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 Value *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
129 // ReplaceInstUsesWith - This method is to be used when an instruction is
130 // found to be dead, replacable with another preexisting expression. Here
131 // we add all uses of I to the worklist, replace all uses of I with the new
132 // value, then return I, so that the inst combiner will know that I was
135 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
136 AddUsesToWorkList(I); // Add all modified instrs to worklist
137 I.replaceAllUsesWith(V);
141 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
142 /// InsertBefore instruction. This is specialized a bit to avoid inserting
143 /// casts that are known to not do anything...
145 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
146 Instruction *InsertBefore);
148 // SimplifyCommutative - This performs a few simplifications for commutative
150 bool SimplifyCommutative(BinaryOperator &I);
152 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
153 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
156 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
159 // getComplexity: Assign a complexity or rank value to LLVM Values...
160 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
161 static unsigned getComplexity(Value *V) {
162 if (isa<Instruction>(V)) {
163 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
167 if (isa<Argument>(V)) return 2;
168 return isa<Constant>(V) ? 0 : 1;
171 // isOnlyUse - Return true if this instruction will be deleted if we stop using
173 static bool isOnlyUse(Value *V) {
174 return V->hasOneUse() || isa<Constant>(V);
177 // getSignedIntegralType - Given an unsigned integral type, return the signed
178 // version of it that has the same size.
179 static const Type *getSignedIntegralType(const Type *Ty) {
180 switch (Ty->getPrimitiveID()) {
181 default: assert(0 && "Invalid unsigned integer type!"); abort();
182 case Type::UByteTyID: return Type::SByteTy;
183 case Type::UShortTyID: return Type::ShortTy;
184 case Type::UIntTyID: return Type::IntTy;
185 case Type::ULongTyID: return Type::LongTy;
189 // getPromotedType - Return the specified type promoted as it would be to pass
190 // though a va_arg area...
191 static const Type *getPromotedType(const Type *Ty) {
192 switch (Ty->getPrimitiveID()) {
193 case Type::SByteTyID:
194 case Type::ShortTyID: return Type::IntTy;
195 case Type::UByteTyID:
196 case Type::UShortTyID: return Type::UIntTy;
197 case Type::FloatTyID: return Type::DoubleTy;
202 // SimplifyCommutative - This performs a few simplifications for commutative
205 // 1. Order operands such that they are listed from right (least complex) to
206 // left (most complex). This puts constants before unary operators before
209 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
210 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
212 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
213 bool Changed = false;
214 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
215 Changed = !I.swapOperands();
217 if (!I.isAssociative()) return Changed;
218 Instruction::BinaryOps Opcode = I.getOpcode();
219 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
220 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
221 if (isa<Constant>(I.getOperand(1))) {
222 Constant *Folded = ConstantExpr::get(I.getOpcode(),
223 cast<Constant>(I.getOperand(1)),
224 cast<Constant>(Op->getOperand(1)));
225 I.setOperand(0, Op->getOperand(0));
226 I.setOperand(1, Folded);
228 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
229 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
230 isOnlyUse(Op) && isOnlyUse(Op1)) {
231 Constant *C1 = cast<Constant>(Op->getOperand(1));
232 Constant *C2 = cast<Constant>(Op1->getOperand(1));
234 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
235 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
236 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
239 WorkList.push_back(New);
240 I.setOperand(0, New);
241 I.setOperand(1, Folded);
248 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
249 // if the LHS is a constant zero (which is the 'negate' form).
251 static inline Value *dyn_castNegVal(Value *V) {
252 if (BinaryOperator::isNeg(V))
253 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
255 // Constants can be considered to be negated values if they can be folded...
256 if (Constant *C = dyn_cast<Constant>(V))
257 return ConstantExpr::get(Instruction::Sub,
258 Constant::getNullValue(V->getType()), C);
262 static Constant *NotConstant(Constant *C) {
263 return ConstantExpr::get(Instruction::Xor, C,
264 ConstantIntegral::getAllOnesValue(C->getType()));
267 static inline Value *dyn_castNotVal(Value *V) {
268 if (BinaryOperator::isNot(V))
269 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
271 // Constants can be considered to be not'ed values...
272 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
273 return NotConstant(C);
277 // dyn_castFoldableMul - If this value is a multiply that can be folded into
278 // other computations (because it has a constant operand), return the
279 // non-constant operand of the multiply.
281 static inline Value *dyn_castFoldableMul(Value *V) {
282 if (V->hasOneUse() && V->getType()->isInteger())
283 if (Instruction *I = dyn_cast<Instruction>(V))
284 if (I->getOpcode() == Instruction::Mul)
285 if (isa<Constant>(I->getOperand(1)))
286 return I->getOperand(0);
290 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
291 // a constant, return the constant being anded with.
293 template<class ValueType>
294 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
295 if (Instruction *I = dyn_cast<Instruction>(V))
296 if (I->getOpcode() == Instruction::And)
297 return dyn_cast<Constant>(I->getOperand(1));
299 // If this is a constant, it acts just like we were masking with it.
300 return dyn_cast<Constant>(V);
303 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
305 static unsigned Log2(uint64_t Val) {
306 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
309 if (Val & 1) return 0; // Multiple bits set?
317 /// AssociativeOpt - Perform an optimization on an associative operator. This
318 /// function is designed to check a chain of associative operators for a
319 /// potential to apply a certain optimization. Since the optimization may be
320 /// applicable if the expression was reassociated, this checks the chain, then
321 /// reassociates the expression as necessary to expose the optimization
322 /// opportunity. This makes use of a special Functor, which must define
323 /// 'shouldApply' and 'apply' methods.
325 template<typename Functor>
326 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
327 unsigned Opcode = Root.getOpcode();
328 Value *LHS = Root.getOperand(0);
330 // Quick check, see if the immediate LHS matches...
331 if (F.shouldApply(LHS))
332 return F.apply(Root);
334 // Otherwise, if the LHS is not of the same opcode as the root, return.
335 Instruction *LHSI = dyn_cast<Instruction>(LHS);
336 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
337 // Should we apply this transform to the RHS?
338 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
340 // If not to the RHS, check to see if we should apply to the LHS...
341 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
342 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
346 // If the functor wants to apply the optimization to the RHS of LHSI,
347 // reassociate the expression from ((? op A) op B) to (? op (A op B))
349 BasicBlock *BB = Root.getParent();
350 // All of the instructions have a single use and have no side-effects,
351 // because of this, we can pull them all into the current basic block.
352 if (LHSI->getParent() != BB) {
353 // Move all of the instructions from root to LHSI into the current
355 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
356 Instruction *LastUse = &Root;
357 while (TmpLHSI->getParent() == BB) {
359 TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
362 // Loop over all of the instructions in other blocks, moving them into
364 Value *TmpLHS = TmpLHSI;
366 TmpLHSI = cast<Instruction>(TmpLHS);
367 // Remove from current block...
368 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
369 // Insert before the last instruction...
370 BB->getInstList().insert(LastUse, TmpLHSI);
371 TmpLHS = TmpLHSI->getOperand(0);
372 } while (TmpLHSI != LHSI);
375 // Now all of the instructions are in the current basic block, go ahead
376 // and perform the reassociation.
377 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
379 // First move the selected RHS to the LHS of the root...
380 Root.setOperand(0, LHSI->getOperand(1));
382 // Make what used to be the LHS of the root be the user of the root...
383 Value *ExtraOperand = TmpLHSI->getOperand(1);
384 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
385 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
386 BB->getInstList().remove(&Root); // Remove root from the BB
387 BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
389 // Now propagate the ExtraOperand down the chain of instructions until we
391 while (TmpLHSI != LHSI) {
392 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
393 Value *NextOp = NextLHSI->getOperand(1);
394 NextLHSI->setOperand(1, ExtraOperand);
396 ExtraOperand = NextOp;
399 // Now that the instructions are reassociated, have the functor perform
400 // the transformation...
401 return F.apply(Root);
404 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
410 // AddRHS - Implements: X + X --> X << 1
413 AddRHS(Value *rhs) : RHS(rhs) {}
414 bool shouldApply(Value *LHS) const { return LHS == RHS; }
415 Instruction *apply(BinaryOperator &Add) const {
416 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
417 ConstantInt::get(Type::UByteTy, 1));
421 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
423 struct AddMaskingAnd {
425 AddMaskingAnd(Constant *c) : C2(c) {}
426 bool shouldApply(Value *LHS) const {
427 if (Constant *C1 = dyn_castMaskingAnd(LHS))
428 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
431 Instruction *apply(BinaryOperator &Add) const {
432 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
439 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
440 bool Changed = SimplifyCommutative(I);
441 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
444 if (RHS == Constant::getNullValue(I.getType()))
445 return ReplaceInstUsesWith(I, LHS);
448 if (I.getType()->isInteger())
449 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
452 if (Value *V = dyn_castNegVal(LHS))
453 return BinaryOperator::create(Instruction::Sub, RHS, V);
456 if (!isa<Constant>(RHS))
457 if (Value *V = dyn_castNegVal(RHS))
458 return BinaryOperator::create(Instruction::Sub, LHS, V);
460 // X*C + X --> X * (C+1)
461 if (dyn_castFoldableMul(LHS) == RHS) {
463 ConstantExpr::get(Instruction::Add,
464 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
465 ConstantInt::get(I.getType(), 1));
466 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
469 // X + X*C --> X * (C+1)
470 if (dyn_castFoldableMul(RHS) == LHS) {
472 ConstantExpr::get(Instruction::Add,
473 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
474 ConstantInt::get(I.getType(), 1));
475 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
478 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
479 if (Constant *C2 = dyn_castMaskingAnd(RHS))
480 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
482 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
483 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
484 switch (ILHS->getOpcode()) {
485 case Instruction::Xor:
486 // ~X + C --> (C-1) - X
487 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
488 if (XorRHS->isAllOnesValue())
489 return BinaryOperator::create(Instruction::Sub,
490 ConstantExpr::get(Instruction::Sub,
491 CRHS, ConstantInt::get(I.getType(), 1)),
492 ILHS->getOperand(0));
499 return Changed ? &I : 0;
502 // isSignBit - Return true if the value represented by the constant only has the
503 // highest order bit set.
504 static bool isSignBit(ConstantInt *CI) {
505 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
506 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
509 static unsigned getTypeSizeInBits(const Type *Ty) {
510 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
513 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
514 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
516 if (Op0 == Op1) // sub X, X -> 0
517 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
519 // If this is a 'B = x-(-A)', change to B = x+A...
520 if (Value *V = dyn_castNegVal(Op1))
521 return BinaryOperator::create(Instruction::Add, Op0, V);
523 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
524 // Replace (-1 - A) with (~A)...
525 if (C->isAllOnesValue())
526 return BinaryOperator::createNot(Op1);
528 // C - ~X == X + (1+C)
529 if (BinaryOperator::isNot(Op1))
530 return BinaryOperator::create(Instruction::Add,
531 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
532 ConstantExpr::get(Instruction::Add, C,
533 ConstantInt::get(I.getType(), 1)));
536 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
537 if (Op1I->hasOneUse()) {
538 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
539 // is not used by anyone else...
541 if (Op1I->getOpcode() == Instruction::Sub &&
542 !Op1I->getType()->isFloatingPoint()) {
543 // Swap the two operands of the subexpr...
544 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
545 Op1I->setOperand(0, IIOp1);
546 Op1I->setOperand(1, IIOp0);
548 // Create the new top level add instruction...
549 return BinaryOperator::create(Instruction::Add, Op0, Op1);
552 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
554 if (Op1I->getOpcode() == Instruction::And &&
555 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
556 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
558 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
559 return BinaryOperator::create(Instruction::And, Op0, NewNot);
562 // X - X*C --> X * (1-C)
563 if (dyn_castFoldableMul(Op1I) == Op0) {
565 ConstantExpr::get(Instruction::Sub,
566 ConstantInt::get(I.getType(), 1),
567 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
568 assert(CP1 && "Couldn't constant fold 1-C?");
569 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
573 // X*C - X --> X * (C-1)
574 if (dyn_castFoldableMul(Op0) == Op1) {
576 ConstantExpr::get(Instruction::Sub,
577 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
578 ConstantInt::get(I.getType(), 1));
579 assert(CP1 && "Couldn't constant fold C - 1?");
580 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
586 /// isSignBitCheck - Given an exploded setcc instruction, return true if it is
587 /// really just returns true if the most significant (sign) bit is set.
588 static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
589 if (RHS->getType()->isSigned()) {
590 // True if source is LHS < 0 or LHS <= -1
591 return Opcode == Instruction::SetLT && RHS->isNullValue() ||
592 Opcode == Instruction::SetLE && RHS->isAllOnesValue();
594 ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
595 // True if source is LHS > 127 or LHS >= 128, where the constants depend on
596 // the size of the integer type.
597 if (Opcode == Instruction::SetGE)
598 return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1);
599 if (Opcode == Instruction::SetGT)
600 return RHSC->getValue() ==
601 (1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
606 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
607 bool Changed = SimplifyCommutative(I);
608 Value *Op0 = I.getOperand(0);
610 // Simplify mul instructions with a constant RHS...
611 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
612 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
614 // ((X << C1)*C2) == (X * (C2 << C1))
615 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
616 if (SI->getOpcode() == Instruction::Shl)
617 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
618 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
619 ConstantExpr::get(Instruction::Shl, CI, ShOp));
621 if (CI->isNullValue())
622 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
623 if (CI->equalsInt(1)) // X * 1 == X
624 return ReplaceInstUsesWith(I, Op0);
625 if (CI->isAllOnesValue()) // X * -1 == 0 - X
626 return BinaryOperator::createNeg(Op0, I.getName());
628 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
629 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
630 return new ShiftInst(Instruction::Shl, Op0,
631 ConstantUInt::get(Type::UByteTy, C));
633 ConstantFP *Op1F = cast<ConstantFP>(Op1);
634 if (Op1F->isNullValue())
635 return ReplaceInstUsesWith(I, Op1);
637 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
638 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
639 if (Op1F->getValue() == 1.0)
640 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
644 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
645 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
646 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
648 // If one of the operands of the multiply is a cast from a boolean value, then
649 // we know the bool is either zero or one, so this is a 'masking' multiply.
650 // See if we can simplify things based on how the boolean was originally
652 CastInst *BoolCast = 0;
653 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
654 if (CI->getOperand(0)->getType() == Type::BoolTy)
657 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
658 if (CI->getOperand(0)->getType() == Type::BoolTy)
661 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
662 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
663 const Type *SCOpTy = SCIOp0->getType();
665 // If the setcc is true iff the sign bit of X is set, then convert this
666 // multiply into a shift/and combination.
667 if (isa<ConstantInt>(SCIOp1) &&
668 isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
669 // Shift the X value right to turn it into "all signbits".
670 Constant *Amt = ConstantUInt::get(Type::UByteTy,
671 SCOpTy->getPrimitiveSize()*8-1);
672 if (SCIOp0->getType()->isUnsigned()) {
673 const Type *NewTy = getSignedIntegralType(SCIOp0->getType());
674 SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
675 SCIOp0->getName()), I);
679 InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
680 BoolCast->getOperand(0)->getName()+
683 // If the multiply type is not the same as the source type, sign extend
684 // or truncate to the multiply type.
685 if (I.getType() != V->getType())
686 V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
688 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
689 return BinaryOperator::create(Instruction::And, V, OtherOp);
694 return Changed ? &I : 0;
697 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
699 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
700 if (RHS->equalsInt(1))
701 return ReplaceInstUsesWith(I, I.getOperand(0));
703 // Check to see if this is an unsigned division with an exact power of 2,
704 // if so, convert to a right shift.
705 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
706 if (uint64_t Val = C->getValue()) // Don't break X / 0
707 if (uint64_t C = Log2(Val))
708 return new ShiftInst(Instruction::Shr, I.getOperand(0),
709 ConstantUInt::get(Type::UByteTy, C));
712 // 0 / X == 0, we don't need to preserve faults!
713 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
714 if (LHS->equalsInt(0))
715 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
721 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
722 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
723 if (RHS->equalsInt(1)) // X % 1 == 0
724 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
726 // Check to see if this is an unsigned remainder with an exact power of 2,
727 // if so, convert to a bitwise and.
728 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
729 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
731 return BinaryOperator::create(Instruction::And, I.getOperand(0),
732 ConstantUInt::get(I.getType(), Val-1));
735 // 0 % X == 0, we don't need to preserve faults!
736 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
737 if (LHS->equalsInt(0))
738 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
743 // isMaxValueMinusOne - return true if this is Max-1
744 static bool isMaxValueMinusOne(const ConstantInt *C) {
745 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
746 // Calculate -1 casted to the right type...
747 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
748 uint64_t Val = ~0ULL; // All ones
749 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
750 return CU->getValue() == Val-1;
753 const ConstantSInt *CS = cast<ConstantSInt>(C);
755 // Calculate 0111111111..11111
756 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
757 int64_t Val = INT64_MAX; // All ones
758 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
759 return CS->getValue() == Val-1;
762 // isMinValuePlusOne - return true if this is Min+1
763 static bool isMinValuePlusOne(const ConstantInt *C) {
764 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
765 return CU->getValue() == 1;
767 const ConstantSInt *CS = cast<ConstantSInt>(C);
769 // Calculate 1111111111000000000000
770 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
771 int64_t Val = -1; // All ones
772 Val <<= TypeBits-1; // Shift over to the right spot
773 return CS->getValue() == Val+1;
776 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
777 /// are carefully arranged to allow folding of expressions such as:
779 /// (A < B) | (A > B) --> (A != B)
781 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
782 /// represents that the comparison is true if A == B, and bit value '1' is true
785 static unsigned getSetCondCode(const SetCondInst *SCI) {
786 switch (SCI->getOpcode()) {
788 case Instruction::SetGT: return 1;
789 case Instruction::SetEQ: return 2;
790 case Instruction::SetGE: return 3;
791 case Instruction::SetLT: return 4;
792 case Instruction::SetNE: return 5;
793 case Instruction::SetLE: return 6;
796 assert(0 && "Invalid SetCC opcode!");
801 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
802 /// opcode and two operands into either a constant true or false, or a brand new
803 /// SetCC instruction.
804 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
806 case 0: return ConstantBool::False;
807 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
808 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
809 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
810 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
811 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
812 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
813 case 7: return ConstantBool::True;
814 default: assert(0 && "Illegal SetCCCode!"); return 0;
818 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
819 struct FoldSetCCLogical {
822 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
823 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
824 bool shouldApply(Value *V) const {
825 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
826 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
827 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
830 Instruction *apply(BinaryOperator &Log) const {
831 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
832 if (SCI->getOperand(0) != LHS) {
833 assert(SCI->getOperand(1) == LHS);
834 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
837 unsigned LHSCode = getSetCondCode(SCI);
838 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
840 switch (Log.getOpcode()) {
841 case Instruction::And: Code = LHSCode & RHSCode; break;
842 case Instruction::Or: Code = LHSCode | RHSCode; break;
843 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
844 default: assert(0 && "Illegal logical opcode!"); return 0;
847 Value *RV = getSetCCValue(Code, LHS, RHS);
848 if (Instruction *I = dyn_cast<Instruction>(RV))
850 // Otherwise, it's a constant boolean value...
851 return IC.ReplaceInstUsesWith(Log, RV);
856 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
857 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
858 // guaranteed to be either a shift instruction or a binary operator.
859 Instruction *InstCombiner::OptAndOp(Instruction *Op,
860 ConstantIntegral *OpRHS,
861 ConstantIntegral *AndRHS,
862 BinaryOperator &TheAnd) {
863 Value *X = Op->getOperand(0);
864 Constant *Together = 0;
865 if (!isa<ShiftInst>(Op))
866 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
868 switch (Op->getOpcode()) {
869 case Instruction::Xor:
870 if (Together->isNullValue()) {
871 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
872 return BinaryOperator::create(Instruction::And, X, AndRHS);
873 } else if (Op->hasOneUse()) {
874 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
875 std::string OpName = Op->getName(); Op->setName("");
876 Instruction *And = BinaryOperator::create(Instruction::And,
878 InsertNewInstBefore(And, TheAnd);
879 return BinaryOperator::create(Instruction::Xor, And, Together);
882 case Instruction::Or:
883 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
884 if (Together->isNullValue())
885 return BinaryOperator::create(Instruction::And, X, AndRHS);
887 if (Together == AndRHS) // (X | C) & C --> C
888 return ReplaceInstUsesWith(TheAnd, AndRHS);
890 if (Op->hasOneUse() && Together != OpRHS) {
891 // (X | C1) & C2 --> (X | (C1&C2)) & C2
892 std::string Op0Name = Op->getName(); Op->setName("");
893 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
895 InsertNewInstBefore(Or, TheAnd);
896 return BinaryOperator::create(Instruction::And, Or, AndRHS);
900 case Instruction::Add:
901 if (Op->hasOneUse()) {
902 // Adding a one to a single bit bit-field should be turned into an XOR
903 // of the bit. First thing to check is to see if this AND is with a
904 // single bit constant.
905 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
907 // Clear bits that are not part of the constant.
908 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
910 // If there is only one bit set...
911 if ((AndRHSV & (AndRHSV-1)) == 0) {
912 // Ok, at this point, we know that we are masking the result of the
913 // ADD down to exactly one bit. If the constant we are adding has
914 // no bits set below this bit, then we can eliminate the ADD.
915 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
917 // Check to see if any bits below the one bit set in AndRHSV are set.
918 if ((AddRHS & (AndRHSV-1)) == 0) {
919 // If not, the only thing that can effect the output of the AND is
920 // the bit specified by AndRHSV. If that bit is set, the effect of
921 // the XOR is to toggle the bit. If it is clear, then the ADD has
923 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
924 TheAnd.setOperand(0, X);
927 std::string Name = Op->getName(); Op->setName("");
928 // Pull the XOR out of the AND.
929 Instruction *NewAnd =
930 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
931 InsertNewInstBefore(NewAnd, TheAnd);
932 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
939 case Instruction::Shl: {
940 // We know that the AND will not produce any of the bits shifted in, so if
941 // the anded constant includes them, clear them now!
943 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
944 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
945 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
947 TheAnd.setOperand(1, CI);
952 case Instruction::Shr:
953 // We know that the AND will not produce any of the bits shifted in, so if
954 // the anded constant includes them, clear them now! This only applies to
955 // unsigned shifts, because a signed shr may bring in set bits!
957 if (AndRHS->getType()->isUnsigned()) {
958 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
959 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
960 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
962 TheAnd.setOperand(1, CI);
972 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
973 bool Changed = SimplifyCommutative(I);
974 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
976 // and X, X = X and X, 0 == 0
977 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
978 return ReplaceInstUsesWith(I, Op1);
981 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
982 if (RHS->isAllOnesValue())
983 return ReplaceInstUsesWith(I, Op0);
985 // Optimize a variety of ((val OP C1) & C2) combinations...
986 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
987 Instruction *Op0I = cast<Instruction>(Op0);
988 Value *X = Op0I->getOperand(0);
989 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
990 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
995 Value *Op0NotVal = dyn_castNotVal(Op0);
996 Value *Op1NotVal = dyn_castNotVal(Op1);
998 // (~A & ~B) == (~(A | B)) - Demorgan's Law
999 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1000 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
1001 Op1NotVal,I.getName()+".demorgan");
1002 InsertNewInstBefore(Or, I);
1003 return BinaryOperator::createNot(Or);
1006 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1007 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1009 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1010 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1011 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1014 return Changed ? &I : 0;
1019 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1020 bool Changed = SimplifyCommutative(I);
1021 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1023 // or X, X = X or X, 0 == X
1024 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1025 return ReplaceInstUsesWith(I, Op0);
1028 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1029 if (RHS->isAllOnesValue())
1030 return ReplaceInstUsesWith(I, Op1);
1032 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1033 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1034 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
1035 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1036 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1037 Instruction *Or = BinaryOperator::create(Instruction::Or,
1038 Op0I->getOperand(0), RHS,
1040 InsertNewInstBefore(Or, I);
1041 return BinaryOperator::create(Instruction::And, Or,
1042 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
1045 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1046 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
1047 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1048 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1049 Instruction *Or = BinaryOperator::create(Instruction::Or,
1050 Op0I->getOperand(0), RHS,
1052 InsertNewInstBefore(Or, I);
1053 return BinaryOperator::create(Instruction::Xor, Or,
1054 ConstantExpr::get(Instruction::And, Op0CI,
1060 // (A & C1)|(A & C2) == A & (C1|C2)
1061 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
1062 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
1063 if (LHS->getOperand(0) == RHS->getOperand(0))
1064 if (Constant *C0 = dyn_castMaskingAnd(LHS))
1065 if (Constant *C1 = dyn_castMaskingAnd(RHS))
1066 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
1067 ConstantExpr::get(Instruction::Or, C0, C1));
1069 Value *Op0NotVal = dyn_castNotVal(Op0);
1070 Value *Op1NotVal = dyn_castNotVal(Op1);
1072 if (Op1 == Op0NotVal) // ~A | A == -1
1073 return ReplaceInstUsesWith(I,
1074 ConstantIntegral::getAllOnesValue(I.getType()));
1076 if (Op0 == Op1NotVal) // A | ~A == -1
1077 return ReplaceInstUsesWith(I,
1078 ConstantIntegral::getAllOnesValue(I.getType()));
1080 // (~A | ~B) == (~(A & B)) - Demorgan's Law
1081 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1082 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
1083 Op1NotVal,I.getName()+".demorgan",
1085 WorkList.push_back(And);
1086 return BinaryOperator::createNot(And);
1089 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1090 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1091 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1094 return Changed ? &I : 0;
1097 // XorSelf - Implements: X ^ X --> 0
1100 XorSelf(Value *rhs) : RHS(rhs) {}
1101 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1102 Instruction *apply(BinaryOperator &Xor) const {
1108 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1109 bool Changed = SimplifyCommutative(I);
1110 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1112 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1113 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1114 assert(Result == &I && "AssociativeOpt didn't work?");
1115 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1118 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1120 if (RHS->isNullValue())
1121 return ReplaceInstUsesWith(I, Op0);
1123 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1124 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1125 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1126 if (RHS == ConstantBool::True && SCI->hasOneUse())
1127 return new SetCondInst(SCI->getInverseCondition(),
1128 SCI->getOperand(0), SCI->getOperand(1));
1130 // ~(c-X) == X-c-1 == X+(-c-1)
1131 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1132 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1133 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1134 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1135 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1136 ConstantInt::get(I.getType(), 1));
1137 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1141 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1142 switch (Op0I->getOpcode()) {
1143 case Instruction::Add:
1144 // ~(X-c) --> (-c-1)-X
1145 if (RHS->isAllOnesValue()) {
1146 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1147 Constant::getNullValue(Op0CI->getType()), Op0CI);
1148 return BinaryOperator::create(Instruction::Sub,
1149 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1150 ConstantInt::get(I.getType(), 1)),
1151 Op0I->getOperand(0));
1154 case Instruction::And:
1155 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1156 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1157 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1159 case Instruction::Or:
1160 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1161 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1162 return BinaryOperator::create(Instruction::And, Op0,
1170 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1172 return ReplaceInstUsesWith(I,
1173 ConstantIntegral::getAllOnesValue(I.getType()));
1175 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1177 return ReplaceInstUsesWith(I,
1178 ConstantIntegral::getAllOnesValue(I.getType()));
1180 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1181 if (Op1I->getOpcode() == Instruction::Or) {
1182 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1183 cast<BinaryOperator>(Op1I)->swapOperands();
1185 std::swap(Op0, Op1);
1186 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1188 std::swap(Op0, Op1);
1190 } else if (Op1I->getOpcode() == Instruction::Xor) {
1191 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1192 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1193 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1194 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1197 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1198 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1199 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1200 cast<BinaryOperator>(Op0I)->swapOperands();
1201 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1202 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1203 WorkList.push_back(cast<Instruction>(NotB));
1204 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1207 } else if (Op0I->getOpcode() == Instruction::Xor) {
1208 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1209 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1210 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1211 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1214 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1215 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1216 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1217 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1218 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1220 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1221 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1222 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1225 return Changed ? &I : 0;
1228 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1229 static Constant *AddOne(ConstantInt *C) {
1230 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1231 ConstantInt::get(C->getType(), 1));
1232 assert(Result && "Constant folding integer addition failed!");
1235 static Constant *SubOne(ConstantInt *C) {
1236 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1237 ConstantInt::get(C->getType(), 1));
1238 assert(Result && "Constant folding integer addition failed!");
1242 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1243 // true when both operands are equal...
1245 static bool isTrueWhenEqual(Instruction &I) {
1246 return I.getOpcode() == Instruction::SetEQ ||
1247 I.getOpcode() == Instruction::SetGE ||
1248 I.getOpcode() == Instruction::SetLE;
1251 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1252 bool Changed = SimplifyCommutative(I);
1253 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1254 const Type *Ty = Op0->getType();
1258 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1260 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1261 if (isa<ConstantPointerNull>(Op1) &&
1262 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1263 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1266 // setcc's with boolean values can always be turned into bitwise operations
1267 if (Ty == Type::BoolTy) {
1268 // If this is <, >, or !=, we can change this into a simple xor instruction
1269 if (!isTrueWhenEqual(I))
1270 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1272 // Otherwise we need to make a temporary intermediate instruction and insert
1273 // it into the instruction stream. This is what we are after:
1275 // seteq bool %A, %B -> ~(A^B)
1276 // setle bool %A, %B -> ~A | B
1277 // setge bool %A, %B -> A | ~B
1279 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1280 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1282 InsertNewInstBefore(Xor, I);
1283 return BinaryOperator::createNot(Xor);
1286 // Handle the setXe cases...
1287 assert(I.getOpcode() == Instruction::SetGE ||
1288 I.getOpcode() == Instruction::SetLE);
1290 if (I.getOpcode() == Instruction::SetGE)
1291 std::swap(Op0, Op1); // Change setge -> setle
1293 // Now we just have the SetLE case.
1294 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1295 InsertNewInstBefore(Not, I);
1296 return BinaryOperator::create(Instruction::Or, Not, Op1);
1299 // Check to see if we are doing one of many comparisons against constant
1300 // integers at the end of their ranges...
1302 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1303 // Simplify seteq and setne instructions...
1304 if (I.getOpcode() == Instruction::SetEQ ||
1305 I.getOpcode() == Instruction::SetNE) {
1306 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1308 // If the first operand is (and|or|xor) with a constant, and the second
1309 // operand is a constant, simplify a bit.
1310 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1311 switch (BO->getOpcode()) {
1312 case Instruction::Add:
1313 if (CI->isNullValue()) {
1314 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1315 // efficiently invertible, or if the add has just this one use.
1316 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1317 if (Value *NegVal = dyn_castNegVal(BOp1))
1318 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1319 else if (Value *NegVal = dyn_castNegVal(BOp0))
1320 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1321 else if (BO->hasOneUse()) {
1322 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1324 InsertNewInstBefore(Neg, I);
1325 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1329 case Instruction::Xor:
1330 // For the xor case, we can xor two constants together, eliminating
1331 // the explicit xor.
1332 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1333 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1334 ConstantExpr::get(Instruction::Xor, CI, BOC));
1337 case Instruction::Sub:
1338 // Replace (([sub|xor] A, B) != 0) with (A != B)
1339 if (CI->isNullValue())
1340 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1344 case Instruction::Or:
1345 // If bits are being or'd in that are not present in the constant we
1346 // are comparing against, then the comparison could never succeed!
1347 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1348 Constant *NotCI = NotConstant(CI);
1349 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1350 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1354 case Instruction::And:
1355 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1356 // If bits are being compared against that are and'd out, then the
1357 // comparison can never succeed!
1358 if (!ConstantExpr::get(Instruction::And, CI,
1359 NotConstant(BOC))->isNullValue())
1360 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1362 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1363 // to be a signed value as appropriate.
1364 if (isSignBit(BOC)) {
1365 Value *X = BO->getOperand(0);
1366 // If 'X' is not signed, insert a cast now...
1367 if (!BOC->getType()->isSigned()) {
1368 const Type *DestTy = getSignedIntegralType(BOC->getType());
1369 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1370 InsertNewInstBefore(NewCI, I);
1373 return new SetCondInst(isSetNE ? Instruction::SetLT :
1374 Instruction::SetGE, X,
1375 Constant::getNullValue(X->getType()));
1381 } else { // Not a SetEQ/SetNE
1382 // If the LHS is a cast from an integral value of the same size,
1383 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
1384 Value *CastOp = Cast->getOperand(0);
1385 const Type *SrcTy = CastOp->getType();
1386 unsigned SrcTySize = SrcTy->getPrimitiveSize();
1387 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
1388 SrcTySize == Cast->getType()->getPrimitiveSize()) {
1389 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
1390 "Source and destination signednesses should differ!");
1391 if (Cast->getType()->isSigned()) {
1392 // If this is a signed comparison, check for comparisons in the
1393 // vicinity of zero.
1394 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
1396 return BinaryOperator::create(Instruction::SetGT, CastOp,
1397 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
1398 else if (I.getOpcode() == Instruction::SetGT &&
1399 cast<ConstantSInt>(CI)->getValue() == -1)
1400 // X > -1 => x < 128
1401 return BinaryOperator::create(Instruction::SetLT, CastOp,
1402 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
1404 ConstantUInt *CUI = cast<ConstantUInt>(CI);
1405 if (I.getOpcode() == Instruction::SetLT &&
1406 CUI->getValue() == 1ULL << (SrcTySize*8-1))
1407 // X < 128 => X > -1
1408 return BinaryOperator::create(Instruction::SetGT, CastOp,
1409 ConstantSInt::get(SrcTy, -1));
1410 else if (I.getOpcode() == Instruction::SetGT &&
1411 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
1413 return BinaryOperator::create(Instruction::SetLT, CastOp,
1414 Constant::getNullValue(SrcTy));
1420 // Check to see if we are comparing against the minimum or maximum value...
1421 if (CI->isMinValue()) {
1422 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1423 return ReplaceInstUsesWith(I, ConstantBool::False);
1424 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1425 return ReplaceInstUsesWith(I, ConstantBool::True);
1426 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1427 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1428 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1429 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1431 } else if (CI->isMaxValue()) {
1432 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1433 return ReplaceInstUsesWith(I, ConstantBool::False);
1434 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1435 return ReplaceInstUsesWith(I, ConstantBool::True);
1436 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1437 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1438 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1439 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1441 // Comparing against a value really close to min or max?
1442 } else if (isMinValuePlusOne(CI)) {
1443 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1444 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1445 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1446 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1448 } else if (isMaxValueMinusOne(CI)) {
1449 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1450 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1451 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1452 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1455 // If we still have a setle or setge instruction, turn it into the
1456 // appropriate setlt or setgt instruction. Since the border cases have
1457 // already been handled above, this requires little checking.
1459 if (I.getOpcode() == Instruction::SetLE)
1460 return BinaryOperator::create(Instruction::SetLT, Op0, AddOne(CI));
1461 if (I.getOpcode() == Instruction::SetGE)
1462 return BinaryOperator::create(Instruction::SetGT, Op0, SubOne(CI));
1465 // Test to see if the operands of the setcc are casted versions of other
1466 // values. If the cast can be stripped off both arguments, we do so now.
1467 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1468 Value *CastOp0 = CI->getOperand(0);
1469 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1470 !isa<Argument>(Op1) &&
1471 (I.getOpcode() == Instruction::SetEQ ||
1472 I.getOpcode() == Instruction::SetNE)) {
1473 // We keep moving the cast from the left operand over to the right
1474 // operand, where it can often be eliminated completely.
1477 // If operand #1 is a cast instruction, see if we can eliminate it as
1479 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1480 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1482 Op1 = CI2->getOperand(0);
1484 // If Op1 is a constant, we can fold the cast into the constant.
1485 if (Op1->getType() != Op0->getType())
1486 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1487 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1489 // Otherwise, cast the RHS right before the setcc
1490 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1491 InsertNewInstBefore(cast<Instruction>(Op1), I);
1493 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1496 // Handle the special case of: setcc (cast bool to X), <cst>
1497 // This comes up when you have code like
1500 // For generality, we handle any zero-extension of any operand comparison
1502 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1503 const Type *SrcTy = CastOp0->getType();
1504 const Type *DestTy = Op0->getType();
1505 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1506 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1507 // Ok, we have an expansion of operand 0 into a new type. Get the
1508 // constant value, masink off bits which are not set in the RHS. These
1509 // could be set if the destination value is signed.
1510 uint64_t ConstVal = ConstantRHS->getRawValue();
1511 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1513 // If the constant we are comparing it with has high bits set, which
1514 // don't exist in the original value, the values could never be equal,
1515 // because the source would be zero extended.
1517 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1518 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1519 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1520 switch (I.getOpcode()) {
1521 default: assert(0 && "Unknown comparison type!");
1522 case Instruction::SetEQ:
1523 return ReplaceInstUsesWith(I, ConstantBool::False);
1524 case Instruction::SetNE:
1525 return ReplaceInstUsesWith(I, ConstantBool::True);
1526 case Instruction::SetLT:
1527 case Instruction::SetLE:
1528 if (DestTy->isSigned() && HasSignBit)
1529 return ReplaceInstUsesWith(I, ConstantBool::False);
1530 return ReplaceInstUsesWith(I, ConstantBool::True);
1531 case Instruction::SetGT:
1532 case Instruction::SetGE:
1533 if (DestTy->isSigned() && HasSignBit)
1534 return ReplaceInstUsesWith(I, ConstantBool::True);
1535 return ReplaceInstUsesWith(I, ConstantBool::False);
1539 // Otherwise, we can replace the setcc with a setcc of the smaller
1541 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1542 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1546 return Changed ? &I : 0;
1551 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1552 assert(I.getOperand(1)->getType() == Type::UByteTy);
1553 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1554 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1556 // shl X, 0 == X and shr X, 0 == X
1557 // shl 0, X == 0 and shr 0, X == 0
1558 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1559 Op0 == Constant::getNullValue(Op0->getType()))
1560 return ReplaceInstUsesWith(I, Op0);
1562 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1564 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1565 if (CSI->isAllOnesValue())
1566 return ReplaceInstUsesWith(I, CSI);
1568 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1569 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1570 // of a signed value.
1572 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1573 if (CUI->getValue() >= TypeBits) {
1574 if (!Op0->getType()->isSigned() || isLeftShift)
1575 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1577 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
1582 // ((X*C1) << C2) == (X * (C1 << C2))
1583 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1584 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1585 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1586 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1587 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1590 // If the operand is an bitwise operator with a constant RHS, and the
1591 // shift is the only use, we can pull it out of the shift.
1592 if (Op0->hasOneUse())
1593 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1594 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1595 bool isValid = true; // Valid only for And, Or, Xor
1596 bool highBitSet = false; // Transform if high bit of constant set?
1598 switch (Op0BO->getOpcode()) {
1599 default: isValid = false; break; // Do not perform transform!
1600 case Instruction::Or:
1601 case Instruction::Xor:
1604 case Instruction::And:
1609 // If this is a signed shift right, and the high bit is modified
1610 // by the logical operation, do not perform the transformation.
1611 // The highBitSet boolean indicates the value of the high bit of
1612 // the constant which would cause it to be modified for this
1615 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1616 uint64_t Val = Op0C->getRawValue();
1617 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1621 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1623 Instruction *NewShift =
1624 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1627 InsertNewInstBefore(NewShift, I);
1629 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1634 // If this is a shift of a shift, see if we can fold the two together...
1635 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1636 if (ConstantUInt *ShiftAmt1C =
1637 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1638 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1639 unsigned ShiftAmt2 = CUI->getValue();
1641 // Check for (A << c1) << c2 and (A >> c1) >> c2
1642 if (I.getOpcode() == Op0SI->getOpcode()) {
1643 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1644 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
1645 Amt = Op0->getType()->getPrimitiveSize()*8;
1646 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1647 ConstantUInt::get(Type::UByteTy, Amt));
1650 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1651 // signed types, we can only support the (A >> c1) << c2 configuration,
1652 // because it can not turn an arbitrary bit of A into a sign bit.
1653 if (I.getType()->isUnsigned() || isLeftShift) {
1654 // Calculate bitmask for what gets shifted off the edge...
1655 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1657 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1659 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1662 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1663 C, Op0SI->getOperand(0)->getName()+".mask");
1664 InsertNewInstBefore(Mask, I);
1666 // Figure out what flavor of shift we should use...
1667 if (ShiftAmt1 == ShiftAmt2)
1668 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1669 else if (ShiftAmt1 < ShiftAmt2) {
1670 return new ShiftInst(I.getOpcode(), Mask,
1671 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1673 return new ShiftInst(Op0SI->getOpcode(), Mask,
1674 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1684 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1687 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1688 const Type *DstTy) {
1690 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1691 // are identical and the bits don't get reinterpreted (for example
1692 // int->float->int would not be allowed)
1693 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1696 // Allow free casting and conversion of sizes as long as the sign doesn't
1698 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1699 unsigned SrcSize = SrcTy->getPrimitiveSize();
1700 unsigned MidSize = MidTy->getPrimitiveSize();
1701 unsigned DstSize = DstTy->getPrimitiveSize();
1703 // Cases where we are monotonically decreasing the size of the type are
1704 // always ok, regardless of what sign changes are going on.
1706 if (SrcSize >= MidSize && MidSize >= DstSize)
1709 // Cases where the source and destination type are the same, but the middle
1710 // type is bigger are noops.
1712 if (SrcSize == DstSize && MidSize > SrcSize)
1715 // If we are monotonically growing, things are more complex.
1717 if (SrcSize <= MidSize && MidSize <= DstSize) {
1718 // We have eight combinations of signedness to worry about. Here's the
1720 static const int SignTable[8] = {
1721 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1722 1, // U U U Always ok
1723 1, // U U S Always ok
1724 3, // U S U Ok iff SrcSize != MidSize
1725 3, // U S S Ok iff SrcSize != MidSize
1726 0, // S U U Never ok
1727 2, // S U S Ok iff MidSize == DstSize
1728 1, // S S U Always ok
1729 1, // S S S Always ok
1732 // Choose an action based on the current entry of the signtable that this
1733 // cast of cast refers to...
1734 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1735 switch (SignTable[Row]) {
1736 case 0: return false; // Never ok
1737 case 1: return true; // Always ok
1738 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1739 case 3: // Ok iff SrcSize != MidSize
1740 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1741 default: assert(0 && "Bad entry in sign table!");
1746 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1747 // like: short -> ushort -> uint, because this can create wrong results if
1748 // the input short is negative!
1753 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1754 if (V->getType() == Ty || isa<Constant>(V)) return false;
1755 if (const CastInst *CI = dyn_cast<CastInst>(V))
1756 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1761 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1762 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1763 /// casts that are known to not do anything...
1765 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1766 Instruction *InsertBefore) {
1767 if (V->getType() == DestTy) return V;
1768 if (Constant *C = dyn_cast<Constant>(V))
1769 return ConstantExpr::getCast(C, DestTy);
1771 CastInst *CI = new CastInst(V, DestTy, V->getName());
1772 InsertNewInstBefore(CI, *InsertBefore);
1776 // CastInst simplification
1778 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1779 Value *Src = CI.getOperand(0);
1781 // If the user is casting a value to the same type, eliminate this cast
1783 if (CI.getType() == Src->getType())
1784 return ReplaceInstUsesWith(CI, Src);
1786 // If casting the result of another cast instruction, try to eliminate this
1789 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1790 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1791 CSrc->getType(), CI.getType())) {
1792 // This instruction now refers directly to the cast's src operand. This
1793 // has a good chance of making CSrc dead.
1794 CI.setOperand(0, CSrc->getOperand(0));
1798 // If this is an A->B->A cast, and we are dealing with integral types, try
1799 // to convert this into a logical 'and' instruction.
1801 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1802 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1803 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1804 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1805 assert(CSrc->getType() != Type::ULongTy &&
1806 "Cannot have type bigger than ulong!");
1807 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1808 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1809 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1814 // If casting the result of a getelementptr instruction with no offset, turn
1815 // this into a cast of the original pointer!
1817 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1818 bool AllZeroOperands = true;
1819 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1820 if (!isa<Constant>(GEP->getOperand(i)) ||
1821 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1822 AllZeroOperands = false;
1825 if (AllZeroOperands) {
1826 CI.setOperand(0, GEP->getOperand(0));
1831 // If we are casting a malloc or alloca to a pointer to a type of the same
1832 // size, rewrite the allocation instruction to allocate the "right" type.
1834 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1835 if (AI->hasOneUse() && !AI->isArrayAllocation())
1836 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1837 // Get the type really allocated and the type casted to...
1838 const Type *AllocElTy = AI->getAllocatedType();
1839 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1840 const Type *CastElTy = PTy->getElementType();
1841 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1843 // If the allocation is for an even multiple of the cast type size
1844 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1845 Value *Amt = ConstantUInt::get(Type::UIntTy,
1846 AllocElTySize/CastElTySize);
1847 std::string Name = AI->getName(); AI->setName("");
1848 AllocationInst *New;
1849 if (isa<MallocInst>(AI))
1850 New = new MallocInst(CastElTy, Amt, Name);
1852 New = new AllocaInst(CastElTy, Amt, Name);
1853 InsertNewInstBefore(New, CI);
1854 return ReplaceInstUsesWith(CI, New);
1858 // If the source value is an instruction with only this use, we can attempt to
1859 // propagate the cast into the instruction. Also, only handle integral types
1861 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1862 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1863 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1864 const Type *DestTy = CI.getType();
1865 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1866 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1868 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1869 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1871 switch (SrcI->getOpcode()) {
1872 case Instruction::Add:
1873 case Instruction::Mul:
1874 case Instruction::And:
1875 case Instruction::Or:
1876 case Instruction::Xor:
1877 // If we are discarding information, or just changing the sign, rewrite.
1878 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1879 // Don't insert two casts if they cannot be eliminated. We allow two
1880 // casts to be inserted if the sizes are the same. This could only be
1881 // converting signedness, which is a noop.
1882 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1883 !ValueRequiresCast(Op0, DestTy)) {
1884 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1885 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1886 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1887 ->getOpcode(), Op0c, Op1c);
1891 case Instruction::Shl:
1892 // Allow changing the sign of the source operand. Do not allow changing
1893 // the size of the shift, UNLESS the shift amount is a constant. We
1894 // mush not change variable sized shifts to a smaller size, because it
1895 // is undefined to shift more bits out than exist in the value.
1896 if (DestBitSize == SrcBitSize ||
1897 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1898 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1899 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1908 // CallInst simplification
1910 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1911 return visitCallSite(&CI);
1914 // InvokeInst simplification
1916 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1917 return visitCallSite(&II);
1920 // visitCallSite - Improvements for call and invoke instructions.
1922 Instruction *InstCombiner::visitCallSite(CallSite CS) {
1923 bool Changed = false;
1925 // If the callee is a constexpr cast of a function, attempt to move the cast
1926 // to the arguments of the call/invoke.
1927 if (transformConstExprCastCall(CS)) return 0;
1929 Value *Callee = CS.getCalledValue();
1930 const PointerType *PTy = cast<PointerType>(Callee->getType());
1931 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1932 if (FTy->isVarArg()) {
1933 // See if we can optimize any arguments passed through the varargs area of
1935 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
1936 E = CS.arg_end(); I != E; ++I)
1937 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
1938 // If this cast does not effect the value passed through the varargs
1939 // area, we can eliminate the use of the cast.
1940 Value *Op = CI->getOperand(0);
1941 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
1948 return Changed ? CS.getInstruction() : 0;
1951 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1952 // attempt to move the cast to the arguments of the call/invoke.
1954 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1955 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1956 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1957 if (CE->getOpcode() != Instruction::Cast ||
1958 !isa<ConstantPointerRef>(CE->getOperand(0)))
1960 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1961 if (!isa<Function>(CPR->getValue())) return false;
1962 Function *Callee = cast<Function>(CPR->getValue());
1963 Instruction *Caller = CS.getInstruction();
1965 // Okay, this is a cast from a function to a different type. Unless doing so
1966 // would cause a type conversion of one of our arguments, change this call to
1967 // be a direct call with arguments casted to the appropriate types.
1969 const FunctionType *FT = Callee->getFunctionType();
1970 const Type *OldRetTy = Caller->getType();
1972 // Check to see if we are changing the return type...
1973 if (OldRetTy != FT->getReturnType()) {
1974 if (Callee->isExternal() &&
1975 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
1976 !Caller->use_empty())
1977 return false; // Cannot transform this return value...
1979 // If the callsite is an invoke instruction, and the return value is used by
1980 // a PHI node in a successor, we cannot change the return type of the call
1981 // because there is no place to put the cast instruction (without breaking
1982 // the critical edge). Bail out in this case.
1983 if (!Caller->use_empty())
1984 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
1985 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
1987 if (PHINode *PN = dyn_cast<PHINode>(*UI))
1988 if (PN->getParent() == II->getNormalDest() ||
1989 PN->getParent() == II->getUnwindDest())
1993 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1994 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1996 CallSite::arg_iterator AI = CS.arg_begin();
1997 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1998 const Type *ParamTy = FT->getParamType(i);
1999 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
2000 if (Callee->isExternal() && !isConvertible) return false;
2003 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
2004 Callee->isExternal())
2005 return false; // Do not delete arguments unless we have a function body...
2007 // Okay, we decided that this is a safe thing to do: go ahead and start
2008 // inserting cast instructions as necessary...
2009 std::vector<Value*> Args;
2010 Args.reserve(NumActualArgs);
2012 AI = CS.arg_begin();
2013 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
2014 const Type *ParamTy = FT->getParamType(i);
2015 if ((*AI)->getType() == ParamTy) {
2016 Args.push_back(*AI);
2018 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
2019 InsertNewInstBefore(Cast, *Caller);
2020 Args.push_back(Cast);
2024 // If the function takes more arguments than the call was taking, add them
2026 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
2027 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
2029 // If we are removing arguments to the function, emit an obnoxious warning...
2030 if (FT->getNumParams() < NumActualArgs)
2031 if (!FT->isVarArg()) {
2032 std::cerr << "WARNING: While resolving call to function '"
2033 << Callee->getName() << "' arguments were dropped!\n";
2035 // Add all of the arguments in their promoted form to the arg list...
2036 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
2037 const Type *PTy = getPromotedType((*AI)->getType());
2038 if (PTy != (*AI)->getType()) {
2039 // Must promote to pass through va_arg area!
2040 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
2041 InsertNewInstBefore(Cast, *Caller);
2042 Args.push_back(Cast);
2044 Args.push_back(*AI);
2049 if (FT->getReturnType() == Type::VoidTy)
2050 Caller->setName(""); // Void type should not have a name...
2053 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2054 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
2055 Args, Caller->getName(), Caller);
2057 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
2060 // Insert a cast of the return type as necessary...
2062 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
2063 if (NV->getType() != Type::VoidTy) {
2064 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
2066 // If this is an invoke instruction, we should insert it after the first
2067 // non-phi, instruction in the normal successor block.
2068 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2069 BasicBlock::iterator I = II->getNormalDest()->begin();
2070 while (isa<PHINode>(I)) ++I;
2071 InsertNewInstBefore(NC, *I);
2073 // Otherwise, it's a call, just insert cast right after the call instr
2074 InsertNewInstBefore(NC, *Caller);
2076 AddUsesToWorkList(*Caller);
2078 NV = Constant::getNullValue(Caller->getType());
2082 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
2083 Caller->replaceAllUsesWith(NV);
2084 Caller->getParent()->getInstList().erase(Caller);
2085 removeFromWorkList(Caller);
2091 // PHINode simplification
2093 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2094 if (Value *V = hasConstantValue(&PN))
2095 return ReplaceInstUsesWith(PN, V);
2097 // If the only user of this instruction is a cast instruction, and all of the
2098 // incoming values are constants, change this PHI to merge together the casted
2101 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2102 if (CI->getType() != PN.getType()) { // noop casts will be folded
2103 bool AllConstant = true;
2104 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2105 if (!isa<Constant>(PN.getIncomingValue(i))) {
2106 AllConstant = false;
2110 // Make a new PHI with all casted values.
2111 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2112 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2113 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2114 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2115 PN.getIncomingBlock(i));
2118 // Update the cast instruction.
2119 CI->setOperand(0, New);
2120 WorkList.push_back(CI); // revisit the cast instruction to fold.
2121 WorkList.push_back(New); // Make sure to revisit the new Phi
2122 return &PN; // PN is now dead!
2129 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2130 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2131 // If so, eliminate the noop.
2132 if (GEP.getNumOperands() == 1)
2133 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2135 bool HasZeroPointerIndex = false;
2136 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2137 HasZeroPointerIndex = C->isNullValue();
2139 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2140 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2142 // Combine Indices - If the source pointer to this getelementptr instruction
2143 // is a getelementptr instruction, combine the indices of the two
2144 // getelementptr instructions into a single instruction.
2146 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
2147 std::vector<Value *> Indices;
2149 // Can we combine the two pointer arithmetics offsets?
2150 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
2151 isa<Constant>(GEP.getOperand(1))) {
2152 // Replace: gep (gep %P, long C1), long C2, ...
2153 // With: gep %P, long (C1+C2), ...
2154 Value *Sum = ConstantExpr::get(Instruction::Add,
2155 cast<Constant>(Src->getOperand(1)),
2156 cast<Constant>(GEP.getOperand(1)));
2157 assert(Sum && "Constant folding of longs failed!?");
2158 GEP.setOperand(0, Src->getOperand(0));
2159 GEP.setOperand(1, Sum);
2160 AddUsesToWorkList(*Src); // Reduce use count of Src
2162 } else if (Src->getNumOperands() == 2) {
2163 // Replace: gep (gep %P, long B), long A, ...
2164 // With: T = long A+B; gep %P, T, ...
2166 // Note that if our source is a gep chain itself that we wait for that
2167 // chain to be resolved before we perform this transformation. This
2168 // avoids us creating a TON of code in some cases.
2170 if (isa<GetElementPtrInst>(Src->getOperand(0)) &&
2171 cast<Instruction>(Src->getOperand(0))->getNumOperands() == 2)
2172 return 0; // Wait until our source is folded to completion.
2174 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
2176 Src->getName()+".sum", &GEP);
2177 GEP.setOperand(0, Src->getOperand(0));
2178 GEP.setOperand(1, Sum);
2179 WorkList.push_back(cast<Instruction>(Sum));
2181 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
2182 Src->getNumOperands() != 1) {
2183 // Otherwise we can do the fold if the first index of the GEP is a zero
2184 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
2185 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2186 } else if (Src->getOperand(Src->getNumOperands()-1) ==
2187 Constant::getNullValue(Type::LongTy)) {
2188 // If the src gep ends with a constant array index, merge this get into
2189 // it, even if we have a non-zero array index.
2190 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
2191 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
2194 if (!Indices.empty())
2195 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
2197 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
2198 // GEP of global variable. If all of the indices for this GEP are
2199 // constants, we can promote this to a constexpr instead of an instruction.
2201 // Scan for nonconstants...
2202 std::vector<Constant*> Indices;
2203 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2204 for (; I != E && isa<Constant>(*I); ++I)
2205 Indices.push_back(cast<Constant>(*I));
2207 if (I == E) { // If they are all constants...
2209 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2211 // Replace all uses of the GEP with the new constexpr...
2212 return ReplaceInstUsesWith(GEP, CE);
2214 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2215 if (CE->getOpcode() == Instruction::Cast) {
2216 if (HasZeroPointerIndex) {
2217 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2218 // into : GEP [10 x ubyte]* X, long 0, ...
2220 // This occurs when the program declares an array extern like "int X[];"
2222 Constant *X = CE->getOperand(0);
2223 const PointerType *CPTy = cast<PointerType>(CE->getType());
2224 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2225 if (const ArrayType *XATy =
2226 dyn_cast<ArrayType>(XTy->getElementType()))
2227 if (const ArrayType *CATy =
2228 dyn_cast<ArrayType>(CPTy->getElementType()))
2229 if (CATy->getElementType() == XATy->getElementType()) {
2230 // At this point, we know that the cast source type is a pointer
2231 // to an array of the same type as the destination pointer
2232 // array. Because the array type is never stepped over (there
2233 // is a leading zero) we can fold the cast into this GEP.
2234 GEP.setOperand(0, X);
2244 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2245 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2246 if (AI.isArrayAllocation()) // Check C != 1
2247 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2248 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2249 AllocationInst *New = 0;
2251 // Create and insert the replacement instruction...
2252 if (isa<MallocInst>(AI))
2253 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
2255 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2256 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
2259 // Scan to the end of the allocation instructions, to skip over a block of
2260 // allocas if possible...
2262 BasicBlock::iterator It = New;
2263 while (isa<AllocationInst>(*It)) ++It;
2265 // Now that I is pointing to the first non-allocation-inst in the block,
2266 // insert our getelementptr instruction...
2268 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
2269 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2271 // Now make everything use the getelementptr instead of the original
2273 ReplaceInstUsesWith(AI, V);
2279 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2280 Value *Op = FI.getOperand(0);
2282 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2283 if (CastInst *CI = dyn_cast<CastInst>(Op))
2284 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2285 FI.setOperand(0, CI->getOperand(0));
2293 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2294 /// constantexpr, return the constant value being addressed by the constant
2295 /// expression, or null if something is funny.
2297 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2298 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
2299 return 0; // Do not allow stepping over the value!
2301 // Loop over all of the operands, tracking down which value we are
2303 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2304 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2305 ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
2306 if (CS == 0) return 0;
2307 if (CU->getValue() >= CS->getValues().size()) return 0;
2308 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2309 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2310 ConstantArray *CA = dyn_cast<ConstantArray>(C);
2311 if (CA == 0) return 0;
2312 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2313 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2319 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2320 Value *Op = LI.getOperand(0);
2321 if (LI.isVolatile()) return 0;
2323 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2324 Op = CPR->getValue();
2326 // Instcombine load (constant global) into the value loaded...
2327 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2328 if (GV->isConstant() && !GV->isExternal())
2329 return ReplaceInstUsesWith(LI, GV->getInitializer());
2331 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2332 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2333 if (CE->getOpcode() == Instruction::GetElementPtr)
2334 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2335 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2336 if (GV->isConstant() && !GV->isExternal())
2337 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2338 return ReplaceInstUsesWith(LI, V);
2343 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2344 // Change br (not X), label True, label False to: br X, label False, True
2345 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
2346 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2347 BasicBlock *TrueDest = BI.getSuccessor(0);
2348 BasicBlock *FalseDest = BI.getSuccessor(1);
2349 // Swap Destinations and condition...
2351 BI.setSuccessor(0, FalseDest);
2352 BI.setSuccessor(1, TrueDest);
2359 void InstCombiner::removeFromWorkList(Instruction *I) {
2360 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2364 bool InstCombiner::runOnFunction(Function &F) {
2365 bool Changed = false;
2366 TD = &getAnalysis<TargetData>();
2368 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2370 while (!WorkList.empty()) {
2371 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2372 WorkList.pop_back();
2374 // Check to see if we can DCE or ConstantPropagate the instruction...
2375 // Check to see if we can DIE the instruction...
2376 if (isInstructionTriviallyDead(I)) {
2377 // Add operands to the worklist...
2378 if (I->getNumOperands() < 4)
2379 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2380 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2381 WorkList.push_back(Op);
2384 I->getParent()->getInstList().erase(I);
2385 removeFromWorkList(I);
2389 // Instruction isn't dead, see if we can constant propagate it...
2390 if (Constant *C = ConstantFoldInstruction(I)) {
2391 // Add operands to the worklist...
2392 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2393 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2394 WorkList.push_back(Op);
2395 ReplaceInstUsesWith(*I, C);
2398 I->getParent()->getInstList().erase(I);
2399 removeFromWorkList(I);
2403 // Now that we have an instruction, try combining it to simplify it...
2404 if (Instruction *Result = visit(*I)) {
2406 // Should we replace the old instruction with a new one?
2408 // Instructions can end up on the worklist more than once. Make sure
2409 // we do not process an instruction that has been deleted.
2410 removeFromWorkList(I);
2412 // Move the name to the new instruction first...
2413 std::string OldName = I->getName(); I->setName("");
2414 Result->setName(OldName);
2416 // Insert the new instruction into the basic block...
2417 BasicBlock *InstParent = I->getParent();
2418 InstParent->getInstList().insert(I, Result);
2420 // Everything uses the new instruction now...
2421 I->replaceAllUsesWith(Result);
2423 // Erase the old instruction.
2424 InstParent->getInstList().erase(I);
2426 BasicBlock::iterator II = I;
2428 // If the instruction was modified, it's possible that it is now dead.
2429 // if so, remove it.
2430 if (dceInstruction(II)) {
2431 // Instructions may end up in the worklist more than once. Erase them
2433 removeFromWorkList(I);
2439 WorkList.push_back(Result);
2440 AddUsesToWorkList(*Result);
2449 Pass *llvm::createInstructionCombiningPass() {
2450 return new InstCombiner();