1 //===- InstructionCombining.cpp - Combine multiple instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // InstructionCombining - Combine instructions to form fewer, simple
11 // instructions. This pass does not modify the CFG This pass is where algebraic
12 // simplification happens.
14 // This pass combines things like:
20 // This is a simple worklist driven algorithm.
22 // This pass guarantees that the following canonicalizations are performed on
24 // 1. If a binary operator has a constant operand, it is moved to the RHS
25 // 2. Bitwise operators with constant operands are always grouped so that
26 // shifts are performed first, then or's, then and's, then xor's.
27 // 3. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible
28 // 4. All SetCC instructions on boolean values are replaced with logical ops
29 // 5. add X, X is represented as (X*2) => (X << 1)
30 // 6. Multiplies with a power-of-two constant argument are transformed into
34 //===----------------------------------------------------------------------===//
36 #define DEBUG_TYPE "instcombine"
37 #include "llvm/Transforms/Scalar.h"
38 #include "llvm/IntrinsicInst.h"
39 #include "llvm/Pass.h"
40 #include "llvm/DerivedTypes.h"
41 #include "llvm/GlobalVariable.h"
42 #include "llvm/Target/TargetData.h"
43 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
44 #include "llvm/Transforms/Utils/Local.h"
45 #include "llvm/Support/CallSite.h"
46 #include "llvm/Support/Debug.h"
47 #include "llvm/Support/GetElementPtrTypeIterator.h"
48 #include "llvm/Support/InstIterator.h"
49 #include "llvm/Support/InstVisitor.h"
50 #include "llvm/Support/PatternMatch.h"
51 #include "llvm/ADT/Statistic.h"
52 #include "llvm/ADT/STLExtras.h"
55 using namespace llvm::PatternMatch;
58 Statistic<> NumCombined ("instcombine", "Number of insts combined");
59 Statistic<> NumConstProp("instcombine", "Number of constant folds");
60 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
61 Statistic<> NumSunkInst ("instcombine", "Number of instructions sunk");
63 class InstCombiner : public FunctionPass,
64 public InstVisitor<InstCombiner, Instruction*> {
65 // Worklist of all of the instructions that need to be simplified.
66 std::vector<Instruction*> WorkList;
69 /// AddUsersToWorkList - When an instruction is simplified, add all users of
70 /// the instruction to the work lists because they might get more simplified
73 void AddUsersToWorkList(Instruction &I) {
74 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
76 WorkList.push_back(cast<Instruction>(*UI));
79 /// AddUsesToWorkList - When an instruction is simplified, add operands to
80 /// the work lists because they might get more simplified now.
82 void AddUsesToWorkList(Instruction &I) {
83 for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
84 if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i)))
85 WorkList.push_back(Op);
88 // removeFromWorkList - remove all instances of I from the worklist.
89 void removeFromWorkList(Instruction *I);
91 virtual bool runOnFunction(Function &F);
93 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
94 AU.addRequired<TargetData>();
98 TargetData &getTargetData() const { return *TD; }
100 // Visitation implementation - Implement instruction combining for different
101 // instruction types. The semantics are as follows:
103 // null - No change was made
104 // I - Change was made, I is still valid, I may be dead though
105 // otherwise - Change was made, replace I with returned instruction
107 Instruction *visitAdd(BinaryOperator &I);
108 Instruction *visitSub(BinaryOperator &I);
109 Instruction *visitMul(BinaryOperator &I);
110 Instruction *visitDiv(BinaryOperator &I);
111 Instruction *visitRem(BinaryOperator &I);
112 Instruction *visitAnd(BinaryOperator &I);
113 Instruction *visitOr (BinaryOperator &I);
114 Instruction *visitXor(BinaryOperator &I);
115 Instruction *visitSetCondInst(BinaryOperator &I);
116 Instruction *visitSetCondInstWithCastAndConstant(BinaryOperator&I,
119 Instruction *visitShiftInst(ShiftInst &I);
120 Instruction *visitCastInst(CastInst &CI);
121 Instruction *visitSelectInst(SelectInst &CI);
122 Instruction *visitCallInst(CallInst &CI);
123 Instruction *visitInvokeInst(InvokeInst &II);
124 Instruction *visitPHINode(PHINode &PN);
125 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
126 Instruction *visitAllocationInst(AllocationInst &AI);
127 Instruction *visitFreeInst(FreeInst &FI);
128 Instruction *visitLoadInst(LoadInst &LI);
129 Instruction *visitBranchInst(BranchInst &BI);
130 Instruction *visitSwitchInst(SwitchInst &SI);
132 // visitInstruction - Specify what to return for unhandled instructions...
133 Instruction *visitInstruction(Instruction &I) { return 0; }
136 Instruction *visitCallSite(CallSite CS);
137 bool transformConstExprCastCall(CallSite CS);
140 // InsertNewInstBefore - insert an instruction New before instruction Old
141 // in the program. Add the new instruction to the worklist.
143 Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
144 assert(New && New->getParent() == 0 &&
145 "New instruction already inserted into a basic block!");
146 BasicBlock *BB = Old.getParent();
147 BB->getInstList().insert(&Old, New); // Insert inst
148 WorkList.push_back(New); // Add to worklist
152 /// InsertCastBefore - Insert a cast of V to TY before the instruction POS.
153 /// This also adds the cast to the worklist. Finally, this returns the
155 Value *InsertCastBefore(Value *V, const Type *Ty, Instruction &Pos) {
156 if (V->getType() == Ty) return V;
158 Instruction *C = new CastInst(V, Ty, V->getName(), &Pos);
159 WorkList.push_back(C);
163 // ReplaceInstUsesWith - This method is to be used when an instruction is
164 // found to be dead, replacable with another preexisting expression. Here
165 // we add all uses of I to the worklist, replace all uses of I with the new
166 // value, then return I, so that the inst combiner will know that I was
169 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
170 AddUsersToWorkList(I); // Add all modified instrs to worklist
172 I.replaceAllUsesWith(V);
175 // If we are replacing the instruction with itself, this must be in a
176 // segment of unreachable code, so just clobber the instruction.
177 I.replaceAllUsesWith(UndefValue::get(I.getType()));
182 // EraseInstFromFunction - When dealing with an instruction that has side
183 // effects or produces a void value, we can't rely on DCE to delete the
184 // instruction. Instead, visit methods should return the value returned by
186 Instruction *EraseInstFromFunction(Instruction &I) {
187 assert(I.use_empty() && "Cannot erase instruction that is used!");
188 AddUsesToWorkList(I);
189 removeFromWorkList(&I);
191 return 0; // Don't do anything with FI
196 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
197 /// InsertBefore instruction. This is specialized a bit to avoid inserting
198 /// casts that are known to not do anything...
200 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
201 Instruction *InsertBefore);
203 // SimplifyCommutative - This performs a few simplifications for commutative
205 bool SimplifyCommutative(BinaryOperator &I);
208 // FoldOpIntoPhi - Given a binary operator or cast instruction which has a
209 // PHI node as operand #0, see if we can fold the instruction into the PHI
210 // (which is only possible if all operands to the PHI are constants).
211 Instruction *FoldOpIntoPhi(Instruction &I);
213 // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
214 // operator and they all are only used by the PHI, PHI together their
215 // inputs, and do the operation once, to the result of the PHI.
216 Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
218 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
219 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
221 Instruction *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
222 bool Inside, Instruction &IB);
225 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
228 // getComplexity: Assign a complexity or rank value to LLVM Values...
229 // 0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
230 static unsigned getComplexity(Value *V) {
231 if (isa<Instruction>(V)) {
232 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
236 if (isa<Argument>(V)) return 3;
237 return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
240 // isOnlyUse - Return true if this instruction will be deleted if we stop using
242 static bool isOnlyUse(Value *V) {
243 return V->hasOneUse() || isa<Constant>(V);
246 // getPromotedType - Return the specified type promoted as it would be to pass
247 // though a va_arg area...
248 static const Type *getPromotedType(const Type *Ty) {
249 switch (Ty->getTypeID()) {
250 case Type::SByteTyID:
251 case Type::ShortTyID: return Type::IntTy;
252 case Type::UByteTyID:
253 case Type::UShortTyID: return Type::UIntTy;
254 case Type::FloatTyID: return Type::DoubleTy;
259 // SimplifyCommutative - This performs a few simplifications for commutative
262 // 1. Order operands such that they are listed from right (least complex) to
263 // left (most complex). This puts constants before unary operators before
266 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
267 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
269 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
270 bool Changed = false;
271 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
272 Changed = !I.swapOperands();
274 if (!I.isAssociative()) return Changed;
275 Instruction::BinaryOps Opcode = I.getOpcode();
276 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
277 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
278 if (isa<Constant>(I.getOperand(1))) {
279 Constant *Folded = ConstantExpr::get(I.getOpcode(),
280 cast<Constant>(I.getOperand(1)),
281 cast<Constant>(Op->getOperand(1)));
282 I.setOperand(0, Op->getOperand(0));
283 I.setOperand(1, Folded);
285 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
286 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
287 isOnlyUse(Op) && isOnlyUse(Op1)) {
288 Constant *C1 = cast<Constant>(Op->getOperand(1));
289 Constant *C2 = cast<Constant>(Op1->getOperand(1));
291 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
292 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
293 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
296 WorkList.push_back(New);
297 I.setOperand(0, New);
298 I.setOperand(1, Folded);
305 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
306 // if the LHS is a constant zero (which is the 'negate' form).
308 static inline Value *dyn_castNegVal(Value *V) {
309 if (BinaryOperator::isNeg(V))
310 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
312 // Constants can be considered to be negated values if they can be folded...
313 if (Constant *C = dyn_cast<Constant>(V))
314 if (!isa<UndefValue>(C))
315 return ConstantExpr::getNeg(C);
319 static inline Value *dyn_castNotVal(Value *V) {
320 if (BinaryOperator::isNot(V))
321 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
323 // Constants can be considered to be not'ed values...
324 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
325 return ConstantExpr::getNot(C);
329 // dyn_castFoldableMul - If this value is a multiply that can be folded into
330 // other computations (because it has a constant operand), return the
331 // non-constant operand of the multiply, and set CST to point to the multiplier.
332 // Otherwise, return null.
334 static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) {
335 if (V->hasOneUse() && V->getType()->isInteger())
336 if (Instruction *I = dyn_cast<Instruction>(V)) {
337 if (I->getOpcode() == Instruction::Mul)
338 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1))))
339 return I->getOperand(0);
340 if (I->getOpcode() == Instruction::Shl)
341 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) {
342 // The multiplier is really 1 << CST.
343 Constant *One = ConstantInt::get(V->getType(), 1);
344 CST = cast<ConstantInt>(ConstantExpr::getShl(One, CST));
345 return I->getOperand(0);
351 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
353 static unsigned Log2(uint64_t Val) {
354 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
357 if (Val & 1) return 0; // Multiple bits set?
364 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
365 static ConstantInt *AddOne(ConstantInt *C) {
366 return cast<ConstantInt>(ConstantExpr::getAdd(C,
367 ConstantInt::get(C->getType(), 1)));
369 static ConstantInt *SubOne(ConstantInt *C) {
370 return cast<ConstantInt>(ConstantExpr::getSub(C,
371 ConstantInt::get(C->getType(), 1)));
374 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
375 // true when both operands are equal...
377 static bool isTrueWhenEqual(Instruction &I) {
378 return I.getOpcode() == Instruction::SetEQ ||
379 I.getOpcode() == Instruction::SetGE ||
380 I.getOpcode() == Instruction::SetLE;
383 /// AssociativeOpt - Perform an optimization on an associative operator. This
384 /// function is designed to check a chain of associative operators for a
385 /// potential to apply a certain optimization. Since the optimization may be
386 /// applicable if the expression was reassociated, this checks the chain, then
387 /// reassociates the expression as necessary to expose the optimization
388 /// opportunity. This makes use of a special Functor, which must define
389 /// 'shouldApply' and 'apply' methods.
391 template<typename Functor>
392 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
393 unsigned Opcode = Root.getOpcode();
394 Value *LHS = Root.getOperand(0);
396 // Quick check, see if the immediate LHS matches...
397 if (F.shouldApply(LHS))
398 return F.apply(Root);
400 // Otherwise, if the LHS is not of the same opcode as the root, return.
401 Instruction *LHSI = dyn_cast<Instruction>(LHS);
402 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
403 // Should we apply this transform to the RHS?
404 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
406 // If not to the RHS, check to see if we should apply to the LHS...
407 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
408 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
412 // If the functor wants to apply the optimization to the RHS of LHSI,
413 // reassociate the expression from ((? op A) op B) to (? op (A op B))
415 BasicBlock *BB = Root.getParent();
417 // Now all of the instructions are in the current basic block, go ahead
418 // and perform the reassociation.
419 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
421 // First move the selected RHS to the LHS of the root...
422 Root.setOperand(0, LHSI->getOperand(1));
424 // Make what used to be the LHS of the root be the user of the root...
425 Value *ExtraOperand = TmpLHSI->getOperand(1);
426 if (&Root == TmpLHSI) {
427 Root.replaceAllUsesWith(Constant::getNullValue(TmpLHSI->getType()));
430 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
431 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
432 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
433 BasicBlock::iterator ARI = &Root; ++ARI;
434 BB->getInstList().insert(ARI, TmpLHSI); // Move TmpLHSI to after Root
437 // Now propagate the ExtraOperand down the chain of instructions until we
439 while (TmpLHSI != LHSI) {
440 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
441 // Move the instruction to immediately before the chain we are
442 // constructing to avoid breaking dominance properties.
443 NextLHSI->getParent()->getInstList().remove(NextLHSI);
444 BB->getInstList().insert(ARI, NextLHSI);
447 Value *NextOp = NextLHSI->getOperand(1);
448 NextLHSI->setOperand(1, ExtraOperand);
450 ExtraOperand = NextOp;
453 // Now that the instructions are reassociated, have the functor perform
454 // the transformation...
455 return F.apply(Root);
458 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
464 // AddRHS - Implements: X + X --> X << 1
467 AddRHS(Value *rhs) : RHS(rhs) {}
468 bool shouldApply(Value *LHS) const { return LHS == RHS; }
469 Instruction *apply(BinaryOperator &Add) const {
470 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
471 ConstantInt::get(Type::UByteTy, 1));
475 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
477 struct AddMaskingAnd {
479 AddMaskingAnd(Constant *c) : C2(c) {}
480 bool shouldApply(Value *LHS) const {
482 return match(LHS, m_And(m_Value(), m_ConstantInt(C1))) &&
483 ConstantExpr::getAnd(C1, C2)->isNullValue();
485 Instruction *apply(BinaryOperator &Add) const {
486 return BinaryOperator::createOr(Add.getOperand(0), Add.getOperand(1));
490 static Value *FoldOperationIntoSelectOperand(Instruction &BI, Value *SO,
492 // Figure out if the constant is the left or the right argument.
493 bool ConstIsRHS = isa<Constant>(BI.getOperand(1));
494 Constant *ConstOperand = cast<Constant>(BI.getOperand(ConstIsRHS));
496 if (Constant *SOC = dyn_cast<Constant>(SO)) {
498 return ConstantExpr::get(BI.getOpcode(), SOC, ConstOperand);
499 return ConstantExpr::get(BI.getOpcode(), ConstOperand, SOC);
502 Value *Op0 = SO, *Op1 = ConstOperand;
506 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&BI))
507 New = BinaryOperator::create(BO->getOpcode(), Op0, Op1);
508 else if (ShiftInst *SI = dyn_cast<ShiftInst>(&BI))
509 New = new ShiftInst(SI->getOpcode(), Op0, Op1);
511 assert(0 && "Unknown binary instruction type!");
514 return IC->InsertNewInstBefore(New, BI);
518 /// FoldOpIntoPhi - Given a binary operator or cast instruction which has a PHI
519 /// node as operand #0, see if we can fold the instruction into the PHI (which
520 /// is only possible if all operands to the PHI are constants).
521 Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
522 PHINode *PN = cast<PHINode>(I.getOperand(0));
523 unsigned NumPHIValues = PN->getNumIncomingValues();
524 if (!PN->hasOneUse() || NumPHIValues == 0 ||
525 !isa<Constant>(PN->getIncomingValue(0))) return 0;
527 // Check to see if all of the operands of the PHI are constants. If not, we
528 // cannot do the transformation.
529 for (unsigned i = 1; i != NumPHIValues; ++i)
530 if (!isa<Constant>(PN->getIncomingValue(i)))
533 // Okay, we can do the transformation: create the new PHI node.
534 PHINode *NewPN = new PHINode(I.getType(), I.getName());
536 NewPN->op_reserve(PN->getNumOperands());
537 InsertNewInstBefore(NewPN, *PN);
539 // Next, add all of the operands to the PHI.
540 if (I.getNumOperands() == 2) {
541 Constant *C = cast<Constant>(I.getOperand(1));
542 for (unsigned i = 0; i != NumPHIValues; ++i) {
543 Constant *InV = cast<Constant>(PN->getIncomingValue(i));
544 NewPN->addIncoming(ConstantExpr::get(I.getOpcode(), InV, C),
545 PN->getIncomingBlock(i));
548 assert(isa<CastInst>(I) && "Unary op should be a cast!");
549 const Type *RetTy = I.getType();
550 for (unsigned i = 0; i != NumPHIValues; ++i) {
551 Constant *InV = cast<Constant>(PN->getIncomingValue(i));
552 NewPN->addIncoming(ConstantExpr::getCast(InV, RetTy),
553 PN->getIncomingBlock(i));
556 return ReplaceInstUsesWith(I, NewPN);
559 // FoldBinOpIntoSelect - Given an instruction with a select as one operand and a
560 // constant as the other operand, try to fold the binary operator into the
562 static Instruction *FoldBinOpIntoSelect(Instruction &BI, SelectInst *SI,
564 // Don't modify shared select instructions
565 if (!SI->hasOneUse()) return 0;
566 Value *TV = SI->getOperand(1);
567 Value *FV = SI->getOperand(2);
569 if (isa<Constant>(TV) || isa<Constant>(FV)) {
570 Value *SelectTrueVal = FoldOperationIntoSelectOperand(BI, TV, IC);
571 Value *SelectFalseVal = FoldOperationIntoSelectOperand(BI, FV, IC);
573 return new SelectInst(SI->getCondition(), SelectTrueVal,
579 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
580 bool Changed = SimplifyCommutative(I);
581 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
583 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
584 // X + undef -> undef
585 if (isa<UndefValue>(RHS))
586 return ReplaceInstUsesWith(I, RHS);
589 if (!I.getType()->isFloatingPoint() && // -0 + +0 = +0, so it's not a noop
591 return ReplaceInstUsesWith(I, LHS);
593 // X + (signbit) --> X ^ signbit
594 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
595 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
596 uint64_t Val = CI->getRawValue() & (1ULL << NumBits)-1;
597 if (Val == (1ULL << (NumBits-1)))
598 return BinaryOperator::createXor(LHS, RHS);
601 if (isa<PHINode>(LHS))
602 if (Instruction *NV = FoldOpIntoPhi(I))
607 if (I.getType()->isInteger()) {
608 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
612 if (Value *V = dyn_castNegVal(LHS))
613 return BinaryOperator::createSub(RHS, V);
616 if (!isa<Constant>(RHS))
617 if (Value *V = dyn_castNegVal(RHS))
618 return BinaryOperator::createSub(LHS, V);
621 if (Value *X = dyn_castFoldableMul(LHS, C2)) {
622 if (X == RHS) // X*C + X --> X * (C+1)
623 return BinaryOperator::createMul(RHS, AddOne(C2));
625 // X*C1 + X*C2 --> X * (C1+C2)
627 if (X == dyn_castFoldableMul(RHS, C1))
628 return BinaryOperator::createMul(X, ConstantExpr::getAdd(C1, C2));
631 // X + X*C --> X * (C+1)
632 if (dyn_castFoldableMul(RHS, C2) == LHS)
633 return BinaryOperator::createMul(LHS, AddOne(C2));
636 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
637 if (match(RHS, m_And(m_Value(), m_ConstantInt(C2))))
638 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
640 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
642 if (match(LHS, m_Not(m_Value(X)))) { // ~X + C --> (C-1) - X
643 Constant *C= ConstantExpr::getSub(CRHS, ConstantInt::get(I.getType(), 1));
644 return BinaryOperator::createSub(C, X);
647 // (X & FF00) + xx00 -> (X+xx00) & FF00
648 if (LHS->hasOneUse() && match(LHS, m_And(m_Value(X), m_ConstantInt(C2)))) {
649 Constant *Anded = ConstantExpr::getAnd(CRHS, C2);
651 // See if all bits from the first bit set in the Add RHS up are included
652 // in the mask. First, get the rightmost bit.
653 uint64_t AddRHSV = CRHS->getRawValue();
655 // Form a mask of all bits from the lowest bit added through the top.
656 uint64_t AddRHSHighBits = ~((AddRHSV & -AddRHSV)-1);
657 AddRHSHighBits &= (1ULL << C2->getType()->getPrimitiveSize()*8)-1;
659 // See if the and mask includes all of these bits.
660 uint64_t AddRHSHighBitsAnd = AddRHSHighBits & C2->getRawValue();
662 if (AddRHSHighBits == AddRHSHighBitsAnd) {
663 // Okay, the xform is safe. Insert the new add pronto.
664 Value *NewAdd = InsertNewInstBefore(BinaryOperator::createAdd(X, CRHS,
666 return BinaryOperator::createAnd(NewAdd, C2);
672 // Try to fold constant add into select arguments.
673 if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
674 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
678 return Changed ? &I : 0;
681 // isSignBit - Return true if the value represented by the constant only has the
682 // highest order bit set.
683 static bool isSignBit(ConstantInt *CI) {
684 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
685 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
688 static unsigned getTypeSizeInBits(const Type *Ty) {
689 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
692 /// RemoveNoopCast - Strip off nonconverting casts from the value.
694 static Value *RemoveNoopCast(Value *V) {
695 if (CastInst *CI = dyn_cast<CastInst>(V)) {
696 const Type *CTy = CI->getType();
697 const Type *OpTy = CI->getOperand(0)->getType();
698 if (CTy->isInteger() && OpTy->isInteger()) {
699 if (CTy->getPrimitiveSize() == OpTy->getPrimitiveSize())
700 return RemoveNoopCast(CI->getOperand(0));
701 } else if (isa<PointerType>(CTy) && isa<PointerType>(OpTy))
702 return RemoveNoopCast(CI->getOperand(0));
707 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
708 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
710 if (Op0 == Op1) // sub X, X -> 0
711 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
713 // If this is a 'B = x-(-A)', change to B = x+A...
714 if (Value *V = dyn_castNegVal(Op1))
715 return BinaryOperator::createAdd(Op0, V);
717 if (isa<UndefValue>(Op0))
718 return ReplaceInstUsesWith(I, Op0); // undef - X -> undef
719 if (isa<UndefValue>(Op1))
720 return ReplaceInstUsesWith(I, Op1); // X - undef -> undef
722 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
723 // Replace (-1 - A) with (~A)...
724 if (C->isAllOnesValue())
725 return BinaryOperator::createNot(Op1);
727 // C - ~X == X + (1+C)
729 if (match(Op1, m_Not(m_Value(X))))
730 return BinaryOperator::createAdd(X,
731 ConstantExpr::getAdd(C, ConstantInt::get(I.getType(), 1)));
732 // -((uint)X >> 31) -> ((int)X >> 31)
733 // -((int)X >> 31) -> ((uint)X >> 31)
734 if (C->isNullValue()) {
735 Value *NoopCastedRHS = RemoveNoopCast(Op1);
736 if (ShiftInst *SI = dyn_cast<ShiftInst>(NoopCastedRHS))
737 if (SI->getOpcode() == Instruction::Shr)
738 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
740 if (SI->getType()->isSigned())
741 NewTy = SI->getType()->getUnsignedVersion();
743 NewTy = SI->getType()->getSignedVersion();
744 // Check to see if we are shifting out everything but the sign bit.
745 if (CU->getValue() == SI->getType()->getPrimitiveSize()*8-1) {
746 // Ok, the transformation is safe. Insert a cast of the incoming
747 // value, then the new shift, then the new cast.
748 Instruction *FirstCast = new CastInst(SI->getOperand(0), NewTy,
749 SI->getOperand(0)->getName());
750 Value *InV = InsertNewInstBefore(FirstCast, I);
751 Instruction *NewShift = new ShiftInst(Instruction::Shr, FirstCast,
753 if (NewShift->getType() == I.getType())
756 InV = InsertNewInstBefore(NewShift, I);
757 return new CastInst(NewShift, I.getType());
763 // Try to fold constant sub into select arguments.
764 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
765 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
768 if (isa<PHINode>(Op0))
769 if (Instruction *NV = FoldOpIntoPhi(I))
773 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
774 if (Op1I->hasOneUse()) {
775 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
776 // is not used by anyone else...
778 if (Op1I->getOpcode() == Instruction::Sub &&
779 !Op1I->getType()->isFloatingPoint()) {
780 // Swap the two operands of the subexpr...
781 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
782 Op1I->setOperand(0, IIOp1);
783 Op1I->setOperand(1, IIOp0);
785 // Create the new top level add instruction...
786 return BinaryOperator::createAdd(Op0, Op1);
789 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
791 if (Op1I->getOpcode() == Instruction::And &&
792 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
793 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
796 InsertNewInstBefore(BinaryOperator::createNot(OtherOp, "B.not"), I);
797 return BinaryOperator::createAnd(Op0, NewNot);
800 // -(X sdiv C) -> (X sdiv -C)
801 if (Op1I->getOpcode() == Instruction::Div)
802 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
803 if (CSI->getValue() == 0)
804 if (Constant *DivRHS = dyn_cast<Constant>(Op1I->getOperand(1)))
805 return BinaryOperator::createDiv(Op1I->getOperand(0),
806 ConstantExpr::getNeg(DivRHS));
808 // X - X*C --> X * (1-C)
810 if (dyn_castFoldableMul(Op1I, C2) == Op0) {
812 ConstantExpr::getSub(ConstantInt::get(I.getType(), 1), C2);
813 return BinaryOperator::createMul(Op0, CP1);
819 if (Value *X = dyn_castFoldableMul(Op0, C1)) {
820 if (X == Op1) { // X*C - X --> X * (C-1)
821 Constant *CP1 = ConstantExpr::getSub(C1, ConstantInt::get(I.getType(),1));
822 return BinaryOperator::createMul(Op1, CP1);
825 ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2)
826 if (X == dyn_castFoldableMul(Op1, C2))
827 return BinaryOperator::createMul(Op1, ConstantExpr::getSub(C1, C2));
832 /// isSignBitCheck - Given an exploded setcc instruction, return true if it is
833 /// really just returns true if the most significant (sign) bit is set.
834 static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
835 if (RHS->getType()->isSigned()) {
836 // True if source is LHS < 0 or LHS <= -1
837 return Opcode == Instruction::SetLT && RHS->isNullValue() ||
838 Opcode == Instruction::SetLE && RHS->isAllOnesValue();
840 ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
841 // True if source is LHS > 127 or LHS >= 128, where the constants depend on
842 // the size of the integer type.
843 if (Opcode == Instruction::SetGE)
844 return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1);
845 if (Opcode == Instruction::SetGT)
846 return RHSC->getValue() ==
847 (1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
852 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
853 bool Changed = SimplifyCommutative(I);
854 Value *Op0 = I.getOperand(0);
856 if (isa<UndefValue>(I.getOperand(1))) // undef * X -> 0
857 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
859 // Simplify mul instructions with a constant RHS...
860 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
861 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
863 // ((X << C1)*C2) == (X * (C2 << C1))
864 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
865 if (SI->getOpcode() == Instruction::Shl)
866 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
867 return BinaryOperator::createMul(SI->getOperand(0),
868 ConstantExpr::getShl(CI, ShOp));
870 if (CI->isNullValue())
871 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
872 if (CI->equalsInt(1)) // X * 1 == X
873 return ReplaceInstUsesWith(I, Op0);
874 if (CI->isAllOnesValue()) // X * -1 == 0 - X
875 return BinaryOperator::createNeg(Op0, I.getName());
877 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
878 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
879 return new ShiftInst(Instruction::Shl, Op0,
880 ConstantUInt::get(Type::UByteTy, C));
881 } else if (ConstantFP *Op1F = dyn_cast<ConstantFP>(Op1)) {
882 if (Op1F->isNullValue())
883 return ReplaceInstUsesWith(I, Op1);
885 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
886 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
887 if (Op1F->getValue() == 1.0)
888 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
891 // Try to fold constant mul into select arguments.
892 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
893 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
896 if (isa<PHINode>(Op0))
897 if (Instruction *NV = FoldOpIntoPhi(I))
901 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
902 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
903 return BinaryOperator::createMul(Op0v, Op1v);
905 // If one of the operands of the multiply is a cast from a boolean value, then
906 // we know the bool is either zero or one, so this is a 'masking' multiply.
907 // See if we can simplify things based on how the boolean was originally
909 CastInst *BoolCast = 0;
910 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
911 if (CI->getOperand(0)->getType() == Type::BoolTy)
914 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
915 if (CI->getOperand(0)->getType() == Type::BoolTy)
918 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
919 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
920 const Type *SCOpTy = SCIOp0->getType();
922 // If the setcc is true iff the sign bit of X is set, then convert this
923 // multiply into a shift/and combination.
924 if (isa<ConstantInt>(SCIOp1) &&
925 isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
926 // Shift the X value right to turn it into "all signbits".
927 Constant *Amt = ConstantUInt::get(Type::UByteTy,
928 SCOpTy->getPrimitiveSize()*8-1);
929 if (SCIOp0->getType()->isUnsigned()) {
930 const Type *NewTy = SCIOp0->getType()->getSignedVersion();
931 SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
932 SCIOp0->getName()), I);
936 InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
937 BoolCast->getOperand(0)->getName()+
940 // If the multiply type is not the same as the source type, sign extend
941 // or truncate to the multiply type.
942 if (I.getType() != V->getType())
943 V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
945 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
946 return BinaryOperator::createAnd(V, OtherOp);
951 return Changed ? &I : 0;
954 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
955 if (isa<UndefValue>(I.getOperand(0))) // undef / X -> 0
956 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
957 if (isa<UndefValue>(I.getOperand(1)))
958 return ReplaceInstUsesWith(I, I.getOperand(1)); // X / undef -> undef
960 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
962 if (RHS->equalsInt(1))
963 return ReplaceInstUsesWith(I, I.getOperand(0));
966 if (RHS->isAllOnesValue())
967 return BinaryOperator::createNeg(I.getOperand(0));
969 if (Instruction *LHS = dyn_cast<Instruction>(I.getOperand(0)))
970 if (LHS->getOpcode() == Instruction::Div)
971 if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
972 // (X / C1) / C2 -> X / (C1*C2)
973 return BinaryOperator::createDiv(LHS->getOperand(0),
974 ConstantExpr::getMul(RHS, LHSRHS));
977 // Check to see if this is an unsigned division with an exact power of 2,
978 // if so, convert to a right shift.
979 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
980 if (uint64_t Val = C->getValue()) // Don't break X / 0
981 if (uint64_t C = Log2(Val))
982 return new ShiftInst(Instruction::Shr, I.getOperand(0),
983 ConstantUInt::get(Type::UByteTy, C));
986 if (RHS->getType()->isSigned())
987 if (Value *LHSNeg = dyn_castNegVal(I.getOperand(0)))
988 return BinaryOperator::createDiv(LHSNeg, ConstantExpr::getNeg(RHS));
990 if (isa<PHINode>(I.getOperand(0)) && !RHS->isNullValue())
991 if (Instruction *NV = FoldOpIntoPhi(I))
995 // 0 / X == 0, we don't need to preserve faults!
996 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
997 if (LHS->equalsInt(0))
998 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1004 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
1005 if (I.getType()->isSigned())
1006 if (Value *RHSNeg = dyn_castNegVal(I.getOperand(1)))
1007 if (!isa<ConstantSInt>(RHSNeg) ||
1008 cast<ConstantSInt>(RHSNeg)->getValue() > 0) {
1010 AddUsesToWorkList(I);
1011 I.setOperand(1, RHSNeg);
1015 if (isa<UndefValue>(I.getOperand(0))) // undef % X -> 0
1016 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1017 if (isa<UndefValue>(I.getOperand(1)))
1018 return ReplaceInstUsesWith(I, I.getOperand(1)); // X % undef -> undef
1020 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
1021 if (RHS->equalsInt(1)) // X % 1 == 0
1022 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1024 // Check to see if this is an unsigned remainder with an exact power of 2,
1025 // if so, convert to a bitwise and.
1026 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
1027 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
1028 if (!(Val & (Val-1))) // Power of 2
1029 return BinaryOperator::createAnd(I.getOperand(0),
1030 ConstantUInt::get(I.getType(), Val-1));
1031 if (isa<PHINode>(I.getOperand(0)) && !RHS->isNullValue())
1032 if (Instruction *NV = FoldOpIntoPhi(I))
1036 // 0 % X == 0, we don't need to preserve faults!
1037 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
1038 if (LHS->equalsInt(0))
1039 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1044 // isMaxValueMinusOne - return true if this is Max-1
1045 static bool isMaxValueMinusOne(const ConstantInt *C) {
1046 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
1047 // Calculate -1 casted to the right type...
1048 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
1049 uint64_t Val = ~0ULL; // All ones
1050 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
1051 return CU->getValue() == Val-1;
1054 const ConstantSInt *CS = cast<ConstantSInt>(C);
1056 // Calculate 0111111111..11111
1057 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
1058 int64_t Val = INT64_MAX; // All ones
1059 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
1060 return CS->getValue() == Val-1;
1063 // isMinValuePlusOne - return true if this is Min+1
1064 static bool isMinValuePlusOne(const ConstantInt *C) {
1065 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
1066 return CU->getValue() == 1;
1068 const ConstantSInt *CS = cast<ConstantSInt>(C);
1070 // Calculate 1111111111000000000000
1071 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
1072 int64_t Val = -1; // All ones
1073 Val <<= TypeBits-1; // Shift over to the right spot
1074 return CS->getValue() == Val+1;
1077 // isOneBitSet - Return true if there is exactly one bit set in the specified
1079 static bool isOneBitSet(const ConstantInt *CI) {
1080 uint64_t V = CI->getRawValue();
1081 return V && (V & (V-1)) == 0;
1084 #if 0 // Currently unused
1085 // isLowOnes - Return true if the constant is of the form 0+1+.
1086 static bool isLowOnes(const ConstantInt *CI) {
1087 uint64_t V = CI->getRawValue();
1089 // There won't be bits set in parts that the type doesn't contain.
1090 V &= ConstantInt::getAllOnesValue(CI->getType())->getRawValue();
1092 uint64_t U = V+1; // If it is low ones, this should be a power of two.
1093 return U && V && (U & V) == 0;
1097 // isHighOnes - Return true if the constant is of the form 1+0+.
1098 // This is the same as lowones(~X).
1099 static bool isHighOnes(const ConstantInt *CI) {
1100 uint64_t V = ~CI->getRawValue();
1102 // There won't be bits set in parts that the type doesn't contain.
1103 V &= ConstantInt::getAllOnesValue(CI->getType())->getRawValue();
1105 uint64_t U = V+1; // If it is low ones, this should be a power of two.
1106 return U && V && (U & V) == 0;
1110 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
1111 /// are carefully arranged to allow folding of expressions such as:
1113 /// (A < B) | (A > B) --> (A != B)
1115 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
1116 /// represents that the comparison is true if A == B, and bit value '1' is true
1119 static unsigned getSetCondCode(const SetCondInst *SCI) {
1120 switch (SCI->getOpcode()) {
1122 case Instruction::SetGT: return 1;
1123 case Instruction::SetEQ: return 2;
1124 case Instruction::SetGE: return 3;
1125 case Instruction::SetLT: return 4;
1126 case Instruction::SetNE: return 5;
1127 case Instruction::SetLE: return 6;
1130 assert(0 && "Invalid SetCC opcode!");
1135 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
1136 /// opcode and two operands into either a constant true or false, or a brand new
1137 /// SetCC instruction.
1138 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
1140 case 0: return ConstantBool::False;
1141 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
1142 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
1143 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
1144 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
1145 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
1146 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
1147 case 7: return ConstantBool::True;
1148 default: assert(0 && "Illegal SetCCCode!"); return 0;
1152 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1153 struct FoldSetCCLogical {
1156 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
1157 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
1158 bool shouldApply(Value *V) const {
1159 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
1160 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
1161 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
1164 Instruction *apply(BinaryOperator &Log) const {
1165 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
1166 if (SCI->getOperand(0) != LHS) {
1167 assert(SCI->getOperand(1) == LHS);
1168 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
1171 unsigned LHSCode = getSetCondCode(SCI);
1172 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
1174 switch (Log.getOpcode()) {
1175 case Instruction::And: Code = LHSCode & RHSCode; break;
1176 case Instruction::Or: Code = LHSCode | RHSCode; break;
1177 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
1178 default: assert(0 && "Illegal logical opcode!"); return 0;
1181 Value *RV = getSetCCValue(Code, LHS, RHS);
1182 if (Instruction *I = dyn_cast<Instruction>(RV))
1184 // Otherwise, it's a constant boolean value...
1185 return IC.ReplaceInstUsesWith(Log, RV);
1190 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
1191 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
1192 // guaranteed to be either a shift instruction or a binary operator.
1193 Instruction *InstCombiner::OptAndOp(Instruction *Op,
1194 ConstantIntegral *OpRHS,
1195 ConstantIntegral *AndRHS,
1196 BinaryOperator &TheAnd) {
1197 Value *X = Op->getOperand(0);
1198 Constant *Together = 0;
1199 if (!isa<ShiftInst>(Op))
1200 Together = ConstantExpr::getAnd(AndRHS, OpRHS);
1202 switch (Op->getOpcode()) {
1203 case Instruction::Xor:
1204 if (Together->isNullValue()) {
1205 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
1206 return BinaryOperator::createAnd(X, AndRHS);
1207 } else if (Op->hasOneUse()) {
1208 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
1209 std::string OpName = Op->getName(); Op->setName("");
1210 Instruction *And = BinaryOperator::createAnd(X, AndRHS, OpName);
1211 InsertNewInstBefore(And, TheAnd);
1212 return BinaryOperator::createXor(And, Together);
1215 case Instruction::Or:
1216 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
1217 if (Together->isNullValue())
1218 return BinaryOperator::createAnd(X, AndRHS);
1220 if (Together == AndRHS) // (X | C) & C --> C
1221 return ReplaceInstUsesWith(TheAnd, AndRHS);
1223 if (Op->hasOneUse() && Together != OpRHS) {
1224 // (X | C1) & C2 --> (X | (C1&C2)) & C2
1225 std::string Op0Name = Op->getName(); Op->setName("");
1226 Instruction *Or = BinaryOperator::createOr(X, Together, Op0Name);
1227 InsertNewInstBefore(Or, TheAnd);
1228 return BinaryOperator::createAnd(Or, AndRHS);
1232 case Instruction::Add:
1233 if (Op->hasOneUse()) {
1234 // Adding a one to a single bit bit-field should be turned into an XOR
1235 // of the bit. First thing to check is to see if this AND is with a
1236 // single bit constant.
1237 uint64_t AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
1239 // Clear bits that are not part of the constant.
1240 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
1242 // If there is only one bit set...
1243 if (isOneBitSet(cast<ConstantInt>(AndRHS))) {
1244 // Ok, at this point, we know that we are masking the result of the
1245 // ADD down to exactly one bit. If the constant we are adding has
1246 // no bits set below this bit, then we can eliminate the ADD.
1247 uint64_t AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
1249 // Check to see if any bits below the one bit set in AndRHSV are set.
1250 if ((AddRHS & (AndRHSV-1)) == 0) {
1251 // If not, the only thing that can effect the output of the AND is
1252 // the bit specified by AndRHSV. If that bit is set, the effect of
1253 // the XOR is to toggle the bit. If it is clear, then the ADD has
1255 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
1256 TheAnd.setOperand(0, X);
1259 std::string Name = Op->getName(); Op->setName("");
1260 // Pull the XOR out of the AND.
1261 Instruction *NewAnd = BinaryOperator::createAnd(X, AndRHS, Name);
1262 InsertNewInstBefore(NewAnd, TheAnd);
1263 return BinaryOperator::createXor(NewAnd, AndRHS);
1270 case Instruction::Shl: {
1271 // We know that the AND will not produce any of the bits shifted in, so if
1272 // the anded constant includes them, clear them now!
1274 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1275 Constant *ShlMask = ConstantExpr::getShl(AllOne, OpRHS);
1276 Constant *CI = ConstantExpr::getAnd(AndRHS, ShlMask);
1278 if (CI == ShlMask) { // Masking out bits that the shift already masks
1279 return ReplaceInstUsesWith(TheAnd, Op); // No need for the and.
1280 } else if (CI != AndRHS) { // Reducing bits set in and.
1281 TheAnd.setOperand(1, CI);
1286 case Instruction::Shr:
1287 // We know that the AND will not produce any of the bits shifted in, so if
1288 // the anded constant includes them, clear them now! This only applies to
1289 // unsigned shifts, because a signed shr may bring in set bits!
1291 if (AndRHS->getType()->isUnsigned()) {
1292 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1293 Constant *ShrMask = ConstantExpr::getShr(AllOne, OpRHS);
1294 Constant *CI = ConstantExpr::getAnd(AndRHS, ShrMask);
1296 if (CI == ShrMask) { // Masking out bits that the shift already masks.
1297 return ReplaceInstUsesWith(TheAnd, Op);
1298 } else if (CI != AndRHS) {
1299 TheAnd.setOperand(1, CI); // Reduce bits set in and cst.
1302 } else { // Signed shr.
1303 // See if this is shifting in some sign extension, then masking it out
1305 if (Op->hasOneUse()) {
1306 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1307 Constant *ShrMask = ConstantExpr::getUShr(AllOne, OpRHS);
1308 Constant *CI = ConstantExpr::getAnd(AndRHS, ShrMask);
1309 if (CI == AndRHS) { // Masking out bits shifted in.
1310 // Make the argument unsigned.
1311 Value *ShVal = Op->getOperand(0);
1312 ShVal = InsertCastBefore(ShVal,
1313 ShVal->getType()->getUnsignedVersion(),
1315 ShVal = InsertNewInstBefore(new ShiftInst(Instruction::Shr, ShVal,
1316 OpRHS, Op->getName()),
1318 Value *AndRHS2 = ConstantExpr::getCast(AndRHS, ShVal->getType());
1319 ShVal = InsertNewInstBefore(BinaryOperator::createAnd(ShVal, AndRHS2,
1322 return new CastInst(ShVal, Op->getType());
1332 /// InsertRangeTest - Emit a computation of: (V >= Lo && V < Hi) if Inside is
1333 /// true, otherwise (V < Lo || V >= Hi). In pratice, we emit the more efficient
1334 /// (V-Lo) <u Hi-Lo. This method expects that Lo <= Hi. IB is the location to
1335 /// insert new instructions.
1336 Instruction *InstCombiner::InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
1337 bool Inside, Instruction &IB) {
1338 assert(cast<ConstantBool>(ConstantExpr::getSetLE(Lo, Hi))->getValue() &&
1339 "Lo is not <= Hi in range emission code!");
1341 if (Lo == Hi) // Trivially false.
1342 return new SetCondInst(Instruction::SetNE, V, V);
1343 if (cast<ConstantIntegral>(Lo)->isMinValue())
1344 return new SetCondInst(Instruction::SetLT, V, Hi);
1346 Constant *AddCST = ConstantExpr::getNeg(Lo);
1347 Instruction *Add = BinaryOperator::createAdd(V, AddCST,V->getName()+".off");
1348 InsertNewInstBefore(Add, IB);
1349 // Convert to unsigned for the comparison.
1350 const Type *UnsType = Add->getType()->getUnsignedVersion();
1351 Value *OffsetVal = InsertCastBefore(Add, UnsType, IB);
1352 AddCST = ConstantExpr::getAdd(AddCST, Hi);
1353 AddCST = ConstantExpr::getCast(AddCST, UnsType);
1354 return new SetCondInst(Instruction::SetLT, OffsetVal, AddCST);
1357 if (Lo == Hi) // Trivially true.
1358 return new SetCondInst(Instruction::SetEQ, V, V);
1360 Hi = SubOne(cast<ConstantInt>(Hi));
1361 if (cast<ConstantIntegral>(Lo)->isMinValue()) // V < 0 || V >= Hi ->'V > Hi-1'
1362 return new SetCondInst(Instruction::SetGT, V, Hi);
1364 // Emit X-Lo > Hi-Lo-1
1365 Constant *AddCST = ConstantExpr::getNeg(Lo);
1366 Instruction *Add = BinaryOperator::createAdd(V, AddCST, V->getName()+".off");
1367 InsertNewInstBefore(Add, IB);
1368 // Convert to unsigned for the comparison.
1369 const Type *UnsType = Add->getType()->getUnsignedVersion();
1370 Value *OffsetVal = InsertCastBefore(Add, UnsType, IB);
1371 AddCST = ConstantExpr::getAdd(AddCST, Hi);
1372 AddCST = ConstantExpr::getCast(AddCST, UnsType);
1373 return new SetCondInst(Instruction::SetGT, OffsetVal, AddCST);
1377 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
1378 bool Changed = SimplifyCommutative(I);
1379 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1381 if (isa<UndefValue>(Op1)) // X & undef -> 0
1382 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1384 // and X, X = X and X, 0 == 0
1385 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1386 return ReplaceInstUsesWith(I, Op1);
1389 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1390 if (RHS->isAllOnesValue())
1391 return ReplaceInstUsesWith(I, Op0);
1393 // Optimize a variety of ((val OP C1) & C2) combinations...
1394 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
1395 Instruction *Op0I = cast<Instruction>(Op0);
1396 Value *X = Op0I->getOperand(0);
1397 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1398 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
1402 // Try to fold constant and into select arguments.
1403 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1404 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1406 if (isa<PHINode>(Op0))
1407 if (Instruction *NV = FoldOpIntoPhi(I))
1411 Value *Op0NotVal = dyn_castNotVal(Op0);
1412 Value *Op1NotVal = dyn_castNotVal(Op1);
1414 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1415 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1417 // (~A & ~B) == (~(A | B)) - De Morgan's Law
1418 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1419 Instruction *Or = BinaryOperator::createOr(Op0NotVal, Op1NotVal,
1420 I.getName()+".demorgan");
1421 InsertNewInstBefore(Or, I);
1422 return BinaryOperator::createNot(Or);
1425 if (SetCondInst *RHS = dyn_cast<SetCondInst>(Op1)) {
1426 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1427 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1430 Value *LHSVal, *RHSVal;
1431 ConstantInt *LHSCst, *RHSCst;
1432 Instruction::BinaryOps LHSCC, RHSCC;
1433 if (match(Op0, m_SetCond(LHSCC, m_Value(LHSVal), m_ConstantInt(LHSCst))))
1434 if (match(RHS, m_SetCond(RHSCC, m_Value(RHSVal), m_ConstantInt(RHSCst))))
1435 if (LHSVal == RHSVal && // Found (X setcc C1) & (X setcc C2)
1436 // Set[GL]E X, CST is folded to Set[GL]T elsewhere.
1437 LHSCC != Instruction::SetGE && LHSCC != Instruction::SetLE &&
1438 RHSCC != Instruction::SetGE && RHSCC != Instruction::SetLE) {
1439 // Ensure that the larger constant is on the RHS.
1440 Constant *Cmp = ConstantExpr::getSetGT(LHSCst, RHSCst);
1441 SetCondInst *LHS = cast<SetCondInst>(Op0);
1442 if (cast<ConstantBool>(Cmp)->getValue()) {
1443 std::swap(LHS, RHS);
1444 std::swap(LHSCst, RHSCst);
1445 std::swap(LHSCC, RHSCC);
1448 // At this point, we know we have have two setcc instructions
1449 // comparing a value against two constants and and'ing the result
1450 // together. Because of the above check, we know that we only have
1451 // SetEQ, SetNE, SetLT, and SetGT here. We also know (from the
1452 // FoldSetCCLogical check above), that the two constants are not
1454 assert(LHSCst != RHSCst && "Compares not folded above?");
1457 default: assert(0 && "Unknown integer condition code!");
1458 case Instruction::SetEQ:
1460 default: assert(0 && "Unknown integer condition code!");
1461 case Instruction::SetEQ: // (X == 13 & X == 15) -> false
1462 case Instruction::SetGT: // (X == 13 & X > 15) -> false
1463 return ReplaceInstUsesWith(I, ConstantBool::False);
1464 case Instruction::SetNE: // (X == 13 & X != 15) -> X == 13
1465 case Instruction::SetLT: // (X == 13 & X < 15) -> X == 13
1466 return ReplaceInstUsesWith(I, LHS);
1468 case Instruction::SetNE:
1470 default: assert(0 && "Unknown integer condition code!");
1471 case Instruction::SetLT:
1472 if (LHSCst == SubOne(RHSCst)) // (X != 13 & X < 14) -> X < 13
1473 return new SetCondInst(Instruction::SetLT, LHSVal, LHSCst);
1474 break; // (X != 13 & X < 15) -> no change
1475 case Instruction::SetEQ: // (X != 13 & X == 15) -> X == 15
1476 case Instruction::SetGT: // (X != 13 & X > 15) -> X > 15
1477 return ReplaceInstUsesWith(I, RHS);
1478 case Instruction::SetNE:
1479 if (LHSCst == SubOne(RHSCst)) {// (X != 13 & X != 14) -> X-13 >u 1
1480 Constant *AddCST = ConstantExpr::getNeg(LHSCst);
1481 Instruction *Add = BinaryOperator::createAdd(LHSVal, AddCST,
1482 LHSVal->getName()+".off");
1483 InsertNewInstBefore(Add, I);
1484 const Type *UnsType = Add->getType()->getUnsignedVersion();
1485 Value *OffsetVal = InsertCastBefore(Add, UnsType, I);
1486 AddCST = ConstantExpr::getSub(RHSCst, LHSCst);
1487 AddCST = ConstantExpr::getCast(AddCST, UnsType);
1488 return new SetCondInst(Instruction::SetGT, OffsetVal, AddCST);
1490 break; // (X != 13 & X != 15) -> no change
1493 case Instruction::SetLT:
1495 default: assert(0 && "Unknown integer condition code!");
1496 case Instruction::SetEQ: // (X < 13 & X == 15) -> false
1497 case Instruction::SetGT: // (X < 13 & X > 15) -> false
1498 return ReplaceInstUsesWith(I, ConstantBool::False);
1499 case Instruction::SetNE: // (X < 13 & X != 15) -> X < 13
1500 case Instruction::SetLT: // (X < 13 & X < 15) -> X < 13
1501 return ReplaceInstUsesWith(I, LHS);
1503 case Instruction::SetGT:
1505 default: assert(0 && "Unknown integer condition code!");
1506 case Instruction::SetEQ: // (X > 13 & X == 15) -> X > 13
1507 return ReplaceInstUsesWith(I, LHS);
1508 case Instruction::SetGT: // (X > 13 & X > 15) -> X > 15
1509 return ReplaceInstUsesWith(I, RHS);
1510 case Instruction::SetNE:
1511 if (RHSCst == AddOne(LHSCst)) // (X > 13 & X != 14) -> X > 14
1512 return new SetCondInst(Instruction::SetGT, LHSVal, RHSCst);
1513 break; // (X > 13 & X != 15) -> no change
1514 case Instruction::SetLT: // (X > 13 & X < 15) -> (X-14) <u 1
1515 return InsertRangeTest(LHSVal, AddOne(LHSCst), RHSCst, true, I);
1521 return Changed ? &I : 0;
1524 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1525 bool Changed = SimplifyCommutative(I);
1526 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1528 if (isa<UndefValue>(Op1))
1529 return ReplaceInstUsesWith(I, // X | undef -> -1
1530 ConstantIntegral::getAllOnesValue(I.getType()));
1532 // or X, X = X or X, 0 == X
1533 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1534 return ReplaceInstUsesWith(I, Op0);
1537 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1538 if (RHS->isAllOnesValue())
1539 return ReplaceInstUsesWith(I, Op1);
1541 ConstantInt *C1; Value *X;
1542 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1543 if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))) && isOnlyUse(Op0)) {
1544 std::string Op0Name = Op0->getName(); Op0->setName("");
1545 Instruction *Or = BinaryOperator::createOr(X, RHS, Op0Name);
1546 InsertNewInstBefore(Or, I);
1547 return BinaryOperator::createAnd(Or, ConstantExpr::getOr(RHS, C1));
1550 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1551 if (match(Op0, m_Xor(m_Value(X), m_ConstantInt(C1))) && isOnlyUse(Op0)) {
1552 std::string Op0Name = Op0->getName(); Op0->setName("");
1553 Instruction *Or = BinaryOperator::createOr(X, RHS, Op0Name);
1554 InsertNewInstBefore(Or, I);
1555 return BinaryOperator::createXor(Or,
1556 ConstantExpr::getAnd(C1, ConstantExpr::getNot(RHS)));
1559 // Try to fold constant and into select arguments.
1560 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1561 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1563 if (isa<PHINode>(Op0))
1564 if (Instruction *NV = FoldOpIntoPhi(I))
1568 // (A & C1)|(A & C2) == A & (C1|C2)
1569 Value *A, *B; ConstantInt *C1, *C2;
1570 if (match(Op0, m_And(m_Value(A), m_ConstantInt(C1))) &&
1571 match(Op1, m_And(m_Value(B), m_ConstantInt(C2))) && A == B)
1572 return BinaryOperator::createAnd(A, ConstantExpr::getOr(C1, C2));
1574 if (match(Op0, m_Not(m_Value(A)))) { // ~A | Op1
1575 if (A == Op1) // ~A | A == -1
1576 return ReplaceInstUsesWith(I,
1577 ConstantIntegral::getAllOnesValue(I.getType()));
1582 if (match(Op1, m_Not(m_Value(B)))) { // Op0 | ~B
1584 return ReplaceInstUsesWith(I,
1585 ConstantIntegral::getAllOnesValue(I.getType()));
1587 // (~A | ~B) == (~(A & B)) - De Morgan's Law
1588 if (A && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1589 Value *And = InsertNewInstBefore(BinaryOperator::createAnd(A, B,
1590 I.getName()+".demorgan"), I);
1591 return BinaryOperator::createNot(And);
1595 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1596 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1))) {
1597 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1600 Value *LHSVal, *RHSVal;
1601 ConstantInt *LHSCst, *RHSCst;
1602 Instruction::BinaryOps LHSCC, RHSCC;
1603 if (match(Op0, m_SetCond(LHSCC, m_Value(LHSVal), m_ConstantInt(LHSCst))))
1604 if (match(RHS, m_SetCond(RHSCC, m_Value(RHSVal), m_ConstantInt(RHSCst))))
1605 if (LHSVal == RHSVal && // Found (X setcc C1) | (X setcc C2)
1606 // Set[GL]E X, CST is folded to Set[GL]T elsewhere.
1607 LHSCC != Instruction::SetGE && LHSCC != Instruction::SetLE &&
1608 RHSCC != Instruction::SetGE && RHSCC != Instruction::SetLE) {
1609 // Ensure that the larger constant is on the RHS.
1610 Constant *Cmp = ConstantExpr::getSetGT(LHSCst, RHSCst);
1611 SetCondInst *LHS = cast<SetCondInst>(Op0);
1612 if (cast<ConstantBool>(Cmp)->getValue()) {
1613 std::swap(LHS, RHS);
1614 std::swap(LHSCst, RHSCst);
1615 std::swap(LHSCC, RHSCC);
1618 // At this point, we know we have have two setcc instructions
1619 // comparing a value against two constants and or'ing the result
1620 // together. Because of the above check, we know that we only have
1621 // SetEQ, SetNE, SetLT, and SetGT here. We also know (from the
1622 // FoldSetCCLogical check above), that the two constants are not
1624 assert(LHSCst != RHSCst && "Compares not folded above?");
1627 default: assert(0 && "Unknown integer condition code!");
1628 case Instruction::SetEQ:
1630 default: assert(0 && "Unknown integer condition code!");
1631 case Instruction::SetEQ:
1632 if (LHSCst == SubOne(RHSCst)) {// (X == 13 | X == 14) -> X-13 <u 2
1633 Constant *AddCST = ConstantExpr::getNeg(LHSCst);
1634 Instruction *Add = BinaryOperator::createAdd(LHSVal, AddCST,
1635 LHSVal->getName()+".off");
1636 InsertNewInstBefore(Add, I);
1637 const Type *UnsType = Add->getType()->getUnsignedVersion();
1638 Value *OffsetVal = InsertCastBefore(Add, UnsType, I);
1639 AddCST = ConstantExpr::getSub(AddOne(RHSCst), LHSCst);
1640 AddCST = ConstantExpr::getCast(AddCST, UnsType);
1641 return new SetCondInst(Instruction::SetLT, OffsetVal, AddCST);
1643 break; // (X == 13 | X == 15) -> no change
1645 case Instruction::SetGT:
1646 if (LHSCst == SubOne(RHSCst)) // (X == 13 | X > 14) -> X > 13
1647 return new SetCondInst(Instruction::SetGT, LHSVal, LHSCst);
1648 break; // (X == 13 | X > 15) -> no change
1649 case Instruction::SetNE: // (X == 13 | X != 15) -> X != 15
1650 case Instruction::SetLT: // (X == 13 | X < 15) -> X < 15
1651 return ReplaceInstUsesWith(I, RHS);
1654 case Instruction::SetNE:
1656 default: assert(0 && "Unknown integer condition code!");
1657 case Instruction::SetLT: // (X != 13 | X < 15) -> X < 15
1658 return ReplaceInstUsesWith(I, RHS);
1659 case Instruction::SetEQ: // (X != 13 | X == 15) -> X != 13
1660 case Instruction::SetGT: // (X != 13 | X > 15) -> X != 13
1661 return ReplaceInstUsesWith(I, LHS);
1662 case Instruction::SetNE: // (X != 13 | X != 15) -> true
1663 return ReplaceInstUsesWith(I, ConstantBool::True);
1666 case Instruction::SetLT:
1668 default: assert(0 && "Unknown integer condition code!");
1669 case Instruction::SetEQ: // (X < 13 | X == 14) -> no change
1671 case Instruction::SetGT: // (X < 13 | X > 15) -> (X-13) > 2
1672 return InsertRangeTest(LHSVal, LHSCst, AddOne(RHSCst), false, I);
1673 case Instruction::SetNE: // (X < 13 | X != 15) -> X != 15
1674 case Instruction::SetLT: // (X < 13 | X < 15) -> X < 15
1675 return ReplaceInstUsesWith(I, RHS);
1678 case Instruction::SetGT:
1680 default: assert(0 && "Unknown integer condition code!");
1681 case Instruction::SetEQ: // (X > 13 | X == 15) -> X > 13
1682 case Instruction::SetGT: // (X > 13 | X > 15) -> X > 13
1683 return ReplaceInstUsesWith(I, LHS);
1684 case Instruction::SetNE: // (X > 13 | X != 15) -> true
1685 case Instruction::SetLT: // (X > 13 | X < 15) -> true
1686 return ReplaceInstUsesWith(I, ConstantBool::True);
1691 return Changed ? &I : 0;
1694 // XorSelf - Implements: X ^ X --> 0
1697 XorSelf(Value *rhs) : RHS(rhs) {}
1698 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1699 Instruction *apply(BinaryOperator &Xor) const {
1705 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1706 bool Changed = SimplifyCommutative(I);
1707 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1709 if (isa<UndefValue>(Op1))
1710 return ReplaceInstUsesWith(I, Op1); // X ^ undef -> undef
1712 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1713 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1714 assert(Result == &I && "AssociativeOpt didn't work?");
1715 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1718 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1720 if (RHS->isNullValue())
1721 return ReplaceInstUsesWith(I, Op0);
1723 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1724 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1725 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1726 if (RHS == ConstantBool::True && SCI->hasOneUse())
1727 return new SetCondInst(SCI->getInverseCondition(),
1728 SCI->getOperand(0), SCI->getOperand(1));
1730 // ~(c-X) == X-c-1 == X+(-c-1)
1731 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1732 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1733 Constant *NegOp0I0C = ConstantExpr::getNeg(Op0I0C);
1734 Constant *ConstantRHS = ConstantExpr::getSub(NegOp0I0C,
1735 ConstantInt::get(I.getType(), 1));
1736 return BinaryOperator::createAdd(Op0I->getOperand(1), ConstantRHS);
1739 // ~(~X & Y) --> (X | ~Y)
1740 if (Op0I->getOpcode() == Instruction::And && RHS->isAllOnesValue()) {
1741 if (dyn_castNotVal(Op0I->getOperand(1))) Op0I->swapOperands();
1742 if (Value *Op0NotVal = dyn_castNotVal(Op0I->getOperand(0))) {
1744 BinaryOperator::createNot(Op0I->getOperand(1),
1745 Op0I->getOperand(1)->getName()+".not");
1746 InsertNewInstBefore(NotY, I);
1747 return BinaryOperator::createOr(Op0NotVal, NotY);
1751 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1752 switch (Op0I->getOpcode()) {
1753 case Instruction::Add:
1754 // ~(X-c) --> (-c-1)-X
1755 if (RHS->isAllOnesValue()) {
1756 Constant *NegOp0CI = ConstantExpr::getNeg(Op0CI);
1757 return BinaryOperator::createSub(
1758 ConstantExpr::getSub(NegOp0CI,
1759 ConstantInt::get(I.getType(), 1)),
1760 Op0I->getOperand(0));
1763 case Instruction::And:
1764 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1765 if (ConstantExpr::getAnd(RHS, Op0CI)->isNullValue())
1766 return BinaryOperator::createOr(Op0, RHS);
1768 case Instruction::Or:
1769 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1770 if (ConstantExpr::getAnd(RHS, Op0CI) == RHS)
1771 return BinaryOperator::createAnd(Op0, ConstantExpr::getNot(RHS));
1777 // Try to fold constant and into select arguments.
1778 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1779 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1781 if (isa<PHINode>(Op0))
1782 if (Instruction *NV = FoldOpIntoPhi(I))
1786 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1788 return ReplaceInstUsesWith(I,
1789 ConstantIntegral::getAllOnesValue(I.getType()));
1791 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1793 return ReplaceInstUsesWith(I,
1794 ConstantIntegral::getAllOnesValue(I.getType()));
1796 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1797 if (Op1I->getOpcode() == Instruction::Or) {
1798 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1799 cast<BinaryOperator>(Op1I)->swapOperands();
1801 std::swap(Op0, Op1);
1802 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1804 std::swap(Op0, Op1);
1806 } else if (Op1I->getOpcode() == Instruction::Xor) {
1807 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1808 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1809 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1810 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1813 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1814 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1815 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1816 cast<BinaryOperator>(Op0I)->swapOperands();
1817 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1818 Value *NotB = InsertNewInstBefore(BinaryOperator::createNot(Op1,
1819 Op1->getName()+".not"), I);
1820 return BinaryOperator::createAnd(Op0I->getOperand(0), NotB);
1822 } else if (Op0I->getOpcode() == Instruction::Xor) {
1823 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1824 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1825 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1826 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1829 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
1830 Value *A, *B; ConstantInt *C1, *C2;
1831 if (match(Op0, m_And(m_Value(A), m_ConstantInt(C1))) &&
1832 match(Op1, m_And(m_Value(B), m_ConstantInt(C2))) &&
1833 ConstantExpr::getAnd(C1, C2)->isNullValue())
1834 return BinaryOperator::createOr(Op0, Op1);
1836 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1837 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1838 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1841 return Changed ? &I : 0;
1844 /// MulWithOverflow - Compute Result = In1*In2, returning true if the result
1845 /// overflowed for this type.
1846 static bool MulWithOverflow(ConstantInt *&Result, ConstantInt *In1,
1848 Result = cast<ConstantInt>(ConstantExpr::getMul(In1, In2));
1849 return !In2->isNullValue() && ConstantExpr::getDiv(Result, In2) != In1;
1852 static bool isPositive(ConstantInt *C) {
1853 return cast<ConstantSInt>(C)->getValue() >= 0;
1856 /// AddWithOverflow - Compute Result = In1+In2, returning true if the result
1857 /// overflowed for this type.
1858 static bool AddWithOverflow(ConstantInt *&Result, ConstantInt *In1,
1860 Result = cast<ConstantInt>(ConstantExpr::getAdd(In1, In2));
1862 if (In1->getType()->isUnsigned())
1863 return cast<ConstantUInt>(Result)->getValue() <
1864 cast<ConstantUInt>(In1)->getValue();
1865 if (isPositive(In1) != isPositive(In2))
1867 if (isPositive(In1))
1868 return cast<ConstantSInt>(Result)->getValue() <
1869 cast<ConstantSInt>(In1)->getValue();
1870 return cast<ConstantSInt>(Result)->getValue() >
1871 cast<ConstantSInt>(In1)->getValue();
1874 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1875 bool Changed = SimplifyCommutative(I);
1876 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1877 const Type *Ty = Op0->getType();
1881 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1883 if (isa<UndefValue>(Op1)) // X setcc undef -> undef
1884 return ReplaceInstUsesWith(I, UndefValue::get(Type::BoolTy));
1886 // setcc <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
1887 // addresses never equal each other! We already know that Op0 != Op1.
1888 if ((isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0) ||
1889 isa<ConstantPointerNull>(Op0)) &&
1890 (isa<GlobalValue>(Op1) || isa<AllocaInst>(Op1) ||
1891 isa<ConstantPointerNull>(Op1)))
1892 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1894 // setcc's with boolean values can always be turned into bitwise operations
1895 if (Ty == Type::BoolTy) {
1896 switch (I.getOpcode()) {
1897 default: assert(0 && "Invalid setcc instruction!");
1898 case Instruction::SetEQ: { // seteq bool %A, %B -> ~(A^B)
1899 Instruction *Xor = BinaryOperator::createXor(Op0, Op1, I.getName()+"tmp");
1900 InsertNewInstBefore(Xor, I);
1901 return BinaryOperator::createNot(Xor);
1903 case Instruction::SetNE:
1904 return BinaryOperator::createXor(Op0, Op1);
1906 case Instruction::SetGT:
1907 std::swap(Op0, Op1); // Change setgt -> setlt
1909 case Instruction::SetLT: { // setlt bool A, B -> ~X & Y
1910 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1911 InsertNewInstBefore(Not, I);
1912 return BinaryOperator::createAnd(Not, Op1);
1914 case Instruction::SetGE:
1915 std::swap(Op0, Op1); // Change setge -> setle
1917 case Instruction::SetLE: { // setle bool %A, %B -> ~A | B
1918 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1919 InsertNewInstBefore(Not, I);
1920 return BinaryOperator::createOr(Not, Op1);
1925 // See if we are doing a comparison between a constant and an instruction that
1926 // can be folded into the comparison.
1927 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1928 // Check to see if we are comparing against the minimum or maximum value...
1929 if (CI->isMinValue()) {
1930 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1931 return ReplaceInstUsesWith(I, ConstantBool::False);
1932 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1933 return ReplaceInstUsesWith(I, ConstantBool::True);
1934 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1935 return BinaryOperator::createSetEQ(Op0, Op1);
1936 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1937 return BinaryOperator::createSetNE(Op0, Op1);
1939 } else if (CI->isMaxValue()) {
1940 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1941 return ReplaceInstUsesWith(I, ConstantBool::False);
1942 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1943 return ReplaceInstUsesWith(I, ConstantBool::True);
1944 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1945 return BinaryOperator::createSetEQ(Op0, Op1);
1946 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1947 return BinaryOperator::createSetNE(Op0, Op1);
1949 // Comparing against a value really close to min or max?
1950 } else if (isMinValuePlusOne(CI)) {
1951 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1952 return BinaryOperator::createSetEQ(Op0, SubOne(CI));
1953 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1954 return BinaryOperator::createSetNE(Op0, SubOne(CI));
1956 } else if (isMaxValueMinusOne(CI)) {
1957 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1958 return BinaryOperator::createSetEQ(Op0, AddOne(CI));
1959 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1960 return BinaryOperator::createSetNE(Op0, AddOne(CI));
1963 // If we still have a setle or setge instruction, turn it into the
1964 // appropriate setlt or setgt instruction. Since the border cases have
1965 // already been handled above, this requires little checking.
1967 if (I.getOpcode() == Instruction::SetLE)
1968 return BinaryOperator::createSetLT(Op0, AddOne(CI));
1969 if (I.getOpcode() == Instruction::SetGE)
1970 return BinaryOperator::createSetGT(Op0, SubOne(CI));
1972 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
1973 switch (LHSI->getOpcode()) {
1974 case Instruction::PHI:
1975 if (Instruction *NV = FoldOpIntoPhi(I))
1978 case Instruction::And:
1979 if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
1980 LHSI->getOperand(0)->hasOneUse()) {
1981 // If this is: (X >> C1) & C2 != C3 (where any shift and any compare
1982 // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This
1983 // happens a LOT in code produced by the C front-end, for bitfield
1985 ShiftInst *Shift = dyn_cast<ShiftInst>(LHSI->getOperand(0));
1986 ConstantUInt *ShAmt;
1987 ShAmt = Shift ? dyn_cast<ConstantUInt>(Shift->getOperand(1)) : 0;
1988 ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
1989 const Type *Ty = LHSI->getType();
1991 // We can fold this as long as we can't shift unknown bits
1992 // into the mask. This can only happen with signed shift
1993 // rights, as they sign-extend.
1995 bool CanFold = Shift->getOpcode() != Instruction::Shr ||
1996 Shift->getType()->isUnsigned();
1998 // To test for the bad case of the signed shr, see if any
1999 // of the bits shifted in could be tested after the mask.
2000 Constant *OShAmt = ConstantUInt::get(Type::UByteTy,
2001 Ty->getPrimitiveSize()*8-ShAmt->getValue());
2003 ConstantExpr::getShl(ConstantInt::getAllOnesValue(Ty), OShAmt);
2004 if (ConstantExpr::getAnd(ShVal, AndCST)->isNullValue())
2010 if (Shift->getOpcode() == Instruction::Shl)
2011 NewCst = ConstantExpr::getUShr(CI, ShAmt);
2013 NewCst = ConstantExpr::getShl(CI, ShAmt);
2015 // Check to see if we are shifting out any of the bits being
2017 if (ConstantExpr::get(Shift->getOpcode(), NewCst, ShAmt) != CI){
2018 // If we shifted bits out, the fold is not going to work out.
2019 // As a special case, check to see if this means that the
2020 // result is always true or false now.
2021 if (I.getOpcode() == Instruction::SetEQ)
2022 return ReplaceInstUsesWith(I, ConstantBool::False);
2023 if (I.getOpcode() == Instruction::SetNE)
2024 return ReplaceInstUsesWith(I, ConstantBool::True);
2026 I.setOperand(1, NewCst);
2027 Constant *NewAndCST;
2028 if (Shift->getOpcode() == Instruction::Shl)
2029 NewAndCST = ConstantExpr::getUShr(AndCST, ShAmt);
2031 NewAndCST = ConstantExpr::getShl(AndCST, ShAmt);
2032 LHSI->setOperand(1, NewAndCST);
2033 LHSI->setOperand(0, Shift->getOperand(0));
2034 WorkList.push_back(Shift); // Shift is dead.
2035 AddUsesToWorkList(I);
2043 // (setcc (cast X to larger), CI)
2044 case Instruction::Cast: {
2045 Instruction* replacement =
2046 visitSetCondInstWithCastAndConstant(I,cast<CastInst>(LHSI),CI);
2052 case Instruction::Shl: // (setcc (shl X, ShAmt), CI)
2053 if (ConstantUInt *ShAmt = dyn_cast<ConstantUInt>(LHSI->getOperand(1))) {
2054 switch (I.getOpcode()) {
2056 case Instruction::SetEQ:
2057 case Instruction::SetNE: {
2058 // If we are comparing against bits always shifted out, the
2059 // comparison cannot succeed.
2061 ConstantExpr::getShl(ConstantExpr::getShr(CI, ShAmt), ShAmt);
2062 if (Comp != CI) {// Comparing against a bit that we know is zero.
2063 bool IsSetNE = I.getOpcode() == Instruction::SetNE;
2064 Constant *Cst = ConstantBool::get(IsSetNE);
2065 return ReplaceInstUsesWith(I, Cst);
2068 if (LHSI->hasOneUse()) {
2069 // Otherwise strength reduce the shift into an and.
2070 unsigned ShAmtVal = ShAmt->getValue();
2071 unsigned TypeBits = CI->getType()->getPrimitiveSize()*8;
2072 uint64_t Val = (1ULL << (TypeBits-ShAmtVal))-1;
2075 if (CI->getType()->isUnsigned()) {
2076 Mask = ConstantUInt::get(CI->getType(), Val);
2077 } else if (ShAmtVal != 0) {
2078 Mask = ConstantSInt::get(CI->getType(), Val);
2080 Mask = ConstantInt::getAllOnesValue(CI->getType());
2084 BinaryOperator::createAnd(LHSI->getOperand(0),
2085 Mask, LHSI->getName()+".mask");
2086 Value *And = InsertNewInstBefore(AndI, I);
2087 return new SetCondInst(I.getOpcode(), And,
2088 ConstantExpr::getUShr(CI, ShAmt));
2095 case Instruction::Shr: // (setcc (shr X, ShAmt), CI)
2096 if (ConstantUInt *ShAmt = dyn_cast<ConstantUInt>(LHSI->getOperand(1))) {
2097 switch (I.getOpcode()) {
2099 case Instruction::SetEQ:
2100 case Instruction::SetNE: {
2101 // If we are comparing against bits always shifted out, the
2102 // comparison cannot succeed.
2104 ConstantExpr::getShr(ConstantExpr::getShl(CI, ShAmt), ShAmt);
2106 if (Comp != CI) {// Comparing against a bit that we know is zero.
2107 bool IsSetNE = I.getOpcode() == Instruction::SetNE;
2108 Constant *Cst = ConstantBool::get(IsSetNE);
2109 return ReplaceInstUsesWith(I, Cst);
2112 if (LHSI->hasOneUse() || CI->isNullValue()) {
2113 unsigned ShAmtVal = ShAmt->getValue();
2115 // Otherwise strength reduce the shift into an and.
2116 uint64_t Val = ~0ULL; // All ones.
2117 Val <<= ShAmtVal; // Shift over to the right spot.
2120 if (CI->getType()->isUnsigned()) {
2121 unsigned TypeBits = CI->getType()->getPrimitiveSize()*8;
2122 Val &= (1ULL << TypeBits)-1;
2123 Mask = ConstantUInt::get(CI->getType(), Val);
2125 Mask = ConstantSInt::get(CI->getType(), Val);
2129 BinaryOperator::createAnd(LHSI->getOperand(0),
2130 Mask, LHSI->getName()+".mask");
2131 Value *And = InsertNewInstBefore(AndI, I);
2132 return new SetCondInst(I.getOpcode(), And,
2133 ConstantExpr::getShl(CI, ShAmt));
2141 case Instruction::Div:
2142 // Fold: (div X, C1) op C2 -> range check
2143 if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
2144 // Fold this div into the comparison, producing a range check.
2145 // Determine, based on the divide type, what the range is being
2146 // checked. If there is an overflow on the low or high side, remember
2147 // it, otherwise compute the range [low, hi) bounding the new value.
2148 bool LoOverflow = false, HiOverflow = 0;
2149 ConstantInt *LoBound = 0, *HiBound = 0;
2152 bool ProdOV = MulWithOverflow(Prod, CI, DivRHS);
2154 Instruction::BinaryOps Opcode = I.getOpcode();
2156 if (DivRHS->isNullValue()) { // Don't hack on divide by zeros.
2157 } else if (LHSI->getType()->isUnsigned()) { // udiv
2159 LoOverflow = ProdOV;
2160 HiOverflow = ProdOV || AddWithOverflow(HiBound, LoBound, DivRHS);
2161 } else if (isPositive(DivRHS)) { // Divisor is > 0.
2162 if (CI->isNullValue()) { // (X / pos) op 0
2164 LoBound = cast<ConstantInt>(ConstantExpr::getNeg(SubOne(DivRHS)));
2166 } else if (isPositive(CI)) { // (X / pos) op pos
2168 LoOverflow = ProdOV;
2169 HiOverflow = ProdOV || AddWithOverflow(HiBound, Prod, DivRHS);
2170 } else { // (X / pos) op neg
2171 Constant *DivRHSH = ConstantExpr::getNeg(SubOne(DivRHS));
2172 LoOverflow = AddWithOverflow(LoBound, Prod,
2173 cast<ConstantInt>(DivRHSH));
2175 HiOverflow = ProdOV;
2177 } else { // Divisor is < 0.
2178 if (CI->isNullValue()) { // (X / neg) op 0
2179 LoBound = AddOne(DivRHS);
2180 HiBound = cast<ConstantInt>(ConstantExpr::getNeg(DivRHS));
2181 } else if (isPositive(CI)) { // (X / neg) op pos
2182 HiOverflow = LoOverflow = ProdOV;
2184 LoOverflow = AddWithOverflow(LoBound, Prod, AddOne(DivRHS));
2185 HiBound = AddOne(Prod);
2186 } else { // (X / neg) op neg
2188 LoOverflow = HiOverflow = ProdOV;
2189 HiBound = cast<ConstantInt>(ConstantExpr::getSub(Prod, DivRHS));
2192 // Dividing by a negate swaps the condition.
2193 Opcode = SetCondInst::getSwappedCondition(Opcode);
2197 Value *X = LHSI->getOperand(0);
2199 default: assert(0 && "Unhandled setcc opcode!");
2200 case Instruction::SetEQ:
2201 if (LoOverflow && HiOverflow)
2202 return ReplaceInstUsesWith(I, ConstantBool::False);
2203 else if (HiOverflow)
2204 return new SetCondInst(Instruction::SetGE, X, LoBound);
2205 else if (LoOverflow)
2206 return new SetCondInst(Instruction::SetLT, X, HiBound);
2208 return InsertRangeTest(X, LoBound, HiBound, true, I);
2209 case Instruction::SetNE:
2210 if (LoOverflow && HiOverflow)
2211 return ReplaceInstUsesWith(I, ConstantBool::True);
2212 else if (HiOverflow)
2213 return new SetCondInst(Instruction::SetLT, X, LoBound);
2214 else if (LoOverflow)
2215 return new SetCondInst(Instruction::SetGE, X, HiBound);
2217 return InsertRangeTest(X, LoBound, HiBound, false, I);
2218 case Instruction::SetLT:
2220 return ReplaceInstUsesWith(I, ConstantBool::False);
2221 return new SetCondInst(Instruction::SetLT, X, LoBound);
2222 case Instruction::SetGT:
2224 return ReplaceInstUsesWith(I, ConstantBool::False);
2225 return new SetCondInst(Instruction::SetGE, X, HiBound);
2230 case Instruction::Select:
2231 // If either operand of the select is a constant, we can fold the
2232 // comparison into the select arms, which will cause one to be
2233 // constant folded and the select turned into a bitwise or.
2234 Value *Op1 = 0, *Op2 = 0;
2235 if (LHSI->hasOneUse()) {
2236 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
2237 // Fold the known value into the constant operand.
2238 Op1 = ConstantExpr::get(I.getOpcode(), C, CI);
2239 // Insert a new SetCC of the other select operand.
2240 Op2 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
2241 LHSI->getOperand(2), CI,
2243 } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
2244 // Fold the known value into the constant operand.
2245 Op2 = ConstantExpr::get(I.getOpcode(), C, CI);
2246 // Insert a new SetCC of the other select operand.
2247 Op1 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
2248 LHSI->getOperand(1), CI,
2254 return new SelectInst(LHSI->getOperand(0), Op1, Op2);
2258 // Simplify seteq and setne instructions...
2259 if (I.getOpcode() == Instruction::SetEQ ||
2260 I.getOpcode() == Instruction::SetNE) {
2261 bool isSetNE = I.getOpcode() == Instruction::SetNE;
2263 // If the first operand is (and|or|xor) with a constant, and the second
2264 // operand is a constant, simplify a bit.
2265 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
2266 switch (BO->getOpcode()) {
2267 case Instruction::Rem:
2268 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
2269 if (CI->isNullValue() && isa<ConstantSInt>(BO->getOperand(1)) &&
2271 cast<ConstantSInt>(BO->getOperand(1))->getValue() > 1)
2273 Log2(cast<ConstantSInt>(BO->getOperand(1))->getValue())) {
2274 const Type *UTy = BO->getType()->getUnsignedVersion();
2275 Value *NewX = InsertNewInstBefore(new CastInst(BO->getOperand(0),
2277 Constant *RHSCst = ConstantUInt::get(UTy, 1ULL << L2);
2278 Value *NewRem =InsertNewInstBefore(BinaryOperator::createRem(NewX,
2279 RHSCst, BO->getName()), I);
2280 return BinaryOperator::create(I.getOpcode(), NewRem,
2281 Constant::getNullValue(UTy));
2285 case Instruction::Add:
2286 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
2287 if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) {
2288 if (BO->hasOneUse())
2289 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
2290 ConstantExpr::getSub(CI, BOp1C));
2291 } else if (CI->isNullValue()) {
2292 // Replace ((add A, B) != 0) with (A != -B) if A or B is
2293 // efficiently invertible, or if the add has just this one use.
2294 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
2296 if (Value *NegVal = dyn_castNegVal(BOp1))
2297 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
2298 else if (Value *NegVal = dyn_castNegVal(BOp0))
2299 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
2300 else if (BO->hasOneUse()) {
2301 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
2303 InsertNewInstBefore(Neg, I);
2304 return new SetCondInst(I.getOpcode(), BOp0, Neg);
2308 case Instruction::Xor:
2309 // For the xor case, we can xor two constants together, eliminating
2310 // the explicit xor.
2311 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
2312 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
2313 ConstantExpr::getXor(CI, BOC));
2316 case Instruction::Sub:
2317 // Replace (([sub|xor] A, B) != 0) with (A != B)
2318 if (CI->isNullValue())
2319 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
2323 case Instruction::Or:
2324 // If bits are being or'd in that are not present in the constant we
2325 // are comparing against, then the comparison could never succeed!
2326 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
2327 Constant *NotCI = ConstantExpr::getNot(CI);
2328 if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue())
2329 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
2333 case Instruction::And:
2334 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
2335 // If bits are being compared against that are and'd out, then the
2336 // comparison can never succeed!
2337 if (!ConstantExpr::getAnd(CI,
2338 ConstantExpr::getNot(BOC))->isNullValue())
2339 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
2341 // If we have ((X & C) == C), turn it into ((X & C) != 0).
2342 if (CI == BOC && isOneBitSet(CI))
2343 return new SetCondInst(isSetNE ? Instruction::SetEQ :
2344 Instruction::SetNE, Op0,
2345 Constant::getNullValue(CI->getType()));
2347 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
2348 // to be a signed value as appropriate.
2349 if (isSignBit(BOC)) {
2350 Value *X = BO->getOperand(0);
2351 // If 'X' is not signed, insert a cast now...
2352 if (!BOC->getType()->isSigned()) {
2353 const Type *DestTy = BOC->getType()->getSignedVersion();
2354 X = InsertCastBefore(X, DestTy, I);
2356 return new SetCondInst(isSetNE ? Instruction::SetLT :
2357 Instruction::SetGE, X,
2358 Constant::getNullValue(X->getType()));
2361 // ((X & ~7) == 0) --> X < 8
2362 if (CI->isNullValue() && isHighOnes(BOC)) {
2363 Value *X = BO->getOperand(0);
2364 Constant *NegX = ConstantExpr::getNeg(BOC);
2366 // If 'X' is signed, insert a cast now.
2367 if (NegX->getType()->isSigned()) {
2368 const Type *DestTy = NegX->getType()->getUnsignedVersion();
2369 X = InsertCastBefore(X, DestTy, I);
2370 NegX = ConstantExpr::getCast(NegX, DestTy);
2373 return new SetCondInst(isSetNE ? Instruction::SetGE :
2374 Instruction::SetLT, X, NegX);
2381 } else { // Not a SetEQ/SetNE
2382 // If the LHS is a cast from an integral value of the same size,
2383 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
2384 Value *CastOp = Cast->getOperand(0);
2385 const Type *SrcTy = CastOp->getType();
2386 unsigned SrcTySize = SrcTy->getPrimitiveSize();
2387 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
2388 SrcTySize == Cast->getType()->getPrimitiveSize()) {
2389 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
2390 "Source and destination signednesses should differ!");
2391 if (Cast->getType()->isSigned()) {
2392 // If this is a signed comparison, check for comparisons in the
2393 // vicinity of zero.
2394 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
2396 return BinaryOperator::createSetGT(CastOp,
2397 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
2398 else if (I.getOpcode() == Instruction::SetGT &&
2399 cast<ConstantSInt>(CI)->getValue() == -1)
2400 // X > -1 => x < 128
2401 return BinaryOperator::createSetLT(CastOp,
2402 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
2404 ConstantUInt *CUI = cast<ConstantUInt>(CI);
2405 if (I.getOpcode() == Instruction::SetLT &&
2406 CUI->getValue() == 1ULL << (SrcTySize*8-1))
2407 // X < 128 => X > -1
2408 return BinaryOperator::createSetGT(CastOp,
2409 ConstantSInt::get(SrcTy, -1));
2410 else if (I.getOpcode() == Instruction::SetGT &&
2411 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
2413 return BinaryOperator::createSetLT(CastOp,
2414 Constant::getNullValue(SrcTy));
2421 // Test to see if the operands of the setcc are casted versions of other
2422 // values. If the cast can be stripped off both arguments, we do so now.
2423 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
2424 Value *CastOp0 = CI->getOperand(0);
2425 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
2426 (isa<Constant>(Op1) || isa<CastInst>(Op1)) &&
2427 (I.getOpcode() == Instruction::SetEQ ||
2428 I.getOpcode() == Instruction::SetNE)) {
2429 // We keep moving the cast from the left operand over to the right
2430 // operand, where it can often be eliminated completely.
2433 // If operand #1 is a cast instruction, see if we can eliminate it as
2435 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
2436 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
2438 Op1 = CI2->getOperand(0);
2440 // If Op1 is a constant, we can fold the cast into the constant.
2441 if (Op1->getType() != Op0->getType())
2442 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
2443 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
2445 // Otherwise, cast the RHS right before the setcc
2446 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
2447 InsertNewInstBefore(cast<Instruction>(Op1), I);
2449 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
2452 // Handle the special case of: setcc (cast bool to X), <cst>
2453 // This comes up when you have code like
2456 // For generality, we handle any zero-extension of any operand comparison
2458 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
2459 const Type *SrcTy = CastOp0->getType();
2460 const Type *DestTy = Op0->getType();
2461 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
2462 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
2463 // Ok, we have an expansion of operand 0 into a new type. Get the
2464 // constant value, masink off bits which are not set in the RHS. These
2465 // could be set if the destination value is signed.
2466 uint64_t ConstVal = ConstantRHS->getRawValue();
2467 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
2469 // If the constant we are comparing it with has high bits set, which
2470 // don't exist in the original value, the values could never be equal,
2471 // because the source would be zero extended.
2473 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
2474 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
2475 if (ConstVal & ~((1ULL << SrcBits)-1)) {
2476 switch (I.getOpcode()) {
2477 default: assert(0 && "Unknown comparison type!");
2478 case Instruction::SetEQ:
2479 return ReplaceInstUsesWith(I, ConstantBool::False);
2480 case Instruction::SetNE:
2481 return ReplaceInstUsesWith(I, ConstantBool::True);
2482 case Instruction::SetLT:
2483 case Instruction::SetLE:
2484 if (DestTy->isSigned() && HasSignBit)
2485 return ReplaceInstUsesWith(I, ConstantBool::False);
2486 return ReplaceInstUsesWith(I, ConstantBool::True);
2487 case Instruction::SetGT:
2488 case Instruction::SetGE:
2489 if (DestTy->isSigned() && HasSignBit)
2490 return ReplaceInstUsesWith(I, ConstantBool::True);
2491 return ReplaceInstUsesWith(I, ConstantBool::False);
2495 // Otherwise, we can replace the setcc with a setcc of the smaller
2497 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
2498 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
2502 return Changed ? &I : 0;
2505 // visitSetCondInstWithCastAndConstant - this method is part of the
2506 // visitSetCondInst method. It handles the situation where we have:
2507 // (setcc (cast X to larger), CI)
2508 // It tries to remove the cast and even the setcc if the CI value
2509 // and range of the cast allow it.
2511 InstCombiner::visitSetCondInstWithCastAndConstant(BinaryOperator&I,
2514 const Type *SrcTy = LHSI->getOperand(0)->getType();
2515 const Type *DestTy = LHSI->getType();
2516 if (SrcTy->isIntegral() && DestTy->isIntegral()) {
2517 unsigned SrcBits = SrcTy->getPrimitiveSize()*8;
2518 unsigned DestBits = DestTy->getPrimitiveSize()*8;
2519 if (SrcTy == Type::BoolTy)
2521 if (DestTy == Type::BoolTy)
2523 if (SrcBits < DestBits) {
2524 // There are fewer bits in the source of the cast than in the result
2525 // of the cast. Any other case doesn't matter because the constant
2526 // value won't have changed due to sign extension.
2527 Constant *NewCst = ConstantExpr::getCast(CI, SrcTy);
2528 if (ConstantExpr::getCast(NewCst, DestTy) == CI) {
2529 // The constant value operand of the setCC before and after a
2530 // cast to the source type of the cast instruction is the same
2531 // value, so we just replace with the same setcc opcode, but
2532 // using the source value compared to the constant casted to the
2534 if (SrcTy->isSigned() && DestTy->isUnsigned()) {
2535 CastInst* Cst = new CastInst(LHSI->getOperand(0),
2536 SrcTy->getUnsignedVersion(), LHSI->getName());
2537 InsertNewInstBefore(Cst,I);
2538 return new SetCondInst(I.getOpcode(), Cst,
2539 ConstantExpr::getCast(CI, SrcTy->getUnsignedVersion()));
2541 return new SetCondInst(I.getOpcode(), LHSI->getOperand(0),NewCst);
2543 // The constant value before and after a cast to the source type
2544 // is different, so various cases are possible depending on the
2545 // opcode and the signs of the types involved in the cast.
2546 switch (I.getOpcode()) {
2547 case Instruction::SetLT: {
2548 Constant* Max = ConstantIntegral::getMaxValue(SrcTy);
2549 Max = ConstantExpr::getCast(Max, DestTy);
2550 return ReplaceInstUsesWith(I, ConstantExpr::getSetLT(Max, CI));
2552 case Instruction::SetGT: {
2553 Constant* Min = ConstantIntegral::getMinValue(SrcTy);
2554 Min = ConstantExpr::getCast(Min, DestTy);
2555 return ReplaceInstUsesWith(I, ConstantExpr::getSetGT(Min, CI));
2557 case Instruction::SetEQ:
2558 // We're looking for equality, and we know the values are not
2559 // equal so replace with constant False.
2560 return ReplaceInstUsesWith(I, ConstantBool::False);
2561 case Instruction::SetNE:
2562 // We're testing for inequality, and we know the values are not
2563 // equal so replace with constant True.
2564 return ReplaceInstUsesWith(I, ConstantBool::True);
2565 case Instruction::SetLE:
2566 case Instruction::SetGE:
2567 assert(!"SetLE and SetGE should be handled elsewhere");
2569 assert(!"unknown integer comparison");
2577 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
2578 assert(I.getOperand(1)->getType() == Type::UByteTy);
2579 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2580 bool isLeftShift = I.getOpcode() == Instruction::Shl;
2582 // shl X, 0 == X and shr X, 0 == X
2583 // shl 0, X == 0 and shr 0, X == 0
2584 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
2585 Op0 == Constant::getNullValue(Op0->getType()))
2586 return ReplaceInstUsesWith(I, Op0);
2588 if (isa<UndefValue>(Op0)) { // undef >>s X -> undef
2589 if (!isLeftShift && I.getType()->isSigned())
2590 return ReplaceInstUsesWith(I, Op0);
2591 else // undef << X -> 0 AND undef >>u X -> 0
2592 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2594 if (isa<UndefValue>(Op1)) {
2595 if (isLeftShift || I.getType()->isUnsigned())
2596 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2598 return ReplaceInstUsesWith(I, Op0); // X >>s undef -> X
2601 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
2603 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
2604 if (CSI->isAllOnesValue())
2605 return ReplaceInstUsesWith(I, CSI);
2607 // Try to fold constant and into select arguments.
2608 if (isa<Constant>(Op0))
2609 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
2610 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
2613 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
2614 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
2615 // of a signed value.
2617 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
2618 if (CUI->getValue() >= TypeBits) {
2619 if (!Op0->getType()->isSigned() || isLeftShift)
2620 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
2622 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
2627 // ((X*C1) << C2) == (X * (C1 << C2))
2628 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
2629 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
2630 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
2631 return BinaryOperator::createMul(BO->getOperand(0),
2632 ConstantExpr::getShl(BOOp, CUI));
2634 // Try to fold constant and into select arguments.
2635 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
2636 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
2638 if (isa<PHINode>(Op0))
2639 if (Instruction *NV = FoldOpIntoPhi(I))
2642 // If the operand is an bitwise operator with a constant RHS, and the
2643 // shift is the only use, we can pull it out of the shift.
2644 if (Op0->hasOneUse())
2645 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
2646 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
2647 bool isValid = true; // Valid only for And, Or, Xor
2648 bool highBitSet = false; // Transform if high bit of constant set?
2650 switch (Op0BO->getOpcode()) {
2651 default: isValid = false; break; // Do not perform transform!
2652 case Instruction::Add:
2653 isValid = isLeftShift;
2655 case Instruction::Or:
2656 case Instruction::Xor:
2659 case Instruction::And:
2664 // If this is a signed shift right, and the high bit is modified
2665 // by the logical operation, do not perform the transformation.
2666 // The highBitSet boolean indicates the value of the high bit of
2667 // the constant which would cause it to be modified for this
2670 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
2671 uint64_t Val = Op0C->getRawValue();
2672 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
2676 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
2678 Instruction *NewShift =
2679 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
2682 InsertNewInstBefore(NewShift, I);
2684 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
2689 // If this is a shift of a shift, see if we can fold the two together...
2690 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
2691 if (ConstantUInt *ShiftAmt1C =
2692 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
2693 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
2694 unsigned ShiftAmt2 = CUI->getValue();
2696 // Check for (A << c1) << c2 and (A >> c1) >> c2
2697 if (I.getOpcode() == Op0SI->getOpcode()) {
2698 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
2699 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
2700 Amt = Op0->getType()->getPrimitiveSize()*8;
2701 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
2702 ConstantUInt::get(Type::UByteTy, Amt));
2705 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
2706 // signed types, we can only support the (A >> c1) << c2 configuration,
2707 // because it can not turn an arbitrary bit of A into a sign bit.
2708 if (I.getType()->isUnsigned() || isLeftShift) {
2709 // Calculate bitmask for what gets shifted off the edge...
2710 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
2712 C = ConstantExpr::getShl(C, ShiftAmt1C);
2714 C = ConstantExpr::getShr(C, ShiftAmt1C);
2717 BinaryOperator::createAnd(Op0SI->getOperand(0), C,
2718 Op0SI->getOperand(0)->getName()+".mask");
2719 InsertNewInstBefore(Mask, I);
2721 // Figure out what flavor of shift we should use...
2722 if (ShiftAmt1 == ShiftAmt2)
2723 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
2724 else if (ShiftAmt1 < ShiftAmt2) {
2725 return new ShiftInst(I.getOpcode(), Mask,
2726 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
2728 return new ShiftInst(Op0SI->getOpcode(), Mask,
2729 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
2745 /// getCastType - In the future, we will split the cast instruction into these
2746 /// various types. Until then, we have to do the analysis here.
2747 static CastType getCastType(const Type *Src, const Type *Dest) {
2748 assert(Src->isIntegral() && Dest->isIntegral() &&
2749 "Only works on integral types!");
2750 unsigned SrcSize = Src->getPrimitiveSize()*8;
2751 if (Src == Type::BoolTy) SrcSize = 1;
2752 unsigned DestSize = Dest->getPrimitiveSize()*8;
2753 if (Dest == Type::BoolTy) DestSize = 1;
2755 if (SrcSize == DestSize) return Noop;
2756 if (SrcSize > DestSize) return Truncate;
2757 if (Src->isSigned()) return Signext;
2762 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
2765 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
2766 const Type *DstTy, TargetData *TD) {
2768 // It is legal to eliminate the instruction if casting A->B->A if the sizes
2769 // are identical and the bits don't get reinterpreted (for example
2770 // int->float->int would not be allowed).
2771 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
2774 // If we are casting between pointer and integer types, treat pointers as
2775 // integers of the appropriate size for the code below.
2776 if (isa<PointerType>(SrcTy)) SrcTy = TD->getIntPtrType();
2777 if (isa<PointerType>(MidTy)) MidTy = TD->getIntPtrType();
2778 if (isa<PointerType>(DstTy)) DstTy = TD->getIntPtrType();
2780 // Allow free casting and conversion of sizes as long as the sign doesn't
2782 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
2783 CastType FirstCast = getCastType(SrcTy, MidTy);
2784 CastType SecondCast = getCastType(MidTy, DstTy);
2786 // Capture the effect of these two casts. If the result is a legal cast,
2787 // the CastType is stored here, otherwise a special code is used.
2788 static const unsigned CastResult[] = {
2789 // First cast is noop
2791 // First cast is a truncate
2792 1, 1, 4, 4, // trunc->extend is not safe to eliminate
2793 // First cast is a sign ext
2794 2, 5, 2, 4, // signext->zeroext never ok
2795 // First cast is a zero ext
2799 unsigned Result = CastResult[FirstCast*4+SecondCast];
2801 default: assert(0 && "Illegal table value!");
2806 // FIXME: in the future, when LLVM has explicit sign/zeroextends and
2807 // truncates, we could eliminate more casts.
2808 return (unsigned)getCastType(SrcTy, DstTy) == Result;
2810 return false; // Not possible to eliminate this here.
2812 // Sign or zero extend followed by truncate is always ok if the result
2813 // is a truncate or noop.
2814 CastType ResultCast = getCastType(SrcTy, DstTy);
2815 if (ResultCast == Noop || ResultCast == Truncate)
2817 // Otherwise we are still growing the value, we are only safe if the
2818 // result will match the sign/zeroextendness of the result.
2819 return ResultCast == FirstCast;
2825 static bool ValueRequiresCast(const Value *V, const Type *Ty, TargetData *TD) {
2826 if (V->getType() == Ty || isa<Constant>(V)) return false;
2827 if (const CastInst *CI = dyn_cast<CastInst>(V))
2828 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty,
2834 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
2835 /// InsertBefore instruction. This is specialized a bit to avoid inserting
2836 /// casts that are known to not do anything...
2838 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
2839 Instruction *InsertBefore) {
2840 if (V->getType() == DestTy) return V;
2841 if (Constant *C = dyn_cast<Constant>(V))
2842 return ConstantExpr::getCast(C, DestTy);
2844 CastInst *CI = new CastInst(V, DestTy, V->getName());
2845 InsertNewInstBefore(CI, *InsertBefore);
2849 // CastInst simplification
2851 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
2852 Value *Src = CI.getOperand(0);
2854 // If the user is casting a value to the same type, eliminate this cast
2856 if (CI.getType() == Src->getType())
2857 return ReplaceInstUsesWith(CI, Src);
2859 if (isa<UndefValue>(Src)) // cast undef -> undef
2860 return ReplaceInstUsesWith(CI, UndefValue::get(CI.getType()));
2862 // If casting the result of another cast instruction, try to eliminate this
2865 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
2866 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
2867 CSrc->getType(), CI.getType(), TD)) {
2868 // This instruction now refers directly to the cast's src operand. This
2869 // has a good chance of making CSrc dead.
2870 CI.setOperand(0, CSrc->getOperand(0));
2874 // If this is an A->B->A cast, and we are dealing with integral types, try
2875 // to convert this into a logical 'and' instruction.
2877 if (CSrc->getOperand(0)->getType() == CI.getType() &&
2878 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
2879 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
2880 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
2881 assert(CSrc->getType() != Type::ULongTy &&
2882 "Cannot have type bigger than ulong!");
2883 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
2884 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
2885 return BinaryOperator::createAnd(CSrc->getOperand(0), AndOp);
2889 // If this is a cast to bool, turn it into the appropriate setne instruction.
2890 if (CI.getType() == Type::BoolTy)
2891 return BinaryOperator::createSetNE(CI.getOperand(0),
2892 Constant::getNullValue(CI.getOperand(0)->getType()));
2894 // If casting the result of a getelementptr instruction with no offset, turn
2895 // this into a cast of the original pointer!
2897 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
2898 bool AllZeroOperands = true;
2899 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
2900 if (!isa<Constant>(GEP->getOperand(i)) ||
2901 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
2902 AllZeroOperands = false;
2905 if (AllZeroOperands) {
2906 CI.setOperand(0, GEP->getOperand(0));
2911 // If we are casting a malloc or alloca to a pointer to a type of the same
2912 // size, rewrite the allocation instruction to allocate the "right" type.
2914 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
2915 if (AI->hasOneUse() && !AI->isArrayAllocation())
2916 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
2917 // Get the type really allocated and the type casted to...
2918 const Type *AllocElTy = AI->getAllocatedType();
2919 const Type *CastElTy = PTy->getElementType();
2920 if (AllocElTy->isSized() && CastElTy->isSized()) {
2921 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
2922 unsigned CastElTySize = TD->getTypeSize(CastElTy);
2924 // If the allocation is for an even multiple of the cast type size
2925 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
2926 Value *Amt = ConstantUInt::get(Type::UIntTy,
2927 AllocElTySize/CastElTySize);
2928 std::string Name = AI->getName(); AI->setName("");
2929 AllocationInst *New;
2930 if (isa<MallocInst>(AI))
2931 New = new MallocInst(CastElTy, Amt, Name);
2933 New = new AllocaInst(CastElTy, Amt, Name);
2934 InsertNewInstBefore(New, *AI);
2935 return ReplaceInstUsesWith(CI, New);
2940 if (isa<PHINode>(Src))
2941 if (Instruction *NV = FoldOpIntoPhi(CI))
2944 // If the source value is an instruction with only this use, we can attempt to
2945 // propagate the cast into the instruction. Also, only handle integral types
2947 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
2948 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
2949 CI.getType()->isInteger()) { // Don't mess with casts to bool here
2950 const Type *DestTy = CI.getType();
2951 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
2952 unsigned DestBitSize = getTypeSizeInBits(DestTy);
2954 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
2955 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
2957 switch (SrcI->getOpcode()) {
2958 case Instruction::Add:
2959 case Instruction::Mul:
2960 case Instruction::And:
2961 case Instruction::Or:
2962 case Instruction::Xor:
2963 // If we are discarding information, or just changing the sign, rewrite.
2964 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
2965 // Don't insert two casts if they cannot be eliminated. We allow two
2966 // casts to be inserted if the sizes are the same. This could only be
2967 // converting signedness, which is a noop.
2968 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy,TD) ||
2969 !ValueRequiresCast(Op0, DestTy, TD)) {
2970 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2971 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
2972 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
2973 ->getOpcode(), Op0c, Op1c);
2977 case Instruction::Shl:
2978 // Allow changing the sign of the source operand. Do not allow changing
2979 // the size of the shift, UNLESS the shift amount is a constant. We
2980 // mush not change variable sized shifts to a smaller size, because it
2981 // is undefined to shift more bits out than exist in the value.
2982 if (DestBitSize == SrcBitSize ||
2983 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
2984 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2985 return new ShiftInst(Instruction::Shl, Op0c, Op1);
2994 /// GetSelectFoldableOperands - We want to turn code that looks like this:
2996 /// %D = select %cond, %C, %A
2998 /// %C = select %cond, %B, 0
3001 /// Assuming that the specified instruction is an operand to the select, return
3002 /// a bitmask indicating which operands of this instruction are foldable if they
3003 /// equal the other incoming value of the select.
3005 static unsigned GetSelectFoldableOperands(Instruction *I) {
3006 switch (I->getOpcode()) {
3007 case Instruction::Add:
3008 case Instruction::Mul:
3009 case Instruction::And:
3010 case Instruction::Or:
3011 case Instruction::Xor:
3012 return 3; // Can fold through either operand.
3013 case Instruction::Sub: // Can only fold on the amount subtracted.
3014 case Instruction::Shl: // Can only fold on the shift amount.
3015 case Instruction::Shr:
3018 return 0; // Cannot fold
3022 /// GetSelectFoldableConstant - For the same transformation as the previous
3023 /// function, return the identity constant that goes into the select.
3024 static Constant *GetSelectFoldableConstant(Instruction *I) {
3025 switch (I->getOpcode()) {
3026 default: assert(0 && "This cannot happen!"); abort();
3027 case Instruction::Add:
3028 case Instruction::Sub:
3029 case Instruction::Or:
3030 case Instruction::Xor:
3031 return Constant::getNullValue(I->getType());
3032 case Instruction::Shl:
3033 case Instruction::Shr:
3034 return Constant::getNullValue(Type::UByteTy);
3035 case Instruction::And:
3036 return ConstantInt::getAllOnesValue(I->getType());
3037 case Instruction::Mul:
3038 return ConstantInt::get(I->getType(), 1);
3042 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
3043 Value *CondVal = SI.getCondition();
3044 Value *TrueVal = SI.getTrueValue();
3045 Value *FalseVal = SI.getFalseValue();
3047 // select true, X, Y -> X
3048 // select false, X, Y -> Y
3049 if (ConstantBool *C = dyn_cast<ConstantBool>(CondVal))
3050 if (C == ConstantBool::True)
3051 return ReplaceInstUsesWith(SI, TrueVal);
3053 assert(C == ConstantBool::False);
3054 return ReplaceInstUsesWith(SI, FalseVal);
3057 // select C, X, X -> X
3058 if (TrueVal == FalseVal)
3059 return ReplaceInstUsesWith(SI, TrueVal);
3061 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
3062 return ReplaceInstUsesWith(SI, FalseVal);
3063 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
3064 return ReplaceInstUsesWith(SI, TrueVal);
3065 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
3066 if (isa<Constant>(TrueVal))
3067 return ReplaceInstUsesWith(SI, TrueVal);
3069 return ReplaceInstUsesWith(SI, FalseVal);
3072 if (SI.getType() == Type::BoolTy)
3073 if (ConstantBool *C = dyn_cast<ConstantBool>(TrueVal)) {
3074 if (C == ConstantBool::True) {
3075 // Change: A = select B, true, C --> A = or B, C
3076 return BinaryOperator::createOr(CondVal, FalseVal);
3078 // Change: A = select B, false, C --> A = and !B, C
3080 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
3081 "not."+CondVal->getName()), SI);
3082 return BinaryOperator::createAnd(NotCond, FalseVal);
3084 } else if (ConstantBool *C = dyn_cast<ConstantBool>(FalseVal)) {
3085 if (C == ConstantBool::False) {
3086 // Change: A = select B, C, false --> A = and B, C
3087 return BinaryOperator::createAnd(CondVal, TrueVal);
3089 // Change: A = select B, C, true --> A = or !B, C
3091 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
3092 "not."+CondVal->getName()), SI);
3093 return BinaryOperator::createOr(NotCond, TrueVal);
3097 // Selecting between two integer constants?
3098 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
3099 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
3100 // select C, 1, 0 -> cast C to int
3101 if (FalseValC->isNullValue() && TrueValC->getRawValue() == 1) {
3102 return new CastInst(CondVal, SI.getType());
3103 } else if (TrueValC->isNullValue() && FalseValC->getRawValue() == 1) {
3104 // select C, 0, 1 -> cast !C to int
3106 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
3107 "not."+CondVal->getName()), SI);
3108 return new CastInst(NotCond, SI.getType());
3111 // If one of the constants is zero (we know they can't both be) and we
3112 // have a setcc instruction with zero, and we have an 'and' with the
3113 // non-constant value, eliminate this whole mess. This corresponds to
3114 // cases like this: ((X & 27) ? 27 : 0)
3115 if (TrueValC->isNullValue() || FalseValC->isNullValue())
3116 if (Instruction *IC = dyn_cast<Instruction>(SI.getCondition()))
3117 if ((IC->getOpcode() == Instruction::SetEQ ||
3118 IC->getOpcode() == Instruction::SetNE) &&
3119 isa<ConstantInt>(IC->getOperand(1)) &&
3120 cast<Constant>(IC->getOperand(1))->isNullValue())
3121 if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
3122 if (ICA->getOpcode() == Instruction::And &&
3123 isa<ConstantInt>(ICA->getOperand(1)) &&
3124 (ICA->getOperand(1) == TrueValC ||
3125 ICA->getOperand(1) == FalseValC) &&
3126 isOneBitSet(cast<ConstantInt>(ICA->getOperand(1)))) {
3127 // Okay, now we know that everything is set up, we just don't
3128 // know whether we have a setne or seteq and whether the true or
3129 // false val is the zero.
3130 bool ShouldNotVal = !TrueValC->isNullValue();
3131 ShouldNotVal ^= IC->getOpcode() == Instruction::SetNE;
3134 V = InsertNewInstBefore(BinaryOperator::create(
3135 Instruction::Xor, V, ICA->getOperand(1)), SI);
3136 return ReplaceInstUsesWith(SI, V);
3140 // See if we are selecting two values based on a comparison of the two values.
3141 if (SetCondInst *SCI = dyn_cast<SetCondInst>(CondVal)) {
3142 if (SCI->getOperand(0) == TrueVal && SCI->getOperand(1) == FalseVal) {
3143 // Transform (X == Y) ? X : Y -> Y
3144 if (SCI->getOpcode() == Instruction::SetEQ)
3145 return ReplaceInstUsesWith(SI, FalseVal);
3146 // Transform (X != Y) ? X : Y -> X
3147 if (SCI->getOpcode() == Instruction::SetNE)
3148 return ReplaceInstUsesWith(SI, TrueVal);
3149 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
3151 } else if (SCI->getOperand(0) == FalseVal && SCI->getOperand(1) == TrueVal){
3152 // Transform (X == Y) ? Y : X -> X
3153 if (SCI->getOpcode() == Instruction::SetEQ)
3154 return ReplaceInstUsesWith(SI, FalseVal);
3155 // Transform (X != Y) ? Y : X -> Y
3156 if (SCI->getOpcode() == Instruction::SetNE)
3157 return ReplaceInstUsesWith(SI, TrueVal);
3158 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
3162 // See if we can fold the select into one of our operands.
3163 if (SI.getType()->isInteger()) {
3164 // See the comment above GetSelectFoldableOperands for a description of the
3165 // transformation we are doing here.
3166 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal))
3167 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
3168 !isa<Constant>(FalseVal))
3169 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
3170 unsigned OpToFold = 0;
3171 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
3173 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
3178 Constant *C = GetSelectFoldableConstant(TVI);
3179 std::string Name = TVI->getName(); TVI->setName("");
3180 Instruction *NewSel =
3181 new SelectInst(SI.getCondition(), TVI->getOperand(2-OpToFold), C,
3183 InsertNewInstBefore(NewSel, SI);
3184 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
3185 return BinaryOperator::create(BO->getOpcode(), FalseVal, NewSel);
3186 else if (ShiftInst *SI = dyn_cast<ShiftInst>(TVI))
3187 return new ShiftInst(SI->getOpcode(), FalseVal, NewSel);
3189 assert(0 && "Unknown instruction!!");
3194 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal))
3195 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
3196 !isa<Constant>(TrueVal))
3197 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
3198 unsigned OpToFold = 0;
3199 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
3201 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
3206 Constant *C = GetSelectFoldableConstant(FVI);
3207 std::string Name = FVI->getName(); FVI->setName("");
3208 Instruction *NewSel =
3209 new SelectInst(SI.getCondition(), C, FVI->getOperand(2-OpToFold),
3211 InsertNewInstBefore(NewSel, SI);
3212 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
3213 return BinaryOperator::create(BO->getOpcode(), TrueVal, NewSel);
3214 else if (ShiftInst *SI = dyn_cast<ShiftInst>(FVI))
3215 return new ShiftInst(SI->getOpcode(), TrueVal, NewSel);
3217 assert(0 && "Unknown instruction!!");
3226 // CallInst simplification
3228 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
3229 // Intrinsics cannot occur in an invoke, so handle them here instead of in
3231 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(&CI)) {
3232 bool Changed = false;
3234 // memmove/cpy/set of zero bytes is a noop.
3235 if (Constant *NumBytes = dyn_cast<Constant>(MI->getLength())) {
3236 if (NumBytes->isNullValue()) return EraseInstFromFunction(CI);
3238 // FIXME: Increase alignment here.
3240 if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes))
3241 if (CI->getRawValue() == 1) {
3242 // Replace the instruction with just byte operations. We would
3243 // transform other cases to loads/stores, but we don't know if
3244 // alignment is sufficient.
3248 // If we have a memmove and the source operation is a constant global,
3249 // then the source and dest pointers can't alias, so we can change this
3250 // into a call to memcpy.
3251 if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(MI))
3252 if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
3253 if (GVSrc->isConstant()) {
3254 Module *M = CI.getParent()->getParent()->getParent();
3255 Function *MemCpy = M->getOrInsertFunction("llvm.memcpy",
3256 CI.getCalledFunction()->getFunctionType());
3257 CI.setOperand(0, MemCpy);
3261 if (Changed) return &CI;
3262 } else if (DbgStopPointInst *SPI = dyn_cast<DbgStopPointInst>(&CI)) {
3263 // If this stoppoint is at the same source location as the previous
3264 // stoppoint in the chain, it is not needed.
3265 if (DbgStopPointInst *PrevSPI =
3266 dyn_cast<DbgStopPointInst>(SPI->getChain()))
3267 if (SPI->getLineNo() == PrevSPI->getLineNo() &&
3268 SPI->getColNo() == PrevSPI->getColNo()) {
3269 SPI->replaceAllUsesWith(PrevSPI);
3270 return EraseInstFromFunction(CI);
3274 return visitCallSite(&CI);
3277 // InvokeInst simplification
3279 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
3280 return visitCallSite(&II);
3283 // visitCallSite - Improvements for call and invoke instructions.
3285 Instruction *InstCombiner::visitCallSite(CallSite CS) {
3286 bool Changed = false;
3288 // If the callee is a constexpr cast of a function, attempt to move the cast
3289 // to the arguments of the call/invoke.
3290 if (transformConstExprCastCall(CS)) return 0;
3292 Value *Callee = CS.getCalledValue();
3294 if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
3295 // This instruction is not reachable, just remove it. We insert a store to
3296 // undef so that we know that this code is not reachable, despite the fact
3297 // that we can't modify the CFG here.
3298 new StoreInst(ConstantBool::True,
3299 UndefValue::get(PointerType::get(Type::BoolTy)),
3300 CS.getInstruction());
3302 if (!CS.getInstruction()->use_empty())
3303 CS.getInstruction()->
3304 replaceAllUsesWith(UndefValue::get(CS.getInstruction()->getType()));
3306 if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
3307 // Don't break the CFG, insert a dummy cond branch.
3308 new BranchInst(II->getNormalDest(), II->getUnwindDest(),
3309 ConstantBool::True, II);
3311 return EraseInstFromFunction(*CS.getInstruction());
3314 const PointerType *PTy = cast<PointerType>(Callee->getType());
3315 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
3316 if (FTy->isVarArg()) {
3317 // See if we can optimize any arguments passed through the varargs area of
3319 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
3320 E = CS.arg_end(); I != E; ++I)
3321 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
3322 // If this cast does not effect the value passed through the varargs
3323 // area, we can eliminate the use of the cast.
3324 Value *Op = CI->getOperand(0);
3325 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
3332 return Changed ? CS.getInstruction() : 0;
3335 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
3336 // attempt to move the cast to the arguments of the call/invoke.
3338 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
3339 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
3340 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
3341 if (CE->getOpcode() != Instruction::Cast || !isa<Function>(CE->getOperand(0)))
3343 Function *Callee = cast<Function>(CE->getOperand(0));
3344 Instruction *Caller = CS.getInstruction();
3346 // Okay, this is a cast from a function to a different type. Unless doing so
3347 // would cause a type conversion of one of our arguments, change this call to
3348 // be a direct call with arguments casted to the appropriate types.
3350 const FunctionType *FT = Callee->getFunctionType();
3351 const Type *OldRetTy = Caller->getType();
3353 // Check to see if we are changing the return type...
3354 if (OldRetTy != FT->getReturnType()) {
3355 if (Callee->isExternal() &&
3356 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
3357 !Caller->use_empty())
3358 return false; // Cannot transform this return value...
3360 // If the callsite is an invoke instruction, and the return value is used by
3361 // a PHI node in a successor, we cannot change the return type of the call
3362 // because there is no place to put the cast instruction (without breaking
3363 // the critical edge). Bail out in this case.
3364 if (!Caller->use_empty())
3365 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
3366 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
3368 if (PHINode *PN = dyn_cast<PHINode>(*UI))
3369 if (PN->getParent() == II->getNormalDest() ||
3370 PN->getParent() == II->getUnwindDest())
3374 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
3375 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
3377 CallSite::arg_iterator AI = CS.arg_begin();
3378 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
3379 const Type *ParamTy = FT->getParamType(i);
3380 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
3381 if (Callee->isExternal() && !isConvertible) return false;
3384 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
3385 Callee->isExternal())
3386 return false; // Do not delete arguments unless we have a function body...
3388 // Okay, we decided that this is a safe thing to do: go ahead and start
3389 // inserting cast instructions as necessary...
3390 std::vector<Value*> Args;
3391 Args.reserve(NumActualArgs);
3393 AI = CS.arg_begin();
3394 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
3395 const Type *ParamTy = FT->getParamType(i);
3396 if ((*AI)->getType() == ParamTy) {
3397 Args.push_back(*AI);
3399 Args.push_back(InsertNewInstBefore(new CastInst(*AI, ParamTy, "tmp"),
3404 // If the function takes more arguments than the call was taking, add them
3406 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
3407 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
3409 // If we are removing arguments to the function, emit an obnoxious warning...
3410 if (FT->getNumParams() < NumActualArgs)
3411 if (!FT->isVarArg()) {
3412 std::cerr << "WARNING: While resolving call to function '"
3413 << Callee->getName() << "' arguments were dropped!\n";
3415 // Add all of the arguments in their promoted form to the arg list...
3416 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
3417 const Type *PTy = getPromotedType((*AI)->getType());
3418 if (PTy != (*AI)->getType()) {
3419 // Must promote to pass through va_arg area!
3420 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
3421 InsertNewInstBefore(Cast, *Caller);
3422 Args.push_back(Cast);
3424 Args.push_back(*AI);
3429 if (FT->getReturnType() == Type::VoidTy)
3430 Caller->setName(""); // Void type should not have a name...
3433 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
3434 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
3435 Args, Caller->getName(), Caller);
3437 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
3440 // Insert a cast of the return type as necessary...
3442 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
3443 if (NV->getType() != Type::VoidTy) {
3444 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
3446 // If this is an invoke instruction, we should insert it after the first
3447 // non-phi, instruction in the normal successor block.
3448 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
3449 BasicBlock::iterator I = II->getNormalDest()->begin();
3450 while (isa<PHINode>(I)) ++I;
3451 InsertNewInstBefore(NC, *I);
3453 // Otherwise, it's a call, just insert cast right after the call instr
3454 InsertNewInstBefore(NC, *Caller);
3456 AddUsersToWorkList(*Caller);
3458 NV = UndefValue::get(Caller->getType());
3462 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
3463 Caller->replaceAllUsesWith(NV);
3464 Caller->getParent()->getInstList().erase(Caller);
3465 removeFromWorkList(Caller);
3470 // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
3471 // operator and they all are only used by the PHI, PHI together their
3472 // inputs, and do the operation once, to the result of the PHI.
3473 Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
3474 Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
3476 // Scan the instruction, looking for input operations that can be folded away.
3477 // If all input operands to the phi are the same instruction (e.g. a cast from
3478 // the same type or "+42") we can pull the operation through the PHI, reducing
3479 // code size and simplifying code.
3480 Constant *ConstantOp = 0;
3481 const Type *CastSrcTy = 0;
3482 if (isa<CastInst>(FirstInst)) {
3483 CastSrcTy = FirstInst->getOperand(0)->getType();
3484 } else if (isa<BinaryOperator>(FirstInst) || isa<ShiftInst>(FirstInst)) {
3485 // Can fold binop or shift if the RHS is a constant.
3486 ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1));
3487 if (ConstantOp == 0) return 0;
3489 return 0; // Cannot fold this operation.
3492 // Check to see if all arguments are the same operation.
3493 for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
3494 if (!isa<Instruction>(PN.getIncomingValue(i))) return 0;
3495 Instruction *I = cast<Instruction>(PN.getIncomingValue(i));
3496 if (!I->hasOneUse() || I->getOpcode() != FirstInst->getOpcode())
3499 if (I->getOperand(0)->getType() != CastSrcTy)
3500 return 0; // Cast operation must match.
3501 } else if (I->getOperand(1) != ConstantOp) {
3506 // Okay, they are all the same operation. Create a new PHI node of the
3507 // correct type, and PHI together all of the LHS's of the instructions.
3508 PHINode *NewPN = new PHINode(FirstInst->getOperand(0)->getType(),
3509 PN.getName()+".in");
3510 NewPN->op_reserve(PN.getNumOperands());
3512 Value *InVal = FirstInst->getOperand(0);
3513 NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
3515 // Add all operands to the new PHI.
3516 for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
3517 Value *NewInVal = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0);
3518 if (NewInVal != InVal)
3520 NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i));
3525 // The new PHI unions all of the same values together. This is really
3526 // common, so we handle it intelligently here for compile-time speed.
3530 InsertNewInstBefore(NewPN, PN);
3534 // Insert and return the new operation.
3535 if (isa<CastInst>(FirstInst))
3536 return new CastInst(PhiVal, PN.getType());
3537 else if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
3538 return BinaryOperator::create(BinOp->getOpcode(), PhiVal, ConstantOp);
3540 return new ShiftInst(cast<ShiftInst>(FirstInst)->getOpcode(),
3541 PhiVal, ConstantOp);
3544 // PHINode simplification
3546 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
3547 if (Value *V = hasConstantValue(&PN)) {
3548 // If V is an instruction, we have to be certain that it dominates PN.
3549 // However, because we don't have dom info, we can't do a perfect job.
3550 if (Instruction *I = dyn_cast<Instruction>(V)) {
3551 // We know that the instruction dominates the PHI if there are no undef
3552 // values coming in.
3553 if (I->getParent() != &I->getParent()->getParent()->front() ||
3555 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
3556 if (isa<UndefValue>(PN.getIncomingValue(i))) {
3563 return ReplaceInstUsesWith(PN, V);
3566 // If the only user of this instruction is a cast instruction, and all of the
3567 // incoming values are constants, change this PHI to merge together the casted
3570 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
3571 if (CI->getType() != PN.getType()) { // noop casts will be folded
3572 bool AllConstant = true;
3573 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
3574 if (!isa<Constant>(PN.getIncomingValue(i))) {
3575 AllConstant = false;
3579 // Make a new PHI with all casted values.
3580 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
3581 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
3582 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
3583 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
3584 PN.getIncomingBlock(i));
3587 // Update the cast instruction.
3588 CI->setOperand(0, New);
3589 WorkList.push_back(CI); // revisit the cast instruction to fold.
3590 WorkList.push_back(New); // Make sure to revisit the new Phi
3591 return &PN; // PN is now dead!
3595 // If all PHI operands are the same operation, pull them through the PHI,
3596 // reducing code size.
3597 if (isa<Instruction>(PN.getIncomingValue(0)) &&
3598 PN.getIncomingValue(0)->hasOneUse())
3599 if (Instruction *Result = FoldPHIArgOpIntoPHI(PN))
3606 static Value *InsertSignExtendToPtrTy(Value *V, const Type *DTy,
3607 Instruction *InsertPoint,
3609 unsigned PS = IC->getTargetData().getPointerSize();
3610 const Type *VTy = V->getType();
3611 if (!VTy->isSigned() && VTy->getPrimitiveSize() < PS)
3612 // We must insert a cast to ensure we sign-extend.
3613 V = IC->InsertNewInstBefore(new CastInst(V, VTy->getSignedVersion(),
3614 V->getName()), *InsertPoint);
3615 return IC->InsertNewInstBefore(new CastInst(V, DTy, V->getName()),
3620 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
3621 Value *PtrOp = GEP.getOperand(0);
3622 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
3623 // If so, eliminate the noop.
3624 if (GEP.getNumOperands() == 1)
3625 return ReplaceInstUsesWith(GEP, PtrOp);
3627 if (isa<UndefValue>(GEP.getOperand(0)))
3628 return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
3630 bool HasZeroPointerIndex = false;
3631 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
3632 HasZeroPointerIndex = C->isNullValue();
3634 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
3635 return ReplaceInstUsesWith(GEP, PtrOp);
3637 // Eliminate unneeded casts for indices.
3638 bool MadeChange = false;
3639 gep_type_iterator GTI = gep_type_begin(GEP);
3640 for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI)
3641 if (isa<SequentialType>(*GTI)) {
3642 if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
3643 Value *Src = CI->getOperand(0);
3644 const Type *SrcTy = Src->getType();
3645 const Type *DestTy = CI->getType();
3646 if (Src->getType()->isInteger()) {
3647 if (SrcTy->getPrimitiveSize() == DestTy->getPrimitiveSize()) {
3648 // We can always eliminate a cast from ulong or long to the other.
3649 // We can always eliminate a cast from uint to int or the other on
3650 // 32-bit pointer platforms.
3651 if (DestTy->getPrimitiveSize() >= TD->getPointerSize()) {
3653 GEP.setOperand(i, Src);
3655 } else if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
3656 SrcTy->getPrimitiveSize() == 4) {
3657 // We can always eliminate a cast from int to [u]long. We can
3658 // eliminate a cast from uint to [u]long iff the target is a 32-bit
3660 if (SrcTy->isSigned() ||
3661 SrcTy->getPrimitiveSize() >= TD->getPointerSize()) {
3663 GEP.setOperand(i, Src);
3668 // If we are using a wider index than needed for this platform, shrink it
3669 // to what we need. If the incoming value needs a cast instruction,
3670 // insert it. This explicit cast can make subsequent optimizations more
3672 Value *Op = GEP.getOperand(i);
3673 if (Op->getType()->getPrimitiveSize() > TD->getPointerSize())
3674 if (Constant *C = dyn_cast<Constant>(Op)) {
3675 GEP.setOperand(i, ConstantExpr::getCast(C,
3676 TD->getIntPtrType()->getSignedVersion()));
3679 Op = InsertNewInstBefore(new CastInst(Op, TD->getIntPtrType(),
3680 Op->getName()), GEP);
3681 GEP.setOperand(i, Op);
3685 // If this is a constant idx, make sure to canonicalize it to be a signed
3686 // operand, otherwise CSE and other optimizations are pessimized.
3687 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op)) {
3688 GEP.setOperand(i, ConstantExpr::getCast(CUI,
3689 CUI->getType()->getSignedVersion()));
3693 if (MadeChange) return &GEP;
3695 // Combine Indices - If the source pointer to this getelementptr instruction
3696 // is a getelementptr instruction, combine the indices of the two
3697 // getelementptr instructions into a single instruction.
3699 std::vector<Value*> SrcGEPOperands;
3700 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(PtrOp)) {
3701 SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
3702 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PtrOp)) {
3703 if (CE->getOpcode() == Instruction::GetElementPtr)
3704 SrcGEPOperands.assign(CE->op_begin(), CE->op_end());
3707 if (!SrcGEPOperands.empty()) {
3708 // Note that if our source is a gep chain itself that we wait for that
3709 // chain to be resolved before we perform this transformation. This
3710 // avoids us creating a TON of code in some cases.
3712 if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
3713 cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
3714 return 0; // Wait until our source is folded to completion.
3716 std::vector<Value *> Indices;
3718 // Find out whether the last index in the source GEP is a sequential idx.
3719 bool EndsWithSequential = false;
3720 for (gep_type_iterator I = gep_type_begin(*cast<User>(PtrOp)),
3721 E = gep_type_end(*cast<User>(PtrOp)); I != E; ++I)
3722 EndsWithSequential = !isa<StructType>(*I);
3724 // Can we combine the two pointer arithmetics offsets?
3725 if (EndsWithSequential) {
3726 // Replace: gep (gep %P, long B), long A, ...
3727 // With: T = long A+B; gep %P, T, ...
3729 Value *Sum, *SO1 = SrcGEPOperands.back(), *GO1 = GEP.getOperand(1);
3730 if (SO1 == Constant::getNullValue(SO1->getType())) {
3732 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
3735 // If they aren't the same type, convert both to an integer of the
3736 // target's pointer size.
3737 if (SO1->getType() != GO1->getType()) {
3738 if (Constant *SO1C = dyn_cast<Constant>(SO1)) {
3739 SO1 = ConstantExpr::getCast(SO1C, GO1->getType());
3740 } else if (Constant *GO1C = dyn_cast<Constant>(GO1)) {
3741 GO1 = ConstantExpr::getCast(GO1C, SO1->getType());
3743 unsigned PS = TD->getPointerSize();
3744 if (SO1->getType()->getPrimitiveSize() == PS) {
3745 // Convert GO1 to SO1's type.
3746 GO1 = InsertSignExtendToPtrTy(GO1, SO1->getType(), &GEP, this);
3748 } else if (GO1->getType()->getPrimitiveSize() == PS) {
3749 // Convert SO1 to GO1's type.
3750 SO1 = InsertSignExtendToPtrTy(SO1, GO1->getType(), &GEP, this);
3752 const Type *PT = TD->getIntPtrType();
3753 SO1 = InsertSignExtendToPtrTy(SO1, PT, &GEP, this);
3754 GO1 = InsertSignExtendToPtrTy(GO1, PT, &GEP, this);
3758 if (isa<Constant>(SO1) && isa<Constant>(GO1))
3759 Sum = ConstantExpr::getAdd(cast<Constant>(SO1), cast<Constant>(GO1));
3761 Sum = BinaryOperator::createAdd(SO1, GO1, PtrOp->getName()+".sum");
3762 InsertNewInstBefore(cast<Instruction>(Sum), GEP);
3766 // Recycle the GEP we already have if possible.
3767 if (SrcGEPOperands.size() == 2) {
3768 GEP.setOperand(0, SrcGEPOperands[0]);
3769 GEP.setOperand(1, Sum);
3772 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
3773 SrcGEPOperands.end()-1);
3774 Indices.push_back(Sum);
3775 Indices.insert(Indices.end(), GEP.op_begin()+2, GEP.op_end());
3777 } else if (isa<Constant>(*GEP.idx_begin()) &&
3778 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
3779 SrcGEPOperands.size() != 1) {
3780 // Otherwise we can do the fold if the first index of the GEP is a zero
3781 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
3782 SrcGEPOperands.end());
3783 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
3786 if (!Indices.empty())
3787 return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
3789 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(PtrOp)) {
3790 // GEP of global variable. If all of the indices for this GEP are
3791 // constants, we can promote this to a constexpr instead of an instruction.
3793 // Scan for nonconstants...
3794 std::vector<Constant*> Indices;
3795 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
3796 for (; I != E && isa<Constant>(*I); ++I)
3797 Indices.push_back(cast<Constant>(*I));
3799 if (I == E) { // If they are all constants...
3800 Constant *CE = ConstantExpr::getGetElementPtr(GV, Indices);
3802 // Replace all uses of the GEP with the new constexpr...
3803 return ReplaceInstUsesWith(GEP, CE);
3805 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PtrOp)) {
3806 if (CE->getOpcode() == Instruction::Cast) {
3807 if (HasZeroPointerIndex) {
3808 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
3809 // into : GEP [10 x ubyte]* X, long 0, ...
3811 // This occurs when the program declares an array extern like "int X[];"
3813 Constant *X = CE->getOperand(0);
3814 const PointerType *CPTy = cast<PointerType>(CE->getType());
3815 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
3816 if (const ArrayType *XATy =
3817 dyn_cast<ArrayType>(XTy->getElementType()))
3818 if (const ArrayType *CATy =
3819 dyn_cast<ArrayType>(CPTy->getElementType()))
3820 if (CATy->getElementType() == XATy->getElementType()) {
3821 // At this point, we know that the cast source type is a pointer
3822 // to an array of the same type as the destination pointer
3823 // array. Because the array type is never stepped over (there
3824 // is a leading zero) we can fold the cast into this GEP.
3825 GEP.setOperand(0, X);
3828 } else if (GEP.getNumOperands() == 2) {
3829 // Transform things like:
3830 // %t = getelementptr ubyte* cast ([2 x sbyte]* %str to ubyte*), uint %V
3831 // into: %t1 = getelementptr [2 x sbyte*]* %str, int 0, uint %V; cast
3832 Constant *X = CE->getOperand(0);
3833 const Type *SrcElTy = cast<PointerType>(X->getType())->getElementType();
3834 const Type *ResElTy =cast<PointerType>(CE->getType())->getElementType();
3835 if (isa<ArrayType>(SrcElTy) &&
3836 TD->getTypeSize(cast<ArrayType>(SrcElTy)->getElementType()) ==
3837 TD->getTypeSize(ResElTy)) {
3838 Value *V = InsertNewInstBefore(
3839 new GetElementPtrInst(X, Constant::getNullValue(Type::IntTy),
3840 GEP.getOperand(1), GEP.getName()), GEP);
3841 return new CastInst(V, GEP.getType());
3850 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
3851 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
3852 if (AI.isArrayAllocation()) // Check C != 1
3853 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
3854 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
3855 AllocationInst *New = 0;
3857 // Create and insert the replacement instruction...
3858 if (isa<MallocInst>(AI))
3859 New = new MallocInst(NewTy, 0, AI.getName());
3861 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
3862 New = new AllocaInst(NewTy, 0, AI.getName());
3865 InsertNewInstBefore(New, AI);
3867 // Scan to the end of the allocation instructions, to skip over a block of
3868 // allocas if possible...
3870 BasicBlock::iterator It = New;
3871 while (isa<AllocationInst>(*It)) ++It;
3873 // Now that I is pointing to the first non-allocation-inst in the block,
3874 // insert our getelementptr instruction...
3876 std::vector<Value*> Idx(2, Constant::getNullValue(Type::IntTy));
3877 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
3879 // Now make everything use the getelementptr instead of the original
3881 return ReplaceInstUsesWith(AI, V);
3882 } else if (isa<UndefValue>(AI.getArraySize())) {
3883 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
3886 // If alloca'ing a zero byte object, replace the alloca with a null pointer.
3887 // Note that we only do this for alloca's, because malloc should allocate and
3888 // return a unique pointer, even for a zero byte allocation.
3889 if (isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized() &&
3890 TD->getTypeSize(AI.getAllocatedType()) == 0)
3891 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
3896 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
3897 Value *Op = FI.getOperand(0);
3899 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
3900 if (CastInst *CI = dyn_cast<CastInst>(Op))
3901 if (isa<PointerType>(CI->getOperand(0)->getType())) {
3902 FI.setOperand(0, CI->getOperand(0));
3906 // free undef -> unreachable.
3907 if (isa<UndefValue>(Op)) {
3908 // Insert a new store to null because we cannot modify the CFG here.
3909 new StoreInst(ConstantBool::True,
3910 UndefValue::get(PointerType::get(Type::BoolTy)), &FI);
3911 return EraseInstFromFunction(FI);
3914 // If we have 'free null' delete the instruction. This can happen in stl code
3915 // when lots of inlining happens.
3916 if (isa<ConstantPointerNull>(Op))
3917 return EraseInstFromFunction(FI);
3923 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
3924 /// constantexpr, return the constant value being addressed by the constant
3925 /// expression, or null if something is funny.
3927 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
3928 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
3929 return 0; // Do not allow stepping over the value!
3931 // Loop over all of the operands, tracking down which value we are
3933 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
3934 for (++I; I != E; ++I)
3935 if (const StructType *STy = dyn_cast<StructType>(*I)) {
3936 ConstantUInt *CU = cast<ConstantUInt>(I.getOperand());
3937 assert(CU->getValue() < STy->getNumElements() &&
3938 "Struct index out of range!");
3939 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
3940 C = CS->getOperand(CU->getValue());
3941 } else if (isa<ConstantAggregateZero>(C)) {
3942 C = Constant::getNullValue(STy->getElementType(CU->getValue()));
3943 } else if (isa<UndefValue>(C)) {
3944 C = UndefValue::get(STy->getElementType(CU->getValue()));
3948 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
3949 const ArrayType *ATy = cast<ArrayType>(*I);
3950 if ((uint64_t)CI->getRawValue() >= ATy->getNumElements()) return 0;
3951 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
3952 C = CA->getOperand(CI->getRawValue());
3953 else if (isa<ConstantAggregateZero>(C))
3954 C = Constant::getNullValue(ATy->getElementType());
3955 else if (isa<UndefValue>(C))
3956 C = UndefValue::get(ATy->getElementType());
3965 static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI) {
3966 User *CI = cast<User>(LI.getOperand(0));
3968 const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
3969 if (const PointerType *SrcTy =
3970 dyn_cast<PointerType>(CI->getOperand(0)->getType())) {
3971 const Type *SrcPTy = SrcTy->getElementType();
3972 if (SrcPTy->isSized() && DestPTy->isSized() &&
3973 IC.getTargetData().getTypeSize(SrcPTy) ==
3974 IC.getTargetData().getTypeSize(DestPTy) &&
3975 (SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
3976 (DestPTy->isInteger() || isa<PointerType>(DestPTy))) {
3977 // Okay, we are casting from one integer or pointer type to another of
3978 // the same size. Instead of casting the pointer before the load, cast
3979 // the result of the loaded value.
3980 Value *NewLoad = IC.InsertNewInstBefore(new LoadInst(CI->getOperand(0),
3982 LI.isVolatile()),LI);
3983 // Now cast the result of the load.
3984 return new CastInst(NewLoad, LI.getType());
3990 /// isSafeToLoadUnconditionally - Return true if we know that executing a load
3991 /// from this value cannot trap. If it is not obviously safe to load from the
3992 /// specified pointer, we do a quick local scan of the basic block containing
3993 /// ScanFrom, to determine if the address is already accessed.
3994 static bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
3995 // If it is an alloca or global variable, it is always safe to load from.
3996 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
3998 // Otherwise, be a little bit agressive by scanning the local block where we
3999 // want to check to see if the pointer is already being loaded or stored
4000 // from/to. If so, the previous load or store would have already trapped,
4001 // so there is no harm doing an extra load (also, CSE will later eliminate
4002 // the load entirely).
4003 BasicBlock::iterator BBI = ScanFrom, E = ScanFrom->getParent()->begin();
4008 if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
4009 if (LI->getOperand(0) == V) return true;
4010 } else if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
4011 if (SI->getOperand(1) == V) return true;
4017 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
4018 Value *Op = LI.getOperand(0);
4020 if (Constant *C = dyn_cast<Constant>(Op)) {
4021 if ((C->isNullValue() || isa<UndefValue>(C)) &&
4022 !LI.isVolatile()) { // load null/undef -> undef
4023 // Insert a new store to null instruction before the load to indicate that
4024 // this code is not reachable. We do this instead of inserting an
4025 // unreachable instruction directly because we cannot modify the CFG.
4026 new StoreInst(UndefValue::get(LI.getType()), C, &LI);
4027 return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
4030 // Instcombine load (constant global) into the value loaded.
4031 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
4032 if (GV->isConstant() && !GV->isExternal())
4033 return ReplaceInstUsesWith(LI, GV->getInitializer());
4035 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded.
4036 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
4037 if (CE->getOpcode() == Instruction::GetElementPtr) {
4038 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
4039 if (GV->isConstant() && !GV->isExternal())
4040 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
4041 return ReplaceInstUsesWith(LI, V);
4042 } else if (CE->getOpcode() == Instruction::Cast) {
4043 if (Instruction *Res = InstCombineLoadCast(*this, LI))
4048 // load (cast X) --> cast (load X) iff safe
4049 if (CastInst *CI = dyn_cast<CastInst>(Op))
4050 if (Instruction *Res = InstCombineLoadCast(*this, LI))
4053 if (!LI.isVolatile() && Op->hasOneUse()) {
4054 // Change select and PHI nodes to select values instead of addresses: this
4055 // helps alias analysis out a lot, allows many others simplifications, and
4056 // exposes redundancy in the code.
4058 // Note that we cannot do the transformation unless we know that the
4059 // introduced loads cannot trap! Something like this is valid as long as
4060 // the condition is always false: load (select bool %C, int* null, int* %G),
4061 // but it would not be valid if we transformed it to load from null
4064 if (SelectInst *SI = dyn_cast<SelectInst>(Op)) {
4065 // load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2).
4066 if (isSafeToLoadUnconditionally(SI->getOperand(1), SI) &&
4067 isSafeToLoadUnconditionally(SI->getOperand(2), SI)) {
4068 Value *V1 = InsertNewInstBefore(new LoadInst(SI->getOperand(1),
4069 SI->getOperand(1)->getName()+".val"), LI);
4070 Value *V2 = InsertNewInstBefore(new LoadInst(SI->getOperand(2),
4071 SI->getOperand(2)->getName()+".val"), LI);
4072 return new SelectInst(SI->getCondition(), V1, V2);
4075 // load (select (cond, null, P)) -> load P
4076 if (Constant *C = dyn_cast<Constant>(SI->getOperand(1)))
4077 if (C->isNullValue()) {
4078 LI.setOperand(0, SI->getOperand(2));
4082 // load (select (cond, P, null)) -> load P
4083 if (Constant *C = dyn_cast<Constant>(SI->getOperand(2)))
4084 if (C->isNullValue()) {
4085 LI.setOperand(0, SI->getOperand(1));
4089 } else if (PHINode *PN = dyn_cast<PHINode>(Op)) {
4090 // load (phi (&V1, &V2, &V3)) --> phi(load &V1, load &V2, load &V3)
4091 bool Safe = PN->getParent() == LI.getParent();
4093 // Scan all of the instructions between the PHI and the load to make
4094 // sure there are no instructions that might possibly alter the value
4095 // loaded from the PHI.
4097 BasicBlock::iterator I = &LI;
4098 for (--I; !isa<PHINode>(I); --I)
4099 if (isa<StoreInst>(I) || isa<CallInst>(I)) {
4105 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e && Safe; ++i)
4106 if (!isSafeToLoadUnconditionally(PN->getIncomingValue(i),
4107 PN->getIncomingBlock(i)->getTerminator()))
4112 PHINode *NewPN = new PHINode(LI.getType(), PN->getName());
4113 InsertNewInstBefore(NewPN, *PN);
4114 std::map<BasicBlock*,Value*> LoadMap; // Don't insert duplicate loads
4116 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
4117 BasicBlock *BB = PN->getIncomingBlock(i);
4118 Value *&TheLoad = LoadMap[BB];
4120 Value *InVal = PN->getIncomingValue(i);
4121 TheLoad = InsertNewInstBefore(new LoadInst(InVal,
4122 InVal->getName()+".val"),
4123 *BB->getTerminator());
4125 NewPN->addIncoming(TheLoad, BB);
4127 return ReplaceInstUsesWith(LI, NewPN);
4134 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
4135 // Change br (not X), label True, label False to: br X, label False, True
4137 BasicBlock *TrueDest;
4138 BasicBlock *FalseDest;
4139 if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) &&
4140 !isa<Constant>(X)) {
4141 // Swap Destinations and condition...
4143 BI.setSuccessor(0, FalseDest);
4144 BI.setSuccessor(1, TrueDest);
4148 // Cannonicalize setne -> seteq
4149 Instruction::BinaryOps Op; Value *Y;
4150 if (match(&BI, m_Br(m_SetCond(Op, m_Value(X), m_Value(Y)),
4151 TrueDest, FalseDest)))
4152 if ((Op == Instruction::SetNE || Op == Instruction::SetLE ||
4153 Op == Instruction::SetGE) && BI.getCondition()->hasOneUse()) {
4154 SetCondInst *I = cast<SetCondInst>(BI.getCondition());
4155 std::string Name = I->getName(); I->setName("");
4156 Instruction::BinaryOps NewOpcode = SetCondInst::getInverseCondition(Op);
4157 Value *NewSCC = BinaryOperator::create(NewOpcode, X, Y, Name, I);
4158 // Swap Destinations and condition...
4159 BI.setCondition(NewSCC);
4160 BI.setSuccessor(0, FalseDest);
4161 BI.setSuccessor(1, TrueDest);
4162 removeFromWorkList(I);
4163 I->getParent()->getInstList().erase(I);
4164 WorkList.push_back(cast<Instruction>(NewSCC));
4171 Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
4172 Value *Cond = SI.getCondition();
4173 if (Instruction *I = dyn_cast<Instruction>(Cond)) {
4174 if (I->getOpcode() == Instruction::Add)
4175 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
4176 // change 'switch (X+4) case 1:' into 'switch (X) case -3'
4177 for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2)
4178 SI.setOperand(i,ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)),
4180 SI.setOperand(0, I->getOperand(0));
4181 WorkList.push_back(I);
4189 void InstCombiner::removeFromWorkList(Instruction *I) {
4190 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
4195 /// TryToSinkInstruction - Try to move the specified instruction from its
4196 /// current block into the beginning of DestBlock, which can only happen if it's
4197 /// safe to move the instruction past all of the instructions between it and the
4198 /// end of its block.
4199 static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
4200 assert(I->hasOneUse() && "Invariants didn't hold!");
4202 // Cannot move control-flow-involving instructions.
4203 if (isa<PHINode>(I) || isa<InvokeInst>(I) || isa<CallInst>(I)) return false;
4205 // Do not sink alloca instructions out of the entry block.
4206 if (isa<AllocaInst>(I) && I->getParent() == &DestBlock->getParent()->front())
4209 // We can only sink load instructions if there is nothing between the load and
4210 // the end of block that could change the value.
4211 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
4212 if (LI->isVolatile()) return false; // Don't sink volatile loads.
4214 for (BasicBlock::iterator Scan = LI, E = LI->getParent()->end();
4216 if (Scan->mayWriteToMemory())
4220 BasicBlock::iterator InsertPos = DestBlock->begin();
4221 while (isa<PHINode>(InsertPos)) ++InsertPos;
4223 BasicBlock *SrcBlock = I->getParent();
4224 DestBlock->getInstList().splice(InsertPos, SrcBlock->getInstList(), I);
4229 bool InstCombiner::runOnFunction(Function &F) {
4230 bool Changed = false;
4231 TD = &getAnalysis<TargetData>();
4233 for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
4234 WorkList.push_back(&*i);
4237 while (!WorkList.empty()) {
4238 Instruction *I = WorkList.back(); // Get an instruction from the worklist
4239 WorkList.pop_back();
4241 // Check to see if we can DCE or ConstantPropagate the instruction...
4242 // Check to see if we can DIE the instruction...
4243 if (isInstructionTriviallyDead(I)) {
4244 // Add operands to the worklist...
4245 if (I->getNumOperands() < 4)
4246 AddUsesToWorkList(*I);
4249 I->getParent()->getInstList().erase(I);
4250 removeFromWorkList(I);
4254 // Instruction isn't dead, see if we can constant propagate it...
4255 if (Constant *C = ConstantFoldInstruction(I)) {
4256 Value* Ptr = I->getOperand(0);
4257 if (isa<GetElementPtrInst>(I) &&
4258 cast<Constant>(Ptr)->isNullValue() &&
4259 !isa<ConstantPointerNull>(C) &&
4260 cast<PointerType>(Ptr->getType())->getElementType()->isSized()) {
4261 // If this is a constant expr gep that is effectively computing an
4262 // "offsetof", fold it into 'cast int X to T*' instead of 'gep 0, 0, 12'
4263 bool isFoldableGEP = true;
4264 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
4265 if (!isa<ConstantInt>(I->getOperand(i)))
4266 isFoldableGEP = false;
4267 if (isFoldableGEP) {
4268 uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
4269 std::vector<Value*>(I->op_begin()+1, I->op_end()));
4270 C = ConstantUInt::get(Type::ULongTy, Offset);
4271 C = ConstantExpr::getCast(C, TD->getIntPtrType());
4272 C = ConstantExpr::getCast(C, I->getType());
4276 // Add operands to the worklist...
4277 AddUsesToWorkList(*I);
4278 ReplaceInstUsesWith(*I, C);
4281 I->getParent()->getInstList().erase(I);
4282 removeFromWorkList(I);
4286 // See if we can trivially sink this instruction to a successor basic block.
4287 if (I->hasOneUse()) {
4288 BasicBlock *BB = I->getParent();
4289 BasicBlock *UserParent = cast<Instruction>(I->use_back())->getParent();
4290 if (UserParent != BB) {
4291 bool UserIsSuccessor = false;
4292 // See if the user is one of our successors.
4293 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
4294 if (*SI == UserParent) {
4295 UserIsSuccessor = true;
4299 // If the user is one of our immediate successors, and if that successor
4300 // only has us as a predecessors (we'd have to split the critical edge
4301 // otherwise), we can keep going.
4302 if (UserIsSuccessor && !isa<PHINode>(I->use_back()) &&
4303 next(pred_begin(UserParent)) == pred_end(UserParent))
4304 // Okay, the CFG is simple enough, try to sink this instruction.
4305 Changed |= TryToSinkInstruction(I, UserParent);
4309 // Now that we have an instruction, try combining it to simplify it...
4310 if (Instruction *Result = visit(*I)) {
4312 // Should we replace the old instruction with a new one?
4314 DEBUG(std::cerr << "IC: Old = " << *I
4315 << " New = " << *Result);
4317 // Everything uses the new instruction now.
4318 I->replaceAllUsesWith(Result);
4320 // Push the new instruction and any users onto the worklist.
4321 WorkList.push_back(Result);
4322 AddUsersToWorkList(*Result);
4324 // Move the name to the new instruction first...
4325 std::string OldName = I->getName(); I->setName("");
4326 Result->setName(OldName);
4328 // Insert the new instruction into the basic block...
4329 BasicBlock *InstParent = I->getParent();
4330 BasicBlock::iterator InsertPos = I;
4332 if (!isa<PHINode>(Result)) // If combining a PHI, don't insert
4333 while (isa<PHINode>(InsertPos)) // middle of a block of PHIs.
4336 InstParent->getInstList().insert(InsertPos, Result);
4338 // Make sure that we reprocess all operands now that we reduced their
4340 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
4341 if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
4342 WorkList.push_back(OpI);
4344 // Instructions can end up on the worklist more than once. Make sure
4345 // we do not process an instruction that has been deleted.
4346 removeFromWorkList(I);
4348 // Erase the old instruction.
4349 InstParent->getInstList().erase(I);
4351 DEBUG(std::cerr << "IC: MOD = " << *I);
4353 // If the instruction was modified, it's possible that it is now dead.
4354 // if so, remove it.
4355 if (isInstructionTriviallyDead(I)) {
4356 // Make sure we process all operands now that we are reducing their
4358 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
4359 if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
4360 WorkList.push_back(OpI);
4362 // Instructions may end up in the worklist more than once. Erase all
4363 // occurrances of this instruction.
4364 removeFromWorkList(I);
4365 I->getParent()->getInstList().erase(I);
4367 WorkList.push_back(Result);
4368 AddUsersToWorkList(*Result);
4378 FunctionPass *llvm::createInstructionCombiningPass() {
4379 return new InstCombiner();