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 #include "llvm/Transforms/Scalar.h"
37 #include "llvm/Instructions.h"
38 #include "llvm/Intrinsics.h"
39 #include "llvm/Pass.h"
40 #include "llvm/Constants.h"
41 #include "llvm/DerivedTypes.h"
42 #include "llvm/GlobalVariable.h"
43 #include "llvm/Target/TargetData.h"
44 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
45 #include "llvm/Transforms/Utils/Local.h"
46 #include "llvm/Support/InstIterator.h"
47 #include "llvm/Support/InstVisitor.h"
48 #include "llvm/Support/CallSite.h"
49 #include "Support/Statistic.h"
54 Statistic<> NumCombined ("instcombine", "Number of insts combined");
55 Statistic<> NumConstProp("instcombine", "Number of constant folds");
56 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
58 class InstCombiner : public FunctionPass,
59 public InstVisitor<InstCombiner, Instruction*> {
60 // Worklist of all of the instructions that need to be simplified.
61 std::vector<Instruction*> WorkList;
64 /// AddUsersToWorkList - When an instruction is simplified, add all users of
65 /// the instruction to the work lists because they might get more simplified
68 void AddUsersToWorkList(Instruction &I) {
69 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
71 WorkList.push_back(cast<Instruction>(*UI));
74 /// AddUsesToWorkList - When an instruction is simplified, add operands to
75 /// the work lists because they might get more simplified now.
77 void AddUsesToWorkList(Instruction &I) {
78 for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
79 if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i)))
80 WorkList.push_back(Op);
83 // removeFromWorkList - remove all instances of I from the worklist.
84 void removeFromWorkList(Instruction *I);
86 virtual bool runOnFunction(Function &F);
88 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
89 AU.addRequired<TargetData>();
93 // Visitation implementation - Implement instruction combining for different
94 // instruction types. The semantics are as follows:
96 // null - No change was made
97 // I - Change was made, I is still valid, I may be dead though
98 // otherwise - Change was made, replace I with returned instruction
100 Instruction *visitAdd(BinaryOperator &I);
101 Instruction *visitSub(BinaryOperator &I);
102 Instruction *visitMul(BinaryOperator &I);
103 Instruction *visitDiv(BinaryOperator &I);
104 Instruction *visitRem(BinaryOperator &I);
105 Instruction *visitAnd(BinaryOperator &I);
106 Instruction *visitOr (BinaryOperator &I);
107 Instruction *visitXor(BinaryOperator &I);
108 Instruction *visitSetCondInst(BinaryOperator &I);
109 Instruction *visitShiftInst(ShiftInst &I);
110 Instruction *visitCastInst(CastInst &CI);
111 Instruction *visitSelectInst(SelectInst &CI);
112 Instruction *visitCallInst(CallInst &CI);
113 Instruction *visitInvokeInst(InvokeInst &II);
114 Instruction *visitPHINode(PHINode &PN);
115 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
116 Instruction *visitAllocationInst(AllocationInst &AI);
117 Instruction *visitFreeInst(FreeInst &FI);
118 Instruction *visitLoadInst(LoadInst &LI);
119 Instruction *visitBranchInst(BranchInst &BI);
121 // visitInstruction - Specify what to return for unhandled instructions...
122 Instruction *visitInstruction(Instruction &I) { return 0; }
125 Instruction *visitCallSite(CallSite CS);
126 bool transformConstExprCastCall(CallSite CS);
128 // InsertNewInstBefore - insert an instruction New before instruction Old
129 // in the program. Add the new instruction to the worklist.
131 Value *InsertNewInstBefore(Instruction *New, Instruction &Old) {
132 assert(New && New->getParent() == 0 &&
133 "New instruction already inserted into a basic block!");
134 BasicBlock *BB = Old.getParent();
135 BB->getInstList().insert(&Old, New); // Insert inst
136 WorkList.push_back(New); // Add to worklist
141 // ReplaceInstUsesWith - This method is to be used when an instruction is
142 // found to be dead, replacable with another preexisting expression. Here
143 // we add all uses of I to the worklist, replace all uses of I with the new
144 // value, then return I, so that the inst combiner will know that I was
147 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
148 AddUsersToWorkList(I); // Add all modified instrs to worklist
149 I.replaceAllUsesWith(V);
153 // EraseInstFromFunction - When dealing with an instruction that has side
154 // effects or produces a void value, we can't rely on DCE to delete the
155 // instruction. Instead, visit methods should return the value returned by
157 Instruction *EraseInstFromFunction(Instruction &I) {
158 assert(I.use_empty() && "Cannot erase instruction that is used!");
159 AddUsesToWorkList(I);
160 removeFromWorkList(&I);
161 I.getParent()->getInstList().erase(&I);
162 return 0; // Don't do anything with FI
167 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
168 /// InsertBefore instruction. This is specialized a bit to avoid inserting
169 /// casts that are known to not do anything...
171 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
172 Instruction *InsertBefore);
174 // SimplifyCommutative - This performs a few simplifications for commutative
176 bool SimplifyCommutative(BinaryOperator &I);
178 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
179 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
182 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
185 // getComplexity: Assign a complexity or rank value to LLVM Values...
186 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
187 static unsigned getComplexity(Value *V) {
188 if (isa<Instruction>(V)) {
189 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
193 if (isa<Argument>(V)) return 2;
194 return isa<Constant>(V) ? 0 : 1;
197 // isOnlyUse - Return true if this instruction will be deleted if we stop using
199 static bool isOnlyUse(Value *V) {
200 return V->hasOneUse() || isa<Constant>(V);
203 // getSignedIntegralType - Given an unsigned integral type, return the signed
204 // version of it that has the same size.
205 static const Type *getSignedIntegralType(const Type *Ty) {
206 switch (Ty->getPrimitiveID()) {
207 default: assert(0 && "Invalid unsigned integer type!"); abort();
208 case Type::UByteTyID: return Type::SByteTy;
209 case Type::UShortTyID: return Type::ShortTy;
210 case Type::UIntTyID: return Type::IntTy;
211 case Type::ULongTyID: return Type::LongTy;
215 // getUnsignedIntegralType - Given an signed integral type, return the unsigned
216 // version of it that has the same size.
217 static const Type *getUnsignedIntegralType(const Type *Ty) {
218 switch (Ty->getPrimitiveID()) {
219 default: assert(0 && "Invalid signed integer type!"); abort();
220 case Type::SByteTyID: return Type::UByteTy;
221 case Type::ShortTyID: return Type::UShortTy;
222 case Type::IntTyID: return Type::UIntTy;
223 case Type::LongTyID: return Type::ULongTy;
227 // getPromotedType - Return the specified type promoted as it would be to pass
228 // though a va_arg area...
229 static const Type *getPromotedType(const Type *Ty) {
230 switch (Ty->getPrimitiveID()) {
231 case Type::SByteTyID:
232 case Type::ShortTyID: return Type::IntTy;
233 case Type::UByteTyID:
234 case Type::UShortTyID: return Type::UIntTy;
235 case Type::FloatTyID: return Type::DoubleTy;
240 // SimplifyCommutative - This performs a few simplifications for commutative
243 // 1. Order operands such that they are listed from right (least complex) to
244 // left (most complex). This puts constants before unary operators before
247 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
248 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
250 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
251 bool Changed = false;
252 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
253 Changed = !I.swapOperands();
255 if (!I.isAssociative()) return Changed;
256 Instruction::BinaryOps Opcode = I.getOpcode();
257 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
258 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
259 if (isa<Constant>(I.getOperand(1))) {
260 Constant *Folded = ConstantExpr::get(I.getOpcode(),
261 cast<Constant>(I.getOperand(1)),
262 cast<Constant>(Op->getOperand(1)));
263 I.setOperand(0, Op->getOperand(0));
264 I.setOperand(1, Folded);
266 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
267 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
268 isOnlyUse(Op) && isOnlyUse(Op1)) {
269 Constant *C1 = cast<Constant>(Op->getOperand(1));
270 Constant *C2 = cast<Constant>(Op1->getOperand(1));
272 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
273 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
274 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
277 WorkList.push_back(New);
278 I.setOperand(0, New);
279 I.setOperand(1, Folded);
286 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
287 // if the LHS is a constant zero (which is the 'negate' form).
289 static inline Value *dyn_castNegVal(Value *V) {
290 if (BinaryOperator::isNeg(V))
291 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
293 // Constants can be considered to be negated values if they can be folded...
294 if (Constant *C = dyn_cast<Constant>(V))
295 return ConstantExpr::get(Instruction::Sub,
296 Constant::getNullValue(V->getType()), C);
300 static Constant *NotConstant(Constant *C) {
301 return ConstantExpr::get(Instruction::Xor, C,
302 ConstantIntegral::getAllOnesValue(C->getType()));
305 static inline Value *dyn_castNotVal(Value *V) {
306 if (BinaryOperator::isNot(V))
307 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
309 // Constants can be considered to be not'ed values...
310 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
311 return NotConstant(C);
315 // dyn_castFoldableMul - If this value is a multiply that can be folded into
316 // other computations (because it has a constant operand), return the
317 // non-constant operand of the multiply.
319 static inline Value *dyn_castFoldableMul(Value *V) {
320 if (V->hasOneUse() && V->getType()->isInteger())
321 if (Instruction *I = dyn_cast<Instruction>(V))
322 if (I->getOpcode() == Instruction::Mul)
323 if (isa<Constant>(I->getOperand(1)))
324 return I->getOperand(0);
328 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
329 // a constant, return the constant being anded with.
331 template<class ValueType>
332 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
333 if (Instruction *I = dyn_cast<Instruction>(V))
334 if (I->getOpcode() == Instruction::And)
335 return dyn_cast<Constant>(I->getOperand(1));
337 // If this is a constant, it acts just like we were masking with it.
338 return dyn_cast<Constant>(V);
341 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
343 static unsigned Log2(uint64_t Val) {
344 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
347 if (Val & 1) return 0; // Multiple bits set?
355 /// AssociativeOpt - Perform an optimization on an associative operator. This
356 /// function is designed to check a chain of associative operators for a
357 /// potential to apply a certain optimization. Since the optimization may be
358 /// applicable if the expression was reassociated, this checks the chain, then
359 /// reassociates the expression as necessary to expose the optimization
360 /// opportunity. This makes use of a special Functor, which must define
361 /// 'shouldApply' and 'apply' methods.
363 template<typename Functor>
364 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
365 unsigned Opcode = Root.getOpcode();
366 Value *LHS = Root.getOperand(0);
368 // Quick check, see if the immediate LHS matches...
369 if (F.shouldApply(LHS))
370 return F.apply(Root);
372 // Otherwise, if the LHS is not of the same opcode as the root, return.
373 Instruction *LHSI = dyn_cast<Instruction>(LHS);
374 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
375 // Should we apply this transform to the RHS?
376 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
378 // If not to the RHS, check to see if we should apply to the LHS...
379 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
380 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
384 // If the functor wants to apply the optimization to the RHS of LHSI,
385 // reassociate the expression from ((? op A) op B) to (? op (A op B))
387 BasicBlock *BB = Root.getParent();
388 // All of the instructions have a single use and have no side-effects,
389 // because of this, we can pull them all into the current basic block.
390 if (LHSI->getParent() != BB) {
391 // Move all of the instructions from root to LHSI into the current
393 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
394 Instruction *LastUse = &Root;
395 while (TmpLHSI->getParent() == BB) {
397 TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
400 // Loop over all of the instructions in other blocks, moving them into
402 Value *TmpLHS = TmpLHSI;
404 TmpLHSI = cast<Instruction>(TmpLHS);
405 // Remove from current block...
406 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
407 // Insert before the last instruction...
408 BB->getInstList().insert(LastUse, TmpLHSI);
409 TmpLHS = TmpLHSI->getOperand(0);
410 } while (TmpLHSI != LHSI);
413 // Now all of the instructions are in the current basic block, go ahead
414 // and perform the reassociation.
415 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
417 // First move the selected RHS to the LHS of the root...
418 Root.setOperand(0, LHSI->getOperand(1));
420 // Make what used to be the LHS of the root be the user of the root...
421 Value *ExtraOperand = TmpLHSI->getOperand(1);
422 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
423 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
424 BB->getInstList().remove(&Root); // Remove root from the BB
425 BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
427 // Now propagate the ExtraOperand down the chain of instructions until we
429 while (TmpLHSI != LHSI) {
430 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
431 Value *NextOp = NextLHSI->getOperand(1);
432 NextLHSI->setOperand(1, ExtraOperand);
434 ExtraOperand = NextOp;
437 // Now that the instructions are reassociated, have the functor perform
438 // the transformation...
439 return F.apply(Root);
442 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
448 // AddRHS - Implements: X + X --> X << 1
451 AddRHS(Value *rhs) : RHS(rhs) {}
452 bool shouldApply(Value *LHS) const { return LHS == RHS; }
453 Instruction *apply(BinaryOperator &Add) const {
454 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
455 ConstantInt::get(Type::UByteTy, 1));
459 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
461 struct AddMaskingAnd {
463 AddMaskingAnd(Constant *c) : C2(c) {}
464 bool shouldApply(Value *LHS) const {
465 if (Constant *C1 = dyn_castMaskingAnd(LHS))
466 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
469 Instruction *apply(BinaryOperator &Add) const {
470 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
477 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
478 bool Changed = SimplifyCommutative(I);
479 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
482 if (!I.getType()->isFloatingPoint() && // -0 + +0 = +0, so it's not a noop
483 RHS == Constant::getNullValue(I.getType()))
484 return ReplaceInstUsesWith(I, LHS);
487 if (I.getType()->isInteger())
488 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
491 if (Value *V = dyn_castNegVal(LHS))
492 return BinaryOperator::create(Instruction::Sub, RHS, V);
495 if (!isa<Constant>(RHS))
496 if (Value *V = dyn_castNegVal(RHS))
497 return BinaryOperator::create(Instruction::Sub, LHS, V);
499 // X*C + X --> X * (C+1)
500 if (dyn_castFoldableMul(LHS) == RHS) {
502 ConstantExpr::get(Instruction::Add,
503 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
504 ConstantInt::get(I.getType(), 1));
505 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
508 // X + X*C --> X * (C+1)
509 if (dyn_castFoldableMul(RHS) == LHS) {
511 ConstantExpr::get(Instruction::Add,
512 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
513 ConstantInt::get(I.getType(), 1));
514 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
517 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
518 if (Constant *C2 = dyn_castMaskingAnd(RHS))
519 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
521 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
522 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
523 switch (ILHS->getOpcode()) {
524 case Instruction::Xor:
525 // ~X + C --> (C-1) - X
526 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
527 if (XorRHS->isAllOnesValue())
528 return BinaryOperator::create(Instruction::Sub,
529 ConstantExpr::get(Instruction::Sub,
530 CRHS, ConstantInt::get(I.getType(), 1)),
531 ILHS->getOperand(0));
538 return Changed ? &I : 0;
541 // isSignBit - Return true if the value represented by the constant only has the
542 // highest order bit set.
543 static bool isSignBit(ConstantInt *CI) {
544 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
545 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
548 static unsigned getTypeSizeInBits(const Type *Ty) {
549 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
552 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
553 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
555 if (Op0 == Op1) // sub X, X -> 0
556 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
558 // If this is a 'B = x-(-A)', change to B = x+A...
559 if (Value *V = dyn_castNegVal(Op1))
560 return BinaryOperator::create(Instruction::Add, Op0, V);
562 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
563 // Replace (-1 - A) with (~A)...
564 if (C->isAllOnesValue())
565 return BinaryOperator::createNot(Op1);
567 // C - ~X == X + (1+C)
568 if (BinaryOperator::isNot(Op1))
569 return BinaryOperator::create(Instruction::Add,
570 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
571 ConstantExpr::get(Instruction::Add, C,
572 ConstantInt::get(I.getType(), 1)));
573 // -((uint)X >> 31) -> ((int)X >> 31)
574 // -((int)X >> 31) -> ((uint)X >> 31)
575 if (C->isNullValue())
576 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op1))
577 if (SI->getOpcode() == Instruction::Shr)
578 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
580 if (C->getType()->isSigned())
581 NewTy = getUnsignedIntegralType(C->getType());
583 NewTy = getSignedIntegralType(C->getType());
584 // Check to see if we are shifting out everything but the sign bit.
585 if (CU->getValue() == C->getType()->getPrimitiveSize()*8-1) {
586 // Ok, the transformation is safe. Insert a cast of the incoming
587 // value, then the new shift, then the new cast.
588 Instruction *FirstCast = new CastInst(SI->getOperand(0), NewTy,
589 SI->getOperand(0)->getName());
590 Value *InV = InsertNewInstBefore(FirstCast, I);
591 Instruction *NewShift = new ShiftInst(Instruction::Shr, FirstCast,
593 InV = InsertNewInstBefore(NewShift, I);
594 return new CastInst(NewShift, I.getType());
599 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
600 if (Op1I->hasOneUse()) {
601 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
602 // is not used by anyone else...
604 if (Op1I->getOpcode() == Instruction::Sub &&
605 !Op1I->getType()->isFloatingPoint()) {
606 // Swap the two operands of the subexpr...
607 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
608 Op1I->setOperand(0, IIOp1);
609 Op1I->setOperand(1, IIOp0);
611 // Create the new top level add instruction...
612 return BinaryOperator::create(Instruction::Add, Op0, Op1);
615 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
617 if (Op1I->getOpcode() == Instruction::And &&
618 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
619 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
621 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
622 return BinaryOperator::create(Instruction::And, Op0, NewNot);
625 // X - X*C --> X * (1-C)
626 if (dyn_castFoldableMul(Op1I) == Op0) {
628 ConstantExpr::get(Instruction::Sub,
629 ConstantInt::get(I.getType(), 1),
630 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
631 assert(CP1 && "Couldn't constant fold 1-C?");
632 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
636 // X*C - X --> X * (C-1)
637 if (dyn_castFoldableMul(Op0) == Op1) {
639 ConstantExpr::get(Instruction::Sub,
640 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
641 ConstantInt::get(I.getType(), 1));
642 assert(CP1 && "Couldn't constant fold C - 1?");
643 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
649 /// isSignBitCheck - Given an exploded setcc instruction, return true if it is
650 /// really just returns true if the most significant (sign) bit is set.
651 static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
652 if (RHS->getType()->isSigned()) {
653 // True if source is LHS < 0 or LHS <= -1
654 return Opcode == Instruction::SetLT && RHS->isNullValue() ||
655 Opcode == Instruction::SetLE && RHS->isAllOnesValue();
657 ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
658 // True if source is LHS > 127 or LHS >= 128, where the constants depend on
659 // the size of the integer type.
660 if (Opcode == Instruction::SetGE)
661 return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1);
662 if (Opcode == Instruction::SetGT)
663 return RHSC->getValue() ==
664 (1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
669 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
670 bool Changed = SimplifyCommutative(I);
671 Value *Op0 = I.getOperand(0);
673 // Simplify mul instructions with a constant RHS...
674 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
675 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
677 // ((X << C1)*C2) == (X * (C2 << C1))
678 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
679 if (SI->getOpcode() == Instruction::Shl)
680 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
681 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
682 ConstantExpr::get(Instruction::Shl, CI, ShOp));
684 if (CI->isNullValue())
685 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
686 if (CI->equalsInt(1)) // X * 1 == X
687 return ReplaceInstUsesWith(I, Op0);
688 if (CI->isAllOnesValue()) // X * -1 == 0 - X
689 return BinaryOperator::createNeg(Op0, I.getName());
691 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
692 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
693 return new ShiftInst(Instruction::Shl, Op0,
694 ConstantUInt::get(Type::UByteTy, C));
696 ConstantFP *Op1F = cast<ConstantFP>(Op1);
697 if (Op1F->isNullValue())
698 return ReplaceInstUsesWith(I, Op1);
700 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
701 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
702 if (Op1F->getValue() == 1.0)
703 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
707 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
708 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
709 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
711 // If one of the operands of the multiply is a cast from a boolean value, then
712 // we know the bool is either zero or one, so this is a 'masking' multiply.
713 // See if we can simplify things based on how the boolean was originally
715 CastInst *BoolCast = 0;
716 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
717 if (CI->getOperand(0)->getType() == Type::BoolTy)
720 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
721 if (CI->getOperand(0)->getType() == Type::BoolTy)
724 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
725 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
726 const Type *SCOpTy = SCIOp0->getType();
728 // If the setcc is true iff the sign bit of X is set, then convert this
729 // multiply into a shift/and combination.
730 if (isa<ConstantInt>(SCIOp1) &&
731 isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
732 // Shift the X value right to turn it into "all signbits".
733 Constant *Amt = ConstantUInt::get(Type::UByteTy,
734 SCOpTy->getPrimitiveSize()*8-1);
735 if (SCIOp0->getType()->isUnsigned()) {
736 const Type *NewTy = getSignedIntegralType(SCIOp0->getType());
737 SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
738 SCIOp0->getName()), I);
742 InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
743 BoolCast->getOperand(0)->getName()+
746 // If the multiply type is not the same as the source type, sign extend
747 // or truncate to the multiply type.
748 if (I.getType() != V->getType())
749 V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
751 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
752 return BinaryOperator::create(Instruction::And, V, OtherOp);
757 return Changed ? &I : 0;
760 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
762 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
763 if (RHS->equalsInt(1))
764 return ReplaceInstUsesWith(I, I.getOperand(0));
766 // Check to see if this is an unsigned division with an exact power of 2,
767 // if so, convert to a right shift.
768 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
769 if (uint64_t Val = C->getValue()) // Don't break X / 0
770 if (uint64_t C = Log2(Val))
771 return new ShiftInst(Instruction::Shr, I.getOperand(0),
772 ConstantUInt::get(Type::UByteTy, C));
775 // 0 / X == 0, we don't need to preserve faults!
776 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
777 if (LHS->equalsInt(0))
778 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
784 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
785 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
786 if (RHS->equalsInt(1)) // X % 1 == 0
787 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
789 // Check to see if this is an unsigned remainder with an exact power of 2,
790 // if so, convert to a bitwise and.
791 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
792 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
794 return BinaryOperator::create(Instruction::And, I.getOperand(0),
795 ConstantUInt::get(I.getType(), Val-1));
798 // 0 % X == 0, we don't need to preserve faults!
799 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
800 if (LHS->equalsInt(0))
801 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
806 // isMaxValueMinusOne - return true if this is Max-1
807 static bool isMaxValueMinusOne(const ConstantInt *C) {
808 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
809 // Calculate -1 casted to the right type...
810 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
811 uint64_t Val = ~0ULL; // All ones
812 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
813 return CU->getValue() == Val-1;
816 const ConstantSInt *CS = cast<ConstantSInt>(C);
818 // Calculate 0111111111..11111
819 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
820 int64_t Val = INT64_MAX; // All ones
821 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
822 return CS->getValue() == Val-1;
825 // isMinValuePlusOne - return true if this is Min+1
826 static bool isMinValuePlusOne(const ConstantInt *C) {
827 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
828 return CU->getValue() == 1;
830 const ConstantSInt *CS = cast<ConstantSInt>(C);
832 // Calculate 1111111111000000000000
833 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
834 int64_t Val = -1; // All ones
835 Val <<= TypeBits-1; // Shift over to the right spot
836 return CS->getValue() == Val+1;
839 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
840 /// are carefully arranged to allow folding of expressions such as:
842 /// (A < B) | (A > B) --> (A != B)
844 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
845 /// represents that the comparison is true if A == B, and bit value '1' is true
848 static unsigned getSetCondCode(const SetCondInst *SCI) {
849 switch (SCI->getOpcode()) {
851 case Instruction::SetGT: return 1;
852 case Instruction::SetEQ: return 2;
853 case Instruction::SetGE: return 3;
854 case Instruction::SetLT: return 4;
855 case Instruction::SetNE: return 5;
856 case Instruction::SetLE: return 6;
859 assert(0 && "Invalid SetCC opcode!");
864 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
865 /// opcode and two operands into either a constant true or false, or a brand new
866 /// SetCC instruction.
867 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
869 case 0: return ConstantBool::False;
870 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
871 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
872 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
873 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
874 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
875 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
876 case 7: return ConstantBool::True;
877 default: assert(0 && "Illegal SetCCCode!"); return 0;
881 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
882 struct FoldSetCCLogical {
885 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
886 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
887 bool shouldApply(Value *V) const {
888 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
889 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
890 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
893 Instruction *apply(BinaryOperator &Log) const {
894 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
895 if (SCI->getOperand(0) != LHS) {
896 assert(SCI->getOperand(1) == LHS);
897 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
900 unsigned LHSCode = getSetCondCode(SCI);
901 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
903 switch (Log.getOpcode()) {
904 case Instruction::And: Code = LHSCode & RHSCode; break;
905 case Instruction::Or: Code = LHSCode | RHSCode; break;
906 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
907 default: assert(0 && "Illegal logical opcode!"); return 0;
910 Value *RV = getSetCCValue(Code, LHS, RHS);
911 if (Instruction *I = dyn_cast<Instruction>(RV))
913 // Otherwise, it's a constant boolean value...
914 return IC.ReplaceInstUsesWith(Log, RV);
919 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
920 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
921 // guaranteed to be either a shift instruction or a binary operator.
922 Instruction *InstCombiner::OptAndOp(Instruction *Op,
923 ConstantIntegral *OpRHS,
924 ConstantIntegral *AndRHS,
925 BinaryOperator &TheAnd) {
926 Value *X = Op->getOperand(0);
927 Constant *Together = 0;
928 if (!isa<ShiftInst>(Op))
929 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
931 switch (Op->getOpcode()) {
932 case Instruction::Xor:
933 if (Together->isNullValue()) {
934 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
935 return BinaryOperator::create(Instruction::And, X, AndRHS);
936 } else if (Op->hasOneUse()) {
937 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
938 std::string OpName = Op->getName(); Op->setName("");
939 Instruction *And = BinaryOperator::create(Instruction::And,
941 InsertNewInstBefore(And, TheAnd);
942 return BinaryOperator::create(Instruction::Xor, And, Together);
945 case Instruction::Or:
946 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
947 if (Together->isNullValue())
948 return BinaryOperator::create(Instruction::And, X, AndRHS);
950 if (Together == AndRHS) // (X | C) & C --> C
951 return ReplaceInstUsesWith(TheAnd, AndRHS);
953 if (Op->hasOneUse() && Together != OpRHS) {
954 // (X | C1) & C2 --> (X | (C1&C2)) & C2
955 std::string Op0Name = Op->getName(); Op->setName("");
956 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
958 InsertNewInstBefore(Or, TheAnd);
959 return BinaryOperator::create(Instruction::And, Or, AndRHS);
963 case Instruction::Add:
964 if (Op->hasOneUse()) {
965 // Adding a one to a single bit bit-field should be turned into an XOR
966 // of the bit. First thing to check is to see if this AND is with a
967 // single bit constant.
968 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
970 // Clear bits that are not part of the constant.
971 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
973 // If there is only one bit set...
974 if ((AndRHSV & (AndRHSV-1)) == 0) {
975 // Ok, at this point, we know that we are masking the result of the
976 // ADD down to exactly one bit. If the constant we are adding has
977 // no bits set below this bit, then we can eliminate the ADD.
978 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
980 // Check to see if any bits below the one bit set in AndRHSV are set.
981 if ((AddRHS & (AndRHSV-1)) == 0) {
982 // If not, the only thing that can effect the output of the AND is
983 // the bit specified by AndRHSV. If that bit is set, the effect of
984 // the XOR is to toggle the bit. If it is clear, then the ADD has
986 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
987 TheAnd.setOperand(0, X);
990 std::string Name = Op->getName(); Op->setName("");
991 // Pull the XOR out of the AND.
992 Instruction *NewAnd =
993 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
994 InsertNewInstBefore(NewAnd, TheAnd);
995 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
1002 case Instruction::Shl: {
1003 // We know that the AND will not produce any of the bits shifted in, so if
1004 // the anded constant includes them, clear them now!
1006 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1007 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1008 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
1010 TheAnd.setOperand(1, CI);
1015 case Instruction::Shr:
1016 // We know that the AND will not produce any of the bits shifted in, so if
1017 // the anded constant includes them, clear them now! This only applies to
1018 // unsigned shifts, because a signed shr may bring in set bits!
1020 if (AndRHS->getType()->isUnsigned()) {
1021 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1022 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1023 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
1025 TheAnd.setOperand(1, CI);
1035 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
1036 bool Changed = SimplifyCommutative(I);
1037 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1039 // and X, X = X and X, 0 == 0
1040 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1041 return ReplaceInstUsesWith(I, Op1);
1044 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1045 if (RHS->isAllOnesValue())
1046 return ReplaceInstUsesWith(I, Op0);
1048 // Optimize a variety of ((val OP C1) & C2) combinations...
1049 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
1050 Instruction *Op0I = cast<Instruction>(Op0);
1051 Value *X = Op0I->getOperand(0);
1052 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1053 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
1058 Value *Op0NotVal = dyn_castNotVal(Op0);
1059 Value *Op1NotVal = dyn_castNotVal(Op1);
1061 // (~A & ~B) == (~(A | B)) - Demorgan's Law
1062 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1063 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
1064 Op1NotVal,I.getName()+".demorgan");
1065 InsertNewInstBefore(Or, I);
1066 return BinaryOperator::createNot(Or);
1069 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1070 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1072 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1073 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1074 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1077 return Changed ? &I : 0;
1082 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1083 bool Changed = SimplifyCommutative(I);
1084 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1086 // or X, X = X or X, 0 == X
1087 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1088 return ReplaceInstUsesWith(I, Op0);
1091 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1092 if (RHS->isAllOnesValue())
1093 return ReplaceInstUsesWith(I, Op1);
1095 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1096 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1097 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
1098 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1099 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1100 Instruction *Or = BinaryOperator::create(Instruction::Or,
1101 Op0I->getOperand(0), RHS,
1103 InsertNewInstBefore(Or, I);
1104 return BinaryOperator::create(Instruction::And, Or,
1105 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
1108 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1109 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
1110 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1111 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1112 Instruction *Or = BinaryOperator::create(Instruction::Or,
1113 Op0I->getOperand(0), RHS,
1115 InsertNewInstBefore(Or, I);
1116 return BinaryOperator::create(Instruction::Xor, Or,
1117 ConstantExpr::get(Instruction::And, Op0CI,
1123 // (A & C1)|(A & C2) == A & (C1|C2)
1124 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
1125 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
1126 if (LHS->getOperand(0) == RHS->getOperand(0))
1127 if (Constant *C0 = dyn_castMaskingAnd(LHS))
1128 if (Constant *C1 = dyn_castMaskingAnd(RHS))
1129 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
1130 ConstantExpr::get(Instruction::Or, C0, C1));
1132 Value *Op0NotVal = dyn_castNotVal(Op0);
1133 Value *Op1NotVal = dyn_castNotVal(Op1);
1135 if (Op1 == Op0NotVal) // ~A | A == -1
1136 return ReplaceInstUsesWith(I,
1137 ConstantIntegral::getAllOnesValue(I.getType()));
1139 if (Op0 == Op1NotVal) // A | ~A == -1
1140 return ReplaceInstUsesWith(I,
1141 ConstantIntegral::getAllOnesValue(I.getType()));
1143 // (~A | ~B) == (~(A & B)) - Demorgan's Law
1144 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1145 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
1146 Op1NotVal,I.getName()+".demorgan",
1148 WorkList.push_back(And);
1149 return BinaryOperator::createNot(And);
1152 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1153 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1154 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1157 return Changed ? &I : 0;
1160 // XorSelf - Implements: X ^ X --> 0
1163 XorSelf(Value *rhs) : RHS(rhs) {}
1164 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1165 Instruction *apply(BinaryOperator &Xor) const {
1171 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1172 bool Changed = SimplifyCommutative(I);
1173 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1175 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1176 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1177 assert(Result == &I && "AssociativeOpt didn't work?");
1178 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1181 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1183 if (RHS->isNullValue())
1184 return ReplaceInstUsesWith(I, Op0);
1186 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1187 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1188 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1189 if (RHS == ConstantBool::True && SCI->hasOneUse())
1190 return new SetCondInst(SCI->getInverseCondition(),
1191 SCI->getOperand(0), SCI->getOperand(1));
1193 // ~(c-X) == X-c-1 == X+(-c-1)
1194 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1195 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1196 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1197 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1198 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1199 ConstantInt::get(I.getType(), 1));
1200 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1204 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1205 switch (Op0I->getOpcode()) {
1206 case Instruction::Add:
1207 // ~(X-c) --> (-c-1)-X
1208 if (RHS->isAllOnesValue()) {
1209 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1210 Constant::getNullValue(Op0CI->getType()), Op0CI);
1211 return BinaryOperator::create(Instruction::Sub,
1212 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1213 ConstantInt::get(I.getType(), 1)),
1214 Op0I->getOperand(0));
1217 case Instruction::And:
1218 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1219 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1220 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1222 case Instruction::Or:
1223 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1224 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1225 return BinaryOperator::create(Instruction::And, Op0,
1233 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1235 return ReplaceInstUsesWith(I,
1236 ConstantIntegral::getAllOnesValue(I.getType()));
1238 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1240 return ReplaceInstUsesWith(I,
1241 ConstantIntegral::getAllOnesValue(I.getType()));
1243 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1244 if (Op1I->getOpcode() == Instruction::Or) {
1245 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1246 cast<BinaryOperator>(Op1I)->swapOperands();
1248 std::swap(Op0, Op1);
1249 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1251 std::swap(Op0, Op1);
1253 } else if (Op1I->getOpcode() == Instruction::Xor) {
1254 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1255 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1256 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1257 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1260 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1261 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1262 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1263 cast<BinaryOperator>(Op0I)->swapOperands();
1264 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1265 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1266 WorkList.push_back(cast<Instruction>(NotB));
1267 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1270 } else if (Op0I->getOpcode() == Instruction::Xor) {
1271 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1272 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1273 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1274 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1277 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1278 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1279 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1280 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1281 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1283 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1284 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1285 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1288 return Changed ? &I : 0;
1291 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1292 static Constant *AddOne(ConstantInt *C) {
1293 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1294 ConstantInt::get(C->getType(), 1));
1295 assert(Result && "Constant folding integer addition failed!");
1298 static Constant *SubOne(ConstantInt *C) {
1299 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1300 ConstantInt::get(C->getType(), 1));
1301 assert(Result && "Constant folding integer addition failed!");
1305 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1306 // true when both operands are equal...
1308 static bool isTrueWhenEqual(Instruction &I) {
1309 return I.getOpcode() == Instruction::SetEQ ||
1310 I.getOpcode() == Instruction::SetGE ||
1311 I.getOpcode() == Instruction::SetLE;
1314 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1315 bool Changed = SimplifyCommutative(I);
1316 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1317 const Type *Ty = Op0->getType();
1321 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1323 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1324 if (isa<ConstantPointerNull>(Op1) &&
1325 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1326 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1329 // setcc's with boolean values can always be turned into bitwise operations
1330 if (Ty == Type::BoolTy) {
1331 // If this is <, >, or !=, we can change this into a simple xor instruction
1332 if (!isTrueWhenEqual(I))
1333 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1335 // Otherwise we need to make a temporary intermediate instruction and insert
1336 // it into the instruction stream. This is what we are after:
1338 // seteq bool %A, %B -> ~(A^B)
1339 // setle bool %A, %B -> ~A | B
1340 // setge bool %A, %B -> A | ~B
1342 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1343 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1345 InsertNewInstBefore(Xor, I);
1346 return BinaryOperator::createNot(Xor);
1349 // Handle the setXe cases...
1350 assert(I.getOpcode() == Instruction::SetGE ||
1351 I.getOpcode() == Instruction::SetLE);
1353 if (I.getOpcode() == Instruction::SetGE)
1354 std::swap(Op0, Op1); // Change setge -> setle
1356 // Now we just have the SetLE case.
1357 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1358 InsertNewInstBefore(Not, I);
1359 return BinaryOperator::create(Instruction::Or, Not, Op1);
1362 // Check to see if we are doing one of many comparisons against constant
1363 // integers at the end of their ranges...
1365 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1366 // Simplify seteq and setne instructions...
1367 if (I.getOpcode() == Instruction::SetEQ ||
1368 I.getOpcode() == Instruction::SetNE) {
1369 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1371 // If the first operand is (and|or|xor) with a constant, and the second
1372 // operand is a constant, simplify a bit.
1373 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1374 switch (BO->getOpcode()) {
1375 case Instruction::Add:
1376 if (CI->isNullValue()) {
1377 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1378 // efficiently invertible, or if the add has just this one use.
1379 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1380 if (Value *NegVal = dyn_castNegVal(BOp1))
1381 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1382 else if (Value *NegVal = dyn_castNegVal(BOp0))
1383 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1384 else if (BO->hasOneUse()) {
1385 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1387 InsertNewInstBefore(Neg, I);
1388 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1392 case Instruction::Xor:
1393 // For the xor case, we can xor two constants together, eliminating
1394 // the explicit xor.
1395 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1396 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1397 ConstantExpr::get(Instruction::Xor, CI, BOC));
1400 case Instruction::Sub:
1401 // Replace (([sub|xor] A, B) != 0) with (A != B)
1402 if (CI->isNullValue())
1403 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1407 case Instruction::Or:
1408 // If bits are being or'd in that are not present in the constant we
1409 // are comparing against, then the comparison could never succeed!
1410 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1411 Constant *NotCI = NotConstant(CI);
1412 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1413 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1417 case Instruction::And:
1418 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1419 // If bits are being compared against that are and'd out, then the
1420 // comparison can never succeed!
1421 if (!ConstantExpr::get(Instruction::And, CI,
1422 NotConstant(BOC))->isNullValue())
1423 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1425 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1426 // to be a signed value as appropriate.
1427 if (isSignBit(BOC)) {
1428 Value *X = BO->getOperand(0);
1429 // If 'X' is not signed, insert a cast now...
1430 if (!BOC->getType()->isSigned()) {
1431 const Type *DestTy = getSignedIntegralType(BOC->getType());
1432 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1433 InsertNewInstBefore(NewCI, I);
1436 return new SetCondInst(isSetNE ? Instruction::SetLT :
1437 Instruction::SetGE, X,
1438 Constant::getNullValue(X->getType()));
1444 } else { // Not a SetEQ/SetNE
1445 // If the LHS is a cast from an integral value of the same size,
1446 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
1447 Value *CastOp = Cast->getOperand(0);
1448 const Type *SrcTy = CastOp->getType();
1449 unsigned SrcTySize = SrcTy->getPrimitiveSize();
1450 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
1451 SrcTySize == Cast->getType()->getPrimitiveSize()) {
1452 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
1453 "Source and destination signednesses should differ!");
1454 if (Cast->getType()->isSigned()) {
1455 // If this is a signed comparison, check for comparisons in the
1456 // vicinity of zero.
1457 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
1459 return BinaryOperator::create(Instruction::SetGT, CastOp,
1460 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
1461 else if (I.getOpcode() == Instruction::SetGT &&
1462 cast<ConstantSInt>(CI)->getValue() == -1)
1463 // X > -1 => x < 128
1464 return BinaryOperator::create(Instruction::SetLT, CastOp,
1465 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
1467 ConstantUInt *CUI = cast<ConstantUInt>(CI);
1468 if (I.getOpcode() == Instruction::SetLT &&
1469 CUI->getValue() == 1ULL << (SrcTySize*8-1))
1470 // X < 128 => X > -1
1471 return BinaryOperator::create(Instruction::SetGT, CastOp,
1472 ConstantSInt::get(SrcTy, -1));
1473 else if (I.getOpcode() == Instruction::SetGT &&
1474 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
1476 return BinaryOperator::create(Instruction::SetLT, CastOp,
1477 Constant::getNullValue(SrcTy));
1483 // Check to see if we are comparing against the minimum or maximum value...
1484 if (CI->isMinValue()) {
1485 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1486 return ReplaceInstUsesWith(I, ConstantBool::False);
1487 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1488 return ReplaceInstUsesWith(I, ConstantBool::True);
1489 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1490 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1491 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1492 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1494 } else if (CI->isMaxValue()) {
1495 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1496 return ReplaceInstUsesWith(I, ConstantBool::False);
1497 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1498 return ReplaceInstUsesWith(I, ConstantBool::True);
1499 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1500 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1501 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1502 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1504 // Comparing against a value really close to min or max?
1505 } else if (isMinValuePlusOne(CI)) {
1506 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1507 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1508 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1509 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1511 } else if (isMaxValueMinusOne(CI)) {
1512 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1513 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1514 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1515 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1518 // If we still have a setle or setge instruction, turn it into the
1519 // appropriate setlt or setgt instruction. Since the border cases have
1520 // already been handled above, this requires little checking.
1522 if (I.getOpcode() == Instruction::SetLE)
1523 return BinaryOperator::create(Instruction::SetLT, Op0, AddOne(CI));
1524 if (I.getOpcode() == Instruction::SetGE)
1525 return BinaryOperator::create(Instruction::SetGT, Op0, SubOne(CI));
1528 // Test to see if the operands of the setcc are casted versions of other
1529 // values. If the cast can be stripped off both arguments, we do so now.
1530 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1531 Value *CastOp0 = CI->getOperand(0);
1532 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1533 !isa<Argument>(Op1) &&
1534 (I.getOpcode() == Instruction::SetEQ ||
1535 I.getOpcode() == Instruction::SetNE)) {
1536 // We keep moving the cast from the left operand over to the right
1537 // operand, where it can often be eliminated completely.
1540 // If operand #1 is a cast instruction, see if we can eliminate it as
1542 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1543 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1545 Op1 = CI2->getOperand(0);
1547 // If Op1 is a constant, we can fold the cast into the constant.
1548 if (Op1->getType() != Op0->getType())
1549 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1550 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1552 // Otherwise, cast the RHS right before the setcc
1553 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1554 InsertNewInstBefore(cast<Instruction>(Op1), I);
1556 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1559 // Handle the special case of: setcc (cast bool to X), <cst>
1560 // This comes up when you have code like
1563 // For generality, we handle any zero-extension of any operand comparison
1565 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1566 const Type *SrcTy = CastOp0->getType();
1567 const Type *DestTy = Op0->getType();
1568 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1569 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1570 // Ok, we have an expansion of operand 0 into a new type. Get the
1571 // constant value, masink off bits which are not set in the RHS. These
1572 // could be set if the destination value is signed.
1573 uint64_t ConstVal = ConstantRHS->getRawValue();
1574 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1576 // If the constant we are comparing it with has high bits set, which
1577 // don't exist in the original value, the values could never be equal,
1578 // because the source would be zero extended.
1580 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1581 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1582 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1583 switch (I.getOpcode()) {
1584 default: assert(0 && "Unknown comparison type!");
1585 case Instruction::SetEQ:
1586 return ReplaceInstUsesWith(I, ConstantBool::False);
1587 case Instruction::SetNE:
1588 return ReplaceInstUsesWith(I, ConstantBool::True);
1589 case Instruction::SetLT:
1590 case Instruction::SetLE:
1591 if (DestTy->isSigned() && HasSignBit)
1592 return ReplaceInstUsesWith(I, ConstantBool::False);
1593 return ReplaceInstUsesWith(I, ConstantBool::True);
1594 case Instruction::SetGT:
1595 case Instruction::SetGE:
1596 if (DestTy->isSigned() && HasSignBit)
1597 return ReplaceInstUsesWith(I, ConstantBool::True);
1598 return ReplaceInstUsesWith(I, ConstantBool::False);
1602 // Otherwise, we can replace the setcc with a setcc of the smaller
1604 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1605 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1609 return Changed ? &I : 0;
1614 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1615 assert(I.getOperand(1)->getType() == Type::UByteTy);
1616 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1617 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1619 // shl X, 0 == X and shr X, 0 == X
1620 // shl 0, X == 0 and shr 0, X == 0
1621 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1622 Op0 == Constant::getNullValue(Op0->getType()))
1623 return ReplaceInstUsesWith(I, Op0);
1625 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1627 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1628 if (CSI->isAllOnesValue())
1629 return ReplaceInstUsesWith(I, CSI);
1631 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1632 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1633 // of a signed value.
1635 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1636 if (CUI->getValue() >= TypeBits) {
1637 if (!Op0->getType()->isSigned() || isLeftShift)
1638 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1640 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
1645 // ((X*C1) << C2) == (X * (C1 << C2))
1646 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1647 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1648 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1649 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1650 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1653 // If the operand is an bitwise operator with a constant RHS, and the
1654 // shift is the only use, we can pull it out of the shift.
1655 if (Op0->hasOneUse())
1656 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1657 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1658 bool isValid = true; // Valid only for And, Or, Xor
1659 bool highBitSet = false; // Transform if high bit of constant set?
1661 switch (Op0BO->getOpcode()) {
1662 default: isValid = false; break; // Do not perform transform!
1663 case Instruction::Or:
1664 case Instruction::Xor:
1667 case Instruction::And:
1672 // If this is a signed shift right, and the high bit is modified
1673 // by the logical operation, do not perform the transformation.
1674 // The highBitSet boolean indicates the value of the high bit of
1675 // the constant which would cause it to be modified for this
1678 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1679 uint64_t Val = Op0C->getRawValue();
1680 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1684 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1686 Instruction *NewShift =
1687 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1690 InsertNewInstBefore(NewShift, I);
1692 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1697 // If this is a shift of a shift, see if we can fold the two together...
1698 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1699 if (ConstantUInt *ShiftAmt1C =
1700 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1701 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1702 unsigned ShiftAmt2 = CUI->getValue();
1704 // Check for (A << c1) << c2 and (A >> c1) >> c2
1705 if (I.getOpcode() == Op0SI->getOpcode()) {
1706 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1707 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
1708 Amt = Op0->getType()->getPrimitiveSize()*8;
1709 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1710 ConstantUInt::get(Type::UByteTy, Amt));
1713 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1714 // signed types, we can only support the (A >> c1) << c2 configuration,
1715 // because it can not turn an arbitrary bit of A into a sign bit.
1716 if (I.getType()->isUnsigned() || isLeftShift) {
1717 // Calculate bitmask for what gets shifted off the edge...
1718 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1720 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1722 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1725 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1726 C, Op0SI->getOperand(0)->getName()+".mask");
1727 InsertNewInstBefore(Mask, I);
1729 // Figure out what flavor of shift we should use...
1730 if (ShiftAmt1 == ShiftAmt2)
1731 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1732 else if (ShiftAmt1 < ShiftAmt2) {
1733 return new ShiftInst(I.getOpcode(), Mask,
1734 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1736 return new ShiftInst(Op0SI->getOpcode(), Mask,
1737 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1747 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1750 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1751 const Type *DstTy) {
1753 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1754 // are identical and the bits don't get reinterpreted (for example
1755 // int->float->int would not be allowed)
1756 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1759 // Allow free casting and conversion of sizes as long as the sign doesn't
1761 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1762 unsigned SrcSize = SrcTy->getPrimitiveSize();
1763 unsigned MidSize = MidTy->getPrimitiveSize();
1764 unsigned DstSize = DstTy->getPrimitiveSize();
1766 // Cases where we are monotonically decreasing the size of the type are
1767 // always ok, regardless of what sign changes are going on.
1769 if (SrcSize >= MidSize && MidSize >= DstSize)
1772 // Cases where the source and destination type are the same, but the middle
1773 // type is bigger are noops.
1775 if (SrcSize == DstSize && MidSize > SrcSize)
1778 // If we are monotonically growing, things are more complex.
1780 if (SrcSize <= MidSize && MidSize <= DstSize) {
1781 // We have eight combinations of signedness to worry about. Here's the
1783 static const int SignTable[8] = {
1784 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1785 1, // U U U Always ok
1786 1, // U U S Always ok
1787 3, // U S U Ok iff SrcSize != MidSize
1788 3, // U S S Ok iff SrcSize != MidSize
1789 0, // S U U Never ok
1790 2, // S U S Ok iff MidSize == DstSize
1791 1, // S S U Always ok
1792 1, // S S S Always ok
1795 // Choose an action based on the current entry of the signtable that this
1796 // cast of cast refers to...
1797 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1798 switch (SignTable[Row]) {
1799 case 0: return false; // Never ok
1800 case 1: return true; // Always ok
1801 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1802 case 3: // Ok iff SrcSize != MidSize
1803 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1804 default: assert(0 && "Bad entry in sign table!");
1809 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1810 // like: short -> ushort -> uint, because this can create wrong results if
1811 // the input short is negative!
1816 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1817 if (V->getType() == Ty || isa<Constant>(V)) return false;
1818 if (const CastInst *CI = dyn_cast<CastInst>(V))
1819 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1824 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1825 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1826 /// casts that are known to not do anything...
1828 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1829 Instruction *InsertBefore) {
1830 if (V->getType() == DestTy) return V;
1831 if (Constant *C = dyn_cast<Constant>(V))
1832 return ConstantExpr::getCast(C, DestTy);
1834 CastInst *CI = new CastInst(V, DestTy, V->getName());
1835 InsertNewInstBefore(CI, *InsertBefore);
1839 // CastInst simplification
1841 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1842 Value *Src = CI.getOperand(0);
1844 // If the user is casting a value to the same type, eliminate this cast
1846 if (CI.getType() == Src->getType())
1847 return ReplaceInstUsesWith(CI, Src);
1849 // If casting the result of another cast instruction, try to eliminate this
1852 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1853 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1854 CSrc->getType(), CI.getType())) {
1855 // This instruction now refers directly to the cast's src operand. This
1856 // has a good chance of making CSrc dead.
1857 CI.setOperand(0, CSrc->getOperand(0));
1861 // If this is an A->B->A cast, and we are dealing with integral types, try
1862 // to convert this into a logical 'and' instruction.
1864 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1865 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1866 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1867 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1868 assert(CSrc->getType() != Type::ULongTy &&
1869 "Cannot have type bigger than ulong!");
1870 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1871 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1872 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1877 // If casting the result of a getelementptr instruction with no offset, turn
1878 // this into a cast of the original pointer!
1880 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1881 bool AllZeroOperands = true;
1882 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1883 if (!isa<Constant>(GEP->getOperand(i)) ||
1884 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1885 AllZeroOperands = false;
1888 if (AllZeroOperands) {
1889 CI.setOperand(0, GEP->getOperand(0));
1894 // If we are casting a malloc or alloca to a pointer to a type of the same
1895 // size, rewrite the allocation instruction to allocate the "right" type.
1897 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1898 if (AI->hasOneUse() && !AI->isArrayAllocation())
1899 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1900 // Get the type really allocated and the type casted to...
1901 const Type *AllocElTy = AI->getAllocatedType();
1902 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1903 const Type *CastElTy = PTy->getElementType();
1904 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1906 // If the allocation is for an even multiple of the cast type size
1907 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1908 Value *Amt = ConstantUInt::get(Type::UIntTy,
1909 AllocElTySize/CastElTySize);
1910 std::string Name = AI->getName(); AI->setName("");
1911 AllocationInst *New;
1912 if (isa<MallocInst>(AI))
1913 New = new MallocInst(CastElTy, Amt, Name);
1915 New = new AllocaInst(CastElTy, Amt, Name);
1916 InsertNewInstBefore(New, CI);
1917 return ReplaceInstUsesWith(CI, New);
1921 // If the source value is an instruction with only this use, we can attempt to
1922 // propagate the cast into the instruction. Also, only handle integral types
1924 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1925 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1926 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1927 const Type *DestTy = CI.getType();
1928 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1929 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1931 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1932 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1934 switch (SrcI->getOpcode()) {
1935 case Instruction::Add:
1936 case Instruction::Mul:
1937 case Instruction::And:
1938 case Instruction::Or:
1939 case Instruction::Xor:
1940 // If we are discarding information, or just changing the sign, rewrite.
1941 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1942 // Don't insert two casts if they cannot be eliminated. We allow two
1943 // casts to be inserted if the sizes are the same. This could only be
1944 // converting signedness, which is a noop.
1945 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1946 !ValueRequiresCast(Op0, DestTy)) {
1947 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1948 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1949 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1950 ->getOpcode(), Op0c, Op1c);
1954 case Instruction::Shl:
1955 // Allow changing the sign of the source operand. Do not allow changing
1956 // the size of the shift, UNLESS the shift amount is a constant. We
1957 // mush not change variable sized shifts to a smaller size, because it
1958 // is undefined to shift more bits out than exist in the value.
1959 if (DestBitSize == SrcBitSize ||
1960 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1961 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1962 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1971 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
1972 if (ConstantBool *C = dyn_cast<ConstantBool>(SI.getCondition()))
1973 if (C == ConstantBool::True)
1974 return ReplaceInstUsesWith(SI, SI.getTrueValue());
1976 assert(C == ConstantBool::False);
1977 return ReplaceInstUsesWith(SI, SI.getFalseValue());
1979 // Other transformations are possible!
1985 // CallInst simplification
1987 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1988 // Intrinsics cannot occur in an invoke, so handle them here instead of in
1990 if (Function *F = CI.getCalledFunction())
1991 switch (F->getIntrinsicID()) {
1992 case Intrinsic::memmove:
1993 case Intrinsic::memcpy:
1994 case Intrinsic::memset:
1995 // memmove/cpy/set of zero bytes is a noop.
1996 if (Constant *NumBytes = dyn_cast<Constant>(CI.getOperand(3))) {
1997 if (NumBytes->isNullValue())
1998 return EraseInstFromFunction(CI);
2005 return visitCallSite(&CI);
2008 // InvokeInst simplification
2010 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
2011 return visitCallSite(&II);
2014 // visitCallSite - Improvements for call and invoke instructions.
2016 Instruction *InstCombiner::visitCallSite(CallSite CS) {
2017 bool Changed = false;
2019 // If the callee is a constexpr cast of a function, attempt to move the cast
2020 // to the arguments of the call/invoke.
2021 if (transformConstExprCastCall(CS)) return 0;
2023 Value *Callee = CS.getCalledValue();
2024 const PointerType *PTy = cast<PointerType>(Callee->getType());
2025 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
2026 if (FTy->isVarArg()) {
2027 // See if we can optimize any arguments passed through the varargs area of
2029 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
2030 E = CS.arg_end(); I != E; ++I)
2031 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
2032 // If this cast does not effect the value passed through the varargs
2033 // area, we can eliminate the use of the cast.
2034 Value *Op = CI->getOperand(0);
2035 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
2042 return Changed ? CS.getInstruction() : 0;
2045 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
2046 // attempt to move the cast to the arguments of the call/invoke.
2048 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
2049 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
2050 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
2051 if (CE->getOpcode() != Instruction::Cast ||
2052 !isa<ConstantPointerRef>(CE->getOperand(0)))
2054 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
2055 if (!isa<Function>(CPR->getValue())) return false;
2056 Function *Callee = cast<Function>(CPR->getValue());
2057 Instruction *Caller = CS.getInstruction();
2059 // Okay, this is a cast from a function to a different type. Unless doing so
2060 // would cause a type conversion of one of our arguments, change this call to
2061 // be a direct call with arguments casted to the appropriate types.
2063 const FunctionType *FT = Callee->getFunctionType();
2064 const Type *OldRetTy = Caller->getType();
2066 // Check to see if we are changing the return type...
2067 if (OldRetTy != FT->getReturnType()) {
2068 if (Callee->isExternal() &&
2069 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
2070 !Caller->use_empty())
2071 return false; // Cannot transform this return value...
2073 // If the callsite is an invoke instruction, and the return value is used by
2074 // a PHI node in a successor, we cannot change the return type of the call
2075 // because there is no place to put the cast instruction (without breaking
2076 // the critical edge). Bail out in this case.
2077 if (!Caller->use_empty())
2078 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
2079 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
2081 if (PHINode *PN = dyn_cast<PHINode>(*UI))
2082 if (PN->getParent() == II->getNormalDest() ||
2083 PN->getParent() == II->getUnwindDest())
2087 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
2088 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
2090 CallSite::arg_iterator AI = CS.arg_begin();
2091 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
2092 const Type *ParamTy = FT->getParamType(i);
2093 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
2094 if (Callee->isExternal() && !isConvertible) return false;
2097 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
2098 Callee->isExternal())
2099 return false; // Do not delete arguments unless we have a function body...
2101 // Okay, we decided that this is a safe thing to do: go ahead and start
2102 // inserting cast instructions as necessary...
2103 std::vector<Value*> Args;
2104 Args.reserve(NumActualArgs);
2106 AI = CS.arg_begin();
2107 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
2108 const Type *ParamTy = FT->getParamType(i);
2109 if ((*AI)->getType() == ParamTy) {
2110 Args.push_back(*AI);
2112 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
2113 InsertNewInstBefore(Cast, *Caller);
2114 Args.push_back(Cast);
2118 // If the function takes more arguments than the call was taking, add them
2120 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
2121 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
2123 // If we are removing arguments to the function, emit an obnoxious warning...
2124 if (FT->getNumParams() < NumActualArgs)
2125 if (!FT->isVarArg()) {
2126 std::cerr << "WARNING: While resolving call to function '"
2127 << Callee->getName() << "' arguments were dropped!\n";
2129 // Add all of the arguments in their promoted form to the arg list...
2130 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
2131 const Type *PTy = getPromotedType((*AI)->getType());
2132 if (PTy != (*AI)->getType()) {
2133 // Must promote to pass through va_arg area!
2134 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
2135 InsertNewInstBefore(Cast, *Caller);
2136 Args.push_back(Cast);
2138 Args.push_back(*AI);
2143 if (FT->getReturnType() == Type::VoidTy)
2144 Caller->setName(""); // Void type should not have a name...
2147 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2148 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
2149 Args, Caller->getName(), Caller);
2151 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
2154 // Insert a cast of the return type as necessary...
2156 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
2157 if (NV->getType() != Type::VoidTy) {
2158 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
2160 // If this is an invoke instruction, we should insert it after the first
2161 // non-phi, instruction in the normal successor block.
2162 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2163 BasicBlock::iterator I = II->getNormalDest()->begin();
2164 while (isa<PHINode>(I)) ++I;
2165 InsertNewInstBefore(NC, *I);
2167 // Otherwise, it's a call, just insert cast right after the call instr
2168 InsertNewInstBefore(NC, *Caller);
2170 AddUsersToWorkList(*Caller);
2172 NV = Constant::getNullValue(Caller->getType());
2176 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
2177 Caller->replaceAllUsesWith(NV);
2178 Caller->getParent()->getInstList().erase(Caller);
2179 removeFromWorkList(Caller);
2185 // PHINode simplification
2187 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2188 if (Value *V = hasConstantValue(&PN))
2189 return ReplaceInstUsesWith(PN, V);
2191 // If the only user of this instruction is a cast instruction, and all of the
2192 // incoming values are constants, change this PHI to merge together the casted
2195 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2196 if (CI->getType() != PN.getType()) { // noop casts will be folded
2197 bool AllConstant = true;
2198 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2199 if (!isa<Constant>(PN.getIncomingValue(i))) {
2200 AllConstant = false;
2204 // Make a new PHI with all casted values.
2205 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2206 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2207 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2208 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2209 PN.getIncomingBlock(i));
2212 // Update the cast instruction.
2213 CI->setOperand(0, New);
2214 WorkList.push_back(CI); // revisit the cast instruction to fold.
2215 WorkList.push_back(New); // Make sure to revisit the new Phi
2216 return &PN; // PN is now dead!
2223 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2224 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2225 // If so, eliminate the noop.
2226 if (GEP.getNumOperands() == 1)
2227 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2229 bool HasZeroPointerIndex = false;
2230 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2231 HasZeroPointerIndex = C->isNullValue();
2233 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2234 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2236 // Combine Indices - If the source pointer to this getelementptr instruction
2237 // is a getelementptr instruction, combine the indices of the two
2238 // getelementptr instructions into a single instruction.
2240 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
2241 std::vector<Value *> Indices;
2243 // Can we combine the two pointer arithmetics offsets?
2244 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
2245 isa<Constant>(GEP.getOperand(1))) {
2246 // Replace: gep (gep %P, long C1), long C2, ...
2247 // With: gep %P, long (C1+C2), ...
2248 Value *Sum = ConstantExpr::get(Instruction::Add,
2249 cast<Constant>(Src->getOperand(1)),
2250 cast<Constant>(GEP.getOperand(1)));
2251 assert(Sum && "Constant folding of longs failed!?");
2252 GEP.setOperand(0, Src->getOperand(0));
2253 GEP.setOperand(1, Sum);
2254 AddUsersToWorkList(*Src); // Reduce use count of Src
2256 } else if (Src->getNumOperands() == 2) {
2257 // Replace: gep (gep %P, long B), long A, ...
2258 // With: T = long A+B; gep %P, T, ...
2260 // Note that if our source is a gep chain itself that we wait for that
2261 // chain to be resolved before we perform this transformation. This
2262 // avoids us creating a TON of code in some cases.
2264 if (isa<GetElementPtrInst>(Src->getOperand(0)) &&
2265 cast<Instruction>(Src->getOperand(0))->getNumOperands() == 2)
2266 return 0; // Wait until our source is folded to completion.
2268 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
2270 Src->getName()+".sum", &GEP);
2271 GEP.setOperand(0, Src->getOperand(0));
2272 GEP.setOperand(1, Sum);
2273 WorkList.push_back(cast<Instruction>(Sum));
2275 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
2276 Src->getNumOperands() != 1) {
2277 // Otherwise we can do the fold if the first index of the GEP is a zero
2278 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
2279 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2280 } else if (Src->getOperand(Src->getNumOperands()-1) ==
2281 Constant::getNullValue(Type::LongTy)) {
2282 // If the src gep ends with a constant array index, merge this get into
2283 // it, even if we have a non-zero array index.
2284 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
2285 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
2288 if (!Indices.empty())
2289 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
2291 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
2292 // GEP of global variable. If all of the indices for this GEP are
2293 // constants, we can promote this to a constexpr instead of an instruction.
2295 // Scan for nonconstants...
2296 std::vector<Constant*> Indices;
2297 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2298 for (; I != E && isa<Constant>(*I); ++I)
2299 Indices.push_back(cast<Constant>(*I));
2301 if (I == E) { // If they are all constants...
2303 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2305 // Replace all uses of the GEP with the new constexpr...
2306 return ReplaceInstUsesWith(GEP, CE);
2308 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2309 if (CE->getOpcode() == Instruction::Cast) {
2310 if (HasZeroPointerIndex) {
2311 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2312 // into : GEP [10 x ubyte]* X, long 0, ...
2314 // This occurs when the program declares an array extern like "int X[];"
2316 Constant *X = CE->getOperand(0);
2317 const PointerType *CPTy = cast<PointerType>(CE->getType());
2318 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2319 if (const ArrayType *XATy =
2320 dyn_cast<ArrayType>(XTy->getElementType()))
2321 if (const ArrayType *CATy =
2322 dyn_cast<ArrayType>(CPTy->getElementType()))
2323 if (CATy->getElementType() == XATy->getElementType()) {
2324 // At this point, we know that the cast source type is a pointer
2325 // to an array of the same type as the destination pointer
2326 // array. Because the array type is never stepped over (there
2327 // is a leading zero) we can fold the cast into this GEP.
2328 GEP.setOperand(0, X);
2338 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2339 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2340 if (AI.isArrayAllocation()) // Check C != 1
2341 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2342 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2343 AllocationInst *New = 0;
2345 // Create and insert the replacement instruction...
2346 if (isa<MallocInst>(AI))
2347 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
2349 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2350 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
2353 // Scan to the end of the allocation instructions, to skip over a block of
2354 // allocas if possible...
2356 BasicBlock::iterator It = New;
2357 while (isa<AllocationInst>(*It)) ++It;
2359 // Now that I is pointing to the first non-allocation-inst in the block,
2360 // insert our getelementptr instruction...
2362 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
2363 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2365 // Now make everything use the getelementptr instead of the original
2367 ReplaceInstUsesWith(AI, V);
2373 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2374 Value *Op = FI.getOperand(0);
2376 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2377 if (CastInst *CI = dyn_cast<CastInst>(Op))
2378 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2379 FI.setOperand(0, CI->getOperand(0));
2383 // If we have 'free null' delete the instruction. This can happen in stl code
2384 // when lots of inlining happens.
2385 if (isa<ConstantPointerNull>(Op))
2386 return EraseInstFromFunction(FI);
2392 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2393 /// constantexpr, return the constant value being addressed by the constant
2394 /// expression, or null if something is funny.
2396 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2397 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
2398 return 0; // Do not allow stepping over the value!
2400 // Loop over all of the operands, tracking down which value we are
2402 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2403 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2404 ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
2405 if (CS == 0) return 0;
2406 if (CU->getValue() >= CS->getValues().size()) return 0;
2407 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2408 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2409 ConstantArray *CA = dyn_cast<ConstantArray>(C);
2410 if (CA == 0) return 0;
2411 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2412 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2418 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2419 Value *Op = LI.getOperand(0);
2420 if (LI.isVolatile()) return 0;
2422 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2423 Op = CPR->getValue();
2425 // Instcombine load (constant global) into the value loaded...
2426 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2427 if (GV->isConstant() && !GV->isExternal())
2428 return ReplaceInstUsesWith(LI, GV->getInitializer());
2430 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2431 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2432 if (CE->getOpcode() == Instruction::GetElementPtr)
2433 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2434 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2435 if (GV->isConstant() && !GV->isExternal())
2436 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2437 return ReplaceInstUsesWith(LI, V);
2442 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2443 // Change br (not X), label True, label False to: br X, label False, True
2444 if (BI.isConditional() && !isa<Constant>(BI.getCondition())) {
2445 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2446 BasicBlock *TrueDest = BI.getSuccessor(0);
2447 BasicBlock *FalseDest = BI.getSuccessor(1);
2448 // Swap Destinations and condition...
2450 BI.setSuccessor(0, FalseDest);
2451 BI.setSuccessor(1, TrueDest);
2453 } else if (SetCondInst *I = dyn_cast<SetCondInst>(BI.getCondition())) {
2454 // Cannonicalize setne -> seteq
2455 if ((I->getOpcode() == Instruction::SetNE ||
2456 I->getOpcode() == Instruction::SetLE ||
2457 I->getOpcode() == Instruction::SetGE) && I->hasOneUse()) {
2458 std::string Name = I->getName(); I->setName("");
2459 Instruction::BinaryOps NewOpcode =
2460 SetCondInst::getInverseCondition(I->getOpcode());
2461 Value *NewSCC = BinaryOperator::create(NewOpcode, I->getOperand(0),
2462 I->getOperand(1), Name, I);
2463 BasicBlock *TrueDest = BI.getSuccessor(0);
2464 BasicBlock *FalseDest = BI.getSuccessor(1);
2465 // Swap Destinations and condition...
2466 BI.setCondition(NewSCC);
2467 BI.setSuccessor(0, FalseDest);
2468 BI.setSuccessor(1, TrueDest);
2469 removeFromWorkList(I);
2470 I->getParent()->getInstList().erase(I);
2471 WorkList.push_back(cast<Instruction>(NewSCC));
2480 void InstCombiner::removeFromWorkList(Instruction *I) {
2481 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2485 bool InstCombiner::runOnFunction(Function &F) {
2486 bool Changed = false;
2487 TD = &getAnalysis<TargetData>();
2489 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2491 while (!WorkList.empty()) {
2492 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2493 WorkList.pop_back();
2495 // Check to see if we can DCE or ConstantPropagate the instruction...
2496 // Check to see if we can DIE the instruction...
2497 if (isInstructionTriviallyDead(I)) {
2498 // Add operands to the worklist...
2499 if (I->getNumOperands() < 4)
2500 AddUsesToWorkList(*I);
2503 I->getParent()->getInstList().erase(I);
2504 removeFromWorkList(I);
2508 // Instruction isn't dead, see if we can constant propagate it...
2509 if (Constant *C = ConstantFoldInstruction(I)) {
2510 // Add operands to the worklist...
2511 AddUsesToWorkList(*I);
2512 ReplaceInstUsesWith(*I, C);
2515 I->getParent()->getInstList().erase(I);
2516 removeFromWorkList(I);
2520 // Now that we have an instruction, try combining it to simplify it...
2521 if (Instruction *Result = visit(*I)) {
2523 // Should we replace the old instruction with a new one?
2525 // Instructions can end up on the worklist more than once. Make sure
2526 // we do not process an instruction that has been deleted.
2527 removeFromWorkList(I);
2529 // Move the name to the new instruction first...
2530 std::string OldName = I->getName(); I->setName("");
2531 Result->setName(OldName);
2533 // Insert the new instruction into the basic block...
2534 BasicBlock *InstParent = I->getParent();
2535 InstParent->getInstList().insert(I, Result);
2537 // Everything uses the new instruction now...
2538 I->replaceAllUsesWith(Result);
2540 // Erase the old instruction.
2541 InstParent->getInstList().erase(I);
2543 BasicBlock::iterator II = I;
2545 // If the instruction was modified, it's possible that it is now dead.
2546 // if so, remove it.
2547 if (dceInstruction(II)) {
2548 // Instructions may end up in the worklist more than once. Erase them
2550 removeFromWorkList(I);
2556 WorkList.push_back(Result);
2557 AddUsersToWorkList(*Result);
2566 Pass *llvm::createInstructionCombiningPass() {
2567 return new InstCombiner();