1 //===- InstructionCombining.cpp - Combine multiple instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // InstructionCombining - Combine instructions to form fewer, simple
11 // instructions. This pass does not modify the CFG This pass is where algebraic
12 // simplification happens.
14 // This pass combines things like:
20 // This is a simple worklist driven algorithm.
22 // This pass guarantees that the following canonicalizations are performed on
24 // 1. If a binary operator has a constant operand, it is moved to the RHS
25 // 2. Bitwise operators with constant operands are always grouped so that
26 // shifts are performed first, then or's, then and's, then xor's.
27 // 3. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible
28 // 4. All SetCC instructions on boolean values are replaced with logical ops
29 // 5. add X, X is represented as (X*2) => (X << 1)
30 // 6. Multiplies with a power-of-two constant argument are transformed into
32 // N. This list is incomplete
34 //===----------------------------------------------------------------------===//
36 #include "llvm/Transforms/Scalar.h"
37 #include "llvm/Instructions.h"
38 #include "llvm/Pass.h"
39 #include "llvm/Constants.h"
40 #include "llvm/DerivedTypes.h"
41 #include "llvm/GlobalVariable.h"
42 #include "llvm/Target/TargetData.h"
43 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
44 #include "llvm/Transforms/Utils/Local.h"
45 #include "llvm/Support/InstIterator.h"
46 #include "llvm/Support/InstVisitor.h"
47 #include "llvm/Support/CallSite.h"
48 #include "Support/Statistic.h"
53 Statistic<> NumCombined ("instcombine", "Number of insts combined");
54 Statistic<> NumConstProp("instcombine", "Number of constant folds");
55 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
57 class InstCombiner : public FunctionPass,
58 public InstVisitor<InstCombiner, Instruction*> {
59 // Worklist of all of the instructions that need to be simplified.
60 std::vector<Instruction*> WorkList;
63 void AddUsesToWorkList(Instruction &I) {
64 // The instruction was simplified, add all users of the instruction to
65 // the work lists because they might get more simplified now...
67 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
69 WorkList.push_back(cast<Instruction>(*UI));
72 // removeFromWorkList - remove all instances of I from the worklist.
73 void removeFromWorkList(Instruction *I);
75 virtual bool runOnFunction(Function &F);
77 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
78 AU.addRequired<TargetData>();
82 // Visitation implementation - Implement instruction combining for different
83 // instruction types. The semantics are as follows:
85 // null - No change was made
86 // I - Change was made, I is still valid, I may be dead though
87 // otherwise - Change was made, replace I with returned instruction
89 Instruction *visitAdd(BinaryOperator &I);
90 Instruction *visitSub(BinaryOperator &I);
91 Instruction *visitMul(BinaryOperator &I);
92 Instruction *visitDiv(BinaryOperator &I);
93 Instruction *visitRem(BinaryOperator &I);
94 Instruction *visitAnd(BinaryOperator &I);
95 Instruction *visitOr (BinaryOperator &I);
96 Instruction *visitXor(BinaryOperator &I);
97 Instruction *visitSetCondInst(BinaryOperator &I);
98 Instruction *visitShiftInst(ShiftInst &I);
99 Instruction *visitCastInst(CastInst &CI);
100 Instruction *visitCallInst(CallInst &CI);
101 Instruction *visitInvokeInst(InvokeInst &II);
102 Instruction *visitPHINode(PHINode &PN);
103 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
104 Instruction *visitAllocationInst(AllocationInst &AI);
105 Instruction *visitFreeInst(FreeInst &FI);
106 Instruction *visitLoadInst(LoadInst &LI);
107 Instruction *visitBranchInst(BranchInst &BI);
109 // visitInstruction - Specify what to return for unhandled instructions...
110 Instruction *visitInstruction(Instruction &I) { return 0; }
113 Instruction *visitCallSite(CallSite CS);
114 bool transformConstExprCastCall(CallSite CS);
116 // InsertNewInstBefore - insert an instruction New before instruction Old
117 // in the program. Add the new instruction to the worklist.
119 void InsertNewInstBefore(Instruction *New, Instruction &Old) {
120 assert(New && New->getParent() == 0 &&
121 "New instruction already inserted into a basic block!");
122 BasicBlock *BB = Old.getParent();
123 BB->getInstList().insert(&Old, New); // Insert inst
124 WorkList.push_back(New); // Add to worklist
128 // ReplaceInstUsesWith - This method is to be used when an instruction is
129 // found to be dead, replacable with another preexisting expression. Here
130 // we add all uses of I to the worklist, replace all uses of I with the new
131 // value, then return I, so that the inst combiner will know that I was
134 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
135 AddUsesToWorkList(I); // Add all modified instrs to worklist
136 I.replaceAllUsesWith(V);
140 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
141 /// InsertBefore instruction. This is specialized a bit to avoid inserting
142 /// casts that are known to not do anything...
144 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
145 Instruction *InsertBefore);
147 // SimplifyCommutative - This performs a few simplifications for commutative
149 bool SimplifyCommutative(BinaryOperator &I);
151 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
152 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
155 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
158 // getComplexity: Assign a complexity or rank value to LLVM Values...
159 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
160 static unsigned getComplexity(Value *V) {
161 if (isa<Instruction>(V)) {
162 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
166 if (isa<Argument>(V)) return 2;
167 return isa<Constant>(V) ? 0 : 1;
170 // isOnlyUse - Return true if this instruction will be deleted if we stop using
172 static bool isOnlyUse(Value *V) {
173 return V->hasOneUse() || isa<Constant>(V);
176 // SimplifyCommutative - This performs a few simplifications for commutative
179 // 1. Order operands such that they are listed from right (least complex) to
180 // left (most complex). This puts constants before unary operators before
183 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
184 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
186 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
187 bool Changed = false;
188 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
189 Changed = !I.swapOperands();
191 if (!I.isAssociative()) return Changed;
192 Instruction::BinaryOps Opcode = I.getOpcode();
193 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
194 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
195 if (isa<Constant>(I.getOperand(1))) {
196 Constant *Folded = ConstantExpr::get(I.getOpcode(),
197 cast<Constant>(I.getOperand(1)),
198 cast<Constant>(Op->getOperand(1)));
199 I.setOperand(0, Op->getOperand(0));
200 I.setOperand(1, Folded);
202 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
203 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
204 isOnlyUse(Op) && isOnlyUse(Op1)) {
205 Constant *C1 = cast<Constant>(Op->getOperand(1));
206 Constant *C2 = cast<Constant>(Op1->getOperand(1));
208 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
209 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
210 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
213 WorkList.push_back(New);
214 I.setOperand(0, New);
215 I.setOperand(1, Folded);
222 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
223 // if the LHS is a constant zero (which is the 'negate' form).
225 static inline Value *dyn_castNegVal(Value *V) {
226 if (BinaryOperator::isNeg(V))
227 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
229 // Constants can be considered to be negated values if they can be folded...
230 if (Constant *C = dyn_cast<Constant>(V))
231 return ConstantExpr::get(Instruction::Sub,
232 Constant::getNullValue(V->getType()), C);
236 static Constant *NotConstant(Constant *C) {
237 return ConstantExpr::get(Instruction::Xor, C,
238 ConstantIntegral::getAllOnesValue(C->getType()));
241 static inline Value *dyn_castNotVal(Value *V) {
242 if (BinaryOperator::isNot(V))
243 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
245 // Constants can be considered to be not'ed values...
246 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
247 return NotConstant(C);
251 // dyn_castFoldableMul - If this value is a multiply that can be folded into
252 // other computations (because it has a constant operand), return the
253 // non-constant operand of the multiply.
255 static inline Value *dyn_castFoldableMul(Value *V) {
256 if (V->hasOneUse() && V->getType()->isInteger())
257 if (Instruction *I = dyn_cast<Instruction>(V))
258 if (I->getOpcode() == Instruction::Mul)
259 if (isa<Constant>(I->getOperand(1)))
260 return I->getOperand(0);
264 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
265 // a constant, return the constant being anded with.
267 template<class ValueType>
268 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
269 if (Instruction *I = dyn_cast<Instruction>(V))
270 if (I->getOpcode() == Instruction::And)
271 return dyn_cast<Constant>(I->getOperand(1));
273 // If this is a constant, it acts just like we were masking with it.
274 return dyn_cast<Constant>(V);
277 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
279 static unsigned Log2(uint64_t Val) {
280 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
283 if (Val & 1) return 0; // Multiple bits set?
291 /// AssociativeOpt - Perform an optimization on an associative operator. This
292 /// function is designed to check a chain of associative operators for a
293 /// potential to apply a certain optimization. Since the optimization may be
294 /// applicable if the expression was reassociated, this checks the chain, then
295 /// reassociates the expression as necessary to expose the optimization
296 /// opportunity. This makes use of a special Functor, which must define
297 /// 'shouldApply' and 'apply' methods.
299 template<typename Functor>
300 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
301 unsigned Opcode = Root.getOpcode();
302 Value *LHS = Root.getOperand(0);
304 // Quick check, see if the immediate LHS matches...
305 if (F.shouldApply(LHS))
306 return F.apply(Root);
308 // Otherwise, if the LHS is not of the same opcode as the root, return.
309 Instruction *LHSI = dyn_cast<Instruction>(LHS);
310 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
311 // Should we apply this transform to the RHS?
312 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
314 // If not to the RHS, check to see if we should apply to the LHS...
315 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
316 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
320 // If the functor wants to apply the optimization to the RHS of LHSI,
321 // reassociate the expression from ((? op A) op B) to (? op (A op B))
323 BasicBlock *BB = Root.getParent();
324 // All of the instructions have a single use and have no side-effects,
325 // because of this, we can pull them all into the current basic block.
326 if (LHSI->getParent() != BB) {
327 // Move all of the instructions from root to LHSI into the current
329 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
330 Instruction *LastUse = &Root;
331 while (TmpLHSI->getParent() == BB) {
333 TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
336 // Loop over all of the instructions in other blocks, moving them into
338 Value *TmpLHS = TmpLHSI;
340 TmpLHSI = cast<Instruction>(TmpLHS);
341 // Remove from current block...
342 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
343 // Insert before the last instruction...
344 BB->getInstList().insert(LastUse, TmpLHSI);
345 TmpLHS = TmpLHSI->getOperand(0);
346 } while (TmpLHSI != LHSI);
349 // Now all of the instructions are in the current basic block, go ahead
350 // and perform the reassociation.
351 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
353 // First move the selected RHS to the LHS of the root...
354 Root.setOperand(0, LHSI->getOperand(1));
356 // Make what used to be the LHS of the root be the user of the root...
357 Value *ExtraOperand = TmpLHSI->getOperand(1);
358 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
359 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
360 BB->getInstList().remove(&Root); // Remove root from the BB
361 BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
363 // Now propagate the ExtraOperand down the chain of instructions until we
365 while (TmpLHSI != LHSI) {
366 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
367 Value *NextOp = NextLHSI->getOperand(1);
368 NextLHSI->setOperand(1, ExtraOperand);
370 ExtraOperand = NextOp;
373 // Now that the instructions are reassociated, have the functor perform
374 // the transformation...
375 return F.apply(Root);
378 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
384 // AddRHS - Implements: X + X --> X << 1
387 AddRHS(Value *rhs) : RHS(rhs) {}
388 bool shouldApply(Value *LHS) const { return LHS == RHS; }
389 Instruction *apply(BinaryOperator &Add) const {
390 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
391 ConstantInt::get(Type::UByteTy, 1));
395 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
397 struct AddMaskingAnd {
399 AddMaskingAnd(Constant *c) : C2(c) {}
400 bool shouldApply(Value *LHS) const {
401 if (Constant *C1 = dyn_castMaskingAnd(LHS))
402 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
405 Instruction *apply(BinaryOperator &Add) const {
406 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
413 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
414 bool Changed = SimplifyCommutative(I);
415 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
418 if (RHS == Constant::getNullValue(I.getType()))
419 return ReplaceInstUsesWith(I, LHS);
422 if (I.getType()->isInteger())
423 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
426 if (Value *V = dyn_castNegVal(LHS))
427 return BinaryOperator::create(Instruction::Sub, RHS, V);
430 if (!isa<Constant>(RHS))
431 if (Value *V = dyn_castNegVal(RHS))
432 return BinaryOperator::create(Instruction::Sub, LHS, V);
434 // X*C + X --> X * (C+1)
435 if (dyn_castFoldableMul(LHS) == RHS) {
437 ConstantExpr::get(Instruction::Add,
438 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
439 ConstantInt::get(I.getType(), 1));
440 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
443 // X + X*C --> X * (C+1)
444 if (dyn_castFoldableMul(RHS) == LHS) {
446 ConstantExpr::get(Instruction::Add,
447 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
448 ConstantInt::get(I.getType(), 1));
449 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
452 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
453 if (Constant *C2 = dyn_castMaskingAnd(RHS))
454 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
456 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
457 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
458 switch (ILHS->getOpcode()) {
459 case Instruction::Xor:
460 // ~X + C --> (C-1) - X
461 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
462 if (XorRHS->isAllOnesValue())
463 return BinaryOperator::create(Instruction::Sub,
464 ConstantExpr::get(Instruction::Sub,
465 CRHS, ConstantInt::get(I.getType(), 1)),
466 ILHS->getOperand(0));
473 return Changed ? &I : 0;
476 // isSignBit - Return true if the value represented by the constant only has the
477 // highest order bit set.
478 static bool isSignBit(ConstantInt *CI) {
479 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
480 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
483 static unsigned getTypeSizeInBits(const Type *Ty) {
484 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
487 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
488 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
490 if (Op0 == Op1) // sub X, X -> 0
491 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
493 // If this is a 'B = x-(-A)', change to B = x+A...
494 if (Value *V = dyn_castNegVal(Op1))
495 return BinaryOperator::create(Instruction::Add, Op0, V);
497 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
498 // Replace (-1 - A) with (~A)...
499 if (C->isAllOnesValue())
500 return BinaryOperator::createNot(Op1);
502 // C - ~X == X + (1+C)
503 if (BinaryOperator::isNot(Op1))
504 return BinaryOperator::create(Instruction::Add,
505 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
506 ConstantExpr::get(Instruction::Add, C,
507 ConstantInt::get(I.getType(), 1)));
510 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
511 if (Op1I->hasOneUse()) {
512 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
513 // is not used by anyone else...
515 if (Op1I->getOpcode() == Instruction::Sub &&
516 !Op1I->getType()->isFloatingPoint()) {
517 // Swap the two operands of the subexpr...
518 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
519 Op1I->setOperand(0, IIOp1);
520 Op1I->setOperand(1, IIOp0);
522 // Create the new top level add instruction...
523 return BinaryOperator::create(Instruction::Add, Op0, Op1);
526 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
528 if (Op1I->getOpcode() == Instruction::And &&
529 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
530 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
532 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
533 return BinaryOperator::create(Instruction::And, Op0, NewNot);
536 // X - X*C --> X * (1-C)
537 if (dyn_castFoldableMul(Op1I) == Op0) {
539 ConstantExpr::get(Instruction::Sub,
540 ConstantInt::get(I.getType(), 1),
541 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
542 assert(CP1 && "Couldn't constant fold 1-C?");
543 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
547 // X*C - X --> X * (C-1)
548 if (dyn_castFoldableMul(Op0) == Op1) {
550 ConstantExpr::get(Instruction::Sub,
551 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
552 ConstantInt::get(I.getType(), 1));
553 assert(CP1 && "Couldn't constant fold C - 1?");
554 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
560 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
561 bool Changed = SimplifyCommutative(I);
562 Value *Op0 = I.getOperand(0);
564 // Simplify mul instructions with a constant RHS...
565 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
566 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
568 // ((X << C1)*C2) == (X * (C2 << C1))
569 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
570 if (SI->getOpcode() == Instruction::Shl)
571 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
572 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
573 ConstantExpr::get(Instruction::Shl, CI, ShOp));
575 if (CI->isNullValue())
576 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
577 if (CI->equalsInt(1)) // X * 1 == X
578 return ReplaceInstUsesWith(I, Op0);
579 if (CI->isAllOnesValue()) // X * -1 == 0 - X
580 return BinaryOperator::createNeg(Op0, I.getName());
582 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
583 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
584 return new ShiftInst(Instruction::Shl, Op0,
585 ConstantUInt::get(Type::UByteTy, C));
587 ConstantFP *Op1F = cast<ConstantFP>(Op1);
588 if (Op1F->isNullValue())
589 return ReplaceInstUsesWith(I, Op1);
591 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
592 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
593 if (Op1F->getValue() == 1.0)
594 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
598 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
599 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
600 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
602 // If one of the operands of the multiply is a cast from a boolean value, then
603 // we know the bool is either zero or one, so this is a 'masking' multiply.
604 // See if we can simplify things based on how the boolean was originally
606 CastInst *BoolCast = 0;
607 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
608 if (CI->getOperand(0)->getType() == Type::BoolTy)
611 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
612 if (CI->getOperand(0)->getType() == Type::BoolTy)
615 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
616 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
617 const Type *SCOpTy = SCIOp0->getType();
619 // If the source is X < 0, and X is a signed integer type, convert this
620 // multiply into a shift/and combination.
621 if (SCI->getOpcode() == Instruction::SetLT &&
622 isa<Constant>(SCIOp1) && cast<Constant>(SCIOp1)->isNullValue() &&
623 SCOpTy->isInteger() && SCOpTy->isSigned()) {
625 // Shift the X value right to turn it into "all signbits".
626 Constant *Amt = ConstantUInt::get(Type::UByteTy,
627 SCOpTy->getPrimitiveSize()*8-1);
628 Value *V = new ShiftInst(Instruction::Shr, SCIOp0, Amt,
629 BoolCast->getName()+".mask", &I);
631 // If the multiply type is not the same as the source type, sign extend
632 // or truncate to the multiply type.
633 if (I.getType() != V->getType())
634 V = new CastInst(V, I.getType(), V->getName(), &I);
636 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
637 return BinaryOperator::create(Instruction::And, V, OtherOp);
642 return Changed ? &I : 0;
645 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
647 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
648 if (RHS->equalsInt(1))
649 return ReplaceInstUsesWith(I, I.getOperand(0));
651 // Check to see if this is an unsigned division with an exact power of 2,
652 // if so, convert to a right shift.
653 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
654 if (uint64_t Val = C->getValue()) // Don't break X / 0
655 if (uint64_t C = Log2(Val))
656 return new ShiftInst(Instruction::Shr, I.getOperand(0),
657 ConstantUInt::get(Type::UByteTy, C));
660 // 0 / X == 0, we don't need to preserve faults!
661 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
662 if (LHS->equalsInt(0))
663 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
669 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
670 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
671 if (RHS->equalsInt(1)) // X % 1 == 0
672 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
674 // Check to see if this is an unsigned remainder with an exact power of 2,
675 // if so, convert to a bitwise and.
676 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
677 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
679 return BinaryOperator::create(Instruction::And, I.getOperand(0),
680 ConstantUInt::get(I.getType(), Val-1));
683 // 0 % X == 0, we don't need to preserve faults!
684 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
685 if (LHS->equalsInt(0))
686 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
691 // isMaxValueMinusOne - return true if this is Max-1
692 static bool isMaxValueMinusOne(const ConstantInt *C) {
693 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
694 // Calculate -1 casted to the right type...
695 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
696 uint64_t Val = ~0ULL; // All ones
697 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
698 return CU->getValue() == Val-1;
701 const ConstantSInt *CS = cast<ConstantSInt>(C);
703 // Calculate 0111111111..11111
704 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
705 int64_t Val = INT64_MAX; // All ones
706 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
707 return CS->getValue() == Val-1;
710 // isMinValuePlusOne - return true if this is Min+1
711 static bool isMinValuePlusOne(const ConstantInt *C) {
712 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
713 return CU->getValue() == 1;
715 const ConstantSInt *CS = cast<ConstantSInt>(C);
717 // Calculate 1111111111000000000000
718 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
719 int64_t Val = -1; // All ones
720 Val <<= TypeBits-1; // Shift over to the right spot
721 return CS->getValue() == Val+1;
724 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
725 /// are carefully arranged to allow folding of expressions such as:
727 /// (A < B) | (A > B) --> (A != B)
729 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
730 /// represents that the comparison is true if A == B, and bit value '1' is true
733 static unsigned getSetCondCode(const SetCondInst *SCI) {
734 switch (SCI->getOpcode()) {
736 case Instruction::SetGT: return 1;
737 case Instruction::SetEQ: return 2;
738 case Instruction::SetGE: return 3;
739 case Instruction::SetLT: return 4;
740 case Instruction::SetNE: return 5;
741 case Instruction::SetLE: return 6;
744 assert(0 && "Invalid SetCC opcode!");
749 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
750 /// opcode and two operands into either a constant true or false, or a brand new
751 /// SetCC instruction.
752 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
754 case 0: return ConstantBool::False;
755 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
756 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
757 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
758 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
759 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
760 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
761 case 7: return ConstantBool::True;
762 default: assert(0 && "Illegal SetCCCode!"); return 0;
766 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
767 struct FoldSetCCLogical {
770 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
771 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
772 bool shouldApply(Value *V) const {
773 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
774 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
775 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
778 Instruction *apply(BinaryOperator &Log) const {
779 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
780 if (SCI->getOperand(0) != LHS) {
781 assert(SCI->getOperand(1) == LHS);
782 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
785 unsigned LHSCode = getSetCondCode(SCI);
786 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
788 switch (Log.getOpcode()) {
789 case Instruction::And: Code = LHSCode & RHSCode; break;
790 case Instruction::Or: Code = LHSCode | RHSCode; break;
791 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
792 default: assert(0 && "Illegal logical opcode!"); return 0;
795 Value *RV = getSetCCValue(Code, LHS, RHS);
796 if (Instruction *I = dyn_cast<Instruction>(RV))
798 // Otherwise, it's a constant boolean value...
799 return IC.ReplaceInstUsesWith(Log, RV);
804 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
805 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
806 // guaranteed to be either a shift instruction or a binary operator.
807 Instruction *InstCombiner::OptAndOp(Instruction *Op,
808 ConstantIntegral *OpRHS,
809 ConstantIntegral *AndRHS,
810 BinaryOperator &TheAnd) {
811 Value *X = Op->getOperand(0);
812 Constant *Together = 0;
813 if (!isa<ShiftInst>(Op))
814 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
816 switch (Op->getOpcode()) {
817 case Instruction::Xor:
818 if (Together->isNullValue()) {
819 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
820 return BinaryOperator::create(Instruction::And, X, AndRHS);
821 } else if (Op->hasOneUse()) {
822 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
823 std::string OpName = Op->getName(); Op->setName("");
824 Instruction *And = BinaryOperator::create(Instruction::And,
826 InsertNewInstBefore(And, TheAnd);
827 return BinaryOperator::create(Instruction::Xor, And, Together);
830 case Instruction::Or:
831 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
832 if (Together->isNullValue())
833 return BinaryOperator::create(Instruction::And, X, AndRHS);
835 if (Together == AndRHS) // (X | C) & C --> C
836 return ReplaceInstUsesWith(TheAnd, AndRHS);
838 if (Op->hasOneUse() && Together != OpRHS) {
839 // (X | C1) & C2 --> (X | (C1&C2)) & C2
840 std::string Op0Name = Op->getName(); Op->setName("");
841 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
843 InsertNewInstBefore(Or, TheAnd);
844 return BinaryOperator::create(Instruction::And, Or, AndRHS);
848 case Instruction::Add:
849 if (Op->hasOneUse()) {
850 // Adding a one to a single bit bit-field should be turned into an XOR
851 // of the bit. First thing to check is to see if this AND is with a
852 // single bit constant.
853 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
855 // Clear bits that are not part of the constant.
856 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
858 // If there is only one bit set...
859 if ((AndRHSV & (AndRHSV-1)) == 0) {
860 // Ok, at this point, we know that we are masking the result of the
861 // ADD down to exactly one bit. If the constant we are adding has
862 // no bits set below this bit, then we can eliminate the ADD.
863 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
865 // Check to see if any bits below the one bit set in AndRHSV are set.
866 if ((AddRHS & (AndRHSV-1)) == 0) {
867 // If not, the only thing that can effect the output of the AND is
868 // the bit specified by AndRHSV. If that bit is set, the effect of
869 // the XOR is to toggle the bit. If it is clear, then the ADD has
871 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
872 TheAnd.setOperand(0, X);
875 std::string Name = Op->getName(); Op->setName("");
876 // Pull the XOR out of the AND.
877 Instruction *NewAnd =
878 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
879 InsertNewInstBefore(NewAnd, TheAnd);
880 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
887 case Instruction::Shl: {
888 // We know that the AND will not produce any of the bits shifted in, so if
889 // the anded constant includes them, clear them now!
891 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
892 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
893 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
895 TheAnd.setOperand(1, CI);
900 case Instruction::Shr:
901 // We know that the AND will not produce any of the bits shifted in, so if
902 // the anded constant includes them, clear them now! This only applies to
903 // unsigned shifts, because a signed shr may bring in set bits!
905 if (AndRHS->getType()->isUnsigned()) {
906 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
907 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
908 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
910 TheAnd.setOperand(1, CI);
920 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
921 bool Changed = SimplifyCommutative(I);
922 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
924 // and X, X = X and X, 0 == 0
925 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
926 return ReplaceInstUsesWith(I, Op1);
929 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
930 if (RHS->isAllOnesValue())
931 return ReplaceInstUsesWith(I, Op0);
933 // Optimize a variety of ((val OP C1) & C2) combinations...
934 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
935 Instruction *Op0I = cast<Instruction>(Op0);
936 Value *X = Op0I->getOperand(0);
937 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
938 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
943 Value *Op0NotVal = dyn_castNotVal(Op0);
944 Value *Op1NotVal = dyn_castNotVal(Op1);
946 // (~A & ~B) == (~(A | B)) - Demorgan's Law
947 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
948 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
949 Op1NotVal,I.getName()+".demorgan");
950 InsertNewInstBefore(Or, I);
951 return BinaryOperator::createNot(Or);
954 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
955 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
957 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
958 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
959 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
962 return Changed ? &I : 0;
967 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
968 bool Changed = SimplifyCommutative(I);
969 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
971 // or X, X = X or X, 0 == X
972 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
973 return ReplaceInstUsesWith(I, Op0);
976 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
977 if (RHS->isAllOnesValue())
978 return ReplaceInstUsesWith(I, Op1);
980 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
981 // (X & C1) | C2 --> (X | C2) & (C1|C2)
982 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
983 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
984 std::string Op0Name = Op0I->getName(); Op0I->setName("");
985 Instruction *Or = BinaryOperator::create(Instruction::Or,
986 Op0I->getOperand(0), RHS,
988 InsertNewInstBefore(Or, I);
989 return BinaryOperator::create(Instruction::And, Or,
990 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
993 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
994 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
995 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
996 std::string Op0Name = Op0I->getName(); Op0I->setName("");
997 Instruction *Or = BinaryOperator::create(Instruction::Or,
998 Op0I->getOperand(0), RHS,
1000 InsertNewInstBefore(Or, I);
1001 return BinaryOperator::create(Instruction::Xor, Or,
1002 ConstantExpr::get(Instruction::And, Op0CI,
1008 // (A & C1)|(A & C2) == A & (C1|C2)
1009 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
1010 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
1011 if (LHS->getOperand(0) == RHS->getOperand(0))
1012 if (Constant *C0 = dyn_castMaskingAnd(LHS))
1013 if (Constant *C1 = dyn_castMaskingAnd(RHS))
1014 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
1015 ConstantExpr::get(Instruction::Or, C0, C1));
1017 Value *Op0NotVal = dyn_castNotVal(Op0);
1018 Value *Op1NotVal = dyn_castNotVal(Op1);
1020 if (Op1 == Op0NotVal) // ~A | A == -1
1021 return ReplaceInstUsesWith(I,
1022 ConstantIntegral::getAllOnesValue(I.getType()));
1024 if (Op0 == Op1NotVal) // A | ~A == -1
1025 return ReplaceInstUsesWith(I,
1026 ConstantIntegral::getAllOnesValue(I.getType()));
1028 // (~A | ~B) == (~(A & B)) - Demorgan's Law
1029 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1030 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
1031 Op1NotVal,I.getName()+".demorgan",
1033 WorkList.push_back(And);
1034 return BinaryOperator::createNot(And);
1037 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1038 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1039 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1042 return Changed ? &I : 0;
1045 // XorSelf - Implements: X ^ X --> 0
1048 XorSelf(Value *rhs) : RHS(rhs) {}
1049 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1050 Instruction *apply(BinaryOperator &Xor) const {
1056 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1057 bool Changed = SimplifyCommutative(I);
1058 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1060 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1061 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1062 assert(Result == &I && "AssociativeOpt didn't work?");
1063 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1066 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1068 if (RHS->isNullValue())
1069 return ReplaceInstUsesWith(I, Op0);
1071 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1072 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1073 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1074 if (RHS == ConstantBool::True && SCI->hasOneUse())
1075 return new SetCondInst(SCI->getInverseCondition(),
1076 SCI->getOperand(0), SCI->getOperand(1));
1078 // ~(c-X) == X-c-1 == X+(-c-1)
1079 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1080 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1081 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1082 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1083 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1084 ConstantInt::get(I.getType(), 1));
1085 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1089 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1090 switch (Op0I->getOpcode()) {
1091 case Instruction::Add:
1092 // ~(X-c) --> (-c-1)-X
1093 if (RHS->isAllOnesValue()) {
1094 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1095 Constant::getNullValue(Op0CI->getType()), Op0CI);
1096 return BinaryOperator::create(Instruction::Sub,
1097 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1098 ConstantInt::get(I.getType(), 1)),
1099 Op0I->getOperand(0));
1102 case Instruction::And:
1103 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1104 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1105 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1107 case Instruction::Or:
1108 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1109 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1110 return BinaryOperator::create(Instruction::And, Op0,
1118 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1120 return ReplaceInstUsesWith(I,
1121 ConstantIntegral::getAllOnesValue(I.getType()));
1123 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1125 return ReplaceInstUsesWith(I,
1126 ConstantIntegral::getAllOnesValue(I.getType()));
1128 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1129 if (Op1I->getOpcode() == Instruction::Or) {
1130 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1131 cast<BinaryOperator>(Op1I)->swapOperands();
1133 std::swap(Op0, Op1);
1134 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1136 std::swap(Op0, Op1);
1138 } else if (Op1I->getOpcode() == Instruction::Xor) {
1139 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1140 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1141 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1142 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1145 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1146 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1147 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1148 cast<BinaryOperator>(Op0I)->swapOperands();
1149 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1150 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1151 WorkList.push_back(cast<Instruction>(NotB));
1152 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1155 } else if (Op0I->getOpcode() == Instruction::Xor) {
1156 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1157 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1158 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1159 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1162 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1163 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1164 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1165 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1166 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1168 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1169 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1170 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1173 return Changed ? &I : 0;
1176 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1177 static Constant *AddOne(ConstantInt *C) {
1178 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1179 ConstantInt::get(C->getType(), 1));
1180 assert(Result && "Constant folding integer addition failed!");
1183 static Constant *SubOne(ConstantInt *C) {
1184 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1185 ConstantInt::get(C->getType(), 1));
1186 assert(Result && "Constant folding integer addition failed!");
1190 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1191 // true when both operands are equal...
1193 static bool isTrueWhenEqual(Instruction &I) {
1194 return I.getOpcode() == Instruction::SetEQ ||
1195 I.getOpcode() == Instruction::SetGE ||
1196 I.getOpcode() == Instruction::SetLE;
1199 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1200 bool Changed = SimplifyCommutative(I);
1201 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1202 const Type *Ty = Op0->getType();
1206 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1208 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1209 if (isa<ConstantPointerNull>(Op1) &&
1210 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1211 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1214 // setcc's with boolean values can always be turned into bitwise operations
1215 if (Ty == Type::BoolTy) {
1216 // If this is <, >, or !=, we can change this into a simple xor instruction
1217 if (!isTrueWhenEqual(I))
1218 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1220 // Otherwise we need to make a temporary intermediate instruction and insert
1221 // it into the instruction stream. This is what we are after:
1223 // seteq bool %A, %B -> ~(A^B)
1224 // setle bool %A, %B -> ~A | B
1225 // setge bool %A, %B -> A | ~B
1227 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1228 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1230 InsertNewInstBefore(Xor, I);
1231 return BinaryOperator::createNot(Xor);
1234 // Handle the setXe cases...
1235 assert(I.getOpcode() == Instruction::SetGE ||
1236 I.getOpcode() == Instruction::SetLE);
1238 if (I.getOpcode() == Instruction::SetGE)
1239 std::swap(Op0, Op1); // Change setge -> setle
1241 // Now we just have the SetLE case.
1242 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1243 InsertNewInstBefore(Not, I);
1244 return BinaryOperator::create(Instruction::Or, Not, Op1);
1247 // Check to see if we are doing one of many comparisons against constant
1248 // integers at the end of their ranges...
1250 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1251 // Simplify seteq and setne instructions...
1252 if (I.getOpcode() == Instruction::SetEQ ||
1253 I.getOpcode() == Instruction::SetNE) {
1254 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1256 // If the first operand is (and|or|xor) with a constant, and the second
1257 // operand is a constant, simplify a bit.
1258 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1259 switch (BO->getOpcode()) {
1260 case Instruction::Add:
1261 if (CI->isNullValue()) {
1262 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1263 // efficiently invertible, or if the add has just this one use.
1264 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1265 if (Value *NegVal = dyn_castNegVal(BOp1))
1266 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1267 else if (Value *NegVal = dyn_castNegVal(BOp0))
1268 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1269 else if (BO->hasOneUse()) {
1270 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1272 InsertNewInstBefore(Neg, I);
1273 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1277 case Instruction::Xor:
1278 // For the xor case, we can xor two constants together, eliminating
1279 // the explicit xor.
1280 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1281 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1282 ConstantExpr::get(Instruction::Xor, CI, BOC));
1285 case Instruction::Sub:
1286 // Replace (([sub|xor] A, B) != 0) with (A != B)
1287 if (CI->isNullValue())
1288 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1292 case Instruction::Or:
1293 // If bits are being or'd in that are not present in the constant we
1294 // are comparing against, then the comparison could never succeed!
1295 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1296 Constant *NotCI = NotConstant(CI);
1297 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1298 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1302 case Instruction::And:
1303 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1304 // If bits are being compared against that are and'd out, then the
1305 // comparison can never succeed!
1306 if (!ConstantExpr::get(Instruction::And, CI,
1307 NotConstant(BOC))->isNullValue())
1308 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1310 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1311 // to be a signed value as appropriate.
1312 if (isSignBit(BOC)) {
1313 Value *X = BO->getOperand(0);
1314 // If 'X' is not signed, insert a cast now...
1315 if (!BOC->getType()->isSigned()) {
1317 switch (BOC->getType()->getPrimitiveID()) {
1318 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1319 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1320 case Type::UIntTyID: DestTy = Type::IntTy; break;
1321 case Type::ULongTyID: DestTy = Type::LongTy; break;
1322 default: assert(0 && "Invalid unsigned integer type!"); abort();
1324 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1325 InsertNewInstBefore(NewCI, I);
1328 return new SetCondInst(isSetNE ? Instruction::SetLT :
1329 Instruction::SetGE, X,
1330 Constant::getNullValue(X->getType()));
1338 // Check to see if we are comparing against the minimum or maximum value...
1339 if (CI->isMinValue()) {
1340 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1341 return ReplaceInstUsesWith(I, ConstantBool::False);
1342 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1343 return ReplaceInstUsesWith(I, ConstantBool::True);
1344 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1345 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1346 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1347 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1349 } else if (CI->isMaxValue()) {
1350 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1351 return ReplaceInstUsesWith(I, ConstantBool::False);
1352 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1353 return ReplaceInstUsesWith(I, ConstantBool::True);
1354 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1355 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1356 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1357 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1359 // Comparing against a value really close to min or max?
1360 } else if (isMinValuePlusOne(CI)) {
1361 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1362 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1363 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1364 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1366 } else if (isMaxValueMinusOne(CI)) {
1367 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1368 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1369 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1370 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1374 // Test to see if the operands of the setcc are casted versions of other
1375 // values. If the cast can be stripped off both arguments, we do so now.
1376 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1377 Value *CastOp0 = CI->getOperand(0);
1378 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1379 !isa<Argument>(Op1) &&
1380 (I.getOpcode() == Instruction::SetEQ ||
1381 I.getOpcode() == Instruction::SetNE)) {
1382 // We keep moving the cast from the left operand over to the right
1383 // operand, where it can often be eliminated completely.
1386 // If operand #1 is a cast instruction, see if we can eliminate it as
1388 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1389 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1391 Op1 = CI2->getOperand(0);
1393 // If Op1 is a constant, we can fold the cast into the constant.
1394 if (Op1->getType() != Op0->getType())
1395 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1396 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1398 // Otherwise, cast the RHS right before the setcc
1399 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1400 InsertNewInstBefore(cast<Instruction>(Op1), I);
1402 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1405 // Handle the special case of: setcc (cast bool to X), <cst>
1406 // This comes up when you have code like
1409 // For generality, we handle any zero-extension of any operand comparison
1411 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1412 const Type *SrcTy = CastOp0->getType();
1413 const Type *DestTy = Op0->getType();
1414 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1415 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1416 // Ok, we have an expansion of operand 0 into a new type. Get the
1417 // constant value, masink off bits which are not set in the RHS. These
1418 // could be set if the destination value is signed.
1419 uint64_t ConstVal = ConstantRHS->getRawValue();
1420 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1422 // If the constant we are comparing it with has high bits set, which
1423 // don't exist in the original value, the values could never be equal,
1424 // because the source would be zero extended.
1426 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1427 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1428 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1429 switch (I.getOpcode()) {
1430 default: assert(0 && "Unknown comparison type!");
1431 case Instruction::SetEQ:
1432 return ReplaceInstUsesWith(I, ConstantBool::False);
1433 case Instruction::SetNE:
1434 return ReplaceInstUsesWith(I, ConstantBool::True);
1435 case Instruction::SetLT:
1436 case Instruction::SetLE:
1437 if (DestTy->isSigned() && HasSignBit)
1438 return ReplaceInstUsesWith(I, ConstantBool::False);
1439 return ReplaceInstUsesWith(I, ConstantBool::True);
1440 case Instruction::SetGT:
1441 case Instruction::SetGE:
1442 if (DestTy->isSigned() && HasSignBit)
1443 return ReplaceInstUsesWith(I, ConstantBool::True);
1444 return ReplaceInstUsesWith(I, ConstantBool::False);
1448 // Otherwise, we can replace the setcc with a setcc of the smaller
1450 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1451 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1455 return Changed ? &I : 0;
1460 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1461 assert(I.getOperand(1)->getType() == Type::UByteTy);
1462 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1463 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1465 // shl X, 0 == X and shr X, 0 == X
1466 // shl 0, X == 0 and shr 0, X == 0
1467 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1468 Op0 == Constant::getNullValue(Op0->getType()))
1469 return ReplaceInstUsesWith(I, Op0);
1471 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1473 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1474 if (CSI->isAllOnesValue())
1475 return ReplaceInstUsesWith(I, CSI);
1477 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1478 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1479 // of a signed value.
1481 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1482 if (CUI->getValue() >= TypeBits &&
1483 (!Op0->getType()->isSigned() || isLeftShift))
1484 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1486 // ((X*C1) << C2) == (X * (C1 << C2))
1487 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1488 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1489 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1490 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1491 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1494 // If the operand is an bitwise operator with a constant RHS, and the
1495 // shift is the only use, we can pull it out of the shift.
1496 if (Op0->hasOneUse())
1497 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1498 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1499 bool isValid = true; // Valid only for And, Or, Xor
1500 bool highBitSet = false; // Transform if high bit of constant set?
1502 switch (Op0BO->getOpcode()) {
1503 default: isValid = false; break; // Do not perform transform!
1504 case Instruction::Or:
1505 case Instruction::Xor:
1508 case Instruction::And:
1513 // If this is a signed shift right, and the high bit is modified
1514 // by the logical operation, do not perform the transformation.
1515 // The highBitSet boolean indicates the value of the high bit of
1516 // the constant which would cause it to be modified for this
1519 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1520 uint64_t Val = Op0C->getRawValue();
1521 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1525 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1527 Instruction *NewShift =
1528 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1531 InsertNewInstBefore(NewShift, I);
1533 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1538 // If this is a shift of a shift, see if we can fold the two together...
1539 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1540 if (ConstantUInt *ShiftAmt1C =
1541 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1542 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1543 unsigned ShiftAmt2 = CUI->getValue();
1545 // Check for (A << c1) << c2 and (A >> c1) >> c2
1546 if (I.getOpcode() == Op0SI->getOpcode()) {
1547 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1548 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1549 ConstantUInt::get(Type::UByteTy, Amt));
1552 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1553 // signed types, we can only support the (A >> c1) << c2 configuration,
1554 // because it can not turn an arbitrary bit of A into a sign bit.
1555 if (I.getType()->isUnsigned() || isLeftShift) {
1556 // Calculate bitmask for what gets shifted off the edge...
1557 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1559 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1561 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1564 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1565 C, Op0SI->getOperand(0)->getName()+".mask");
1566 InsertNewInstBefore(Mask, I);
1568 // Figure out what flavor of shift we should use...
1569 if (ShiftAmt1 == ShiftAmt2)
1570 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1571 else if (ShiftAmt1 < ShiftAmt2) {
1572 return new ShiftInst(I.getOpcode(), Mask,
1573 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1575 return new ShiftInst(Op0SI->getOpcode(), Mask,
1576 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1586 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1589 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1590 const Type *DstTy) {
1592 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1593 // are identical and the bits don't get reinterpreted (for example
1594 // int->float->int would not be allowed)
1595 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1598 // Allow free casting and conversion of sizes as long as the sign doesn't
1600 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1601 unsigned SrcSize = SrcTy->getPrimitiveSize();
1602 unsigned MidSize = MidTy->getPrimitiveSize();
1603 unsigned DstSize = DstTy->getPrimitiveSize();
1605 // Cases where we are monotonically decreasing the size of the type are
1606 // always ok, regardless of what sign changes are going on.
1608 if (SrcSize >= MidSize && MidSize >= DstSize)
1611 // Cases where the source and destination type are the same, but the middle
1612 // type is bigger are noops.
1614 if (SrcSize == DstSize && MidSize > SrcSize)
1617 // If we are monotonically growing, things are more complex.
1619 if (SrcSize <= MidSize && MidSize <= DstSize) {
1620 // We have eight combinations of signedness to worry about. Here's the
1622 static const int SignTable[8] = {
1623 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1624 1, // U U U Always ok
1625 1, // U U S Always ok
1626 3, // U S U Ok iff SrcSize != MidSize
1627 3, // U S S Ok iff SrcSize != MidSize
1628 0, // S U U Never ok
1629 2, // S U S Ok iff MidSize == DstSize
1630 1, // S S U Always ok
1631 1, // S S S Always ok
1634 // Choose an action based on the current entry of the signtable that this
1635 // cast of cast refers to...
1636 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1637 switch (SignTable[Row]) {
1638 case 0: return false; // Never ok
1639 case 1: return true; // Always ok
1640 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1641 case 3: // Ok iff SrcSize != MidSize
1642 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1643 default: assert(0 && "Bad entry in sign table!");
1648 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1649 // like: short -> ushort -> uint, because this can create wrong results if
1650 // the input short is negative!
1655 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1656 if (V->getType() == Ty || isa<Constant>(V)) return false;
1657 if (const CastInst *CI = dyn_cast<CastInst>(V))
1658 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1663 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1664 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1665 /// casts that are known to not do anything...
1667 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1668 Instruction *InsertBefore) {
1669 if (V->getType() == DestTy) return V;
1670 if (Constant *C = dyn_cast<Constant>(V))
1671 return ConstantExpr::getCast(C, DestTy);
1673 CastInst *CI = new CastInst(V, DestTy, V->getName());
1674 InsertNewInstBefore(CI, *InsertBefore);
1678 // CastInst simplification
1680 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1681 Value *Src = CI.getOperand(0);
1683 // If the user is casting a value to the same type, eliminate this cast
1685 if (CI.getType() == Src->getType())
1686 return ReplaceInstUsesWith(CI, Src);
1688 // If casting the result of another cast instruction, try to eliminate this
1691 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1692 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1693 CSrc->getType(), CI.getType())) {
1694 // This instruction now refers directly to the cast's src operand. This
1695 // has a good chance of making CSrc dead.
1696 CI.setOperand(0, CSrc->getOperand(0));
1700 // If this is an A->B->A cast, and we are dealing with integral types, try
1701 // to convert this into a logical 'and' instruction.
1703 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1704 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1705 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1706 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1707 assert(CSrc->getType() != Type::ULongTy &&
1708 "Cannot have type bigger than ulong!");
1709 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1710 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1711 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1716 // If casting the result of a getelementptr instruction with no offset, turn
1717 // this into a cast of the original pointer!
1719 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1720 bool AllZeroOperands = true;
1721 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1722 if (!isa<Constant>(GEP->getOperand(i)) ||
1723 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1724 AllZeroOperands = false;
1727 if (AllZeroOperands) {
1728 CI.setOperand(0, GEP->getOperand(0));
1733 // If we are casting a malloc or alloca to a pointer to a type of the same
1734 // size, rewrite the allocation instruction to allocate the "right" type.
1736 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1737 if (AI->hasOneUse() && !AI->isArrayAllocation())
1738 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1739 // Get the type really allocated and the type casted to...
1740 const Type *AllocElTy = AI->getAllocatedType();
1741 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1742 const Type *CastElTy = PTy->getElementType();
1743 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1745 // If the allocation is for an even multiple of the cast type size
1746 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1747 Value *Amt = ConstantUInt::get(Type::UIntTy,
1748 AllocElTySize/CastElTySize);
1749 std::string Name = AI->getName(); AI->setName("");
1750 AllocationInst *New;
1751 if (isa<MallocInst>(AI))
1752 New = new MallocInst(CastElTy, Amt, Name);
1754 New = new AllocaInst(CastElTy, Amt, Name);
1755 InsertNewInstBefore(New, CI);
1756 return ReplaceInstUsesWith(CI, New);
1760 // If the source value is an instruction with only this use, we can attempt to
1761 // propagate the cast into the instruction. Also, only handle integral types
1763 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1764 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1765 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1766 const Type *DestTy = CI.getType();
1767 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1768 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1770 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1771 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1773 switch (SrcI->getOpcode()) {
1774 case Instruction::Add:
1775 case Instruction::Mul:
1776 case Instruction::And:
1777 case Instruction::Or:
1778 case Instruction::Xor:
1779 // If we are discarding information, or just changing the sign, rewrite.
1780 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1781 // Don't insert two casts if they cannot be eliminated. We allow two
1782 // casts to be inserted if the sizes are the same. This could only be
1783 // converting signedness, which is a noop.
1784 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1785 !ValueRequiresCast(Op0, DestTy)) {
1786 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1787 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1788 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1789 ->getOpcode(), Op0c, Op1c);
1793 case Instruction::Shl:
1794 // Allow changing the sign of the source operand. Do not allow changing
1795 // the size of the shift, UNLESS the shift amount is a constant. We
1796 // mush not change variable sized shifts to a smaller size, because it
1797 // is undefined to shift more bits out than exist in the value.
1798 if (DestBitSize == SrcBitSize ||
1799 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1800 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1801 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1810 // CallInst simplification
1812 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1813 return visitCallSite(&CI);
1816 // InvokeInst simplification
1818 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1819 return visitCallSite(&II);
1822 // getPromotedType - Return the specified type promoted as it would be to pass
1823 // though a va_arg area...
1824 static const Type *getPromotedType(const Type *Ty) {
1825 switch (Ty->getPrimitiveID()) {
1826 case Type::SByteTyID:
1827 case Type::ShortTyID: return Type::IntTy;
1828 case Type::UByteTyID:
1829 case Type::UShortTyID: return Type::UIntTy;
1830 case Type::FloatTyID: return Type::DoubleTy;
1835 // visitCallSite - Improvements for call and invoke instructions.
1837 Instruction *InstCombiner::visitCallSite(CallSite CS) {
1838 bool Changed = false;
1840 // If the callee is a constexpr cast of a function, attempt to move the cast
1841 // to the arguments of the call/invoke.
1842 if (transformConstExprCastCall(CS)) return 0;
1844 Value *Callee = CS.getCalledValue();
1845 const PointerType *PTy = cast<PointerType>(Callee->getType());
1846 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1847 if (FTy->isVarArg()) {
1848 // See if we can optimize any arguments passed through the varargs area of
1850 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
1851 E = CS.arg_end(); I != E; ++I)
1852 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
1853 // If this cast does not effect the value passed through the varargs
1854 // area, we can eliminate the use of the cast.
1855 Value *Op = CI->getOperand(0);
1856 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
1863 return Changed ? CS.getInstruction() : 0;
1866 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1867 // attempt to move the cast to the arguments of the call/invoke.
1869 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1870 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1871 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1872 if (CE->getOpcode() != Instruction::Cast ||
1873 !isa<ConstantPointerRef>(CE->getOperand(0)))
1875 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1876 if (!isa<Function>(CPR->getValue())) return false;
1877 Function *Callee = cast<Function>(CPR->getValue());
1878 Instruction *Caller = CS.getInstruction();
1880 // Okay, this is a cast from a function to a different type. Unless doing so
1881 // would cause a type conversion of one of our arguments, change this call to
1882 // be a direct call with arguments casted to the appropriate types.
1884 const FunctionType *FT = Callee->getFunctionType();
1885 const Type *OldRetTy = Caller->getType();
1887 // Check to see if we are changing the return type...
1888 if (OldRetTy != FT->getReturnType()) {
1889 if (Callee->isExternal() &&
1890 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
1891 !Caller->use_empty())
1892 return false; // Cannot transform this return value...
1894 // If the callsite is an invoke instruction, and the return value is used by
1895 // a PHI node in a successor, we cannot change the return type of the call
1896 // because there is no place to put the cast instruction (without breaking
1897 // the critical edge). Bail out in this case.
1898 if (!Caller->use_empty())
1899 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
1900 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
1902 if (PHINode *PN = dyn_cast<PHINode>(*UI))
1903 if (PN->getParent() == II->getNormalDest() ||
1904 PN->getParent() == II->getUnwindDest())
1908 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1909 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1911 CallSite::arg_iterator AI = CS.arg_begin();
1912 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1913 const Type *ParamTy = FT->getParamType(i);
1914 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1915 if (Callee->isExternal() && !isConvertible) return false;
1918 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1919 Callee->isExternal())
1920 return false; // Do not delete arguments unless we have a function body...
1922 // Okay, we decided that this is a safe thing to do: go ahead and start
1923 // inserting cast instructions as necessary...
1924 std::vector<Value*> Args;
1925 Args.reserve(NumActualArgs);
1927 AI = CS.arg_begin();
1928 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1929 const Type *ParamTy = FT->getParamType(i);
1930 if ((*AI)->getType() == ParamTy) {
1931 Args.push_back(*AI);
1933 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1934 InsertNewInstBefore(Cast, *Caller);
1935 Args.push_back(Cast);
1939 // If the function takes more arguments than the call was taking, add them
1941 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1942 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1944 // If we are removing arguments to the function, emit an obnoxious warning...
1945 if (FT->getNumParams() < NumActualArgs)
1946 if (!FT->isVarArg()) {
1947 std::cerr << "WARNING: While resolving call to function '"
1948 << Callee->getName() << "' arguments were dropped!\n";
1950 // Add all of the arguments in their promoted form to the arg list...
1951 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1952 const Type *PTy = getPromotedType((*AI)->getType());
1953 if (PTy != (*AI)->getType()) {
1954 // Must promote to pass through va_arg area!
1955 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1956 InsertNewInstBefore(Cast, *Caller);
1957 Args.push_back(Cast);
1959 Args.push_back(*AI);
1964 if (FT->getReturnType() == Type::VoidTy)
1965 Caller->setName(""); // Void type should not have a name...
1968 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1969 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
1970 Args, Caller->getName(), Caller);
1972 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1975 // Insert a cast of the return type as necessary...
1977 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1978 if (NV->getType() != Type::VoidTy) {
1979 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1981 // If this is an invoke instruction, we should insert it after the first
1982 // non-phi, instruction in the normal successor block.
1983 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1984 BasicBlock::iterator I = II->getNormalDest()->begin();
1985 while (isa<PHINode>(I)) ++I;
1986 InsertNewInstBefore(NC, *I);
1988 // Otherwise, it's a call, just insert cast right after the call instr
1989 InsertNewInstBefore(NC, *Caller);
1991 AddUsesToWorkList(*Caller);
1993 NV = Constant::getNullValue(Caller->getType());
1997 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1998 Caller->replaceAllUsesWith(NV);
1999 Caller->getParent()->getInstList().erase(Caller);
2000 removeFromWorkList(Caller);
2006 // PHINode simplification
2008 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2009 if (Value *V = hasConstantValue(&PN))
2010 return ReplaceInstUsesWith(PN, V);
2012 // If the only user of this instruction is a cast instruction, and all of the
2013 // incoming values are constants, change this PHI to merge together the casted
2016 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2017 if (CI->getType() != PN.getType()) { // noop casts will be folded
2018 bool AllConstant = true;
2019 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2020 if (!isa<Constant>(PN.getIncomingValue(i))) {
2021 AllConstant = false;
2025 // Make a new PHI with all casted values.
2026 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2027 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2028 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2029 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2030 PN.getIncomingBlock(i));
2033 // Update the cast instruction.
2034 CI->setOperand(0, New);
2035 WorkList.push_back(CI); // revisit the cast instruction to fold.
2036 WorkList.push_back(New); // Make sure to revisit the new Phi
2037 return &PN; // PN is now dead!
2044 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2045 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2046 // If so, eliminate the noop.
2047 if (GEP.getNumOperands() == 1)
2048 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2050 bool HasZeroPointerIndex = false;
2051 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2052 HasZeroPointerIndex = C->isNullValue();
2054 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2055 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2057 // Combine Indices - If the source pointer to this getelementptr instruction
2058 // is a getelementptr instruction, combine the indices of the two
2059 // getelementptr instructions into a single instruction.
2061 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
2062 std::vector<Value *> Indices;
2064 // Can we combine the two pointer arithmetics offsets?
2065 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
2066 isa<Constant>(GEP.getOperand(1))) {
2067 // Replace: gep (gep %P, long C1), long C2, ...
2068 // With: gep %P, long (C1+C2), ...
2069 Value *Sum = ConstantExpr::get(Instruction::Add,
2070 cast<Constant>(Src->getOperand(1)),
2071 cast<Constant>(GEP.getOperand(1)));
2072 assert(Sum && "Constant folding of longs failed!?");
2073 GEP.setOperand(0, Src->getOperand(0));
2074 GEP.setOperand(1, Sum);
2075 AddUsesToWorkList(*Src); // Reduce use count of Src
2077 } else if (Src->getNumOperands() == 2) {
2078 // Replace: gep (gep %P, long B), long A, ...
2079 // With: T = long A+B; gep %P, T, ...
2081 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
2083 Src->getName()+".sum", &GEP);
2084 GEP.setOperand(0, Src->getOperand(0));
2085 GEP.setOperand(1, Sum);
2086 WorkList.push_back(cast<Instruction>(Sum));
2088 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
2089 Src->getNumOperands() != 1) {
2090 // Otherwise we can do the fold if the first index of the GEP is a zero
2091 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
2092 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2093 } else if (Src->getOperand(Src->getNumOperands()-1) ==
2094 Constant::getNullValue(Type::LongTy)) {
2095 // If the src gep ends with a constant array index, merge this get into
2096 // it, even if we have a non-zero array index.
2097 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
2098 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
2101 if (!Indices.empty())
2102 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
2104 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
2105 // GEP of global variable. If all of the indices for this GEP are
2106 // constants, we can promote this to a constexpr instead of an instruction.
2108 // Scan for nonconstants...
2109 std::vector<Constant*> Indices;
2110 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2111 for (; I != E && isa<Constant>(*I); ++I)
2112 Indices.push_back(cast<Constant>(*I));
2114 if (I == E) { // If they are all constants...
2116 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2118 // Replace all uses of the GEP with the new constexpr...
2119 return ReplaceInstUsesWith(GEP, CE);
2121 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2122 if (CE->getOpcode() == Instruction::Cast) {
2123 if (HasZeroPointerIndex) {
2124 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2125 // into : GEP [10 x ubyte]* X, long 0, ...
2127 // This occurs when the program declares an array extern like "int X[];"
2129 Constant *X = CE->getOperand(0);
2130 const PointerType *CPTy = cast<PointerType>(CE->getType());
2131 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2132 if (const ArrayType *XATy =
2133 dyn_cast<ArrayType>(XTy->getElementType()))
2134 if (const ArrayType *CATy =
2135 dyn_cast<ArrayType>(CPTy->getElementType()))
2136 if (CATy->getElementType() == XATy->getElementType()) {
2137 // At this point, we know that the cast source type is a pointer
2138 // to an array of the same type as the destination pointer
2139 // array. Because the array type is never stepped over (there
2140 // is a leading zero) we can fold the cast into this GEP.
2141 GEP.setOperand(0, X);
2151 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2152 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2153 if (AI.isArrayAllocation()) // Check C != 1
2154 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2155 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2156 AllocationInst *New = 0;
2158 // Create and insert the replacement instruction...
2159 if (isa<MallocInst>(AI))
2160 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
2162 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2163 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
2166 // Scan to the end of the allocation instructions, to skip over a block of
2167 // allocas if possible...
2169 BasicBlock::iterator It = New;
2170 while (isa<AllocationInst>(*It)) ++It;
2172 // Now that I is pointing to the first non-allocation-inst in the block,
2173 // insert our getelementptr instruction...
2175 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
2176 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2178 // Now make everything use the getelementptr instead of the original
2180 ReplaceInstUsesWith(AI, V);
2186 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2187 Value *Op = FI.getOperand(0);
2189 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2190 if (CastInst *CI = dyn_cast<CastInst>(Op))
2191 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2192 FI.setOperand(0, CI->getOperand(0));
2200 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2201 /// constantexpr, return the constant value being addressed by the constant
2202 /// expression, or null if something is funny.
2204 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2205 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
2206 return 0; // Do not allow stepping over the value!
2208 // Loop over all of the operands, tracking down which value we are
2210 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2211 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2212 ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
2213 if (CS == 0) return 0;
2214 if (CU->getValue() >= CS->getValues().size()) return 0;
2215 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2216 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2217 ConstantArray *CA = dyn_cast<ConstantArray>(C);
2218 if (CA == 0) return 0;
2219 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2220 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2226 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2227 Value *Op = LI.getOperand(0);
2228 if (LI.isVolatile()) return 0;
2230 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2231 Op = CPR->getValue();
2233 // Instcombine load (constant global) into the value loaded...
2234 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2235 if (GV->isConstant() && !GV->isExternal())
2236 return ReplaceInstUsesWith(LI, GV->getInitializer());
2238 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2239 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2240 if (CE->getOpcode() == Instruction::GetElementPtr)
2241 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2242 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2243 if (GV->isConstant() && !GV->isExternal())
2244 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2245 return ReplaceInstUsesWith(LI, V);
2250 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2251 // Change br (not X), label True, label False to: br X, label False, True
2252 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
2253 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2254 BasicBlock *TrueDest = BI.getSuccessor(0);
2255 BasicBlock *FalseDest = BI.getSuccessor(1);
2256 // Swap Destinations and condition...
2258 BI.setSuccessor(0, FalseDest);
2259 BI.setSuccessor(1, TrueDest);
2266 void InstCombiner::removeFromWorkList(Instruction *I) {
2267 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2271 bool InstCombiner::runOnFunction(Function &F) {
2272 bool Changed = false;
2273 TD = &getAnalysis<TargetData>();
2275 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2277 while (!WorkList.empty()) {
2278 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2279 WorkList.pop_back();
2281 // Check to see if we can DCE or ConstantPropagate the instruction...
2282 // Check to see if we can DIE the instruction...
2283 if (isInstructionTriviallyDead(I)) {
2284 // Add operands to the worklist...
2285 if (I->getNumOperands() < 4)
2286 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2287 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2288 WorkList.push_back(Op);
2291 I->getParent()->getInstList().erase(I);
2292 removeFromWorkList(I);
2296 // Instruction isn't dead, see if we can constant propagate it...
2297 if (Constant *C = ConstantFoldInstruction(I)) {
2298 // Add operands to the worklist...
2299 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2300 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2301 WorkList.push_back(Op);
2302 ReplaceInstUsesWith(*I, C);
2305 I->getParent()->getInstList().erase(I);
2306 removeFromWorkList(I);
2310 // Now that we have an instruction, try combining it to simplify it...
2311 if (Instruction *Result = visit(*I)) {
2313 // Should we replace the old instruction with a new one?
2315 // Instructions can end up on the worklist more than once. Make sure
2316 // we do not process an instruction that has been deleted.
2317 removeFromWorkList(I);
2319 // Move the name to the new instruction first...
2320 std::string OldName = I->getName(); I->setName("");
2321 Result->setName(OldName);
2323 // Insert the new instruction into the basic block...
2324 BasicBlock *InstParent = I->getParent();
2325 InstParent->getInstList().insert(I, Result);
2327 // Everything uses the new instruction now...
2328 I->replaceAllUsesWith(Result);
2330 // Erase the old instruction.
2331 InstParent->getInstList().erase(I);
2333 BasicBlock::iterator II = I;
2335 // If the instruction was modified, it's possible that it is now dead.
2336 // if so, remove it.
2337 if (dceInstruction(II)) {
2338 // Instructions may end up in the worklist more than once. Erase them
2340 removeFromWorkList(I);
2346 WorkList.push_back(Result);
2347 AddUsesToWorkList(*Result);
2356 Pass *llvm::createInstructionCombiningPass() {
2357 return new InstCombiner();