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))))
598 if (match(Op0, m_Mul(m_Specific(Op1), m_ConstantInt<2>())) ||
599 match(Op0, m_Shl(m_Specific(Op1), m_One())))
603 if (MaxRecurse && Op0->getType()->isIntegerTy(1))
604 if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1))
607 // X - (X - Y) -> Y. More generally Z - (X - Y) -> (Z - X) + Y if everything
609 Value *Y = 0, *Z = Op0;
610 if (MaxRecurse && match(Op1, m_Sub(m_Value(X), m_Value(Y)))) // Z - (X - Y)
611 // See if "V === Z - X" simplifies.
612 if (Value *V = SimplifyBinOp(Instruction::Sub, Z, X, TD, DT, MaxRecurse-1))
613 // It does! Now see if "W === V + Y" simplifies.
614 if (Value *W = SimplifyBinOp(Instruction::Add, V, Y, TD, DT,
616 // It does, we successfully reassociated!
621 // Mul distributes over Sub. Try some generic simplifications based on this.
622 if (Value *V = FactorizeBinOp(Instruction::Sub, Op0, Op1, Instruction::Mul,
626 // Threading Sub over selects and phi nodes is pointless, so don't bother.
627 // Threading over the select in "A - select(cond, B, C)" means evaluating
628 // "A-B" and "A-C" and seeing if they are equal; but they are equal if and
629 // only if B and C are equal. If B and C are equal then (since we assume
630 // that operands have already been simplified) "select(cond, B, C)" should
631 // have been simplified to the common value of B and C already. Analysing
632 // "A-B" and "A-C" thus gains nothing, but costs compile time. Similarly
633 // for threading over phi nodes.
638 Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
639 const TargetData *TD, const DominatorTree *DT) {
640 return ::SimplifySubInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit);
643 /// SimplifyMulInst - Given operands for a Mul, see if we can
644 /// fold the result. If not, this returns null.
645 static Value *SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
646 const DominatorTree *DT, unsigned MaxRecurse) {
647 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
648 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
649 Constant *Ops[] = { CLHS, CRHS };
650 return ConstantFoldInstOperands(Instruction::Mul, CLHS->getType(),
654 // Canonicalize the constant to the RHS.
659 if (isa<UndefValue>(Op1))
660 return Constant::getNullValue(Op0->getType());
663 if (match(Op1, m_Zero()))
667 if (match(Op1, m_One()))
671 if (MaxRecurse && Op0->getType()->isIntegerTy(1))
672 if (Value *V = SimplifyAndInst(Op0, Op1, TD, DT, MaxRecurse-1))
675 // Try some generic simplifications for associative operations.
676 if (Value *V = SimplifyAssociativeBinOp(Instruction::Mul, Op0, Op1, TD, DT,
680 // Mul distributes over Add. Try some generic simplifications based on this.
681 if (Value *V = ExpandBinOp(Instruction::Mul, Op0, Op1, Instruction::Add,
685 // If the operation is with the result of a select instruction, check whether
686 // operating on either branch of the select always yields the same value.
687 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
688 if (Value *V = ThreadBinOpOverSelect(Instruction::Mul, Op0, Op1, TD, DT,
692 // If the operation is with the result of a phi instruction, check whether
693 // operating on all incoming values of the phi always yields the same value.
694 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
695 if (Value *V = ThreadBinOpOverPHI(Instruction::Mul, Op0, Op1, TD, DT,
702 Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
703 const DominatorTree *DT) {
704 return ::SimplifyMulInst(Op0, Op1, TD, DT, RecursionLimit);
707 /// SimplifyShift - Given operands for an Shl, LShr or AShr, see if we can
708 /// fold the result. If not, this returns null.
709 static Value *SimplifyShift(unsigned Opcode, Value *Op0, Value *Op1,
710 const TargetData *TD, const DominatorTree *DT,
711 unsigned MaxRecurse) {
712 if (Constant *C0 = dyn_cast<Constant>(Op0)) {
713 if (Constant *C1 = dyn_cast<Constant>(Op1)) {
714 Constant *Ops[] = { C0, C1 };
715 return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, 2, TD);
720 if (match(Op0, m_Zero()))
724 if (match(Op1, m_Zero()))
727 // X shift by undef -> undef because it may shift by the bitwidth.
728 if (isa<UndefValue>(Op1))
731 // Shifting by the bitwidth or more is undefined.
732 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1))
733 if (CI->getValue().getLimitedValue() >=
734 Op0->getType()->getScalarSizeInBits())
735 return UndefValue::get(Op0->getType());
737 // If the operation is with the result of a select instruction, check whether
738 // operating on either branch of the select always yields the same value.
739 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
740 if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, TD, DT, MaxRecurse))
743 // If the operation is with the result of a phi instruction, check whether
744 // operating on all incoming values of the phi always yields the same value.
745 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
746 if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, TD, DT, MaxRecurse))
752 /// SimplifyShlInst - Given operands for an Shl, see if we can
753 /// fold the result. If not, this returns null.
754 static Value *SimplifyShlInst(Value *Op0, Value *Op1, const TargetData *TD,
755 const DominatorTree *DT, unsigned MaxRecurse) {
756 if (Value *V = SimplifyShift(Instruction::Shl, Op0, Op1, TD, DT, MaxRecurse))
760 if (isa<UndefValue>(Op0))
761 return Constant::getNullValue(Op0->getType());
766 Value *llvm::SimplifyShlInst(Value *Op0, Value *Op1, const TargetData *TD,
767 const DominatorTree *DT) {
768 return ::SimplifyShlInst(Op0, Op1, TD, DT, RecursionLimit);
771 /// SimplifyLShrInst - Given operands for an LShr, see if we can
772 /// fold the result. If not, this returns null.
773 static Value *SimplifyLShrInst(Value *Op0, Value *Op1, const TargetData *TD,
774 const DominatorTree *DT, unsigned MaxRecurse) {
775 if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, TD, DT, MaxRecurse))
779 if (isa<UndefValue>(Op0))
780 return Constant::getNullValue(Op0->getType());
785 Value *llvm::SimplifyLShrInst(Value *Op0, Value *Op1, const TargetData *TD,
786 const DominatorTree *DT) {
787 return ::SimplifyLShrInst(Op0, Op1, TD, DT, RecursionLimit);
790 /// SimplifyAShrInst - Given operands for an AShr, see if we can
791 /// fold the result. If not, this returns null.
792 static Value *SimplifyAShrInst(Value *Op0, Value *Op1, const TargetData *TD,
793 const DominatorTree *DT, unsigned MaxRecurse) {
794 if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, TD, DT, MaxRecurse))
797 // all ones >>a X -> all ones
798 if (match(Op0, m_AllOnes()))
801 // undef >>a X -> all ones
802 if (isa<UndefValue>(Op0))
803 return Constant::getAllOnesValue(Op0->getType());
808 Value *llvm::SimplifyAShrInst(Value *Op0, Value *Op1, const TargetData *TD,
809 const DominatorTree *DT) {
810 return ::SimplifyAShrInst(Op0, Op1, TD, DT, RecursionLimit);
813 /// SimplifyAndInst - Given operands for an And, see if we can
814 /// fold the result. If not, this returns null.
815 static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
816 const DominatorTree *DT, unsigned MaxRecurse) {
817 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
818 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
819 Constant *Ops[] = { CLHS, CRHS };
820 return ConstantFoldInstOperands(Instruction::And, CLHS->getType(),
824 // Canonicalize the constant to the RHS.
829 if (isa<UndefValue>(Op1))
830 return Constant::getNullValue(Op0->getType());
837 if (match(Op1, m_Zero()))
841 if (match(Op1, m_AllOnes()))
844 // A & ~A = ~A & A = 0
845 Value *A = 0, *B = 0;
846 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
847 (match(Op1, m_Not(m_Value(A))) && A == Op0))
848 return Constant::getNullValue(Op0->getType());
851 if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
852 (A == Op1 || B == Op1))
856 if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
857 (A == Op0 || B == Op0))
860 // Try some generic simplifications for associative operations.
861 if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, TD, DT,
865 // And distributes over Or. Try some generic simplifications based on this.
866 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Or,
870 // And distributes over Xor. Try some generic simplifications based on this.
871 if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Xor,
875 // Or distributes over And. Try some generic simplifications based on this.
876 if (Value *V = FactorizeBinOp(Instruction::And, Op0, Op1, Instruction::Or,
880 // If the operation is with the result of a select instruction, check whether
881 // operating on either branch of the select always yields the same value.
882 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
883 if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, TD, DT,
887 // If the operation is with the result of a phi instruction, check whether
888 // operating on all incoming values of the phi always yields the same value.
889 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
890 if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, TD, DT,
897 Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
898 const DominatorTree *DT) {
899 return ::SimplifyAndInst(Op0, Op1, TD, DT, RecursionLimit);
902 /// SimplifyOrInst - Given operands for an Or, see if we can
903 /// fold the result. If not, this returns null.
904 static Value *SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
905 const DominatorTree *DT, unsigned MaxRecurse) {
906 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
907 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
908 Constant *Ops[] = { CLHS, CRHS };
909 return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(),
913 // Canonicalize the constant to the RHS.
918 if (isa<UndefValue>(Op1))
919 return Constant::getAllOnesValue(Op0->getType());
926 if (match(Op1, m_Zero()))
930 if (match(Op1, m_AllOnes()))
933 // A | ~A = ~A | A = -1
934 Value *A = 0, *B = 0;
935 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
936 (match(Op1, m_Not(m_Value(A))) && A == Op0))
937 return Constant::getAllOnesValue(Op0->getType());
940 if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
941 (A == Op1 || B == Op1))
945 if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
946 (A == Op0 || B == Op0))
949 // Try some generic simplifications for associative operations.
950 if (Value *V = SimplifyAssociativeBinOp(Instruction::Or, Op0, Op1, TD, DT,
954 // Or distributes over And. Try some generic simplifications based on this.
955 if (Value *V = ExpandBinOp(Instruction::Or, Op0, Op1, Instruction::And,
959 // And distributes over Or. Try some generic simplifications based on this.
960 if (Value *V = FactorizeBinOp(Instruction::Or, Op0, Op1, Instruction::And,
964 // If the operation is with the result of a select instruction, check whether
965 // operating on either branch of the select always yields the same value.
966 if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
967 if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, TD, DT,
971 // If the operation is with the result of a phi instruction, check whether
972 // operating on all incoming values of the phi always yields the same value.
973 if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
974 if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, TD, DT,
981 Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
982 const DominatorTree *DT) {
983 return ::SimplifyOrInst(Op0, Op1, TD, DT, RecursionLimit);
986 /// SimplifyXorInst - Given operands for a Xor, see if we can
987 /// fold the result. If not, this returns null.
988 static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
989 const DominatorTree *DT, unsigned MaxRecurse) {
990 if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
991 if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
992 Constant *Ops[] = { CLHS, CRHS };
993 return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(),
997 // Canonicalize the constant to the RHS.
1001 // A ^ undef -> undef
1002 if (isa<UndefValue>(Op1))
1006 if (match(Op1, m_Zero()))
1011 return Constant::getNullValue(Op0->getType());
1013 // A ^ ~A = ~A ^ A = -1
1015 if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
1016 (match(Op1, m_Not(m_Value(A))) && A == Op0))
1017 return Constant::getAllOnesValue(Op0->getType());
1019 // Try some generic simplifications for associative operations.
1020 if (Value *V = SimplifyAssociativeBinOp(Instruction::Xor, Op0, Op1, TD, DT,
1024 // And distributes over Xor. Try some generic simplifications based on this.
1025 if (Value *V = FactorizeBinOp(Instruction::Xor, Op0, Op1, Instruction::And,
1026 TD, DT, MaxRecurse))
1029 // Threading Xor over selects and phi nodes is pointless, so don't bother.
1030 // Threading over the select in "A ^ select(cond, B, C)" means evaluating
1031 // "A^B" and "A^C" and seeing if they are equal; but they are equal if and
1032 // only if B and C are equal. If B and C are equal then (since we assume
1033 // that operands have already been simplified) "select(cond, B, C)" should
1034 // have been simplified to the common value of B and C already. Analysing
1035 // "A^B" and "A^C" thus gains nothing, but costs compile time. Similarly
1036 // for threading over phi nodes.
1041 Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
1042 const DominatorTree *DT) {
1043 return ::SimplifyXorInst(Op0, Op1, TD, DT, RecursionLimit);
1046 static const Type *GetCompareTy(Value *Op) {
1047 return CmpInst::makeCmpResultType(Op->getType());
1050 /// SimplifyICmpInst - Given operands for an ICmpInst, see if we can
1051 /// fold the result. If not, this returns null.
1052 static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1053 const TargetData *TD, const DominatorTree *DT,
1054 unsigned MaxRecurse) {
1055 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
1056 assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!");
1058 if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
1059 if (Constant *CRHS = dyn_cast<Constant>(RHS))
1060 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD);
1062 // If we have a constant, make sure it is on the RHS.
1063 std::swap(LHS, RHS);
1064 Pred = CmpInst::getSwappedPredicate(Pred);
1067 const Type *ITy = GetCompareTy(LHS); // The return type.
1068 const Type *OpTy = LHS->getType(); // The operand type.
1070 // icmp X, X -> true/false
1071 // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false
1072 // because X could be 0.
1073 if (LHS == RHS || isa<UndefValue>(RHS))
1074 return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred));
1076 // Special case logic when the operands have i1 type.
1077 if (OpTy->isIntegerTy(1) || (OpTy->isVectorTy() &&
1078 cast<VectorType>(OpTy)->getElementType()->isIntegerTy(1))) {
1081 case ICmpInst::ICMP_EQ:
1083 if (match(RHS, m_One()))
1086 case ICmpInst::ICMP_NE:
1088 if (match(RHS, m_Zero()))
1091 case ICmpInst::ICMP_UGT:
1093 if (match(RHS, m_Zero()))
1096 case ICmpInst::ICMP_UGE:
1098 if (match(RHS, m_One()))
1101 case ICmpInst::ICMP_SLT:
1103 if (match(RHS, m_Zero()))
1106 case ICmpInst::ICMP_SLE:
1108 if (match(RHS, m_One()))
1114 // See if we are doing a comparison with a constant.
1115 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
1118 case ICmpInst::ICMP_UGT:
1119 if (CI->isMaxValue(false)) // A >u MAX -> FALSE
1120 return ConstantInt::getFalse(CI->getContext());
1122 case ICmpInst::ICMP_UGE:
1123 if (CI->isMinValue(false)) // A >=u MIN -> TRUE
1124 return ConstantInt::getTrue(CI->getContext());
1126 case ICmpInst::ICMP_ULT:
1127 if (CI->isMinValue(false)) // A <u MIN -> FALSE
1128 return ConstantInt::getFalse(CI->getContext());
1130 case ICmpInst::ICMP_ULE:
1131 if (CI->isMaxValue(false)) // A <=u MAX -> TRUE
1132 return ConstantInt::getTrue(CI->getContext());
1134 case ICmpInst::ICMP_SGT:
1135 if (CI->isMaxValue(true)) // A >s MAX -> FALSE
1136 return ConstantInt::getFalse(CI->getContext());
1138 case ICmpInst::ICMP_SGE:
1139 if (CI->isMinValue(true)) // A >=s MIN -> TRUE
1140 return ConstantInt::getTrue(CI->getContext());
1142 case ICmpInst::ICMP_SLT:
1143 if (CI->isMinValue(true)) // A <s MIN -> FALSE
1144 return ConstantInt::getFalse(CI->getContext());
1146 case ICmpInst::ICMP_SLE:
1147 if (CI->isMaxValue(true)) // A <=s MAX -> TRUE
1148 return ConstantInt::getTrue(CI->getContext());
1153 // icmp <alloca*>, <global/alloca*/null> - Different stack variables have
1154 // different addresses, and what's more the address of a stack variable is
1155 // never null or equal to the address of a global. Note that generalizing
1156 // to the case where LHS is a global variable address or null is pointless,
1157 // since if both LHS and RHS are constants then we already constant folded
1158 // the compare, and if only one of them is then we moved it to RHS already.
1159 if (isa<AllocaInst>(LHS) && (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) ||
1160 isa<ConstantPointerNull>(RHS)))
1161 // We already know that LHS != LHS.
1162 return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
1164 // If the comparison is with the result of a select instruction, check whether
1165 // comparing with either branch of the select always yields the same value.
1166 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
1167 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse))
1170 // If the comparison is with the result of a phi instruction, check whether
1171 // doing the compare with each incoming phi value yields a common result.
1172 if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
1173 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse))
1179 Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1180 const TargetData *TD, const DominatorTree *DT) {
1181 return ::SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
1184 /// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can
1185 /// fold the result. If not, this returns null.
1186 static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1187 const TargetData *TD, const DominatorTree *DT,
1188 unsigned MaxRecurse) {
1189 CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
1190 assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!");
1192 if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
1193 if (Constant *CRHS = dyn_cast<Constant>(RHS))
1194 return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD);
1196 // If we have a constant, make sure it is on the RHS.
1197 std::swap(LHS, RHS);
1198 Pred = CmpInst::getSwappedPredicate(Pred);
1201 // Fold trivial predicates.
1202 if (Pred == FCmpInst::FCMP_FALSE)
1203 return ConstantInt::get(GetCompareTy(LHS), 0);
1204 if (Pred == FCmpInst::FCMP_TRUE)
1205 return ConstantInt::get(GetCompareTy(LHS), 1);
1207 if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef
1208 return UndefValue::get(GetCompareTy(LHS));
1210 // fcmp x,x -> true/false. Not all compares are foldable.
1212 if (CmpInst::isTrueWhenEqual(Pred))
1213 return ConstantInt::get(GetCompareTy(LHS), 1);
1214 if (CmpInst::isFalseWhenEqual(Pred))
1215 return ConstantInt::get(GetCompareTy(LHS), 0);
1218 // Handle fcmp with constant RHS
1219 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
1220 // If the constant is a nan, see if we can fold the comparison based on it.
1221 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
1222 if (CFP->getValueAPF().isNaN()) {
1223 if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo"
1224 return ConstantInt::getFalse(CFP->getContext());
1225 assert(FCmpInst::isUnordered(Pred) &&
1226 "Comparison must be either ordered or unordered!");
1227 // True if unordered.
1228 return ConstantInt::getTrue(CFP->getContext());
1230 // Check whether the constant is an infinity.
1231 if (CFP->getValueAPF().isInfinity()) {
1232 if (CFP->getValueAPF().isNegative()) {
1234 case FCmpInst::FCMP_OLT:
1235 // No value is ordered and less than negative infinity.
1236 return ConstantInt::getFalse(CFP->getContext());
1237 case FCmpInst::FCMP_UGE:
1238 // All values are unordered with or at least negative infinity.
1239 return ConstantInt::getTrue(CFP->getContext());
1245 case FCmpInst::FCMP_OGT:
1246 // No value is ordered and greater than infinity.
1247 return ConstantInt::getFalse(CFP->getContext());
1248 case FCmpInst::FCMP_ULE:
1249 // All values are unordered with and at most infinity.
1250 return ConstantInt::getTrue(CFP->getContext());
1259 // If the comparison is with the result of a select instruction, check whether
1260 // comparing with either branch of the select always yields the same value.
1261 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
1262 if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse))
1265 // If the comparison is with the result of a phi instruction, check whether
1266 // doing the compare with each incoming phi value yields a common result.
1267 if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
1268 if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse))
1274 Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1275 const TargetData *TD, const DominatorTree *DT) {
1276 return ::SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
1279 /// SimplifySelectInst - Given operands for a SelectInst, see if we can fold
1280 /// the result. If not, this returns null.
1281 Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal,
1282 const TargetData *TD, const DominatorTree *) {
1283 // select true, X, Y -> X
1284 // select false, X, Y -> Y
1285 if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal))
1286 return CB->getZExtValue() ? TrueVal : FalseVal;
1288 // select C, X, X -> X
1289 if (TrueVal == FalseVal)
1292 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
1294 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
1296 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
1297 if (isa<Constant>(TrueVal))
1305 /// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
1306 /// fold the result. If not, this returns null.
1307 Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps,
1308 const TargetData *TD, const DominatorTree *) {
1309 // The type of the GEP pointer operand.
1310 const PointerType *PtrTy = cast<PointerType>(Ops[0]->getType());
1312 // getelementptr P -> P.
1316 if (isa<UndefValue>(Ops[0])) {
1317 // Compute the (pointer) type returned by the GEP instruction.
1318 const Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, &Ops[1],
1320 const Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace());
1321 return UndefValue::get(GEPTy);
1325 // getelementptr P, 0 -> P.
1326 if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1]))
1329 // getelementptr P, N -> P if P points to a type of zero size.
1331 const Type *Ty = PtrTy->getElementType();
1332 if (Ty->isSized() && TD->getTypeAllocSize(Ty) == 0)
1337 // Check to see if this is constant foldable.
1338 for (unsigned i = 0; i != NumOps; ++i)
1339 if (!isa<Constant>(Ops[i]))
1342 return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]),
1343 (Constant *const*)Ops+1, NumOps-1);
1346 /// SimplifyPHINode - See if we can fold the given phi. If not, returns null.
1347 static Value *SimplifyPHINode(PHINode *PN, const DominatorTree *DT) {
1348 // If all of the PHI's incoming values are the same then replace the PHI node
1349 // with the common value.
1350 Value *CommonValue = 0;
1351 bool HasUndefInput = false;
1352 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1353 Value *Incoming = PN->getIncomingValue(i);
1354 // If the incoming value is the phi node itself, it can safely be skipped.
1355 if (Incoming == PN) continue;
1356 if (isa<UndefValue>(Incoming)) {
1357 // Remember that we saw an undef value, but otherwise ignore them.
1358 HasUndefInput = true;
1361 if (CommonValue && Incoming != CommonValue)
1362 return 0; // Not the same, bail out.
1363 CommonValue = Incoming;
1366 // If CommonValue is null then all of the incoming values were either undef or
1367 // equal to the phi node itself.
1369 return UndefValue::get(PN->getType());
1371 // If we have a PHI node like phi(X, undef, X), where X is defined by some
1372 // instruction, we cannot return X as the result of the PHI node unless it
1373 // dominates the PHI block.
1375 return ValueDominatesPHI(CommonValue, PN, DT) ? CommonValue : 0;
1381 //=== Helper functions for higher up the class hierarchy.
1383 /// SimplifyBinOp - Given operands for a BinaryOperator, see if we can
1384 /// fold the result. If not, this returns null.
1385 static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
1386 const TargetData *TD, const DominatorTree *DT,
1387 unsigned MaxRecurse) {
1389 case Instruction::Add: return SimplifyAddInst(LHS, RHS, /* isNSW */ false,
1390 /* isNUW */ false, TD, DT,
1392 case Instruction::Sub: return SimplifySubInst(LHS, RHS, /* isNSW */ false,
1393 /* isNUW */ false, TD, DT,
1395 case Instruction::Mul: return SimplifyMulInst(LHS, RHS, TD, DT, MaxRecurse);
1396 case Instruction::Shl: return SimplifyShlInst(LHS, RHS, TD, DT, MaxRecurse);
1397 case Instruction::LShr: return SimplifyLShrInst(LHS, RHS, TD, DT, MaxRecurse);
1398 case Instruction::AShr: return SimplifyAShrInst(LHS, RHS, TD, DT, MaxRecurse);
1399 case Instruction::And: return SimplifyAndInst(LHS, RHS, TD, DT, MaxRecurse);
1400 case Instruction::Or: return SimplifyOrInst(LHS, RHS, TD, DT, MaxRecurse);
1401 case Instruction::Xor: return SimplifyXorInst(LHS, RHS, TD, DT, MaxRecurse);
1403 if (Constant *CLHS = dyn_cast<Constant>(LHS))
1404 if (Constant *CRHS = dyn_cast<Constant>(RHS)) {
1405 Constant *COps[] = {CLHS, CRHS};
1406 return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, 2, TD);
1409 // If the operation is associative, try some generic simplifications.
1410 if (Instruction::isAssociative(Opcode))
1411 if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, TD, DT,
1415 // If the operation is with the result of a select instruction, check whether
1416 // operating on either branch of the select always yields the same value.
1417 if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
1418 if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, TD, DT,
1422 // If the operation is with the result of a phi instruction, check whether
1423 // operating on all incoming values of the phi always yields the same value.
1424 if (isa<PHINode>(LHS) || isa<PHINode>(RHS))
1425 if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, TD, DT, MaxRecurse))
1432 Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
1433 const TargetData *TD, const DominatorTree *DT) {
1434 return ::SimplifyBinOp(Opcode, LHS, RHS, TD, DT, RecursionLimit);
1437 /// SimplifyCmpInst - Given operands for a CmpInst, see if we can
1438 /// fold the result.
1439 static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1440 const TargetData *TD, const DominatorTree *DT,
1441 unsigned MaxRecurse) {
1442 if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate))
1443 return SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse);
1444 return SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse);
1447 Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
1448 const TargetData *TD, const DominatorTree *DT) {
1449 return ::SimplifyCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
1452 /// SimplifyInstruction - See if we can compute a simplified version of this
1453 /// instruction. If not, this returns null.
1454 Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD,
1455 const DominatorTree *DT) {
1458 switch (I->getOpcode()) {
1460 Result = ConstantFoldInstruction(I, TD);
1462 case Instruction::Add:
1463 Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1),
1464 cast<BinaryOperator>(I)->hasNoSignedWrap(),
1465 cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
1468 case Instruction::Sub:
1469 Result = SimplifySubInst(I->getOperand(0), I->getOperand(1),
1470 cast<BinaryOperator>(I)->hasNoSignedWrap(),
1471 cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
1474 case Instruction::Mul:
1475 Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, DT);
1477 case Instruction::Shl:
1478 Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1), TD, DT);
1480 case Instruction::LShr:
1481 Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1), TD, DT);
1483 case Instruction::AShr:
1484 Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1), TD, DT);
1486 case Instruction::And:
1487 Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT);
1489 case Instruction::Or:
1490 Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, DT);
1492 case Instruction::Xor:
1493 Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, DT);
1495 case Instruction::ICmp:
1496 Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
1497 I->getOperand(0), I->getOperand(1), TD, DT);
1499 case Instruction::FCmp:
1500 Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
1501 I->getOperand(0), I->getOperand(1), TD, DT);
1503 case Instruction::Select:
1504 Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1),
1505 I->getOperand(2), TD, DT);
1507 case Instruction::GetElementPtr: {
1508 SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
1509 Result = SimplifyGEPInst(&Ops[0], Ops.size(), TD, DT);
1512 case Instruction::PHI:
1513 Result = SimplifyPHINode(cast<PHINode>(I), DT);
1517 /// If called on unreachable code, the above logic may report that the
1518 /// instruction simplified to itself. Make life easier for users by
1519 /// detecting that case here, returning a safe value instead.
1520 return Result == I ? UndefValue::get(I->getType()) : Result;
1523 /// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
1524 /// delete the From instruction. In addition to a basic RAUW, this does a
1525 /// recursive simplification of the newly formed instructions. This catches
1526 /// things where one simplification exposes other opportunities. This only
1527 /// simplifies and deletes scalar operations, it does not change the CFG.
1529 void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
1530 const TargetData *TD,
1531 const DominatorTree *DT) {
1532 assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
1534 // FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that
1535 // we can know if it gets deleted out from under us or replaced in a
1536 // recursive simplification.
1537 WeakVH FromHandle(From);
1538 WeakVH ToHandle(To);
1540 while (!From->use_empty()) {
1541 // Update the instruction to use the new value.
1542 Use &TheUse = From->use_begin().getUse();
1543 Instruction *User = cast<Instruction>(TheUse.getUser());
1546 // Check to see if the instruction can be folded due to the operand
1547 // replacement. For example changing (or X, Y) into (or X, -1) can replace
1548 // the 'or' with -1.
1549 Value *SimplifiedVal;
1551 // Sanity check to make sure 'User' doesn't dangle across
1552 // SimplifyInstruction.
1553 AssertingVH<> UserHandle(User);
1555 SimplifiedVal = SimplifyInstruction(User, TD, DT);
1556 if (SimplifiedVal == 0) continue;
1559 // Recursively simplify this user to the new value.
1560 ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD, DT);
1561 From = dyn_cast_or_null<Instruction>((Value*)FromHandle);
1564 assert(ToHandle && "To value deleted by recursive simplification?");
1566 // If the recursive simplification ended up revisiting and deleting
1567 // 'From' then we're done.
1572 // If 'From' has value handles referring to it, do a real RAUW to update them.
1573 From->replaceAllUsesWith(To);
1575 From->eraseFromParent();