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
32 // N. This list is incomplete
34 //===----------------------------------------------------------------------===//
36 #define DEBUG_TYPE "instcombine"
37 #include "llvm/Transforms/Scalar.h"
38 #include "llvm/Instructions.h"
39 #include "llvm/Intrinsics.h"
40 #include "llvm/Pass.h"
41 #include "llvm/Constants.h"
42 #include "llvm/DerivedTypes.h"
43 #include "llvm/GlobalVariable.h"
44 #include "llvm/Target/TargetData.h"
45 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
46 #include "llvm/Transforms/Utils/Local.h"
47 #include "llvm/Support/CallSite.h"
48 #include "llvm/Support/GetElementPtrTypeIterator.h"
49 #include "llvm/Support/InstIterator.h"
50 #include "llvm/Support/InstVisitor.h"
51 #include "Support/Debug.h"
52 #include "Support/Statistic.h"
57 Statistic<> NumCombined ("instcombine", "Number of insts combined");
58 Statistic<> NumConstProp("instcombine", "Number of constant folds");
59 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
61 class InstCombiner : public FunctionPass,
62 public InstVisitor<InstCombiner, Instruction*> {
63 // Worklist of all of the instructions that need to be simplified.
64 std::vector<Instruction*> WorkList;
67 /// AddUsersToWorkList - When an instruction is simplified, add all users of
68 /// the instruction to the work lists because they might get more simplified
71 void AddUsersToWorkList(Instruction &I) {
72 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
74 WorkList.push_back(cast<Instruction>(*UI));
77 /// AddUsesToWorkList - When an instruction is simplified, add operands to
78 /// the work lists because they might get more simplified now.
80 void AddUsesToWorkList(Instruction &I) {
81 for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
82 if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i)))
83 WorkList.push_back(Op);
86 // removeFromWorkList - remove all instances of I from the worklist.
87 void removeFromWorkList(Instruction *I);
89 virtual bool runOnFunction(Function &F);
91 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
92 AU.addRequired<TargetData>();
96 TargetData &getTargetData() const { return *TD; }
98 // Visitation implementation - Implement instruction combining for different
99 // instruction types. The semantics are as follows:
101 // null - No change was made
102 // I - Change was made, I is still valid, I may be dead though
103 // otherwise - Change was made, replace I with returned instruction
105 Instruction *visitAdd(BinaryOperator &I);
106 Instruction *visitSub(BinaryOperator &I);
107 Instruction *visitMul(BinaryOperator &I);
108 Instruction *visitDiv(BinaryOperator &I);
109 Instruction *visitRem(BinaryOperator &I);
110 Instruction *visitAnd(BinaryOperator &I);
111 Instruction *visitOr (BinaryOperator &I);
112 Instruction *visitXor(BinaryOperator &I);
113 Instruction *visitSetCondInst(BinaryOperator &I);
114 Instruction *visitShiftInst(ShiftInst &I);
115 Instruction *visitCastInst(CastInst &CI);
116 Instruction *visitSelectInst(SelectInst &CI);
117 Instruction *visitCallInst(CallInst &CI);
118 Instruction *visitInvokeInst(InvokeInst &II);
119 Instruction *visitPHINode(PHINode &PN);
120 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
121 Instruction *visitAllocationInst(AllocationInst &AI);
122 Instruction *visitFreeInst(FreeInst &FI);
123 Instruction *visitLoadInst(LoadInst &LI);
124 Instruction *visitBranchInst(BranchInst &BI);
126 // visitInstruction - Specify what to return for unhandled instructions...
127 Instruction *visitInstruction(Instruction &I) { return 0; }
130 Instruction *visitCallSite(CallSite CS);
131 bool transformConstExprCastCall(CallSite CS);
134 // InsertNewInstBefore - insert an instruction New before instruction Old
135 // in the program. Add the new instruction to the worklist.
137 Value *InsertNewInstBefore(Instruction *New, Instruction &Old) {
138 assert(New && New->getParent() == 0 &&
139 "New instruction already inserted into a basic block!");
140 BasicBlock *BB = Old.getParent();
141 BB->getInstList().insert(&Old, New); // Insert inst
142 WorkList.push_back(New); // Add to worklist
146 // ReplaceInstUsesWith - This method is to be used when an instruction is
147 // found to be dead, replacable with another preexisting expression. Here
148 // we add all uses of I to the worklist, replace all uses of I with the new
149 // value, then return I, so that the inst combiner will know that I was
152 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
153 AddUsersToWorkList(I); // Add all modified instrs to worklist
155 I.replaceAllUsesWith(V);
158 // If we are replacing the instruction with itself, this must be in a
159 // segment of unreachable code, so just clobber the instruction.
160 I.replaceAllUsesWith(Constant::getNullValue(I.getType()));
165 // EraseInstFromFunction - When dealing with an instruction that has side
166 // effects or produces a void value, we can't rely on DCE to delete the
167 // instruction. Instead, visit methods should return the value returned by
169 Instruction *EraseInstFromFunction(Instruction &I) {
170 assert(I.use_empty() && "Cannot erase instruction that is used!");
171 AddUsesToWorkList(I);
172 removeFromWorkList(&I);
173 I.getParent()->getInstList().erase(&I);
174 return 0; // Don't do anything with FI
179 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
180 /// InsertBefore instruction. This is specialized a bit to avoid inserting
181 /// casts that are known to not do anything...
183 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
184 Instruction *InsertBefore);
186 // SimplifyCommutative - This performs a few simplifications for commutative
188 bool SimplifyCommutative(BinaryOperator &I);
190 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
191 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
194 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
197 // getComplexity: Assign a complexity or rank value to LLVM Values...
198 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
199 static unsigned getComplexity(Value *V) {
200 if (isa<Instruction>(V)) {
201 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
205 if (isa<Argument>(V)) return 2;
206 return isa<Constant>(V) ? 0 : 1;
209 // isOnlyUse - Return true if this instruction will be deleted if we stop using
211 static bool isOnlyUse(Value *V) {
212 return V->hasOneUse() || isa<Constant>(V);
215 // getSignedIntegralType - Given an unsigned integral type, return the signed
216 // version of it that has the same size.
217 static const Type *getSignedIntegralType(const Type *Ty) {
218 switch (Ty->getPrimitiveID()) {
219 default: assert(0 && "Invalid unsigned integer type!"); abort();
220 case Type::UByteTyID: return Type::SByteTy;
221 case Type::UShortTyID: return Type::ShortTy;
222 case Type::UIntTyID: return Type::IntTy;
223 case Type::ULongTyID: return Type::LongTy;
227 // getUnsignedIntegralType - Given an signed integral type, return the unsigned
228 // version of it that has the same size.
229 static const Type *getUnsignedIntegralType(const Type *Ty) {
230 switch (Ty->getPrimitiveID()) {
231 default: assert(0 && "Invalid signed integer type!"); abort();
232 case Type::SByteTyID: return Type::UByteTy;
233 case Type::ShortTyID: return Type::UShortTy;
234 case Type::IntTyID: return Type::UIntTy;
235 case Type::LongTyID: return Type::ULongTy;
239 // getPromotedType - Return the specified type promoted as it would be to pass
240 // though a va_arg area...
241 static const Type *getPromotedType(const Type *Ty) {
242 switch (Ty->getPrimitiveID()) {
243 case Type::SByteTyID:
244 case Type::ShortTyID: return Type::IntTy;
245 case Type::UByteTyID:
246 case Type::UShortTyID: return Type::UIntTy;
247 case Type::FloatTyID: return Type::DoubleTy;
252 // SimplifyCommutative - This performs a few simplifications for commutative
255 // 1. Order operands such that they are listed from right (least complex) to
256 // left (most complex). This puts constants before unary operators before
259 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
260 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
262 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
263 bool Changed = false;
264 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
265 Changed = !I.swapOperands();
267 if (!I.isAssociative()) return Changed;
268 Instruction::BinaryOps Opcode = I.getOpcode();
269 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
270 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
271 if (isa<Constant>(I.getOperand(1))) {
272 Constant *Folded = ConstantExpr::get(I.getOpcode(),
273 cast<Constant>(I.getOperand(1)),
274 cast<Constant>(Op->getOperand(1)));
275 I.setOperand(0, Op->getOperand(0));
276 I.setOperand(1, Folded);
278 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
279 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
280 isOnlyUse(Op) && isOnlyUse(Op1)) {
281 Constant *C1 = cast<Constant>(Op->getOperand(1));
282 Constant *C2 = cast<Constant>(Op1->getOperand(1));
284 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
285 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
286 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
289 WorkList.push_back(New);
290 I.setOperand(0, New);
291 I.setOperand(1, Folded);
298 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
299 // if the LHS is a constant zero (which is the 'negate' form).
301 static inline Value *dyn_castNegVal(Value *V) {
302 if (BinaryOperator::isNeg(V))
303 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
305 // Constants can be considered to be negated values if they can be folded...
306 if (Constant *C = dyn_cast<Constant>(V))
307 return ConstantExpr::get(Instruction::Sub,
308 Constant::getNullValue(V->getType()), C);
312 static Constant *NotConstant(Constant *C) {
313 return ConstantExpr::get(Instruction::Xor, C,
314 ConstantIntegral::getAllOnesValue(C->getType()));
317 static inline Value *dyn_castNotVal(Value *V) {
318 if (BinaryOperator::isNot(V))
319 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
321 // Constants can be considered to be not'ed values...
322 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
323 return NotConstant(C);
327 // dyn_castFoldableMul - If this value is a multiply that can be folded into
328 // other computations (because it has a constant operand), return the
329 // non-constant operand of the multiply.
331 static inline Value *dyn_castFoldableMul(Value *V) {
332 if (V->hasOneUse() && V->getType()->isInteger())
333 if (Instruction *I = dyn_cast<Instruction>(V))
334 if (I->getOpcode() == Instruction::Mul)
335 if (isa<Constant>(I->getOperand(1)))
336 return I->getOperand(0);
340 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
341 // a constant, return the constant being anded with.
343 template<class ValueType>
344 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
345 if (Instruction *I = dyn_cast<Instruction>(V))
346 if (I->getOpcode() == Instruction::And)
347 return dyn_cast<Constant>(I->getOperand(1));
349 // If this is a constant, it acts just like we were masking with it.
350 return dyn_cast<Constant>(V);
353 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
355 static unsigned Log2(uint64_t Val) {
356 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
359 if (Val & 1) return 0; // Multiple bits set?
367 /// AssociativeOpt - Perform an optimization on an associative operator. This
368 /// function is designed to check a chain of associative operators for a
369 /// potential to apply a certain optimization. Since the optimization may be
370 /// applicable if the expression was reassociated, this checks the chain, then
371 /// reassociates the expression as necessary to expose the optimization
372 /// opportunity. This makes use of a special Functor, which must define
373 /// 'shouldApply' and 'apply' methods.
375 template<typename Functor>
376 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
377 unsigned Opcode = Root.getOpcode();
378 Value *LHS = Root.getOperand(0);
380 // Quick check, see if the immediate LHS matches...
381 if (F.shouldApply(LHS))
382 return F.apply(Root);
384 // Otherwise, if the LHS is not of the same opcode as the root, return.
385 Instruction *LHSI = dyn_cast<Instruction>(LHS);
386 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
387 // Should we apply this transform to the RHS?
388 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
390 // If not to the RHS, check to see if we should apply to the LHS...
391 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
392 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
396 // If the functor wants to apply the optimization to the RHS of LHSI,
397 // reassociate the expression from ((? op A) op B) to (? op (A op B))
399 BasicBlock *BB = Root.getParent();
400 // All of the instructions have a single use and have no side-effects,
401 // because of this, we can pull them all into the current basic block.
402 if (LHSI->getParent() != BB) {
403 // Move all of the instructions from root to LHSI into the current
405 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
406 Instruction *LastUse = &Root;
407 while (TmpLHSI->getParent() == BB) {
409 TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
412 // Loop over all of the instructions in other blocks, moving them into
414 Value *TmpLHS = TmpLHSI;
416 TmpLHSI = cast<Instruction>(TmpLHS);
417 // Remove from current block...
418 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
419 // Insert before the last instruction...
420 BB->getInstList().insert(LastUse, TmpLHSI);
421 TmpLHS = TmpLHSI->getOperand(0);
422 } while (TmpLHSI != LHSI);
425 // Now all of the instructions are in the current basic block, go ahead
426 // and perform the reassociation.
427 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
429 // First move the selected RHS to the LHS of the root...
430 Root.setOperand(0, LHSI->getOperand(1));
432 // Make what used to be the LHS of the root be the user of the root...
433 Value *ExtraOperand = TmpLHSI->getOperand(1);
434 if (&Root != TmpLHSI)
435 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
437 Root.replaceAllUsesWith(Constant::getNullValue(TmpLHSI->getType()));
440 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
441 BB->getInstList().remove(&Root); // Remove root from the BB
442 BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
444 // Now propagate the ExtraOperand down the chain of instructions until we
446 while (TmpLHSI != LHSI) {
447 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
448 Value *NextOp = NextLHSI->getOperand(1);
449 NextLHSI->setOperand(1, ExtraOperand);
451 ExtraOperand = NextOp;
454 // Now that the instructions are reassociated, have the functor perform
455 // the transformation...
456 return F.apply(Root);
459 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
465 // AddRHS - Implements: X + X --> X << 1
468 AddRHS(Value *rhs) : RHS(rhs) {}
469 bool shouldApply(Value *LHS) const { return LHS == RHS; }
470 Instruction *apply(BinaryOperator &Add) const {
471 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
472 ConstantInt::get(Type::UByteTy, 1));
476 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
478 struct AddMaskingAnd {
480 AddMaskingAnd(Constant *c) : C2(c) {}
481 bool shouldApply(Value *LHS) const {
482 if (Constant *C1 = dyn_castMaskingAnd(LHS))
483 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
486 Instruction *apply(BinaryOperator &Add) const {
487 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
494 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
495 bool Changed = SimplifyCommutative(I);
496 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
499 if (!I.getType()->isFloatingPoint() && // -0 + +0 = +0, so it's not a noop
500 RHS == Constant::getNullValue(I.getType()))
501 return ReplaceInstUsesWith(I, LHS);
504 if (I.getType()->isInteger())
505 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
508 if (Value *V = dyn_castNegVal(LHS))
509 return BinaryOperator::create(Instruction::Sub, RHS, V);
512 if (!isa<Constant>(RHS))
513 if (Value *V = dyn_castNegVal(RHS))
514 return BinaryOperator::create(Instruction::Sub, LHS, V);
516 // X*C + X --> X * (C+1)
517 if (dyn_castFoldableMul(LHS) == RHS) {
519 ConstantExpr::get(Instruction::Add,
520 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
521 ConstantInt::get(I.getType(), 1));
522 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
525 // X + X*C --> X * (C+1)
526 if (dyn_castFoldableMul(RHS) == LHS) {
528 ConstantExpr::get(Instruction::Add,
529 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
530 ConstantInt::get(I.getType(), 1));
531 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
534 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
535 if (Constant *C2 = dyn_castMaskingAnd(RHS))
536 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
538 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
539 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
540 switch (ILHS->getOpcode()) {
541 case Instruction::Xor:
542 // ~X + C --> (C-1) - X
543 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
544 if (XorRHS->isAllOnesValue())
545 return BinaryOperator::create(Instruction::Sub,
546 ConstantExpr::get(Instruction::Sub,
547 CRHS, ConstantInt::get(I.getType(), 1)),
548 ILHS->getOperand(0));
555 return Changed ? &I : 0;
558 // isSignBit - Return true if the value represented by the constant only has the
559 // highest order bit set.
560 static bool isSignBit(ConstantInt *CI) {
561 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
562 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
565 static unsigned getTypeSizeInBits(const Type *Ty) {
566 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
569 /// RemoveNoopCast - Strip off nonconverting casts from the value.
571 static Value *RemoveNoopCast(Value *V) {
572 if (CastInst *CI = dyn_cast<CastInst>(V)) {
573 const Type *CTy = CI->getType();
574 const Type *OpTy = CI->getOperand(0)->getType();
575 if (CTy->isInteger() && OpTy->isInteger()) {
576 if (CTy->getPrimitiveSize() == OpTy->getPrimitiveSize())
577 return RemoveNoopCast(CI->getOperand(0));
578 } else if (isa<PointerType>(CTy) && isa<PointerType>(OpTy))
579 return RemoveNoopCast(CI->getOperand(0));
584 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
585 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
587 if (Op0 == Op1) // sub X, X -> 0
588 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
590 // If this is a 'B = x-(-A)', change to B = x+A...
591 if (Value *V = dyn_castNegVal(Op1))
592 return BinaryOperator::create(Instruction::Add, Op0, V);
594 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
595 // Replace (-1 - A) with (~A)...
596 if (C->isAllOnesValue())
597 return BinaryOperator::createNot(Op1);
599 // C - ~X == X + (1+C)
600 if (BinaryOperator::isNot(Op1))
601 return BinaryOperator::create(Instruction::Add,
602 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
603 ConstantExpr::get(Instruction::Add, C,
604 ConstantInt::get(I.getType(), 1)));
605 // -((uint)X >> 31) -> ((int)X >> 31)
606 // -((int)X >> 31) -> ((uint)X >> 31)
607 if (C->isNullValue()) {
608 Value *NoopCastedRHS = RemoveNoopCast(Op1);
609 if (ShiftInst *SI = dyn_cast<ShiftInst>(NoopCastedRHS))
610 if (SI->getOpcode() == Instruction::Shr)
611 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
613 if (SI->getType()->isSigned())
614 NewTy = getUnsignedIntegralType(SI->getType());
616 NewTy = getSignedIntegralType(SI->getType());
617 // Check to see if we are shifting out everything but the sign bit.
618 if (CU->getValue() == SI->getType()->getPrimitiveSize()*8-1) {
619 // Ok, the transformation is safe. Insert a cast of the incoming
620 // value, then the new shift, then the new cast.
621 Instruction *FirstCast = new CastInst(SI->getOperand(0), NewTy,
622 SI->getOperand(0)->getName());
623 Value *InV = InsertNewInstBefore(FirstCast, I);
624 Instruction *NewShift = new ShiftInst(Instruction::Shr, FirstCast,
626 if (NewShift->getType() == I.getType())
629 InV = InsertNewInstBefore(NewShift, I);
630 return new CastInst(NewShift, I.getType());
637 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
638 if (Op1I->hasOneUse()) {
639 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
640 // is not used by anyone else...
642 if (Op1I->getOpcode() == Instruction::Sub &&
643 !Op1I->getType()->isFloatingPoint()) {
644 // Swap the two operands of the subexpr...
645 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
646 Op1I->setOperand(0, IIOp1);
647 Op1I->setOperand(1, IIOp0);
649 // Create the new top level add instruction...
650 return BinaryOperator::create(Instruction::Add, Op0, Op1);
653 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
655 if (Op1I->getOpcode() == Instruction::And &&
656 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
657 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
659 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
660 return BinaryOperator::create(Instruction::And, Op0, NewNot);
663 // X - X*C --> X * (1-C)
664 if (dyn_castFoldableMul(Op1I) == Op0) {
666 ConstantExpr::get(Instruction::Sub,
667 ConstantInt::get(I.getType(), 1),
668 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
669 assert(CP1 && "Couldn't constant fold 1-C?");
670 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
674 // X*C - X --> X * (C-1)
675 if (dyn_castFoldableMul(Op0) == Op1) {
677 ConstantExpr::get(Instruction::Sub,
678 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
679 ConstantInt::get(I.getType(), 1));
680 assert(CP1 && "Couldn't constant fold C - 1?");
681 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
687 /// isSignBitCheck - Given an exploded setcc instruction, return true if it is
688 /// really just returns true if the most significant (sign) bit is set.
689 static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
690 if (RHS->getType()->isSigned()) {
691 // True if source is LHS < 0 or LHS <= -1
692 return Opcode == Instruction::SetLT && RHS->isNullValue() ||
693 Opcode == Instruction::SetLE && RHS->isAllOnesValue();
695 ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
696 // True if source is LHS > 127 or LHS >= 128, where the constants depend on
697 // the size of the integer type.
698 if (Opcode == Instruction::SetGE)
699 return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1);
700 if (Opcode == Instruction::SetGT)
701 return RHSC->getValue() ==
702 (1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
707 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
708 bool Changed = SimplifyCommutative(I);
709 Value *Op0 = I.getOperand(0);
711 // Simplify mul instructions with a constant RHS...
712 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
713 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
715 // ((X << C1)*C2) == (X * (C2 << C1))
716 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
717 if (SI->getOpcode() == Instruction::Shl)
718 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
719 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
720 ConstantExpr::get(Instruction::Shl, CI, ShOp));
722 if (CI->isNullValue())
723 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
724 if (CI->equalsInt(1)) // X * 1 == X
725 return ReplaceInstUsesWith(I, Op0);
726 if (CI->isAllOnesValue()) // X * -1 == 0 - X
727 return BinaryOperator::createNeg(Op0, I.getName());
729 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
730 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
731 return new ShiftInst(Instruction::Shl, Op0,
732 ConstantUInt::get(Type::UByteTy, C));
734 ConstantFP *Op1F = cast<ConstantFP>(Op1);
735 if (Op1F->isNullValue())
736 return ReplaceInstUsesWith(I, Op1);
738 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
739 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
740 if (Op1F->getValue() == 1.0)
741 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
745 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
746 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
747 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
749 // If one of the operands of the multiply is a cast from a boolean value, then
750 // we know the bool is either zero or one, so this is a 'masking' multiply.
751 // See if we can simplify things based on how the boolean was originally
753 CastInst *BoolCast = 0;
754 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
755 if (CI->getOperand(0)->getType() == Type::BoolTy)
758 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
759 if (CI->getOperand(0)->getType() == Type::BoolTy)
762 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
763 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
764 const Type *SCOpTy = SCIOp0->getType();
766 // If the setcc is true iff the sign bit of X is set, then convert this
767 // multiply into a shift/and combination.
768 if (isa<ConstantInt>(SCIOp1) &&
769 isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
770 // Shift the X value right to turn it into "all signbits".
771 Constant *Amt = ConstantUInt::get(Type::UByteTy,
772 SCOpTy->getPrimitiveSize()*8-1);
773 if (SCIOp0->getType()->isUnsigned()) {
774 const Type *NewTy = getSignedIntegralType(SCIOp0->getType());
775 SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
776 SCIOp0->getName()), I);
780 InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
781 BoolCast->getOperand(0)->getName()+
784 // If the multiply type is not the same as the source type, sign extend
785 // or truncate to the multiply type.
786 if (I.getType() != V->getType())
787 V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
789 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
790 return BinaryOperator::create(Instruction::And, V, OtherOp);
795 return Changed ? &I : 0;
798 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
800 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
801 if (RHS->equalsInt(1))
802 return ReplaceInstUsesWith(I, I.getOperand(0));
804 // Check to see if this is an unsigned division with an exact power of 2,
805 // if so, convert to a right shift.
806 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
807 if (uint64_t Val = C->getValue()) // Don't break X / 0
808 if (uint64_t C = Log2(Val))
809 return new ShiftInst(Instruction::Shr, I.getOperand(0),
810 ConstantUInt::get(Type::UByteTy, C));
813 // 0 / X == 0, we don't need to preserve faults!
814 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
815 if (LHS->equalsInt(0))
816 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
822 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
823 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
824 if (RHS->equalsInt(1)) // X % 1 == 0
825 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
826 if (RHS->isAllOnesValue()) // X % -1 == 0
827 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
829 // Check to see if this is an unsigned remainder with an exact power of 2,
830 // if so, convert to a bitwise and.
831 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
832 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
834 return BinaryOperator::create(Instruction::And, I.getOperand(0),
835 ConstantUInt::get(I.getType(), Val-1));
838 // 0 % X == 0, we don't need to preserve faults!
839 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
840 if (LHS->equalsInt(0))
841 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
846 // isMaxValueMinusOne - return true if this is Max-1
847 static bool isMaxValueMinusOne(const ConstantInt *C) {
848 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
849 // Calculate -1 casted to the right type...
850 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
851 uint64_t Val = ~0ULL; // All ones
852 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
853 return CU->getValue() == Val-1;
856 const ConstantSInt *CS = cast<ConstantSInt>(C);
858 // Calculate 0111111111..11111
859 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
860 int64_t Val = INT64_MAX; // All ones
861 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
862 return CS->getValue() == Val-1;
865 // isMinValuePlusOne - return true if this is Min+1
866 static bool isMinValuePlusOne(const ConstantInt *C) {
867 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
868 return CU->getValue() == 1;
870 const ConstantSInt *CS = cast<ConstantSInt>(C);
872 // Calculate 1111111111000000000000
873 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
874 int64_t Val = -1; // All ones
875 Val <<= TypeBits-1; // Shift over to the right spot
876 return CS->getValue() == Val+1;
879 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
880 /// are carefully arranged to allow folding of expressions such as:
882 /// (A < B) | (A > B) --> (A != B)
884 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
885 /// represents that the comparison is true if A == B, and bit value '1' is true
888 static unsigned getSetCondCode(const SetCondInst *SCI) {
889 switch (SCI->getOpcode()) {
891 case Instruction::SetGT: return 1;
892 case Instruction::SetEQ: return 2;
893 case Instruction::SetGE: return 3;
894 case Instruction::SetLT: return 4;
895 case Instruction::SetNE: return 5;
896 case Instruction::SetLE: return 6;
899 assert(0 && "Invalid SetCC opcode!");
904 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
905 /// opcode and two operands into either a constant true or false, or a brand new
906 /// SetCC instruction.
907 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
909 case 0: return ConstantBool::False;
910 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
911 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
912 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
913 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
914 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
915 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
916 case 7: return ConstantBool::True;
917 default: assert(0 && "Illegal SetCCCode!"); return 0;
921 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
922 struct FoldSetCCLogical {
925 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
926 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
927 bool shouldApply(Value *V) const {
928 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
929 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
930 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
933 Instruction *apply(BinaryOperator &Log) const {
934 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
935 if (SCI->getOperand(0) != LHS) {
936 assert(SCI->getOperand(1) == LHS);
937 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
940 unsigned LHSCode = getSetCondCode(SCI);
941 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
943 switch (Log.getOpcode()) {
944 case Instruction::And: Code = LHSCode & RHSCode; break;
945 case Instruction::Or: Code = LHSCode | RHSCode; break;
946 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
947 default: assert(0 && "Illegal logical opcode!"); return 0;
950 Value *RV = getSetCCValue(Code, LHS, RHS);
951 if (Instruction *I = dyn_cast<Instruction>(RV))
953 // Otherwise, it's a constant boolean value...
954 return IC.ReplaceInstUsesWith(Log, RV);
959 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
960 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
961 // guaranteed to be either a shift instruction or a binary operator.
962 Instruction *InstCombiner::OptAndOp(Instruction *Op,
963 ConstantIntegral *OpRHS,
964 ConstantIntegral *AndRHS,
965 BinaryOperator &TheAnd) {
966 Value *X = Op->getOperand(0);
967 Constant *Together = 0;
968 if (!isa<ShiftInst>(Op))
969 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
971 switch (Op->getOpcode()) {
972 case Instruction::Xor:
973 if (Together->isNullValue()) {
974 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
975 return BinaryOperator::create(Instruction::And, X, AndRHS);
976 } else if (Op->hasOneUse()) {
977 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
978 std::string OpName = Op->getName(); Op->setName("");
979 Instruction *And = BinaryOperator::create(Instruction::And,
981 InsertNewInstBefore(And, TheAnd);
982 return BinaryOperator::create(Instruction::Xor, And, Together);
985 case Instruction::Or:
986 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
987 if (Together->isNullValue())
988 return BinaryOperator::create(Instruction::And, X, AndRHS);
990 if (Together == AndRHS) // (X | C) & C --> C
991 return ReplaceInstUsesWith(TheAnd, AndRHS);
993 if (Op->hasOneUse() && Together != OpRHS) {
994 // (X | C1) & C2 --> (X | (C1&C2)) & C2
995 std::string Op0Name = Op->getName(); Op->setName("");
996 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
998 InsertNewInstBefore(Or, TheAnd);
999 return BinaryOperator::create(Instruction::And, Or, AndRHS);
1003 case Instruction::Add:
1004 if (Op->hasOneUse()) {
1005 // Adding a one to a single bit bit-field should be turned into an XOR
1006 // of the bit. First thing to check is to see if this AND is with a
1007 // single bit constant.
1008 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
1010 // Clear bits that are not part of the constant.
1011 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
1013 // If there is only one bit set...
1014 if ((AndRHSV & (AndRHSV-1)) == 0) {
1015 // Ok, at this point, we know that we are masking the result of the
1016 // ADD down to exactly one bit. If the constant we are adding has
1017 // no bits set below this bit, then we can eliminate the ADD.
1018 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
1020 // Check to see if any bits below the one bit set in AndRHSV are set.
1021 if ((AddRHS & (AndRHSV-1)) == 0) {
1022 // If not, the only thing that can effect the output of the AND is
1023 // the bit specified by AndRHSV. If that bit is set, the effect of
1024 // the XOR is to toggle the bit. If it is clear, then the ADD has
1026 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
1027 TheAnd.setOperand(0, X);
1030 std::string Name = Op->getName(); Op->setName("");
1031 // Pull the XOR out of the AND.
1032 Instruction *NewAnd =
1033 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
1034 InsertNewInstBefore(NewAnd, TheAnd);
1035 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
1042 case Instruction::Shl: {
1043 // We know that the AND will not produce any of the bits shifted in, so if
1044 // the anded constant includes them, clear them now!
1046 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1047 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1048 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
1050 TheAnd.setOperand(1, CI);
1055 case Instruction::Shr:
1056 // We know that the AND will not produce any of the bits shifted in, so if
1057 // the anded constant includes them, clear them now! This only applies to
1058 // unsigned shifts, because a signed shr may bring in set bits!
1060 if (AndRHS->getType()->isUnsigned()) {
1061 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1062 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1063 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
1065 TheAnd.setOperand(1, CI);
1075 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
1076 bool Changed = SimplifyCommutative(I);
1077 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1079 // and X, X = X and X, 0 == 0
1080 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1081 return ReplaceInstUsesWith(I, Op1);
1084 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1085 if (RHS->isAllOnesValue())
1086 return ReplaceInstUsesWith(I, Op0);
1088 // Optimize a variety of ((val OP C1) & C2) combinations...
1089 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
1090 Instruction *Op0I = cast<Instruction>(Op0);
1091 Value *X = Op0I->getOperand(0);
1092 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1093 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
1098 Value *Op0NotVal = dyn_castNotVal(Op0);
1099 Value *Op1NotVal = dyn_castNotVal(Op1);
1101 // (~A & ~B) == (~(A | B)) - Demorgan's Law
1102 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1103 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
1104 Op1NotVal,I.getName()+".demorgan");
1105 InsertNewInstBefore(Or, I);
1106 return BinaryOperator::createNot(Or);
1109 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1110 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1112 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1113 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1114 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1117 return Changed ? &I : 0;
1122 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1123 bool Changed = SimplifyCommutative(I);
1124 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1126 // or X, X = X or X, 0 == X
1127 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1128 return ReplaceInstUsesWith(I, Op0);
1131 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1132 if (RHS->isAllOnesValue())
1133 return ReplaceInstUsesWith(I, Op1);
1135 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1136 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1137 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
1138 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1139 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1140 Instruction *Or = BinaryOperator::create(Instruction::Or,
1141 Op0I->getOperand(0), RHS,
1143 InsertNewInstBefore(Or, I);
1144 return BinaryOperator::create(Instruction::And, Or,
1145 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
1148 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1149 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
1150 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1151 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1152 Instruction *Or = BinaryOperator::create(Instruction::Or,
1153 Op0I->getOperand(0), RHS,
1155 InsertNewInstBefore(Or, I);
1156 return BinaryOperator::create(Instruction::Xor, Or,
1157 ConstantExpr::get(Instruction::And, Op0CI,
1163 // (A & C1)|(A & C2) == A & (C1|C2)
1164 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
1165 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
1166 if (LHS->getOperand(0) == RHS->getOperand(0))
1167 if (Constant *C0 = dyn_castMaskingAnd(LHS))
1168 if (Constant *C1 = dyn_castMaskingAnd(RHS))
1169 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
1170 ConstantExpr::get(Instruction::Or, C0, C1));
1172 Value *Op0NotVal = dyn_castNotVal(Op0);
1173 Value *Op1NotVal = dyn_castNotVal(Op1);
1175 if (Op1 == Op0NotVal) // ~A | A == -1
1176 return ReplaceInstUsesWith(I,
1177 ConstantIntegral::getAllOnesValue(I.getType()));
1179 if (Op0 == Op1NotVal) // A | ~A == -1
1180 return ReplaceInstUsesWith(I,
1181 ConstantIntegral::getAllOnesValue(I.getType()));
1183 // (~A | ~B) == (~(A & B)) - Demorgan's Law
1184 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1185 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
1186 Op1NotVal,I.getName()+".demorgan",
1188 WorkList.push_back(And);
1189 return BinaryOperator::createNot(And);
1192 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1193 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1194 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1197 return Changed ? &I : 0;
1200 // XorSelf - Implements: X ^ X --> 0
1203 XorSelf(Value *rhs) : RHS(rhs) {}
1204 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1205 Instruction *apply(BinaryOperator &Xor) const {
1211 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1212 bool Changed = SimplifyCommutative(I);
1213 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1215 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1216 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1217 assert(Result == &I && "AssociativeOpt didn't work?");
1218 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1221 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1223 if (RHS->isNullValue())
1224 return ReplaceInstUsesWith(I, Op0);
1226 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1227 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1228 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1229 if (RHS == ConstantBool::True && SCI->hasOneUse())
1230 return new SetCondInst(SCI->getInverseCondition(),
1231 SCI->getOperand(0), SCI->getOperand(1));
1233 // ~(c-X) == X-c-1 == X+(-c-1)
1234 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1235 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1236 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1237 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1238 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1239 ConstantInt::get(I.getType(), 1));
1240 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1244 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1245 switch (Op0I->getOpcode()) {
1246 case Instruction::Add:
1247 // ~(X-c) --> (-c-1)-X
1248 if (RHS->isAllOnesValue()) {
1249 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1250 Constant::getNullValue(Op0CI->getType()), Op0CI);
1251 return BinaryOperator::create(Instruction::Sub,
1252 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1253 ConstantInt::get(I.getType(), 1)),
1254 Op0I->getOperand(0));
1257 case Instruction::And:
1258 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1259 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1260 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1262 case Instruction::Or:
1263 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1264 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1265 return BinaryOperator::create(Instruction::And, Op0,
1273 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1275 return ReplaceInstUsesWith(I,
1276 ConstantIntegral::getAllOnesValue(I.getType()));
1278 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1280 return ReplaceInstUsesWith(I,
1281 ConstantIntegral::getAllOnesValue(I.getType()));
1283 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1284 if (Op1I->getOpcode() == Instruction::Or) {
1285 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1286 cast<BinaryOperator>(Op1I)->swapOperands();
1288 std::swap(Op0, Op1);
1289 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1291 std::swap(Op0, Op1);
1293 } else if (Op1I->getOpcode() == Instruction::Xor) {
1294 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1295 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1296 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1297 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1300 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1301 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1302 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1303 cast<BinaryOperator>(Op0I)->swapOperands();
1304 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1305 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1306 WorkList.push_back(cast<Instruction>(NotB));
1307 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1310 } else if (Op0I->getOpcode() == Instruction::Xor) {
1311 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1312 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1313 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1314 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1317 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1318 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1319 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1320 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1321 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1323 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1324 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1325 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1328 return Changed ? &I : 0;
1331 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1332 static Constant *AddOne(ConstantInt *C) {
1333 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1334 ConstantInt::get(C->getType(), 1));
1335 assert(Result && "Constant folding integer addition failed!");
1338 static Constant *SubOne(ConstantInt *C) {
1339 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1340 ConstantInt::get(C->getType(), 1));
1341 assert(Result && "Constant folding integer addition failed!");
1345 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1346 // true when both operands are equal...
1348 static bool isTrueWhenEqual(Instruction &I) {
1349 return I.getOpcode() == Instruction::SetEQ ||
1350 I.getOpcode() == Instruction::SetGE ||
1351 I.getOpcode() == Instruction::SetLE;
1354 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1355 bool Changed = SimplifyCommutative(I);
1356 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1357 const Type *Ty = Op0->getType();
1361 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1363 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1364 if (isa<ConstantPointerNull>(Op1) &&
1365 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1366 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1369 // setcc's with boolean values can always be turned into bitwise operations
1370 if (Ty == Type::BoolTy) {
1371 // If this is <, >, or !=, we can change this into a simple xor instruction
1372 if (!isTrueWhenEqual(I))
1373 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1375 // Otherwise we need to make a temporary intermediate instruction and insert
1376 // it into the instruction stream. This is what we are after:
1378 // seteq bool %A, %B -> ~(A^B)
1379 // setle bool %A, %B -> ~A | B
1380 // setge bool %A, %B -> A | ~B
1382 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1383 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1385 InsertNewInstBefore(Xor, I);
1386 return BinaryOperator::createNot(Xor);
1389 // Handle the setXe cases...
1390 assert(I.getOpcode() == Instruction::SetGE ||
1391 I.getOpcode() == Instruction::SetLE);
1393 if (I.getOpcode() == Instruction::SetGE)
1394 std::swap(Op0, Op1); // Change setge -> setle
1396 // Now we just have the SetLE case.
1397 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1398 InsertNewInstBefore(Not, I);
1399 return BinaryOperator::create(Instruction::Or, Not, Op1);
1402 // Check to see if we are doing one of many comparisons against constant
1403 // integers at the end of their ranges...
1405 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1406 // Simplify seteq and setne instructions...
1407 if (I.getOpcode() == Instruction::SetEQ ||
1408 I.getOpcode() == Instruction::SetNE) {
1409 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1411 // If the first operand is (and|or|xor) with a constant, and the second
1412 // operand is a constant, simplify a bit.
1413 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1414 switch (BO->getOpcode()) {
1415 case Instruction::Add:
1416 if (CI->isNullValue()) {
1417 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1418 // efficiently invertible, or if the add has just this one use.
1419 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1420 if (Value *NegVal = dyn_castNegVal(BOp1))
1421 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1422 else if (Value *NegVal = dyn_castNegVal(BOp0))
1423 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1424 else if (BO->hasOneUse()) {
1425 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1427 InsertNewInstBefore(Neg, I);
1428 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1432 case Instruction::Xor:
1433 // For the xor case, we can xor two constants together, eliminating
1434 // the explicit xor.
1435 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1436 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1437 ConstantExpr::get(Instruction::Xor, CI, BOC));
1440 case Instruction::Sub:
1441 // Replace (([sub|xor] A, B) != 0) with (A != B)
1442 if (CI->isNullValue())
1443 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1447 case Instruction::Or:
1448 // If bits are being or'd in that are not present in the constant we
1449 // are comparing against, then the comparison could never succeed!
1450 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1451 Constant *NotCI = NotConstant(CI);
1452 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1453 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1457 case Instruction::And:
1458 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1459 // If bits are being compared against that are and'd out, then the
1460 // comparison can never succeed!
1461 if (!ConstantExpr::get(Instruction::And, CI,
1462 NotConstant(BOC))->isNullValue())
1463 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1465 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1466 // to be a signed value as appropriate.
1467 if (isSignBit(BOC)) {
1468 Value *X = BO->getOperand(0);
1469 // If 'X' is not signed, insert a cast now...
1470 if (!BOC->getType()->isSigned()) {
1471 const Type *DestTy = getSignedIntegralType(BOC->getType());
1472 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1473 InsertNewInstBefore(NewCI, I);
1476 return new SetCondInst(isSetNE ? Instruction::SetLT :
1477 Instruction::SetGE, X,
1478 Constant::getNullValue(X->getType()));
1484 } else { // Not a SetEQ/SetNE
1485 // If the LHS is a cast from an integral value of the same size,
1486 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
1487 Value *CastOp = Cast->getOperand(0);
1488 const Type *SrcTy = CastOp->getType();
1489 unsigned SrcTySize = SrcTy->getPrimitiveSize();
1490 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
1491 SrcTySize == Cast->getType()->getPrimitiveSize()) {
1492 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
1493 "Source and destination signednesses should differ!");
1494 if (Cast->getType()->isSigned()) {
1495 // If this is a signed comparison, check for comparisons in the
1496 // vicinity of zero.
1497 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
1499 return BinaryOperator::create(Instruction::SetGT, CastOp,
1500 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
1501 else if (I.getOpcode() == Instruction::SetGT &&
1502 cast<ConstantSInt>(CI)->getValue() == -1)
1503 // X > -1 => x < 128
1504 return BinaryOperator::create(Instruction::SetLT, CastOp,
1505 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
1507 ConstantUInt *CUI = cast<ConstantUInt>(CI);
1508 if (I.getOpcode() == Instruction::SetLT &&
1509 CUI->getValue() == 1ULL << (SrcTySize*8-1))
1510 // X < 128 => X > -1
1511 return BinaryOperator::create(Instruction::SetGT, CastOp,
1512 ConstantSInt::get(SrcTy, -1));
1513 else if (I.getOpcode() == Instruction::SetGT &&
1514 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
1516 return BinaryOperator::create(Instruction::SetLT, CastOp,
1517 Constant::getNullValue(SrcTy));
1523 // Check to see if we are comparing against the minimum or maximum value...
1524 if (CI->isMinValue()) {
1525 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1526 return ReplaceInstUsesWith(I, ConstantBool::False);
1527 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1528 return ReplaceInstUsesWith(I, ConstantBool::True);
1529 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1530 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1531 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1532 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1534 } else if (CI->isMaxValue()) {
1535 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1536 return ReplaceInstUsesWith(I, ConstantBool::False);
1537 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1538 return ReplaceInstUsesWith(I, ConstantBool::True);
1539 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1540 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1541 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1542 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1544 // Comparing against a value really close to min or max?
1545 } else if (isMinValuePlusOne(CI)) {
1546 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1547 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1548 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1549 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1551 } else if (isMaxValueMinusOne(CI)) {
1552 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1553 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1554 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1555 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1558 // If we still have a setle or setge instruction, turn it into the
1559 // appropriate setlt or setgt instruction. Since the border cases have
1560 // already been handled above, this requires little checking.
1562 if (I.getOpcode() == Instruction::SetLE)
1563 return BinaryOperator::create(Instruction::SetLT, Op0, AddOne(CI));
1564 if (I.getOpcode() == Instruction::SetGE)
1565 return BinaryOperator::create(Instruction::SetGT, Op0, SubOne(CI));
1568 // Test to see if the operands of the setcc are casted versions of other
1569 // values. If the cast can be stripped off both arguments, we do so now.
1570 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1571 Value *CastOp0 = CI->getOperand(0);
1572 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1573 (isa<Constant>(Op1) || isa<CastInst>(Op1)) &&
1574 (I.getOpcode() == Instruction::SetEQ ||
1575 I.getOpcode() == Instruction::SetNE)) {
1576 // We keep moving the cast from the left operand over to the right
1577 // operand, where it can often be eliminated completely.
1580 // If operand #1 is a cast instruction, see if we can eliminate it as
1582 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1583 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1585 Op1 = CI2->getOperand(0);
1587 // If Op1 is a constant, we can fold the cast into the constant.
1588 if (Op1->getType() != Op0->getType())
1589 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1590 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1592 // Otherwise, cast the RHS right before the setcc
1593 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1594 InsertNewInstBefore(cast<Instruction>(Op1), I);
1596 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1599 // Handle the special case of: setcc (cast bool to X), <cst>
1600 // This comes up when you have code like
1603 // For generality, we handle any zero-extension of any operand comparison
1605 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1606 const Type *SrcTy = CastOp0->getType();
1607 const Type *DestTy = Op0->getType();
1608 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1609 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1610 // Ok, we have an expansion of operand 0 into a new type. Get the
1611 // constant value, masink off bits which are not set in the RHS. These
1612 // could be set if the destination value is signed.
1613 uint64_t ConstVal = ConstantRHS->getRawValue();
1614 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1616 // If the constant we are comparing it with has high bits set, which
1617 // don't exist in the original value, the values could never be equal,
1618 // because the source would be zero extended.
1620 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1621 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1622 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1623 switch (I.getOpcode()) {
1624 default: assert(0 && "Unknown comparison type!");
1625 case Instruction::SetEQ:
1626 return ReplaceInstUsesWith(I, ConstantBool::False);
1627 case Instruction::SetNE:
1628 return ReplaceInstUsesWith(I, ConstantBool::True);
1629 case Instruction::SetLT:
1630 case Instruction::SetLE:
1631 if (DestTy->isSigned() && HasSignBit)
1632 return ReplaceInstUsesWith(I, ConstantBool::False);
1633 return ReplaceInstUsesWith(I, ConstantBool::True);
1634 case Instruction::SetGT:
1635 case Instruction::SetGE:
1636 if (DestTy->isSigned() && HasSignBit)
1637 return ReplaceInstUsesWith(I, ConstantBool::True);
1638 return ReplaceInstUsesWith(I, ConstantBool::False);
1642 // Otherwise, we can replace the setcc with a setcc of the smaller
1644 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1645 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1649 return Changed ? &I : 0;
1654 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1655 assert(I.getOperand(1)->getType() == Type::UByteTy);
1656 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1657 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1659 // shl X, 0 == X and shr X, 0 == X
1660 // shl 0, X == 0 and shr 0, X == 0
1661 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1662 Op0 == Constant::getNullValue(Op0->getType()))
1663 return ReplaceInstUsesWith(I, Op0);
1665 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1667 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1668 if (CSI->isAllOnesValue())
1669 return ReplaceInstUsesWith(I, CSI);
1671 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1672 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1673 // of a signed value.
1675 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1676 if (CUI->getValue() >= TypeBits) {
1677 if (!Op0->getType()->isSigned() || isLeftShift)
1678 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1680 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
1685 // ((X*C1) << C2) == (X * (C1 << C2))
1686 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1687 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1688 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1689 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1690 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1693 // If the operand is an bitwise operator with a constant RHS, and the
1694 // shift is the only use, we can pull it out of the shift.
1695 if (Op0->hasOneUse())
1696 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1697 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1698 bool isValid = true; // Valid only for And, Or, Xor
1699 bool highBitSet = false; // Transform if high bit of constant set?
1701 switch (Op0BO->getOpcode()) {
1702 default: isValid = false; break; // Do not perform transform!
1703 case Instruction::Or:
1704 case Instruction::Xor:
1707 case Instruction::And:
1712 // If this is a signed shift right, and the high bit is modified
1713 // by the logical operation, do not perform the transformation.
1714 // The highBitSet boolean indicates the value of the high bit of
1715 // the constant which would cause it to be modified for this
1718 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1719 uint64_t Val = Op0C->getRawValue();
1720 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1724 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1726 Instruction *NewShift =
1727 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1730 InsertNewInstBefore(NewShift, I);
1732 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1737 // If this is a shift of a shift, see if we can fold the two together...
1738 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1739 if (ConstantUInt *ShiftAmt1C =
1740 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1741 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1742 unsigned ShiftAmt2 = CUI->getValue();
1744 // Check for (A << c1) << c2 and (A >> c1) >> c2
1745 if (I.getOpcode() == Op0SI->getOpcode()) {
1746 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1747 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
1748 Amt = Op0->getType()->getPrimitiveSize()*8;
1749 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1750 ConstantUInt::get(Type::UByteTy, Amt));
1753 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1754 // signed types, we can only support the (A >> c1) << c2 configuration,
1755 // because it can not turn an arbitrary bit of A into a sign bit.
1756 if (I.getType()->isUnsigned() || isLeftShift) {
1757 // Calculate bitmask for what gets shifted off the edge...
1758 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1760 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1762 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1765 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1766 C, Op0SI->getOperand(0)->getName()+".mask");
1767 InsertNewInstBefore(Mask, I);
1769 // Figure out what flavor of shift we should use...
1770 if (ShiftAmt1 == ShiftAmt2)
1771 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1772 else if (ShiftAmt1 < ShiftAmt2) {
1773 return new ShiftInst(I.getOpcode(), Mask,
1774 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1776 return new ShiftInst(Op0SI->getOpcode(), Mask,
1777 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1787 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1790 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1791 const Type *DstTy) {
1793 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1794 // are identical and the bits don't get reinterpreted (for example
1795 // int->float->int would not be allowed)
1796 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1799 // Allow free casting and conversion of sizes as long as the sign doesn't
1801 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1802 unsigned SrcSize = SrcTy->getPrimitiveSize();
1803 unsigned MidSize = MidTy->getPrimitiveSize();
1804 unsigned DstSize = DstTy->getPrimitiveSize();
1806 // Cases where we are monotonically decreasing the size of the type are
1807 // always ok, regardless of what sign changes are going on.
1809 if (SrcSize >= MidSize && MidSize >= DstSize)
1812 // Cases where the source and destination type are the same, but the middle
1813 // type is bigger are noops.
1815 if (SrcSize == DstSize && MidSize > SrcSize)
1818 // If we are monotonically growing, things are more complex.
1820 if (SrcSize <= MidSize && MidSize <= DstSize) {
1821 // We have eight combinations of signedness to worry about. Here's the
1823 static const int SignTable[8] = {
1824 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1825 1, // U U U Always ok
1826 1, // U U S Always ok
1827 3, // U S U Ok iff SrcSize != MidSize
1828 3, // U S S Ok iff SrcSize != MidSize
1829 0, // S U U Never ok
1830 2, // S U S Ok iff MidSize == DstSize
1831 1, // S S U Always ok
1832 1, // S S S Always ok
1835 // Choose an action based on the current entry of the signtable that this
1836 // cast of cast refers to...
1837 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1838 switch (SignTable[Row]) {
1839 case 0: return false; // Never ok
1840 case 1: return true; // Always ok
1841 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1842 case 3: // Ok iff SrcSize != MidSize
1843 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1844 default: assert(0 && "Bad entry in sign table!");
1849 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1850 // like: short -> ushort -> uint, because this can create wrong results if
1851 // the input short is negative!
1856 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1857 if (V->getType() == Ty || isa<Constant>(V)) return false;
1858 if (const CastInst *CI = dyn_cast<CastInst>(V))
1859 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1864 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1865 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1866 /// casts that are known to not do anything...
1868 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1869 Instruction *InsertBefore) {
1870 if (V->getType() == DestTy) return V;
1871 if (Constant *C = dyn_cast<Constant>(V))
1872 return ConstantExpr::getCast(C, DestTy);
1874 CastInst *CI = new CastInst(V, DestTy, V->getName());
1875 InsertNewInstBefore(CI, *InsertBefore);
1879 // CastInst simplification
1881 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1882 Value *Src = CI.getOperand(0);
1884 // If the user is casting a value to the same type, eliminate this cast
1886 if (CI.getType() == Src->getType())
1887 return ReplaceInstUsesWith(CI, Src);
1889 // If casting the result of another cast instruction, try to eliminate this
1892 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1893 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1894 CSrc->getType(), CI.getType())) {
1895 // This instruction now refers directly to the cast's src operand. This
1896 // has a good chance of making CSrc dead.
1897 CI.setOperand(0, CSrc->getOperand(0));
1901 // If this is an A->B->A cast, and we are dealing with integral types, try
1902 // to convert this into a logical 'and' instruction.
1904 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1905 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1906 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1907 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1908 assert(CSrc->getType() != Type::ULongTy &&
1909 "Cannot have type bigger than ulong!");
1910 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1911 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1912 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1917 // If casting the result of a getelementptr instruction with no offset, turn
1918 // this into a cast of the original pointer!
1920 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1921 bool AllZeroOperands = true;
1922 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1923 if (!isa<Constant>(GEP->getOperand(i)) ||
1924 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1925 AllZeroOperands = false;
1928 if (AllZeroOperands) {
1929 CI.setOperand(0, GEP->getOperand(0));
1934 // If we are casting a malloc or alloca to a pointer to a type of the same
1935 // size, rewrite the allocation instruction to allocate the "right" type.
1937 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1938 if (AI->hasOneUse() && !AI->isArrayAllocation())
1939 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1940 // Get the type really allocated and the type casted to...
1941 const Type *AllocElTy = AI->getAllocatedType();
1942 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1943 const Type *CastElTy = PTy->getElementType();
1944 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1946 // If the allocation is for an even multiple of the cast type size
1947 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1948 Value *Amt = ConstantUInt::get(Type::UIntTy,
1949 AllocElTySize/CastElTySize);
1950 std::string Name = AI->getName(); AI->setName("");
1951 AllocationInst *New;
1952 if (isa<MallocInst>(AI))
1953 New = new MallocInst(CastElTy, Amt, Name);
1955 New = new AllocaInst(CastElTy, Amt, Name);
1956 InsertNewInstBefore(New, CI);
1957 return ReplaceInstUsesWith(CI, New);
1961 // If the source value is an instruction with only this use, we can attempt to
1962 // propagate the cast into the instruction. Also, only handle integral types
1964 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1965 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1966 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1967 const Type *DestTy = CI.getType();
1968 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1969 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1971 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1972 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1974 switch (SrcI->getOpcode()) {
1975 case Instruction::Add:
1976 case Instruction::Mul:
1977 case Instruction::And:
1978 case Instruction::Or:
1979 case Instruction::Xor:
1980 // If we are discarding information, or just changing the sign, rewrite.
1981 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1982 // Don't insert two casts if they cannot be eliminated. We allow two
1983 // casts to be inserted if the sizes are the same. This could only be
1984 // converting signedness, which is a noop.
1985 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1986 !ValueRequiresCast(Op0, DestTy)) {
1987 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1988 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1989 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1990 ->getOpcode(), Op0c, Op1c);
1994 case Instruction::Shl:
1995 // Allow changing the sign of the source operand. Do not allow changing
1996 // the size of the shift, UNLESS the shift amount is a constant. We
1997 // mush not change variable sized shifts to a smaller size, because it
1998 // is undefined to shift more bits out than exist in the value.
1999 if (DestBitSize == SrcBitSize ||
2000 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
2001 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2002 return new ShiftInst(Instruction::Shl, Op0c, Op1);
2011 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
2012 Value *CondVal = SI.getCondition();
2013 Value *TrueVal = SI.getTrueValue();
2014 Value *FalseVal = SI.getFalseValue();
2016 // select true, X, Y -> X
2017 // select false, X, Y -> Y
2018 if (ConstantBool *C = dyn_cast<ConstantBool>(CondVal))
2019 if (C == ConstantBool::True)
2020 return ReplaceInstUsesWith(SI, TrueVal);
2022 assert(C == ConstantBool::False);
2023 return ReplaceInstUsesWith(SI, FalseVal);
2026 // select C, X, X -> X
2027 if (TrueVal == FalseVal)
2028 return ReplaceInstUsesWith(SI, TrueVal);
2030 if (SI.getType() == Type::BoolTy)
2031 if (ConstantBool *C = dyn_cast<ConstantBool>(TrueVal)) {
2032 if (C == ConstantBool::True) {
2033 // Change: A = select B, true, C --> A = or B, C
2034 return BinaryOperator::create(Instruction::Or, CondVal, FalseVal);
2036 // Change: A = select B, false, C --> A = and !B, C
2038 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2039 "not."+CondVal->getName()), SI);
2040 return BinaryOperator::create(Instruction::And, NotCond, FalseVal);
2042 } else if (ConstantBool *C = dyn_cast<ConstantBool>(FalseVal)) {
2043 if (C == ConstantBool::False) {
2044 // Change: A = select B, C, false --> A = and B, C
2045 return BinaryOperator::create(Instruction::And, CondVal, TrueVal);
2047 // Change: A = select B, C, true --> A = or !B, C
2049 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2050 "not."+CondVal->getName()), SI);
2051 return BinaryOperator::create(Instruction::Or, NotCond, TrueVal);
2055 // Selecting between two constants?
2056 if (Constant *TrueValC = dyn_cast<Constant>(TrueVal))
2057 if (Constant *FalseValC = dyn_cast<Constant>(FalseVal)) {
2058 // If the true constant is a 1 and the false is a zero, turn this into a
2060 if (FalseValC->isNullValue() && isa<ConstantInt>(TrueValC) &&
2061 cast<ConstantInt>(TrueValC)->getRawValue() == 1)
2062 return new CastInst(CondVal, SI.getType());
2069 // CallInst simplification
2071 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
2072 // Intrinsics cannot occur in an invoke, so handle them here instead of in
2074 if (Function *F = CI.getCalledFunction())
2075 switch (F->getIntrinsicID()) {
2076 case Intrinsic::memmove:
2077 case Intrinsic::memcpy:
2078 case Intrinsic::memset:
2079 // memmove/cpy/set of zero bytes is a noop.
2080 if (Constant *NumBytes = dyn_cast<Constant>(CI.getOperand(3))) {
2081 if (NumBytes->isNullValue())
2082 return EraseInstFromFunction(CI);
2089 return visitCallSite(&CI);
2092 // InvokeInst simplification
2094 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
2095 return visitCallSite(&II);
2098 // visitCallSite - Improvements for call and invoke instructions.
2100 Instruction *InstCombiner::visitCallSite(CallSite CS) {
2101 bool Changed = false;
2103 // If the callee is a constexpr cast of a function, attempt to move the cast
2104 // to the arguments of the call/invoke.
2105 if (transformConstExprCastCall(CS)) return 0;
2107 Value *Callee = CS.getCalledValue();
2108 const PointerType *PTy = cast<PointerType>(Callee->getType());
2109 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
2110 if (FTy->isVarArg()) {
2111 // See if we can optimize any arguments passed through the varargs area of
2113 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
2114 E = CS.arg_end(); I != E; ++I)
2115 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
2116 // If this cast does not effect the value passed through the varargs
2117 // area, we can eliminate the use of the cast.
2118 Value *Op = CI->getOperand(0);
2119 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
2126 return Changed ? CS.getInstruction() : 0;
2129 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
2130 // attempt to move the cast to the arguments of the call/invoke.
2132 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
2133 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
2134 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
2135 if (CE->getOpcode() != Instruction::Cast ||
2136 !isa<ConstantPointerRef>(CE->getOperand(0)))
2138 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
2139 if (!isa<Function>(CPR->getValue())) return false;
2140 Function *Callee = cast<Function>(CPR->getValue());
2141 Instruction *Caller = CS.getInstruction();
2143 // Okay, this is a cast from a function to a different type. Unless doing so
2144 // would cause a type conversion of one of our arguments, change this call to
2145 // be a direct call with arguments casted to the appropriate types.
2147 const FunctionType *FT = Callee->getFunctionType();
2148 const Type *OldRetTy = Caller->getType();
2150 // Check to see if we are changing the return type...
2151 if (OldRetTy != FT->getReturnType()) {
2152 if (Callee->isExternal() &&
2153 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
2154 !Caller->use_empty())
2155 return false; // Cannot transform this return value...
2157 // If the callsite is an invoke instruction, and the return value is used by
2158 // a PHI node in a successor, we cannot change the return type of the call
2159 // because there is no place to put the cast instruction (without breaking
2160 // the critical edge). Bail out in this case.
2161 if (!Caller->use_empty())
2162 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
2163 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
2165 if (PHINode *PN = dyn_cast<PHINode>(*UI))
2166 if (PN->getParent() == II->getNormalDest() ||
2167 PN->getParent() == II->getUnwindDest())
2171 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
2172 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
2174 CallSite::arg_iterator AI = CS.arg_begin();
2175 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
2176 const Type *ParamTy = FT->getParamType(i);
2177 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
2178 if (Callee->isExternal() && !isConvertible) return false;
2181 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
2182 Callee->isExternal())
2183 return false; // Do not delete arguments unless we have a function body...
2185 // Okay, we decided that this is a safe thing to do: go ahead and start
2186 // inserting cast instructions as necessary...
2187 std::vector<Value*> Args;
2188 Args.reserve(NumActualArgs);
2190 AI = CS.arg_begin();
2191 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
2192 const Type *ParamTy = FT->getParamType(i);
2193 if ((*AI)->getType() == ParamTy) {
2194 Args.push_back(*AI);
2196 Args.push_back(InsertNewInstBefore(new CastInst(*AI, ParamTy, "tmp"),
2201 // If the function takes more arguments than the call was taking, add them
2203 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
2204 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
2206 // If we are removing arguments to the function, emit an obnoxious warning...
2207 if (FT->getNumParams() < NumActualArgs)
2208 if (!FT->isVarArg()) {
2209 std::cerr << "WARNING: While resolving call to function '"
2210 << Callee->getName() << "' arguments were dropped!\n";
2212 // Add all of the arguments in their promoted form to the arg list...
2213 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
2214 const Type *PTy = getPromotedType((*AI)->getType());
2215 if (PTy != (*AI)->getType()) {
2216 // Must promote to pass through va_arg area!
2217 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
2218 InsertNewInstBefore(Cast, *Caller);
2219 Args.push_back(Cast);
2221 Args.push_back(*AI);
2226 if (FT->getReturnType() == Type::VoidTy)
2227 Caller->setName(""); // Void type should not have a name...
2230 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2231 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
2232 Args, Caller->getName(), Caller);
2234 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
2237 // Insert a cast of the return type as necessary...
2239 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
2240 if (NV->getType() != Type::VoidTy) {
2241 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
2243 // If this is an invoke instruction, we should insert it after the first
2244 // non-phi, instruction in the normal successor block.
2245 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2246 BasicBlock::iterator I = II->getNormalDest()->begin();
2247 while (isa<PHINode>(I)) ++I;
2248 InsertNewInstBefore(NC, *I);
2250 // Otherwise, it's a call, just insert cast right after the call instr
2251 InsertNewInstBefore(NC, *Caller);
2253 AddUsersToWorkList(*Caller);
2255 NV = Constant::getNullValue(Caller->getType());
2259 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
2260 Caller->replaceAllUsesWith(NV);
2261 Caller->getParent()->getInstList().erase(Caller);
2262 removeFromWorkList(Caller);
2268 // PHINode simplification
2270 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2271 if (Value *V = hasConstantValue(&PN))
2272 return ReplaceInstUsesWith(PN, V);
2274 // If the only user of this instruction is a cast instruction, and all of the
2275 // incoming values are constants, change this PHI to merge together the casted
2278 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2279 if (CI->getType() != PN.getType()) { // noop casts will be folded
2280 bool AllConstant = true;
2281 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2282 if (!isa<Constant>(PN.getIncomingValue(i))) {
2283 AllConstant = false;
2287 // Make a new PHI with all casted values.
2288 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2289 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2290 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2291 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2292 PN.getIncomingBlock(i));
2295 // Update the cast instruction.
2296 CI->setOperand(0, New);
2297 WorkList.push_back(CI); // revisit the cast instruction to fold.
2298 WorkList.push_back(New); // Make sure to revisit the new Phi
2299 return &PN; // PN is now dead!
2305 static Value *InsertSignExtendToPtrTy(Value *V, const Type *DTy,
2306 Instruction *InsertPoint,
2308 unsigned PS = IC->getTargetData().getPointerSize();
2309 const Type *VTy = V->getType();
2311 if (!VTy->isSigned() && VTy->getPrimitiveSize() < PS)
2312 // We must insert a cast to ensure we sign-extend.
2313 V = IC->InsertNewInstBefore(new CastInst(V, VTy->getSignedVersion(),
2314 V->getName()), *InsertPoint);
2315 return IC->InsertNewInstBefore(new CastInst(V, DTy, V->getName()),
2320 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2321 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2322 // If so, eliminate the noop.
2323 if (GEP.getNumOperands() == 1)
2324 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2326 bool HasZeroPointerIndex = false;
2327 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2328 HasZeroPointerIndex = C->isNullValue();
2330 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2331 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2333 // Eliminate unneeded casts for indices.
2334 bool MadeChange = false;
2335 gep_type_iterator GTI = gep_type_begin(GEP);
2336 for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI)
2337 if (isa<SequentialType>(*GTI)) {
2338 if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
2339 Value *Src = CI->getOperand(0);
2340 const Type *SrcTy = Src->getType();
2341 const Type *DestTy = CI->getType();
2342 if (Src->getType()->isInteger()) {
2343 if (SrcTy->getPrimitiveSize() == DestTy->getPrimitiveSize()) {
2344 // We can always eliminate a cast from ulong or long to the other.
2345 // We can always eliminate a cast from uint to int or the other on
2346 // 32-bit pointer platforms.
2347 if (DestTy->getPrimitiveSize() >= TD->getPointerSize()) {
2349 GEP.setOperand(i, Src);
2351 } else if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
2352 SrcTy->getPrimitiveSize() == 4) {
2353 // We can always eliminate a cast from int to [u]long. We can
2354 // eliminate a cast from uint to [u]long iff the target is a 32-bit
2356 if (SrcTy->isSigned() ||
2357 SrcTy->getPrimitiveSize() >= TD->getPointerSize()) {
2359 GEP.setOperand(i, Src);
2364 // If we are using a wider index than needed for this platform, shrink it
2365 // to what we need. If the incoming value needs a cast instruction,
2366 // insert it. This explicit cast can make subsequent optimizations more
2368 Value *Op = GEP.getOperand(i);
2369 if (Op->getType()->getPrimitiveSize() > TD->getPointerSize())
2370 if (!isa<Constant>(Op)) {
2371 Op = InsertNewInstBefore(new CastInst(Op, TD->getIntPtrType(),
2372 Op->getName()), GEP);
2373 GEP.setOperand(i, Op);
2377 if (MadeChange) return &GEP;
2379 // Combine Indices - If the source pointer to this getelementptr instruction
2380 // is a getelementptr instruction, combine the indices of the two
2381 // getelementptr instructions into a single instruction.
2383 std::vector<Value*> SrcGEPOperands;
2384 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
2385 SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
2386 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2387 if (CE->getOpcode() == Instruction::GetElementPtr)
2388 SrcGEPOperands.assign(CE->op_begin(), CE->op_end());
2391 if (!SrcGEPOperands.empty()) {
2392 std::vector<Value *> Indices;
2394 // Can we combine the two pointer arithmetics offsets?
2395 if (SrcGEPOperands.size() == 2 && isa<Constant>(SrcGEPOperands[1]) &&
2396 isa<Constant>(GEP.getOperand(1))) {
2397 Constant *SGC = cast<Constant>(SrcGEPOperands[1]);
2398 Constant *GC = cast<Constant>(GEP.getOperand(1));
2399 if (SGC->getType() != GC->getType()) {
2400 SGC = ConstantExpr::getSignExtend(SGC, Type::LongTy);
2401 GC = ConstantExpr::getSignExtend(GC, Type::LongTy);
2404 // Replace: gep (gep %P, long C1), long C2, ...
2405 // With: gep %P, long (C1+C2), ...
2406 GEP.setOperand(0, SrcGEPOperands[0]);
2407 GEP.setOperand(1, ConstantExpr::getAdd(SGC, GC));
2408 if (Instruction *I = dyn_cast<Instruction>(GEP.getOperand(0)))
2409 AddUsersToWorkList(*I); // Reduce use count of Src
2411 } else if (SrcGEPOperands.size() == 2) {
2412 // Replace: gep (gep %P, long B), long A, ...
2413 // With: T = long A+B; gep %P, T, ...
2415 // Note that if our source is a gep chain itself that we wait for that
2416 // chain to be resolved before we perform this transformation. This
2417 // avoids us creating a TON of code in some cases.
2419 if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
2420 cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
2421 return 0; // Wait until our source is folded to completion.
2423 Value *Sum, *SO1 = SrcGEPOperands[1], *GO1 = GEP.getOperand(1);
2424 if (SO1 == Constant::getNullValue(SO1->getType())) {
2426 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
2429 // If they aren't the same type, convert both to an integer of the
2430 // target's pointer size.
2431 if (SO1->getType() != GO1->getType()) {
2432 if (Constant *SO1C = dyn_cast<Constant>(SO1)) {
2433 SO1 = ConstantExpr::getCast(SO1C, GO1->getType());
2434 } else if (Constant *GO1C = dyn_cast<Constant>(GO1)) {
2435 GO1 = ConstantExpr::getCast(GO1C, SO1->getType());
2437 unsigned PS = TD->getPointerSize();
2439 if (SO1->getType()->getPrimitiveSize() == PS) {
2440 // Convert GO1 to SO1's type.
2441 GO1 = InsertSignExtendToPtrTy(GO1, SO1->getType(), &GEP, this);
2443 } else if (GO1->getType()->getPrimitiveSize() == PS) {
2444 // Convert SO1 to GO1's type.
2445 SO1 = InsertSignExtendToPtrTy(SO1, GO1->getType(), &GEP, this);
2447 const Type *PT = TD->getIntPtrType();
2448 SO1 = InsertSignExtendToPtrTy(SO1, PT, &GEP, this);
2449 GO1 = InsertSignExtendToPtrTy(GO1, PT, &GEP, this);
2453 Sum = BinaryOperator::create(Instruction::Add, SO1, GO1,
2454 GEP.getOperand(0)->getName()+".sum", &GEP);
2455 WorkList.push_back(cast<Instruction>(Sum));
2457 GEP.setOperand(0, SrcGEPOperands[0]);
2458 GEP.setOperand(1, Sum);
2460 } else if (isa<Constant>(*GEP.idx_begin()) &&
2461 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
2462 SrcGEPOperands.size() != 1) {
2463 // Otherwise we can do the fold if the first index of the GEP is a zero
2464 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2465 SrcGEPOperands.end());
2466 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2467 } else if (SrcGEPOperands.back() ==
2468 Constant::getNullValue(SrcGEPOperands.back()->getType())) {
2469 // We have to check to make sure this really is an ARRAY index we are
2470 // ending up with, not a struct index.
2471 generic_gep_type_iterator<std::vector<Value*>::iterator>
2472 GTI = gep_type_begin(SrcGEPOperands[0]->getType(),
2473 SrcGEPOperands.begin()+1, SrcGEPOperands.end());
2474 std::advance(GTI, SrcGEPOperands.size()-2);
2475 if (isa<SequentialType>(*GTI)) {
2476 // If the src gep ends with a constant array index, merge this get into
2477 // it, even if we have a non-zero array index.
2478 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2479 SrcGEPOperands.end()-1);
2480 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
2484 if (!Indices.empty())
2485 return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
2487 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
2488 // GEP of global variable. If all of the indices for this GEP are
2489 // constants, we can promote this to a constexpr instead of an instruction.
2491 // Scan for nonconstants...
2492 std::vector<Constant*> Indices;
2493 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2494 for (; I != E && isa<Constant>(*I); ++I)
2495 Indices.push_back(cast<Constant>(*I));
2497 if (I == E) { // If they are all constants...
2499 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2501 // Replace all uses of the GEP with the new constexpr...
2502 return ReplaceInstUsesWith(GEP, CE);
2504 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2505 if (CE->getOpcode() == Instruction::Cast) {
2506 if (HasZeroPointerIndex) {
2507 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2508 // into : GEP [10 x ubyte]* X, long 0, ...
2510 // This occurs when the program declares an array extern like "int X[];"
2512 Constant *X = CE->getOperand(0);
2513 const PointerType *CPTy = cast<PointerType>(CE->getType());
2514 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2515 if (const ArrayType *XATy =
2516 dyn_cast<ArrayType>(XTy->getElementType()))
2517 if (const ArrayType *CATy =
2518 dyn_cast<ArrayType>(CPTy->getElementType()))
2519 if (CATy->getElementType() == XATy->getElementType()) {
2520 // At this point, we know that the cast source type is a pointer
2521 // to an array of the same type as the destination pointer
2522 // array. Because the array type is never stepped over (there
2523 // is a leading zero) we can fold the cast into this GEP.
2524 GEP.setOperand(0, X);
2534 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2535 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2536 if (AI.isArrayAllocation()) // Check C != 1
2537 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2538 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2539 AllocationInst *New = 0;
2541 // Create and insert the replacement instruction...
2542 if (isa<MallocInst>(AI))
2543 New = new MallocInst(NewTy, 0, AI.getName());
2545 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2546 New = new AllocaInst(NewTy, 0, AI.getName());
2549 InsertNewInstBefore(New, AI);
2551 // Scan to the end of the allocation instructions, to skip over a block of
2552 // allocas if possible...
2554 BasicBlock::iterator It = New;
2555 while (isa<AllocationInst>(*It)) ++It;
2557 // Now that I is pointing to the first non-allocation-inst in the block,
2558 // insert our getelementptr instruction...
2560 std::vector<Value*> Idx(2, Constant::getNullValue(Type::IntTy));
2561 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2563 // Now make everything use the getelementptr instead of the original
2565 return ReplaceInstUsesWith(AI, V);
2568 // If alloca'ing a zero byte object, replace the alloca with a null pointer.
2569 // Note that we only do this for alloca's, because malloc should allocate and
2570 // return a unique pointer, even for a zero byte allocation.
2571 if (isa<AllocaInst>(AI) && TD->getTypeSize(AI.getAllocatedType()) == 0)
2572 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
2577 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2578 Value *Op = FI.getOperand(0);
2580 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2581 if (CastInst *CI = dyn_cast<CastInst>(Op))
2582 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2583 FI.setOperand(0, CI->getOperand(0));
2587 // If we have 'free null' delete the instruction. This can happen in stl code
2588 // when lots of inlining happens.
2589 if (isa<ConstantPointerNull>(Op))
2590 return EraseInstFromFunction(FI);
2596 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2597 /// constantexpr, return the constant value being addressed by the constant
2598 /// expression, or null if something is funny.
2600 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2601 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
2602 return 0; // Do not allow stepping over the value!
2604 // Loop over all of the operands, tracking down which value we are
2606 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2607 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2608 ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
2609 if (CS == 0) return 0;
2610 if (CU->getValue() >= CS->getValues().size()) return 0;
2611 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2612 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2613 ConstantArray *CA = dyn_cast<ConstantArray>(C);
2614 if (CA == 0) return 0;
2615 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2616 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2622 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2623 Value *Op = LI.getOperand(0);
2624 if (LI.isVolatile()) return 0;
2626 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2627 Op = CPR->getValue();
2629 // Instcombine load (constant global) into the value loaded...
2630 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2631 if (GV->isConstant() && !GV->isExternal())
2632 return ReplaceInstUsesWith(LI, GV->getInitializer());
2634 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2635 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2636 if (CE->getOpcode() == Instruction::GetElementPtr)
2637 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2638 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2639 if (GV->isConstant() && !GV->isExternal())
2640 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2641 return ReplaceInstUsesWith(LI, V);
2646 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2647 // Change br (not X), label True, label False to: br X, label False, True
2648 if (BI.isConditional() && !isa<Constant>(BI.getCondition())) {
2649 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2650 BasicBlock *TrueDest = BI.getSuccessor(0);
2651 BasicBlock *FalseDest = BI.getSuccessor(1);
2652 // Swap Destinations and condition...
2654 BI.setSuccessor(0, FalseDest);
2655 BI.setSuccessor(1, TrueDest);
2657 } else if (SetCondInst *I = dyn_cast<SetCondInst>(BI.getCondition())) {
2658 // Cannonicalize setne -> seteq
2659 if ((I->getOpcode() == Instruction::SetNE ||
2660 I->getOpcode() == Instruction::SetLE ||
2661 I->getOpcode() == Instruction::SetGE) && I->hasOneUse()) {
2662 std::string Name = I->getName(); I->setName("");
2663 Instruction::BinaryOps NewOpcode =
2664 SetCondInst::getInverseCondition(I->getOpcode());
2665 Value *NewSCC = BinaryOperator::create(NewOpcode, I->getOperand(0),
2666 I->getOperand(1), Name, I);
2667 BasicBlock *TrueDest = BI.getSuccessor(0);
2668 BasicBlock *FalseDest = BI.getSuccessor(1);
2669 // Swap Destinations and condition...
2670 BI.setCondition(NewSCC);
2671 BI.setSuccessor(0, FalseDest);
2672 BI.setSuccessor(1, TrueDest);
2673 removeFromWorkList(I);
2674 I->getParent()->getInstList().erase(I);
2675 WorkList.push_back(cast<Instruction>(NewSCC));
2684 void InstCombiner::removeFromWorkList(Instruction *I) {
2685 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2689 bool InstCombiner::runOnFunction(Function &F) {
2690 bool Changed = false;
2691 TD = &getAnalysis<TargetData>();
2693 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2695 while (!WorkList.empty()) {
2696 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2697 WorkList.pop_back();
2699 // Check to see if we can DCE or ConstantPropagate the instruction...
2700 // Check to see if we can DIE the instruction...
2701 if (isInstructionTriviallyDead(I)) {
2702 // Add operands to the worklist...
2703 if (I->getNumOperands() < 4)
2704 AddUsesToWorkList(*I);
2707 I->getParent()->getInstList().erase(I);
2708 removeFromWorkList(I);
2712 // Instruction isn't dead, see if we can constant propagate it...
2713 if (Constant *C = ConstantFoldInstruction(I)) {
2714 // Add operands to the worklist...
2715 AddUsesToWorkList(*I);
2716 ReplaceInstUsesWith(*I, C);
2719 I->getParent()->getInstList().erase(I);
2720 removeFromWorkList(I);
2724 // Check to see if any of the operands of this instruction are a
2725 // ConstantPointerRef. Since they sneak in all over the place and inhibit
2726 // optimization, we want to strip them out unconditionally!
2727 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2728 if (ConstantPointerRef *CPR =
2729 dyn_cast<ConstantPointerRef>(I->getOperand(i))) {
2730 I->setOperand(i, CPR->getValue());
2734 // Now that we have an instruction, try combining it to simplify it...
2735 if (Instruction *Result = visit(*I)) {
2737 // Should we replace the old instruction with a new one?
2739 DEBUG(std::cerr << "IC: Old = " << *I
2740 << " New = " << *Result);
2742 // Instructions can end up on the worklist more than once. Make sure
2743 // we do not process an instruction that has been deleted.
2744 removeFromWorkList(I);
2746 // Move the name to the new instruction first...
2747 std::string OldName = I->getName(); I->setName("");
2748 Result->setName(OldName);
2750 // Insert the new instruction into the basic block...
2751 BasicBlock *InstParent = I->getParent();
2752 InstParent->getInstList().insert(I, Result);
2754 // Everything uses the new instruction now...
2755 I->replaceAllUsesWith(Result);
2757 // Erase the old instruction.
2758 InstParent->getInstList().erase(I);
2760 DEBUG(std::cerr << "IC: MOD = " << *I);
2762 BasicBlock::iterator II = I;
2764 // If the instruction was modified, it's possible that it is now dead.
2765 // if so, remove it.
2766 if (dceInstruction(II)) {
2767 // Instructions may end up in the worklist more than once. Erase them
2769 removeFromWorkList(I);
2775 WorkList.push_back(Result);
2776 AddUsersToWorkList(*Result);
2785 Pass *llvm::createInstructionCombiningPass() {
2786 return new InstCombiner();