InstructionSimplify.cpp revision 28e215ba63164f201292f8c77bf038b4282aa052 
1//===- InstructionSimplify.cpp - Fold instruction operands ----------------===//
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 file implements routines for folding instructions into simpler forms
11// that do not require creating new instructions.  This does constant folding
12// ("add i32 1, 1" -> "2") but can also handle non-constant operands, either
13// returning a constant ("and i32 %x, 0" -> "0") or an already existing value
14// ("and i32 %x, %x" -> "%x").  All operands are assumed to have already been
15// simplified: This is usually true and assuming it simplifies the logic (if
16// they have not been simplified then results are correct but maybe suboptimal).
17//
18//===----------------------------------------------------------------------===//
19
20#define DEBUG_TYPE "instsimplify"
21#include "llvm/Operator.h"
22#include "llvm/ADT/Statistic.h"
23#include "llvm/Analysis/InstructionSimplify.h"
24#include "llvm/Analysis/AliasAnalysis.h"
25#include "llvm/Analysis/ConstantFolding.h"
26#include "llvm/Analysis/Dominators.h"
27#include "llvm/Analysis/ValueTracking.h"
28#include "llvm/Support/ConstantRange.h"
29#include "llvm/Support/PatternMatch.h"
30#include "llvm/Support/ValueHandle.h"
31#include "llvm/Target/TargetData.h"
32using namespace llvm;
33using namespace llvm::PatternMatch;
34
35enum { RecursionLimit = 3 };
36
37STATISTIC(NumExpand,  "Number of expansions");
38STATISTIC(NumFactor , "Number of factorizations");
39STATISTIC(NumReassoc, "Number of reassociations");
40
41static Value *SimplifyAndInst(Value *, Value *, const TargetData *,
42                              const TargetLibraryInfo *, const DominatorTree *,
43                              unsigned);
44static Value *SimplifyBinOp(unsigned, Value *, Value *, const TargetData *,
45                            const TargetLibraryInfo *, const DominatorTree *,
46                            unsigned);
47static Value *SimplifyCmpInst(unsigned, Value *, Value *, const TargetData *,
48                              const TargetLibraryInfo *, const DominatorTree *,
49                              unsigned);
50static Value *SimplifyOrInst(Value *, Value *, const TargetData *,
51                             const TargetLibraryInfo *, const DominatorTree *,
52                             unsigned);
53static Value *SimplifyXorInst(Value *, Value *, const TargetData *,
54                              const TargetLibraryInfo *, const DominatorTree *,
55                              unsigned);
56
57/// getFalse - For a boolean type, or a vector of boolean type, return false, or
58/// a vector with every element false, as appropriate for the type.
59static Constant *getFalse(Type *Ty) {
60  assert(Ty->getScalarType()->isIntegerTy(1) &&
61         "Expected i1 type or a vector of i1!");
62  return Constant::getNullValue(Ty);
63}
64
65/// getTrue - For a boolean type, or a vector of boolean type, return true, or
66/// a vector with every element true, as appropriate for the type.
67static Constant *getTrue(Type *Ty) {
68  assert(Ty->getScalarType()->isIntegerTy(1) &&
69         "Expected i1 type or a vector of i1!");
70  return Constant::getAllOnesValue(Ty);
71}
72
73/// isSameCompare - Is V equivalent to the comparison "LHS Pred RHS"?
74static bool isSameCompare(Value *V, CmpInst::Predicate Pred, Value *LHS,
75                          Value *RHS) {
76  CmpInst *Cmp = dyn_cast<CmpInst>(V);
77  if (!Cmp)
78    return false;
79  CmpInst::Predicate CPred = Cmp->getPredicate();
80  Value *CLHS = Cmp->getOperand(0), *CRHS = Cmp->getOperand(1);
81  if (CPred == Pred && CLHS == LHS && CRHS == RHS)
82    return true;
83  return CPred == CmpInst::getSwappedPredicate(Pred) && CLHS == RHS &&
84    CRHS == LHS;
85}
86
87/// ValueDominatesPHI - Does the given value dominate the specified phi node?
88static bool ValueDominatesPHI(Value *V, PHINode *P, const DominatorTree *DT) {
89  Instruction *I = dyn_cast<Instruction>(V);
90  if (!I)
91    // Arguments and constants dominate all instructions.
92    return true;
93
94  // If we have a DominatorTree then do a precise test.
95  if (DT)
96    return DT->dominates(I, P);
97
98  // Otherwise, if the instruction is in the entry block, and is not an invoke,
99  // then it obviously dominates all phi nodes.
100  if (I->getParent() == &I->getParent()->getParent()->getEntryBlock() &&
101      !isa<InvokeInst>(I))
102    return true;
103
104  return false;
105}
106
107/// ExpandBinOp - Simplify "A op (B op' C)" by distributing op over op', turning
108/// it into "(A op B) op' (A op C)".  Here "op" is given by Opcode and "op'" is
109/// given by OpcodeToExpand, while "A" corresponds to LHS and "B op' C" to RHS.
110/// Also performs the transform "(A op' B) op C" -> "(A op C) op' (B op C)".
111/// Returns the simplified value, or null if no simplification was performed.
112static Value *ExpandBinOp(unsigned Opcode, Value *LHS, Value *RHS,
113                          unsigned OpcToExpand, const TargetData *TD,
114                          const TargetLibraryInfo *TLI, const DominatorTree *DT,
115                          unsigned MaxRecurse) {
116  Instruction::BinaryOps OpcodeToExpand = (Instruction::BinaryOps)OpcToExpand;
117  // Recursion is always used, so bail out at once if we already hit the limit.
118  if (!MaxRecurse--)
119    return 0;
120
121  // Check whether the expression has the form "(A op' B) op C".
122  if (BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS))
123    if (Op0->getOpcode() == OpcodeToExpand) {
124      // It does!  Try turning it into "(A op C) op' (B op C)".
125      Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS;
126      // Do "A op C" and "B op C" both simplify?
127      if (Value *L = SimplifyBinOp(Opcode, A, C, TD, TLI, DT, MaxRecurse))
128        if (Value *R = SimplifyBinOp(Opcode, B, C, TD, TLI, DT, MaxRecurse)) {
129          // They do! Return "L op' R" if it simplifies or is already available.
130          // If "L op' R" equals "A op' B" then "L op' R" is just the LHS.
131          if ((L == A && R == B) || (Instruction::isCommutative(OpcodeToExpand)
132                                     && L == B && R == A)) {
133            ++NumExpand;
134            return LHS;
135          }
136          // Otherwise return "L op' R" if it simplifies.
137          if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, TLI, DT,
138                                       MaxRecurse)) {
139            ++NumExpand;
140            return V;
141          }
142        }
143    }
144
145  // Check whether the expression has the form "A op (B op' C)".
146  if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS))
147    if (Op1->getOpcode() == OpcodeToExpand) {
148      // It does!  Try turning it into "(A op B) op' (A op C)".
149      Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1);
150      // Do "A op B" and "A op C" both simplify?
151      if (Value *L = SimplifyBinOp(Opcode, A, B, TD, TLI, DT, MaxRecurse))
152        if (Value *R = SimplifyBinOp(Opcode, A, C, TD, TLI, DT, MaxRecurse)) {
153          // They do! Return "L op' R" if it simplifies or is already available.
154          // If "L op' R" equals "B op' C" then "L op' R" is just the RHS.
155          if ((L == B && R == C) || (Instruction::isCommutative(OpcodeToExpand)
156                                     && L == C && R == B)) {
157            ++NumExpand;
158            return RHS;
159          }
160          // Otherwise return "L op' R" if it simplifies.
161          if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, TLI, DT,
162                                       MaxRecurse)) {
163            ++NumExpand;
164            return V;
165          }
166        }
167    }
168
169  return 0;
170}
171
172/// FactorizeBinOp - Simplify "LHS Opcode RHS" by factorizing out a common term
173/// using the operation OpCodeToExtract.  For example, when Opcode is Add and
174/// OpCodeToExtract is Mul then this tries to turn "(A*B)+(A*C)" into "A*(B+C)".
175/// Returns the simplified value, or null if no simplification was performed.
176static Value *FactorizeBinOp(unsigned Opcode, Value *LHS, Value *RHS,
177                             unsigned OpcToExtract, const TargetData *TD,
178                             const TargetLibraryInfo *TLI,
179                             const DominatorTree *DT,
180                             unsigned MaxRecurse) {
181  Instruction::BinaryOps OpcodeToExtract = (Instruction::BinaryOps)OpcToExtract;
182  // Recursion is always used, so bail out at once if we already hit the limit.
183  if (!MaxRecurse--)
184    return 0;
185
186  BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
187  BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
188
189  if (!Op0 || Op0->getOpcode() != OpcodeToExtract ||
190      !Op1 || Op1->getOpcode() != OpcodeToExtract)
191    return 0;
192
193  // The expression has the form "(A op' B) op (C op' D)".
194  Value *A = Op0->getOperand(0), *B = Op0->getOperand(1);
195  Value *C = Op1->getOperand(0), *D = Op1->getOperand(1);
196
197  // Use left distributivity, i.e. "X op' (Y op Z) = (X op' Y) op (X op' Z)".
198  // Does the instruction have the form "(A op' B) op (A op' D)" or, in the
199  // commutative case, "(A op' B) op (C op' A)"?
200  if (A == C || (Instruction::isCommutative(OpcodeToExtract) && A == D)) {
201    Value *DD = A == C ? D : C;
202    // Form "A op' (B op DD)" if it simplifies completely.
203    // Does "B op DD" simplify?
204    if (Value *V = SimplifyBinOp(Opcode, B, DD, TD, TLI, DT, MaxRecurse)) {
205      // It does!  Return "A op' V" if it simplifies or is already available.
206      // If V equals B then "A op' V" is just the LHS.  If V equals DD then
207      // "A op' V" is just the RHS.
208      if (V == B || V == DD) {
209        ++NumFactor;
210        return V == B ? LHS : RHS;
211      }
212      // Otherwise return "A op' V" if it simplifies.
213      if (Value *W = SimplifyBinOp(OpcodeToExtract, A, V, TD, TLI, DT,
214                                   MaxRecurse)) {
215        ++NumFactor;
216        return W;
217      }
218    }
219  }
220
221  // Use right distributivity, i.e. "(X op Y) op' Z = (X op' Z) op (Y op' Z)".
222  // Does the instruction have the form "(A op' B) op (C op' B)" or, in the
223  // commutative case, "(A op' B) op (B op' D)"?
224  if (B == D || (Instruction::isCommutative(OpcodeToExtract) && B == C)) {
225    Value *CC = B == D ? C : D;
226    // Form "(A op CC) op' B" if it simplifies completely..
227    // Does "A op CC" simplify?
228    if (Value *V = SimplifyBinOp(Opcode, A, CC, TD, TLI, DT, MaxRecurse)) {
229      // It does!  Return "V op' B" if it simplifies or is already available.
230      // If V equals A then "V op' B" is just the LHS.  If V equals CC then
231      // "V op' B" is just the RHS.
232      if (V == A || V == CC) {
233        ++NumFactor;
234        return V == A ? LHS : RHS;
235      }
236      // Otherwise return "V op' B" if it simplifies.
237      if (Value *W = SimplifyBinOp(OpcodeToExtract, V, B, TD, TLI, DT,
238                                   MaxRecurse)) {
239        ++NumFactor;
240        return W;
241      }
242    }
243  }
244
245  return 0;
246}
247
248/// SimplifyAssociativeBinOp - Generic simplifications for associative binary
249/// operations.  Returns the simpler value, or null if none was found.
250static Value *SimplifyAssociativeBinOp(unsigned Opc, Value *LHS, Value *RHS,
251                                       const TargetData *TD,
252                                       const TargetLibraryInfo *TLI,
253                                       const DominatorTree *DT,
254                                       unsigned MaxRecurse) {
255  Instruction::BinaryOps Opcode = (Instruction::BinaryOps)Opc;
256  assert(Instruction::isAssociative(Opcode) && "Not an associative operation!");
257
258  // Recursion is always used, so bail out at once if we already hit the limit.
259  if (!MaxRecurse--)
260    return 0;
261
262  BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
263  BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
264
265  // Transform: "(A op B) op C" ==> "A op (B op C)" if it simplifies completely.
266  if (Op0 && Op0->getOpcode() == Opcode) {
267    Value *A = Op0->getOperand(0);
268    Value *B = Op0->getOperand(1);
269    Value *C = RHS;
270
271    // Does "B op C" simplify?
272    if (Value *V = SimplifyBinOp(Opcode, B, C, TD, TLI, DT, MaxRecurse)) {
273      // It does!  Return "A op V" if it simplifies or is already available.
274      // If V equals B then "A op V" is just the LHS.
275      if (V == B) return LHS;
276      // Otherwise return "A op V" if it simplifies.
277      if (Value *W = SimplifyBinOp(Opcode, A, V, TD, TLI, DT, MaxRecurse)) {
278        ++NumReassoc;
279        return W;
280      }
281    }
282  }
283
284  // Transform: "A op (B op C)" ==> "(A op B) op C" if it simplifies completely.
285  if (Op1 && Op1->getOpcode() == Opcode) {
286    Value *A = LHS;
287    Value *B = Op1->getOperand(0);
288    Value *C = Op1->getOperand(1);
289
290    // Does "A op B" simplify?
291    if (Value *V = SimplifyBinOp(Opcode, A, B, TD, TLI, DT, MaxRecurse)) {
292      // It does!  Return "V op C" if it simplifies or is already available.
293      // If V equals B then "V op C" is just the RHS.
294      if (V == B) return RHS;
295      // Otherwise return "V op C" if it simplifies.
296      if (Value *W = SimplifyBinOp(Opcode, V, C, TD, TLI, DT, MaxRecurse)) {
297        ++NumReassoc;
298        return W;
299      }
300    }
301  }
302
303  // The remaining transforms require commutativity as well as associativity.
304  if (!Instruction::isCommutative(Opcode))
305    return 0;
306
307  // Transform: "(A op B) op C" ==> "(C op A) op B" if it simplifies completely.
308  if (Op0 && Op0->getOpcode() == Opcode) {
309    Value *A = Op0->getOperand(0);
310    Value *B = Op0->getOperand(1);
311    Value *C = RHS;
312
313    // Does "C op A" simplify?
314    if (Value *V = SimplifyBinOp(Opcode, C, A, TD, TLI, DT, MaxRecurse)) {
315      // It does!  Return "V op B" if it simplifies or is already available.
316      // If V equals A then "V op B" is just the LHS.
317      if (V == A) return LHS;
318      // Otherwise return "V op B" if it simplifies.
319      if (Value *W = SimplifyBinOp(Opcode, V, B, TD, TLI, DT, MaxRecurse)) {
320        ++NumReassoc;
321        return W;
322      }
323    }
324  }
325
326  // Transform: "A op (B op C)" ==> "B op (C op A)" if it simplifies completely.
327  if (Op1 && Op1->getOpcode() == Opcode) {
328    Value *A = LHS;
329    Value *B = Op1->getOperand(0);
330    Value *C = Op1->getOperand(1);
331
332    // Does "C op A" simplify?
333    if (Value *V = SimplifyBinOp(Opcode, C, A, TD, TLI, DT, MaxRecurse)) {
334      // It does!  Return "B op V" if it simplifies or is already available.
335      // If V equals C then "B op V" is just the RHS.
336      if (V == C) return RHS;
337      // Otherwise return "B op V" if it simplifies.
338      if (Value *W = SimplifyBinOp(Opcode, B, V, TD, TLI, DT, MaxRecurse)) {
339        ++NumReassoc;
340        return W;
341      }
342    }
343  }
344
345  return 0;
346}
347
348/// ThreadBinOpOverSelect - In the case of a binary operation with a select
349/// instruction as an operand, try to simplify the binop by seeing whether
350/// evaluating it on both branches of the select results in the same value.
351/// Returns the common value if so, otherwise returns null.
352static Value *ThreadBinOpOverSelect(unsigned Opcode, Value *LHS, Value *RHS,
353                                    const TargetData *TD,
354                                    const TargetLibraryInfo *TLI,
355                                    const DominatorTree *DT,
356                                    unsigned MaxRecurse) {
357  // Recursion is always used, so bail out at once if we already hit the limit.
358  if (!MaxRecurse--)
359    return 0;
360
361  SelectInst *SI;
362  if (isa<SelectInst>(LHS)) {
363    SI = cast<SelectInst>(LHS);
364  } else {
365    assert(isa<SelectInst>(RHS) && "No select instruction operand!");
366    SI = cast<SelectInst>(RHS);
367  }
368
369  // Evaluate the BinOp on the true and false branches of the select.
370  Value *TV;
371  Value *FV;
372  if (SI == LHS) {
373    TV = SimplifyBinOp(Opcode, SI->getTrueValue(), RHS, TD, TLI, DT, MaxRecurse);
374    FV = SimplifyBinOp(Opcode, SI->getFalseValue(), RHS, TD, TLI, DT, MaxRecurse);
375  } else {
376    TV = SimplifyBinOp(Opcode, LHS, SI->getTrueValue(), TD, TLI, DT, MaxRecurse);
377    FV = SimplifyBinOp(Opcode, LHS, SI->getFalseValue(), TD, TLI, DT, MaxRecurse);
378  }
379
380  // If they simplified to the same value, then return the common value.
381  // If they both failed to simplify then return null.
382  if (TV == FV)
383    return TV;
384
385  // If one branch simplified to undef, return the other one.
386  if (TV && isa<UndefValue>(TV))
387    return FV;
388  if (FV && isa<UndefValue>(FV))
389    return TV;
390
391  // If applying the operation did not change the true and false select values,
392  // then the result of the binop is the select itself.
393  if (TV == SI->getTrueValue() && FV == SI->getFalseValue())
394    return SI;
395
396  // If one branch simplified and the other did not, and the simplified
397  // value is equal to the unsimplified one, return the simplified value.
398  // For example, select (cond, X, X & Z) & Z -> X & Z.
399  if ((FV && !TV) || (TV && !FV)) {
400    // Check that the simplified value has the form "X op Y" where "op" is the
401    // same as the original operation.
402    Instruction *Simplified = dyn_cast<Instruction>(FV ? FV : TV);
403    if (Simplified && Simplified->getOpcode() == Opcode) {
404      // The value that didn't simplify is "UnsimplifiedLHS op UnsimplifiedRHS".
405      // We already know that "op" is the same as for the simplified value.  See
406      // if the operands match too.  If so, return the simplified value.
407      Value *UnsimplifiedBranch = FV ? SI->getTrueValue() : SI->getFalseValue();
408      Value *UnsimplifiedLHS = SI == LHS ? UnsimplifiedBranch : LHS;
409      Value *UnsimplifiedRHS = SI == LHS ? RHS : UnsimplifiedBranch;
410      if (Simplified->getOperand(0) == UnsimplifiedLHS &&
411          Simplified->getOperand(1) == UnsimplifiedRHS)
412        return Simplified;
413      if (Simplified->isCommutative() &&
414          Simplified->getOperand(1) == UnsimplifiedLHS &&
415          Simplified->getOperand(0) == UnsimplifiedRHS)
416        return Simplified;
417    }
418  }
419
420  return 0;
421}
422
423/// ThreadCmpOverSelect - In the case of a comparison with a select instruction,
424/// try to simplify the comparison by seeing whether both branches of the select
425/// result in the same value.  Returns the common value if so, otherwise returns
426/// null.
427static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS,
428                                  Value *RHS, const TargetData *TD,
429                                  const TargetLibraryInfo *TLI,
430                                  const DominatorTree *DT,
431                                  unsigned MaxRecurse) {
432  // Recursion is always used, so bail out at once if we already hit the limit.
433  if (!MaxRecurse--)
434    return 0;
435
436  // Make sure the select is on the LHS.
437  if (!isa<SelectInst>(LHS)) {
438    std::swap(LHS, RHS);
439    Pred = CmpInst::getSwappedPredicate(Pred);
440  }
441  assert(isa<SelectInst>(LHS) && "Not comparing with a select instruction!");
442  SelectInst *SI = cast<SelectInst>(LHS);
443  Value *Cond = SI->getCondition();
444  Value *TV = SI->getTrueValue();
445  Value *FV = SI->getFalseValue();
446
447  // Now that we have "cmp select(Cond, TV, FV), RHS", analyse it.
448  // Does "cmp TV, RHS" simplify?
449  Value *TCmp = SimplifyCmpInst(Pred, TV, RHS, TD, TLI, DT, MaxRecurse);
450  if (TCmp == Cond) {
451    // It not only simplified, it simplified to the select condition.  Replace
452    // it with 'true'.
453    TCmp = getTrue(Cond->getType());
454  } else if (!TCmp) {
455    // It didn't simplify.  However if "cmp TV, RHS" is equal to the select
456    // condition then we can replace it with 'true'.  Otherwise give up.
457    if (!isSameCompare(Cond, Pred, TV, RHS))
458      return 0;
459    TCmp = getTrue(Cond->getType());
460  }
461
462  // Does "cmp FV, RHS" simplify?
463  Value *FCmp = SimplifyCmpInst(Pred, FV, RHS, TD, TLI, DT, MaxRecurse);
464  if (FCmp == Cond) {
465    // It not only simplified, it simplified to the select condition.  Replace
466    // it with 'false'.
467    FCmp = getFalse(Cond->getType());
468  } else if (!FCmp) {
469    // It didn't simplify.  However if "cmp FV, RHS" is equal to the select
470    // condition then we can replace it with 'false'.  Otherwise give up.
471    if (!isSameCompare(Cond, Pred, FV, RHS))
472      return 0;
473    FCmp = getFalse(Cond->getType());
474  }
475
476  // If both sides simplified to the same value, then use it as the result of
477  // the original comparison.
478  if (TCmp == FCmp)
479    return TCmp;
480
481  // The remaining cases only make sense if the select condition has the same
482  // type as the result of the comparison, so bail out if this is not so.
483  if (Cond->getType()->isVectorTy() != RHS->getType()->isVectorTy())
484    return 0;
485  // If the false value simplified to false, then the result of the compare
486  // is equal to "Cond && TCmp".  This also catches the case when the false
487  // value simplified to false and the true value to true, returning "Cond".
488  if (match(FCmp, m_Zero()))
489    if (Value *V = SimplifyAndInst(Cond, TCmp, TD, TLI, DT, MaxRecurse))
490      return V;
491  // If the true value simplified to true, then the result of the compare
492  // is equal to "Cond || FCmp".
493  if (match(TCmp, m_One()))
494    if (Value *V = SimplifyOrInst(Cond, FCmp, TD, TLI, DT, MaxRecurse))
495      return V;
496  // Finally, if the false value simplified to true and the true value to
497  // false, then the result of the compare is equal to "!Cond".
498  if (match(FCmp, m_One()) && match(TCmp, m_Zero()))
499    if (Value *V =
500        SimplifyXorInst(Cond, Constant::getAllOnesValue(Cond->getType()),
501                        TD, TLI, DT, MaxRecurse))
502      return V;
503
504  return 0;
505}
506
507/// ThreadBinOpOverPHI - In the case of a binary operation with an operand that
508/// is a PHI instruction, try to simplify the binop by seeing whether evaluating
509/// it on the incoming phi values yields the same result for every value.  If so
510/// returns the common value, otherwise returns null.
511static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS,
512                                 const TargetData *TD,
513                                 const TargetLibraryInfo *TLI,
514                                 const DominatorTree *DT,
515                                 unsigned MaxRecurse) {
516  // Recursion is always used, so bail out at once if we already hit the limit.
517  if (!MaxRecurse--)
518    return 0;
519
520  PHINode *PI;
521  if (isa<PHINode>(LHS)) {
522    PI = cast<PHINode>(LHS);
523    // Bail out if RHS and the phi may be mutually interdependent due to a loop.
524    if (!ValueDominatesPHI(RHS, PI, DT))
525      return 0;
526  } else {
527    assert(isa<PHINode>(RHS) && "No PHI instruction operand!");
528    PI = cast<PHINode>(RHS);
529    // Bail out if LHS and the phi may be mutually interdependent due to a loop.
530    if (!ValueDominatesPHI(LHS, PI, DT))
531      return 0;
532  }
533
534  // Evaluate the BinOp on the incoming phi values.
535  Value *CommonValue = 0;
536  for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
537    Value *Incoming = PI->getIncomingValue(i);
538    // If the incoming value is the phi node itself, it can safely be skipped.
539    if (Incoming == PI) continue;
540    Value *V = PI == LHS ?
541      SimplifyBinOp(Opcode, Incoming, RHS, TD, TLI, DT, MaxRecurse) :
542      SimplifyBinOp(Opcode, LHS, Incoming, TD, TLI, DT, MaxRecurse);
543    // If the operation failed to simplify, or simplified to a different value
544    // to previously, then give up.
545    if (!V || (CommonValue && V != CommonValue))
546      return 0;
547    CommonValue = V;
548  }
549
550  return CommonValue;
551}
552
553/// ThreadCmpOverPHI - In the case of a comparison with a PHI instruction, try
554/// try to simplify the comparison by seeing whether comparing with all of the
555/// incoming phi values yields the same result every time.  If so returns the
556/// common result, otherwise returns null.
557static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS,
558                               const TargetData *TD,
559                               const TargetLibraryInfo *TLI,
560                               const DominatorTree *DT,
561                               unsigned MaxRecurse) {
562  // Recursion is always used, so bail out at once if we already hit the limit.
563  if (!MaxRecurse--)
564    return 0;
565
566  // Make sure the phi is on the LHS.
567  if (!isa<PHINode>(LHS)) {
568    std::swap(LHS, RHS);
569    Pred = CmpInst::getSwappedPredicate(Pred);
570  }
571  assert(isa<PHINode>(LHS) && "Not comparing with a phi instruction!");
572  PHINode *PI = cast<PHINode>(LHS);
573
574  // Bail out if RHS and the phi may be mutually interdependent due to a loop.
575  if (!ValueDominatesPHI(RHS, PI, DT))
576    return 0;
577
578  // Evaluate the BinOp on the incoming phi values.
579  Value *CommonValue = 0;
580  for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
581    Value *Incoming = PI->getIncomingValue(i);
582    // If the incoming value is the phi node itself, it can safely be skipped.
583    if (Incoming == PI) continue;
584    Value *V = SimplifyCmpInst(Pred, Incoming, RHS, TD, TLI, DT, MaxRecurse);
585    // If the operation failed to simplify, or simplified to a different value
586    // to previously, then give up.
587    if (!V || (CommonValue && V != CommonValue))
588      return 0;
589    CommonValue = V;
590  }
591
592  return CommonValue;
593}
594
595/// SimplifyAddInst - Given operands for an Add, see if we can
596/// fold the result.  If not, this returns null.
597static Value *SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
598                              const TargetData *TD,
599                              const TargetLibraryInfo *TLI,
600                              const DominatorTree *DT,
601                              unsigned MaxRecurse) {
602  if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
603    if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
604      Constant *Ops[] = { CLHS, CRHS };
605      return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(),
606                                      Ops, TD, TLI);
607    }
608
609    // Canonicalize the constant to the RHS.
610    std::swap(Op0, Op1);
611  }
612
613  // X + undef -> undef
614  if (match(Op1, m_Undef()))
615    return Op1;
616
617  // X + 0 -> X
618  if (match(Op1, m_Zero()))
619    return Op0;
620
621  // X + (Y - X) -> Y
622  // (Y - X) + X -> Y
623  // Eg: X + -X -> 0
624  Value *Y = 0;
625  if (match(Op1, m_Sub(m_Value(Y), m_Specific(Op0))) ||
626      match(Op0, m_Sub(m_Value(Y), m_Specific(Op1))))
627    return Y;
628
629  // X + ~X -> -1   since   ~X = -X-1
630  if (match(Op0, m_Not(m_Specific(Op1))) ||
631      match(Op1, m_Not(m_Specific(Op0))))
632    return Constant::getAllOnesValue(Op0->getType());
633
634  /// i1 add -> xor.
635  if (MaxRecurse && Op0->getType()->isIntegerTy(1))
636    if (Value *V = SimplifyXorInst(Op0, Op1, TD, TLI, DT, MaxRecurse-1))
637      return V;
638
639  // Try some generic simplifications for associative operations.
640  if (Value *V = SimplifyAssociativeBinOp(Instruction::Add, Op0, Op1, TD, TLI, DT,
641                                          MaxRecurse))
642    return V;
643
644  // Mul distributes over Add.  Try some generic simplifications based on this.
645  if (Value *V = FactorizeBinOp(Instruction::Add, Op0, Op1, Instruction::Mul,
646                                TD, TLI, DT, MaxRecurse))
647    return V;
648
649  // Threading Add over selects and phi nodes is pointless, so don't bother.
650  // Threading over the select in "A + select(cond, B, C)" means evaluating
651  // "A+B" and "A+C" and seeing if they are equal; but they are equal if and
652  // only if B and C are equal.  If B and C are equal then (since we assume
653  // that operands have already been simplified) "select(cond, B, C)" should
654  // have been simplified to the common value of B and C already.  Analysing
655  // "A+B" and "A+C" thus gains nothing, but costs compile time.  Similarly
656  // for threading over phi nodes.
657
658  return 0;
659}
660
661Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
662                             const TargetData *TD, const TargetLibraryInfo *TLI,
663                             const DominatorTree *DT) {
664  return ::SimplifyAddInst(Op0, Op1, isNSW, isNUW, TD, TLI, DT, RecursionLimit);
665}
666
667/// SimplifySubInst - Given operands for a Sub, see if we can
668/// fold the result.  If not, this returns null.
669static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
670                              const TargetData *TD,
671                              const TargetLibraryInfo *TLI,
672                              const DominatorTree *DT,
673                              unsigned MaxRecurse) {
674  if (Constant *CLHS = dyn_cast<Constant>(Op0))
675    if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
676      Constant *Ops[] = { CLHS, CRHS };
677      return ConstantFoldInstOperands(Instruction::Sub, CLHS->getType(),
678                                      Ops, TD, TLI);
679    }
680
681  // X - undef -> undef
682  // undef - X -> undef
683  if (match(Op0, m_Undef()) || match(Op1, m_Undef()))
684    return UndefValue::get(Op0->getType());
685
686  // X - 0 -> X
687  if (match(Op1, m_Zero()))
688    return Op0;
689
690  // X - X -> 0
691  if (Op0 == Op1)
692    return Constant::getNullValue(Op0->getType());
693
694  // (X*2) - X -> X
695  // (X<<1) - X -> X
696  Value *X = 0;
697  if (match(Op0, m_Mul(m_Specific(Op1), m_ConstantInt<2>())) ||
698      match(Op0, m_Shl(m_Specific(Op1), m_One())))
699    return Op1;
700
701  // (X + Y) - Z -> X + (Y - Z) or Y + (X - Z) if everything simplifies.
702  // For example, (X + Y) - Y -> X; (Y + X) - Y -> X
703  Value *Y = 0, *Z = Op1;
704  if (MaxRecurse && match(Op0, m_Add(m_Value(X), m_Value(Y)))) { // (X + Y) - Z
705    // See if "V === Y - Z" simplifies.
706    if (Value *V = SimplifyBinOp(Instruction::Sub, Y, Z, TD, TLI, DT, MaxRecurse-1))
707      // It does!  Now see if "X + V" simplifies.
708      if (Value *W = SimplifyBinOp(Instruction::Add, X, V, TD, TLI, DT,
709                                   MaxRecurse-1)) {
710        // It does, we successfully reassociated!
711        ++NumReassoc;
712        return W;
713      }
714    // See if "V === X - Z" simplifies.
715    if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, TD, TLI, DT, MaxRecurse-1))
716      // It does!  Now see if "Y + V" simplifies.
717      if (Value *W = SimplifyBinOp(Instruction::Add, Y, V, TD, TLI, DT,
718                                   MaxRecurse-1)) {
719        // It does, we successfully reassociated!
720        ++NumReassoc;
721        return W;
722      }
723  }
724
725  // X - (Y + Z) -> (X - Y) - Z or (X - Z) - Y if everything simplifies.
726  // For example, X - (X + 1) -> -1
727  X = Op0;
728  if (MaxRecurse && match(Op1, m_Add(m_Value(Y), m_Value(Z)))) { // X - (Y + Z)
729    // See if "V === X - Y" simplifies.
730    if (Value *V = SimplifyBinOp(Instruction::Sub, X, Y, TD, TLI, DT, MaxRecurse-1))
731      // It does!  Now see if "V - Z" simplifies.
732      if (Value *W = SimplifyBinOp(Instruction::Sub, V, Z, TD, TLI, DT,
733                                   MaxRecurse-1)) {
734        // It does, we successfully reassociated!
735        ++NumReassoc;
736        return W;
737      }
738    // See if "V === X - Z" simplifies.
739    if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, TD, TLI, DT, MaxRecurse-1))
740      // It does!  Now see if "V - Y" simplifies.
741      if (Value *W = SimplifyBinOp(Instruction::Sub, V, Y, TD, TLI, DT,
742                                   MaxRecurse-1)) {
743        // It does, we successfully reassociated!
744        ++NumReassoc;
745        return W;
746      }
747  }
748
749  // Z - (X - Y) -> (Z - X) + Y if everything simplifies.
750  // For example, X - (X - Y) -> Y.
751  Z = Op0;
752  if (MaxRecurse && match(Op1, m_Sub(m_Value(X), m_Value(Y)))) // Z - (X - Y)
753    // See if "V === Z - X" simplifies.
754    if (Value *V = SimplifyBinOp(Instruction::Sub, Z, X, TD, TLI, DT, MaxRecurse-1))
755      // It does!  Now see if "V + Y" simplifies.
756      if (Value *W = SimplifyBinOp(Instruction::Add, V, Y, TD, TLI, DT,
757                                   MaxRecurse-1)) {
758        // It does, we successfully reassociated!
759        ++NumReassoc;
760        return W;
761      }
762
763  // Mul distributes over Sub.  Try some generic simplifications based on this.
764  if (Value *V = FactorizeBinOp(Instruction::Sub, Op0, Op1, Instruction::Mul,
765                                TD, TLI, DT, MaxRecurse))
766    return V;
767
768  // i1 sub -> xor.
769  if (MaxRecurse && Op0->getType()->isIntegerTy(1))
770    if (Value *V = SimplifyXorInst(Op0, Op1, TD, TLI, DT, MaxRecurse-1))
771      return V;
772
773  // Threading Sub over selects and phi nodes is pointless, so don't bother.
774  // Threading over the select in "A - select(cond, B, C)" means evaluating
775  // "A-B" and "A-C" and seeing if they are equal; but they are equal if and
776  // only if B and C are equal.  If B and C are equal then (since we assume
777  // that operands have already been simplified) "select(cond, B, C)" should
778  // have been simplified to the common value of B and C already.  Analysing
779  // "A-B" and "A-C" thus gains nothing, but costs compile time.  Similarly
780  // for threading over phi nodes.
781
782  return 0;
783}
784
785Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
786                             const TargetData *TD,
787                             const TargetLibraryInfo *TLI,
788                             const DominatorTree *DT) {
789  return ::SimplifySubInst(Op0, Op1, isNSW, isNUW, TD, TLI, DT, RecursionLimit);
790}
791
792/// SimplifyMulInst - Given operands for a Mul, see if we can
793/// fold the result.  If not, this returns null.
794static Value *SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
795                              const TargetLibraryInfo *TLI,
796                              const DominatorTree *DT, unsigned MaxRecurse) {
797  if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
798    if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
799      Constant *Ops[] = { CLHS, CRHS };
800      return ConstantFoldInstOperands(Instruction::Mul, CLHS->getType(),
801                                      Ops, TD, TLI);
802    }
803
804    // Canonicalize the constant to the RHS.
805    std::swap(Op0, Op1);
806  }
807
808  // X * undef -> 0
809  if (match(Op1, m_Undef()))
810    return Constant::getNullValue(Op0->getType());
811
812  // X * 0 -> 0
813  if (match(Op1, m_Zero()))
814    return Op1;
815
816  // X * 1 -> X
817  if (match(Op1, m_One()))
818    return Op0;
819
820  // (X / Y) * Y -> X if the division is exact.
821  Value *X = 0;
822  if (match(Op0, m_Exact(m_IDiv(m_Value(X), m_Specific(Op1)))) || // (X / Y) * Y
823      match(Op1, m_Exact(m_IDiv(m_Value(X), m_Specific(Op0)))))   // Y * (X / Y)
824    return X;
825
826  // i1 mul -> and.
827  if (MaxRecurse && Op0->getType()->isIntegerTy(1))
828    if (Value *V = SimplifyAndInst(Op0, Op1, TD, TLI, DT, MaxRecurse-1))
829      return V;
830
831  // Try some generic simplifications for associative operations.
832  if (Value *V = SimplifyAssociativeBinOp(Instruction::Mul, Op0, Op1, TD, TLI, DT,
833                                          MaxRecurse))
834    return V;
835
836  // Mul distributes over Add.  Try some generic simplifications based on this.
837  if (Value *V = ExpandBinOp(Instruction::Mul, Op0, Op1, Instruction::Add,
838                             TD, TLI, DT, MaxRecurse))
839    return V;
840
841  // If the operation is with the result of a select instruction, check whether
842  // operating on either branch of the select always yields the same value.
843  if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
844    if (Value *V = ThreadBinOpOverSelect(Instruction::Mul, Op0, Op1, TD, TLI, DT,
845                                         MaxRecurse))
846      return V;
847
848  // If the operation is with the result of a phi instruction, check whether
849  // operating on all incoming values of the phi always yields the same value.
850  if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
851    if (Value *V = ThreadBinOpOverPHI(Instruction::Mul, Op0, Op1, TD, TLI, DT,
852                                      MaxRecurse))
853      return V;
854
855  return 0;
856}
857
858Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
859                             const TargetLibraryInfo *TLI,
860                             const DominatorTree *DT) {
861  return ::SimplifyMulInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
862}
863
864/// SimplifyDiv - Given operands for an SDiv or UDiv, see if we can
865/// fold the result.  If not, this returns null.
866static Value *SimplifyDiv(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1,
867                          const TargetData *TD, const TargetLibraryInfo *TLI,
868                          const DominatorTree *DT, unsigned MaxRecurse) {
869  if (Constant *C0 = dyn_cast<Constant>(Op0)) {
870    if (Constant *C1 = dyn_cast<Constant>(Op1)) {
871      Constant *Ops[] = { C0, C1 };
872      return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, TD, TLI);
873    }
874  }
875
876  bool isSigned = Opcode == Instruction::SDiv;
877
878  // X / undef -> undef
879  if (match(Op1, m_Undef()))
880    return Op1;
881
882  // undef / X -> 0
883  if (match(Op0, m_Undef()))
884    return Constant::getNullValue(Op0->getType());
885
886  // 0 / X -> 0, we don't need to preserve faults!
887  if (match(Op0, m_Zero()))
888    return Op0;
889
890  // X / 1 -> X
891  if (match(Op1, m_One()))
892    return Op0;
893
894  if (Op0->getType()->isIntegerTy(1))
895    // It can't be division by zero, hence it must be division by one.
896    return Op0;
897
898  // X / X -> 1
899  if (Op0 == Op1)
900    return ConstantInt::get(Op0->getType(), 1);
901
902  // (X * Y) / Y -> X if the multiplication does not overflow.
903  Value *X = 0, *Y = 0;
904  if (match(Op0, m_Mul(m_Value(X), m_Value(Y))) && (X == Op1 || Y == Op1)) {
905    if (Y != Op1) std::swap(X, Y); // Ensure expression is (X * Y) / Y, Y = Op1
906    OverflowingBinaryOperator *Mul = cast<OverflowingBinaryOperator>(Op0);
907    // If the Mul knows it does not overflow, then we are good to go.
908    if ((isSigned && Mul->hasNoSignedWrap()) ||
909        (!isSigned && Mul->hasNoUnsignedWrap()))
910      return X;
911    // If X has the form X = A / Y then X * Y cannot overflow.
912    if (BinaryOperator *Div = dyn_cast<BinaryOperator>(X))
913      if (Div->getOpcode() == Opcode && Div->getOperand(1) == Y)
914        return X;
915  }
916
917  // (X rem Y) / Y -> 0
918  if ((isSigned && match(Op0, m_SRem(m_Value(), m_Specific(Op1)))) ||
919      (!isSigned && match(Op0, m_URem(m_Value(), m_Specific(Op1)))))
920    return Constant::getNullValue(Op0->getType());
921
922  // If the operation is with the result of a select instruction, check whether
923  // operating on either branch of the select always yields the same value.
924  if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
925    if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, TD, TLI, DT,
926                                         MaxRecurse))
927      return V;
928
929  // If the operation is with the result of a phi instruction, check whether
930  // operating on all incoming values of the phi always yields the same value.
931  if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
932    if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, TD, TLI, DT,
933                                      MaxRecurse))
934      return V;
935
936  return 0;
937}
938
939/// SimplifySDivInst - Given operands for an SDiv, see if we can
940/// fold the result.  If not, this returns null.
941static Value *SimplifySDivInst(Value *Op0, Value *Op1, const TargetData *TD,
942                               const TargetLibraryInfo *TLI,
943                               const DominatorTree *DT, unsigned MaxRecurse) {
944  if (Value *V = SimplifyDiv(Instruction::SDiv, Op0, Op1, TD, TLI, DT,
945                             MaxRecurse))
946    return V;
947
948  return 0;
949}
950
951Value *llvm::SimplifySDivInst(Value *Op0, Value *Op1, const TargetData *TD,
952                              const TargetLibraryInfo *TLI,
953                              const DominatorTree *DT) {
954  return ::SimplifySDivInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
955}
956
957/// SimplifyUDivInst - Given operands for a UDiv, see if we can
958/// fold the result.  If not, this returns null.
959static Value *SimplifyUDivInst(Value *Op0, Value *Op1, const TargetData *TD,
960                               const TargetLibraryInfo *TLI,
961                               const DominatorTree *DT, unsigned MaxRecurse) {
962  if (Value *V = SimplifyDiv(Instruction::UDiv, Op0, Op1, TD, TLI, DT,
963                             MaxRecurse))
964    return V;
965
966  return 0;
967}
968
969Value *llvm::SimplifyUDivInst(Value *Op0, Value *Op1, const TargetData *TD,
970                              const TargetLibraryInfo *TLI,
971                              const DominatorTree *DT) {
972  return ::SimplifyUDivInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
973}
974
975static Value *SimplifyFDivInst(Value *Op0, Value *Op1, const TargetData *,
976                               const TargetLibraryInfo *,
977                               const DominatorTree *, unsigned) {
978  // undef / X -> undef    (the undef could be a snan).
979  if (match(Op0, m_Undef()))
980    return Op0;
981
982  // X / undef -> undef
983  if (match(Op1, m_Undef()))
984    return Op1;
985
986  return 0;
987}
988
989Value *llvm::SimplifyFDivInst(Value *Op0, Value *Op1, const TargetData *TD,
990                              const TargetLibraryInfo *TLI,
991                              const DominatorTree *DT) {
992  return ::SimplifyFDivInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
993}
994
995/// SimplifyRem - Given operands for an SRem or URem, see if we can
996/// fold the result.  If not, this returns null.
997static Value *SimplifyRem(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1,
998                          const TargetData *TD, const TargetLibraryInfo *TLI,
999                          const DominatorTree *DT, unsigned MaxRecurse) {
1000  if (Constant *C0 = dyn_cast<Constant>(Op0)) {
1001    if (Constant *C1 = dyn_cast<Constant>(Op1)) {
1002      Constant *Ops[] = { C0, C1 };
1003      return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, TD, TLI);
1004    }
1005  }
1006
1007  // X % undef -> undef
1008  if (match(Op1, m_Undef()))
1009    return Op1;
1010
1011  // undef % X -> 0
1012  if (match(Op0, m_Undef()))
1013    return Constant::getNullValue(Op0->getType());
1014
1015  // 0 % X -> 0, we don't need to preserve faults!
1016  if (match(Op0, m_Zero()))
1017    return Op0;
1018
1019  // X % 0 -> undef, we don't need to preserve faults!
1020  if (match(Op1, m_Zero()))
1021    return UndefValue::get(Op0->getType());
1022
1023  // X % 1 -> 0
1024  if (match(Op1, m_One()))
1025    return Constant::getNullValue(Op0->getType());
1026
1027  if (Op0->getType()->isIntegerTy(1))
1028    // It can't be remainder by zero, hence it must be remainder by one.
1029    return Constant::getNullValue(Op0->getType());
1030
1031  // X % X -> 0
1032  if (Op0 == Op1)
1033    return Constant::getNullValue(Op0->getType());
1034
1035  // If the operation is with the result of a select instruction, check whether
1036  // operating on either branch of the select always yields the same value.
1037  if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
1038    if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, TD, TLI, DT, MaxRecurse))
1039      return V;
1040
1041  // If the operation is with the result of a phi instruction, check whether
1042  // operating on all incoming values of the phi always yields the same value.
1043  if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
1044    if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, TD, TLI, DT, MaxRecurse))
1045      return V;
1046
1047  return 0;
1048}
1049
1050/// SimplifySRemInst - Given operands for an SRem, see if we can
1051/// fold the result.  If not, this returns null.
1052static Value *SimplifySRemInst(Value *Op0, Value *Op1, const TargetData *TD,
1053                               const TargetLibraryInfo *TLI,
1054                               const DominatorTree *DT,
1055                               unsigned MaxRecurse) {
1056  if (Value *V = SimplifyRem(Instruction::SRem, Op0, Op1, TD, TLI, DT, MaxRecurse))
1057    return V;
1058
1059  return 0;
1060}
1061
1062Value *llvm::SimplifySRemInst(Value *Op0, Value *Op1, const TargetData *TD,
1063                              const TargetLibraryInfo *TLI,
1064                              const DominatorTree *DT) {
1065  return ::SimplifySRemInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
1066}
1067
1068/// SimplifyURemInst - Given operands for a URem, see if we can
1069/// fold the result.  If not, this returns null.
1070static Value *SimplifyURemInst(Value *Op0, Value *Op1, const TargetData *TD,
1071                               const TargetLibraryInfo *TLI,
1072                               const DominatorTree *DT,
1073                               unsigned MaxRecurse) {
1074  if (Value *V = SimplifyRem(Instruction::URem, Op0, Op1, TD, TLI, DT, MaxRecurse))
1075    return V;
1076
1077  return 0;
1078}
1079
1080Value *llvm::SimplifyURemInst(Value *Op0, Value *Op1, const TargetData *TD,
1081                              const TargetLibraryInfo *TLI,
1082                              const DominatorTree *DT) {
1083  return ::SimplifyURemInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
1084}
1085
1086static Value *SimplifyFRemInst(Value *Op0, Value *Op1, const TargetData *,
1087                               const TargetLibraryInfo *,
1088                               const DominatorTree *,
1089                               unsigned) {
1090  // undef % X -> undef    (the undef could be a snan).
1091  if (match(Op0, m_Undef()))
1092    return Op0;
1093
1094  // X % undef -> undef
1095  if (match(Op1, m_Undef()))
1096    return Op1;
1097
1098  return 0;
1099}
1100
1101Value *llvm::SimplifyFRemInst(Value *Op0, Value *Op1, const TargetData *TD,
1102                              const TargetLibraryInfo *TLI,
1103                              const DominatorTree *DT) {
1104  return ::SimplifyFRemInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
1105}
1106
1107/// SimplifyShift - Given operands for an Shl, LShr or AShr, see if we can
1108/// fold the result.  If not, this returns null.
1109static Value *SimplifyShift(unsigned Opcode, Value *Op0, Value *Op1,
1110                            const TargetData *TD, const TargetLibraryInfo *TLI,
1111                            const DominatorTree *DT, unsigned MaxRecurse) {
1112  if (Constant *C0 = dyn_cast<Constant>(Op0)) {
1113    if (Constant *C1 = dyn_cast<Constant>(Op1)) {
1114      Constant *Ops[] = { C0, C1 };
1115      return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, TD, TLI);
1116    }
1117  }
1118
1119  // 0 shift by X -> 0
1120  if (match(Op0, m_Zero()))
1121    return Op0;
1122
1123  // X shift by 0 -> X
1124  if (match(Op1, m_Zero()))
1125    return Op0;
1126
1127  // X shift by undef -> undef because it may shift by the bitwidth.
1128  if (match(Op1, m_Undef()))
1129    return Op1;
1130
1131  // Shifting by the bitwidth or more is undefined.
1132  if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1))
1133    if (CI->getValue().getLimitedValue() >=
1134        Op0->getType()->getScalarSizeInBits())
1135      return UndefValue::get(Op0->getType());
1136
1137  // If the operation is with the result of a select instruction, check whether
1138  // operating on either branch of the select always yields the same value.
1139  if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
1140    if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, TD, TLI, DT, MaxRecurse))
1141      return V;
1142
1143  // If the operation is with the result of a phi instruction, check whether
1144  // operating on all incoming values of the phi always yields the same value.
1145  if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
1146    if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, TD, TLI, DT, MaxRecurse))
1147      return V;
1148
1149  return 0;
1150}
1151
1152/// SimplifyShlInst - Given operands for an Shl, see if we can
1153/// fold the result.  If not, this returns null.
1154static Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
1155                              const TargetData *TD,
1156                              const TargetLibraryInfo *TLI,
1157                              const DominatorTree *DT, unsigned MaxRecurse) {
1158  if (Value *V = SimplifyShift(Instruction::Shl, Op0, Op1, TD, TLI, DT, MaxRecurse))
1159    return V;
1160
1161  // undef << X -> 0
1162  if (match(Op0, m_Undef()))
1163    return Constant::getNullValue(Op0->getType());
1164
1165  // (X >> A) << A -> X
1166  Value *X;
1167  if (match(Op0, m_Exact(m_Shr(m_Value(X), m_Specific(Op1)))))
1168    return X;
1169  return 0;
1170}
1171
1172Value *llvm::SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
1173                             const TargetData *TD, const TargetLibraryInfo *TLI,
1174                             const DominatorTree *DT) {
1175  return ::SimplifyShlInst(Op0, Op1, isNSW, isNUW, TD, TLI, DT, RecursionLimit);
1176}
1177
1178/// SimplifyLShrInst - Given operands for an LShr, see if we can
1179/// fold the result.  If not, this returns null.
1180static Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
1181                               const TargetData *TD,
1182                               const TargetLibraryInfo *TLI,
1183                               const DominatorTree *DT,
1184                               unsigned MaxRecurse) {
1185  if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, TD, TLI, DT, MaxRecurse))
1186    return V;
1187
1188  // undef >>l X -> 0
1189  if (match(Op0, m_Undef()))
1190    return Constant::getNullValue(Op0->getType());
1191
1192  // (X << A) >> A -> X
1193  Value *X;
1194  if (match(Op0, m_Shl(m_Value(X), m_Specific(Op1))) &&
1195      cast<OverflowingBinaryOperator>(Op0)->hasNoUnsignedWrap())
1196    return X;
1197
1198  return 0;
1199}
1200
1201Value *llvm::SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact,
1202                              const TargetData *TD,
1203                              const TargetLibraryInfo *TLI,
1204                              const DominatorTree *DT) {
1205  return ::SimplifyLShrInst(Op0, Op1, isExact, TD, TLI, DT, RecursionLimit);
1206}
1207
1208/// SimplifyAShrInst - Given operands for an AShr, see if we can
1209/// fold the result.  If not, this returns null.
1210static Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
1211                               const TargetData *TD,
1212                               const TargetLibraryInfo *TLI,
1213                               const DominatorTree *DT,
1214                               unsigned MaxRecurse) {
1215  if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, TD, TLI, DT, MaxRecurse))
1216    return V;
1217
1218  // all ones >>a X -> all ones
1219  if (match(Op0, m_AllOnes()))
1220    return Op0;
1221
1222  // undef >>a X -> all ones
1223  if (match(Op0, m_Undef()))
1224    return Constant::getAllOnesValue(Op0->getType());
1225
1226  // (X << A) >> A -> X
1227  Value *X;
1228  if (match(Op0, m_Shl(m_Value(X), m_Specific(Op1))) &&
1229      cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap())
1230    return X;
1231
1232  return 0;
1233}
1234
1235Value *llvm::SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact,
1236                              const TargetData *TD,
1237                              const TargetLibraryInfo *TLI,
1238                              const DominatorTree *DT) {
1239  return ::SimplifyAShrInst(Op0, Op1, isExact, TD, TLI, DT, RecursionLimit);
1240}
1241
1242/// SimplifyAndInst - Given operands for an And, see if we can
1243/// fold the result.  If not, this returns null.
1244static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
1245                              const TargetLibraryInfo *TLI,
1246                              const DominatorTree *DT,
1247                              unsigned MaxRecurse) {
1248  if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
1249    if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
1250      Constant *Ops[] = { CLHS, CRHS };
1251      return ConstantFoldInstOperands(Instruction::And, CLHS->getType(),
1252                                      Ops, TD, TLI);
1253    }
1254
1255    // Canonicalize the constant to the RHS.
1256    std::swap(Op0, Op1);
1257  }
1258
1259  // X & undef -> 0
1260  if (match(Op1, m_Undef()))
1261    return Constant::getNullValue(Op0->getType());
1262
1263  // X & X = X
1264  if (Op0 == Op1)
1265    return Op0;
1266
1267  // X & 0 = 0
1268  if (match(Op1, m_Zero()))
1269    return Op1;
1270
1271  // X & -1 = X
1272  if (match(Op1, m_AllOnes()))
1273    return Op0;
1274
1275  // A & ~A  =  ~A & A  =  0
1276  if (match(Op0, m_Not(m_Specific(Op1))) ||
1277      match(Op1, m_Not(m_Specific(Op0))))
1278    return Constant::getNullValue(Op0->getType());
1279
1280  // (A | ?) & A = A
1281  Value *A = 0, *B = 0;
1282  if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
1283      (A == Op1 || B == Op1))
1284    return Op1;
1285
1286  // A & (A | ?) = A
1287  if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
1288      (A == Op0 || B == Op0))
1289    return Op0;
1290
1291  // A & (-A) = A if A is a power of two or zero.
1292  if (match(Op0, m_Neg(m_Specific(Op1))) ||
1293      match(Op1, m_Neg(m_Specific(Op0)))) {
1294    if (isPowerOfTwo(Op0, TD, /*OrZero*/true))
1295      return Op0;
1296    if (isPowerOfTwo(Op1, TD, /*OrZero*/true))
1297      return Op1;
1298  }
1299
1300  // Try some generic simplifications for associative operations.
1301  if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, TD, TLI,
1302                                          DT, MaxRecurse))
1303    return V;
1304
1305  // And distributes over Or.  Try some generic simplifications based on this.
1306  if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Or,
1307                             TD, TLI, DT, MaxRecurse))
1308    return V;
1309
1310  // And distributes over Xor.  Try some generic simplifications based on this.
1311  if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Xor,
1312                             TD, TLI, DT, MaxRecurse))
1313    return V;
1314
1315  // Or distributes over And.  Try some generic simplifications based on this.
1316  if (Value *V = FactorizeBinOp(Instruction::And, Op0, Op1, Instruction::Or,
1317                                TD, TLI, DT, MaxRecurse))
1318    return V;
1319
1320  // If the operation is with the result of a select instruction, check whether
1321  // operating on either branch of the select always yields the same value.
1322  if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
1323    if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, TD, TLI,
1324                                         DT, MaxRecurse))
1325      return V;
1326
1327  // If the operation is with the result of a phi instruction, check whether
1328  // operating on all incoming values of the phi always yields the same value.
1329  if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
1330    if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, TD, TLI, DT,
1331                                      MaxRecurse))
1332      return V;
1333
1334  return 0;
1335}
1336
1337Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
1338                             const TargetLibraryInfo *TLI,
1339                             const DominatorTree *DT) {
1340  return ::SimplifyAndInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
1341}
1342
1343/// SimplifyOrInst - Given operands for an Or, see if we can
1344/// fold the result.  If not, this returns null.
1345static Value *SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
1346                             const TargetLibraryInfo *TLI,
1347                             const DominatorTree *DT, unsigned MaxRecurse) {
1348  if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
1349    if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
1350      Constant *Ops[] = { CLHS, CRHS };
1351      return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(),
1352                                      Ops, TD, TLI);
1353    }
1354
1355    // Canonicalize the constant to the RHS.
1356    std::swap(Op0, Op1);
1357  }
1358
1359  // X | undef -> -1
1360  if (match(Op1, m_Undef()))
1361    return Constant::getAllOnesValue(Op0->getType());
1362
1363  // X | X = X
1364  if (Op0 == Op1)
1365    return Op0;
1366
1367  // X | 0 = X
1368  if (match(Op1, m_Zero()))
1369    return Op0;
1370
1371  // X | -1 = -1
1372  if (match(Op1, m_AllOnes()))
1373    return Op1;
1374
1375  // A | ~A  =  ~A | A  =  -1
1376  if (match(Op0, m_Not(m_Specific(Op1))) ||
1377      match(Op1, m_Not(m_Specific(Op0))))
1378    return Constant::getAllOnesValue(Op0->getType());
1379
1380  // (A & ?) | A = A
1381  Value *A = 0, *B = 0;
1382  if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
1383      (A == Op1 || B == Op1))
1384    return Op1;
1385
1386  // A | (A & ?) = A
1387  if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
1388      (A == Op0 || B == Op0))
1389    return Op0;
1390
1391  // ~(A & ?) | A = -1
1392  if (match(Op0, m_Not(m_And(m_Value(A), m_Value(B)))) &&
1393      (A == Op1 || B == Op1))
1394    return Constant::getAllOnesValue(Op1->getType());
1395
1396  // A | ~(A & ?) = -1
1397  if (match(Op1, m_Not(m_And(m_Value(A), m_Value(B)))) &&
1398      (A == Op0 || B == Op0))
1399    return Constant::getAllOnesValue(Op0->getType());
1400
1401  // Try some generic simplifications for associative operations.
1402  if (Value *V = SimplifyAssociativeBinOp(Instruction::Or, Op0, Op1, TD, TLI,
1403                                          DT, MaxRecurse))
1404    return V;
1405
1406  // Or distributes over And.  Try some generic simplifications based on this.
1407  if (Value *V = ExpandBinOp(Instruction::Or, Op0, Op1, Instruction::And, TD,
1408                             TLI, DT, MaxRecurse))
1409    return V;
1410
1411  // And distributes over Or.  Try some generic simplifications based on this.
1412  if (Value *V = FactorizeBinOp(Instruction::Or, Op0, Op1, Instruction::And,
1413                                TD, TLI, DT, MaxRecurse))
1414    return V;
1415
1416  // If the operation is with the result of a select instruction, check whether
1417  // operating on either branch of the select always yields the same value.
1418  if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
1419    if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, TD, TLI, DT,
1420                                         MaxRecurse))
1421      return V;
1422
1423  // If the operation is with the result of a phi instruction, check whether
1424  // operating on all incoming values of the phi always yields the same value.
1425  if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
1426    if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, TD, TLI, DT,
1427                                      MaxRecurse))
1428      return V;
1429
1430  return 0;
1431}
1432
1433Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
1434                            const TargetLibraryInfo *TLI,
1435                            const DominatorTree *DT) {
1436  return ::SimplifyOrInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
1437}
1438
1439/// SimplifyXorInst - Given operands for a Xor, see if we can
1440/// fold the result.  If not, this returns null.
1441static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
1442                              const TargetLibraryInfo *TLI,
1443                              const DominatorTree *DT, unsigned MaxRecurse) {
1444  if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
1445    if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
1446      Constant *Ops[] = { CLHS, CRHS };
1447      return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(),
1448                                      Ops, TD, TLI);
1449    }
1450
1451    // Canonicalize the constant to the RHS.
1452    std::swap(Op0, Op1);
1453  }
1454
1455  // A ^ undef -> undef
1456  if (match(Op1, m_Undef()))
1457    return Op1;
1458
1459  // A ^ 0 = A
1460  if (match(Op1, m_Zero()))
1461    return Op0;
1462
1463  // A ^ A = 0
1464  if (Op0 == Op1)
1465    return Constant::getNullValue(Op0->getType());
1466
1467  // A ^ ~A  =  ~A ^ A  =  -1
1468  if (match(Op0, m_Not(m_Specific(Op1))) ||
1469      match(Op1, m_Not(m_Specific(Op0))))
1470    return Constant::getAllOnesValue(Op0->getType());
1471
1472  // Try some generic simplifications for associative operations.
1473  if (Value *V = SimplifyAssociativeBinOp(Instruction::Xor, Op0, Op1, TD, TLI,
1474                                          DT, MaxRecurse))
1475    return V;
1476
1477  // And distributes over Xor.  Try some generic simplifications based on this.
1478  if (Value *V = FactorizeBinOp(Instruction::Xor, Op0, Op1, Instruction::And,
1479                                TD, TLI, DT, MaxRecurse))
1480    return V;
1481
1482  // Threading Xor over selects and phi nodes is pointless, so don't bother.
1483  // Threading over the select in "A ^ select(cond, B, C)" means evaluating
1484  // "A^B" and "A^C" and seeing if they are equal; but they are equal if and
1485  // only if B and C are equal.  If B and C are equal then (since we assume
1486  // that operands have already been simplified) "select(cond, B, C)" should
1487  // have been simplified to the common value of B and C already.  Analysing
1488  // "A^B" and "A^C" thus gains nothing, but costs compile time.  Similarly
1489  // for threading over phi nodes.
1490
1491  return 0;
1492}
1493
1494Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
1495                             const TargetLibraryInfo *TLI,
1496                             const DominatorTree *DT) {
1497  return ::SimplifyXorInst(Op0, Op1, TD, TLI, DT, RecursionLimit);
1498}
1499
1500static Type *GetCompareTy(Value *Op) {
1501  return CmpInst::makeCmpResultType(Op->getType());
1502}
1503
1504/// ExtractEquivalentCondition - Rummage around inside V looking for something
1505/// equivalent to the comparison "LHS Pred RHS".  Return such a value if found,
1506/// otherwise return null.  Helper function for analyzing max/min idioms.
1507static Value *ExtractEquivalentCondition(Value *V, CmpInst::Predicate Pred,
1508                                         Value *LHS, Value *RHS) {
1509  SelectInst *SI = dyn_cast<SelectInst>(V);
1510  if (!SI)
1511    return 0;
1512  CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition());
1513  if (!Cmp)
1514    return 0;
1515  Value *CmpLHS = Cmp->getOperand(0), *CmpRHS = Cmp->getOperand(1);
1516  if (Pred == Cmp->getPredicate() && LHS == CmpLHS && RHS == CmpRHS)
1517    return Cmp;
1518  if (Pred == CmpInst::getSwappedPredicate(Cmp->getPredicate()) &&
1519      LHS == CmpRHS && RHS == CmpLHS)
1520    return Cmp;
1521  return 0;
1522}
1523
1524/// stripPointerAdjustments - This is like Value::stripPointerCasts, but also
1525/// removes inbounds gep operations, regardless of their indices.
1526static Value *stripPointerAdjustmentsImpl(Value *V,
1527                                    SmallPtrSet<GEPOperator*, 8> &VisitedGEPs) {
1528  GEPOperator *GEP = dyn_cast<GEPOperator>(V);
1529  if (GEP == 0 || !GEP->isInBounds())
1530    return V;
1531
1532  // If we've already seen this GEP, we will end up infinitely looping.  This
1533  // can happen in unreachable code.
1534  if (!VisitedGEPs.insert(GEP))
1535    return V;
1536
1537  return stripPointerAdjustmentsImpl(GEP->getOperand(0)->stripPointerCasts(),
1538                                     VisitedGEPs);
1539}
1540
1541static Value *stripPointerAdjustments(Value *V) {
1542  SmallPtrSet<GEPOperator*, 8> VisitedGEPs;
1543  return stripPointerAdjustmentsImpl(V, VisitedGEPs);
1544}
1545
1546
1547/// SimplifyICmpInst - Given operands for an ICmpInst, see if we can
1548/// fold the result.  If not, this returns null.
1549static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1550                               const TargetData *TD,
1551                               const TargetLibraryInfo *TLI,
1552                               const DominatorTree *DT,
1553                               unsigned MaxRecurse) {
1554  CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
1555  assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!");
1556
1557  if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
1558    if (Constant *CRHS = dyn_cast<Constant>(RHS))
1559      return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD, TLI);
1560
1561    // If we have a constant, make sure it is on the RHS.
1562    std::swap(LHS, RHS);
1563    Pred = CmpInst::getSwappedPredicate(Pred);
1564  }
1565
1566  Type *ITy = GetCompareTy(LHS); // The return type.
1567  Type *OpTy = LHS->getType();   // The operand type.
1568
1569  // icmp X, X -> true/false
1570  // X icmp undef -> true/false.  For example, icmp ugt %X, undef -> false
1571  // because X could be 0.
1572  if (LHS == RHS || isa<UndefValue>(RHS))
1573    return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred));
1574
1575  // Special case logic when the operands have i1 type.
1576  if (OpTy->getScalarType()->isIntegerTy(1)) {
1577    switch (Pred) {
1578    default: break;
1579    case ICmpInst::ICMP_EQ:
1580      // X == 1 -> X
1581      if (match(RHS, m_One()))
1582        return LHS;
1583      break;
1584    case ICmpInst::ICMP_NE:
1585      // X != 0 -> X
1586      if (match(RHS, m_Zero()))
1587        return LHS;
1588      break;
1589    case ICmpInst::ICMP_UGT:
1590      // X >u 0 -> X
1591      if (match(RHS, m_Zero()))
1592        return LHS;
1593      break;
1594    case ICmpInst::ICMP_UGE:
1595      // X >=u 1 -> X
1596      if (match(RHS, m_One()))
1597        return LHS;
1598      break;
1599    case ICmpInst::ICMP_SLT:
1600      // X <s 0 -> X
1601      if (match(RHS, m_Zero()))
1602        return LHS;
1603      break;
1604    case ICmpInst::ICMP_SLE:
1605      // X <=s -1 -> X
1606      if (match(RHS, m_One()))
1607        return LHS;
1608      break;
1609    }
1610  }
1611
1612  // icmp <object*>, <object*/null> - Different identified objects have
1613  // different addresses, and what's more the address of a stack variable is
1614  // never equal to another argument.  Note that generalizing to the case where
1615  // LHS is a global variable address or null is pointless, since if both LHS
1616  // and RHS are constants then we already constant folded the compare, and if
1617  // only one of them is then we moved it to RHS already.
1618  Value *LHSPtr = LHS->stripPointerCasts();
1619  Value *RHSPtr = RHS->stripPointerCasts();
1620  if (LHSPtr == RHSPtr)
1621    return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred));
1622
1623  // Be more aggressive about stripping pointer adjustments when checking a
1624  // comparison of an alloca address to another object.  We can rip off all
1625  // inbounds GEP operations, even if they are variable.
1626  LHSPtr = stripPointerAdjustments(LHSPtr);
1627  if (llvm::isIdentifiedObject(LHSPtr)) {
1628    RHSPtr = stripPointerAdjustments(RHSPtr);
1629    if (llvm::isKnownNonNull(LHSPtr) || llvm::isKnownNonNull(RHSPtr)) {
1630      // If both sides are different identified objects, they aren't equal
1631      // unless they're null.
1632      if (LHSPtr != RHSPtr && llvm::isIdentifiedObject(RHSPtr))
1633        return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
1634
1635      // A local identified object (alloca or noalias call) can't equal any
1636      // incoming argument, unless they're both null.
1637      if ((isa<Instruction>(LHSPtr) && isa<Argument>(RHSPtr)) ||
1638          (isa<Instruction>(RHSPtr) && isa<Argument>(LHSPtr)))
1639        return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
1640    }
1641
1642    // Assume that the constant null is on the right.
1643    if (llvm::isKnownNonNull(LHSPtr) && isa<ConstantPointerNull>(RHSPtr))
1644      return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
1645  }
1646
1647  // If we are comparing with zero then try hard since this is a common case.
1648  if (match(RHS, m_Zero())) {
1649    bool LHSKnownNonNegative, LHSKnownNegative;
1650    switch (Pred) {
1651    default: llvm_unreachable("Unknown ICmp predicate!");
1652    case ICmpInst::ICMP_ULT:
1653      return getFalse(ITy);
1654    case ICmpInst::ICMP_UGE:
1655      return getTrue(ITy);
1656    case ICmpInst::ICMP_EQ:
1657    case ICmpInst::ICMP_ULE:
1658      if (isKnownNonZero(LHS, TD))
1659        return getFalse(ITy);
1660      break;
1661    case ICmpInst::ICMP_NE:
1662    case ICmpInst::ICMP_UGT:
1663      if (isKnownNonZero(LHS, TD))
1664        return getTrue(ITy);
1665      break;
1666    case ICmpInst::ICMP_SLT:
1667      ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, TD);
1668      if (LHSKnownNegative)
1669        return getTrue(ITy);
1670      if (LHSKnownNonNegative)
1671        return getFalse(ITy);
1672      break;
1673    case ICmpInst::ICMP_SLE:
1674      ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, TD);
1675      if (LHSKnownNegative)
1676        return getTrue(ITy);
1677      if (LHSKnownNonNegative && isKnownNonZero(LHS, TD))
1678        return getFalse(ITy);
1679      break;
1680    case ICmpInst::ICMP_SGE:
1681      ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, TD);
1682      if (LHSKnownNegative)
1683        return getFalse(ITy);
1684      if (LHSKnownNonNegative)
1685        return getTrue(ITy);
1686      break;
1687    case ICmpInst::ICMP_SGT:
1688      ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, TD);
1689      if (LHSKnownNegative)
1690        return getFalse(ITy);
1691      if (LHSKnownNonNegative && isKnownNonZero(LHS, TD))
1692        return getTrue(ITy);
1693      break;
1694    }
1695  }
1696
1697  // See if we are doing a comparison with a constant integer.
1698  if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
1699    // Rule out tautological comparisons (eg., ult 0 or uge 0).
1700    ConstantRange RHS_CR = ICmpInst::makeConstantRange(Pred, CI->getValue());
1701    if (RHS_CR.isEmptySet())
1702      return ConstantInt::getFalse(CI->getContext());
1703    if (RHS_CR.isFullSet())
1704      return ConstantInt::getTrue(CI->getContext());
1705
1706    // Many binary operators with constant RHS have easy to compute constant
1707    // range.  Use them to check whether the comparison is a tautology.
1708    uint32_t Width = CI->getBitWidth();
1709    APInt Lower = APInt(Width, 0);
1710    APInt Upper = APInt(Width, 0);
1711    ConstantInt *CI2;
1712    if (match(LHS, m_URem(m_Value(), m_ConstantInt(CI2)))) {
1713      // 'urem x, CI2' produces [0, CI2).
1714      Upper = CI2->getValue();
1715    } else if (match(LHS, m_SRem(m_Value(), m_ConstantInt(CI2)))) {
1716      // 'srem x, CI2' produces (-|CI2|, |CI2|).
1717      Upper = CI2->getValue().abs();
1718      Lower = (-Upper) + 1;
1719    } else if (match(LHS, m_UDiv(m_ConstantInt(CI2), m_Value()))) {
1720      // 'udiv CI2, x' produces [0, CI2].
1721      Upper = CI2->getValue() + 1;
1722    } else if (match(LHS, m_UDiv(m_Value(), m_ConstantInt(CI2)))) {
1723      // 'udiv x, CI2' produces [0, UINT_MAX / CI2].
1724      APInt NegOne = APInt::getAllOnesValue(Width);
1725      if (!CI2->isZero())
1726        Upper = NegOne.udiv(CI2->getValue()) + 1;
1727    } else if (match(LHS, m_SDiv(m_Value(), m_ConstantInt(CI2)))) {
1728      // 'sdiv x, CI2' produces [INT_MIN / CI2, INT_MAX / CI2].
1729      APInt IntMin = APInt::getSignedMinValue(Width);
1730      APInt IntMax = APInt::getSignedMaxValue(Width);
1731      APInt Val = CI2->getValue().abs();
1732      if (!Val.isMinValue()) {
1733        Lower = IntMin.sdiv(Val);
1734        Upper = IntMax.sdiv(Val) + 1;
1735      }
1736    } else if (match(LHS, m_LShr(m_Value(), m_ConstantInt(CI2)))) {
1737      // 'lshr x, CI2' produces [0, UINT_MAX >> CI2].
1738      APInt NegOne = APInt::getAllOnesValue(Width);
1739      if (CI2->getValue().ult(Width))
1740        Upper = NegOne.lshr(CI2->getValue()) + 1;
1741    } else if (match(LHS, m_AShr(m_Value(), m_ConstantInt(CI2)))) {
1742      // 'ashr x, CI2' produces [INT_MIN >> CI2, INT_MAX >> CI2].
1743      APInt IntMin = APInt::getSignedMinValue(Width);
1744      APInt IntMax = APInt::getSignedMaxValue(Width);
1745      if (CI2->getValue().ult(Width)) {
1746        Lower = IntMin.ashr(CI2->getValue());
1747        Upper = IntMax.ashr(CI2->getValue()) + 1;
1748      }
1749    } else if (match(LHS, m_Or(m_Value(), m_ConstantInt(CI2)))) {
1750      // 'or x, CI2' produces [CI2, UINT_MAX].
1751      Lower = CI2->getValue();
1752    } else if (match(LHS, m_And(m_Value(), m_ConstantInt(CI2)))) {
1753      // 'and x, CI2' produces [0, CI2].
1754      Upper = CI2->getValue() + 1;
1755    }
1756    if (Lower != Upper) {
1757      ConstantRange LHS_CR = ConstantRange(Lower, Upper);
1758      if (RHS_CR.contains(LHS_CR))
1759        return ConstantInt::getTrue(RHS->getContext());
1760      if (RHS_CR.inverse().contains(LHS_CR))
1761        return ConstantInt::getFalse(RHS->getContext());
1762    }
1763  }
1764
1765  // Compare of cast, for example (zext X) != 0 -> X != 0
1766  if (isa<CastInst>(LHS) && (isa<Constant>(RHS) || isa<CastInst>(RHS))) {
1767    Instruction *LI = cast<CastInst>(LHS);
1768    Value *SrcOp = LI->getOperand(0);
1769    Type *SrcTy = SrcOp->getType();
1770    Type *DstTy = LI->getType();
1771
1772    // Turn icmp (ptrtoint x), (ptrtoint/constant) into a compare of the input
1773    // if the integer type is the same size as the pointer type.
1774    if (MaxRecurse && TD && isa<PtrToIntInst>(LI) &&
1775        TD->getPointerSizeInBits() == DstTy->getPrimitiveSizeInBits()) {
1776      if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
1777        // Transfer the cast to the constant.
1778        if (Value *V = SimplifyICmpInst(Pred, SrcOp,
1779                                        ConstantExpr::getIntToPtr(RHSC, SrcTy),
1780                                        TD, TLI, DT, MaxRecurse-1))
1781          return V;
1782      } else if (PtrToIntInst *RI = dyn_cast<PtrToIntInst>(RHS)) {
1783        if (RI->getOperand(0)->getType() == SrcTy)
1784          // Compare without the cast.
1785          if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0),
1786                                          TD, TLI, DT, MaxRecurse-1))
1787            return V;
1788      }
1789    }
1790
1791    if (isa<ZExtInst>(LHS)) {
1792      // Turn icmp (zext X), (zext Y) into a compare of X and Y if they have the
1793      // same type.
1794      if (ZExtInst *RI = dyn_cast<ZExtInst>(RHS)) {
1795        if (MaxRecurse && SrcTy == RI->getOperand(0)->getType())
1796          // Compare X and Y.  Note that signed predicates become unsigned.
1797          if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred),
1798                                          SrcOp, RI->getOperand(0), TD, TLI, DT,
1799                                          MaxRecurse-1))
1800            return V;
1801      }
1802      // Turn icmp (zext X), Cst into a compare of X and Cst if Cst is extended
1803      // too.  If not, then try to deduce the result of the comparison.
1804      else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
1805        // Compute the constant that would happen if we truncated to SrcTy then
1806        // reextended to DstTy.
1807        Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy);
1808        Constant *RExt = ConstantExpr::getCast(CastInst::ZExt, Trunc, DstTy);
1809
1810        // If the re-extended constant didn't change then this is effectively
1811        // also a case of comparing two zero-extended values.
1812        if (RExt == CI && MaxRecurse)
1813          if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred),
1814                                        SrcOp, Trunc, TD, TLI, DT, MaxRecurse-1))
1815            return V;
1816
1817        // Otherwise the upper bits of LHS are zero while RHS has a non-zero bit
1818        // there.  Use this to work out the result of the comparison.
1819        if (RExt != CI) {
1820          switch (Pred) {
1821          default: llvm_unreachable("Unknown ICmp predicate!");
1822          // LHS <u RHS.
1823          case ICmpInst::ICMP_EQ:
1824          case ICmpInst::ICMP_UGT:
1825          case ICmpInst::ICMP_UGE:
1826            return ConstantInt::getFalse(CI->getContext());
1827
1828          case ICmpInst::ICMP_NE:
1829          case ICmpInst::ICMP_ULT:
1830          case ICmpInst::ICMP_ULE:
1831            return ConstantInt::getTrue(CI->getContext());
1832
1833          // LHS is non-negative.  If RHS is negative then LHS >s LHS.  If RHS
1834          // is non-negative then LHS <s RHS.
1835          case ICmpInst::ICMP_SGT:
1836          case ICmpInst::ICMP_SGE:
1837            return CI->getValue().isNegative() ?
1838              ConstantInt::getTrue(CI->getContext()) :
1839              ConstantInt::getFalse(CI->getContext());
1840
1841          case ICmpInst::ICMP_SLT:
1842          case ICmpInst::ICMP_SLE:
1843            return CI->getValue().isNegative() ?
1844              ConstantInt::getFalse(CI->getContext()) :
1845              ConstantInt::getTrue(CI->getContext());
1846          }
1847        }
1848      }
1849    }
1850
1851    if (isa<SExtInst>(LHS)) {
1852      // Turn icmp (sext X), (sext Y) into a compare of X and Y if they have the
1853      // same type.
1854      if (SExtInst *RI = dyn_cast<SExtInst>(RHS)) {
1855        if (MaxRecurse && SrcTy == RI->getOperand(0)->getType())
1856          // Compare X and Y.  Note that the predicate does not change.
1857          if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0),
1858                                          TD, TLI, DT, MaxRecurse-1))
1859            return V;
1860      }
1861      // Turn icmp (sext X), Cst into a compare of X and Cst if Cst is extended
1862      // too.  If not, then try to deduce the result of the comparison.
1863      else if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
1864        // Compute the constant that would happen if we truncated to SrcTy then
1865        // reextended to DstTy.
1866        Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy);
1867        Constant *RExt = ConstantExpr::getCast(CastInst::SExt, Trunc, DstTy);
1868
1869        // If the re-extended constant didn't change then this is effectively
1870        // also a case of comparing two sign-extended values.
1871        if (RExt == CI && MaxRecurse)
1872          if (Value *V = SimplifyICmpInst(Pred, SrcOp, Trunc, TD, TLI, DT,
1873                                          MaxRecurse-1))
1874            return V;
1875
1876        // Otherwise the upper bits of LHS are all equal, while RHS has varying
1877        // bits there.  Use this to work out the result of the comparison.
1878        if (RExt != CI) {
1879          switch (Pred) {
1880          default: llvm_unreachable("Unknown ICmp predicate!");
1881          case ICmpInst::ICMP_EQ:
1882            return ConstantInt::getFalse(CI->getContext());
1883          case ICmpInst::ICMP_NE:
1884            return ConstantInt::getTrue(CI->getContext());
1885
1886          // If RHS is non-negative then LHS <s RHS.  If RHS is negative then
1887          // LHS >s RHS.
1888          case ICmpInst::ICMP_SGT:
1889          case ICmpInst::ICMP_SGE:
1890            return CI->getValue().isNegative() ?
1891              ConstantInt::getTrue(CI->getContext()) :
1892              ConstantInt::getFalse(CI->getContext());
1893          case ICmpInst::ICMP_SLT:
1894          case ICmpInst::ICMP_SLE:
1895            return CI->getValue().isNegative() ?
1896              ConstantInt::getFalse(CI->getContext()) :
1897              ConstantInt::getTrue(CI->getContext());
1898
1899          // If LHS is non-negative then LHS <u RHS.  If LHS is negative then
1900          // LHS >u RHS.
1901          case ICmpInst::ICMP_UGT:
1902          case ICmpInst::ICMP_UGE:
1903            // Comparison is true iff the LHS <s 0.
1904            if (MaxRecurse)
1905              if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SLT, SrcOp,
1906                                              Constant::getNullValue(SrcTy),
1907                                              TD, TLI, DT, MaxRecurse-1))
1908                return V;
1909            break;
1910          case ICmpInst::ICMP_ULT:
1911          case ICmpInst::ICMP_ULE:
1912            // Comparison is true iff the LHS >=s 0.
1913            if (MaxRecurse)
1914              if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SGE, SrcOp,
1915                                              Constant::getNullValue(SrcTy),
1916                                              TD, TLI, DT, MaxRecurse-1))
1917                return V;
1918            break;
1919          }
1920        }
1921      }
1922    }
1923  }
1924
1925  // Special logic for binary operators.
1926  BinaryOperator *LBO = dyn_cast<BinaryOperator>(LHS);
1927  BinaryOperator *RBO = dyn_cast<BinaryOperator>(RHS);
1928  if (MaxRecurse && (LBO || RBO)) {
1929    // Analyze the case when either LHS or RHS is an add instruction.
1930    Value *A = 0, *B = 0, *C = 0, *D = 0;
1931    // LHS = A + B (or A and B are null); RHS = C + D (or C and D are null).
1932    bool NoLHSWrapProblem = false, NoRHSWrapProblem = false;
1933    if (LBO && LBO->getOpcode() == Instruction::Add) {
1934      A = LBO->getOperand(0); B = LBO->getOperand(1);
1935      NoLHSWrapProblem = ICmpInst::isEquality(Pred) ||
1936        (CmpInst::isUnsigned(Pred) && LBO->hasNoUnsignedWrap()) ||
1937        (CmpInst::isSigned(Pred) && LBO->hasNoSignedWrap());
1938    }
1939    if (RBO && RBO->getOpcode() == Instruction::Add) {
1940      C = RBO->getOperand(0); D = RBO->getOperand(1);
1941      NoRHSWrapProblem = ICmpInst::isEquality(Pred) ||
1942        (CmpInst::isUnsigned(Pred) && RBO->hasNoUnsignedWrap()) ||
1943        (CmpInst::isSigned(Pred) && RBO->hasNoSignedWrap());
1944    }
1945
1946    // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
1947    if ((A == RHS || B == RHS) && NoLHSWrapProblem)
1948      if (Value *V = SimplifyICmpInst(Pred, A == RHS ? B : A,
1949                                      Constant::getNullValue(RHS->getType()),
1950                                      TD, TLI, DT, MaxRecurse-1))
1951        return V;
1952
1953    // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow.
1954    if ((C == LHS || D == LHS) && NoRHSWrapProblem)
1955      if (Value *V = SimplifyICmpInst(Pred,
1956                                      Constant::getNullValue(LHS->getType()),
1957                                      C == LHS ? D : C, TD, TLI, DT, MaxRecurse-1))
1958        return V;
1959
1960    // icmp (X+Y), (X+Z) -> icmp Y,Z for equalities or if there is no overflow.
1961    if (A && C && (A == C || A == D || B == C || B == D) &&
1962        NoLHSWrapProblem && NoRHSWrapProblem) {
1963      // Determine Y and Z in the form icmp (X+Y), (X+Z).
1964      Value *Y = (A == C || A == D) ? B : A;
1965      Value *Z = (C == A || C == B) ? D : C;
1966      if (Value *V = SimplifyICmpInst(Pred, Y, Z, TD, TLI, DT, MaxRecurse-1))
1967        return V;
1968    }
1969  }
1970
1971  if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) {
1972    bool KnownNonNegative, KnownNegative;
1973    switch (Pred) {
1974    default:
1975      break;
1976    case ICmpInst::ICMP_SGT:
1977    case ICmpInst::ICMP_SGE:
1978      ComputeSignBit(LHS, KnownNonNegative, KnownNegative, TD);
1979      if (!KnownNonNegative)
1980        break;
1981      // fall-through
1982    case ICmpInst::ICMP_EQ:
1983    case ICmpInst::ICMP_UGT:
1984    case ICmpInst::ICMP_UGE:
1985      return getFalse(ITy);
1986    case ICmpInst::ICMP_SLT:
1987    case ICmpInst::ICMP_SLE:
1988      ComputeSignBit(LHS, KnownNonNegative, KnownNegative, TD);
1989      if (!KnownNonNegative)
1990        break;
1991      // fall-through
1992    case ICmpInst::ICMP_NE:
1993    case ICmpInst::ICMP_ULT:
1994    case ICmpInst::ICMP_ULE:
1995      return getTrue(ITy);
1996    }
1997  }
1998  if (RBO && match(RBO, m_URem(m_Value(), m_Specific(LHS)))) {
1999    bool KnownNonNegative, KnownNegative;
2000    switch (Pred) {
2001    default:
2002      break;
2003    case ICmpInst::ICMP_SGT:
2004    case ICmpInst::ICMP_SGE:
2005      ComputeSignBit(RHS, KnownNonNegative, KnownNegative, TD);
2006      if (!KnownNonNegative)
2007        break;
2008      // fall-through
2009    case ICmpInst::ICMP_NE:
2010    case ICmpInst::ICMP_UGT:
2011    case ICmpInst::ICMP_UGE:
2012      return getTrue(ITy);
2013    case ICmpInst::ICMP_SLT:
2014    case ICmpInst::ICMP_SLE:
2015      ComputeSignBit(RHS, KnownNonNegative, KnownNegative, TD);
2016      if (!KnownNonNegative)
2017        break;
2018      // fall-through
2019    case ICmpInst::ICMP_EQ:
2020    case ICmpInst::ICMP_ULT:
2021    case ICmpInst::ICMP_ULE:
2022      return getFalse(ITy);
2023    }
2024  }
2025
2026  // x udiv y <=u x.
2027  if (LBO && match(LBO, m_UDiv(m_Specific(RHS), m_Value()))) {
2028    // icmp pred (X /u Y), X
2029    if (Pred == ICmpInst::ICMP_UGT)
2030      return getFalse(ITy);
2031    if (Pred == ICmpInst::ICMP_ULE)
2032      return getTrue(ITy);
2033  }
2034
2035  if (MaxRecurse && LBO && RBO && LBO->getOpcode() == RBO->getOpcode() &&
2036      LBO->getOperand(1) == RBO->getOperand(1)) {
2037    switch (LBO->getOpcode()) {
2038    default: break;
2039    case Instruction::UDiv:
2040    case Instruction::LShr:
2041      if (ICmpInst::isSigned(Pred))
2042        break;
2043      // fall-through
2044    case Instruction::SDiv:
2045    case Instruction::AShr:
2046      if (!LBO->isExact() || !RBO->isExact())
2047        break;
2048      if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0),
2049                                      RBO->getOperand(0), TD, TLI, DT, MaxRecurse-1))
2050        return V;
2051      break;
2052    case Instruction::Shl: {
2053      bool NUW = LBO->hasNoUnsignedWrap() && RBO->hasNoUnsignedWrap();
2054      bool NSW = LBO->hasNoSignedWrap() && RBO->hasNoSignedWrap();
2055      if (!NUW && !NSW)
2056        break;
2057      if (!NSW && ICmpInst::isSigned(Pred))
2058        break;
2059      if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0),
2060                                      RBO->getOperand(0), TD, TLI, DT, MaxRecurse-1))
2061        return V;
2062      break;
2063    }
2064    }
2065  }
2066
2067  // Simplify comparisons involving max/min.
2068  Value *A, *B;
2069  CmpInst::Predicate P = CmpInst::BAD_ICMP_PREDICATE;
2070  CmpInst::Predicate EqP; // Chosen so that "A == max/min(A,B)" iff "A EqP B".
2071
2072  // Signed variants on "max(a,b)>=a -> true".
2073  if (match(LHS, m_SMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) {
2074    if (A != RHS) std::swap(A, B); // smax(A, B) pred A.
2075    EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B".
2076    // We analyze this as smax(A, B) pred A.
2077    P = Pred;
2078  } else if (match(RHS, m_SMax(m_Value(A), m_Value(B))) &&
2079             (A == LHS || B == LHS)) {
2080    if (A != LHS) std::swap(A, B); // A pred smax(A, B).
2081    EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B".
2082    // We analyze this as smax(A, B) swapped-pred A.
2083    P = CmpInst::getSwappedPredicate(Pred);
2084  } else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) &&
2085             (A == RHS || B == RHS)) {
2086    if (A != RHS) std::swap(A, B); // smin(A, B) pred A.
2087    EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B".
2088    // We analyze this as smax(-A, -B) swapped-pred -A.
2089    // Note that we do not need to actually form -A or -B thanks to EqP.
2090    P = CmpInst::getSwappedPredicate(Pred);
2091  } else if (match(RHS, m_SMin(m_Value(A), m_Value(B))) &&
2092             (A == LHS || B == LHS)) {
2093    if (A != LHS) std::swap(A, B); // A pred smin(A, B).
2094    EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B".
2095    // We analyze this as smax(-A, -B) pred -A.
2096    // Note that we do not need to actually form -A or -B thanks to EqP.
2097    P = Pred;
2098  }
2099  if (P != CmpInst::BAD_ICMP_PREDICATE) {
2100    // Cases correspond to "max(A, B) p A".
2101    switch (P) {
2102    default:
2103      break;
2104    case CmpInst::ICMP_EQ:
2105    case CmpInst::ICMP_SLE:
2106      // Equivalent to "A EqP B".  This may be the same as the condition tested
2107      // in the max/min; if so, we can just return that.
2108      if (Value *V = ExtractEquivalentCondition(LHS, EqP, A, B))
2109        return V;
2110      if (Value *V = ExtractEquivalentCondition(RHS, EqP, A, B))
2111        return V;
2112      // Otherwise, see if "A EqP B" simplifies.
2113      if (MaxRecurse)
2114        if (Value *V = SimplifyICmpInst(EqP, A, B, TD, TLI, DT, MaxRecurse-1))
2115          return V;
2116      break;
2117    case CmpInst::ICMP_NE:
2118    case CmpInst::ICMP_SGT: {
2119      CmpInst::Predicate InvEqP = CmpInst::getInversePredicate(EqP);
2120      // Equivalent to "A InvEqP B".  This may be the same as the condition
2121      // tested in the max/min; if so, we can just return that.
2122      if (Value *V = ExtractEquivalentCondition(LHS, InvEqP, A, B))
2123        return V;
2124      if (Value *V = ExtractEquivalentCondition(RHS, InvEqP, A, B))
2125        return V;
2126      // Otherwise, see if "A InvEqP B" simplifies.
2127      if (MaxRecurse)
2128        if (Value *V = SimplifyICmpInst(InvEqP, A, B, TD, TLI, DT, MaxRecurse-1))
2129          return V;
2130      break;
2131    }
2132    case CmpInst::ICMP_SGE:
2133      // Always true.
2134      return getTrue(ITy);
2135    case CmpInst::ICMP_SLT:
2136      // Always false.
2137      return getFalse(ITy);
2138    }
2139  }
2140
2141  // Unsigned variants on "max(a,b)>=a -> true".
2142  P = CmpInst::BAD_ICMP_PREDICATE;
2143  if (match(LHS, m_UMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) {
2144    if (A != RHS) std::swap(A, B); // umax(A, B) pred A.
2145    EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B".
2146    // We analyze this as umax(A, B) pred A.
2147    P = Pred;
2148  } else if (match(RHS, m_UMax(m_Value(A), m_Value(B))) &&
2149             (A == LHS || B == LHS)) {
2150    if (A != LHS) std::swap(A, B); // A pred umax(A, B).
2151    EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B".
2152    // We analyze this as umax(A, B) swapped-pred A.
2153    P = CmpInst::getSwappedPredicate(Pred);
2154  } else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) &&
2155             (A == RHS || B == RHS)) {
2156    if (A != RHS) std::swap(A, B); // umin(A, B) pred A.
2157    EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B".
2158    // We analyze this as umax(-A, -B) swapped-pred -A.
2159    // Note that we do not need to actually form -A or -B thanks to EqP.
2160    P = CmpInst::getSwappedPredicate(Pred);
2161  } else if (match(RHS, m_UMin(m_Value(A), m_Value(B))) &&
2162             (A == LHS || B == LHS)) {
2163    if (A != LHS) std::swap(A, B); // A pred umin(A, B).
2164    EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B".
2165    // We analyze this as umax(-A, -B) pred -A.
2166    // Note that we do not need to actually form -A or -B thanks to EqP.
2167    P = Pred;
2168  }
2169  if (P != CmpInst::BAD_ICMP_PREDICATE) {
2170    // Cases correspond to "max(A, B) p A".
2171    switch (P) {
2172    default:
2173      break;
2174    case CmpInst::ICMP_EQ:
2175    case CmpInst::ICMP_ULE:
2176      // Equivalent to "A EqP B".  This may be the same as the condition tested
2177      // in the max/min; if so, we can just return that.
2178      if (Value *V = ExtractEquivalentCondition(LHS, EqP, A, B))
2179        return V;
2180      if (Value *V = ExtractEquivalentCondition(RHS, EqP, A, B))
2181        return V;
2182      // Otherwise, see if "A EqP B" simplifies.
2183      if (MaxRecurse)
2184        if (Value *V = SimplifyICmpInst(EqP, A, B, TD, TLI, DT, MaxRecurse-1))
2185          return V;
2186      break;
2187    case CmpInst::ICMP_NE:
2188    case CmpInst::ICMP_UGT: {
2189      CmpInst::Predicate InvEqP = CmpInst::getInversePredicate(EqP);
2190      // Equivalent to "A InvEqP B".  This may be the same as the condition
2191      // tested in the max/min; if so, we can just return that.
2192      if (Value *V = ExtractEquivalentCondition(LHS, InvEqP, A, B))
2193        return V;
2194      if (Value *V = ExtractEquivalentCondition(RHS, InvEqP, A, B))
2195        return V;
2196      // Otherwise, see if "A InvEqP B" simplifies.
2197      if (MaxRecurse)
2198        if (Value *V = SimplifyICmpInst(InvEqP, A, B, TD, TLI, DT, MaxRecurse-1))
2199          return V;
2200      break;
2201    }
2202    case CmpInst::ICMP_UGE:
2203      // Always true.
2204      return getTrue(ITy);
2205    case CmpInst::ICMP_ULT:
2206      // Always false.
2207      return getFalse(ITy);
2208    }
2209  }
2210
2211  // Variants on "max(x,y) >= min(x,z)".
2212  Value *C, *D;
2213  if (match(LHS, m_SMax(m_Value(A), m_Value(B))) &&
2214      match(RHS, m_SMin(m_Value(C), m_Value(D))) &&
2215      (A == C || A == D || B == C || B == D)) {
2216    // max(x, ?) pred min(x, ?).
2217    if (Pred == CmpInst::ICMP_SGE)
2218      // Always true.
2219      return getTrue(ITy);
2220    if (Pred == CmpInst::ICMP_SLT)
2221      // Always false.
2222      return getFalse(ITy);
2223  } else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) &&
2224             match(RHS, m_SMax(m_Value(C), m_Value(D))) &&
2225             (A == C || A == D || B == C || B == D)) {
2226    // min(x, ?) pred max(x, ?).
2227    if (Pred == CmpInst::ICMP_SLE)
2228      // Always true.
2229      return getTrue(ITy);
2230    if (Pred == CmpInst::ICMP_SGT)
2231      // Always false.
2232      return getFalse(ITy);
2233  } else if (match(LHS, m_UMax(m_Value(A), m_Value(B))) &&
2234             match(RHS, m_UMin(m_Value(C), m_Value(D))) &&
2235             (A == C || A == D || B == C || B == D)) {
2236    // max(x, ?) pred min(x, ?).
2237    if (Pred == CmpInst::ICMP_UGE)
2238      // Always true.
2239      return getTrue(ITy);
2240    if (Pred == CmpInst::ICMP_ULT)
2241      // Always false.
2242      return getFalse(ITy);
2243  } else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) &&
2244             match(RHS, m_UMax(m_Value(C), m_Value(D))) &&
2245             (A == C || A == D || B == C || B == D)) {
2246    // min(x, ?) pred max(x, ?).
2247    if (Pred == CmpInst::ICMP_ULE)
2248      // Always true.
2249      return getTrue(ITy);
2250    if (Pred == CmpInst::ICMP_UGT)
2251      // Always false.
2252      return getFalse(ITy);
2253  }
2254
2255  // Simplify comparisons of GEPs.
2256  if (GetElementPtrInst *GLHS = dyn_cast<GetElementPtrInst>(LHS)) {
2257    if (GEPOperator *GRHS = dyn_cast<GEPOperator>(RHS)) {
2258      if (GLHS->getPointerOperand() == GRHS->getPointerOperand() &&
2259          GLHS->hasAllConstantIndices() && GRHS->hasAllConstantIndices()) {
2260        // The bases are equal and the indices are constant.  Build a constant
2261        // expression GEP with the same indices and a null base pointer to see
2262        // what constant folding can make out of it.
2263        Constant *Null = Constant::getNullValue(GLHS->getPointerOperandType());
2264        SmallVector<Value *, 4> IndicesLHS(GLHS->idx_begin(), GLHS->idx_end());
2265        Constant *NewLHS = ConstantExpr::getGetElementPtr(Null, IndicesLHS);
2266
2267        SmallVector<Value *, 4> IndicesRHS(GRHS->idx_begin(), GRHS->idx_end());
2268        Constant *NewRHS = ConstantExpr::getGetElementPtr(Null, IndicesRHS);
2269        return ConstantExpr::getICmp(Pred, NewLHS, NewRHS);
2270      }
2271    }
2272  }
2273
2274  // If the comparison is with the result of a select instruction, check whether
2275  // comparing with either branch of the select always yields the same value.
2276  if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
2277    if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, TLI, DT, MaxRecurse))
2278      return V;
2279
2280  // If the comparison is with the result of a phi instruction, check whether
2281  // doing the compare with each incoming phi value yields a common result.
2282  if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
2283    if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, TLI, DT, MaxRecurse))
2284      return V;
2285
2286  return 0;
2287}
2288
2289Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
2290                              const TargetData *TD,
2291                              const TargetLibraryInfo *TLI,
2292                              const DominatorTree *DT) {
2293  return ::SimplifyICmpInst(Predicate, LHS, RHS, TD, TLI, DT, RecursionLimit);
2294}
2295
2296/// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can
2297/// fold the result.  If not, this returns null.
2298static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
2299                               const TargetData *TD,
2300                               const TargetLibraryInfo *TLI,
2301                               const DominatorTree *DT,
2302                               unsigned MaxRecurse) {
2303  CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
2304  assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!");
2305
2306  if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
2307    if (Constant *CRHS = dyn_cast<Constant>(RHS))
2308      return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD, TLI);
2309
2310    // If we have a constant, make sure it is on the RHS.
2311    std::swap(LHS, RHS);
2312    Pred = CmpInst::getSwappedPredicate(Pred);
2313  }
2314
2315  // Fold trivial predicates.
2316  if (Pred == FCmpInst::FCMP_FALSE)
2317    return ConstantInt::get(GetCompareTy(LHS), 0);
2318  if (Pred == FCmpInst::FCMP_TRUE)
2319    return ConstantInt::get(GetCompareTy(LHS), 1);
2320
2321  if (isa<UndefValue>(RHS))                  // fcmp pred X, undef -> undef
2322    return UndefValue::get(GetCompareTy(LHS));
2323
2324  // fcmp x,x -> true/false.  Not all compares are foldable.
2325  if (LHS == RHS) {
2326    if (CmpInst::isTrueWhenEqual(Pred))
2327      return ConstantInt::get(GetCompareTy(LHS), 1);
2328    if (CmpInst::isFalseWhenEqual(Pred))
2329      return ConstantInt::get(GetCompareTy(LHS), 0);
2330  }
2331
2332  // Handle fcmp with constant RHS
2333  if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
2334    // If the constant is a nan, see if we can fold the comparison based on it.
2335    if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
2336      if (CFP->getValueAPF().isNaN()) {
2337        if (FCmpInst::isOrdered(Pred))   // True "if ordered and foo"
2338          return ConstantInt::getFalse(CFP->getContext());
2339        assert(FCmpInst::isUnordered(Pred) &&
2340               "Comparison must be either ordered or unordered!");
2341        // True if unordered.
2342        return ConstantInt::getTrue(CFP->getContext());
2343      }
2344      // Check whether the constant is an infinity.
2345      if (CFP->getValueAPF().isInfinity()) {
2346        if (CFP->getValueAPF().isNegative()) {
2347          switch (Pred) {
2348          case FCmpInst::FCMP_OLT:
2349            // No value is ordered and less than negative infinity.
2350            return ConstantInt::getFalse(CFP->getContext());
2351          case FCmpInst::FCMP_UGE:
2352            // All values are unordered with or at least negative infinity.
2353            return ConstantInt::getTrue(CFP->getContext());
2354          default:
2355            break;
2356          }
2357        } else {
2358          switch (Pred) {
2359          case FCmpInst::FCMP_OGT:
2360            // No value is ordered and greater than infinity.
2361            return ConstantInt::getFalse(CFP->getContext());
2362          case FCmpInst::FCMP_ULE:
2363            // All values are unordered with and at most infinity.
2364            return ConstantInt::getTrue(CFP->getContext());
2365          default:
2366            break;
2367          }
2368        }
2369      }
2370    }
2371  }
2372
2373  // If the comparison is with the result of a select instruction, check whether
2374  // comparing with either branch of the select always yields the same value.
2375  if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
2376    if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, TLI, DT, MaxRecurse))
2377      return V;
2378
2379  // If the comparison is with the result of a phi instruction, check whether
2380  // doing the compare with each incoming phi value yields a common result.
2381  if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
2382    if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, TLI, DT, MaxRecurse))
2383      return V;
2384
2385  return 0;
2386}
2387
2388Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
2389                              const TargetData *TD,
2390                              const TargetLibraryInfo *TLI,
2391                              const DominatorTree *DT) {
2392  return ::SimplifyFCmpInst(Predicate, LHS, RHS, TD, TLI, DT, RecursionLimit);
2393}
2394
2395/// SimplifySelectInst - Given operands for a SelectInst, see if we can fold
2396/// the result.  If not, this returns null.
2397Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal,
2398                                const TargetData *TD, const DominatorTree *) {
2399  // select true, X, Y  -> X
2400  // select false, X, Y -> Y
2401  if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal))
2402    return CB->getZExtValue() ? TrueVal : FalseVal;
2403
2404  // select C, X, X -> X
2405  if (TrueVal == FalseVal)
2406    return TrueVal;
2407
2408  if (isa<UndefValue>(CondVal)) {  // select undef, X, Y -> X or Y
2409    if (isa<Constant>(TrueVal))
2410      return TrueVal;
2411    return FalseVal;
2412  }
2413  if (isa<UndefValue>(TrueVal))   // select C, undef, X -> X
2414    return FalseVal;
2415  if (isa<UndefValue>(FalseVal))   // select C, X, undef -> X
2416    return TrueVal;
2417
2418  return 0;
2419}
2420
2421/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
2422/// fold the result.  If not, this returns null.
2423Value *llvm::SimplifyGEPInst(ArrayRef<Value *> Ops, const TargetData *TD,
2424                             const DominatorTree *) {
2425  // The type of the GEP pointer operand.
2426  PointerType *PtrTy = dyn_cast<PointerType>(Ops[0]->getType());
2427  // The GEP pointer operand is not a pointer, it's a vector of pointers.
2428  if (!PtrTy)
2429    return 0;
2430
2431  // getelementptr P -> P.
2432  if (Ops.size() == 1)
2433    return Ops[0];
2434
2435  if (isa<UndefValue>(Ops[0])) {
2436    // Compute the (pointer) type returned by the GEP instruction.
2437    Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, Ops.slice(1));
2438    Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace());
2439    return UndefValue::get(GEPTy);
2440  }
2441
2442  if (Ops.size() == 2) {
2443    // getelementptr P, 0 -> P.
2444    if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1]))
2445      if (C->isZero())
2446        return Ops[0];
2447    // getelementptr P, N -> P if P points to a type of zero size.
2448    if (TD) {
2449      Type *Ty = PtrTy->getElementType();
2450      if (Ty->isSized() && TD->getTypeAllocSize(Ty) == 0)
2451        return Ops[0];
2452    }
2453  }
2454
2455  // Check to see if this is constant foldable.
2456  for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2457    if (!isa<Constant>(Ops[i]))
2458      return 0;
2459
2460  return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]), Ops.slice(1));
2461}
2462
2463/// SimplifyInsertValueInst - Given operands for an InsertValueInst, see if we
2464/// can fold the result.  If not, this returns null.
2465Value *llvm::SimplifyInsertValueInst(Value *Agg, Value *Val,
2466                                     ArrayRef<unsigned> Idxs,
2467                                     const TargetData *,
2468                                     const DominatorTree *) {
2469  if (Constant *CAgg = dyn_cast<Constant>(Agg))
2470    if (Constant *CVal = dyn_cast<Constant>(Val))
2471      return ConstantFoldInsertValueInstruction(CAgg, CVal, Idxs);
2472
2473  // insertvalue x, undef, n -> x
2474  if (match(Val, m_Undef()))
2475    return Agg;
2476
2477  // insertvalue x, (extractvalue y, n), n
2478  if (ExtractValueInst *EV = dyn_cast<ExtractValueInst>(Val))
2479    if (EV->getAggregateOperand()->getType() == Agg->getType() &&
2480        EV->getIndices() == Idxs) {
2481      // insertvalue undef, (extractvalue y, n), n -> y
2482      if (match(Agg, m_Undef()))
2483        return EV->getAggregateOperand();
2484
2485      // insertvalue y, (extractvalue y, n), n -> y
2486      if (Agg == EV->getAggregateOperand())
2487        return Agg;
2488    }
2489
2490  return 0;
2491}
2492
2493/// SimplifyPHINode - See if we can fold the given phi.  If not, returns null.
2494static Value *SimplifyPHINode(PHINode *PN, const DominatorTree *DT) {
2495  // If all of the PHI's incoming values are the same then replace the PHI node
2496  // with the common value.
2497  Value *CommonValue = 0;
2498  bool HasUndefInput = false;
2499  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2500    Value *Incoming = PN->getIncomingValue(i);
2501    // If the incoming value is the phi node itself, it can safely be skipped.
2502    if (Incoming == PN) continue;
2503    if (isa<UndefValue>(Incoming)) {
2504      // Remember that we saw an undef value, but otherwise ignore them.
2505      HasUndefInput = true;
2506      continue;
2507    }
2508    if (CommonValue && Incoming != CommonValue)
2509      return 0;  // Not the same, bail out.
2510    CommonValue = Incoming;
2511  }
2512
2513  // If CommonValue is null then all of the incoming values were either undef or
2514  // equal to the phi node itself.
2515  if (!CommonValue)
2516    return UndefValue::get(PN->getType());
2517
2518  // If we have a PHI node like phi(X, undef, X), where X is defined by some
2519  // instruction, we cannot return X as the result of the PHI node unless it
2520  // dominates the PHI block.
2521  if (HasUndefInput)
2522    return ValueDominatesPHI(CommonValue, PN, DT) ? CommonValue : 0;
2523
2524  return CommonValue;
2525}
2526
2527//=== Helper functions for higher up the class hierarchy.
2528
2529/// SimplifyBinOp - Given operands for a BinaryOperator, see if we can
2530/// fold the result.  If not, this returns null.
2531static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
2532                            const TargetData *TD,
2533                            const TargetLibraryInfo *TLI,
2534                            const DominatorTree *DT,
2535                            unsigned MaxRecurse) {
2536  switch (Opcode) {
2537  case Instruction::Add:
2538    return SimplifyAddInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false,
2539                           TD, TLI, DT, MaxRecurse);
2540  case Instruction::Sub:
2541    return SimplifySubInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false,
2542                           TD, TLI, DT, MaxRecurse);
2543  case Instruction::Mul:  return SimplifyMulInst (LHS, RHS, TD, TLI, DT,
2544                                                  MaxRecurse);
2545  case Instruction::SDiv: return SimplifySDivInst(LHS, RHS, TD, TLI, DT,
2546                                                  MaxRecurse);
2547  case Instruction::UDiv: return SimplifyUDivInst(LHS, RHS, TD, TLI, DT,
2548                                                  MaxRecurse);
2549  case Instruction::FDiv: return SimplifyFDivInst(LHS, RHS, TD, TLI, DT,
2550                                                  MaxRecurse);
2551  case Instruction::SRem: return SimplifySRemInst(LHS, RHS, TD, TLI, DT,
2552                                                  MaxRecurse);
2553  case Instruction::URem: return SimplifyURemInst(LHS, RHS, TD, TLI, DT,
2554                                                  MaxRecurse);
2555  case Instruction::FRem: return SimplifyFRemInst(LHS, RHS, TD, TLI, DT,
2556                                                  MaxRecurse);
2557  case Instruction::Shl:
2558    return SimplifyShlInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false,
2559                           TD, TLI, DT, MaxRecurse);
2560  case Instruction::LShr:
2561    return SimplifyLShrInst(LHS, RHS, /*isExact*/false, TD, TLI, DT,
2562                            MaxRecurse);
2563  case Instruction::AShr:
2564    return SimplifyAShrInst(LHS, RHS, /*isExact*/false, TD, TLI, DT,
2565                            MaxRecurse);
2566  case Instruction::And: return SimplifyAndInst(LHS, RHS, TD, TLI, DT,
2567                                                MaxRecurse);
2568  case Instruction::Or:  return SimplifyOrInst (LHS, RHS, TD, TLI, DT,
2569                                                MaxRecurse);
2570  case Instruction::Xor: return SimplifyXorInst(LHS, RHS, TD, TLI, DT,
2571                                                MaxRecurse);
2572  default:
2573    if (Constant *CLHS = dyn_cast<Constant>(LHS))
2574      if (Constant *CRHS = dyn_cast<Constant>(RHS)) {
2575        Constant *COps[] = {CLHS, CRHS};
2576        return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, TD, TLI);
2577      }
2578
2579    // If the operation is associative, try some generic simplifications.
2580    if (Instruction::isAssociative(Opcode))
2581      if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, TD, TLI, DT,
2582                                              MaxRecurse))
2583        return V;
2584
2585    // If the operation is with the result of a select instruction, check whether
2586    // operating on either branch of the select always yields the same value.
2587    if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
2588      if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, TD, TLI, DT,
2589                                           MaxRecurse))
2590        return V;
2591
2592    // If the operation is with the result of a phi instruction, check whether
2593    // operating on all incoming values of the phi always yields the same value.
2594    if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
2595      if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, TD, TLI, DT,
2596                                        MaxRecurse))
2597        return V;
2598
2599    return 0;
2600  }
2601}
2602
2603Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
2604                           const TargetData *TD, const TargetLibraryInfo *TLI,
2605                           const DominatorTree *DT) {
2606  return ::SimplifyBinOp(Opcode, LHS, RHS, TD, TLI, DT, RecursionLimit);
2607}
2608
2609/// SimplifyCmpInst - Given operands for a CmpInst, see if we can
2610/// fold the result.
2611static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
2612                              const TargetData *TD,
2613                              const TargetLibraryInfo *TLI,
2614                              const DominatorTree *DT,
2615                              unsigned MaxRecurse) {
2616  if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate))
2617    return SimplifyICmpInst(Predicate, LHS, RHS, TD, TLI, DT, MaxRecurse);
2618  return SimplifyFCmpInst(Predicate, LHS, RHS, TD, TLI, DT, MaxRecurse);
2619}
2620
2621Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
2622                             const TargetData *TD, const TargetLibraryInfo *TLI,
2623                             const DominatorTree *DT) {
2624  return ::SimplifyCmpInst(Predicate, LHS, RHS, TD, TLI, DT, RecursionLimit);
2625}
2626
2627static Value *SimplifyCallInst(CallInst *CI) {
2628  // call undef -> undef
2629  if (isa<UndefValue>(CI->getCalledValue()))
2630    return UndefValue::get(CI->getType());
2631
2632  return 0;
2633}
2634
2635/// SimplifyInstruction - See if we can compute a simplified version of this
2636/// instruction.  If not, this returns null.
2637Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD,
2638                                 const TargetLibraryInfo *TLI,
2639                                 const DominatorTree *DT) {
2640  Value *Result;
2641
2642  switch (I->getOpcode()) {
2643  default:
2644    Result = ConstantFoldInstruction(I, TD, TLI);
2645    break;
2646  case Instruction::Add:
2647    Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1),
2648                             cast<BinaryOperator>(I)->hasNoSignedWrap(),
2649                             cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
2650                             TD, TLI, DT);
2651    break;
2652  case Instruction::Sub:
2653    Result = SimplifySubInst(I->getOperand(0), I->getOperand(1),
2654                             cast<BinaryOperator>(I)->hasNoSignedWrap(),
2655                             cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
2656                             TD, TLI, DT);
2657    break;
2658  case Instruction::Mul:
2659    Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2660    break;
2661  case Instruction::SDiv:
2662    Result = SimplifySDivInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2663    break;
2664  case Instruction::UDiv:
2665    Result = SimplifyUDivInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2666    break;
2667  case Instruction::FDiv:
2668    Result = SimplifyFDivInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2669    break;
2670  case Instruction::SRem:
2671    Result = SimplifySRemInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2672    break;
2673  case Instruction::URem:
2674    Result = SimplifyURemInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2675    break;
2676  case Instruction::FRem:
2677    Result = SimplifyFRemInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2678    break;
2679  case Instruction::Shl:
2680    Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1),
2681                             cast<BinaryOperator>(I)->hasNoSignedWrap(),
2682                             cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
2683                             TD, TLI, DT);
2684    break;
2685  case Instruction::LShr:
2686    Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1),
2687                              cast<BinaryOperator>(I)->isExact(),
2688                              TD, TLI, DT);
2689    break;
2690  case Instruction::AShr:
2691    Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1),
2692                              cast<BinaryOperator>(I)->isExact(),
2693                              TD, TLI, DT);
2694    break;
2695  case Instruction::And:
2696    Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2697    break;
2698  case Instruction::Or:
2699    Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2700    break;
2701  case Instruction::Xor:
2702    Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2703    break;
2704  case Instruction::ICmp:
2705    Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
2706                              I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2707    break;
2708  case Instruction::FCmp:
2709    Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
2710                              I->getOperand(0), I->getOperand(1), TD, TLI, DT);
2711    break;
2712  case Instruction::Select:
2713    Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1),
2714                                I->getOperand(2), TD, DT);
2715    break;
2716  case Instruction::GetElementPtr: {
2717    SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
2718    Result = SimplifyGEPInst(Ops, TD, DT);
2719    break;
2720  }
2721  case Instruction::InsertValue: {
2722    InsertValueInst *IV = cast<InsertValueInst>(I);
2723    Result = SimplifyInsertValueInst(IV->getAggregateOperand(),
2724                                     IV->getInsertedValueOperand(),
2725                                     IV->getIndices(), TD, DT);
2726    break;
2727  }
2728  case Instruction::PHI:
2729    Result = SimplifyPHINode(cast<PHINode>(I), DT);
2730    break;
2731  case Instruction::Call:
2732    Result = SimplifyCallInst(cast<CallInst>(I));
2733    break;
2734  }
2735
2736  /// If called on unreachable code, the above logic may report that the
2737  /// instruction simplified to itself.  Make life easier for users by
2738  /// detecting that case here, returning a safe value instead.
2739  return Result == I ? UndefValue::get(I->getType()) : Result;
2740}
2741
2742/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
2743/// delete the From instruction.  In addition to a basic RAUW, this does a
2744/// recursive simplification of the newly formed instructions.  This catches
2745/// things where one simplification exposes other opportunities.  This only
2746/// simplifies and deletes scalar operations, it does not change the CFG.
2747///
2748void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
2749                                     const TargetData *TD,
2750                                     const TargetLibraryInfo *TLI,
2751                                     const DominatorTree *DT) {
2752  assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
2753
2754  // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that
2755  // we can know if it gets deleted out from under us or replaced in a
2756  // recursive simplification.
2757  WeakVH FromHandle(From);
2758  WeakVH ToHandle(To);
2759
2760  while (!From->use_empty()) {
2761    // Update the instruction to use the new value.
2762    Use &TheUse = From->use_begin().getUse();
2763    Instruction *User = cast<Instruction>(TheUse.getUser());
2764    TheUse = To;
2765
2766    // Check to see if the instruction can be folded due to the operand
2767    // replacement.  For example changing (or X, Y) into (or X, -1) can replace
2768    // the 'or' with -1.
2769    Value *SimplifiedVal;
2770    {
2771      // Sanity check to make sure 'User' doesn't dangle across
2772      // SimplifyInstruction.
2773      AssertingVH<> UserHandle(User);
2774
2775      SimplifiedVal = SimplifyInstruction(User, TD, TLI, DT);
2776      if (SimplifiedVal == 0) continue;
2777    }
2778
2779    // Recursively simplify this user to the new value.
2780    ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD, TLI, DT);
2781    From = dyn_cast_or_null<Instruction>((Value*)FromHandle);
2782    To = ToHandle;
2783
2784    assert(ToHandle && "To value deleted by recursive simplification?");
2785
2786    // If the recursive simplification ended up revisiting and deleting
2787    // 'From' then we're done.
2788    if (From == 0)
2789      return;
2790  }
2791
2792  // If 'From' has value handles referring to it, do a real RAUW to update them.
2793  From->replaceAllUsesWith(To);
2794
2795  From->eraseFromParent();
2796}
2797