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 OpcToExpand, const TargetData *TD,
75 const DominatorTree *DT, unsigned MaxRecurse) {
76 Instruction::BinaryOps OpcodeToExpand = (Instruction::BinaryOps)OpcToExpand;
77 // Recursion is always used, so bail out at once if we already hit the limit.
81 // Check whether the expression has the form "(A op' B) op C".
82 if (BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS))
83 if (Op0->getOpcode() == OpcodeToExpand) {
84 // It does! Try turning it into "(A op C) op' (B op C)".
85 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS;
86 // Do "A op C" and "B op C" both simplify?
87 if (Value *L = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse))
88 if (Value *R = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) {
89 // They do! Return "L op' R" if it simplifies or is already available.
90 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS.
91 if ((L == A && R == B) || (Instruction::isCommutative(OpcodeToExpand)
92 && L == B && R == A)) {
96 // Otherwise return "L op' R" if it simplifies.
97 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT,
105 // Check whether the expression has the form "A op (B op' C)".
106 if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS))
107 if (Op1->getOpcode() == OpcodeToExpand) {
108 // It does! Try turning it into "(A op B) op' (A op C)".
109 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1);
110 // Do "A op B" and "A op C" both simplify?
111 if (Value *L = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse))
112 if (Value *R = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse)) {
113 // They do! Return "L op' R" if it simplifies or is already available.
114 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS.
115 if ((L == B && R == C) || (Instruction::isCommutative(OpcodeToExpand)
116 && L == C && R == B)) {
120 // Otherwise return "L op' R" if it simplifies.
121 if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT,
132 /// FactorizeBinOp - Simplify "LHS Opcode RHS" by factorizing out a common term
133 /// using the operation OpCodeToExtract. For example, when Opcode is Add and
134 /// OpCodeToExtract is Mul then this tries to turn "(A*B)+(A*C)" into "A*(B+C)".
135 /// Returns the simplified value, or null if no simplification was performed.
136 static Value *FactorizeBinOp(unsigned Opcode, Value *LHS, Value *RHS,
137 unsigned OpcToExtract, const TargetData *TD,
138 const DominatorTree *DT, unsigned MaxRecurse) {
139 Instruction::BinaryOps OpcodeToExtract = (Instruction::BinaryOps)OpcToExtract;
140 // Recursion is always used, so bail out at once if we already hit the limit.
144 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
145 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
147 if (!Op0 || Op0->getOpcode() != OpcodeToExtract ||
148 !Op1 || Op1->getOpcode() != OpcodeToExtract)
151 // The expression has the form "(A op' B) op (C op' D)".
152 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1);
153 Value *C = Op1->getOperand(0), *D = Op1->getOperand(1);
155 // Use left distributivity, i.e. "X op' (Y op Z) = (X op' Y) op (X op' Z)".
156 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the
157 // commutative case, "(A op' B) op (C op' A)"?
158 if (A == C || (Instruction::isCommutative(OpcodeToExtract) && A == D)) {
159 Value *DD = A == C ? D : C;
160 // Form "A op' (B op DD)" if it simplifies completely.
161 // Does "B op DD" simplify?
162 if (Value *V = SimplifyBinOp(Opcode, B, DD, TD, DT, MaxRecurse)) {
163 // It does! Return "A op' V" if it simplifies or is already available.
164 // If V equals B then "A op' V" is just the LHS. If V equals DD then
165 // "A op' V" is just the RHS.
166 if (V == B || V == DD) {
168 return V == B ? LHS : RHS;
170 // Otherwise return "A op' V" if it simplifies.
171 if (Value *W = SimplifyBinOp(OpcodeToExtract, A, V, TD, DT, MaxRecurse)) {
178 // Use right distributivity, i.e. "(X op Y) op' Z = (X op' Z) op (Y op' Z)".
179 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the
180 // commutative case, "(A op' B) op (B op' D)"?
181 if (B == D || (Instruction::isCommutative(OpcodeToExtract) && B == C)) {
182 Value *CC = B == D ? C : D;
183 // Form "(A op CC) op' B" if it simplifies completely..
184 // Does "A op CC" simplify?
185 if (Value *V = SimplifyBinOp(Opcode, A, CC, TD, DT, MaxRecurse)) {
186 // It does! Return "V op' B" if it simplifies or is already available.
187 // If V equals A then "V op' B" is just the LHS. If V equals CC then
188 // "V op' B" is just the RHS.
189 if (V == A || V == CC) {
191 return V == A ? LHS : RHS;
193 // Otherwise return "V op' B" if it simplifies.
194 if (Value *W = SimplifyBinOp(OpcodeToExtract, V, B, TD, DT, MaxRecurse)) {
204 /// SimplifyAssociativeBinOp - Generic simplifications for associative binary
205 /// operations. Returns the simpler value, or null if none was found.
206 static Value *SimplifyAssociativeBinOp(unsigned Opc, Value *LHS, Value *RHS,
207 const TargetData *TD,
208 const DominatorTree *DT,
209 unsigned MaxRecurse) {
210 Instruction::BinaryOps Opcode = (Instruction::BinaryOps)Opc;
211 assert(Instruction::isAssociative(Opcode) && "Not an associative operation!");
213 // Recursion is always used, so bail out at once if we already hit the limit.
217 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
218 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
220 // Transform: "(A op B) op C" ==> "A op (B op C)" if it simplifies completely.
221 if (Op0 && Op0->getOpcode() == Opcode) {
222 Value *A = Op0->getOperand(0);
223 Value *B = Op0->getOperand(1);
226 // Does "B op C" simplify?
227 if (Value *V = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) {
228 // It does! Return "A op V" if it simplifies or is already available.
229 // If V equals B then "A op V" is just the LHS.
230 if (V == B) return LHS;
231 // Otherwise return "A op V" if it simplifies.
232 if (Value *W = SimplifyBinOp(Opcode, A, V, TD, DT, MaxRecurse)) {
239 // Transform: "A op (B op C)" ==> "(A op B) op C" if it simplifies completely.
240 if (Op1 && Op1->getOpcode() == Opcode) {
242 Value *B = Op1->getOperand(0);
243 Value *C = Op1->getOperand(1);
245 // Does "A op B" simplify?
246 if (Value *V = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse)) {
247 // It does! Return "V op C" if it simplifies or is already available.
248 // If V equals B then "V op C" is just the RHS.
249 if (V == B) return RHS;
250 // Otherwise return "V op C" if it simplifies.
251 if (Value *W = SimplifyBinOp(Opcode, V, C, TD, DT, MaxRecurse)) {
258 // The remaining transforms require commutativity as well as associativity.
259 if (!Instruction::isCommutative(Opcode))
262 // Transform: "(A op B) op C" ==> "(C op A) op B" if it simplifies completely.
263 if (Op0 && Op0->getOpcode() == Opcode) {
264 Value *A = Op0->getOperand(0);
265 Value *B = Op0->getOperand(1);
268 // Does "C op A" simplify?
269 if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) {
270 // It does! Return "V op B" if it simplifies or is already available.
271 // If V equals A then "V op B" is just the LHS.
272 if (V == A) return LHS;
273 // Otherwise return "V op B" if it simplifies.
274 if (Value *W = SimplifyBinOp(Opcode, V, B, TD, DT, MaxRecurse)) {
281 // Transform: "A op (B op C)" ==> "B op (C op A)" if it simplifies completely.
282 if (Op1 && Op1->getOpcode() == Opcode) {
284 Value *B = Op1->getOperand(0);
285 Value *C = Op1->getOperand(1);
287 // Does "C op A" simplify?
288 if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) {
289 // It does! Return "B op V" if it simplifies or is already available.
290 // If V equals C then "B op V" is just the RHS.
291 if (V == C) return RHS;
292 // Otherwise return "B op V" if it simplifies.
293 if (Value *W = SimplifyBinOp(Opcode, B, V, TD, DT, MaxRecurse)) {
303 /// ThreadBinOpOverSelect - In the case of a binary operation with a select
304 /// instruction as an operand, try to simplify the binop by seeing whether
305 /// evaluating it on both branches of the select results in the same value.
306 /// Returns the common value if so, otherwise returns null.
307 static Value *ThreadBinOpOverSelect(unsigned Opcode, Value *LHS, Value *RHS,
308 const TargetData *TD,
309 const DominatorTree *DT,
310 unsigned MaxRecurse) {
311 // Recursion is always used, so bail out at once if we already hit the limit.
316 if (isa<SelectInst>(LHS)) {
317 SI = cast<SelectInst>(LHS);
319 assert(isa<SelectInst>(RHS) && "No select instruction operand!");
320 SI = cast<SelectInst>(RHS);
323 // Evaluate the BinOp on the true and false branches of the select.
327 TV = SimplifyBinOp(Opcode, SI->getTrueValue(), RHS, TD, DT, MaxRecurse);
328 FV = SimplifyBinOp(Opcode, SI->getFalseValue(), RHS, TD, DT, MaxRecurse);
330 TV = SimplifyBinOp(Opcode, LHS, SI->getTrueValue(), TD, DT, MaxRecurse);
331 FV = SimplifyBinOp(Opcode, LHS, SI->getFalseValue(), TD, DT, MaxRecurse);
334 // If they simplified to the same value, then return the common value.
335 // If they both failed to simplify then return null.
339 // If one branch simplified to undef, return the other one.
340 if (TV && isa<UndefValue>(TV))
342 if (FV && isa<UndefValue>(FV))
345 // If applying the operation did not change the true and false select values,
346 // then the result of the binop is the select itself.
347 if (TV == SI->getTrueValue() && FV == SI->getFalseValue())
350 // If one branch simplified and the other did not, and the simplified
351 // value is equal to the unsimplified one, return the simplified value.
352 // For example, select (cond, X, X & Z) & Z -> X & Z.
353 if ((FV && !TV) || (TV && !FV)) {
354 // Check that the simplified value has the form "X op Y" where "op" is the
355 // same as the original operation.
356 Instruction *Simplified = dyn_cast<Instruction>(FV ? FV : TV);
357 if (Simplified && Simplified->getOpcode() == Opcode) {
358 // The value that didn't simplify is "UnsimplifiedLHS op UnsimplifiedRHS".
359 // We already know that "op" is the same as for the simplified value. See
360 // if the operands match too. If so, return the simplified value.
361 Value *UnsimplifiedBranch = FV ? SI->getTrueValue() : SI->getFalseValue();
362 Value *UnsimplifiedLHS = SI == LHS ? UnsimplifiedBranch : LHS;
363 Value *UnsimplifiedRHS = SI == LHS ? RHS : UnsimplifiedBranch;
364 if (Simplified->getOperand(0) == UnsimplifiedLHS &&
365 Simplified->getOperand(1) == UnsimplifiedRHS)
367 if (Simplified->isCommutative() &&
368 Simplified->getOperand(1) == UnsimplifiedLHS &&
369 Simplified->getOperand(0) == UnsimplifiedRHS)
377 /// ThreadCmpOverSelect - In the case of a comparison with a select instruction,
378 /// try to simplify the comparison by seeing whether both branches of the select
379 /// result in the same value. Returns the common value if so, otherwise returns
381 static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS,
382 Value *RHS, const TargetData *TD,
383 const DominatorTree *DT,
384 unsigned MaxRecurse) {
385 // Recursion is always used, so bail out at once if we already hit the limit.
389 // Make sure the select is on the LHS.
390 if (!isa<SelectInst>(LHS)) {
392 Pred = CmpInst::getSwappedPredicate(Pred);
394 assert(isa<SelectInst>(LHS) && "Not comparing with a select instruction!");
395 SelectInst *SI = cast<SelectInst>(LHS);
397 // Now that we have "cmp select(cond, TV, FV), RHS", analyse it.
398 // Does "cmp TV, RHS" simplify?
399 if (Value *TCmp = SimplifyCmpInst(Pred, SI->getTrueValue(), RHS, TD, DT,
401 // It does! Does "cmp FV, RHS" simplify?
402 if (Value *FCmp = SimplifyCmpInst(Pred, SI->getFalseValue(), RHS, TD, DT,
404 // It does! If they simplified to the same value, then use it as the
405 // result of the original comparison.
411 /// ThreadBinOpOverPHI - In the case of a binary operation with an operand that
412 /// is a PHI instruction, try to simplify the binop by seeing whether evaluating
413 /// it on the incoming phi values yields the same result for every value. If so
414 /// returns the common value, otherwise returns null.
415 static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS,
416 const TargetData *TD, const DominatorTree *DT,
417 unsigned MaxRecurse) {
418 // Recursion is always used, so bail out at once if we already hit the limit.
423 if (isa<PHINode>(LHS)) {
424 PI = cast<PHINode>(LHS);
425 // Bail out if RHS and the phi may be mutually interdependent due to a loop.
426 if (!ValueDominatesPHI(RHS, PI, DT))
429 assert(isa<PHINode>(RHS) && "No PHI instruction operand!");
430 PI = cast<PHINode>(RHS);
431 // Bail out if LHS and the phi may be mutually interdependent due to a loop.
432 if (!ValueDominatesPHI(LHS, PI, DT))
436 // Evaluate the BinOp on the incoming phi values.
437 Value *CommonValue = 0;
438 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
439 Value *Incoming = PI->getIncomingValue(i);
440 // If the incoming value is the phi node itself, it can safely be skipped.
441 if (Incoming == PI) continue;
442 Value *V = PI == LHS ?
443 SimplifyBinOp(Opcode, Incoming, RHS, TD, DT, MaxRecurse) :
444 SimplifyBinOp(Opcode, LHS, Incoming, TD, DT, MaxRecurse);
445 // If the operation failed to simplify, or simplified to a different value
446 // to previously, then give up.
447 if (!V || (CommonValue && V != CommonValue))
455 /// ThreadCmpOverPHI - In the case of a comparison with a PHI instruction, try
456 /// try to simplify the comparison by seeing whether comparing with all of the
457 /// incoming phi values yields the same result every time. If so returns the
458 /// common result, otherwise returns null.
459 static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS,
460 const TargetData *TD, const DominatorTree *DT,
461 unsigned MaxRecurse) {
462 // Recursion is always used, so bail out at once if we already hit the limit.
466 // Make sure the phi is on the LHS.
467 if (!isa<PHINode>(LHS)) {
469 Pred = CmpInst::getSwappedPredicate(Pred);
471 assert(isa<PHINode>(LHS) && "Not comparing with a phi instruction!");
472 PHINode *PI = cast<PHINode>(LHS);
474 // Bail out if RHS and the phi may be mutually interdependent due to a loop.
475 if (!ValueDominatesPHI(RHS, PI, DT))
478 // Evaluate the BinOp on the incoming phi values.
479 Value *CommonValue = 0;
480 for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
481 Value *Incoming = PI->getIncomingValue(i);
482 // If the incoming value is the phi node itself, it can safely be skipped.
483 if (Incoming == PI) continue;
484 Value *V = SimplifyCmpInst(Pred, Incoming, RHS, TD, DT, MaxRecurse);
485 // If the operation failed to simplify, or simplified to a different value
486 // to previously, then give up.
487 if (!V || (CommonValue && V != CommonValue))
495 /// SimplifyAddInst - Given operands for an Add, see if we can
496 /// fold the result. If not, this returns null.
497 static Value *SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
498 const TargetData *TD, const DominatorTree *DT,
499 unsigned MaxRecurse) {
500 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
501 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
502 Constant *Ops[] = { CLHS, CRHS };
503 return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(),
507 // Canonicalize the constant to the RHS.
511 // X + undef -> undef
512 if (isa<UndefValue>(Op1))
516 if (match(Op1, m_Zero()))
523 if (match(Op1, m_Sub(m_Value(Y), m_Specific(Op0))) ||
524 match(Op0, m_Sub(m_Value(Y), m_Specific(Op1))))
527 // X + ~X -> -1 since ~X = -X-1
528 if (match(Op0, m_Not(m_Specific(Op1))) ||
529 match(Op1, m_Not(m_Specific(Op0))))
530 return Constant::getAllOnesValue(Op0->getType());
533 if (MaxRecurse && Op0->getType()->isIntegerTy(1))
534 if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1))
537 // Try some generic simplifications for associative operations.
538 if (Value *V = SimplifyAssociativeBinOp(Instruction::Add, Op0, Op1, TD, DT,
542 // Mul distributes over Add. Try some generic simplifications based on this.
543 if (Value *V = FactorizeBinOp(Instruction::Add, Op0, Op1, Instruction::Mul,
547 // Threading Add over selects and phi nodes is pointless, so don't bother.
548 // Threading over the select in "A + select(cond, B, C)" means evaluating
549 // "A+B" and "A+C" and seeing if they are equal; but they are equal if and
550 // only if B and C are equal. If B and C are equal then (since we assume
551 // that operands have already been simplified) "select(cond, B, C)" should
552 // have been simplified to the common value of B and C already. Analysing
553 // "A+B" and "A+C" thus gains nothing, but costs compile time. Similarly
554 // for threading over phi nodes.
559 Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
560 const TargetData *TD, const DominatorTree *DT) {
561 return ::SimplifyAddInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit);
564 /// SimplifySubInst - Given operands for a Sub, see if we can
565 /// fold the result. If not, this returns null.
566 static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
567 const TargetData *TD, const DominatorTree *DT,
568 unsigned MaxRecurse) {
569 if (Constant *CLHS = dyn_cast<Constant>(Op0))
570 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
571 Constant *Ops[] = { CLHS, CRHS };
572 return ConstantFoldInstOperands(Instruction::Sub, CLHS->getType(),
576 // X - undef -> undef
577 // undef - X -> undef
578 if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1))
579 return UndefValue::get(Op0->getType());
582 if (match(Op1, m_Zero()))
587 return Constant::getNullValue(Op0->getType());
592 if (match(Op0, m_Add(m_Value(X), m_Specific(Op1))) ||
593 match(Op0, m_Add(m_Specific(Op1), m_Value(X))))
597 if (MaxRecurse && Op0->getType()->isIntegerTy(1))
598 if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1))
601 // X - (X - Y) -> Y. More generally Z - (X - Y) -> (Z - X) + Y if everything
603 Value *Y = 0, *Z = Op0;
604 if (MaxRecurse && match(Op1, m_Sub(m_Value(X), m_Value(Y)))) // Z - (X - Y)
605 // See if "V === Z - X" simplifies.
606 if (Value *V = SimplifyBinOp(Instruction::Sub, Z, X, TD, DT, MaxRecurse-1))
607 // It does! Now see if "W === V + Y" simplifies.
608 if (Value *W = SimplifyBinOp(Instruction::Add, V, Y, TD, DT,
610 // It does, we successfully reassociated!
615 // Mul distributes over Sub. Try some generic simplifications based on this.
616 if (Value *V = FactorizeBinOp(Instruction::Sub, Op0, Op1, Instruction::Mul,
620 // Threading Sub over selects and phi nodes is pointless, so don't bother.
621 // Threading over the select in "A - select(cond, B, C)" means evaluating
622 // "A-B" and "A-C" and seeing if they are equal; but they are equal if and
623 // only if B and C are equal. If B and C are equal then (since we assume
624 // that operands have already been simplified) "select(cond, B, C)" should
625 // have been simplified to the common value of B and C already. Analysing
626 // "A-B" and "A-C" thus gains nothing, but costs compile time. Similarly
627 // for threading over phi nodes.
632 Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
633 const TargetData *TD, const DominatorTree *DT) {
634 return ::SimplifySubInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit);
637 /// SimplifyMulInst - Given operands for a Mul, see if we can
638 /// fold the result. If not, this returns null.
639 static Value *SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
640 const DominatorTree *DT, unsigned MaxRecurse) {
641 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
642 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
643 Constant *Ops[] = { CLHS, CRHS };
644 return ConstantFoldInstOperands(Instruction::Mul, CLHS->getType(),
648 // Canonicalize the constant to the RHS.
653 if (isa<UndefValue>(Op1))
654 return Constant::getNullValue(Op0->getType());
657 if (match(Op1, m_Zero()))
661 if (match(Op1, m_One()))
665 if (MaxRecurse && Op0->getType()->isIntegerTy(1))
666 if (Value *V = SimplifyAndInst(Op0, Op1, TD, DT, MaxRecurse-1))
669 // Try some generic simplifications for associative operations.
670 if (Value *V = SimplifyAssociativeBinOp(Instruction::Mul, Op0, Op1, TD, DT,
674 // Mul distributes over Add. Try some generic simplifications based on this.
675 if (Value *V = ExpandBinOp(Instruction::Mul, Op0, Op1, Instruction::Add,
679 // If the operation is with the result of a select instruction, check whether
680 // operating on either branch of the select always yields the same value.
681 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
682 if (Value *V = ThreadBinOpOverSelect(Instruction::Mul, Op0, Op1, TD, DT,
686 // If the operation is with the result of a phi instruction, check whether
687 // operating on all incoming values of the phi always yields the same value.
688 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
689 if (Value *V = ThreadBinOpOverPHI(Instruction::Mul, Op0, Op1, TD, DT,
696 Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
697 const DominatorTree *DT) {
698 return ::SimplifyMulInst(Op0, Op1, TD, DT, RecursionLimit);
701 /// SimplifyShift - Given operands for an Shl, LShr or AShr, see if we can
702 /// fold the result. If not, this returns null.
703 static Value *SimplifyShift(unsigned Opcode, Value *Op0, Value *Op1,
704 const TargetData *TD, const DominatorTree *DT,
705 unsigned MaxRecurse) {
706 if (Constant *C0 = dyn_cast<Constant>(Op0)) {
707 if (Constant *C1 = dyn_cast<Constant>(Op1)) {
708 Constant *Ops[] = { C0, C1 };
709 return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, 2, TD);
714 if (match(Op0, m_Zero()))
718 if (match(Op1, m_Zero()))
721 // X shift by undef -> undef because it may shift by the bitwidth.
722 if (isa<UndefValue>(Op1))
725 // Shifting by the bitwidth or more is undefined.
726 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1))
727 if (CI->getValue().getLimitedValue() >=
728 Op0->getType()->getScalarSizeInBits())
729 return UndefValue::get(Op0->getType());
731 // If the operation is with the result of a select instruction, check whether
732 // operating on either branch of the select always yields the same value.
733 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
734 if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, TD, DT, MaxRecurse))
737 // If the operation is with the result of a phi instruction, check whether
738 // operating on all incoming values of the phi always yields the same value.
739 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
740 if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, TD, DT, MaxRecurse))
746 /// SimplifyShlInst - Given operands for an Shl, see if we can
747 /// fold the result. If not, this returns null.
748 static Value *SimplifyShlInst(Value *Op0, Value *Op1, const TargetData *TD,
749 const DominatorTree *DT, unsigned MaxRecurse) {
750 if (Value *V = SimplifyShift(Instruction::Shl, Op0, Op1, TD, DT, MaxRecurse))
754 if (isa<UndefValue>(Op0))
755 return Constant::getNullValue(Op0->getType());
760 Value *llvm::SimplifyShlInst(Value *Op0, Value *Op1, const TargetData *TD,
761 const DominatorTree *DT) {
762 return ::SimplifyShlInst(Op0, Op1, TD, DT, RecursionLimit);
765 /// SimplifyLShrInst - Given operands for an LShr, see if we can
766 /// fold the result. If not, this returns null.
767 static Value *SimplifyLShrInst(Value *Op0, Value *Op1, const TargetData *TD,
768 const DominatorTree *DT, unsigned MaxRecurse) {
769 if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, TD, DT, MaxRecurse))
773 if (isa<UndefValue>(Op0))
774 return Constant::getNullValue(Op0->getType());
779 Value *llvm::SimplifyLShrInst(Value *Op0, Value *Op1, const TargetData *TD,
780 const DominatorTree *DT) {
781 return ::SimplifyLShrInst(Op0, Op1, TD, DT, RecursionLimit);
784 /// SimplifyAShrInst - Given operands for an AShr, see if we can
785 /// fold the result. If not, this returns null.
786 static Value *SimplifyAShrInst(Value *Op0, Value *Op1, const TargetData *TD,
787 const DominatorTree *DT, unsigned MaxRecurse) {
788 if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, TD, DT, MaxRecurse))
791 // all ones >>a X -> all ones
792 if (match(Op0, m_AllOnes()))
795 // undef >>a X -> all ones
796 if (isa<UndefValue>(Op0))
797 return Constant::getAllOnesValue(Op0->getType());
802 Value *llvm::SimplifyAShrInst(Value *Op0, Value *Op1, const TargetData *TD,
803 const DominatorTree *DT) {
804 return ::SimplifyAShrInst(Op0, Op1, TD, DT, RecursionLimit);
807 /// SimplifyAndInst - Given operands for an And, see if we can
808 /// fold the result. If not, this returns null.
809 static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
810 const DominatorTree *DT, unsigned MaxRecurse) {
811 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
812 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
813 Constant *Ops[] = { CLHS, CRHS };
814 return ConstantFoldInstOperands(Instruction::And, CLHS->getType(),
818 // Canonicalize the constant to the RHS.
823 if (isa<UndefValue>(Op1))
824 return Constant::getNullValue(Op0->getType());
831 if (match(Op1, m_Zero()))
835 if (match(Op1, m_AllOnes()))
838 // A & ~A = ~A & A = 0
839 Value *A = 0, *B = 0;
840 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
841 (match(Op1, m_Not(m_Value(A))) && A == Op0))
842 return Constant::getNullValue(Op0->getType());
845 if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
846 (A == Op1 || B == Op1))
850 if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
851 (A == Op0 || B == Op0))
854 // Try some generic simplifications for associative operations.
855 if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, TD, DT,
859 // And distributes over Or. Try some generic simplifications based on this.
860 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Or,
864 // And distributes over Xor. Try some generic simplifications based on this.
865 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Xor,
869 // Or distributes over And. Try some generic simplifications based on this.
870 if (Value *V = FactorizeBinOp(Instruction::And, Op0, Op1, Instruction::Or,
874 // If the operation is with the result of a select instruction, check whether
875 // operating on either branch of the select always yields the same value.
876 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
877 if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, TD, DT,
881 // If the operation is with the result of a phi instruction, check whether
882 // operating on all incoming values of the phi always yields the same value.
883 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
884 if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, TD, DT,
891 Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
892 const DominatorTree *DT) {
893 return ::SimplifyAndInst(Op0, Op1, TD, DT, RecursionLimit);
896 /// SimplifyOrInst - Given operands for an Or, see if we can
897 /// fold the result. If not, this returns null.
898 static Value *SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
899 const DominatorTree *DT, unsigned MaxRecurse) {
900 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
901 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
902 Constant *Ops[] = { CLHS, CRHS };
903 return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(),
907 // Canonicalize the constant to the RHS.
912 if (isa<UndefValue>(Op1))
913 return Constant::getAllOnesValue(Op0->getType());
920 if (match(Op1, m_Zero()))
924 if (match(Op1, m_AllOnes()))
927 // A | ~A = ~A | A = -1
928 Value *A = 0, *B = 0;
929 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
930 (match(Op1, m_Not(m_Value(A))) && A == Op0))
931 return Constant::getAllOnesValue(Op0->getType());
934 if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
935 (A == Op1 || B == Op1))
939 if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
940 (A == Op0 || B == Op0))
943 // Try some generic simplifications for associative operations.
944 if (Value *V = SimplifyAssociativeBinOp(Instruction::Or, Op0, Op1, TD, DT,
948 // Or distributes over And. Try some generic simplifications based on this.
949 if (Value *V = ExpandBinOp(Instruction::Or, Op0, Op1, Instruction::And,
953 // And distributes over Or. Try some generic simplifications based on this.
954 if (Value *V = FactorizeBinOp(Instruction::Or, Op0, Op1, Instruction::And,
958 // If the operation is with the result of a select instruction, check whether
959 // operating on either branch of the select always yields the same value.
960 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
961 if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, TD, DT,
965 // If the operation is with the result of a phi instruction, check whether
966 // operating on all incoming values of the phi always yields the same value.
967 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
968 if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, TD, DT,
975 Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
976 const DominatorTree *DT) {
977 return ::SimplifyOrInst(Op0, Op1, TD, DT, RecursionLimit);
980 /// SimplifyXorInst - Given operands for a Xor, see if we can
981 /// fold the result. If not, this returns null.
982 static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
983 const DominatorTree *DT, unsigned MaxRecurse) {
984 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
985 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
986 Constant *Ops[] = { CLHS, CRHS };
987 return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(),
991 // Canonicalize the constant to the RHS.
995 // A ^ undef -> undef
996 if (isa<UndefValue>(Op1))
1000 if (match(Op1, m_Zero()))
1005 return Constant::getNullValue(Op0->getType());
1007 // A ^ ~A = ~A ^ A = -1
1009 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
1010 (match(Op1, m_Not(m_Value(A))) && A == Op0))
1011 return Constant::getAllOnesValue(Op0->getType());
1013 // Try some generic simplifications for associative operations.
1014 if (Value *V = SimplifyAssociativeBinOp(Instruction::Xor, Op0, Op1, TD, DT,
1018 // And distributes over Xor. Try some generic simplifications based on this.
1019 if (Value *V = FactorizeBinOp(Instruction::Xor, Op0, Op1, Instruction::And,
1020 TD, DT, MaxRecurse))
1023 // Threading Xor over selects and phi nodes is pointless, so don't bother.
1024 // Threading over the select in "A ^ select(cond, B, C)" means evaluating
1025 // "A^B" and "A^C" and seeing if they are equal; but they are equal if and
1026 // only if B and C are equal. If B and C are equal then (since we assume
1027 // that operands have already been simplified) "select(cond, B, C)" should
1028 // have been simplified to the common value of B and C already. Analysing
1029 // "A^B" and "A^C" thus gains nothing, but costs compile time. Similarly
1030 // for threading over phi nodes.
1035 Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
1036 const DominatorTree *DT) {
1037 return ::SimplifyXorInst(Op0, Op1, TD, DT, RecursionLimit);
1040 static const Type *GetCompareTy(Value *Op) {
1041 return CmpInst::makeCmpResultType(Op->getType());
1044 /// SimplifyICmpInst - Given operands for an ICmpInst, see if we can
1045 /// fold the result. If not, this returns null.
1046 static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1047 const TargetData *TD, const DominatorTree *DT,
1048 unsigned MaxRecurse) {
1049 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
1050 assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!");
1052 if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
1053 if (Constant *CRHS = dyn_cast<Constant>(RHS))
1054 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD);
1056 // If we have a constant, make sure it is on the RHS.
1057 std::swap(LHS, RHS);
1058 Pred = CmpInst::getSwappedPredicate(Pred);
1061 const Type *ITy = GetCompareTy(LHS); // The return type.
1062 const Type *OpTy = LHS->getType(); // The operand type.
1064 // icmp X, X -> true/false
1065 // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false
1066 // because X could be 0.
1067 if (LHS == RHS || isa<UndefValue>(RHS))
1068 return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred));
1070 // Special case logic when the operands have i1 type.
1071 if (OpTy->isIntegerTy(1) || (OpTy->isVectorTy() &&
1072 cast<VectorType>(OpTy)->getElementType()->isIntegerTy(1))) {
1075 case ICmpInst::ICMP_EQ:
1077 if (match(RHS, m_One()))
1080 case ICmpInst::ICMP_NE:
1082 if (match(RHS, m_Zero()))
1085 case ICmpInst::ICMP_UGT:
1087 if (match(RHS, m_Zero()))
1090 case ICmpInst::ICMP_UGE:
1092 if (match(RHS, m_One()))
1095 case ICmpInst::ICMP_SLT:
1097 if (match(RHS, m_Zero()))
1100 case ICmpInst::ICMP_SLE:
1102 if (match(RHS, m_One()))
1108 // See if we are doing a comparison with a constant.
1109 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
1112 case ICmpInst::ICMP_UGT:
1113 if (CI->isMaxValue(false)) // A >u MAX -> FALSE
1114 return ConstantInt::getFalse(CI->getContext());
1116 case ICmpInst::ICMP_UGE:
1117 if (CI->isMinValue(false)) // A >=u MIN -> TRUE
1118 return ConstantInt::getTrue(CI->getContext());
1120 case ICmpInst::ICMP_ULT:
1121 if (CI->isMinValue(false)) // A <u MIN -> FALSE
1122 return ConstantInt::getFalse(CI->getContext());
1124 case ICmpInst::ICMP_ULE:
1125 if (CI->isMaxValue(false)) // A <=u MAX -> TRUE
1126 return ConstantInt::getTrue(CI->getContext());
1128 case ICmpInst::ICMP_SGT:
1129 if (CI->isMaxValue(true)) // A >s MAX -> FALSE
1130 return ConstantInt::getFalse(CI->getContext());
1132 case ICmpInst::ICMP_SGE:
1133 if (CI->isMinValue(true)) // A >=s MIN -> TRUE
1134 return ConstantInt::getTrue(CI->getContext());
1136 case ICmpInst::ICMP_SLT:
1137 if (CI->isMinValue(true)) // A <s MIN -> FALSE
1138 return ConstantInt::getFalse(CI->getContext());
1140 case ICmpInst::ICMP_SLE:
1141 if (CI->isMaxValue(true)) // A <=s MAX -> TRUE
1142 return ConstantInt::getTrue(CI->getContext());
1147 // icmp <alloca*>, <global/alloca*/null> - Different stack variables have
1148 // different addresses, and what's more the address of a stack variable is
1149 // never null or equal to the address of a global. Note that generalizing
1150 // to the case where LHS is a global variable address or null is pointless,
1151 // since if both LHS and RHS are constants then we already constant folded
1152 // the compare, and if only one of them is then we moved it to RHS already.
1153 if (isa<AllocaInst>(LHS) && (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) ||
1154 isa<ConstantPointerNull>(RHS)))
1155 // We already know that LHS != LHS.
1156 return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
1158 // If the comparison is with the result of a select instruction, check whether
1159 // comparing with either branch of the select always yields the same value.
1160 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
1161 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse))
1164 // If the comparison is with the result of a phi instruction, check whether
1165 // doing the compare with each incoming phi value yields a common result.
1166 if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
1167 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse))
1173 Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1174 const TargetData *TD, const DominatorTree *DT) {
1175 return ::SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
1178 /// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can
1179 /// fold the result. If not, this returns null.
1180 static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1181 const TargetData *TD, const DominatorTree *DT,
1182 unsigned MaxRecurse) {
1183 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
1184 assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!");
1186 if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
1187 if (Constant *CRHS = dyn_cast<Constant>(RHS))
1188 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD);
1190 // If we have a constant, make sure it is on the RHS.
1191 std::swap(LHS, RHS);
1192 Pred = CmpInst::getSwappedPredicate(Pred);
1195 // Fold trivial predicates.
1196 if (Pred == FCmpInst::FCMP_FALSE)
1197 return ConstantInt::get(GetCompareTy(LHS), 0);
1198 if (Pred == FCmpInst::FCMP_TRUE)
1199 return ConstantInt::get(GetCompareTy(LHS), 1);
1201 if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef
1202 return UndefValue::get(GetCompareTy(LHS));
1204 // fcmp x,x -> true/false. Not all compares are foldable.
1206 if (CmpInst::isTrueWhenEqual(Pred))
1207 return ConstantInt::get(GetCompareTy(LHS), 1);
1208 if (CmpInst::isFalseWhenEqual(Pred))
1209 return ConstantInt::get(GetCompareTy(LHS), 0);
1212 // Handle fcmp with constant RHS
1213 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
1214 // If the constant is a nan, see if we can fold the comparison based on it.
1215 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
1216 if (CFP->getValueAPF().isNaN()) {
1217 if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo"
1218 return ConstantInt::getFalse(CFP->getContext());
1219 assert(FCmpInst::isUnordered(Pred) &&
1220 "Comparison must be either ordered or unordered!");
1221 // True if unordered.
1222 return ConstantInt::getTrue(CFP->getContext());
1224 // Check whether the constant is an infinity.
1225 if (CFP->getValueAPF().isInfinity()) {
1226 if (CFP->getValueAPF().isNegative()) {
1228 case FCmpInst::FCMP_OLT:
1229 // No value is ordered and less than negative infinity.
1230 return ConstantInt::getFalse(CFP->getContext());
1231 case FCmpInst::FCMP_UGE:
1232 // All values are unordered with or at least negative infinity.
1233 return ConstantInt::getTrue(CFP->getContext());
1239 case FCmpInst::FCMP_OGT:
1240 // No value is ordered and greater than infinity.
1241 return ConstantInt::getFalse(CFP->getContext());
1242 case FCmpInst::FCMP_ULE:
1243 // All values are unordered with and at most infinity.
1244 return ConstantInt::getTrue(CFP->getContext());
1253 // If the comparison is with the result of a select instruction, check whether
1254 // comparing with either branch of the select always yields the same value.
1255 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
1256 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse))
1259 // If the comparison is with the result of a phi instruction, check whether
1260 // doing the compare with each incoming phi value yields a common result.
1261 if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
1262 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse))
1268 Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1269 const TargetData *TD, const DominatorTree *DT) {
1270 return ::SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
1273 /// SimplifySelectInst - Given operands for a SelectInst, see if we can fold
1274 /// the result. If not, this returns null.
1275 Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal,
1276 const TargetData *TD, const DominatorTree *) {
1277 // select true, X, Y -> X
1278 // select false, X, Y -> Y
1279 if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal))
1280 return CB->getZExtValue() ? TrueVal : FalseVal;
1282 // select C, X, X -> X
1283 if (TrueVal == FalseVal)
1286 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
1288 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
1290 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
1291 if (isa<Constant>(TrueVal))
1299 /// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
1300 /// fold the result. If not, this returns null.
1301 Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps,
1302 const TargetData *TD, const DominatorTree *) {
1303 // The type of the GEP pointer operand.
1304 const PointerType *PtrTy = cast<PointerType>(Ops[0]->getType());
1306 // getelementptr P -> P.
1310 if (isa<UndefValue>(Ops[0])) {
1311 // Compute the (pointer) type returned by the GEP instruction.
1312 const Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, &Ops[1],
1314 const Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace());
1315 return UndefValue::get(GEPTy);
1319 // getelementptr P, 0 -> P.
1320 if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1]))
1323 // getelementptr P, N -> P if P points to a type of zero size.
1325 const Type *Ty = PtrTy->getElementType();
1326 if (Ty->isSized() && TD->getTypeAllocSize(Ty) == 0)
1331 // Check to see if this is constant foldable.
1332 for (unsigned i = 0; i != NumOps; ++i)
1333 if (!isa<Constant>(Ops[i]))
1336 return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]),
1337 (Constant *const*)Ops+1, NumOps-1);
1340 /// SimplifyPHINode - See if we can fold the given phi. If not, returns null.
1341 static Value *SimplifyPHINode(PHINode *PN, const DominatorTree *DT) {
1342 // If all of the PHI's incoming values are the same then replace the PHI node
1343 // with the common value.
1344 Value *CommonValue = 0;
1345 bool HasUndefInput = false;
1346 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1347 Value *Incoming = PN->getIncomingValue(i);
1348 // If the incoming value is the phi node itself, it can safely be skipped.
1349 if (Incoming == PN) continue;
1350 if (isa<UndefValue>(Incoming)) {
1351 // Remember that we saw an undef value, but otherwise ignore them.
1352 HasUndefInput = true;
1355 if (CommonValue && Incoming != CommonValue)
1356 return 0; // Not the same, bail out.
1357 CommonValue = Incoming;
1360 // If CommonValue is null then all of the incoming values were either undef or
1361 // equal to the phi node itself.
1363 return UndefValue::get(PN->getType());
1365 // If we have a PHI node like phi(X, undef, X), where X is defined by some
1366 // instruction, we cannot return X as the result of the PHI node unless it
1367 // dominates the PHI block.
1369 return ValueDominatesPHI(CommonValue, PN, DT) ? CommonValue : 0;
1375 //=== Helper functions for higher up the class hierarchy.
1377 /// SimplifyBinOp - Given operands for a BinaryOperator, see if we can
1378 /// fold the result. If not, this returns null.
1379 static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
1380 const TargetData *TD, const DominatorTree *DT,
1381 unsigned MaxRecurse) {
1383 case Instruction::Add: return SimplifyAddInst(LHS, RHS, /* isNSW */ false,
1384 /* isNUW */ false, TD, DT,
1386 case Instruction::Sub: return SimplifySubInst(LHS, RHS, /* isNSW */ false,
1387 /* isNUW */ false, TD, DT,
1389 case Instruction::Mul: return SimplifyMulInst(LHS, RHS, TD, DT, MaxRecurse);
1390 case Instruction::Shl: return SimplifyShlInst(LHS, RHS, TD, DT, MaxRecurse);
1391 case Instruction::LShr: return SimplifyLShrInst(LHS, RHS, TD, DT, MaxRecurse);
1392 case Instruction::AShr: return SimplifyAShrInst(LHS, RHS, TD, DT, MaxRecurse);
1393 case Instruction::And: return SimplifyAndInst(LHS, RHS, TD, DT, MaxRecurse);
1394 case Instruction::Or: return SimplifyOrInst(LHS, RHS, TD, DT, MaxRecurse);
1395 case Instruction::Xor: return SimplifyXorInst(LHS, RHS, TD, DT, MaxRecurse);
1397 if (Constant *CLHS = dyn_cast<Constant>(LHS))
1398 if (Constant *CRHS = dyn_cast<Constant>(RHS)) {
1399 Constant *COps[] = {CLHS, CRHS};
1400 return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, 2, TD);
1403 // If the operation is associative, try some generic simplifications.
1404 if (Instruction::isAssociative(Opcode))
1405 if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, TD, DT,
1409 // If the operation is with the result of a select instruction, check whether
1410 // operating on either branch of the select always yields the same value.
1411 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
1412 if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, TD, DT,
1416 // If the operation is with the result of a phi instruction, check whether
1417 // operating on all incoming values of the phi always yields the same value.
1418 if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
1419 if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, TD, DT, MaxRecurse))
1426 Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
1427 const TargetData *TD, const DominatorTree *DT) {
1428 return ::SimplifyBinOp(Opcode, LHS, RHS, TD, DT, RecursionLimit);
1431 /// SimplifyCmpInst - Given operands for a CmpInst, see if we can
1432 /// fold the result.
1433 static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1434 const TargetData *TD, const DominatorTree *DT,
1435 unsigned MaxRecurse) {
1436 if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate))
1437 return SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse);
1438 return SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse);
1441 Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1442 const TargetData *TD, const DominatorTree *DT) {
1443 return ::SimplifyCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
1446 /// SimplifyInstruction - See if we can compute a simplified version of this
1447 /// instruction. If not, this returns null.
1448 Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD,
1449 const DominatorTree *DT) {
1452 switch (I->getOpcode()) {
1454 Result = ConstantFoldInstruction(I, TD);
1456 case Instruction::Add:
1457 Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1),
1458 cast<BinaryOperator>(I)->hasNoSignedWrap(),
1459 cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
1462 case Instruction::Sub:
1463 Result = SimplifySubInst(I->getOperand(0), I->getOperand(1),
1464 cast<BinaryOperator>(I)->hasNoSignedWrap(),
1465 cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
1468 case Instruction::Mul:
1469 Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, DT);
1471 case Instruction::Shl:
1472 Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1), TD, DT);
1474 case Instruction::LShr:
1475 Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1), TD, DT);
1477 case Instruction::AShr:
1478 Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1), TD, DT);
1480 case Instruction::And:
1481 Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT);
1483 case Instruction::Or:
1484 Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, DT);
1486 case Instruction::Xor:
1487 Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, DT);
1489 case Instruction::ICmp:
1490 Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
1491 I->getOperand(0), I->getOperand(1), TD, DT);
1493 case Instruction::FCmp:
1494 Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
1495 I->getOperand(0), I->getOperand(1), TD, DT);
1497 case Instruction::Select:
1498 Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1),
1499 I->getOperand(2), TD, DT);
1501 case Instruction::GetElementPtr: {
1502 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
1503 Result = SimplifyGEPInst(&Ops[0], Ops.size(), TD, DT);
1506 case Instruction::PHI:
1507 Result = SimplifyPHINode(cast<PHINode>(I), DT);
1511 /// If called on unreachable code, the above logic may report that the
1512 /// instruction simplified to itself. Make life easier for users by
1513 /// detecting that case here, returning a safe value instead.
1514 return Result == I ? UndefValue::get(I->getType()) : Result;
1517 /// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
1518 /// delete the From instruction. In addition to a basic RAUW, this does a
1519 /// recursive simplification of the newly formed instructions. This catches
1520 /// things where one simplification exposes other opportunities. This only
1521 /// simplifies and deletes scalar operations, it does not change the CFG.
1523 void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
1524 const TargetData *TD,
1525 const DominatorTree *DT) {
1526 assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
1528 // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that
1529 // we can know if it gets deleted out from under us or replaced in a
1530 // recursive simplification.
1531 WeakVH FromHandle(From);
1532 WeakVH ToHandle(To);
1534 while (!From->use_empty()) {
1535 // Update the instruction to use the new value.
1536 Use &TheUse = From->use_begin().getUse();
1537 Instruction *User = cast<Instruction>(TheUse.getUser());
1540 // Check to see if the instruction can be folded due to the operand
1541 // replacement. For example changing (or X, Y) into (or X, -1) can replace
1542 // the 'or' with -1.
1543 Value *SimplifiedVal;
1545 // Sanity check to make sure 'User' doesn't dangle across
1546 // SimplifyInstruction.
1547 AssertingVH<> UserHandle(User);
1549 SimplifiedVal = SimplifyInstruction(User, TD, DT);
1550 if (SimplifiedVal == 0) continue;
1553 // Recursively simplify this user to the new value.
1554 ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD, DT);
1555 From = dyn_cast_or_null<Instruction>((Value*)FromHandle);
1558 assert(ToHandle && "To value deleted by recursive simplification?");
1560 // If the recursive simplification ended up revisiting and deleting
1561 // 'From' then we're done.
1566 // If 'From' has value handles referring to it, do a real RAUW to update them.
1567 From->replaceAllUsesWith(To);
1569 From->eraseFromParent();