2003  // TODO: We should optimize vector Xor instructions, but they are
2004  // currently unsupported.
2005  if (I->getType()->isVectorTy() && I->getOpcode() == Instruction::Xor)
2006  return;
2007 
2008  // Don't optimize floating point instructions that don't have unsafe algebra.
2009  if (I->getType()->isFPOrFPVectorTy() && !I->hasUnsafeAlgebra())
2010  return;
2011 
2012  // Do not reassociate boolean (i1) expressions. We want to preserve the
2013  // original order of evaluation for short-circuited comparisons that
2014  // SimplifyCFG has folded to AND/OR expressions. If the expression
2015  // is not further optimized, it is likely to be transformed back to a
2016  // short-circuited form for code gen, and the source order may have been
2017  // optimized for the most likely conditions.
2018  if (I->getType()->isIntegerTy(1))
2019  return;
2020 
2021  // If this is a subtract instruction which is not already in negate form,
2022  // see if we can convert it to X+-Y.
2023  if (I->getOpcode() == Instruction::Sub) {
2024  if (ShouldBreakUpSubtract(I)) {
2025  Instruction *NI = BreakUpSubtract(I, RedoInsts);
2026  RedoInsts.insert(I);
2027  MadeChange = true;
2028  I = NI;
2029  } else if (BinaryOperator::isNeg(I)) {
2030  // Otherwise, this is a negation. See if the operand is a multiply tree
2031  // and if this is not an inner node of a multiply tree.
2032  if (isReassociableOp(I->getOperand(1), Instruction::Mul) &&
2033  (!I->hasOneUse() ||
2034  !isReassociableOp(I->user_back(), Instruction::Mul))) {
2036  // If the negate was simplified, revisit the users to see if we can
2037  // reassociate further.
2038  for (User *U : NI->users()) {
2039  if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
2040  RedoInsts.insert(Tmp);
2041  }
2042  RedoInsts.insert(I);
2043  MadeChange = true;
2044  I = NI;
2045  }
2046  }
2047  } else if (I->getOpcode() == Instruction::FSub) {
2048  if (ShouldBreakUpSubtract(I)) {
2049  Instruction *NI = BreakUpSubtract(I, RedoInsts);
2050  RedoInsts.insert(I);
2051  MadeChange = true;
2052  I = NI;
2053  } else if (BinaryOperator::isFNeg(I)) {
2054  // Otherwise, this is a negation. See if the operand is a multiply tree
2055  // and if this is not an inner node of a multiply tree.
2056  if (isReassociableOp(I->getOperand(1), Instruction::FMul) &&
2057  (!I->hasOneUse() ||
2058  !isReassociableOp(I->user_back(), Instruction::FMul))) {
2059  // If the negate was simplified, revisit the users to see if we can
2060  // reassociate further.
2062  for (User *U : NI->users()) {
2063  if (BinaryOperator *Tmp = dyn_cast<BinaryOperator>(U))
2064  RedoInsts.insert(Tmp);
2065  }
2066  RedoInsts.insert(I);
2067  MadeChange = true;
2068  I = NI;
2069  }
2070  }
2071  }
2072 
2073  // If this instruction is an associative binary operator, process it.
2074  if (!I->isAssociative()) return;
2075  BinaryOperator *BO = cast<BinaryOperator>(I);
2076 
2077  // If this is an interior node of a reassociable tree, ignore it until we
2078  // get to the root of the tree, to avoid N^2 analysis.
2079  unsigned Opcode = BO->getOpcode();
2080  if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode) {
2081  // During the initial run we will get to the root of the tree.
2082  // But if we get here while we are redoing instructions, there is no
2083  // guarantee that the root will be visited. So Redo later
2084  if (BO->user_back() != BO &&
2085  BO->getParent() == BO->user_back()->getParent())
2086  RedoInsts.insert(BO->user_back());
2087  return;
2088  }
2089 
2090  // If this is an add tree that is used by a sub instruction, ignore it
2091  // until we process the subtract.
2092  if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
2093  cast<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub)
2094  return;
2095  if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd &&
2096  cast<Instruction>(BO->user_back())->getOpcode() == Instruction::FSub)
2097  return;
2098 
2099  ReassociateExpression(BO);
2100 }
2101 
2102 void ReassociatePass::ReassociateExpression(BinaryOperator *I) {
2103  // First, walk the expression tree, linearizing the tree, collecting the
2104  // operand information.
2106  MadeChange |= LinearizeExprTree(I, Tree);
2108  Ops.reserve(Tree.size());
2109  for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
2110  RepeatedValue E = Tree[i];
2111  Ops.append(E.second.getZExtValue(),
2112  ValueEntry(getRank(E.first), E.first));
2113  }
2114 
2115  DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
2116 
2117  // Now that we have linearized the tree to a list and have gathered all of
2118  // the operands and their ranks, sort the operands by their rank. Use a
2119  // stable_sort so that values with equal ranks will have their relative
2120  // positions maintained (and so the compiler is deterministic). Note that
2121  // this sorts so that the highest ranking values end up at the beginning of
2122  // the vector.
2123  std::stable_sort(Ops.begin(), Ops.end());
2124 
2125  // Now that we have the expression tree in a convenient
2126  // sorted form, optimize it globally if possible.
2127  if (Value *V = OptimizeExpression(I, Ops)) {
2128  if (V == I)
2129  // Self-referential expression in unreachable code.
2130  return;
2131  // This expression tree simplified to something that isn't a tree,
2132  // eliminate it.
2133  DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
2134  I->replaceAllUsesWith(V);
2135  if (Instruction *VI = dyn_cast<Instruction>(V))
2136  VI->setDebugLoc(I->getDebugLoc());
2137  RedoInsts.insert(I);
2138  ++NumAnnihil;
2139  return;
2140  }
2141 
2142  // We want to sink immediates as deeply as possible except in the case where
2143  // this is a multiply tree used only by an add, and the immediate is a -1.
2144  // In this case we reassociate to put the negation on the outside so that we
2145  // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
2146  if (I->hasOneUse()) {
2147  if (I->getOpcode() == Instruction::Mul &&
2148  cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
2149  isa<ConstantInt>(Ops.back().Op) &&
2150  cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
2151  ValueEntry Tmp = Ops.pop_back_val();
2152  Ops.insert(Ops.begin(), Tmp);
2153  } else if (I->getOpcode() == Instruction::FMul &&
2154  cast<Instruction>(I->user_back())->getOpcode() ==
2155  Instruction::FAdd &&
2156  isa<ConstantFP>(Ops.back().Op) &&
2157  cast<ConstantFP>(Ops.back().Op)->isExactlyValue(-1.0)) {
2158  ValueEntry Tmp = Ops.pop_back_val();
2159  Ops.insert(Ops.begin(), Tmp);
2160  }
2161  }
2162 
2163  DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
2164 
2165  if (Ops.size() == 1) {
2166  if (Ops[0].Op == I)
2167  // Self-referential expression in unreachable code.
2168  return;
2169 
2170  // This expression tree simplified to something that isn't a tree,
2171  // eliminate it.
2172  I->replaceAllUsesWith(Ops[0].Op);
2173  if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
2174  OI->setDebugLoc(I->getDebugLoc());
2175  RedoInsts.insert(I);
2176  return;
2177  }
2178 
2179  // Now that we ordered and optimized the expressions, splat them back into
2180  // the expression tree, removing any unneeded nodes.
2181  RewriteExprTree(I, Ops);
2182 }
2183 
2185  // Get the functions basic blocks in Reverse Post Order. This order is used by
2186  // BuildRankMap to pre calculate ranks correctly. It also excludes dead basic
2187  // blocks (it has been seen that the analysis in this pass could hang when
2188  // analysing dead basic blocks).
2190 
2191  // Calculate the rank map for F.
2192  BuildRankMap(F, RPOT);
2193 
2194  MadeChange = false;
2195  // Traverse the same blocks that was analysed by BuildRankMap.
2196  for (BasicBlock *BI : RPOT) {
2197  assert(RankMap.count(&*BI) && "BB should be ranked.");
2198  // Optimize every instruction in the basic block.
2199  for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;)
2200  if (isInstructionTriviallyDead(&*II)) {
2201  EraseInst(&*II++);
2202  } else {
2203  OptimizeInst(&*II);
2204  assert(II->getParent() == &*BI && "Moved to a different block!");
2205  ++II;
2206  }
2207 
2208  // Make a copy of all the instructions to be redone so we can remove dead
2209  // instructions.
2210  SetVector<AssertingVH<Instruction>> ToRedo(RedoInsts);
2211  // Iterate over all instructions to be reevaluated and remove trivially dead
2212  // instructions. If any operand of the trivially dead instruction becomes
2213  // dead mark it for deletion as well. Continue this process until all
2214  // trivially dead instructions have been removed.
2215  while (!ToRedo.empty()) {
2216  Instruction *I = ToRedo.pop_back_val();
2217  if (isInstructionTriviallyDead(I)) {
2218  RecursivelyEraseDeadInsts(I, ToRedo);
2219  MadeChange = true;
2220  }
2221  }
2222 
2223  // Now that we have removed dead instructions, we can reoptimize the
2224  // remaining instructions.
2225  while (!RedoInsts.empty()) {
2226  Instruction *I = RedoInsts.pop_back_val();
2228  EraseInst(I);
2229  else
2230  OptimizeInst(I);
2231  }
2232  }
2233 
2234  // We are done with the rank map.
2235  RankMap.clear();
2236  ValueRankMap.clear();
2237 
2238  if (MadeChange) {
2239  // FIXME: This should also 'preserve the CFG'.
2240  auto PA = PreservedAnalyses();
2241  PA.preserve<GlobalsAA>();
2242  return PA;
2243  }
2244 
2245  return PreservedAnalyses::all();
2246 }
2247 
2248 namespace {
2249  class ReassociateLegacyPass : public FunctionPass {
2250  ReassociatePass Impl;
2251  public:
2252  static char ID; // Pass identification, replacement for typeid
2253  ReassociateLegacyPass() : FunctionPass(ID) {
2255  }
2256 
2257  bool runOnFunction(Function &F) override {
2258  if (skipFunction(F))
2259  return false;
2260 
2261  FunctionAnalysisManager DummyFAM;
2262  auto PA = Impl.run(F, DummyFAM);
2263  return !PA.areAllPreserved();
2264  }
2265 
2266  void getAnalysisUsage(AnalysisUsage &AU) const override {
2267  AU.setPreservesCFG();
2269  }
2270  };
2271 }
2272 
2273 char ReassociateLegacyPass::ID = 0;
2274 INITIALIZE_PASS(ReassociateLegacyPass, "reassociate",
2275  "Reassociate expressions", false, false)
2276 
2277 // Public interface to the Reassociate pass
2279  return new ReassociateLegacyPass();
2280 }
Legacy wrapper pass to provide the GlobalsAAResult object.
bool isNilpotent() const
Return true if the instruction is nilpotent:
Definition: Instruction.h:406
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks 'this' from the containing basic block and deletes it.
Definition: Instruction.cpp:76
void push_back(const T &Elt)
Definition: SmallVector.h:211
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:1309
STATISTIC(NumFunctions,"Total number of functions")
LLVM_NODISCARD T pop_back_val()
Definition: SetVector.h:222
static BinaryOperator * LowerNegateToMultiply(Instruction *Neg)
Replace 0-X with X*-1.
size_t i
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:52
Utility class representing a non-constant Xor-operand.
Definition: Reassociate.cpp:77
static Constant * getBinOpIdentity(unsigned Opcode, Type *Ty)
Return the identity for the given binary operation, i.e.
Definition: Constants.cpp:2220
size_type count(PtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:380
nary reassociate
Utility class representing a base and exponent pair which form one factor of some product...
Definition: Reassociate.h:48
FastMathFlags getFastMathFlags() const
Convenience function for getting all the fast-math flags, which must be an operator which supports th...
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:100
arg_iterator arg_end()
Definition: Function.h:559
void changeSign()
Definition: APFloat.h:975
void reserve(size_type N)
Definition: SmallVector.h:377
Reassociate commutative expressions.
Definition: Reassociate.h:58
op_iterator op_begin()
Definition: User.h:205
static void FindSingleUseMultiplyFactors(Value *V, SmallVectorImpl< Value * > &Factors, const SmallVectorImpl< ValueEntry > &Ops)
If V is a single-use multiply, recursively add its operands as factors, otherwise add V to the list o...
static Constant * getNullValue(Type *Ty)
Constructor to create a '0' constant of arbitrary type.
Definition: Constants.cpp:195
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:191
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:228
Value * getValue() const
Definition: Reassociate.cpp:83
bool swapOperands()
Exchange the two operands to this instruction.
static const Value * getNegArgument(const Value *BinOp)
Helper functions to extract the unary argument of a NEG, FNEG or NOT operation implemented via Sub...
struct fuzzer::@269 Flags
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:32
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:588
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:257
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:60
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:1728
static Value * OptimizeAndOrXor(unsigned Opcode, SmallVectorImpl< ValueEntry > &Ops)
Optimize a series of operands to an 'and', 'or', or 'xor' instruction.
#define F(x, y, z)
Definition: MD5.cpp:51
LLVMContext & getContext() const
Return the LLVMContext in which this type was uniqued.
Definition: Type.h:128
std::pair< Value *, APInt > RepeatedValue
bool isAssociative() const
Return true if the instruction is associative:
void andIRFlags(const Value *V)
Logical 'and' of any supported wrapping, exact, and fast-math flags of V and this instruction...
bool hasUnsafeAlgebra() const
Determine whether the unsafe-algebra flag is set.
bool empty() const
Determine if the SetVector is empty or not.
Definition: SetVector.h:73
static Value * createAndInstr(Instruction *InsertBefore, Value *Opnd, const APInt &ConstOpnd)
Helper function of CombineXorOpnd().
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:401
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:263
const char * getOpcodeName() const
Definition: Instruction.h:113
Type * getScalarType() const LLVM_READONLY
If this is a vector type, return the element type, otherwise return 'this'.
Definition: Type.cpp:44
static BinaryOperator * CreateAdd(Value *S1, Value *S2, const Twine &Name, Instruction *InsertBefore, Value *FlagsOp)
static const Value * getNotArgument(const Value *BinOp)
bool ult(const APInt &RHS) const
Unsigned less than comparison.
Definition: APInt.cpp:501
Value * getSymbolicPart() const
Definition: Reassociate.cpp:84
static GCRegistry::Add< CoreCLRGC > E("coreclr","CoreCLR-compatible GC")
#define P(N)
bool isIntOrIntVectorTy() const
Return true if this is an integer type or a vector of integer types.
Definition: Type.h:201
static Constant * getFNeg(Constant *C)
Definition: Constants.cpp:2120
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:107
static Value * buildMultiplyTree(IRBuilder<> &Builder, SmallVectorImpl< Value * > &Ops)
Build a tree of multiplies, computing the product of Ops.
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:256
void insertBefore(Instruction *InsertPos)
Insert an unlinked instruction into a basic block immediately before the specified instruction...
Definition: Instruction.cpp:82
LLVM Basic Block Representation.
Definition: BasicBlock.h:51
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:48
bool isVectorTy() const
True if this is an instance of VectorType.
Definition: Type.h:219
This is an important base class in LLVM.
Definition: Constant.h:42
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator begin()
Definition: SmallVector.h:115
This file contains the declarations for the subclasses of Constant, which represent the different fla...
APInt Or(const APInt &LHS, const APInt &RHS)
Bitwise OR function for APInt.
Definition: APInt.h:1947
static Value * EmitAddTreeOfValues(Instruction *I, SmallVectorImpl< WeakVH > &Ops)
Emit a tree of add instructions, summing Ops together and returning the result.
ConstantFP - Floating Point Values [float, double].
Definition: Constants.h:269
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:368
APInt Xor(const APInt &LHS, const APInt &RHS)
Bitwise XOR function for APInt.
Definition: APInt.h:1952
static APInt getOneBitSet(unsigned numBits, unsigned BitNo)
Return an APInt with exactly one bit set in the result.
Definition: APInt.h:484
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:259
Represent the analysis usage information of a pass.
op_iterator op_end()
Definition: User.h:207
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang","erlang-compatible garbage collector")
Analysis pass providing a never-invalidated alias analysis result.
unsigned getBitWidth() const
Return the number of bits in the APInt.
Definition: APInt.h:1255
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:298
Value * getOperand(unsigned i) const
Definition: User.h:145
bool isCommutative() const
Return true if the instruction is commutative:
Definition: Instruction.h:385
arg_iterator arg_begin()
Definition: Function.h:550
static bool isNot(const Value *V)
self_iterator getIterator()
Definition: ilist_node.h:81
unsigned getIntegerBitWidth() const
Definition: DerivedTypes.h:96
static Constant * getAllOnesValue(Type *Ty)
Get the all ones value.
Definition: Constants.cpp:249
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...
void append(in_iter in_start, in_iter in_end)
Add the specified range to the end of the SmallVector.
Definition: SmallVector.h:392
static UndefValue * get(Type *T)
Static factory methods - Return an 'undef' object of the specified type.
Definition: Constants.cpp:1337
iterator erase(const_iterator CI)
Definition: SmallVector.h:431
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:113
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:654
static unsigned CarmichaelShift(unsigned Bitwidth)
Returns k such that lambda(2^Bitwidth) = 2^k, where lambda is the Carmichael function.
bool isFPOrFPVectorTy() const
Return true if this is a FP type or a vector of FP.
Definition: Type.h:183
#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:857
void dump() const
Support for debugging, callable in GDB: V->dump()
Definition: AsmWriter.cpp:3540
unsigned getSymbolicRank() const
Definition: Reassociate.cpp:85
BinaryOps getOpcode() const
Definition: InstrTypes.h:541
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.
INITIALIZE_PASS(ReassociateLegacyPass,"reassociate","Reassociate expressions", false, false) FunctionPass *llvm
This is the shared class of boolean and integer constants.
Definition: Constants.h:88
const Module * getModule() const
Return the module owning the function this instruction belongs to or nullptr it the function does not...
Definition: Instruction.cpp:58
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 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:843
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:230
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:59
const APInt & getConstPart() const
Definition: Reassociate.cpp:86
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:382
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:558
void setSymbolicRank(unsigned R)
Definition: Reassociate.cpp:89
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:276
const BasicBlock & getEntryBlock() const
Definition: Function.h:519
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:623
Value handle that asserts if the Value is deleted.
Definition: ValueHandle.h:182
static GCRegistry::Add< ShadowStackGC > C("shadow-stack","Very portable GC for uncooperative code generators")
void setOperand(unsigned i, Value *Val)
Definition: User.h:150
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:586
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:77
bool isIntegerTy() const
True if this is an instance of IntegerType.
Definition: Type.h:195
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:370
iterator insert(iterator I, T &&Elt)
Definition: SmallVector.h:464
bool isMinValue() const
Determine if this is the smallest unsigned value.
Definition: APInt.h:366
APInt And(const APInt &LHS, const APInt &RHS)
Bitwise AND function for APInt.
Definition: APInt.h:1942
static Constant * getNeg(Constant *C, bool HasNUW=false, bool HasNSW=false)
Definition: Constants.cpp:2113
bool isAllOnesValue() const
Determine if all bits are set.
Definition: APInt.h:342
bool isNegative() const
Return true if the sign bit is set.
Definition: Constants.h:306
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:119
iterator insert(iterator where, pointer New)
Definition: ilist.h:241
void emplace_back(ArgTypes &&...Args)
Definition: SmallVector.h:635
bool mayBeMemoryDependent(const Instruction &I)
Returns true if the result or effects of the given instructions I depend on or influence global memor...
static bool isFNeg(const Value *V, bool IgnoreZeroSign=false)
bool isIdempotent() const
Return true if the instruction is idempotent:
Definition: Instruction.h:394
static void PrintOps(Instruction *I, const SmallVectorImpl< ValueEntry > &Ops)
Print out the expression identified in the Ops list.
Definition: Reassociate.cpp:57
static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode)
Add the extra weight 'RHS' to the existing weight 'LHS', reducing the combined weight using any speci...
#define I(x, y, z)
Definition: MD5.cpp:54
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:135
bool hasOneUse() const
Return true if there is exactly one user of this value.
Definition: Value.h:383
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:287
static Constant * getShl(Constant *C1, Constant *C2, bool HasNUW=false, bool HasNSW=false)
Definition: Constants.cpp:2203
static BinaryOperator * CreateNeg(Value *S1, const Twine &Name, Instruction *InsertBefore, Value *FlagsOp)
bool hasNUsesOrMore(unsigned N) const
Return true if this value has N users or more.
Definition: Value.cpp:107
const APFloat & getValueAPF() const
Definition: Constants.h:300
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...
bool use_empty() const
Definition: Value.h:299
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
user_iterator user_begin()
Definition: Value.h:346
void initializeReassociateLegacyPassPass(PassRegistry &)
unsigned getPrimitiveSizeInBits() const LLVM_READONLY
Return the basic size of this type if it is a primitive type.
Definition: Type.cpp:108
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:288
LLVM Value Representation.
Definition: Value.h:71
static unsigned FindInOperandList(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...
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:111
A vector that has set insertion semantics.
Definition: SetVector.h:41
void clearSubclassOptionalData()
Clear the optional flags contained in this value.
Definition: Value.h:446
void setFastMathFlags(FastMathFlags NewFMF)
Set the fast-math flags to be used with generated fp-math operators.
Definition: IRBuilder.h:220
void moveBefore(Instruction *MovePos)
Unlink this instruction from its current basic block and insert it into the basic block that MovePos ...
Definition: Instruction.cpp:95
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:100
cmpResult compare(const APFloat &RHS) const
Definition: APFloat.h:1018
IRTranslator LLVM IR MI
Convenience struct for specifying and reasoning about fast-math flags.
Definition: Operator.h:168
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 '0' value.
Definition: APInt.h:465
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:871
static Constant * getBinOpAbsorber(unsigned Opcode, Type *Ty)
Return the absorbing element for the given binary operation, i.e.
Definition: Constants.cpp:2239
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...
const BasicBlock * getParent() const
Definition: Instruction.h:62
User * user_back()
Definition: Value.h:356
PreservedAnalyses run(Function &F, FunctionAnalysisManager &)