1 //===- InstructionCombining.cpp - Combine multiple instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // InstructionCombining - Combine instructions to form fewer, simple
11 // instructions. This pass does not modify the CFG This pass is where algebraic
12 // simplification happens.
14 // This pass combines things like:
20 // This is a simple worklist driven algorithm.
22 // This pass guarantees that the following canonicalizations are performed on
24 // 1. If a binary operator has a constant operand, it is moved to the RHS
25 // 2. Bitwise operators with constant operands are always grouped so that
26 // shifts are performed first, then or's, then and's, then xor's.
27 // 3. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible
28 // 4. All SetCC instructions on boolean values are replaced with logical ops
29 // 5. add X, X is represented as (X*2) => (X << 1)
30 // 6. Multiplies with a power-of-two constant argument are transformed into
32 // N. This list is incomplete
34 //===----------------------------------------------------------------------===//
36 #define DEBUG_TYPE "instcombine"
37 #include "llvm/Transforms/Scalar.h"
38 #include "llvm/Instructions.h"
39 #include "llvm/Intrinsics.h"
40 #include "llvm/Pass.h"
41 #include "llvm/Constants.h"
42 #include "llvm/DerivedTypes.h"
43 #include "llvm/GlobalVariable.h"
44 #include "llvm/Target/TargetData.h"
45 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
46 #include "llvm/Transforms/Utils/Local.h"
47 #include "llvm/Support/InstIterator.h"
48 #include "llvm/Support/InstVisitor.h"
49 #include "llvm/Support/CallSite.h"
50 #include "Support/Debug.h"
51 #include "Support/Statistic.h"
56 Statistic<> NumCombined ("instcombine", "Number of insts combined");
57 Statistic<> NumConstProp("instcombine", "Number of constant folds");
58 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
60 class InstCombiner : public FunctionPass,
61 public InstVisitor<InstCombiner, Instruction*> {
62 // Worklist of all of the instructions that need to be simplified.
63 std::vector<Instruction*> WorkList;
66 /// AddUsersToWorkList - When an instruction is simplified, add all users of
67 /// the instruction to the work lists because they might get more simplified
70 void AddUsersToWorkList(Instruction &I) {
71 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
73 WorkList.push_back(cast<Instruction>(*UI));
76 /// AddUsesToWorkList - When an instruction is simplified, add operands to
77 /// the work lists because they might get more simplified now.
79 void AddUsesToWorkList(Instruction &I) {
80 for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
81 if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i)))
82 WorkList.push_back(Op);
85 // removeFromWorkList - remove all instances of I from the worklist.
86 void removeFromWorkList(Instruction *I);
88 virtual bool runOnFunction(Function &F);
90 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
91 AU.addRequired<TargetData>();
95 // Visitation implementation - Implement instruction combining for different
96 // instruction types. The semantics are as follows:
98 // null - No change was made
99 // I - Change was made, I is still valid, I may be dead though
100 // otherwise - Change was made, replace I with returned instruction
102 Instruction *visitAdd(BinaryOperator &I);
103 Instruction *visitSub(BinaryOperator &I);
104 Instruction *visitMul(BinaryOperator &I);
105 Instruction *visitDiv(BinaryOperator &I);
106 Instruction *visitRem(BinaryOperator &I);
107 Instruction *visitAnd(BinaryOperator &I);
108 Instruction *visitOr (BinaryOperator &I);
109 Instruction *visitXor(BinaryOperator &I);
110 Instruction *visitSetCondInst(BinaryOperator &I);
111 Instruction *visitShiftInst(ShiftInst &I);
112 Instruction *visitCastInst(CastInst &CI);
113 Instruction *visitSelectInst(SelectInst &CI);
114 Instruction *visitCallInst(CallInst &CI);
115 Instruction *visitInvokeInst(InvokeInst &II);
116 Instruction *visitPHINode(PHINode &PN);
117 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
118 Instruction *visitAllocationInst(AllocationInst &AI);
119 Instruction *visitFreeInst(FreeInst &FI);
120 Instruction *visitLoadInst(LoadInst &LI);
121 Instruction *visitBranchInst(BranchInst &BI);
123 // visitInstruction - Specify what to return for unhandled instructions...
124 Instruction *visitInstruction(Instruction &I) { return 0; }
127 Instruction *visitCallSite(CallSite CS);
128 bool transformConstExprCastCall(CallSite CS);
130 // InsertNewInstBefore - insert an instruction New before instruction Old
131 // in the program. Add the new instruction to the worklist.
133 Value *InsertNewInstBefore(Instruction *New, Instruction &Old) {
134 assert(New && New->getParent() == 0 &&
135 "New instruction already inserted into a basic block!");
136 BasicBlock *BB = Old.getParent();
137 BB->getInstList().insert(&Old, New); // Insert inst
138 WorkList.push_back(New); // Add to worklist
143 // ReplaceInstUsesWith - This method is to be used when an instruction is
144 // found to be dead, replacable with another preexisting expression. Here
145 // we add all uses of I to the worklist, replace all uses of I with the new
146 // value, then return I, so that the inst combiner will know that I was
149 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
150 AddUsersToWorkList(I); // Add all modified instrs to worklist
151 I.replaceAllUsesWith(V);
155 // EraseInstFromFunction - When dealing with an instruction that has side
156 // effects or produces a void value, we can't rely on DCE to delete the
157 // instruction. Instead, visit methods should return the value returned by
159 Instruction *EraseInstFromFunction(Instruction &I) {
160 assert(I.use_empty() && "Cannot erase instruction that is used!");
161 AddUsesToWorkList(I);
162 removeFromWorkList(&I);
163 I.getParent()->getInstList().erase(&I);
164 return 0; // Don't do anything with FI
169 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
170 /// InsertBefore instruction. This is specialized a bit to avoid inserting
171 /// casts that are known to not do anything...
173 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
174 Instruction *InsertBefore);
176 // SimplifyCommutative - This performs a few simplifications for commutative
178 bool SimplifyCommutative(BinaryOperator &I);
180 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
181 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
184 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
187 // getComplexity: Assign a complexity or rank value to LLVM Values...
188 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
189 static unsigned getComplexity(Value *V) {
190 if (isa<Instruction>(V)) {
191 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
195 if (isa<Argument>(V)) return 2;
196 return isa<Constant>(V) ? 0 : 1;
199 // isOnlyUse - Return true if this instruction will be deleted if we stop using
201 static bool isOnlyUse(Value *V) {
202 return V->hasOneUse() || isa<Constant>(V);
205 // getSignedIntegralType - Given an unsigned integral type, return the signed
206 // version of it that has the same size.
207 static const Type *getSignedIntegralType(const Type *Ty) {
208 switch (Ty->getPrimitiveID()) {
209 default: assert(0 && "Invalid unsigned integer type!"); abort();
210 case Type::UByteTyID: return Type::SByteTy;
211 case Type::UShortTyID: return Type::ShortTy;
212 case Type::UIntTyID: return Type::IntTy;
213 case Type::ULongTyID: return Type::LongTy;
217 // getUnsignedIntegralType - Given an signed integral type, return the unsigned
218 // version of it that has the same size.
219 static const Type *getUnsignedIntegralType(const Type *Ty) {
220 switch (Ty->getPrimitiveID()) {
221 default: assert(0 && "Invalid signed integer type!"); abort();
222 case Type::SByteTyID: return Type::UByteTy;
223 case Type::ShortTyID: return Type::UShortTy;
224 case Type::IntTyID: return Type::UIntTy;
225 case Type::LongTyID: return Type::ULongTy;
229 // getPromotedType - Return the specified type promoted as it would be to pass
230 // though a va_arg area...
231 static const Type *getPromotedType(const Type *Ty) {
232 switch (Ty->getPrimitiveID()) {
233 case Type::SByteTyID:
234 case Type::ShortTyID: return Type::IntTy;
235 case Type::UByteTyID:
236 case Type::UShortTyID: return Type::UIntTy;
237 case Type::FloatTyID: return Type::DoubleTy;
242 // SimplifyCommutative - This performs a few simplifications for commutative
245 // 1. Order operands such that they are listed from right (least complex) to
246 // left (most complex). This puts constants before unary operators before
249 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
250 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
252 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
253 bool Changed = false;
254 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
255 Changed = !I.swapOperands();
257 if (!I.isAssociative()) return Changed;
258 Instruction::BinaryOps Opcode = I.getOpcode();
259 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
260 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
261 if (isa<Constant>(I.getOperand(1))) {
262 Constant *Folded = ConstantExpr::get(I.getOpcode(),
263 cast<Constant>(I.getOperand(1)),
264 cast<Constant>(Op->getOperand(1)));
265 I.setOperand(0, Op->getOperand(0));
266 I.setOperand(1, Folded);
268 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
269 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
270 isOnlyUse(Op) && isOnlyUse(Op1)) {
271 Constant *C1 = cast<Constant>(Op->getOperand(1));
272 Constant *C2 = cast<Constant>(Op1->getOperand(1));
274 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
275 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
276 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
279 WorkList.push_back(New);
280 I.setOperand(0, New);
281 I.setOperand(1, Folded);
288 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
289 // if the LHS is a constant zero (which is the 'negate' form).
291 static inline Value *dyn_castNegVal(Value *V) {
292 if (BinaryOperator::isNeg(V))
293 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
295 // Constants can be considered to be negated values if they can be folded...
296 if (Constant *C = dyn_cast<Constant>(V))
297 return ConstantExpr::get(Instruction::Sub,
298 Constant::getNullValue(V->getType()), C);
302 static Constant *NotConstant(Constant *C) {
303 return ConstantExpr::get(Instruction::Xor, C,
304 ConstantIntegral::getAllOnesValue(C->getType()));
307 static inline Value *dyn_castNotVal(Value *V) {
308 if (BinaryOperator::isNot(V))
309 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
311 // Constants can be considered to be not'ed values...
312 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
313 return NotConstant(C);
317 // dyn_castFoldableMul - If this value is a multiply that can be folded into
318 // other computations (because it has a constant operand), return the
319 // non-constant operand of the multiply.
321 static inline Value *dyn_castFoldableMul(Value *V) {
322 if (V->hasOneUse() && V->getType()->isInteger())
323 if (Instruction *I = dyn_cast<Instruction>(V))
324 if (I->getOpcode() == Instruction::Mul)
325 if (isa<Constant>(I->getOperand(1)))
326 return I->getOperand(0);
330 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
331 // a constant, return the constant being anded with.
333 template<class ValueType>
334 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
335 if (Instruction *I = dyn_cast<Instruction>(V))
336 if (I->getOpcode() == Instruction::And)
337 return dyn_cast<Constant>(I->getOperand(1));
339 // If this is a constant, it acts just like we were masking with it.
340 return dyn_cast<Constant>(V);
343 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
345 static unsigned Log2(uint64_t Val) {
346 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
349 if (Val & 1) return 0; // Multiple bits set?
357 /// AssociativeOpt - Perform an optimization on an associative operator. This
358 /// function is designed to check a chain of associative operators for a
359 /// potential to apply a certain optimization. Since the optimization may be
360 /// applicable if the expression was reassociated, this checks the chain, then
361 /// reassociates the expression as necessary to expose the optimization
362 /// opportunity. This makes use of a special Functor, which must define
363 /// 'shouldApply' and 'apply' methods.
365 template<typename Functor>
366 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
367 unsigned Opcode = Root.getOpcode();
368 Value *LHS = Root.getOperand(0);
370 // Quick check, see if the immediate LHS matches...
371 if (F.shouldApply(LHS))
372 return F.apply(Root);
374 // Otherwise, if the LHS is not of the same opcode as the root, return.
375 Instruction *LHSI = dyn_cast<Instruction>(LHS);
376 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
377 // Should we apply this transform to the RHS?
378 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
380 // If not to the RHS, check to see if we should apply to the LHS...
381 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
382 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
386 // If the functor wants to apply the optimization to the RHS of LHSI,
387 // reassociate the expression from ((? op A) op B) to (? op (A op B))
389 BasicBlock *BB = Root.getParent();
390 // All of the instructions have a single use and have no side-effects,
391 // because of this, we can pull them all into the current basic block.
392 if (LHSI->getParent() != BB) {
393 // Move all of the instructions from root to LHSI into the current
395 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
396 Instruction *LastUse = &Root;
397 while (TmpLHSI->getParent() == BB) {
399 TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
402 // Loop over all of the instructions in other blocks, moving them into
404 Value *TmpLHS = TmpLHSI;
406 TmpLHSI = cast<Instruction>(TmpLHS);
407 // Remove from current block...
408 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
409 // Insert before the last instruction...
410 BB->getInstList().insert(LastUse, TmpLHSI);
411 TmpLHS = TmpLHSI->getOperand(0);
412 } while (TmpLHSI != LHSI);
415 // Now all of the instructions are in the current basic block, go ahead
416 // and perform the reassociation.
417 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
419 // First move the selected RHS to the LHS of the root...
420 Root.setOperand(0, LHSI->getOperand(1));
422 // Make what used to be the LHS of the root be the user of the root...
423 Value *ExtraOperand = TmpLHSI->getOperand(1);
424 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
425 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
426 BB->getInstList().remove(&Root); // Remove root from the BB
427 BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
429 // Now propagate the ExtraOperand down the chain of instructions until we
431 while (TmpLHSI != LHSI) {
432 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
433 Value *NextOp = NextLHSI->getOperand(1);
434 NextLHSI->setOperand(1, ExtraOperand);
436 ExtraOperand = NextOp;
439 // Now that the instructions are reassociated, have the functor perform
440 // the transformation...
441 return F.apply(Root);
444 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
450 // AddRHS - Implements: X + X --> X << 1
453 AddRHS(Value *rhs) : RHS(rhs) {}
454 bool shouldApply(Value *LHS) const { return LHS == RHS; }
455 Instruction *apply(BinaryOperator &Add) const {
456 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
457 ConstantInt::get(Type::UByteTy, 1));
461 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
463 struct AddMaskingAnd {
465 AddMaskingAnd(Constant *c) : C2(c) {}
466 bool shouldApply(Value *LHS) const {
467 if (Constant *C1 = dyn_castMaskingAnd(LHS))
468 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
471 Instruction *apply(BinaryOperator &Add) const {
472 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
479 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
480 bool Changed = SimplifyCommutative(I);
481 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
484 if (!I.getType()->isFloatingPoint() && // -0 + +0 = +0, so it's not a noop
485 RHS == Constant::getNullValue(I.getType()))
486 return ReplaceInstUsesWith(I, LHS);
489 if (I.getType()->isInteger())
490 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
493 if (Value *V = dyn_castNegVal(LHS))
494 return BinaryOperator::create(Instruction::Sub, RHS, V);
497 if (!isa<Constant>(RHS))
498 if (Value *V = dyn_castNegVal(RHS))
499 return BinaryOperator::create(Instruction::Sub, LHS, V);
501 // X*C + X --> X * (C+1)
502 if (dyn_castFoldableMul(LHS) == RHS) {
504 ConstantExpr::get(Instruction::Add,
505 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
506 ConstantInt::get(I.getType(), 1));
507 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
510 // X + X*C --> X * (C+1)
511 if (dyn_castFoldableMul(RHS) == LHS) {
513 ConstantExpr::get(Instruction::Add,
514 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
515 ConstantInt::get(I.getType(), 1));
516 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
519 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
520 if (Constant *C2 = dyn_castMaskingAnd(RHS))
521 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
523 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
524 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
525 switch (ILHS->getOpcode()) {
526 case Instruction::Xor:
527 // ~X + C --> (C-1) - X
528 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
529 if (XorRHS->isAllOnesValue())
530 return BinaryOperator::create(Instruction::Sub,
531 ConstantExpr::get(Instruction::Sub,
532 CRHS, ConstantInt::get(I.getType(), 1)),
533 ILHS->getOperand(0));
540 return Changed ? &I : 0;
543 // isSignBit - Return true if the value represented by the constant only has the
544 // highest order bit set.
545 static bool isSignBit(ConstantInt *CI) {
546 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
547 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
550 static unsigned getTypeSizeInBits(const Type *Ty) {
551 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
554 /// RemoveNoopCast - Strip off nonconverting casts from the value.
556 static Value *RemoveNoopCast(Value *V) {
557 if (CastInst *CI = dyn_cast<CastInst>(V)) {
558 const Type *CTy = CI->getType();
559 const Type *OpTy = CI->getOperand(0)->getType();
560 if (CTy->isInteger() && OpTy->isInteger()) {
561 if (CTy->getPrimitiveSize() == OpTy->getPrimitiveSize())
562 return RemoveNoopCast(CI->getOperand(0));
563 } else if (isa<PointerType>(CTy) && isa<PointerType>(OpTy))
564 return RemoveNoopCast(CI->getOperand(0));
569 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
570 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
572 if (Op0 == Op1) // sub X, X -> 0
573 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
575 // If this is a 'B = x-(-A)', change to B = x+A...
576 if (Value *V = dyn_castNegVal(Op1))
577 return BinaryOperator::create(Instruction::Add, Op0, V);
579 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
580 // Replace (-1 - A) with (~A)...
581 if (C->isAllOnesValue())
582 return BinaryOperator::createNot(Op1);
584 // C - ~X == X + (1+C)
585 if (BinaryOperator::isNot(Op1))
586 return BinaryOperator::create(Instruction::Add,
587 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
588 ConstantExpr::get(Instruction::Add, C,
589 ConstantInt::get(I.getType(), 1)));
590 // -((uint)X >> 31) -> ((int)X >> 31)
591 // -((int)X >> 31) -> ((uint)X >> 31)
592 if (C->isNullValue()) {
593 Value *NoopCastedRHS = RemoveNoopCast(Op1);
594 if (ShiftInst *SI = dyn_cast<ShiftInst>(NoopCastedRHS))
595 if (SI->getOpcode() == Instruction::Shr)
596 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
598 if (SI->getType()->isSigned())
599 NewTy = getUnsignedIntegralType(SI->getType());
601 NewTy = getSignedIntegralType(SI->getType());
602 // Check to see if we are shifting out everything but the sign bit.
603 if (CU->getValue() == SI->getType()->getPrimitiveSize()*8-1) {
604 // Ok, the transformation is safe. Insert a cast of the incoming
605 // value, then the new shift, then the new cast.
606 Instruction *FirstCast = new CastInst(SI->getOperand(0), NewTy,
607 SI->getOperand(0)->getName());
608 Value *InV = InsertNewInstBefore(FirstCast, I);
609 Instruction *NewShift = new ShiftInst(Instruction::Shr, FirstCast,
611 if (NewShift->getType() == I.getType())
614 InV = InsertNewInstBefore(NewShift, I);
615 return new CastInst(NewShift, I.getType());
622 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
623 if (Op1I->hasOneUse()) {
624 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
625 // is not used by anyone else...
627 if (Op1I->getOpcode() == Instruction::Sub &&
628 !Op1I->getType()->isFloatingPoint()) {
629 // Swap the two operands of the subexpr...
630 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
631 Op1I->setOperand(0, IIOp1);
632 Op1I->setOperand(1, IIOp0);
634 // Create the new top level add instruction...
635 return BinaryOperator::create(Instruction::Add, Op0, Op1);
638 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
640 if (Op1I->getOpcode() == Instruction::And &&
641 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
642 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
644 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
645 return BinaryOperator::create(Instruction::And, Op0, NewNot);
648 // X - X*C --> X * (1-C)
649 if (dyn_castFoldableMul(Op1I) == Op0) {
651 ConstantExpr::get(Instruction::Sub,
652 ConstantInt::get(I.getType(), 1),
653 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
654 assert(CP1 && "Couldn't constant fold 1-C?");
655 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
659 // X*C - X --> X * (C-1)
660 if (dyn_castFoldableMul(Op0) == Op1) {
662 ConstantExpr::get(Instruction::Sub,
663 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
664 ConstantInt::get(I.getType(), 1));
665 assert(CP1 && "Couldn't constant fold C - 1?");
666 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
672 /// isSignBitCheck - Given an exploded setcc instruction, return true if it is
673 /// really just returns true if the most significant (sign) bit is set.
674 static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
675 if (RHS->getType()->isSigned()) {
676 // True if source is LHS < 0 or LHS <= -1
677 return Opcode == Instruction::SetLT && RHS->isNullValue() ||
678 Opcode == Instruction::SetLE && RHS->isAllOnesValue();
680 ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
681 // True if source is LHS > 127 or LHS >= 128, where the constants depend on
682 // the size of the integer type.
683 if (Opcode == Instruction::SetGE)
684 return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1);
685 if (Opcode == Instruction::SetGT)
686 return RHSC->getValue() ==
687 (1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
692 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
693 bool Changed = SimplifyCommutative(I);
694 Value *Op0 = I.getOperand(0);
696 // Simplify mul instructions with a constant RHS...
697 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
698 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
700 // ((X << C1)*C2) == (X * (C2 << C1))
701 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
702 if (SI->getOpcode() == Instruction::Shl)
703 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
704 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
705 ConstantExpr::get(Instruction::Shl, CI, ShOp));
707 if (CI->isNullValue())
708 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
709 if (CI->equalsInt(1)) // X * 1 == X
710 return ReplaceInstUsesWith(I, Op0);
711 if (CI->isAllOnesValue()) // X * -1 == 0 - X
712 return BinaryOperator::createNeg(Op0, I.getName());
714 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
715 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
716 return new ShiftInst(Instruction::Shl, Op0,
717 ConstantUInt::get(Type::UByteTy, C));
719 ConstantFP *Op1F = cast<ConstantFP>(Op1);
720 if (Op1F->isNullValue())
721 return ReplaceInstUsesWith(I, Op1);
723 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
724 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
725 if (Op1F->getValue() == 1.0)
726 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
730 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
731 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
732 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
734 // If one of the operands of the multiply is a cast from a boolean value, then
735 // we know the bool is either zero or one, so this is a 'masking' multiply.
736 // See if we can simplify things based on how the boolean was originally
738 CastInst *BoolCast = 0;
739 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
740 if (CI->getOperand(0)->getType() == Type::BoolTy)
743 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
744 if (CI->getOperand(0)->getType() == Type::BoolTy)
747 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
748 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
749 const Type *SCOpTy = SCIOp0->getType();
751 // If the setcc is true iff the sign bit of X is set, then convert this
752 // multiply into a shift/and combination.
753 if (isa<ConstantInt>(SCIOp1) &&
754 isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
755 // Shift the X value right to turn it into "all signbits".
756 Constant *Amt = ConstantUInt::get(Type::UByteTy,
757 SCOpTy->getPrimitiveSize()*8-1);
758 if (SCIOp0->getType()->isUnsigned()) {
759 const Type *NewTy = getSignedIntegralType(SCIOp0->getType());
760 SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
761 SCIOp0->getName()), I);
765 InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
766 BoolCast->getOperand(0)->getName()+
769 // If the multiply type is not the same as the source type, sign extend
770 // or truncate to the multiply type.
771 if (I.getType() != V->getType())
772 V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
774 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
775 return BinaryOperator::create(Instruction::And, V, OtherOp);
780 return Changed ? &I : 0;
783 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
785 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
786 if (RHS->equalsInt(1))
787 return ReplaceInstUsesWith(I, I.getOperand(0));
789 // Check to see if this is an unsigned division with an exact power of 2,
790 // if so, convert to a right shift.
791 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
792 if (uint64_t Val = C->getValue()) // Don't break X / 0
793 if (uint64_t C = Log2(Val))
794 return new ShiftInst(Instruction::Shr, I.getOperand(0),
795 ConstantUInt::get(Type::UByteTy, C));
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()));
807 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
808 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
809 if (RHS->equalsInt(1)) // X % 1 == 0
810 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
811 if (RHS->isAllOnesValue()) // X % -1 == 0
812 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
814 // Check to see if this is an unsigned remainder with an exact power of 2,
815 // if so, convert to a bitwise and.
816 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
817 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
819 return BinaryOperator::create(Instruction::And, I.getOperand(0),
820 ConstantUInt::get(I.getType(), Val-1));
823 // 0 % X == 0, we don't need to preserve faults!
824 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
825 if (LHS->equalsInt(0))
826 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
831 // isMaxValueMinusOne - return true if this is Max-1
832 static bool isMaxValueMinusOne(const ConstantInt *C) {
833 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
834 // Calculate -1 casted to the right type...
835 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
836 uint64_t Val = ~0ULL; // All ones
837 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
838 return CU->getValue() == Val-1;
841 const ConstantSInt *CS = cast<ConstantSInt>(C);
843 // Calculate 0111111111..11111
844 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
845 int64_t Val = INT64_MAX; // All ones
846 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
847 return CS->getValue() == Val-1;
850 // isMinValuePlusOne - return true if this is Min+1
851 static bool isMinValuePlusOne(const ConstantInt *C) {
852 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
853 return CU->getValue() == 1;
855 const ConstantSInt *CS = cast<ConstantSInt>(C);
857 // Calculate 1111111111000000000000
858 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
859 int64_t Val = -1; // All ones
860 Val <<= TypeBits-1; // Shift over to the right spot
861 return CS->getValue() == Val+1;
864 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
865 /// are carefully arranged to allow folding of expressions such as:
867 /// (A < B) | (A > B) --> (A != B)
869 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
870 /// represents that the comparison is true if A == B, and bit value '1' is true
873 static unsigned getSetCondCode(const SetCondInst *SCI) {
874 switch (SCI->getOpcode()) {
876 case Instruction::SetGT: return 1;
877 case Instruction::SetEQ: return 2;
878 case Instruction::SetGE: return 3;
879 case Instruction::SetLT: return 4;
880 case Instruction::SetNE: return 5;
881 case Instruction::SetLE: return 6;
884 assert(0 && "Invalid SetCC opcode!");
889 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
890 /// opcode and two operands into either a constant true or false, or a brand new
891 /// SetCC instruction.
892 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
894 case 0: return ConstantBool::False;
895 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
896 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
897 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
898 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
899 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
900 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
901 case 7: return ConstantBool::True;
902 default: assert(0 && "Illegal SetCCCode!"); return 0;
906 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
907 struct FoldSetCCLogical {
910 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
911 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
912 bool shouldApply(Value *V) const {
913 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
914 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
915 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
918 Instruction *apply(BinaryOperator &Log) const {
919 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
920 if (SCI->getOperand(0) != LHS) {
921 assert(SCI->getOperand(1) == LHS);
922 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
925 unsigned LHSCode = getSetCondCode(SCI);
926 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
928 switch (Log.getOpcode()) {
929 case Instruction::And: Code = LHSCode & RHSCode; break;
930 case Instruction::Or: Code = LHSCode | RHSCode; break;
931 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
932 default: assert(0 && "Illegal logical opcode!"); return 0;
935 Value *RV = getSetCCValue(Code, LHS, RHS);
936 if (Instruction *I = dyn_cast<Instruction>(RV))
938 // Otherwise, it's a constant boolean value...
939 return IC.ReplaceInstUsesWith(Log, RV);
944 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
945 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
946 // guaranteed to be either a shift instruction or a binary operator.
947 Instruction *InstCombiner::OptAndOp(Instruction *Op,
948 ConstantIntegral *OpRHS,
949 ConstantIntegral *AndRHS,
950 BinaryOperator &TheAnd) {
951 Value *X = Op->getOperand(0);
952 Constant *Together = 0;
953 if (!isa<ShiftInst>(Op))
954 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
956 switch (Op->getOpcode()) {
957 case Instruction::Xor:
958 if (Together->isNullValue()) {
959 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
960 return BinaryOperator::create(Instruction::And, X, AndRHS);
961 } else if (Op->hasOneUse()) {
962 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
963 std::string OpName = Op->getName(); Op->setName("");
964 Instruction *And = BinaryOperator::create(Instruction::And,
966 InsertNewInstBefore(And, TheAnd);
967 return BinaryOperator::create(Instruction::Xor, And, Together);
970 case Instruction::Or:
971 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
972 if (Together->isNullValue())
973 return BinaryOperator::create(Instruction::And, X, AndRHS);
975 if (Together == AndRHS) // (X | C) & C --> C
976 return ReplaceInstUsesWith(TheAnd, AndRHS);
978 if (Op->hasOneUse() && Together != OpRHS) {
979 // (X | C1) & C2 --> (X | (C1&C2)) & C2
980 std::string Op0Name = Op->getName(); Op->setName("");
981 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
983 InsertNewInstBefore(Or, TheAnd);
984 return BinaryOperator::create(Instruction::And, Or, AndRHS);
988 case Instruction::Add:
989 if (Op->hasOneUse()) {
990 // Adding a one to a single bit bit-field should be turned into an XOR
991 // of the bit. First thing to check is to see if this AND is with a
992 // single bit constant.
993 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
995 // Clear bits that are not part of the constant.
996 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
998 // If there is only one bit set...
999 if ((AndRHSV & (AndRHSV-1)) == 0) {
1000 // Ok, at this point, we know that we are masking the result of the
1001 // ADD down to exactly one bit. If the constant we are adding has
1002 // no bits set below this bit, then we can eliminate the ADD.
1003 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
1005 // Check to see if any bits below the one bit set in AndRHSV are set.
1006 if ((AddRHS & (AndRHSV-1)) == 0) {
1007 // If not, the only thing that can effect the output of the AND is
1008 // the bit specified by AndRHSV. If that bit is set, the effect of
1009 // the XOR is to toggle the bit. If it is clear, then the ADD has
1011 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
1012 TheAnd.setOperand(0, X);
1015 std::string Name = Op->getName(); Op->setName("");
1016 // Pull the XOR out of the AND.
1017 Instruction *NewAnd =
1018 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
1019 InsertNewInstBefore(NewAnd, TheAnd);
1020 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
1027 case Instruction::Shl: {
1028 // We know that the AND will not produce any of the bits shifted in, so if
1029 // the anded constant includes them, clear them now!
1031 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1032 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1033 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
1035 TheAnd.setOperand(1, CI);
1040 case Instruction::Shr:
1041 // We know that the AND will not produce any of the bits shifted in, so if
1042 // the anded constant includes them, clear them now! This only applies to
1043 // unsigned shifts, because a signed shr may bring in set bits!
1045 if (AndRHS->getType()->isUnsigned()) {
1046 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1047 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1048 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
1050 TheAnd.setOperand(1, CI);
1060 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
1061 bool Changed = SimplifyCommutative(I);
1062 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1064 // and X, X = X and X, 0 == 0
1065 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1066 return ReplaceInstUsesWith(I, Op1);
1069 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1070 if (RHS->isAllOnesValue())
1071 return ReplaceInstUsesWith(I, Op0);
1073 // Optimize a variety of ((val OP C1) & C2) combinations...
1074 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
1075 Instruction *Op0I = cast<Instruction>(Op0);
1076 Value *X = Op0I->getOperand(0);
1077 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1078 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
1083 Value *Op0NotVal = dyn_castNotVal(Op0);
1084 Value *Op1NotVal = dyn_castNotVal(Op1);
1086 // (~A & ~B) == (~(A | B)) - Demorgan's Law
1087 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1088 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
1089 Op1NotVal,I.getName()+".demorgan");
1090 InsertNewInstBefore(Or, I);
1091 return BinaryOperator::createNot(Or);
1094 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1095 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1097 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1098 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1099 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1102 return Changed ? &I : 0;
1107 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1108 bool Changed = SimplifyCommutative(I);
1109 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1111 // or X, X = X or X, 0 == X
1112 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1113 return ReplaceInstUsesWith(I, Op0);
1116 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1117 if (RHS->isAllOnesValue())
1118 return ReplaceInstUsesWith(I, Op1);
1120 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1121 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1122 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
1123 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1124 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1125 Instruction *Or = BinaryOperator::create(Instruction::Or,
1126 Op0I->getOperand(0), RHS,
1128 InsertNewInstBefore(Or, I);
1129 return BinaryOperator::create(Instruction::And, Or,
1130 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
1133 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1134 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
1135 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1136 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1137 Instruction *Or = BinaryOperator::create(Instruction::Or,
1138 Op0I->getOperand(0), RHS,
1140 InsertNewInstBefore(Or, I);
1141 return BinaryOperator::create(Instruction::Xor, Or,
1142 ConstantExpr::get(Instruction::And, Op0CI,
1148 // (A & C1)|(A & C2) == A & (C1|C2)
1149 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
1150 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
1151 if (LHS->getOperand(0) == RHS->getOperand(0))
1152 if (Constant *C0 = dyn_castMaskingAnd(LHS))
1153 if (Constant *C1 = dyn_castMaskingAnd(RHS))
1154 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
1155 ConstantExpr::get(Instruction::Or, C0, C1));
1157 Value *Op0NotVal = dyn_castNotVal(Op0);
1158 Value *Op1NotVal = dyn_castNotVal(Op1);
1160 if (Op1 == Op0NotVal) // ~A | A == -1
1161 return ReplaceInstUsesWith(I,
1162 ConstantIntegral::getAllOnesValue(I.getType()));
1164 if (Op0 == Op1NotVal) // A | ~A == -1
1165 return ReplaceInstUsesWith(I,
1166 ConstantIntegral::getAllOnesValue(I.getType()));
1168 // (~A | ~B) == (~(A & B)) - Demorgan's Law
1169 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1170 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
1171 Op1NotVal,I.getName()+".demorgan",
1173 WorkList.push_back(And);
1174 return BinaryOperator::createNot(And);
1177 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1178 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1179 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1182 return Changed ? &I : 0;
1185 // XorSelf - Implements: X ^ X --> 0
1188 XorSelf(Value *rhs) : RHS(rhs) {}
1189 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1190 Instruction *apply(BinaryOperator &Xor) const {
1196 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1197 bool Changed = SimplifyCommutative(I);
1198 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1200 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1201 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1202 assert(Result == &I && "AssociativeOpt didn't work?");
1203 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1206 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1208 if (RHS->isNullValue())
1209 return ReplaceInstUsesWith(I, Op0);
1211 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1212 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1213 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1214 if (RHS == ConstantBool::True && SCI->hasOneUse())
1215 return new SetCondInst(SCI->getInverseCondition(),
1216 SCI->getOperand(0), SCI->getOperand(1));
1218 // ~(c-X) == X-c-1 == X+(-c-1)
1219 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1220 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1221 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1222 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1223 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1224 ConstantInt::get(I.getType(), 1));
1225 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1229 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1230 switch (Op0I->getOpcode()) {
1231 case Instruction::Add:
1232 // ~(X-c) --> (-c-1)-X
1233 if (RHS->isAllOnesValue()) {
1234 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1235 Constant::getNullValue(Op0CI->getType()), Op0CI);
1236 return BinaryOperator::create(Instruction::Sub,
1237 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1238 ConstantInt::get(I.getType(), 1)),
1239 Op0I->getOperand(0));
1242 case Instruction::And:
1243 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1244 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1245 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1247 case Instruction::Or:
1248 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1249 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1250 return BinaryOperator::create(Instruction::And, Op0,
1258 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1260 return ReplaceInstUsesWith(I,
1261 ConstantIntegral::getAllOnesValue(I.getType()));
1263 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1265 return ReplaceInstUsesWith(I,
1266 ConstantIntegral::getAllOnesValue(I.getType()));
1268 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1269 if (Op1I->getOpcode() == Instruction::Or) {
1270 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1271 cast<BinaryOperator>(Op1I)->swapOperands();
1273 std::swap(Op0, Op1);
1274 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1276 std::swap(Op0, Op1);
1278 } else if (Op1I->getOpcode() == Instruction::Xor) {
1279 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1280 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1281 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1282 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1285 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1286 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1287 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1288 cast<BinaryOperator>(Op0I)->swapOperands();
1289 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1290 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1291 WorkList.push_back(cast<Instruction>(NotB));
1292 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1295 } else if (Op0I->getOpcode() == Instruction::Xor) {
1296 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1297 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1298 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1299 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1302 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1303 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1304 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1305 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1306 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1308 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1309 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1310 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1313 return Changed ? &I : 0;
1316 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1317 static Constant *AddOne(ConstantInt *C) {
1318 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1319 ConstantInt::get(C->getType(), 1));
1320 assert(Result && "Constant folding integer addition failed!");
1323 static Constant *SubOne(ConstantInt *C) {
1324 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1325 ConstantInt::get(C->getType(), 1));
1326 assert(Result && "Constant folding integer addition failed!");
1330 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1331 // true when both operands are equal...
1333 static bool isTrueWhenEqual(Instruction &I) {
1334 return I.getOpcode() == Instruction::SetEQ ||
1335 I.getOpcode() == Instruction::SetGE ||
1336 I.getOpcode() == Instruction::SetLE;
1339 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1340 bool Changed = SimplifyCommutative(I);
1341 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1342 const Type *Ty = Op0->getType();
1346 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1348 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1349 if (isa<ConstantPointerNull>(Op1) &&
1350 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1351 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1354 // setcc's with boolean values can always be turned into bitwise operations
1355 if (Ty == Type::BoolTy) {
1356 // If this is <, >, or !=, we can change this into a simple xor instruction
1357 if (!isTrueWhenEqual(I))
1358 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1360 // Otherwise we need to make a temporary intermediate instruction and insert
1361 // it into the instruction stream. This is what we are after:
1363 // seteq bool %A, %B -> ~(A^B)
1364 // setle bool %A, %B -> ~A | B
1365 // setge bool %A, %B -> A | ~B
1367 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1368 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1370 InsertNewInstBefore(Xor, I);
1371 return BinaryOperator::createNot(Xor);
1374 // Handle the setXe cases...
1375 assert(I.getOpcode() == Instruction::SetGE ||
1376 I.getOpcode() == Instruction::SetLE);
1378 if (I.getOpcode() == Instruction::SetGE)
1379 std::swap(Op0, Op1); // Change setge -> setle
1381 // Now we just have the SetLE case.
1382 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1383 InsertNewInstBefore(Not, I);
1384 return BinaryOperator::create(Instruction::Or, Not, Op1);
1387 // Check to see if we are doing one of many comparisons against constant
1388 // integers at the end of their ranges...
1390 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1391 // Simplify seteq and setne instructions...
1392 if (I.getOpcode() == Instruction::SetEQ ||
1393 I.getOpcode() == Instruction::SetNE) {
1394 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1396 // If the first operand is (and|or|xor) with a constant, and the second
1397 // operand is a constant, simplify a bit.
1398 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1399 switch (BO->getOpcode()) {
1400 case Instruction::Add:
1401 if (CI->isNullValue()) {
1402 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1403 // efficiently invertible, or if the add has just this one use.
1404 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1405 if (Value *NegVal = dyn_castNegVal(BOp1))
1406 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1407 else if (Value *NegVal = dyn_castNegVal(BOp0))
1408 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1409 else if (BO->hasOneUse()) {
1410 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1412 InsertNewInstBefore(Neg, I);
1413 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1417 case Instruction::Xor:
1418 // For the xor case, we can xor two constants together, eliminating
1419 // the explicit xor.
1420 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1421 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1422 ConstantExpr::get(Instruction::Xor, CI, BOC));
1425 case Instruction::Sub:
1426 // Replace (([sub|xor] A, B) != 0) with (A != B)
1427 if (CI->isNullValue())
1428 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1432 case Instruction::Or:
1433 // If bits are being or'd in that are not present in the constant we
1434 // are comparing against, then the comparison could never succeed!
1435 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1436 Constant *NotCI = NotConstant(CI);
1437 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1438 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1442 case Instruction::And:
1443 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1444 // If bits are being compared against that are and'd out, then the
1445 // comparison can never succeed!
1446 if (!ConstantExpr::get(Instruction::And, CI,
1447 NotConstant(BOC))->isNullValue())
1448 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1450 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1451 // to be a signed value as appropriate.
1452 if (isSignBit(BOC)) {
1453 Value *X = BO->getOperand(0);
1454 // If 'X' is not signed, insert a cast now...
1455 if (!BOC->getType()->isSigned()) {
1456 const Type *DestTy = getSignedIntegralType(BOC->getType());
1457 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1458 InsertNewInstBefore(NewCI, I);
1461 return new SetCondInst(isSetNE ? Instruction::SetLT :
1462 Instruction::SetGE, X,
1463 Constant::getNullValue(X->getType()));
1469 } else { // Not a SetEQ/SetNE
1470 // If the LHS is a cast from an integral value of the same size,
1471 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
1472 Value *CastOp = Cast->getOperand(0);
1473 const Type *SrcTy = CastOp->getType();
1474 unsigned SrcTySize = SrcTy->getPrimitiveSize();
1475 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
1476 SrcTySize == Cast->getType()->getPrimitiveSize()) {
1477 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
1478 "Source and destination signednesses should differ!");
1479 if (Cast->getType()->isSigned()) {
1480 // If this is a signed comparison, check for comparisons in the
1481 // vicinity of zero.
1482 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
1484 return BinaryOperator::create(Instruction::SetGT, CastOp,
1485 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
1486 else if (I.getOpcode() == Instruction::SetGT &&
1487 cast<ConstantSInt>(CI)->getValue() == -1)
1488 // X > -1 => x < 128
1489 return BinaryOperator::create(Instruction::SetLT, CastOp,
1490 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
1492 ConstantUInt *CUI = cast<ConstantUInt>(CI);
1493 if (I.getOpcode() == Instruction::SetLT &&
1494 CUI->getValue() == 1ULL << (SrcTySize*8-1))
1495 // X < 128 => X > -1
1496 return BinaryOperator::create(Instruction::SetGT, CastOp,
1497 ConstantSInt::get(SrcTy, -1));
1498 else if (I.getOpcode() == Instruction::SetGT &&
1499 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
1501 return BinaryOperator::create(Instruction::SetLT, CastOp,
1502 Constant::getNullValue(SrcTy));
1508 // Check to see if we are comparing against the minimum or maximum value...
1509 if (CI->isMinValue()) {
1510 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1511 return ReplaceInstUsesWith(I, ConstantBool::False);
1512 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1513 return ReplaceInstUsesWith(I, ConstantBool::True);
1514 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1515 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1516 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1517 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1519 } else if (CI->isMaxValue()) {
1520 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1521 return ReplaceInstUsesWith(I, ConstantBool::False);
1522 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1523 return ReplaceInstUsesWith(I, ConstantBool::True);
1524 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1525 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1526 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1527 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1529 // Comparing against a value really close to min or max?
1530 } else if (isMinValuePlusOne(CI)) {
1531 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1532 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1533 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1534 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1536 } else if (isMaxValueMinusOne(CI)) {
1537 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1538 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1539 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1540 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1543 // If we still have a setle or setge instruction, turn it into the
1544 // appropriate setlt or setgt instruction. Since the border cases have
1545 // already been handled above, this requires little checking.
1547 if (I.getOpcode() == Instruction::SetLE)
1548 return BinaryOperator::create(Instruction::SetLT, Op0, AddOne(CI));
1549 if (I.getOpcode() == Instruction::SetGE)
1550 return BinaryOperator::create(Instruction::SetGT, Op0, SubOne(CI));
1553 // Test to see if the operands of the setcc are casted versions of other
1554 // values. If the cast can be stripped off both arguments, we do so now.
1555 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1556 Value *CastOp0 = CI->getOperand(0);
1557 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1558 (isa<Constant>(Op1) || isa<CastInst>(Op1)) &&
1559 (I.getOpcode() == Instruction::SetEQ ||
1560 I.getOpcode() == Instruction::SetNE)) {
1561 // We keep moving the cast from the left operand over to the right
1562 // operand, where it can often be eliminated completely.
1565 // If operand #1 is a cast instruction, see if we can eliminate it as
1567 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1568 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1570 Op1 = CI2->getOperand(0);
1572 // If Op1 is a constant, we can fold the cast into the constant.
1573 if (Op1->getType() != Op0->getType())
1574 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1575 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1577 // Otherwise, cast the RHS right before the setcc
1578 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1579 InsertNewInstBefore(cast<Instruction>(Op1), I);
1581 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1584 // Handle the special case of: setcc (cast bool to X), <cst>
1585 // This comes up when you have code like
1588 // For generality, we handle any zero-extension of any operand comparison
1590 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1591 const Type *SrcTy = CastOp0->getType();
1592 const Type *DestTy = Op0->getType();
1593 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1594 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1595 // Ok, we have an expansion of operand 0 into a new type. Get the
1596 // constant value, masink off bits which are not set in the RHS. These
1597 // could be set if the destination value is signed.
1598 uint64_t ConstVal = ConstantRHS->getRawValue();
1599 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1601 // If the constant we are comparing it with has high bits set, which
1602 // don't exist in the original value, the values could never be equal,
1603 // because the source would be zero extended.
1605 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1606 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1607 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1608 switch (I.getOpcode()) {
1609 default: assert(0 && "Unknown comparison type!");
1610 case Instruction::SetEQ:
1611 return ReplaceInstUsesWith(I, ConstantBool::False);
1612 case Instruction::SetNE:
1613 return ReplaceInstUsesWith(I, ConstantBool::True);
1614 case Instruction::SetLT:
1615 case Instruction::SetLE:
1616 if (DestTy->isSigned() && HasSignBit)
1617 return ReplaceInstUsesWith(I, ConstantBool::False);
1618 return ReplaceInstUsesWith(I, ConstantBool::True);
1619 case Instruction::SetGT:
1620 case Instruction::SetGE:
1621 if (DestTy->isSigned() && HasSignBit)
1622 return ReplaceInstUsesWith(I, ConstantBool::True);
1623 return ReplaceInstUsesWith(I, ConstantBool::False);
1627 // Otherwise, we can replace the setcc with a setcc of the smaller
1629 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1630 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1634 return Changed ? &I : 0;
1639 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1640 assert(I.getOperand(1)->getType() == Type::UByteTy);
1641 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1642 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1644 // shl X, 0 == X and shr X, 0 == X
1645 // shl 0, X == 0 and shr 0, X == 0
1646 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1647 Op0 == Constant::getNullValue(Op0->getType()))
1648 return ReplaceInstUsesWith(I, Op0);
1650 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1652 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1653 if (CSI->isAllOnesValue())
1654 return ReplaceInstUsesWith(I, CSI);
1656 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1657 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1658 // of a signed value.
1660 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1661 if (CUI->getValue() >= TypeBits) {
1662 if (!Op0->getType()->isSigned() || isLeftShift)
1663 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1665 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
1670 // ((X*C1) << C2) == (X * (C1 << C2))
1671 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1672 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1673 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1674 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1675 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1678 // If the operand is an bitwise operator with a constant RHS, and the
1679 // shift is the only use, we can pull it out of the shift.
1680 if (Op0->hasOneUse())
1681 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1682 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1683 bool isValid = true; // Valid only for And, Or, Xor
1684 bool highBitSet = false; // Transform if high bit of constant set?
1686 switch (Op0BO->getOpcode()) {
1687 default: isValid = false; break; // Do not perform transform!
1688 case Instruction::Or:
1689 case Instruction::Xor:
1692 case Instruction::And:
1697 // If this is a signed shift right, and the high bit is modified
1698 // by the logical operation, do not perform the transformation.
1699 // The highBitSet boolean indicates the value of the high bit of
1700 // the constant which would cause it to be modified for this
1703 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1704 uint64_t Val = Op0C->getRawValue();
1705 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1709 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1711 Instruction *NewShift =
1712 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1715 InsertNewInstBefore(NewShift, I);
1717 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1722 // If this is a shift of a shift, see if we can fold the two together...
1723 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1724 if (ConstantUInt *ShiftAmt1C =
1725 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1726 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1727 unsigned ShiftAmt2 = CUI->getValue();
1729 // Check for (A << c1) << c2 and (A >> c1) >> c2
1730 if (I.getOpcode() == Op0SI->getOpcode()) {
1731 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1732 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
1733 Amt = Op0->getType()->getPrimitiveSize()*8;
1734 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1735 ConstantUInt::get(Type::UByteTy, Amt));
1738 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1739 // signed types, we can only support the (A >> c1) << c2 configuration,
1740 // because it can not turn an arbitrary bit of A into a sign bit.
1741 if (I.getType()->isUnsigned() || isLeftShift) {
1742 // Calculate bitmask for what gets shifted off the edge...
1743 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1745 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1747 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1750 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1751 C, Op0SI->getOperand(0)->getName()+".mask");
1752 InsertNewInstBefore(Mask, I);
1754 // Figure out what flavor of shift we should use...
1755 if (ShiftAmt1 == ShiftAmt2)
1756 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1757 else if (ShiftAmt1 < ShiftAmt2) {
1758 return new ShiftInst(I.getOpcode(), Mask,
1759 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1761 return new ShiftInst(Op0SI->getOpcode(), Mask,
1762 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1772 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1775 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1776 const Type *DstTy) {
1778 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1779 // are identical and the bits don't get reinterpreted (for example
1780 // int->float->int would not be allowed)
1781 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1784 // Allow free casting and conversion of sizes as long as the sign doesn't
1786 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1787 unsigned SrcSize = SrcTy->getPrimitiveSize();
1788 unsigned MidSize = MidTy->getPrimitiveSize();
1789 unsigned DstSize = DstTy->getPrimitiveSize();
1791 // Cases where we are monotonically decreasing the size of the type are
1792 // always ok, regardless of what sign changes are going on.
1794 if (SrcSize >= MidSize && MidSize >= DstSize)
1797 // Cases where the source and destination type are the same, but the middle
1798 // type is bigger are noops.
1800 if (SrcSize == DstSize && MidSize > SrcSize)
1803 // If we are monotonically growing, things are more complex.
1805 if (SrcSize <= MidSize && MidSize <= DstSize) {
1806 // We have eight combinations of signedness to worry about. Here's the
1808 static const int SignTable[8] = {
1809 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1810 1, // U U U Always ok
1811 1, // U U S Always ok
1812 3, // U S U Ok iff SrcSize != MidSize
1813 3, // U S S Ok iff SrcSize != MidSize
1814 0, // S U U Never ok
1815 2, // S U S Ok iff MidSize == DstSize
1816 1, // S S U Always ok
1817 1, // S S S Always ok
1820 // Choose an action based on the current entry of the signtable that this
1821 // cast of cast refers to...
1822 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1823 switch (SignTable[Row]) {
1824 case 0: return false; // Never ok
1825 case 1: return true; // Always ok
1826 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1827 case 3: // Ok iff SrcSize != MidSize
1828 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1829 default: assert(0 && "Bad entry in sign table!");
1834 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1835 // like: short -> ushort -> uint, because this can create wrong results if
1836 // the input short is negative!
1841 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1842 if (V->getType() == Ty || isa<Constant>(V)) return false;
1843 if (const CastInst *CI = dyn_cast<CastInst>(V))
1844 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1849 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1850 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1851 /// casts that are known to not do anything...
1853 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1854 Instruction *InsertBefore) {
1855 if (V->getType() == DestTy) return V;
1856 if (Constant *C = dyn_cast<Constant>(V))
1857 return ConstantExpr::getCast(C, DestTy);
1859 CastInst *CI = new CastInst(V, DestTy, V->getName());
1860 InsertNewInstBefore(CI, *InsertBefore);
1864 // CastInst simplification
1866 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1867 Value *Src = CI.getOperand(0);
1869 // If the user is casting a value to the same type, eliminate this cast
1871 if (CI.getType() == Src->getType())
1872 return ReplaceInstUsesWith(CI, Src);
1874 // If casting the result of another cast instruction, try to eliminate this
1877 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1878 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1879 CSrc->getType(), CI.getType())) {
1880 // This instruction now refers directly to the cast's src operand. This
1881 // has a good chance of making CSrc dead.
1882 CI.setOperand(0, CSrc->getOperand(0));
1886 // If this is an A->B->A cast, and we are dealing with integral types, try
1887 // to convert this into a logical 'and' instruction.
1889 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1890 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1891 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1892 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1893 assert(CSrc->getType() != Type::ULongTy &&
1894 "Cannot have type bigger than ulong!");
1895 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1896 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1897 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1902 // If casting the result of a getelementptr instruction with no offset, turn
1903 // this into a cast of the original pointer!
1905 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1906 bool AllZeroOperands = true;
1907 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1908 if (!isa<Constant>(GEP->getOperand(i)) ||
1909 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1910 AllZeroOperands = false;
1913 if (AllZeroOperands) {
1914 CI.setOperand(0, GEP->getOperand(0));
1919 // If we are casting a malloc or alloca to a pointer to a type of the same
1920 // size, rewrite the allocation instruction to allocate the "right" type.
1922 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1923 if (AI->hasOneUse() && !AI->isArrayAllocation())
1924 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1925 // Get the type really allocated and the type casted to...
1926 const Type *AllocElTy = AI->getAllocatedType();
1927 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1928 const Type *CastElTy = PTy->getElementType();
1929 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1931 // If the allocation is for an even multiple of the cast type size
1932 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1933 Value *Amt = ConstantUInt::get(Type::UIntTy,
1934 AllocElTySize/CastElTySize);
1935 std::string Name = AI->getName(); AI->setName("");
1936 AllocationInst *New;
1937 if (isa<MallocInst>(AI))
1938 New = new MallocInst(CastElTy, Amt, Name);
1940 New = new AllocaInst(CastElTy, Amt, Name);
1941 InsertNewInstBefore(New, CI);
1942 return ReplaceInstUsesWith(CI, New);
1946 // If the source value is an instruction with only this use, we can attempt to
1947 // propagate the cast into the instruction. Also, only handle integral types
1949 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1950 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1951 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1952 const Type *DestTy = CI.getType();
1953 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1954 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1956 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1957 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1959 switch (SrcI->getOpcode()) {
1960 case Instruction::Add:
1961 case Instruction::Mul:
1962 case Instruction::And:
1963 case Instruction::Or:
1964 case Instruction::Xor:
1965 // If we are discarding information, or just changing the sign, rewrite.
1966 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1967 // Don't insert two casts if they cannot be eliminated. We allow two
1968 // casts to be inserted if the sizes are the same. This could only be
1969 // converting signedness, which is a noop.
1970 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1971 !ValueRequiresCast(Op0, DestTy)) {
1972 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1973 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1974 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1975 ->getOpcode(), Op0c, Op1c);
1979 case Instruction::Shl:
1980 // Allow changing the sign of the source operand. Do not allow changing
1981 // the size of the shift, UNLESS the shift amount is a constant. We
1982 // mush not change variable sized shifts to a smaller size, because it
1983 // is undefined to shift more bits out than exist in the value.
1984 if (DestBitSize == SrcBitSize ||
1985 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1986 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1987 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1996 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
1997 if (ConstantBool *C = dyn_cast<ConstantBool>(SI.getCondition()))
1998 if (C == ConstantBool::True)
1999 return ReplaceInstUsesWith(SI, SI.getTrueValue());
2001 assert(C == ConstantBool::False);
2002 return ReplaceInstUsesWith(SI, SI.getFalseValue());
2004 // Other transformations are possible!
2010 // CallInst simplification
2012 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
2013 // Intrinsics cannot occur in an invoke, so handle them here instead of in
2015 if (Function *F = CI.getCalledFunction())
2016 switch (F->getIntrinsicID()) {
2017 case Intrinsic::memmove:
2018 case Intrinsic::memcpy:
2019 case Intrinsic::memset:
2020 // memmove/cpy/set of zero bytes is a noop.
2021 if (Constant *NumBytes = dyn_cast<Constant>(CI.getOperand(3))) {
2022 if (NumBytes->isNullValue())
2023 return EraseInstFromFunction(CI);
2030 return visitCallSite(&CI);
2033 // InvokeInst simplification
2035 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
2036 return visitCallSite(&II);
2039 // visitCallSite - Improvements for call and invoke instructions.
2041 Instruction *InstCombiner::visitCallSite(CallSite CS) {
2042 bool Changed = false;
2044 // If the callee is a constexpr cast of a function, attempt to move the cast
2045 // to the arguments of the call/invoke.
2046 if (transformConstExprCastCall(CS)) return 0;
2048 Value *Callee = CS.getCalledValue();
2049 const PointerType *PTy = cast<PointerType>(Callee->getType());
2050 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
2051 if (FTy->isVarArg()) {
2052 // See if we can optimize any arguments passed through the varargs area of
2054 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
2055 E = CS.arg_end(); I != E; ++I)
2056 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
2057 // If this cast does not effect the value passed through the varargs
2058 // area, we can eliminate the use of the cast.
2059 Value *Op = CI->getOperand(0);
2060 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
2067 return Changed ? CS.getInstruction() : 0;
2070 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
2071 // attempt to move the cast to the arguments of the call/invoke.
2073 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
2074 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
2075 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
2076 if (CE->getOpcode() != Instruction::Cast ||
2077 !isa<ConstantPointerRef>(CE->getOperand(0)))
2079 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
2080 if (!isa<Function>(CPR->getValue())) return false;
2081 Function *Callee = cast<Function>(CPR->getValue());
2082 Instruction *Caller = CS.getInstruction();
2084 // Okay, this is a cast from a function to a different type. Unless doing so
2085 // would cause a type conversion of one of our arguments, change this call to
2086 // be a direct call with arguments casted to the appropriate types.
2088 const FunctionType *FT = Callee->getFunctionType();
2089 const Type *OldRetTy = Caller->getType();
2091 // Check to see if we are changing the return type...
2092 if (OldRetTy != FT->getReturnType()) {
2093 if (Callee->isExternal() &&
2094 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
2095 !Caller->use_empty())
2096 return false; // Cannot transform this return value...
2098 // If the callsite is an invoke instruction, and the return value is used by
2099 // a PHI node in a successor, we cannot change the return type of the call
2100 // because there is no place to put the cast instruction (without breaking
2101 // the critical edge). Bail out in this case.
2102 if (!Caller->use_empty())
2103 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
2104 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
2106 if (PHINode *PN = dyn_cast<PHINode>(*UI))
2107 if (PN->getParent() == II->getNormalDest() ||
2108 PN->getParent() == II->getUnwindDest())
2112 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
2113 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
2115 CallSite::arg_iterator AI = CS.arg_begin();
2116 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
2117 const Type *ParamTy = FT->getParamType(i);
2118 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
2119 if (Callee->isExternal() && !isConvertible) return false;
2122 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
2123 Callee->isExternal())
2124 return false; // Do not delete arguments unless we have a function body...
2126 // Okay, we decided that this is a safe thing to do: go ahead and start
2127 // inserting cast instructions as necessary...
2128 std::vector<Value*> Args;
2129 Args.reserve(NumActualArgs);
2131 AI = CS.arg_begin();
2132 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
2133 const Type *ParamTy = FT->getParamType(i);
2134 if ((*AI)->getType() == ParamTy) {
2135 Args.push_back(*AI);
2137 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
2138 InsertNewInstBefore(Cast, *Caller);
2139 Args.push_back(Cast);
2143 // If the function takes more arguments than the call was taking, add them
2145 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
2146 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
2148 // If we are removing arguments to the function, emit an obnoxious warning...
2149 if (FT->getNumParams() < NumActualArgs)
2150 if (!FT->isVarArg()) {
2151 std::cerr << "WARNING: While resolving call to function '"
2152 << Callee->getName() << "' arguments were dropped!\n";
2154 // Add all of the arguments in their promoted form to the arg list...
2155 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
2156 const Type *PTy = getPromotedType((*AI)->getType());
2157 if (PTy != (*AI)->getType()) {
2158 // Must promote to pass through va_arg area!
2159 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
2160 InsertNewInstBefore(Cast, *Caller);
2161 Args.push_back(Cast);
2163 Args.push_back(*AI);
2168 if (FT->getReturnType() == Type::VoidTy)
2169 Caller->setName(""); // Void type should not have a name...
2172 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2173 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
2174 Args, Caller->getName(), Caller);
2176 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
2179 // Insert a cast of the return type as necessary...
2181 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
2182 if (NV->getType() != Type::VoidTy) {
2183 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
2185 // If this is an invoke instruction, we should insert it after the first
2186 // non-phi, instruction in the normal successor block.
2187 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2188 BasicBlock::iterator I = II->getNormalDest()->begin();
2189 while (isa<PHINode>(I)) ++I;
2190 InsertNewInstBefore(NC, *I);
2192 // Otherwise, it's a call, just insert cast right after the call instr
2193 InsertNewInstBefore(NC, *Caller);
2195 AddUsersToWorkList(*Caller);
2197 NV = Constant::getNullValue(Caller->getType());
2201 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
2202 Caller->replaceAllUsesWith(NV);
2203 Caller->getParent()->getInstList().erase(Caller);
2204 removeFromWorkList(Caller);
2210 // PHINode simplification
2212 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2213 if (Value *V = hasConstantValue(&PN))
2214 return ReplaceInstUsesWith(PN, V);
2216 // If the only user of this instruction is a cast instruction, and all of the
2217 // incoming values are constants, change this PHI to merge together the casted
2220 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2221 if (CI->getType() != PN.getType()) { // noop casts will be folded
2222 bool AllConstant = true;
2223 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2224 if (!isa<Constant>(PN.getIncomingValue(i))) {
2225 AllConstant = false;
2229 // Make a new PHI with all casted values.
2230 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2231 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2232 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2233 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2234 PN.getIncomingBlock(i));
2237 // Update the cast instruction.
2238 CI->setOperand(0, New);
2239 WorkList.push_back(CI); // revisit the cast instruction to fold.
2240 WorkList.push_back(New); // Make sure to revisit the new Phi
2241 return &PN; // PN is now dead!
2248 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2249 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2250 // If so, eliminate the noop.
2251 if (GEP.getNumOperands() == 1)
2252 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2254 bool HasZeroPointerIndex = false;
2255 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2256 HasZeroPointerIndex = C->isNullValue();
2258 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2259 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2261 // Combine Indices - If the source pointer to this getelementptr instruction
2262 // is a getelementptr instruction, combine the indices of the two
2263 // getelementptr instructions into a single instruction.
2265 std::vector<Value*> SrcGEPOperands;
2266 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
2267 SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
2268 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2269 if (CE->getOpcode() == Instruction::GetElementPtr)
2270 SrcGEPOperands.assign(CE->op_begin(), CE->op_end());
2273 if (!SrcGEPOperands.empty()) {
2274 std::vector<Value *> Indices;
2276 // Can we combine the two pointer arithmetics offsets?
2277 if (SrcGEPOperands.size() == 2 && isa<Constant>(SrcGEPOperands[1]) &&
2278 isa<Constant>(GEP.getOperand(1))) {
2279 // Replace: gep (gep %P, long C1), long C2, ...
2280 // With: gep %P, long (C1+C2), ...
2281 Value *Sum = ConstantExpr::get(Instruction::Add,
2282 cast<Constant>(SrcGEPOperands[1]),
2283 cast<Constant>(GEP.getOperand(1)));
2284 assert(Sum && "Constant folding of longs failed!?");
2285 GEP.setOperand(0, SrcGEPOperands[0]);
2286 GEP.setOperand(1, Sum);
2287 if (Instruction *I = dyn_cast<Instruction>(GEP.getOperand(0)))
2288 AddUsersToWorkList(*I); // Reduce use count of Src
2290 } else if (SrcGEPOperands.size() == 2) {
2291 // Replace: gep (gep %P, long B), long A, ...
2292 // With: T = long A+B; gep %P, T, ...
2294 // Note that if our source is a gep chain itself that we wait for that
2295 // chain to be resolved before we perform this transformation. This
2296 // avoids us creating a TON of code in some cases.
2298 if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
2299 cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
2300 return 0; // Wait until our source is folded to completion.
2302 Value *Sum = BinaryOperator::create(Instruction::Add, SrcGEPOperands[1],
2304 GEP.getOperand(0)->getName()+".sum",
2306 GEP.setOperand(0, SrcGEPOperands[0]);
2307 GEP.setOperand(1, Sum);
2308 WorkList.push_back(cast<Instruction>(Sum));
2310 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
2311 SrcGEPOperands.size() != 1) {
2312 // Otherwise we can do the fold if the first index of the GEP is a zero
2313 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2314 SrcGEPOperands.end());
2315 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2316 } else if (SrcGEPOperands.back() == Constant::getNullValue(Type::LongTy)) {
2317 // FIXME: when we allow indices to be non-long values, support this for
2320 // If the src gep ends with a constant array index, merge this get into
2321 // it, even if we have a non-zero array index.
2322 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2323 SrcGEPOperands.end()-1);
2324 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
2327 if (!Indices.empty())
2328 return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
2330 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
2331 // GEP of global variable. If all of the indices for this GEP are
2332 // constants, we can promote this to a constexpr instead of an instruction.
2334 // Scan for nonconstants...
2335 std::vector<Constant*> Indices;
2336 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2337 for (; I != E && isa<Constant>(*I); ++I)
2338 Indices.push_back(cast<Constant>(*I));
2340 if (I == E) { // If they are all constants...
2342 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2344 // Replace all uses of the GEP with the new constexpr...
2345 return ReplaceInstUsesWith(GEP, CE);
2347 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2348 if (CE->getOpcode() == Instruction::Cast) {
2349 if (HasZeroPointerIndex) {
2350 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2351 // into : GEP [10 x ubyte]* X, long 0, ...
2353 // This occurs when the program declares an array extern like "int X[];"
2355 Constant *X = CE->getOperand(0);
2356 const PointerType *CPTy = cast<PointerType>(CE->getType());
2357 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2358 if (const ArrayType *XATy =
2359 dyn_cast<ArrayType>(XTy->getElementType()))
2360 if (const ArrayType *CATy =
2361 dyn_cast<ArrayType>(CPTy->getElementType()))
2362 if (CATy->getElementType() == XATy->getElementType()) {
2363 // At this point, we know that the cast source type is a pointer
2364 // to an array of the same type as the destination pointer
2365 // array. Because the array type is never stepped over (there
2366 // is a leading zero) we can fold the cast into this GEP.
2367 GEP.setOperand(0, X);
2377 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2378 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2379 if (AI.isArrayAllocation()) // Check C != 1
2380 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2381 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2382 AllocationInst *New = 0;
2384 // Create and insert the replacement instruction...
2385 if (isa<MallocInst>(AI))
2386 New = new MallocInst(NewTy, 0, AI.getName());
2388 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2389 New = new AllocaInst(NewTy, 0, AI.getName());
2392 InsertNewInstBefore(New, AI);
2394 // Scan to the end of the allocation instructions, to skip over a block of
2395 // allocas if possible...
2397 BasicBlock::iterator It = New;
2398 while (isa<AllocationInst>(*It)) ++It;
2400 // Now that I is pointing to the first non-allocation-inst in the block,
2401 // insert our getelementptr instruction...
2403 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
2404 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2406 // Now make everything use the getelementptr instead of the original
2408 return ReplaceInstUsesWith(AI, V);
2411 // If alloca'ing a zero byte object, replace the alloca with a null pointer.
2412 // Note that we only do this for alloca's, because malloc should allocate and
2413 // return a unique pointer, even for a zero byte allocation.
2414 if (isa<AllocaInst>(AI) && TD->getTypeSize(AI.getAllocatedType()) == 0)
2415 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
2420 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2421 Value *Op = FI.getOperand(0);
2423 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2424 if (CastInst *CI = dyn_cast<CastInst>(Op))
2425 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2426 FI.setOperand(0, CI->getOperand(0));
2430 // If we have 'free null' delete the instruction. This can happen in stl code
2431 // when lots of inlining happens.
2432 if (isa<ConstantPointerNull>(Op))
2433 return EraseInstFromFunction(FI);
2439 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2440 /// constantexpr, return the constant value being addressed by the constant
2441 /// expression, or null if something is funny.
2443 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2444 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
2445 return 0; // Do not allow stepping over the value!
2447 // Loop over all of the operands, tracking down which value we are
2449 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2450 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2451 ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
2452 if (CS == 0) return 0;
2453 if (CU->getValue() >= CS->getValues().size()) return 0;
2454 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2455 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2456 ConstantArray *CA = dyn_cast<ConstantArray>(C);
2457 if (CA == 0) return 0;
2458 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2459 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2465 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2466 Value *Op = LI.getOperand(0);
2467 if (LI.isVolatile()) return 0;
2469 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2470 Op = CPR->getValue();
2472 // Instcombine load (constant global) into the value loaded...
2473 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2474 if (GV->isConstant() && !GV->isExternal())
2475 return ReplaceInstUsesWith(LI, GV->getInitializer());
2477 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2478 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2479 if (CE->getOpcode() == Instruction::GetElementPtr)
2480 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2481 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2482 if (GV->isConstant() && !GV->isExternal())
2483 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2484 return ReplaceInstUsesWith(LI, V);
2489 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2490 // Change br (not X), label True, label False to: br X, label False, True
2491 if (BI.isConditional() && !isa<Constant>(BI.getCondition())) {
2492 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2493 BasicBlock *TrueDest = BI.getSuccessor(0);
2494 BasicBlock *FalseDest = BI.getSuccessor(1);
2495 // Swap Destinations and condition...
2497 BI.setSuccessor(0, FalseDest);
2498 BI.setSuccessor(1, TrueDest);
2500 } else if (SetCondInst *I = dyn_cast<SetCondInst>(BI.getCondition())) {
2501 // Cannonicalize setne -> seteq
2502 if ((I->getOpcode() == Instruction::SetNE ||
2503 I->getOpcode() == Instruction::SetLE ||
2504 I->getOpcode() == Instruction::SetGE) && I->hasOneUse()) {
2505 std::string Name = I->getName(); I->setName("");
2506 Instruction::BinaryOps NewOpcode =
2507 SetCondInst::getInverseCondition(I->getOpcode());
2508 Value *NewSCC = BinaryOperator::create(NewOpcode, I->getOperand(0),
2509 I->getOperand(1), Name, I);
2510 BasicBlock *TrueDest = BI.getSuccessor(0);
2511 BasicBlock *FalseDest = BI.getSuccessor(1);
2512 // Swap Destinations and condition...
2513 BI.setCondition(NewSCC);
2514 BI.setSuccessor(0, FalseDest);
2515 BI.setSuccessor(1, TrueDest);
2516 removeFromWorkList(I);
2517 I->getParent()->getInstList().erase(I);
2518 WorkList.push_back(cast<Instruction>(NewSCC));
2527 void InstCombiner::removeFromWorkList(Instruction *I) {
2528 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2532 bool InstCombiner::runOnFunction(Function &F) {
2533 bool Changed = false;
2534 TD = &getAnalysis<TargetData>();
2536 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2538 while (!WorkList.empty()) {
2539 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2540 WorkList.pop_back();
2542 // Check to see if we can DCE or ConstantPropagate the instruction...
2543 // Check to see if we can DIE the instruction...
2544 if (isInstructionTriviallyDead(I)) {
2545 // Add operands to the worklist...
2546 if (I->getNumOperands() < 4)
2547 AddUsesToWorkList(*I);
2550 I->getParent()->getInstList().erase(I);
2551 removeFromWorkList(I);
2555 // Instruction isn't dead, see if we can constant propagate it...
2556 if (Constant *C = ConstantFoldInstruction(I)) {
2557 // Add operands to the worklist...
2558 AddUsesToWorkList(*I);
2559 ReplaceInstUsesWith(*I, C);
2562 I->getParent()->getInstList().erase(I);
2563 removeFromWorkList(I);
2567 // Check to see if any of the operands of this instruction are a
2568 // ConstantPointerRef. Since they sneak in all over the place and inhibit
2569 // optimization, we want to strip them out unconditionally!
2570 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2571 if (ConstantPointerRef *CPR =
2572 dyn_cast<ConstantPointerRef>(I->getOperand(i))) {
2573 I->setOperand(i, CPR->getValue());
2577 // Now that we have an instruction, try combining it to simplify it...
2578 if (Instruction *Result = visit(*I)) {
2580 // Should we replace the old instruction with a new one?
2582 DEBUG(std::cerr << "IC: Old = " << *I
2583 << " New = " << *Result);
2585 // Instructions can end up on the worklist more than once. Make sure
2586 // we do not process an instruction that has been deleted.
2587 removeFromWorkList(I);
2589 // Move the name to the new instruction first...
2590 std::string OldName = I->getName(); I->setName("");
2591 Result->setName(OldName);
2593 // Insert the new instruction into the basic block...
2594 BasicBlock *InstParent = I->getParent();
2595 InstParent->getInstList().insert(I, Result);
2597 // Everything uses the new instruction now...
2598 I->replaceAllUsesWith(Result);
2600 // Erase the old instruction.
2601 InstParent->getInstList().erase(I);
2603 DEBUG(std::cerr << "IC: MOD = " << *I);
2605 BasicBlock::iterator II = I;
2607 // If the instruction was modified, it's possible that it is now dead.
2608 // if so, remove it.
2609 if (dceInstruction(II)) {
2610 // Instructions may end up in the worklist more than once. Erase them
2612 removeFromWorkList(I);
2618 WorkList.push_back(Result);
2619 AddUsersToWorkList(*Result);
2628 Pass *llvm::createInstructionCombiningPass() {
2629 return new InstCombiner();