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 (!I.getType()->isFloatingPoint() && // -0 + +0 = +0, so it's not a noop
445 RHS == Constant::getNullValue(I.getType()))
446 return ReplaceInstUsesWith(I, LHS);
449 if (I.getType()->isInteger())
450 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
453 if (Value *V = dyn_castNegVal(LHS))
454 return BinaryOperator::create(Instruction::Sub, RHS, V);
457 if (!isa<Constant>(RHS))
458 if (Value *V = dyn_castNegVal(RHS))
459 return BinaryOperator::create(Instruction::Sub, LHS, V);
461 // X*C + X --> X * (C+1)
462 if (dyn_castFoldableMul(LHS) == RHS) {
464 ConstantExpr::get(Instruction::Add,
465 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
466 ConstantInt::get(I.getType(), 1));
467 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
470 // X + X*C --> X * (C+1)
471 if (dyn_castFoldableMul(RHS) == LHS) {
473 ConstantExpr::get(Instruction::Add,
474 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
475 ConstantInt::get(I.getType(), 1));
476 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
479 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
480 if (Constant *C2 = dyn_castMaskingAnd(RHS))
481 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
483 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
484 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
485 switch (ILHS->getOpcode()) {
486 case Instruction::Xor:
487 // ~X + C --> (C-1) - X
488 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
489 if (XorRHS->isAllOnesValue())
490 return BinaryOperator::create(Instruction::Sub,
491 ConstantExpr::get(Instruction::Sub,
492 CRHS, ConstantInt::get(I.getType(), 1)),
493 ILHS->getOperand(0));
500 return Changed ? &I : 0;
503 // isSignBit - Return true if the value represented by the constant only has the
504 // highest order bit set.
505 static bool isSignBit(ConstantInt *CI) {
506 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
507 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
510 static unsigned getTypeSizeInBits(const Type *Ty) {
511 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
514 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
515 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
517 if (Op0 == Op1) // sub X, X -> 0
518 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
520 // If this is a 'B = x-(-A)', change to B = x+A...
521 if (Value *V = dyn_castNegVal(Op1))
522 return BinaryOperator::create(Instruction::Add, Op0, V);
524 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
525 // Replace (-1 - A) with (~A)...
526 if (C->isAllOnesValue())
527 return BinaryOperator::createNot(Op1);
529 // C - ~X == X + (1+C)
530 if (BinaryOperator::isNot(Op1))
531 return BinaryOperator::create(Instruction::Add,
532 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
533 ConstantExpr::get(Instruction::Add, C,
534 ConstantInt::get(I.getType(), 1)));
537 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
538 if (Op1I->hasOneUse()) {
539 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
540 // is not used by anyone else...
542 if (Op1I->getOpcode() == Instruction::Sub &&
543 !Op1I->getType()->isFloatingPoint()) {
544 // Swap the two operands of the subexpr...
545 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
546 Op1I->setOperand(0, IIOp1);
547 Op1I->setOperand(1, IIOp0);
549 // Create the new top level add instruction...
550 return BinaryOperator::create(Instruction::Add, Op0, Op1);
553 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
555 if (Op1I->getOpcode() == Instruction::And &&
556 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
557 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
559 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
560 return BinaryOperator::create(Instruction::And, Op0, NewNot);
563 // X - X*C --> X * (1-C)
564 if (dyn_castFoldableMul(Op1I) == Op0) {
566 ConstantExpr::get(Instruction::Sub,
567 ConstantInt::get(I.getType(), 1),
568 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
569 assert(CP1 && "Couldn't constant fold 1-C?");
570 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
574 // X*C - X --> X * (C-1)
575 if (dyn_castFoldableMul(Op0) == Op1) {
577 ConstantExpr::get(Instruction::Sub,
578 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
579 ConstantInt::get(I.getType(), 1));
580 assert(CP1 && "Couldn't constant fold C - 1?");
581 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
587 /// isSignBitCheck - Given an exploded setcc instruction, return true if it is
588 /// really just returns true if the most significant (sign) bit is set.
589 static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
590 if (RHS->getType()->isSigned()) {
591 // True if source is LHS < 0 or LHS <= -1
592 return Opcode == Instruction::SetLT && RHS->isNullValue() ||
593 Opcode == Instruction::SetLE && RHS->isAllOnesValue();
595 ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
596 // True if source is LHS > 127 or LHS >= 128, where the constants depend on
597 // the size of the integer type.
598 if (Opcode == Instruction::SetGE)
599 return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1);
600 if (Opcode == Instruction::SetGT)
601 return RHSC->getValue() ==
602 (1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
607 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
608 bool Changed = SimplifyCommutative(I);
609 Value *Op0 = I.getOperand(0);
611 // Simplify mul instructions with a constant RHS...
612 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
613 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
615 // ((X << C1)*C2) == (X * (C2 << C1))
616 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
617 if (SI->getOpcode() == Instruction::Shl)
618 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
619 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
620 ConstantExpr::get(Instruction::Shl, CI, ShOp));
622 if (CI->isNullValue())
623 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
624 if (CI->equalsInt(1)) // X * 1 == X
625 return ReplaceInstUsesWith(I, Op0);
626 if (CI->isAllOnesValue()) // X * -1 == 0 - X
627 return BinaryOperator::createNeg(Op0, I.getName());
629 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
630 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
631 return new ShiftInst(Instruction::Shl, Op0,
632 ConstantUInt::get(Type::UByteTy, C));
634 ConstantFP *Op1F = cast<ConstantFP>(Op1);
635 if (Op1F->isNullValue())
636 return ReplaceInstUsesWith(I, Op1);
638 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
639 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
640 if (Op1F->getValue() == 1.0)
641 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
645 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
646 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
647 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
649 // If one of the operands of the multiply is a cast from a boolean value, then
650 // we know the bool is either zero or one, so this is a 'masking' multiply.
651 // See if we can simplify things based on how the boolean was originally
653 CastInst *BoolCast = 0;
654 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
655 if (CI->getOperand(0)->getType() == Type::BoolTy)
658 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
659 if (CI->getOperand(0)->getType() == Type::BoolTy)
662 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
663 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
664 const Type *SCOpTy = SCIOp0->getType();
666 // If the setcc is true iff the sign bit of X is set, then convert this
667 // multiply into a shift/and combination.
668 if (isa<ConstantInt>(SCIOp1) &&
669 isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
670 // Shift the X value right to turn it into "all signbits".
671 Constant *Amt = ConstantUInt::get(Type::UByteTy,
672 SCOpTy->getPrimitiveSize()*8-1);
673 if (SCIOp0->getType()->isUnsigned()) {
674 const Type *NewTy = getSignedIntegralType(SCIOp0->getType());
675 SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
676 SCIOp0->getName()), I);
680 InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
681 BoolCast->getOperand(0)->getName()+
684 // If the multiply type is not the same as the source type, sign extend
685 // or truncate to the multiply type.
686 if (I.getType() != V->getType())
687 V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
689 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
690 return BinaryOperator::create(Instruction::And, V, OtherOp);
695 return Changed ? &I : 0;
698 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
700 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
701 if (RHS->equalsInt(1))
702 return ReplaceInstUsesWith(I, I.getOperand(0));
704 // Check to see if this is an unsigned division with an exact power of 2,
705 // if so, convert to a right shift.
706 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
707 if (uint64_t Val = C->getValue()) // Don't break X / 0
708 if (uint64_t C = Log2(Val))
709 return new ShiftInst(Instruction::Shr, I.getOperand(0),
710 ConstantUInt::get(Type::UByteTy, C));
713 // 0 / X == 0, we don't need to preserve faults!
714 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
715 if (LHS->equalsInt(0))
716 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
722 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
723 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
724 if (RHS->equalsInt(1)) // X % 1 == 0
725 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
727 // Check to see if this is an unsigned remainder with an exact power of 2,
728 // if so, convert to a bitwise and.
729 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
730 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
732 return BinaryOperator::create(Instruction::And, I.getOperand(0),
733 ConstantUInt::get(I.getType(), Val-1));
736 // 0 % X == 0, we don't need to preserve faults!
737 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
738 if (LHS->equalsInt(0))
739 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
744 // isMaxValueMinusOne - return true if this is Max-1
745 static bool isMaxValueMinusOne(const ConstantInt *C) {
746 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
747 // Calculate -1 casted to the right type...
748 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
749 uint64_t Val = ~0ULL; // All ones
750 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
751 return CU->getValue() == Val-1;
754 const ConstantSInt *CS = cast<ConstantSInt>(C);
756 // Calculate 0111111111..11111
757 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
758 int64_t Val = INT64_MAX; // All ones
759 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
760 return CS->getValue() == Val-1;
763 // isMinValuePlusOne - return true if this is Min+1
764 static bool isMinValuePlusOne(const ConstantInt *C) {
765 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
766 return CU->getValue() == 1;
768 const ConstantSInt *CS = cast<ConstantSInt>(C);
770 // Calculate 1111111111000000000000
771 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
772 int64_t Val = -1; // All ones
773 Val <<= TypeBits-1; // Shift over to the right spot
774 return CS->getValue() == Val+1;
777 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
778 /// are carefully arranged to allow folding of expressions such as:
780 /// (A < B) | (A > B) --> (A != B)
782 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
783 /// represents that the comparison is true if A == B, and bit value '1' is true
786 static unsigned getSetCondCode(const SetCondInst *SCI) {
787 switch (SCI->getOpcode()) {
789 case Instruction::SetGT: return 1;
790 case Instruction::SetEQ: return 2;
791 case Instruction::SetGE: return 3;
792 case Instruction::SetLT: return 4;
793 case Instruction::SetNE: return 5;
794 case Instruction::SetLE: return 6;
797 assert(0 && "Invalid SetCC opcode!");
802 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
803 /// opcode and two operands into either a constant true or false, or a brand new
804 /// SetCC instruction.
805 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
807 case 0: return ConstantBool::False;
808 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
809 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
810 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
811 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
812 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
813 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
814 case 7: return ConstantBool::True;
815 default: assert(0 && "Illegal SetCCCode!"); return 0;
819 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
820 struct FoldSetCCLogical {
823 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
824 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
825 bool shouldApply(Value *V) const {
826 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
827 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
828 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
831 Instruction *apply(BinaryOperator &Log) const {
832 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
833 if (SCI->getOperand(0) != LHS) {
834 assert(SCI->getOperand(1) == LHS);
835 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
838 unsigned LHSCode = getSetCondCode(SCI);
839 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
841 switch (Log.getOpcode()) {
842 case Instruction::And: Code = LHSCode & RHSCode; break;
843 case Instruction::Or: Code = LHSCode | RHSCode; break;
844 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
845 default: assert(0 && "Illegal logical opcode!"); return 0;
848 Value *RV = getSetCCValue(Code, LHS, RHS);
849 if (Instruction *I = dyn_cast<Instruction>(RV))
851 // Otherwise, it's a constant boolean value...
852 return IC.ReplaceInstUsesWith(Log, RV);
857 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
858 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
859 // guaranteed to be either a shift instruction or a binary operator.
860 Instruction *InstCombiner::OptAndOp(Instruction *Op,
861 ConstantIntegral *OpRHS,
862 ConstantIntegral *AndRHS,
863 BinaryOperator &TheAnd) {
864 Value *X = Op->getOperand(0);
865 Constant *Together = 0;
866 if (!isa<ShiftInst>(Op))
867 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
869 switch (Op->getOpcode()) {
870 case Instruction::Xor:
871 if (Together->isNullValue()) {
872 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
873 return BinaryOperator::create(Instruction::And, X, AndRHS);
874 } else if (Op->hasOneUse()) {
875 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
876 std::string OpName = Op->getName(); Op->setName("");
877 Instruction *And = BinaryOperator::create(Instruction::And,
879 InsertNewInstBefore(And, TheAnd);
880 return BinaryOperator::create(Instruction::Xor, And, Together);
883 case Instruction::Or:
884 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
885 if (Together->isNullValue())
886 return BinaryOperator::create(Instruction::And, X, AndRHS);
888 if (Together == AndRHS) // (X | C) & C --> C
889 return ReplaceInstUsesWith(TheAnd, AndRHS);
891 if (Op->hasOneUse() && Together != OpRHS) {
892 // (X | C1) & C2 --> (X | (C1&C2)) & C2
893 std::string Op0Name = Op->getName(); Op->setName("");
894 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
896 InsertNewInstBefore(Or, TheAnd);
897 return BinaryOperator::create(Instruction::And, Or, AndRHS);
901 case Instruction::Add:
902 if (Op->hasOneUse()) {
903 // Adding a one to a single bit bit-field should be turned into an XOR
904 // of the bit. First thing to check is to see if this AND is with a
905 // single bit constant.
906 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
908 // Clear bits that are not part of the constant.
909 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
911 // If there is only one bit set...
912 if ((AndRHSV & (AndRHSV-1)) == 0) {
913 // Ok, at this point, we know that we are masking the result of the
914 // ADD down to exactly one bit. If the constant we are adding has
915 // no bits set below this bit, then we can eliminate the ADD.
916 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
918 // Check to see if any bits below the one bit set in AndRHSV are set.
919 if ((AddRHS & (AndRHSV-1)) == 0) {
920 // If not, the only thing that can effect the output of the AND is
921 // the bit specified by AndRHSV. If that bit is set, the effect of
922 // the XOR is to toggle the bit. If it is clear, then the ADD has
924 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
925 TheAnd.setOperand(0, X);
928 std::string Name = Op->getName(); Op->setName("");
929 // Pull the XOR out of the AND.
930 Instruction *NewAnd =
931 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
932 InsertNewInstBefore(NewAnd, TheAnd);
933 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
940 case Instruction::Shl: {
941 // We know that the AND will not produce any of the bits shifted in, so if
942 // the anded constant includes them, clear them now!
944 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
945 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
946 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
948 TheAnd.setOperand(1, CI);
953 case Instruction::Shr:
954 // We know that the AND will not produce any of the bits shifted in, so if
955 // the anded constant includes them, clear them now! This only applies to
956 // unsigned shifts, because a signed shr may bring in set bits!
958 if (AndRHS->getType()->isUnsigned()) {
959 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
960 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
961 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
963 TheAnd.setOperand(1, CI);
973 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
974 bool Changed = SimplifyCommutative(I);
975 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
977 // and X, X = X and X, 0 == 0
978 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
979 return ReplaceInstUsesWith(I, Op1);
982 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
983 if (RHS->isAllOnesValue())
984 return ReplaceInstUsesWith(I, Op0);
986 // Optimize a variety of ((val OP C1) & C2) combinations...
987 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
988 Instruction *Op0I = cast<Instruction>(Op0);
989 Value *X = Op0I->getOperand(0);
990 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
991 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
996 Value *Op0NotVal = dyn_castNotVal(Op0);
997 Value *Op1NotVal = dyn_castNotVal(Op1);
999 // (~A & ~B) == (~(A | B)) - Demorgan's Law
1000 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1001 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
1002 Op1NotVal,I.getName()+".demorgan");
1003 InsertNewInstBefore(Or, I);
1004 return BinaryOperator::createNot(Or);
1007 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1008 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1010 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1011 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1012 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1015 return Changed ? &I : 0;
1020 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1021 bool Changed = SimplifyCommutative(I);
1022 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1024 // or X, X = X or X, 0 == X
1025 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1026 return ReplaceInstUsesWith(I, Op0);
1029 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1030 if (RHS->isAllOnesValue())
1031 return ReplaceInstUsesWith(I, Op1);
1033 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1034 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1035 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
1036 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1037 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1038 Instruction *Or = BinaryOperator::create(Instruction::Or,
1039 Op0I->getOperand(0), RHS,
1041 InsertNewInstBefore(Or, I);
1042 return BinaryOperator::create(Instruction::And, Or,
1043 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
1046 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1047 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
1048 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1049 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1050 Instruction *Or = BinaryOperator::create(Instruction::Or,
1051 Op0I->getOperand(0), RHS,
1053 InsertNewInstBefore(Or, I);
1054 return BinaryOperator::create(Instruction::Xor, Or,
1055 ConstantExpr::get(Instruction::And, Op0CI,
1061 // (A & C1)|(A & C2) == A & (C1|C2)
1062 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
1063 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
1064 if (LHS->getOperand(0) == RHS->getOperand(0))
1065 if (Constant *C0 = dyn_castMaskingAnd(LHS))
1066 if (Constant *C1 = dyn_castMaskingAnd(RHS))
1067 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
1068 ConstantExpr::get(Instruction::Or, C0, C1));
1070 Value *Op0NotVal = dyn_castNotVal(Op0);
1071 Value *Op1NotVal = dyn_castNotVal(Op1);
1073 if (Op1 == Op0NotVal) // ~A | A == -1
1074 return ReplaceInstUsesWith(I,
1075 ConstantIntegral::getAllOnesValue(I.getType()));
1077 if (Op0 == Op1NotVal) // A | ~A == -1
1078 return ReplaceInstUsesWith(I,
1079 ConstantIntegral::getAllOnesValue(I.getType()));
1081 // (~A | ~B) == (~(A & B)) - Demorgan's Law
1082 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1083 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
1084 Op1NotVal,I.getName()+".demorgan",
1086 WorkList.push_back(And);
1087 return BinaryOperator::createNot(And);
1090 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1091 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1092 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1095 return Changed ? &I : 0;
1098 // XorSelf - Implements: X ^ X --> 0
1101 XorSelf(Value *rhs) : RHS(rhs) {}
1102 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1103 Instruction *apply(BinaryOperator &Xor) const {
1109 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1110 bool Changed = SimplifyCommutative(I);
1111 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1113 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1114 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1115 assert(Result == &I && "AssociativeOpt didn't work?");
1116 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1119 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1121 if (RHS->isNullValue())
1122 return ReplaceInstUsesWith(I, Op0);
1124 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1125 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1126 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1127 if (RHS == ConstantBool::True && SCI->hasOneUse())
1128 return new SetCondInst(SCI->getInverseCondition(),
1129 SCI->getOperand(0), SCI->getOperand(1));
1131 // ~(c-X) == X-c-1 == X+(-c-1)
1132 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1133 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1134 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1135 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1136 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1137 ConstantInt::get(I.getType(), 1));
1138 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1142 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1143 switch (Op0I->getOpcode()) {
1144 case Instruction::Add:
1145 // ~(X-c) --> (-c-1)-X
1146 if (RHS->isAllOnesValue()) {
1147 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1148 Constant::getNullValue(Op0CI->getType()), Op0CI);
1149 return BinaryOperator::create(Instruction::Sub,
1150 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1151 ConstantInt::get(I.getType(), 1)),
1152 Op0I->getOperand(0));
1155 case Instruction::And:
1156 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1157 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1158 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1160 case Instruction::Or:
1161 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1162 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1163 return BinaryOperator::create(Instruction::And, Op0,
1171 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1173 return ReplaceInstUsesWith(I,
1174 ConstantIntegral::getAllOnesValue(I.getType()));
1176 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1178 return ReplaceInstUsesWith(I,
1179 ConstantIntegral::getAllOnesValue(I.getType()));
1181 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1182 if (Op1I->getOpcode() == Instruction::Or) {
1183 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1184 cast<BinaryOperator>(Op1I)->swapOperands();
1186 std::swap(Op0, Op1);
1187 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1189 std::swap(Op0, Op1);
1191 } else if (Op1I->getOpcode() == Instruction::Xor) {
1192 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1193 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1194 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1195 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1198 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1199 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1200 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1201 cast<BinaryOperator>(Op0I)->swapOperands();
1202 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1203 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1204 WorkList.push_back(cast<Instruction>(NotB));
1205 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1208 } else if (Op0I->getOpcode() == Instruction::Xor) {
1209 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1210 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1211 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1212 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1215 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1216 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1217 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1218 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1219 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1221 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1222 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1223 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1226 return Changed ? &I : 0;
1229 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1230 static Constant *AddOne(ConstantInt *C) {
1231 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1232 ConstantInt::get(C->getType(), 1));
1233 assert(Result && "Constant folding integer addition failed!");
1236 static Constant *SubOne(ConstantInt *C) {
1237 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1238 ConstantInt::get(C->getType(), 1));
1239 assert(Result && "Constant folding integer addition failed!");
1243 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1244 // true when both operands are equal...
1246 static bool isTrueWhenEqual(Instruction &I) {
1247 return I.getOpcode() == Instruction::SetEQ ||
1248 I.getOpcode() == Instruction::SetGE ||
1249 I.getOpcode() == Instruction::SetLE;
1252 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1253 bool Changed = SimplifyCommutative(I);
1254 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1255 const Type *Ty = Op0->getType();
1259 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1261 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1262 if (isa<ConstantPointerNull>(Op1) &&
1263 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1264 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1267 // setcc's with boolean values can always be turned into bitwise operations
1268 if (Ty == Type::BoolTy) {
1269 // If this is <, >, or !=, we can change this into a simple xor instruction
1270 if (!isTrueWhenEqual(I))
1271 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1273 // Otherwise we need to make a temporary intermediate instruction and insert
1274 // it into the instruction stream. This is what we are after:
1276 // seteq bool %A, %B -> ~(A^B)
1277 // setle bool %A, %B -> ~A | B
1278 // setge bool %A, %B -> A | ~B
1280 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1281 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1283 InsertNewInstBefore(Xor, I);
1284 return BinaryOperator::createNot(Xor);
1287 // Handle the setXe cases...
1288 assert(I.getOpcode() == Instruction::SetGE ||
1289 I.getOpcode() == Instruction::SetLE);
1291 if (I.getOpcode() == Instruction::SetGE)
1292 std::swap(Op0, Op1); // Change setge -> setle
1294 // Now we just have the SetLE case.
1295 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1296 InsertNewInstBefore(Not, I);
1297 return BinaryOperator::create(Instruction::Or, Not, Op1);
1300 // Check to see if we are doing one of many comparisons against constant
1301 // integers at the end of their ranges...
1303 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1304 // Simplify seteq and setne instructions...
1305 if (I.getOpcode() == Instruction::SetEQ ||
1306 I.getOpcode() == Instruction::SetNE) {
1307 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1309 // If the first operand is (and|or|xor) with a constant, and the second
1310 // operand is a constant, simplify a bit.
1311 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1312 switch (BO->getOpcode()) {
1313 case Instruction::Add:
1314 if (CI->isNullValue()) {
1315 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1316 // efficiently invertible, or if the add has just this one use.
1317 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1318 if (Value *NegVal = dyn_castNegVal(BOp1))
1319 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1320 else if (Value *NegVal = dyn_castNegVal(BOp0))
1321 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1322 else if (BO->hasOneUse()) {
1323 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1325 InsertNewInstBefore(Neg, I);
1326 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1330 case Instruction::Xor:
1331 // For the xor case, we can xor two constants together, eliminating
1332 // the explicit xor.
1333 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1334 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1335 ConstantExpr::get(Instruction::Xor, CI, BOC));
1338 case Instruction::Sub:
1339 // Replace (([sub|xor] A, B) != 0) with (A != B)
1340 if (CI->isNullValue())
1341 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1345 case Instruction::Or:
1346 // If bits are being or'd in that are not present in the constant we
1347 // are comparing against, then the comparison could never succeed!
1348 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1349 Constant *NotCI = NotConstant(CI);
1350 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1351 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1355 case Instruction::And:
1356 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1357 // If bits are being compared against that are and'd out, then the
1358 // comparison can never succeed!
1359 if (!ConstantExpr::get(Instruction::And, CI,
1360 NotConstant(BOC))->isNullValue())
1361 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1363 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1364 // to be a signed value as appropriate.
1365 if (isSignBit(BOC)) {
1366 Value *X = BO->getOperand(0);
1367 // If 'X' is not signed, insert a cast now...
1368 if (!BOC->getType()->isSigned()) {
1369 const Type *DestTy = getSignedIntegralType(BOC->getType());
1370 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1371 InsertNewInstBefore(NewCI, I);
1374 return new SetCondInst(isSetNE ? Instruction::SetLT :
1375 Instruction::SetGE, X,
1376 Constant::getNullValue(X->getType()));
1382 } else { // Not a SetEQ/SetNE
1383 // If the LHS is a cast from an integral value of the same size,
1384 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
1385 Value *CastOp = Cast->getOperand(0);
1386 const Type *SrcTy = CastOp->getType();
1387 unsigned SrcTySize = SrcTy->getPrimitiveSize();
1388 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
1389 SrcTySize == Cast->getType()->getPrimitiveSize()) {
1390 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
1391 "Source and destination signednesses should differ!");
1392 if (Cast->getType()->isSigned()) {
1393 // If this is a signed comparison, check for comparisons in the
1394 // vicinity of zero.
1395 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
1397 return BinaryOperator::create(Instruction::SetGT, CastOp,
1398 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
1399 else if (I.getOpcode() == Instruction::SetGT &&
1400 cast<ConstantSInt>(CI)->getValue() == -1)
1401 // X > -1 => x < 128
1402 return BinaryOperator::create(Instruction::SetLT, CastOp,
1403 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
1405 ConstantUInt *CUI = cast<ConstantUInt>(CI);
1406 if (I.getOpcode() == Instruction::SetLT &&
1407 CUI->getValue() == 1ULL << (SrcTySize*8-1))
1408 // X < 128 => X > -1
1409 return BinaryOperator::create(Instruction::SetGT, CastOp,
1410 ConstantSInt::get(SrcTy, -1));
1411 else if (I.getOpcode() == Instruction::SetGT &&
1412 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
1414 return BinaryOperator::create(Instruction::SetLT, CastOp,
1415 Constant::getNullValue(SrcTy));
1421 // Check to see if we are comparing against the minimum or maximum value...
1422 if (CI->isMinValue()) {
1423 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1424 return ReplaceInstUsesWith(I, ConstantBool::False);
1425 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1426 return ReplaceInstUsesWith(I, ConstantBool::True);
1427 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1428 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1429 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1430 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1432 } else if (CI->isMaxValue()) {
1433 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1434 return ReplaceInstUsesWith(I, ConstantBool::False);
1435 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1436 return ReplaceInstUsesWith(I, ConstantBool::True);
1437 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1438 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1439 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1440 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1442 // Comparing against a value really close to min or max?
1443 } else if (isMinValuePlusOne(CI)) {
1444 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1445 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1446 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1447 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1449 } else if (isMaxValueMinusOne(CI)) {
1450 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1451 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1452 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1453 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1456 // If we still have a setle or setge instruction, turn it into the
1457 // appropriate setlt or setgt instruction. Since the border cases have
1458 // already been handled above, this requires little checking.
1460 if (I.getOpcode() == Instruction::SetLE)
1461 return BinaryOperator::create(Instruction::SetLT, Op0, AddOne(CI));
1462 if (I.getOpcode() == Instruction::SetGE)
1463 return BinaryOperator::create(Instruction::SetGT, Op0, SubOne(CI));
1466 // Test to see if the operands of the setcc are casted versions of other
1467 // values. If the cast can be stripped off both arguments, we do so now.
1468 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1469 Value *CastOp0 = CI->getOperand(0);
1470 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1471 !isa<Argument>(Op1) &&
1472 (I.getOpcode() == Instruction::SetEQ ||
1473 I.getOpcode() == Instruction::SetNE)) {
1474 // We keep moving the cast from the left operand over to the right
1475 // operand, where it can often be eliminated completely.
1478 // If operand #1 is a cast instruction, see if we can eliminate it as
1480 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1481 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1483 Op1 = CI2->getOperand(0);
1485 // If Op1 is a constant, we can fold the cast into the constant.
1486 if (Op1->getType() != Op0->getType())
1487 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1488 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1490 // Otherwise, cast the RHS right before the setcc
1491 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1492 InsertNewInstBefore(cast<Instruction>(Op1), I);
1494 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1497 // Handle the special case of: setcc (cast bool to X), <cst>
1498 // This comes up when you have code like
1501 // For generality, we handle any zero-extension of any operand comparison
1503 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1504 const Type *SrcTy = CastOp0->getType();
1505 const Type *DestTy = Op0->getType();
1506 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1507 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1508 // Ok, we have an expansion of operand 0 into a new type. Get the
1509 // constant value, masink off bits which are not set in the RHS. These
1510 // could be set if the destination value is signed.
1511 uint64_t ConstVal = ConstantRHS->getRawValue();
1512 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1514 // If the constant we are comparing it with has high bits set, which
1515 // don't exist in the original value, the values could never be equal,
1516 // because the source would be zero extended.
1518 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1519 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1520 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1521 switch (I.getOpcode()) {
1522 default: assert(0 && "Unknown comparison type!");
1523 case Instruction::SetEQ:
1524 return ReplaceInstUsesWith(I, ConstantBool::False);
1525 case Instruction::SetNE:
1526 return ReplaceInstUsesWith(I, ConstantBool::True);
1527 case Instruction::SetLT:
1528 case Instruction::SetLE:
1529 if (DestTy->isSigned() && HasSignBit)
1530 return ReplaceInstUsesWith(I, ConstantBool::False);
1531 return ReplaceInstUsesWith(I, ConstantBool::True);
1532 case Instruction::SetGT:
1533 case Instruction::SetGE:
1534 if (DestTy->isSigned() && HasSignBit)
1535 return ReplaceInstUsesWith(I, ConstantBool::True);
1536 return ReplaceInstUsesWith(I, ConstantBool::False);
1540 // Otherwise, we can replace the setcc with a setcc of the smaller
1542 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1543 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1547 return Changed ? &I : 0;
1552 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1553 assert(I.getOperand(1)->getType() == Type::UByteTy);
1554 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1555 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1557 // shl X, 0 == X and shr X, 0 == X
1558 // shl 0, X == 0 and shr 0, X == 0
1559 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1560 Op0 == Constant::getNullValue(Op0->getType()))
1561 return ReplaceInstUsesWith(I, Op0);
1563 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1565 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1566 if (CSI->isAllOnesValue())
1567 return ReplaceInstUsesWith(I, CSI);
1569 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1570 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1571 // of a signed value.
1573 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1574 if (CUI->getValue() >= TypeBits) {
1575 if (!Op0->getType()->isSigned() || isLeftShift)
1576 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1578 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
1583 // ((X*C1) << C2) == (X * (C1 << C2))
1584 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1585 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1586 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1587 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1588 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1591 // If the operand is an bitwise operator with a constant RHS, and the
1592 // shift is the only use, we can pull it out of the shift.
1593 if (Op0->hasOneUse())
1594 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1595 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1596 bool isValid = true; // Valid only for And, Or, Xor
1597 bool highBitSet = false; // Transform if high bit of constant set?
1599 switch (Op0BO->getOpcode()) {
1600 default: isValid = false; break; // Do not perform transform!
1601 case Instruction::Or:
1602 case Instruction::Xor:
1605 case Instruction::And:
1610 // If this is a signed shift right, and the high bit is modified
1611 // by the logical operation, do not perform the transformation.
1612 // The highBitSet boolean indicates the value of the high bit of
1613 // the constant which would cause it to be modified for this
1616 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1617 uint64_t Val = Op0C->getRawValue();
1618 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1622 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1624 Instruction *NewShift =
1625 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1628 InsertNewInstBefore(NewShift, I);
1630 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1635 // If this is a shift of a shift, see if we can fold the two together...
1636 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1637 if (ConstantUInt *ShiftAmt1C =
1638 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1639 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1640 unsigned ShiftAmt2 = CUI->getValue();
1642 // Check for (A << c1) << c2 and (A >> c1) >> c2
1643 if (I.getOpcode() == Op0SI->getOpcode()) {
1644 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1645 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
1646 Amt = Op0->getType()->getPrimitiveSize()*8;
1647 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1648 ConstantUInt::get(Type::UByteTy, Amt));
1651 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1652 // signed types, we can only support the (A >> c1) << c2 configuration,
1653 // because it can not turn an arbitrary bit of A into a sign bit.
1654 if (I.getType()->isUnsigned() || isLeftShift) {
1655 // Calculate bitmask for what gets shifted off the edge...
1656 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1658 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1660 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1663 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1664 C, Op0SI->getOperand(0)->getName()+".mask");
1665 InsertNewInstBefore(Mask, I);
1667 // Figure out what flavor of shift we should use...
1668 if (ShiftAmt1 == ShiftAmt2)
1669 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1670 else if (ShiftAmt1 < ShiftAmt2) {
1671 return new ShiftInst(I.getOpcode(), Mask,
1672 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1674 return new ShiftInst(Op0SI->getOpcode(), Mask,
1675 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1685 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1688 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1689 const Type *DstTy) {
1691 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1692 // are identical and the bits don't get reinterpreted (for example
1693 // int->float->int would not be allowed)
1694 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1697 // Allow free casting and conversion of sizes as long as the sign doesn't
1699 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1700 unsigned SrcSize = SrcTy->getPrimitiveSize();
1701 unsigned MidSize = MidTy->getPrimitiveSize();
1702 unsigned DstSize = DstTy->getPrimitiveSize();
1704 // Cases where we are monotonically decreasing the size of the type are
1705 // always ok, regardless of what sign changes are going on.
1707 if (SrcSize >= MidSize && MidSize >= DstSize)
1710 // Cases where the source and destination type are the same, but the middle
1711 // type is bigger are noops.
1713 if (SrcSize == DstSize && MidSize > SrcSize)
1716 // If we are monotonically growing, things are more complex.
1718 if (SrcSize <= MidSize && MidSize <= DstSize) {
1719 // We have eight combinations of signedness to worry about. Here's the
1721 static const int SignTable[8] = {
1722 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1723 1, // U U U Always ok
1724 1, // U U S Always ok
1725 3, // U S U Ok iff SrcSize != MidSize
1726 3, // U S S Ok iff SrcSize != MidSize
1727 0, // S U U Never ok
1728 2, // S U S Ok iff MidSize == DstSize
1729 1, // S S U Always ok
1730 1, // S S S Always ok
1733 // Choose an action based on the current entry of the signtable that this
1734 // cast of cast refers to...
1735 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1736 switch (SignTable[Row]) {
1737 case 0: return false; // Never ok
1738 case 1: return true; // Always ok
1739 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1740 case 3: // Ok iff SrcSize != MidSize
1741 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1742 default: assert(0 && "Bad entry in sign table!");
1747 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1748 // like: short -> ushort -> uint, because this can create wrong results if
1749 // the input short is negative!
1754 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1755 if (V->getType() == Ty || isa<Constant>(V)) return false;
1756 if (const CastInst *CI = dyn_cast<CastInst>(V))
1757 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1762 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1763 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1764 /// casts that are known to not do anything...
1766 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1767 Instruction *InsertBefore) {
1768 if (V->getType() == DestTy) return V;
1769 if (Constant *C = dyn_cast<Constant>(V))
1770 return ConstantExpr::getCast(C, DestTy);
1772 CastInst *CI = new CastInst(V, DestTy, V->getName());
1773 InsertNewInstBefore(CI, *InsertBefore);
1777 // CastInst simplification
1779 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1780 Value *Src = CI.getOperand(0);
1782 // If the user is casting a value to the same type, eliminate this cast
1784 if (CI.getType() == Src->getType())
1785 return ReplaceInstUsesWith(CI, Src);
1787 // If casting the result of another cast instruction, try to eliminate this
1790 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1791 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1792 CSrc->getType(), CI.getType())) {
1793 // This instruction now refers directly to the cast's src operand. This
1794 // has a good chance of making CSrc dead.
1795 CI.setOperand(0, CSrc->getOperand(0));
1799 // If this is an A->B->A cast, and we are dealing with integral types, try
1800 // to convert this into a logical 'and' instruction.
1802 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1803 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1804 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1805 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1806 assert(CSrc->getType() != Type::ULongTy &&
1807 "Cannot have type bigger than ulong!");
1808 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1809 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1810 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1815 // If casting the result of a getelementptr instruction with no offset, turn
1816 // this into a cast of the original pointer!
1818 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1819 bool AllZeroOperands = true;
1820 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1821 if (!isa<Constant>(GEP->getOperand(i)) ||
1822 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1823 AllZeroOperands = false;
1826 if (AllZeroOperands) {
1827 CI.setOperand(0, GEP->getOperand(0));
1832 // If we are casting a malloc or alloca to a pointer to a type of the same
1833 // size, rewrite the allocation instruction to allocate the "right" type.
1835 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1836 if (AI->hasOneUse() && !AI->isArrayAllocation())
1837 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1838 // Get the type really allocated and the type casted to...
1839 const Type *AllocElTy = AI->getAllocatedType();
1840 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1841 const Type *CastElTy = PTy->getElementType();
1842 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1844 // If the allocation is for an even multiple of the cast type size
1845 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1846 Value *Amt = ConstantUInt::get(Type::UIntTy,
1847 AllocElTySize/CastElTySize);
1848 std::string Name = AI->getName(); AI->setName("");
1849 AllocationInst *New;
1850 if (isa<MallocInst>(AI))
1851 New = new MallocInst(CastElTy, Amt, Name);
1853 New = new AllocaInst(CastElTy, Amt, Name);
1854 InsertNewInstBefore(New, CI);
1855 return ReplaceInstUsesWith(CI, New);
1859 // If the source value is an instruction with only this use, we can attempt to
1860 // propagate the cast into the instruction. Also, only handle integral types
1862 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1863 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1864 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1865 const Type *DestTy = CI.getType();
1866 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1867 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1869 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1870 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1872 switch (SrcI->getOpcode()) {
1873 case Instruction::Add:
1874 case Instruction::Mul:
1875 case Instruction::And:
1876 case Instruction::Or:
1877 case Instruction::Xor:
1878 // If we are discarding information, or just changing the sign, rewrite.
1879 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1880 // Don't insert two casts if they cannot be eliminated. We allow two
1881 // casts to be inserted if the sizes are the same. This could only be
1882 // converting signedness, which is a noop.
1883 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1884 !ValueRequiresCast(Op0, DestTy)) {
1885 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1886 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1887 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1888 ->getOpcode(), Op0c, Op1c);
1892 case Instruction::Shl:
1893 // Allow changing the sign of the source operand. Do not allow changing
1894 // the size of the shift, UNLESS the shift amount is a constant. We
1895 // mush not change variable sized shifts to a smaller size, because it
1896 // is undefined to shift more bits out than exist in the value.
1897 if (DestBitSize == SrcBitSize ||
1898 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1899 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1900 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1909 // CallInst simplification
1911 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1912 return visitCallSite(&CI);
1915 // InvokeInst simplification
1917 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1918 return visitCallSite(&II);
1921 // visitCallSite - Improvements for call and invoke instructions.
1923 Instruction *InstCombiner::visitCallSite(CallSite CS) {
1924 bool Changed = false;
1926 // If the callee is a constexpr cast of a function, attempt to move the cast
1927 // to the arguments of the call/invoke.
1928 if (transformConstExprCastCall(CS)) return 0;
1930 Value *Callee = CS.getCalledValue();
1931 const PointerType *PTy = cast<PointerType>(Callee->getType());
1932 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1933 if (FTy->isVarArg()) {
1934 // See if we can optimize any arguments passed through the varargs area of
1936 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
1937 E = CS.arg_end(); I != E; ++I)
1938 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
1939 // If this cast does not effect the value passed through the varargs
1940 // area, we can eliminate the use of the cast.
1941 Value *Op = CI->getOperand(0);
1942 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
1949 return Changed ? CS.getInstruction() : 0;
1952 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1953 // attempt to move the cast to the arguments of the call/invoke.
1955 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1956 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1957 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1958 if (CE->getOpcode() != Instruction::Cast ||
1959 !isa<ConstantPointerRef>(CE->getOperand(0)))
1961 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1962 if (!isa<Function>(CPR->getValue())) return false;
1963 Function *Callee = cast<Function>(CPR->getValue());
1964 Instruction *Caller = CS.getInstruction();
1966 // Okay, this is a cast from a function to a different type. Unless doing so
1967 // would cause a type conversion of one of our arguments, change this call to
1968 // be a direct call with arguments casted to the appropriate types.
1970 const FunctionType *FT = Callee->getFunctionType();
1971 const Type *OldRetTy = Caller->getType();
1973 // Check to see if we are changing the return type...
1974 if (OldRetTy != FT->getReturnType()) {
1975 if (Callee->isExternal() &&
1976 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
1977 !Caller->use_empty())
1978 return false; // Cannot transform this return value...
1980 // If the callsite is an invoke instruction, and the return value is used by
1981 // a PHI node in a successor, we cannot change the return type of the call
1982 // because there is no place to put the cast instruction (without breaking
1983 // the critical edge). Bail out in this case.
1984 if (!Caller->use_empty())
1985 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
1986 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
1988 if (PHINode *PN = dyn_cast<PHINode>(*UI))
1989 if (PN->getParent() == II->getNormalDest() ||
1990 PN->getParent() == II->getUnwindDest())
1994 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1995 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1997 CallSite::arg_iterator AI = CS.arg_begin();
1998 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1999 const Type *ParamTy = FT->getParamType(i);
2000 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
2001 if (Callee->isExternal() && !isConvertible) return false;
2004 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
2005 Callee->isExternal())
2006 return false; // Do not delete arguments unless we have a function body...
2008 // Okay, we decided that this is a safe thing to do: go ahead and start
2009 // inserting cast instructions as necessary...
2010 std::vector<Value*> Args;
2011 Args.reserve(NumActualArgs);
2013 AI = CS.arg_begin();
2014 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
2015 const Type *ParamTy = FT->getParamType(i);
2016 if ((*AI)->getType() == ParamTy) {
2017 Args.push_back(*AI);
2019 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
2020 InsertNewInstBefore(Cast, *Caller);
2021 Args.push_back(Cast);
2025 // If the function takes more arguments than the call was taking, add them
2027 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
2028 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
2030 // If we are removing arguments to the function, emit an obnoxious warning...
2031 if (FT->getNumParams() < NumActualArgs)
2032 if (!FT->isVarArg()) {
2033 std::cerr << "WARNING: While resolving call to function '"
2034 << Callee->getName() << "' arguments were dropped!\n";
2036 // Add all of the arguments in their promoted form to the arg list...
2037 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
2038 const Type *PTy = getPromotedType((*AI)->getType());
2039 if (PTy != (*AI)->getType()) {
2040 // Must promote to pass through va_arg area!
2041 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
2042 InsertNewInstBefore(Cast, *Caller);
2043 Args.push_back(Cast);
2045 Args.push_back(*AI);
2050 if (FT->getReturnType() == Type::VoidTy)
2051 Caller->setName(""); // Void type should not have a name...
2054 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2055 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
2056 Args, Caller->getName(), Caller);
2058 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
2061 // Insert a cast of the return type as necessary...
2063 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
2064 if (NV->getType() != Type::VoidTy) {
2065 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
2067 // If this is an invoke instruction, we should insert it after the first
2068 // non-phi, instruction in the normal successor block.
2069 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2070 BasicBlock::iterator I = II->getNormalDest()->begin();
2071 while (isa<PHINode>(I)) ++I;
2072 InsertNewInstBefore(NC, *I);
2074 // Otherwise, it's a call, just insert cast right after the call instr
2075 InsertNewInstBefore(NC, *Caller);
2077 AddUsesToWorkList(*Caller);
2079 NV = Constant::getNullValue(Caller->getType());
2083 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
2084 Caller->replaceAllUsesWith(NV);
2085 Caller->getParent()->getInstList().erase(Caller);
2086 removeFromWorkList(Caller);
2092 // PHINode simplification
2094 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2095 if (Value *V = hasConstantValue(&PN))
2096 return ReplaceInstUsesWith(PN, V);
2098 // If the only user of this instruction is a cast instruction, and all of the
2099 // incoming values are constants, change this PHI to merge together the casted
2102 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2103 if (CI->getType() != PN.getType()) { // noop casts will be folded
2104 bool AllConstant = true;
2105 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2106 if (!isa<Constant>(PN.getIncomingValue(i))) {
2107 AllConstant = false;
2111 // Make a new PHI with all casted values.
2112 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2113 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2114 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2115 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2116 PN.getIncomingBlock(i));
2119 // Update the cast instruction.
2120 CI->setOperand(0, New);
2121 WorkList.push_back(CI); // revisit the cast instruction to fold.
2122 WorkList.push_back(New); // Make sure to revisit the new Phi
2123 return &PN; // PN is now dead!
2130 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2131 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2132 // If so, eliminate the noop.
2133 if (GEP.getNumOperands() == 1)
2134 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2136 bool HasZeroPointerIndex = false;
2137 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2138 HasZeroPointerIndex = C->isNullValue();
2140 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2141 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2143 // Combine Indices - If the source pointer to this getelementptr instruction
2144 // is a getelementptr instruction, combine the indices of the two
2145 // getelementptr instructions into a single instruction.
2147 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
2148 std::vector<Value *> Indices;
2150 // Can we combine the two pointer arithmetics offsets?
2151 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
2152 isa<Constant>(GEP.getOperand(1))) {
2153 // Replace: gep (gep %P, long C1), long C2, ...
2154 // With: gep %P, long (C1+C2), ...
2155 Value *Sum = ConstantExpr::get(Instruction::Add,
2156 cast<Constant>(Src->getOperand(1)),
2157 cast<Constant>(GEP.getOperand(1)));
2158 assert(Sum && "Constant folding of longs failed!?");
2159 GEP.setOperand(0, Src->getOperand(0));
2160 GEP.setOperand(1, Sum);
2161 AddUsesToWorkList(*Src); // Reduce use count of Src
2163 } else if (Src->getNumOperands() == 2) {
2164 // Replace: gep (gep %P, long B), long A, ...
2165 // With: T = long A+B; gep %P, T, ...
2167 // Note that if our source is a gep chain itself that we wait for that
2168 // chain to be resolved before we perform this transformation. This
2169 // avoids us creating a TON of code in some cases.
2171 if (isa<GetElementPtrInst>(Src->getOperand(0)) &&
2172 cast<Instruction>(Src->getOperand(0))->getNumOperands() == 2)
2173 return 0; // Wait until our source is folded to completion.
2175 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
2177 Src->getName()+".sum", &GEP);
2178 GEP.setOperand(0, Src->getOperand(0));
2179 GEP.setOperand(1, Sum);
2180 WorkList.push_back(cast<Instruction>(Sum));
2182 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
2183 Src->getNumOperands() != 1) {
2184 // Otherwise we can do the fold if the first index of the GEP is a zero
2185 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
2186 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2187 } else if (Src->getOperand(Src->getNumOperands()-1) ==
2188 Constant::getNullValue(Type::LongTy)) {
2189 // If the src gep ends with a constant array index, merge this get into
2190 // it, even if we have a non-zero array index.
2191 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
2192 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
2195 if (!Indices.empty())
2196 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
2198 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
2199 // GEP of global variable. If all of the indices for this GEP are
2200 // constants, we can promote this to a constexpr instead of an instruction.
2202 // Scan for nonconstants...
2203 std::vector<Constant*> Indices;
2204 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2205 for (; I != E && isa<Constant>(*I); ++I)
2206 Indices.push_back(cast<Constant>(*I));
2208 if (I == E) { // If they are all constants...
2210 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2212 // Replace all uses of the GEP with the new constexpr...
2213 return ReplaceInstUsesWith(GEP, CE);
2215 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2216 if (CE->getOpcode() == Instruction::Cast) {
2217 if (HasZeroPointerIndex) {
2218 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2219 // into : GEP [10 x ubyte]* X, long 0, ...
2221 // This occurs when the program declares an array extern like "int X[];"
2223 Constant *X = CE->getOperand(0);
2224 const PointerType *CPTy = cast<PointerType>(CE->getType());
2225 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2226 if (const ArrayType *XATy =
2227 dyn_cast<ArrayType>(XTy->getElementType()))
2228 if (const ArrayType *CATy =
2229 dyn_cast<ArrayType>(CPTy->getElementType()))
2230 if (CATy->getElementType() == XATy->getElementType()) {
2231 // At this point, we know that the cast source type is a pointer
2232 // to an array of the same type as the destination pointer
2233 // array. Because the array type is never stepped over (there
2234 // is a leading zero) we can fold the cast into this GEP.
2235 GEP.setOperand(0, X);
2245 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2246 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2247 if (AI.isArrayAllocation()) // Check C != 1
2248 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2249 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2250 AllocationInst *New = 0;
2252 // Create and insert the replacement instruction...
2253 if (isa<MallocInst>(AI))
2254 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
2256 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2257 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
2260 // Scan to the end of the allocation instructions, to skip over a block of
2261 // allocas if possible...
2263 BasicBlock::iterator It = New;
2264 while (isa<AllocationInst>(*It)) ++It;
2266 // Now that I is pointing to the first non-allocation-inst in the block,
2267 // insert our getelementptr instruction...
2269 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
2270 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2272 // Now make everything use the getelementptr instead of the original
2274 ReplaceInstUsesWith(AI, V);
2280 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2281 Value *Op = FI.getOperand(0);
2283 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2284 if (CastInst *CI = dyn_cast<CastInst>(Op))
2285 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2286 FI.setOperand(0, CI->getOperand(0));
2294 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2295 /// constantexpr, return the constant value being addressed by the constant
2296 /// expression, or null if something is funny.
2298 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2299 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
2300 return 0; // Do not allow stepping over the value!
2302 // Loop over all of the operands, tracking down which value we are
2304 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2305 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2306 ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
2307 if (CS == 0) return 0;
2308 if (CU->getValue() >= CS->getValues().size()) return 0;
2309 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2310 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2311 ConstantArray *CA = dyn_cast<ConstantArray>(C);
2312 if (CA == 0) return 0;
2313 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2314 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2320 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2321 Value *Op = LI.getOperand(0);
2322 if (LI.isVolatile()) return 0;
2324 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2325 Op = CPR->getValue();
2327 // Instcombine load (constant global) into the value loaded...
2328 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2329 if (GV->isConstant() && !GV->isExternal())
2330 return ReplaceInstUsesWith(LI, GV->getInitializer());
2332 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2333 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2334 if (CE->getOpcode() == Instruction::GetElementPtr)
2335 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2336 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2337 if (GV->isConstant() && !GV->isExternal())
2338 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2339 return ReplaceInstUsesWith(LI, V);
2344 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2345 // Change br (not X), label True, label False to: br X, label False, True
2346 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
2347 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2348 BasicBlock *TrueDest = BI.getSuccessor(0);
2349 BasicBlock *FalseDest = BI.getSuccessor(1);
2350 // Swap Destinations and condition...
2352 BI.setSuccessor(0, FalseDest);
2353 BI.setSuccessor(1, TrueDest);
2360 void InstCombiner::removeFromWorkList(Instruction *I) {
2361 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2365 bool InstCombiner::runOnFunction(Function &F) {
2366 bool Changed = false;
2367 TD = &getAnalysis<TargetData>();
2369 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2371 while (!WorkList.empty()) {
2372 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2373 WorkList.pop_back();
2375 // Check to see if we can DCE or ConstantPropagate the instruction...
2376 // Check to see if we can DIE the instruction...
2377 if (isInstructionTriviallyDead(I)) {
2378 // Add operands to the worklist...
2379 if (I->getNumOperands() < 4)
2380 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2381 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2382 WorkList.push_back(Op);
2385 I->getParent()->getInstList().erase(I);
2386 removeFromWorkList(I);
2390 // Instruction isn't dead, see if we can constant propagate it...
2391 if (Constant *C = ConstantFoldInstruction(I)) {
2392 // Add operands to the worklist...
2393 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2394 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2395 WorkList.push_back(Op);
2396 ReplaceInstUsesWith(*I, C);
2399 I->getParent()->getInstList().erase(I);
2400 removeFromWorkList(I);
2404 // Now that we have an instruction, try combining it to simplify it...
2405 if (Instruction *Result = visit(*I)) {
2407 // Should we replace the old instruction with a new one?
2409 // Instructions can end up on the worklist more than once. Make sure
2410 // we do not process an instruction that has been deleted.
2411 removeFromWorkList(I);
2413 // Move the name to the new instruction first...
2414 std::string OldName = I->getName(); I->setName("");
2415 Result->setName(OldName);
2417 // Insert the new instruction into the basic block...
2418 BasicBlock *InstParent = I->getParent();
2419 InstParent->getInstList().insert(I, Result);
2421 // Everything uses the new instruction now...
2422 I->replaceAllUsesWith(Result);
2424 // Erase the old instruction.
2425 InstParent->getInstList().erase(I);
2427 BasicBlock::iterator II = I;
2429 // If the instruction was modified, it's possible that it is now dead.
2430 // if so, remove it.
2431 if (dceInstruction(II)) {
2432 // Instructions may end up in the worklist more than once. Erase them
2434 removeFromWorkList(I);
2440 WorkList.push_back(Result);
2441 AddUsesToWorkList(*Result);
2450 Pass *llvm::createInstructionCombiningPass() {
2451 return new InstCombiner();