1 //===- InstructionSimplify.cpp - Fold instruction operands ----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This 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).
18 //===----------------------------------------------------------------------===//
20 #define DEBUG_TYPE "instsimplify"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/Analysis/InstructionSimplify.h"
23 #include "llvm/Analysis/ConstantFolding.h"
24 #include "llvm/Analysis/Dominators.h"
25 #include "llvm/Support/PatternMatch.h"
26 #include "llvm/Support/ValueHandle.h"
27 #include "llvm/Target/TargetData.h"
29 using namespace llvm::PatternMatch;
31 #define RecursionLimit 3
33 STATISTIC(NumExpand, "Number of expansions");
34 STATISTIC(NumFactor , "Number of factorizations");
35 STATISTIC(NumReassoc, "Number of reassociations");
37 static Value *SimplifyAndInst(Value *, Value *, const TargetData *,
38 const DominatorTree *, unsigned);
39 static Value *SimplifyBinOp(unsigned, Value *, Value *, const TargetData *,
40 const DominatorTree *, unsigned);
41 static Value *SimplifyCmpInst(unsigned, Value *, Value *, const TargetData *,
42 const DominatorTree *, unsigned);
43 static Value *SimplifyOrInst(Value *, Value *, const TargetData *,
44 const DominatorTree *, unsigned);
45 static Value *SimplifyXorInst(Value *, Value *, const TargetData *,
46 const DominatorTree *, unsigned);
48 /// ValueDominatesPHI - Does the given value dominate the specified phi node?
49 static bool ValueDominatesPHI(Value *V, PHINode *P, const DominatorTree *DT) {
50 Instruction *I = dyn_cast<Instruction>(V);
52 // Arguments and constants dominate all instructions.
55 // If we have a DominatorTree then do a precise test.
57 return DT->dominates(I, P);
59 // Otherwise, if the instruction is in the entry block, and is not an invoke,
60 // then it obviously dominates all phi nodes.
61 if (I->getParent() == &I->getParent()->getParent()->getEntryBlock() &&
68 /// ExpandBinOp - Simplify "A op (B op' C)" by distributing op over op', turning
69 /// it into "(A op B) op' (A op C)". Here "op" is given by Opcode and "op'" is
70 /// given by OpcodeToExpand, while "A" corresponds to LHS and "B op' C" to RHS.
71 /// Also performs the transform "(A op' B) op C" -> "(A op C) op' (B op C)".
72 /// Returns the simplified value, or null if no simplification was performed.
73 static Value *ExpandBinOp(unsigned Opcode, Value *LHS, Value *RHS,
74 unsigned OpcodeToExpand, const TargetData *TD,
75 const DominatorTree *DT, unsigned MaxRecurse) {
76 // Recursion is always used, so bail out at once if we already hit the limit.
80 // Check whether the expression has the form "(A op' B) op C".
81 if (BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS))
82 if (Op0->getOpcode() == OpcodeToExpand) {
83 // It does! Try turning it into "(A op C) op' (B op C)".
84 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS;
85 // Do "A op C" and "B op C" both simplify?
86 if (Value *L = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse))
87 if (Value *R = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) {
88 // They do! Return "L op' R" if it simplifies or is already available.
89 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS.
90 if ((L == A && R == B) || (Instruction::isCommutative(OpcodeToExpand)
91 && L == B && R == A)) {
95 // Otherwise return "L op' R" if it simplifies.
96 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT,
104 // Check whether the expression has the form "A op (B op' C)".
105 if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS))
106 if (Op1->getOpcode() == OpcodeToExpand) {
107 // It does! Try turning it into "(A op B) op' (A op C)".
108 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1);
109 // Do "A op B" and "A op C" both simplify?
110 if (Value *L = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse))
111 if (Value *R = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse)) {
112 // They do! Return "L op' R" if it simplifies or is already available.
113 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS.
114 if ((L == B && R == C) || (Instruction::isCommutative(OpcodeToExpand)
115 && L == C && R == B)) {
119 // Otherwise return "L op' R" if it simplifies.
120 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT,
131 /// FactorizeBinOp - Simplify "LHS Opcode RHS" by factorizing out a common term
132 /// using the operation OpCodeToExtract. For example, when Opcode is Add and
133 /// OpCodeToExtract is Mul then this tries to turn "(A*B)+(A*C)" into "A*(B+C)".
134 /// Returns the simplified value, or null if no simplification was performed.
135 static Value *FactorizeBinOp(unsigned Opcode, Value *LHS, Value *RHS,
136 unsigned OpcodeToExtract, const TargetData *TD,
137 const DominatorTree *DT, unsigned MaxRecurse) {
138 // Recursion is always used, so bail out at once if we already hit the limit.
142 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
143 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
145 if (!Op0 || Op0->getOpcode() != OpcodeToExtract ||
146 !Op1 || Op1->getOpcode() != OpcodeToExtract)
149 // The expression has the form "(A op' B) op (C op' D)".
150 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1);
151 Value *C = Op1->getOperand(0), *D = Op1->getOperand(1);
153 // Use left distributivity, i.e. "X op' (Y op Z) = (X op' Y) op (X op' Z)".
154 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the
155 // commutative case, "(A op' B) op (C op' A)"?
156 if (A == C || (Instruction::isCommutative(OpcodeToExtract) && A == D)) {
157 Value *DD = A == C ? D : C;
158 // Form "A op' (B op DD)" if it simplifies completely.
159 // Does "B op DD" simplify?
160 if (Value *V = SimplifyBinOp(Opcode, B, DD, TD, DT, MaxRecurse)) {
161 // It does! Return "A op' V" if it simplifies or is already available.
162 // If V equals B then "A op' V" is just the LHS. If V equals DD then
163 // "A op' V" is just the RHS.
164 if (V == B || V == DD) {
166 return V == B ? LHS : RHS;
168 // Otherwise return "A op' V" if it simplifies.
169 if (Value *W = SimplifyBinOp(OpcodeToExtract, A, V, TD, DT, MaxRecurse)) {
176 // Use right distributivity, i.e. "(X op Y) op' Z = (X op' Z) op (Y op' Z)".
177 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the
178 // commutative case, "(A op' B) op (B op' D)"?
179 if (B == D || (Instruction::isCommutative(OpcodeToExtract) && B == C)) {
180 Value *CC = B == D ? C : D;
181 // Form "(A op CC) op' B" if it simplifies completely..
182 // Does "A op CC" simplify?
183 if (Value *V = SimplifyBinOp(Opcode, A, CC, TD, DT, MaxRecurse)) {
184 // It does! Return "V op' B" if it simplifies or is already available.
185 // If V equals A then "V op' B" is just the LHS. If V equals CC then
186 // "V op' B" is just the RHS.
187 if (V == A || V == CC) {
189 return V == A ? LHS : RHS;
191 // Otherwise return "V op' B" if it simplifies.
192 if (Value *W = SimplifyBinOp(OpcodeToExtract, V, B, TD, DT, MaxRecurse)) {
202 /// SimplifyAssociativeBinOp - Generic simplifications for associative binary
203 /// operations. Returns the simpler value, or null if none was found.
204 static Value *SimplifyAssociativeBinOp(unsigned Opcode, Value *LHS, Value *RHS,
205 const TargetData *TD,
206 const DominatorTree *DT,
207 unsigned MaxRecurse) {
208 assert(Instruction::isAssociative(Opcode) && "Not an associative operation!");
210 // Recursion is always used, so bail out at once if we already hit the limit.
214 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
215 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
217 // Transform: "(A op B) op C" ==> "A op (B op C)" if it simplifies completely.
218 if (Op0 && Op0->getOpcode() == Opcode) {
219 Value *A = Op0->getOperand(0);
220 Value *B = Op0->getOperand(1);
223 // Does "B op C" simplify?
224 if (Value *V = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) {
225 // It does! Return "A op V" if it simplifies or is already available.
226 // If V equals B then "A op V" is just the LHS.
227 if (V == B) return LHS;
228 // Otherwise return "A op V" if it simplifies.
229 if (Value *W = SimplifyBinOp(Opcode, A, V, TD, DT, MaxRecurse)) {
236 // Transform: "A op (B op C)" ==> "(A op B) op C" if it simplifies completely.
237 if (Op1 && Op1->getOpcode() == Opcode) {
239 Value *B = Op1->getOperand(0);
240 Value *C = Op1->getOperand(1);
242 // Does "A op B" simplify?
243 if (Value *V = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse)) {
244 // It does! Return "V op C" if it simplifies or is already available.
245 // If V equals B then "V op C" is just the RHS.
246 if (V == B) return RHS;
247 // Otherwise return "V op C" if it simplifies.
248 if (Value *W = SimplifyBinOp(Opcode, V, C, TD, DT, MaxRecurse)) {
255 // The remaining transforms require commutativity as well as associativity.
256 if (!Instruction::isCommutative(Opcode))
259 // Transform: "(A op B) op C" ==> "(C op A) op B" if it simplifies completely.
260 if (Op0 && Op0->getOpcode() == Opcode) {
261 Value *A = Op0->getOperand(0);
262 Value *B = Op0->getOperand(1);
265 // Does "C op A" simplify?
266 if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) {
267 // It does! Return "V op B" if it simplifies or is already available.
268 // If V equals A then "V op B" is just the LHS.
269 if (V == A) return LHS;
270 // Otherwise return "V op B" if it simplifies.
271 if (Value *W = SimplifyBinOp(Opcode, V, B, TD, DT, MaxRecurse)) {
278 // Transform: "A op (B op C)" ==> "B op (C op A)" if it simplifies completely.
279 if (Op1 && Op1->getOpcode() == Opcode) {
281 Value *B = Op1->getOperand(0);
282 Value *C = Op1->getOperand(1);
284 // Does "C op A" simplify?
285 if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) {
286 // It does! Return "B op V" if it simplifies or is already available.
287 // If V equals C then "B op V" is just the RHS.
288 if (V == C) return RHS;
289 // Otherwise return "B op V" if it simplifies.
290 if (Value *W = SimplifyBinOp(Opcode, B, V, TD, DT, MaxRecurse)) {
300 /// ThreadBinOpOverSelect - In the case of a binary operation with a select
301 /// instruction as an operand, try to simplify the binop by seeing whether
302 /// evaluating it on both branches of the select results in the same value.
303 /// Returns the common value if so, otherwise returns null.
304 static Value *ThreadBinOpOverSelect(unsigned Opcode, Value *LHS, Value *RHS,
305 const TargetData *TD,
306 const DominatorTree *DT,
307 unsigned MaxRecurse) {
308 // Recursion is always used, so bail out at once if we already hit the limit.
313 if (isa<SelectInst>(LHS)) {
314 SI = cast<SelectInst>(LHS);
316 assert(isa<SelectInst>(RHS) && "No select instruction operand!");
317 SI = cast<SelectInst>(RHS);
320 // Evaluate the BinOp on the true and false branches of the select.
324 TV = SimplifyBinOp(Opcode, SI->getTrueValue(), RHS, TD, DT, MaxRecurse);
325 FV = SimplifyBinOp(Opcode, SI->getFalseValue(), RHS, TD, DT, MaxRecurse);
327 TV = SimplifyBinOp(Opcode, LHS, SI->getTrueValue(), TD, DT, MaxRecurse);
328 FV = SimplifyBinOp(Opcode, LHS, SI->getFalseValue(), TD, DT, MaxRecurse);
331 // If they simplified to the same value, then return the common value.
332 // If they both failed to simplify then return null.
336 // If one branch simplified to undef, return the other one.
337 if (TV && isa<UndefValue>(TV))
339 if (FV && isa<UndefValue>(FV))
342 // If applying the operation did not change the true and false select values,
343 // then the result of the binop is the select itself.
344 if (TV == SI->getTrueValue() && FV == SI->getFalseValue())
347 // If one branch simplified and the other did not, and the simplified
348 // value is equal to the unsimplified one, return the simplified value.
349 // For example, select (cond, X, X & Z) & Z -> X & Z.
350 if ((FV && !TV) || (TV && !FV)) {
351 // Check that the simplified value has the form "X op Y" where "op" is the
352 // same as the original operation.
353 Instruction *Simplified = dyn_cast<Instruction>(FV ? FV : TV);
354 if (Simplified && Simplified->getOpcode() == Opcode) {
355 // The value that didn't simplify is "UnsimplifiedLHS op UnsimplifiedRHS".
356 // We already know that "op" is the same as for the simplified value. See
357 // if the operands match too. If so, return the simplified value.
358 Value *UnsimplifiedBranch = FV ? SI->getTrueValue() : SI->getFalseValue();
359 Value *UnsimplifiedLHS = SI == LHS ? UnsimplifiedBranch : LHS;
360 Value *UnsimplifiedRHS = SI == LHS ? RHS : UnsimplifiedBranch;
361 if (Simplified->getOperand(0) == UnsimplifiedLHS &&
362 Simplified->getOperand(1) == UnsimplifiedRHS)
364 if (Simplified->isCommutative() &&
365 Simplified->getOperand(1) == UnsimplifiedLHS &&
366 Simplified->getOperand(0) == UnsimplifiedRHS)
374 /// ThreadCmpOverSelect - In the case of a comparison with a select instruction,
375 /// try to simplify the comparison by seeing whether both branches of the select
376 /// result in the same value. Returns the common value if so, otherwise returns
378 static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS,
379 Value *RHS, const TargetData *TD,
380 const DominatorTree *DT,
381 unsigned MaxRecurse) {
382 // Recursion is always used, so bail out at once if we already hit the limit.
386 // Make sure the select is on the LHS.
387 if (!isa<SelectInst>(LHS)) {
389 Pred = CmpInst::getSwappedPredicate(Pred);
391 assert(isa<SelectInst>(LHS) && "Not comparing with a select instruction!");
392 SelectInst *SI = cast<SelectInst>(LHS);
394 // Now that we have "cmp select(cond, TV, FV), RHS", analyse it.
395 // Does "cmp TV, RHS" simplify?
396 if (Value *TCmp = SimplifyCmpInst(Pred, SI->getTrueValue(), RHS, TD, DT,
398 // It does! Does "cmp FV, RHS" simplify?
399 if (Value *FCmp = SimplifyCmpInst(Pred, SI->getFalseValue(), RHS, TD, DT,
401 // It does! If they simplified to the same value, then use it as the
402 // result of the original comparison.
408 /// ThreadBinOpOverPHI - In the case of a binary operation with an operand that
409 /// is a PHI instruction, try to simplify the binop by seeing whether evaluating
410 /// it on the incoming phi values yields the same result for every value. If so
411 /// returns the common value, otherwise returns null.
412 static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS,
413 const TargetData *TD, const DominatorTree *DT,
414 unsigned MaxRecurse) {
415 // Recursion is always used, so bail out at once if we already hit the limit.
420 if (isa<PHINode>(LHS)) {
421 PI = cast<PHINode>(LHS);
422 // Bail out if RHS and the phi may be mutually interdependent due to a loop.
423 if (!ValueDominatesPHI(RHS, PI, DT))
426 assert(isa<PHINode>(RHS) && "No PHI instruction operand!");
427 PI = cast<PHINode>(RHS);
428 // Bail out if LHS and the phi may be mutually interdependent due to a loop.
429 if (!ValueDominatesPHI(LHS, PI, DT))
433 // Evaluate the BinOp on the incoming phi values.
434 Value *CommonValue = 0;
435 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
436 Value *Incoming = PI->getIncomingValue(i);
437 // If the incoming value is the phi node itself, it can safely be skipped.
438 if (Incoming == PI) continue;
439 Value *V = PI == LHS ?
440 SimplifyBinOp(Opcode, Incoming, RHS, TD, DT, MaxRecurse) :
441 SimplifyBinOp(Opcode, LHS, Incoming, TD, DT, MaxRecurse);
442 // If the operation failed to simplify, or simplified to a different value
443 // to previously, then give up.
444 if (!V || (CommonValue && V != CommonValue))
452 /// ThreadCmpOverPHI - In the case of a comparison with a PHI instruction, try
453 /// try to simplify the comparison by seeing whether comparing with all of the
454 /// incoming phi values yields the same result every time. If so returns the
455 /// common result, otherwise returns null.
456 static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS,
457 const TargetData *TD, const DominatorTree *DT,
458 unsigned MaxRecurse) {
459 // Recursion is always used, so bail out at once if we already hit the limit.
463 // Make sure the phi is on the LHS.
464 if (!isa<PHINode>(LHS)) {
466 Pred = CmpInst::getSwappedPredicate(Pred);
468 assert(isa<PHINode>(LHS) && "Not comparing with a phi instruction!");
469 PHINode *PI = cast<PHINode>(LHS);
471 // Bail out if RHS and the phi may be mutually interdependent due to a loop.
472 if (!ValueDominatesPHI(RHS, PI, DT))
475 // Evaluate the BinOp on the incoming phi values.
476 Value *CommonValue = 0;
477 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
478 Value *Incoming = PI->getIncomingValue(i);
479 // If the incoming value is the phi node itself, it can safely be skipped.
480 if (Incoming == PI) continue;
481 Value *V = SimplifyCmpInst(Pred, Incoming, RHS, TD, DT, MaxRecurse);
482 // If the operation failed to simplify, or simplified to a different value
483 // to previously, then give up.
484 if (!V || (CommonValue && V != CommonValue))
492 /// SimplifyAddInst - Given operands for an Add, see if we can
493 /// fold the result. If not, this returns null.
494 static Value *SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
495 const TargetData *TD, const DominatorTree *DT,
496 unsigned MaxRecurse) {
497 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
498 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
499 Constant *Ops[] = { CLHS, CRHS };
500 return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(),
504 // Canonicalize the constant to the RHS.
508 // X + undef -> undef
509 if (isa<UndefValue>(Op1))
513 if (match(Op1, m_Zero()))
520 if (match(Op1, m_Sub(m_Value(Y), m_Specific(Op0))) ||
521 match(Op0, m_Sub(m_Value(Y), m_Specific(Op1))))
524 // X + ~X -> -1 since ~X = -X-1
525 if (match(Op0, m_Not(m_Specific(Op1))) ||
526 match(Op1, m_Not(m_Specific(Op0))))
527 return Constant::getAllOnesValue(Op0->getType());
530 if (MaxRecurse && Op0->getType()->isIntegerTy(1))
531 if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1))
534 // Try some generic simplifications for associative operations.
535 if (Value *V = SimplifyAssociativeBinOp(Instruction::Add, Op0, Op1, TD, DT,
539 // Mul distributes over Add. Try some generic simplifications based on this.
540 if (Value *V = FactorizeBinOp(Instruction::Add, Op0, Op1, Instruction::Mul,
544 // Threading Add over selects and phi nodes is pointless, so don't bother.
545 // Threading over the select in "A + select(cond, B, C)" means evaluating
546 // "A+B" and "A+C" and seeing if they are equal; but they are equal if and
547 // only if B and C are equal. If B and C are equal then (since we assume
548 // that operands have already been simplified) "select(cond, B, C)" should
549 // have been simplified to the common value of B and C already. Analysing
550 // "A+B" and "A+C" thus gains nothing, but costs compile time. Similarly
551 // for threading over phi nodes.
556 Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
557 const TargetData *TD, const DominatorTree *DT) {
558 return ::SimplifyAddInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit);
561 /// SimplifySubInst - Given operands for a Sub, see if we can
562 /// fold the result. If not, this returns null.
563 static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
564 const TargetData *TD, const DominatorTree *DT,
565 unsigned MaxRecurse) {
566 if (Constant *CLHS = dyn_cast<Constant>(Op0))
567 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
568 Constant *Ops[] = { CLHS, CRHS };
569 return ConstantFoldInstOperands(Instruction::Sub, CLHS->getType(),
573 // X - undef -> undef
574 // undef - X -> undef
575 if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1))
576 return UndefValue::get(Op0->getType());
579 if (match(Op1, m_Zero()))
584 return Constant::getNullValue(Op0->getType());
589 if (match(Op0, m_Add(m_Value(X), m_Specific(Op1))) ||
590 match(Op0, m_Add(m_Specific(Op1), m_Value(X))))
594 if (MaxRecurse && Op0->getType()->isIntegerTy(1))
595 if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1))
598 // Mul distributes over Sub. Try some generic simplifications based on this.
599 if (Value *V = FactorizeBinOp(Instruction::Sub, Op0, Op1, Instruction::Mul,
603 // Threading Sub over selects and phi nodes is pointless, so don't bother.
604 // Threading over the select in "A - select(cond, B, C)" means evaluating
605 // "A-B" and "A-C" and seeing if they are equal; but they are equal if and
606 // only if B and C are equal. If B and C are equal then (since we assume
607 // that operands have already been simplified) "select(cond, B, C)" should
608 // have been simplified to the common value of B and C already. Analysing
609 // "A-B" and "A-C" thus gains nothing, but costs compile time. Similarly
610 // for threading over phi nodes.
615 Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
616 const TargetData *TD, const DominatorTree *DT) {
617 return ::SimplifySubInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit);
620 /// SimplifyMulInst - Given operands for a Mul, see if we can
621 /// fold the result. If not, this returns null.
622 static Value *SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
623 const DominatorTree *DT, unsigned MaxRecurse) {
624 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
625 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
626 Constant *Ops[] = { CLHS, CRHS };
627 return ConstantFoldInstOperands(Instruction::Mul, CLHS->getType(),
631 // Canonicalize the constant to the RHS.
636 if (isa<UndefValue>(Op1))
637 return Constant::getNullValue(Op0->getType());
640 if (match(Op1, m_Zero()))
644 if (match(Op1, m_One()))
648 if (MaxRecurse && Op0->getType()->isIntegerTy(1))
649 if (Value *V = SimplifyAndInst(Op0, Op1, TD, DT, MaxRecurse-1))
652 // Try some generic simplifications for associative operations.
653 if (Value *V = SimplifyAssociativeBinOp(Instruction::Mul, Op0, Op1, TD, DT,
657 // Mul distributes over Add. Try some generic simplifications based on this.
658 if (Value *V = ExpandBinOp(Instruction::Mul, Op0, Op1, Instruction::Add,
662 // If the operation is with the result of a select instruction, check whether
663 // operating on either branch of the select always yields the same value.
664 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
665 if (Value *V = ThreadBinOpOverSelect(Instruction::Mul, Op0, Op1, TD, DT,
669 // If the operation is with the result of a phi instruction, check whether
670 // operating on all incoming values of the phi always yields the same value.
671 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
672 if (Value *V = ThreadBinOpOverPHI(Instruction::Mul, Op0, Op1, TD, DT,
679 Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
680 const DominatorTree *DT) {
681 return ::SimplifyMulInst(Op0, Op1, TD, DT, RecursionLimit);
684 /// SimplifyAndInst - Given operands for an And, see if we can
685 /// fold the result. If not, this returns null.
686 static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
687 const DominatorTree *DT, unsigned MaxRecurse) {
688 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
689 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
690 Constant *Ops[] = { CLHS, CRHS };
691 return ConstantFoldInstOperands(Instruction::And, CLHS->getType(),
695 // Canonicalize the constant to the RHS.
700 if (isa<UndefValue>(Op1))
701 return Constant::getNullValue(Op0->getType());
708 if (match(Op1, m_Zero()))
712 if (match(Op1, m_AllOnes()))
715 // A & ~A = ~A & A = 0
716 Value *A = 0, *B = 0;
717 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
718 (match(Op1, m_Not(m_Value(A))) && A == Op0))
719 return Constant::getNullValue(Op0->getType());
722 if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
723 (A == Op1 || B == Op1))
727 if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
728 (A == Op0 || B == Op0))
731 // Try some generic simplifications for associative operations.
732 if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, TD, DT,
736 // And distributes over Or. Try some generic simplifications based on this.
737 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Or,
741 // And distributes over Xor. Try some generic simplifications based on this.
742 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Xor,
746 // Or distributes over And. Try some generic simplifications based on this.
747 if (Value *V = FactorizeBinOp(Instruction::And, Op0, Op1, Instruction::Or,
751 // If the operation is with the result of a select instruction, check whether
752 // operating on either branch of the select always yields the same value.
753 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
754 if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, TD, DT,
758 // If the operation is with the result of a phi instruction, check whether
759 // operating on all incoming values of the phi always yields the same value.
760 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
761 if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, TD, DT,
768 Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
769 const DominatorTree *DT) {
770 return ::SimplifyAndInst(Op0, Op1, TD, DT, RecursionLimit);
773 /// SimplifyOrInst - Given operands for an Or, see if we can
774 /// fold the result. If not, this returns null.
775 static Value *SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
776 const DominatorTree *DT, unsigned MaxRecurse) {
777 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
778 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
779 Constant *Ops[] = { CLHS, CRHS };
780 return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(),
784 // Canonicalize the constant to the RHS.
789 if (isa<UndefValue>(Op1))
790 return Constant::getAllOnesValue(Op0->getType());
797 if (match(Op1, m_Zero()))
801 if (match(Op1, m_AllOnes()))
804 // A | ~A = ~A | A = -1
805 Value *A = 0, *B = 0;
806 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
807 (match(Op1, m_Not(m_Value(A))) && A == Op0))
808 return Constant::getAllOnesValue(Op0->getType());
811 if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
812 (A == Op1 || B == Op1))
816 if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
817 (A == Op0 || B == Op0))
820 // Try some generic simplifications for associative operations.
821 if (Value *V = SimplifyAssociativeBinOp(Instruction::Or, Op0, Op1, TD, DT,
825 // Or distributes over And. Try some generic simplifications based on this.
826 if (Value *V = ExpandBinOp(Instruction::Or, Op0, Op1, Instruction::And,
830 // And distributes over Or. Try some generic simplifications based on this.
831 if (Value *V = FactorizeBinOp(Instruction::Or, Op0, Op1, Instruction::And,
835 // If the operation is with the result of a select instruction, check whether
836 // operating on either branch of the select always yields the same value.
837 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
838 if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, TD, DT,
842 // If the operation is with the result of a phi instruction, check whether
843 // operating on all incoming values of the phi always yields the same value.
844 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
845 if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, TD, DT,
852 Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
853 const DominatorTree *DT) {
854 return ::SimplifyOrInst(Op0, Op1, TD, DT, RecursionLimit);
857 /// SimplifyXorInst - Given operands for a Xor, see if we can
858 /// fold the result. If not, this returns null.
859 static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
860 const DominatorTree *DT, unsigned MaxRecurse) {
861 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
862 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
863 Constant *Ops[] = { CLHS, CRHS };
864 return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(),
868 // Canonicalize the constant to the RHS.
872 // A ^ undef -> undef
873 if (isa<UndefValue>(Op1))
877 if (match(Op1, m_Zero()))
882 return Constant::getNullValue(Op0->getType());
884 // A ^ ~A = ~A ^ A = -1
886 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
887 (match(Op1, m_Not(m_Value(A))) && A == Op0))
888 return Constant::getAllOnesValue(Op0->getType());
890 // Try some generic simplifications for associative operations.
891 if (Value *V = SimplifyAssociativeBinOp(Instruction::Xor, Op0, Op1, TD, DT,
895 // And distributes over Xor. Try some generic simplifications based on this.
896 if (Value *V = FactorizeBinOp(Instruction::Xor, Op0, Op1, Instruction::And,
900 // Threading Xor over selects and phi nodes is pointless, so don't bother.
901 // Threading over the select in "A ^ select(cond, B, C)" means evaluating
902 // "A^B" and "A^C" and seeing if they are equal; but they are equal if and
903 // only if B and C are equal. If B and C are equal then (since we assume
904 // that operands have already been simplified) "select(cond, B, C)" should
905 // have been simplified to the common value of B and C already. Analysing
906 // "A^B" and "A^C" thus gains nothing, but costs compile time. Similarly
907 // for threading over phi nodes.
912 Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
913 const DominatorTree *DT) {
914 return ::SimplifyXorInst(Op0, Op1, TD, DT, RecursionLimit);
917 static const Type *GetCompareTy(Value *Op) {
918 return CmpInst::makeCmpResultType(Op->getType());
921 /// SimplifyICmpInst - Given operands for an ICmpInst, see if we can
922 /// fold the result. If not, this returns null.
923 static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
924 const TargetData *TD, const DominatorTree *DT,
925 unsigned MaxRecurse) {
926 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
927 assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!");
929 if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
930 if (Constant *CRHS = dyn_cast<Constant>(RHS))
931 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD);
933 // If we have a constant, make sure it is on the RHS.
935 Pred = CmpInst::getSwappedPredicate(Pred);
938 // ITy - This is the return type of the compare we're considering.
939 const Type *ITy = GetCompareTy(LHS);
941 // icmp X, X -> true/false
942 // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false
943 // because X could be 0.
944 if (LHS == RHS || isa<UndefValue>(RHS))
945 return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred));
947 // icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
948 // addresses never equal each other! We already know that Op0 != Op1.
949 if ((isa<GlobalValue>(LHS) || isa<AllocaInst>(LHS) ||
950 isa<ConstantPointerNull>(LHS)) &&
951 (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) ||
952 isa<ConstantPointerNull>(RHS)))
953 return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
955 // See if we are doing a comparison with a constant.
956 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
957 // If we have an icmp le or icmp ge instruction, turn it into the
958 // appropriate icmp lt or icmp gt instruction. This allows us to rely on
959 // them being folded in the code below.
962 case ICmpInst::ICMP_ULE:
963 if (CI->isMaxValue(false)) // A <=u MAX -> TRUE
964 return ConstantInt::getTrue(CI->getContext());
966 case ICmpInst::ICMP_SLE:
967 if (CI->isMaxValue(true)) // A <=s MAX -> TRUE
968 return ConstantInt::getTrue(CI->getContext());
970 case ICmpInst::ICMP_UGE:
971 if (CI->isMinValue(false)) // A >=u MIN -> TRUE
972 return ConstantInt::getTrue(CI->getContext());
974 case ICmpInst::ICMP_SGE:
975 if (CI->isMinValue(true)) // A >=s MIN -> TRUE
976 return ConstantInt::getTrue(CI->getContext());
981 // If the comparison is with the result of a select instruction, check whether
982 // comparing with either branch of the select always yields the same value.
983 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
984 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse))
987 // If the comparison is with the result of a phi instruction, check whether
988 // doing the compare with each incoming phi value yields a common result.
989 if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
990 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse))
996 Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
997 const TargetData *TD, const DominatorTree *DT) {
998 return ::SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
1001 /// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can
1002 /// fold the result. If not, this returns null.
1003 static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1004 const TargetData *TD, const DominatorTree *DT,
1005 unsigned MaxRecurse) {
1006 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
1007 assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!");
1009 if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
1010 if (Constant *CRHS = dyn_cast<Constant>(RHS))
1011 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD);
1013 // If we have a constant, make sure it is on the RHS.
1014 std::swap(LHS, RHS);
1015 Pred = CmpInst::getSwappedPredicate(Pred);
1018 // Fold trivial predicates.
1019 if (Pred == FCmpInst::FCMP_FALSE)
1020 return ConstantInt::get(GetCompareTy(LHS), 0);
1021 if (Pred == FCmpInst::FCMP_TRUE)
1022 return ConstantInt::get(GetCompareTy(LHS), 1);
1024 if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef
1025 return UndefValue::get(GetCompareTy(LHS));
1027 // fcmp x,x -> true/false. Not all compares are foldable.
1029 if (CmpInst::isTrueWhenEqual(Pred))
1030 return ConstantInt::get(GetCompareTy(LHS), 1);
1031 if (CmpInst::isFalseWhenEqual(Pred))
1032 return ConstantInt::get(GetCompareTy(LHS), 0);
1035 // Handle fcmp with constant RHS
1036 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
1037 // If the constant is a nan, see if we can fold the comparison based on it.
1038 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
1039 if (CFP->getValueAPF().isNaN()) {
1040 if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo"
1041 return ConstantInt::getFalse(CFP->getContext());
1042 assert(FCmpInst::isUnordered(Pred) &&
1043 "Comparison must be either ordered or unordered!");
1044 // True if unordered.
1045 return ConstantInt::getTrue(CFP->getContext());
1047 // Check whether the constant is an infinity.
1048 if (CFP->getValueAPF().isInfinity()) {
1049 if (CFP->getValueAPF().isNegative()) {
1051 case FCmpInst::FCMP_OLT:
1052 // No value is ordered and less than negative infinity.
1053 return ConstantInt::getFalse(CFP->getContext());
1054 case FCmpInst::FCMP_UGE:
1055 // All values are unordered with or at least negative infinity.
1056 return ConstantInt::getTrue(CFP->getContext());
1062 case FCmpInst::FCMP_OGT:
1063 // No value is ordered and greater than infinity.
1064 return ConstantInt::getFalse(CFP->getContext());
1065 case FCmpInst::FCMP_ULE:
1066 // All values are unordered with and at most infinity.
1067 return ConstantInt::getTrue(CFP->getContext());
1076 // If the comparison is with the result of a select instruction, check whether
1077 // comparing with either branch of the select always yields the same value.
1078 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
1079 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse))
1082 // If the comparison is with the result of a phi instruction, check whether
1083 // doing the compare with each incoming phi value yields a common result.
1084 if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
1085 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse))
1091 Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1092 const TargetData *TD, const DominatorTree *DT) {
1093 return ::SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
1096 /// SimplifySelectInst - Given operands for a SelectInst, see if we can fold
1097 /// the result. If not, this returns null.
1098 Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal,
1099 const TargetData *TD, const DominatorTree *) {
1100 // select true, X, Y -> X
1101 // select false, X, Y -> Y
1102 if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal))
1103 return CB->getZExtValue() ? TrueVal : FalseVal;
1105 // select C, X, X -> X
1106 if (TrueVal == FalseVal)
1109 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
1111 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
1113 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
1114 if (isa<Constant>(TrueVal))
1122 /// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
1123 /// fold the result. If not, this returns null.
1124 Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps,
1125 const TargetData *TD, const DominatorTree *) {
1126 // The type of the GEP pointer operand.
1127 const PointerType *PtrTy = cast<PointerType>(Ops[0]->getType());
1129 // getelementptr P -> P.
1133 if (isa<UndefValue>(Ops[0])) {
1134 // Compute the (pointer) type returned by the GEP instruction.
1135 const Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, &Ops[1],
1137 const Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace());
1138 return UndefValue::get(GEPTy);
1142 // getelementptr P, 0 -> P.
1143 if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1]))
1146 // getelementptr P, N -> P if P points to a type of zero size.
1148 const Type *Ty = PtrTy->getElementType();
1149 if (Ty->isSized() && TD->getTypeAllocSize(Ty) == 0)
1154 // Check to see if this is constant foldable.
1155 for (unsigned i = 0; i != NumOps; ++i)
1156 if (!isa<Constant>(Ops[i]))
1159 return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]),
1160 (Constant *const*)Ops+1, NumOps-1);
1163 /// SimplifyPHINode - See if we can fold the given phi. If not, returns null.
1164 static Value *SimplifyPHINode(PHINode *PN, const DominatorTree *DT) {
1165 // If all of the PHI's incoming values are the same then replace the PHI node
1166 // with the common value.
1167 Value *CommonValue = 0;
1168 bool HasUndefInput = false;
1169 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1170 Value *Incoming = PN->getIncomingValue(i);
1171 // If the incoming value is the phi node itself, it can safely be skipped.
1172 if (Incoming == PN) continue;
1173 if (isa<UndefValue>(Incoming)) {
1174 // Remember that we saw an undef value, but otherwise ignore them.
1175 HasUndefInput = true;
1178 if (CommonValue && Incoming != CommonValue)
1179 return 0; // Not the same, bail out.
1180 CommonValue = Incoming;
1183 // If CommonValue is null then all of the incoming values were either undef or
1184 // equal to the phi node itself.
1186 return UndefValue::get(PN->getType());
1188 // If we have a PHI node like phi(X, undef, X), where X is defined by some
1189 // instruction, we cannot return X as the result of the PHI node unless it
1190 // dominates the PHI block.
1192 return ValueDominatesPHI(CommonValue, PN, DT) ? CommonValue : 0;
1198 //=== Helper functions for higher up the class hierarchy.
1200 /// SimplifyBinOp - Given operands for a BinaryOperator, see if we can
1201 /// fold the result. If not, this returns null.
1202 static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
1203 const TargetData *TD, const DominatorTree *DT,
1204 unsigned MaxRecurse) {
1206 case Instruction::Add: return SimplifyAddInst(LHS, RHS, /* isNSW */ false,
1207 /* isNUW */ false, TD, DT,
1209 case Instruction::Sub: return SimplifySubInst(LHS, RHS, /* isNSW */ false,
1210 /* isNUW */ false, TD, DT,
1212 case Instruction::Mul: return SimplifyMulInst(LHS, RHS, TD, DT, MaxRecurse);
1213 case Instruction::And: return SimplifyAndInst(LHS, RHS, TD, DT, MaxRecurse);
1214 case Instruction::Or: return SimplifyOrInst(LHS, RHS, TD, DT, MaxRecurse);
1215 case Instruction::Xor: return SimplifyXorInst(LHS, RHS, TD, DT, MaxRecurse);
1217 if (Constant *CLHS = dyn_cast<Constant>(LHS))
1218 if (Constant *CRHS = dyn_cast<Constant>(RHS)) {
1219 Constant *COps[] = {CLHS, CRHS};
1220 return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, 2, TD);
1223 // If the operation is associative, try some generic simplifications.
1224 if (Instruction::isAssociative(Opcode))
1225 if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, TD, DT,
1229 // If the operation is with the result of a select instruction, check whether
1230 // operating on either branch of the select always yields the same value.
1231 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
1232 if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, TD, DT,
1236 // If the operation is with the result of a phi instruction, check whether
1237 // operating on all incoming values of the phi always yields the same value.
1238 if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
1239 if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, TD, DT, MaxRecurse))
1246 Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
1247 const TargetData *TD, const DominatorTree *DT) {
1248 return ::SimplifyBinOp(Opcode, LHS, RHS, TD, DT, RecursionLimit);
1251 /// SimplifyCmpInst - Given operands for a CmpInst, see if we can
1252 /// fold the result.
1253 static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1254 const TargetData *TD, const DominatorTree *DT,
1255 unsigned MaxRecurse) {
1256 if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate))
1257 return SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse);
1258 return SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse);
1261 Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1262 const TargetData *TD, const DominatorTree *DT) {
1263 return ::SimplifyCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
1266 /// SimplifyInstruction - See if we can compute a simplified version of this
1267 /// instruction. If not, this returns null.
1268 Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD,
1269 const DominatorTree *DT) {
1272 switch (I->getOpcode()) {
1274 Result = ConstantFoldInstruction(I, TD);
1276 case Instruction::Add:
1277 Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1),
1278 cast<BinaryOperator>(I)->hasNoSignedWrap(),
1279 cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
1282 case Instruction::Sub:
1283 Result = SimplifySubInst(I->getOperand(0), I->getOperand(1),
1284 cast<BinaryOperator>(I)->hasNoSignedWrap(),
1285 cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
1288 case Instruction::Mul:
1289 Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, DT);
1291 case Instruction::And:
1292 Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT);
1294 case Instruction::Or:
1295 Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, DT);
1297 case Instruction::Xor:
1298 Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, DT);
1300 case Instruction::ICmp:
1301 Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
1302 I->getOperand(0), I->getOperand(1), TD, DT);
1304 case Instruction::FCmp:
1305 Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
1306 I->getOperand(0), I->getOperand(1), TD, DT);
1308 case Instruction::Select:
1309 Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1),
1310 I->getOperand(2), TD, DT);
1312 case Instruction::GetElementPtr: {
1313 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
1314 Result = SimplifyGEPInst(&Ops[0], Ops.size(), TD, DT);
1317 case Instruction::PHI:
1318 Result = SimplifyPHINode(cast<PHINode>(I), DT);
1322 /// If called on unreachable code, the above logic may report that the
1323 /// instruction simplified to itself. Make life easier for users by
1324 /// detecting that case here, returning a safe value instead.
1325 return Result == I ? UndefValue::get(I->getType()) : Result;
1328 /// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
1329 /// delete the From instruction. In addition to a basic RAUW, this does a
1330 /// recursive simplification of the newly formed instructions. This catches
1331 /// things where one simplification exposes other opportunities. This only
1332 /// simplifies and deletes scalar operations, it does not change the CFG.
1334 void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
1335 const TargetData *TD,
1336 const DominatorTree *DT) {
1337 assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
1339 // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that
1340 // we can know if it gets deleted out from under us or replaced in a
1341 // recursive simplification.
1342 WeakVH FromHandle(From);
1343 WeakVH ToHandle(To);
1345 while (!From->use_empty()) {
1346 // Update the instruction to use the new value.
1347 Use &TheUse = From->use_begin().getUse();
1348 Instruction *User = cast<Instruction>(TheUse.getUser());
1351 // Check to see if the instruction can be folded due to the operand
1352 // replacement. For example changing (or X, Y) into (or X, -1) can replace
1353 // the 'or' with -1.
1354 Value *SimplifiedVal;
1356 // Sanity check to make sure 'User' doesn't dangle across
1357 // SimplifyInstruction.
1358 AssertingVH<> UserHandle(User);
1360 SimplifiedVal = SimplifyInstruction(User, TD, DT);
1361 if (SimplifiedVal == 0) continue;
1364 // Recursively simplify this user to the new value.
1365 ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD, DT);
1366 From = dyn_cast_or_null<Instruction>((Value*)FromHandle);
1369 assert(ToHandle && "To value deleted by recursive simplification?");
1371 // If the recursive simplification ended up revisiting and deleting
1372 // 'From' then we're done.
1377 // If 'From' has value handles referring to it, do a real RAUW to update them.
1378 From->replaceAllUsesWith(To);
1380 From->eraseFromParent();