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/ConstantHandling.h"
41 #include "llvm/DerivedTypes.h"
42 #include "llvm/GlobalVariable.h"
43 #include "llvm/Target/TargetData.h"
44 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
45 #include "llvm/Transforms/Utils/Local.h"
46 #include "llvm/Support/InstIterator.h"
47 #include "llvm/Support/InstVisitor.h"
48 #include "llvm/Support/CallSite.h"
49 #include "Support/Statistic.h"
54 Statistic<> NumCombined ("instcombine", "Number of insts combined");
55 Statistic<> NumConstProp("instcombine", "Number of constant folds");
56 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
58 class InstCombiner : public FunctionPass,
59 public InstVisitor<InstCombiner, Instruction*> {
60 // Worklist of all of the instructions that need to be simplified.
61 std::vector<Instruction*> WorkList;
64 void AddUsesToWorkList(Instruction &I) {
65 // The instruction was simplified, add all users of the instruction to
66 // the work lists because they might get more simplified now...
68 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
70 WorkList.push_back(cast<Instruction>(*UI));
73 // removeFromWorkList - remove all instances of I from the worklist.
74 void removeFromWorkList(Instruction *I);
76 virtual bool runOnFunction(Function &F);
78 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
79 AU.addRequired<TargetData>();
83 // Visitation implementation - Implement instruction combining for different
84 // instruction types. The semantics are as follows:
86 // null - No change was made
87 // I - Change was made, I is still valid, I may be dead though
88 // otherwise - Change was made, replace I with returned instruction
90 Instruction *visitAdd(BinaryOperator &I);
91 Instruction *visitSub(BinaryOperator &I);
92 Instruction *visitMul(BinaryOperator &I);
93 Instruction *visitDiv(BinaryOperator &I);
94 Instruction *visitRem(BinaryOperator &I);
95 Instruction *visitAnd(BinaryOperator &I);
96 Instruction *visitOr (BinaryOperator &I);
97 Instruction *visitXor(BinaryOperator &I);
98 Instruction *visitSetCondInst(BinaryOperator &I);
99 Instruction *visitShiftInst(ShiftInst &I);
100 Instruction *visitCastInst(CastInst &CI);
101 Instruction *visitCallInst(CallInst &CI);
102 Instruction *visitInvokeInst(InvokeInst &II);
103 Instruction *visitPHINode(PHINode &PN);
104 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
105 Instruction *visitAllocationInst(AllocationInst &AI);
106 Instruction *visitFreeInst(FreeInst &FI);
107 Instruction *visitLoadInst(LoadInst &LI);
108 Instruction *visitBranchInst(BranchInst &BI);
110 // visitInstruction - Specify what to return for unhandled instructions...
111 Instruction *visitInstruction(Instruction &I) { return 0; }
114 Instruction *visitCallSite(CallSite CS);
115 bool transformConstExprCastCall(CallSite CS);
117 // InsertNewInstBefore - insert an instruction New before instruction Old
118 // in the program. Add the new instruction to the worklist.
120 void InsertNewInstBefore(Instruction *New, Instruction &Old) {
121 assert(New && New->getParent() == 0 &&
122 "New instruction already inserted into a basic block!");
123 BasicBlock *BB = Old.getParent();
124 BB->getInstList().insert(&Old, New); // Insert inst
125 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 // SimplifyCommutative - This performs a few simplifications for commutative
180 // 1. Order operands such that they are listed from right (least complex) to
181 // left (most complex). This puts constants before unary operators before
184 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
185 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
187 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
188 bool Changed = false;
189 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
190 Changed = !I.swapOperands();
192 if (!I.isAssociative()) return Changed;
193 Instruction::BinaryOps Opcode = I.getOpcode();
194 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
195 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
196 if (isa<Constant>(I.getOperand(1))) {
197 Constant *Folded = ConstantExpr::get(I.getOpcode(),
198 cast<Constant>(I.getOperand(1)),
199 cast<Constant>(Op->getOperand(1)));
200 I.setOperand(0, Op->getOperand(0));
201 I.setOperand(1, Folded);
203 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
204 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
205 isOnlyUse(Op) && isOnlyUse(Op1)) {
206 Constant *C1 = cast<Constant>(Op->getOperand(1));
207 Constant *C2 = cast<Constant>(Op1->getOperand(1));
209 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
210 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
211 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
214 WorkList.push_back(New);
215 I.setOperand(0, New);
216 I.setOperand(1, Folded);
223 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
224 // if the LHS is a constant zero (which is the 'negate' form).
226 static inline Value *dyn_castNegVal(Value *V) {
227 if (BinaryOperator::isNeg(V))
228 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
230 // Constants can be considered to be negated values if they can be folded...
231 if (Constant *C = dyn_cast<Constant>(V))
232 return ConstantExpr::get(Instruction::Sub,
233 Constant::getNullValue(V->getType()), C);
237 static inline Value *dyn_castNotVal(Value *V) {
238 if (BinaryOperator::isNot(V))
239 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
241 // Constants can be considered to be not'ed values...
242 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
243 return ConstantExpr::get(Instruction::Xor,
244 ConstantIntegral::getAllOnesValue(C->getType()),C);
248 // dyn_castFoldableMul - If this value is a multiply that can be folded into
249 // other computations (because it has a constant operand), return the
250 // non-constant operand of the multiply.
252 static inline Value *dyn_castFoldableMul(Value *V) {
253 if (V->hasOneUse() && V->getType()->isInteger())
254 if (Instruction *I = dyn_cast<Instruction>(V))
255 if (I->getOpcode() == Instruction::Mul)
256 if (isa<Constant>(I->getOperand(1)))
257 return I->getOperand(0);
261 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
262 // a constant, return the constant being anded with.
264 template<class ValueType>
265 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
266 if (Instruction *I = dyn_cast<Instruction>(V))
267 if (I->getOpcode() == Instruction::And)
268 return dyn_cast<Constant>(I->getOperand(1));
270 // If this is a constant, it acts just like we were masking with it.
271 return dyn_cast<Constant>(V);
274 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
276 static unsigned Log2(uint64_t Val) {
277 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
280 if (Val & 1) return 0; // Multiple bits set?
288 /// AssociativeOpt - Perform an optimization on an associative operator. This
289 /// function is designed to check a chain of associative operators for a
290 /// potential to apply a certain optimization. Since the optimization may be
291 /// applicable if the expression was reassociated, this checks the chain, then
292 /// reassociates the expression as necessary to expose the optimization
293 /// opportunity. This makes use of a special Functor, which must define
294 /// 'shouldApply' and 'apply' methods.
296 template<typename Functor>
297 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
298 unsigned Opcode = Root.getOpcode();
299 Value *LHS = Root.getOperand(0);
301 // Quick check, see if the immediate LHS matches...
302 if (F.shouldApply(LHS))
303 return F.apply(Root);
305 // Otherwise, if the LHS is not of the same opcode as the root, return.
306 Instruction *LHSI = dyn_cast<Instruction>(LHS);
307 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
308 // Should we apply this transform to the RHS?
309 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
311 // If not to the RHS, check to see if we should apply to the LHS...
312 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
313 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
317 // If the functor wants to apply the optimization to the RHS of LHSI,
318 // reassociate the expression from ((? op A) op B) to (? op (A op B))
320 BasicBlock *BB = Root.getParent();
321 // All of the instructions have a single use and have no side-effects,
322 // because of this, we can pull them all into the current basic block.
323 if (LHSI->getParent() != BB) {
324 // Move all of the instructions from root to LHSI into the current
326 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
327 Instruction *LastUse = &Root;
328 while (TmpLHSI->getParent() == BB) {
330 TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
333 // Loop over all of the instructions in other blocks, moving them into
335 Value *TmpLHS = TmpLHSI;
337 TmpLHSI = cast<Instruction>(TmpLHS);
338 // Remove from current block...
339 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
340 // Insert before the last instruction...
341 BB->getInstList().insert(LastUse, TmpLHSI);
342 TmpLHS = TmpLHSI->getOperand(0);
343 } while (TmpLHSI != LHSI);
346 // Now all of the instructions are in the current basic block, go ahead
347 // and perform the reassociation.
348 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
350 // First move the selected RHS to the LHS of the root...
351 Root.setOperand(0, LHSI->getOperand(1));
353 // Make what used to be the LHS of the root be the user of the root...
354 Value *ExtraOperand = TmpLHSI->getOperand(1);
355 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
356 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
357 BB->getInstList().remove(&Root); // Remove root from the BB
358 BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
360 // Now propagate the ExtraOperand down the chain of instructions until we
362 while (TmpLHSI != LHSI) {
363 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
364 Value *NextOp = NextLHSI->getOperand(1);
365 NextLHSI->setOperand(1, ExtraOperand);
367 ExtraOperand = NextOp;
370 // Now that the instructions are reassociated, have the functor perform
371 // the transformation...
372 return F.apply(Root);
375 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
381 // AddRHS - Implements: X + X --> X << 1
384 AddRHS(Value *rhs) : RHS(rhs) {}
385 bool shouldApply(Value *LHS) const { return LHS == RHS; }
386 Instruction *apply(BinaryOperator &Add) const {
387 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
388 ConstantInt::get(Type::UByteTy, 1));
392 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
394 struct AddMaskingAnd {
396 AddMaskingAnd(Constant *c) : C2(c) {}
397 bool shouldApply(Value *LHS) const {
398 if (Constant *C1 = dyn_castMaskingAnd(LHS))
399 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
402 Instruction *apply(BinaryOperator &Add) const {
403 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
410 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
411 bool Changed = SimplifyCommutative(I);
412 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
415 if (RHS == Constant::getNullValue(I.getType()))
416 return ReplaceInstUsesWith(I, LHS);
419 if (I.getType()->isInteger())
420 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
423 if (Value *V = dyn_castNegVal(LHS))
424 return BinaryOperator::create(Instruction::Sub, RHS, V);
427 if (!isa<Constant>(RHS))
428 if (Value *V = dyn_castNegVal(RHS))
429 return BinaryOperator::create(Instruction::Sub, LHS, V);
431 // X*C + X --> X * (C+1)
432 if (dyn_castFoldableMul(LHS) == RHS) {
434 ConstantExpr::get(Instruction::Add,
435 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
436 ConstantInt::get(I.getType(), 1));
437 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
440 // X + X*C --> X * (C+1)
441 if (dyn_castFoldableMul(RHS) == LHS) {
443 ConstantExpr::get(Instruction::Add,
444 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
445 ConstantInt::get(I.getType(), 1));
446 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
449 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
450 if (Constant *C2 = dyn_castMaskingAnd(RHS))
451 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
453 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
454 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
455 switch (ILHS->getOpcode()) {
456 case Instruction::Xor:
457 // ~X + C --> (C-1) - X
458 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
459 if (XorRHS->isAllOnesValue())
460 return BinaryOperator::create(Instruction::Sub,
461 *CRHS - *ConstantInt::get(I.getType(), 1),
462 ILHS->getOperand(0));
469 return Changed ? &I : 0;
472 // isSignBit - Return true if the value represented by the constant only has the
473 // highest order bit set.
474 static bool isSignBit(ConstantInt *CI) {
475 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
476 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
479 static unsigned getTypeSizeInBits(const Type *Ty) {
480 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
483 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
484 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
486 if (Op0 == Op1) // sub X, X -> 0
487 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
489 // If this is a 'B = x-(-A)', change to B = x+A...
490 if (Value *V = dyn_castNegVal(Op1))
491 return BinaryOperator::create(Instruction::Add, Op0, V);
493 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
494 // Replace (-1 - A) with (~A)...
495 if (C->isAllOnesValue())
496 return BinaryOperator::createNot(Op1);
498 // C - ~X == X + (1+C)
499 if (BinaryOperator::isNot(Op1))
500 return BinaryOperator::create(Instruction::Add,
501 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
502 *C + *ConstantInt::get(I.getType(), 1));
505 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
506 if (Op1I->hasOneUse()) {
507 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
508 // is not used by anyone else...
510 if (Op1I->getOpcode() == Instruction::Sub) {
511 // Swap the two operands of the subexpr...
512 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
513 Op1I->setOperand(0, IIOp1);
514 Op1I->setOperand(1, IIOp0);
516 // Create the new top level add instruction...
517 return BinaryOperator::create(Instruction::Add, Op0, Op1);
520 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
522 if (Op1I->getOpcode() == Instruction::And &&
523 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
524 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
526 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
527 return BinaryOperator::create(Instruction::And, Op0, NewNot);
530 // X - X*C --> X * (1-C)
531 if (dyn_castFoldableMul(Op1I) == Op0) {
533 ConstantExpr::get(Instruction::Sub,
534 ConstantInt::get(I.getType(), 1),
535 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
536 assert(CP1 && "Couldn't constant fold 1-C?");
537 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
541 // X*C - X --> X * (C-1)
542 if (dyn_castFoldableMul(Op0) == Op1) {
544 ConstantExpr::get(Instruction::Sub,
545 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
546 ConstantInt::get(I.getType(), 1));
547 assert(CP1 && "Couldn't constant fold C - 1?");
548 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
554 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
555 bool Changed = SimplifyCommutative(I);
556 Value *Op0 = I.getOperand(0);
558 // Simplify mul instructions with a constant RHS...
559 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
560 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
562 // ((X << C1)*C2) == (X * (C2 << C1))
563 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
564 if (SI->getOpcode() == Instruction::Shl)
565 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
566 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
569 if (CI->isNullValue())
570 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
571 if (CI->equalsInt(1)) // X * 1 == X
572 return ReplaceInstUsesWith(I, Op0);
573 if (CI->isAllOnesValue()) // X * -1 == 0 - X
574 return BinaryOperator::createNeg(Op0, I.getName());
576 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
577 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
578 return new ShiftInst(Instruction::Shl, Op0,
579 ConstantUInt::get(Type::UByteTy, C));
581 ConstantFP *Op1F = cast<ConstantFP>(Op1);
582 if (Op1F->isNullValue())
583 return ReplaceInstUsesWith(I, Op1);
585 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
586 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
587 if (Op1F->getValue() == 1.0)
588 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
592 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
593 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
594 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
596 return Changed ? &I : 0;
599 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
601 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
602 if (RHS->equalsInt(1))
603 return ReplaceInstUsesWith(I, I.getOperand(0));
605 // Check to see if this is an unsigned division with an exact power of 2,
606 // if so, convert to a right shift.
607 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
608 if (uint64_t Val = C->getValue()) // Don't break X / 0
609 if (uint64_t C = Log2(Val))
610 return new ShiftInst(Instruction::Shr, I.getOperand(0),
611 ConstantUInt::get(Type::UByteTy, C));
614 // 0 / X == 0, we don't need to preserve faults!
615 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
616 if (LHS->equalsInt(0))
617 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
623 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
624 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
625 if (RHS->equalsInt(1)) // X % 1 == 0
626 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
628 // Check to see if this is an unsigned remainder with an exact power of 2,
629 // if so, convert to a bitwise and.
630 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
631 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
633 return BinaryOperator::create(Instruction::And, I.getOperand(0),
634 ConstantUInt::get(I.getType(), Val-1));
637 // 0 % X == 0, we don't need to preserve faults!
638 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
639 if (LHS->equalsInt(0))
640 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
645 // isMaxValueMinusOne - return true if this is Max-1
646 static bool isMaxValueMinusOne(const ConstantInt *C) {
647 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
648 // Calculate -1 casted to the right type...
649 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
650 uint64_t Val = ~0ULL; // All ones
651 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
652 return CU->getValue() == Val-1;
655 const ConstantSInt *CS = cast<ConstantSInt>(C);
657 // Calculate 0111111111..11111
658 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
659 int64_t Val = INT64_MAX; // All ones
660 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
661 return CS->getValue() == Val-1;
664 // isMinValuePlusOne - return true if this is Min+1
665 static bool isMinValuePlusOne(const ConstantInt *C) {
666 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
667 return CU->getValue() == 1;
669 const ConstantSInt *CS = cast<ConstantSInt>(C);
671 // Calculate 1111111111000000000000
672 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
673 int64_t Val = -1; // All ones
674 Val <<= TypeBits-1; // Shift over to the right spot
675 return CS->getValue() == Val+1;
678 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
679 /// are carefully arranged to allow folding of expressions such as:
681 /// (A < B) | (A > B) --> (A != B)
683 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
684 /// represents that the comparison is true if A == B, and bit value '1' is true
687 static unsigned getSetCondCode(const SetCondInst *SCI) {
688 switch (SCI->getOpcode()) {
690 case Instruction::SetGT: return 1;
691 case Instruction::SetEQ: return 2;
692 case Instruction::SetGE: return 3;
693 case Instruction::SetLT: return 4;
694 case Instruction::SetNE: return 5;
695 case Instruction::SetLE: return 6;
698 assert(0 && "Invalid SetCC opcode!");
703 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
704 /// opcode and two operands into either a constant true or false, or a brand new
705 /// SetCC instruction.
706 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
708 case 0: return ConstantBool::False;
709 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
710 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
711 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
712 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
713 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
714 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
715 case 7: return ConstantBool::True;
716 default: assert(0 && "Illegal SetCCCode!"); return 0;
720 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
721 struct FoldSetCCLogical {
724 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
725 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
726 bool shouldApply(Value *V) const {
727 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
728 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
729 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
732 Instruction *apply(BinaryOperator &Log) const {
733 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
734 if (SCI->getOperand(0) != LHS) {
735 assert(SCI->getOperand(1) == LHS);
736 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
739 unsigned LHSCode = getSetCondCode(SCI);
740 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
742 switch (Log.getOpcode()) {
743 case Instruction::And: Code = LHSCode & RHSCode; break;
744 case Instruction::Or: Code = LHSCode | RHSCode; break;
745 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
746 default: assert(0 && "Illegal logical opcode!"); return 0;
749 Value *RV = getSetCCValue(Code, LHS, RHS);
750 if (Instruction *I = dyn_cast<Instruction>(RV))
752 // Otherwise, it's a constant boolean value...
753 return IC.ReplaceInstUsesWith(Log, RV);
758 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
759 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
760 // guaranteed to be either a shift instruction or a binary operator.
761 Instruction *InstCombiner::OptAndOp(Instruction *Op,
762 ConstantIntegral *OpRHS,
763 ConstantIntegral *AndRHS,
764 BinaryOperator &TheAnd) {
765 Value *X = Op->getOperand(0);
766 switch (Op->getOpcode()) {
767 case Instruction::Xor:
768 if ((*AndRHS & *OpRHS)->isNullValue()) {
769 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
770 return BinaryOperator::create(Instruction::And, X, AndRHS);
771 } else if (Op->hasOneUse()) {
772 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
773 std::string OpName = Op->getName(); Op->setName("");
774 Instruction *And = BinaryOperator::create(Instruction::And,
776 InsertNewInstBefore(And, TheAnd);
777 return BinaryOperator::create(Instruction::Xor, And, *AndRHS & *OpRHS);
780 case Instruction::Or:
781 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
782 if ((*AndRHS & *OpRHS)->isNullValue())
783 return BinaryOperator::create(Instruction::And, X, AndRHS);
785 Constant *Together = *AndRHS & *OpRHS;
786 if (Together == AndRHS) // (X | C) & C --> C
787 return ReplaceInstUsesWith(TheAnd, AndRHS);
789 if (Op->hasOneUse() && Together != OpRHS) {
790 // (X | C1) & C2 --> (X | (C1&C2)) & C2
791 std::string Op0Name = Op->getName(); Op->setName("");
792 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
794 InsertNewInstBefore(Or, TheAnd);
795 return BinaryOperator::create(Instruction::And, Or, AndRHS);
799 case Instruction::Add:
800 if (Op->hasOneUse()) {
801 // Adding a one to a single bit bit-field should be turned into an XOR
802 // of the bit. First thing to check is to see if this AND is with a
803 // single bit constant.
804 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
806 // Clear bits that are not part of the constant.
807 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
809 // If there is only one bit set...
810 if ((AndRHSV & (AndRHSV-1)) == 0) {
811 // Ok, at this point, we know that we are masking the result of the
812 // ADD down to exactly one bit. If the constant we are adding has
813 // no bits set below this bit, then we can eliminate the ADD.
814 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
816 // Check to see if any bits below the one bit set in AndRHSV are set.
817 if ((AddRHS & (AndRHSV-1)) == 0) {
818 // If not, the only thing that can effect the output of the AND is
819 // the bit specified by AndRHSV. If that bit is set, the effect of
820 // the XOR is to toggle the bit. If it is clear, then the ADD has
822 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
823 TheAnd.setOperand(0, X);
826 std::string Name = Op->getName(); Op->setName("");
827 // Pull the XOR out of the AND.
828 Instruction *NewAnd =
829 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
830 InsertNewInstBefore(NewAnd, TheAnd);
831 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
838 case Instruction::Shl: {
839 // We know that the AND will not produce any of the bits shifted in, so if
840 // the anded constant includes them, clear them now!
842 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
843 Constant *CI = *AndRHS & *(*AllOne << *OpRHS);
845 TheAnd.setOperand(1, CI);
850 case Instruction::Shr:
851 // We know that the AND will not produce any of the bits shifted in, so if
852 // the anded constant includes them, clear them now! This only applies to
853 // unsigned shifts, because a signed shr may bring in set bits!
855 if (AndRHS->getType()->isUnsigned()) {
856 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
857 Constant *CI = *AndRHS & *(*AllOne >> *OpRHS);
859 TheAnd.setOperand(1, CI);
869 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
870 bool Changed = SimplifyCommutative(I);
871 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
873 // and X, X = X and X, 0 == 0
874 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
875 return ReplaceInstUsesWith(I, Op1);
878 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
879 if (RHS->isAllOnesValue())
880 return ReplaceInstUsesWith(I, Op0);
882 // Optimize a variety of ((val OP C1) & C2) combinations...
883 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
884 Instruction *Op0I = cast<Instruction>(Op0);
885 Value *X = Op0I->getOperand(0);
886 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
887 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
892 Value *Op0NotVal = dyn_castNotVal(Op0);
893 Value *Op1NotVal = dyn_castNotVal(Op1);
895 // (~A & ~B) == (~(A | B)) - Demorgan's Law
896 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
897 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
898 Op1NotVal,I.getName()+".demorgan");
899 InsertNewInstBefore(Or, I);
900 return BinaryOperator::createNot(Or);
903 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
904 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
906 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
907 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
908 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
911 return Changed ? &I : 0;
916 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
917 bool Changed = SimplifyCommutative(I);
918 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
920 // or X, X = X or X, 0 == X
921 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
922 return ReplaceInstUsesWith(I, Op0);
925 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
926 if (RHS->isAllOnesValue())
927 return ReplaceInstUsesWith(I, Op1);
929 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
930 // (X & C1) | C2 --> (X | C2) & (C1|C2)
931 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
932 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
933 std::string Op0Name = Op0I->getName(); Op0I->setName("");
934 Instruction *Or = BinaryOperator::create(Instruction::Or,
935 Op0I->getOperand(0), RHS,
937 InsertNewInstBefore(Or, I);
938 return BinaryOperator::create(Instruction::And, Or, *RHS | *Op0CI);
941 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
942 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
943 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
944 std::string Op0Name = Op0I->getName(); Op0I->setName("");
945 Instruction *Or = BinaryOperator::create(Instruction::Or,
946 Op0I->getOperand(0), RHS,
948 InsertNewInstBefore(Or, I);
949 return BinaryOperator::create(Instruction::Xor, Or, *Op0CI & *~*RHS);
954 // (A & C1)|(A & C2) == A & (C1|C2)
955 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
956 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
957 if (LHS->getOperand(0) == RHS->getOperand(0))
958 if (Constant *C0 = dyn_castMaskingAnd(LHS))
959 if (Constant *C1 = dyn_castMaskingAnd(RHS))
960 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
963 Value *Op0NotVal = dyn_castNotVal(Op0);
964 Value *Op1NotVal = dyn_castNotVal(Op1);
966 if (Op1 == Op0NotVal) // ~A | A == -1
967 return ReplaceInstUsesWith(I,
968 ConstantIntegral::getAllOnesValue(I.getType()));
970 if (Op0 == Op1NotVal) // A | ~A == -1
971 return ReplaceInstUsesWith(I,
972 ConstantIntegral::getAllOnesValue(I.getType()));
974 // (~A | ~B) == (~(A & B)) - Demorgan's Law
975 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
976 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
977 Op1NotVal,I.getName()+".demorgan",
979 WorkList.push_back(And);
980 return BinaryOperator::createNot(And);
983 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
984 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
985 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
988 return Changed ? &I : 0;
993 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
994 bool Changed = SimplifyCommutative(I);
995 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
999 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1001 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1003 if (RHS->isNullValue())
1004 return ReplaceInstUsesWith(I, Op0);
1006 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1007 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1008 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1009 if (RHS == ConstantBool::True && SCI->hasOneUse())
1010 return new SetCondInst(SCI->getInverseCondition(),
1011 SCI->getOperand(0), SCI->getOperand(1));
1013 // ~(c-X) == X-c-1 == X+(-c-1)
1014 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue() &&
1015 isa<Constant>(Op0I->getOperand(0))) {
1016 Constant *ConstantRHS = *-*cast<Constant>(Op0I->getOperand(0)) -
1017 *ConstantInt::get(I.getType(), 1);
1018 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1022 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1023 switch (Op0I->getOpcode()) {
1024 case Instruction::Add:
1025 // ~(X-c) --> (-c-1)-X
1026 if (RHS->isAllOnesValue())
1027 return BinaryOperator::create(Instruction::Sub,
1029 *ConstantInt::get(I.getType(), 1),
1030 Op0I->getOperand(0));
1032 case Instruction::And:
1033 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1034 if ((*RHS & *Op0CI)->isNullValue())
1035 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1037 case Instruction::Or:
1038 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1039 if ((*RHS & *Op0CI) == RHS)
1040 return BinaryOperator::create(Instruction::And, Op0, ~*RHS);
1047 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1049 return ReplaceInstUsesWith(I,
1050 ConstantIntegral::getAllOnesValue(I.getType()));
1052 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1054 return ReplaceInstUsesWith(I,
1055 ConstantIntegral::getAllOnesValue(I.getType()));
1057 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1058 if (Op1I->getOpcode() == Instruction::Or)
1059 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1060 cast<BinaryOperator>(Op1I)->swapOperands();
1062 std::swap(Op0, Op1);
1063 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1065 std::swap(Op0, Op1);
1068 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1069 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1070 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1071 cast<BinaryOperator>(Op0I)->swapOperands();
1072 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1073 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1074 WorkList.push_back(cast<Instruction>(NotB));
1075 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1080 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1081 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1082 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1083 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1084 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1086 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1087 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1088 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1091 return Changed ? &I : 0;
1094 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1095 static Constant *AddOne(ConstantInt *C) {
1096 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1097 ConstantInt::get(C->getType(), 1));
1098 assert(Result && "Constant folding integer addition failed!");
1101 static Constant *SubOne(ConstantInt *C) {
1102 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1103 ConstantInt::get(C->getType(), 1));
1104 assert(Result && "Constant folding integer addition failed!");
1108 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1109 // true when both operands are equal...
1111 static bool isTrueWhenEqual(Instruction &I) {
1112 return I.getOpcode() == Instruction::SetEQ ||
1113 I.getOpcode() == Instruction::SetGE ||
1114 I.getOpcode() == Instruction::SetLE;
1117 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1118 bool Changed = SimplifyCommutative(I);
1119 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1120 const Type *Ty = Op0->getType();
1124 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1126 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1127 if (isa<ConstantPointerNull>(Op1) &&
1128 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1129 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1132 // setcc's with boolean values can always be turned into bitwise operations
1133 if (Ty == Type::BoolTy) {
1134 // If this is <, >, or !=, we can change this into a simple xor instruction
1135 if (!isTrueWhenEqual(I))
1136 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1138 // Otherwise we need to make a temporary intermediate instruction and insert
1139 // it into the instruction stream. This is what we are after:
1141 // seteq bool %A, %B -> ~(A^B)
1142 // setle bool %A, %B -> ~A | B
1143 // setge bool %A, %B -> A | ~B
1145 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1146 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1148 InsertNewInstBefore(Xor, I);
1149 return BinaryOperator::createNot(Xor);
1152 // Handle the setXe cases...
1153 assert(I.getOpcode() == Instruction::SetGE ||
1154 I.getOpcode() == Instruction::SetLE);
1156 if (I.getOpcode() == Instruction::SetGE)
1157 std::swap(Op0, Op1); // Change setge -> setle
1159 // Now we just have the SetLE case.
1160 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1161 InsertNewInstBefore(Not, I);
1162 return BinaryOperator::create(Instruction::Or, Not, Op1);
1165 // Check to see if we are doing one of many comparisons against constant
1166 // integers at the end of their ranges...
1168 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1169 // Simplify seteq and setne instructions...
1170 if (I.getOpcode() == Instruction::SetEQ ||
1171 I.getOpcode() == Instruction::SetNE) {
1172 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1174 // If the first operand is (and|or|xor) with a constant, and the second
1175 // operand is a constant, simplify a bit.
1176 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1177 switch (BO->getOpcode()) {
1178 case Instruction::Add:
1179 if (CI->isNullValue()) {
1180 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1181 // efficiently invertible, or if the add has just this one use.
1182 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1183 if (Value *NegVal = dyn_castNegVal(BOp1))
1184 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1185 else if (Value *NegVal = dyn_castNegVal(BOp0))
1186 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1187 else if (BO->hasOneUse()) {
1188 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1190 InsertNewInstBefore(Neg, I);
1191 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1195 case Instruction::Xor:
1196 // For the xor case, we can xor two constants together, eliminating
1197 // the explicit xor.
1198 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1199 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1203 case Instruction::Sub:
1204 // Replace (([sub|xor] A, B) != 0) with (A != B)
1205 if (CI->isNullValue())
1206 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1210 case Instruction::Or:
1211 // If bits are being or'd in that are not present in the constant we
1212 // are comparing against, then the comparison could never succeed!
1213 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1214 if (!(*BOC & *~*CI)->isNullValue())
1215 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1218 case Instruction::And:
1219 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1220 // If bits are being compared against that are and'd out, then the
1221 // comparison can never succeed!
1222 if (!(*CI & *~*BOC)->isNullValue())
1223 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1225 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1226 // to be a signed value as appropriate.
1227 if (isSignBit(BOC)) {
1228 Value *X = BO->getOperand(0);
1229 // If 'X' is not signed, insert a cast now...
1230 if (!BOC->getType()->isSigned()) {
1232 switch (BOC->getType()->getPrimitiveID()) {
1233 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1234 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1235 case Type::UIntTyID: DestTy = Type::IntTy; break;
1236 case Type::ULongTyID: DestTy = Type::LongTy; break;
1237 default: assert(0 && "Invalid unsigned integer type!"); abort();
1239 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1240 InsertNewInstBefore(NewCI, I);
1243 return new SetCondInst(isSetNE ? Instruction::SetLT :
1244 Instruction::SetGE, X,
1245 Constant::getNullValue(X->getType()));
1253 // Check to see if we are comparing against the minimum or maximum value...
1254 if (CI->isMinValue()) {
1255 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1256 return ReplaceInstUsesWith(I, ConstantBool::False);
1257 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1258 return ReplaceInstUsesWith(I, ConstantBool::True);
1259 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1260 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1261 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1262 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1264 } else if (CI->isMaxValue()) {
1265 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1266 return ReplaceInstUsesWith(I, ConstantBool::False);
1267 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1268 return ReplaceInstUsesWith(I, ConstantBool::True);
1269 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1270 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1271 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1272 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1274 // Comparing against a value really close to min or max?
1275 } else if (isMinValuePlusOne(CI)) {
1276 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1277 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1278 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1279 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1281 } else if (isMaxValueMinusOne(CI)) {
1282 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1283 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1284 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1285 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1289 // Test to see if the operands of the setcc are casted versions of other
1290 // values. If the cast can be stripped off both arguments, we do so now.
1291 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1292 Value *CastOp0 = CI->getOperand(0);
1293 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1294 !isa<Argument>(Op1) &&
1295 (I.getOpcode() == Instruction::SetEQ ||
1296 I.getOpcode() == Instruction::SetNE)) {
1297 // We keep moving the cast from the left operand over to the right
1298 // operand, where it can often be eliminated completely.
1301 // If operand #1 is a cast instruction, see if we can eliminate it as
1303 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1304 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1306 Op1 = CI2->getOperand(0);
1308 // If Op1 is a constant, we can fold the cast into the constant.
1309 if (Op1->getType() != Op0->getType())
1310 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1311 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1313 // Otherwise, cast the RHS right before the setcc
1314 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1315 InsertNewInstBefore(cast<Instruction>(Op1), I);
1317 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1320 // Handle the special case of: setcc (cast bool to X), <cst>
1321 // This comes up when you have code like
1324 // For generality, we handle any zero-extension of any operand comparison
1326 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1327 const Type *SrcTy = CastOp0->getType();
1328 const Type *DestTy = Op0->getType();
1329 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1330 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1331 // Ok, we have an expansion of operand 0 into a new type. Get the
1332 // constant value, masink off bits which are not set in the RHS. These
1333 // could be set if the destination value is signed.
1334 uint64_t ConstVal = ConstantRHS->getRawValue();
1335 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1337 // If the constant we are comparing it with has high bits set, which
1338 // don't exist in the original value, the values could never be equal,
1339 // because the source would be zero extended.
1341 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1342 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1343 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1344 switch (I.getOpcode()) {
1345 default: assert(0 && "Unknown comparison type!");
1346 case Instruction::SetEQ:
1347 return ReplaceInstUsesWith(I, ConstantBool::False);
1348 case Instruction::SetNE:
1349 return ReplaceInstUsesWith(I, ConstantBool::True);
1350 case Instruction::SetLT:
1351 case Instruction::SetLE:
1352 if (DestTy->isSigned() && HasSignBit)
1353 return ReplaceInstUsesWith(I, ConstantBool::False);
1354 return ReplaceInstUsesWith(I, ConstantBool::True);
1355 case Instruction::SetGT:
1356 case Instruction::SetGE:
1357 if (DestTy->isSigned() && HasSignBit)
1358 return ReplaceInstUsesWith(I, ConstantBool::True);
1359 return ReplaceInstUsesWith(I, ConstantBool::False);
1363 // Otherwise, we can replace the setcc with a setcc of the smaller
1365 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1366 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1370 return Changed ? &I : 0;
1375 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1376 assert(I.getOperand(1)->getType() == Type::UByteTy);
1377 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1378 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1380 // shl X, 0 == X and shr X, 0 == X
1381 // shl 0, X == 0 and shr 0, X == 0
1382 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1383 Op0 == Constant::getNullValue(Op0->getType()))
1384 return ReplaceInstUsesWith(I, Op0);
1386 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1388 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1389 if (CSI->isAllOnesValue())
1390 return ReplaceInstUsesWith(I, CSI);
1392 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1393 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1394 // of a signed value.
1396 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1397 if (CUI->getValue() >= TypeBits &&
1398 (!Op0->getType()->isSigned() || isLeftShift))
1399 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1401 // ((X*C1) << C2) == (X * (C1 << C2))
1402 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1403 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1404 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1405 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1409 // If the operand is an bitwise operator with a constant RHS, and the
1410 // shift is the only use, we can pull it out of the shift.
1411 if (Op0->hasOneUse())
1412 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1413 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1414 bool isValid = true; // Valid only for And, Or, Xor
1415 bool highBitSet = false; // Transform if high bit of constant set?
1417 switch (Op0BO->getOpcode()) {
1418 default: isValid = false; break; // Do not perform transform!
1419 case Instruction::Or:
1420 case Instruction::Xor:
1423 case Instruction::And:
1428 // If this is a signed shift right, and the high bit is modified
1429 // by the logical operation, do not perform the transformation.
1430 // The highBitSet boolean indicates the value of the high bit of
1431 // the constant which would cause it to be modified for this
1434 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1435 uint64_t Val = Op0C->getRawValue();
1436 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1441 ConstantFoldShiftInstruction(I.getOpcode(), Op0C, CUI);
1443 Instruction *NewShift =
1444 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1447 InsertNewInstBefore(NewShift, I);
1449 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1454 // If this is a shift of a shift, see if we can fold the two together...
1455 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1456 if (ConstantUInt *ShiftAmt1C =
1457 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1458 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1459 unsigned ShiftAmt2 = CUI->getValue();
1461 // Check for (A << c1) << c2 and (A >> c1) >> c2
1462 if (I.getOpcode() == Op0SI->getOpcode()) {
1463 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1464 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1465 ConstantUInt::get(Type::UByteTy, Amt));
1468 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1469 // signed types, we can only support the (A >> c1) << c2 configuration,
1470 // because it can not turn an arbitrary bit of A into a sign bit.
1471 if (I.getType()->isUnsigned() || isLeftShift) {
1472 // Calculate bitmask for what gets shifted off the edge...
1473 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1475 C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
1477 C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
1480 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1481 C, Op0SI->getOperand(0)->getName()+".mask");
1482 InsertNewInstBefore(Mask, I);
1484 // Figure out what flavor of shift we should use...
1485 if (ShiftAmt1 == ShiftAmt2)
1486 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1487 else if (ShiftAmt1 < ShiftAmt2) {
1488 return new ShiftInst(I.getOpcode(), Mask,
1489 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1491 return new ShiftInst(Op0SI->getOpcode(), Mask,
1492 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1502 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1505 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1506 const Type *DstTy) {
1508 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1509 // are identical and the bits don't get reinterpreted (for example
1510 // int->float->int would not be allowed)
1511 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1514 // Allow free casting and conversion of sizes as long as the sign doesn't
1516 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1517 unsigned SrcSize = SrcTy->getPrimitiveSize();
1518 unsigned MidSize = MidTy->getPrimitiveSize();
1519 unsigned DstSize = DstTy->getPrimitiveSize();
1521 // Cases where we are monotonically decreasing the size of the type are
1522 // always ok, regardless of what sign changes are going on.
1524 if (SrcSize >= MidSize && MidSize >= DstSize)
1527 // Cases where the source and destination type are the same, but the middle
1528 // type is bigger are noops.
1530 if (SrcSize == DstSize && MidSize > SrcSize)
1533 // If we are monotonically growing, things are more complex.
1535 if (SrcSize <= MidSize && MidSize <= DstSize) {
1536 // We have eight combinations of signedness to worry about. Here's the
1538 static const int SignTable[8] = {
1539 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1540 1, // U U U Always ok
1541 1, // U U S Always ok
1542 3, // U S U Ok iff SrcSize != MidSize
1543 3, // U S S Ok iff SrcSize != MidSize
1544 0, // S U U Never ok
1545 2, // S U S Ok iff MidSize == DstSize
1546 1, // S S U Always ok
1547 1, // S S S Always ok
1550 // Choose an action based on the current entry of the signtable that this
1551 // cast of cast refers to...
1552 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1553 switch (SignTable[Row]) {
1554 case 0: return false; // Never ok
1555 case 1: return true; // Always ok
1556 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1557 case 3: // Ok iff SrcSize != MidSize
1558 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1559 default: assert(0 && "Bad entry in sign table!");
1564 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1565 // like: short -> ushort -> uint, because this can create wrong results if
1566 // the input short is negative!
1571 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1572 if (V->getType() == Ty || isa<Constant>(V)) return false;
1573 if (const CastInst *CI = dyn_cast<CastInst>(V))
1574 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1579 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1580 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1581 /// casts that are known to not do anything...
1583 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1584 Instruction *InsertBefore) {
1585 if (V->getType() == DestTy) return V;
1586 if (Constant *C = dyn_cast<Constant>(V))
1587 return ConstantExpr::getCast(C, DestTy);
1589 CastInst *CI = new CastInst(V, DestTy, V->getName());
1590 InsertNewInstBefore(CI, *InsertBefore);
1594 // CastInst simplification
1596 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1597 Value *Src = CI.getOperand(0);
1599 // If the user is casting a value to the same type, eliminate this cast
1601 if (CI.getType() == Src->getType())
1602 return ReplaceInstUsesWith(CI, Src);
1604 // If casting the result of another cast instruction, try to eliminate this
1607 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1608 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1609 CSrc->getType(), CI.getType())) {
1610 // This instruction now refers directly to the cast's src operand. This
1611 // has a good chance of making CSrc dead.
1612 CI.setOperand(0, CSrc->getOperand(0));
1616 // If this is an A->B->A cast, and we are dealing with integral types, try
1617 // to convert this into a logical 'and' instruction.
1619 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1620 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1621 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1622 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1623 assert(CSrc->getType() != Type::ULongTy &&
1624 "Cannot have type bigger than ulong!");
1625 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1626 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1627 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1632 // If casting the result of a getelementptr instruction with no offset, turn
1633 // this into a cast of the original pointer!
1635 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1636 bool AllZeroOperands = true;
1637 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1638 if (!isa<Constant>(GEP->getOperand(i)) ||
1639 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1640 AllZeroOperands = false;
1643 if (AllZeroOperands) {
1644 CI.setOperand(0, GEP->getOperand(0));
1649 // If we are casting a malloc or alloca to a pointer to a type of the same
1650 // size, rewrite the allocation instruction to allocate the "right" type.
1652 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1653 if (AI->hasOneUse() && !AI->isArrayAllocation())
1654 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1655 // Get the type really allocated and the type casted to...
1656 const Type *AllocElTy = AI->getAllocatedType();
1657 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1658 const Type *CastElTy = PTy->getElementType();
1659 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1661 // If the allocation is for an even multiple of the cast type size
1662 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1663 Value *Amt = ConstantUInt::get(Type::UIntTy,
1664 AllocElTySize/CastElTySize);
1665 std::string Name = AI->getName(); AI->setName("");
1666 AllocationInst *New;
1667 if (isa<MallocInst>(AI))
1668 New = new MallocInst(CastElTy, Amt, Name);
1670 New = new AllocaInst(CastElTy, Amt, Name);
1671 InsertNewInstBefore(New, CI);
1672 return ReplaceInstUsesWith(CI, New);
1676 // If the source value is an instruction with only this use, we can attempt to
1677 // propagate the cast into the instruction. Also, only handle integral types
1679 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1680 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1681 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1682 const Type *DestTy = CI.getType();
1683 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1684 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1686 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1687 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1689 switch (SrcI->getOpcode()) {
1690 case Instruction::Add:
1691 case Instruction::Mul:
1692 case Instruction::And:
1693 case Instruction::Or:
1694 case Instruction::Xor:
1695 // If we are discarding information, or just changing the sign, rewrite.
1696 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1697 // Don't insert two casts if they cannot be eliminated. We allow two
1698 // casts to be inserted if the sizes are the same. This could only be
1699 // converting signedness, which is a noop.
1700 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1701 !ValueRequiresCast(Op0, DestTy)) {
1702 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1703 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1704 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1705 ->getOpcode(), Op0c, Op1c);
1709 case Instruction::Shl:
1710 // Allow changing the sign of the source operand. Do not allow changing
1711 // the size of the shift, UNLESS the shift amount is a constant. We
1712 // mush not change variable sized shifts to a smaller size, because it
1713 // is undefined to shift more bits out than exist in the value.
1714 if (DestBitSize == SrcBitSize ||
1715 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1716 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1717 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1726 // CallInst simplification
1728 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1729 return visitCallSite(&CI);
1732 // InvokeInst simplification
1734 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1735 return visitCallSite(&II);
1738 // getPromotedType - Return the specified type promoted as it would be to pass
1739 // though a va_arg area...
1740 static const Type *getPromotedType(const Type *Ty) {
1741 switch (Ty->getPrimitiveID()) {
1742 case Type::SByteTyID:
1743 case Type::ShortTyID: return Type::IntTy;
1744 case Type::UByteTyID:
1745 case Type::UShortTyID: return Type::UIntTy;
1746 case Type::FloatTyID: return Type::DoubleTy;
1751 // visitCallSite - Improvements for call and invoke instructions.
1753 Instruction *InstCombiner::visitCallSite(CallSite CS) {
1754 bool Changed = false;
1756 // If the callee is a constexpr cast of a function, attempt to move the cast
1757 // to the arguments of the call/invoke.
1758 if (transformConstExprCastCall(CS)) return 0;
1760 Value *Callee = CS.getCalledValue();
1761 const PointerType *PTy = cast<PointerType>(Callee->getType());
1762 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1763 if (FTy->isVarArg()) {
1764 // See if we can optimize any arguments passed through the varargs area of
1766 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
1767 E = CS.arg_end(); I != E; ++I)
1768 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
1769 // If this cast does not effect the value passed through the varargs
1770 // area, we can eliminate the use of the cast.
1771 Value *Op = CI->getOperand(0);
1772 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
1779 return Changed ? CS.getInstruction() : 0;
1782 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1783 // attempt to move the cast to the arguments of the call/invoke.
1785 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1786 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1787 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1788 if (CE->getOpcode() != Instruction::Cast ||
1789 !isa<ConstantPointerRef>(CE->getOperand(0)))
1791 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1792 if (!isa<Function>(CPR->getValue())) return false;
1793 Function *Callee = cast<Function>(CPR->getValue());
1794 Instruction *Caller = CS.getInstruction();
1796 // Okay, this is a cast from a function to a different type. Unless doing so
1797 // would cause a type conversion of one of our arguments, change this call to
1798 // be a direct call with arguments casted to the appropriate types.
1800 const FunctionType *FT = Callee->getFunctionType();
1801 const Type *OldRetTy = Caller->getType();
1803 if (Callee->isExternal() &&
1804 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
1805 !Caller->use_empty())
1806 return false; // Cannot transform this return value...
1808 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1809 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1811 CallSite::arg_iterator AI = CS.arg_begin();
1812 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1813 const Type *ParamTy = FT->getParamType(i);
1814 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1815 if (Callee->isExternal() && !isConvertible) return false;
1818 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1819 Callee->isExternal())
1820 return false; // Do not delete arguments unless we have a function body...
1822 // Okay, we decided that this is a safe thing to do: go ahead and start
1823 // inserting cast instructions as necessary...
1824 std::vector<Value*> Args;
1825 Args.reserve(NumActualArgs);
1827 AI = CS.arg_begin();
1828 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1829 const Type *ParamTy = FT->getParamType(i);
1830 if ((*AI)->getType() == ParamTy) {
1831 Args.push_back(*AI);
1833 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1834 InsertNewInstBefore(Cast, *Caller);
1835 Args.push_back(Cast);
1839 // If the function takes more arguments than the call was taking, add them
1841 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1842 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1844 // If we are removing arguments to the function, emit an obnoxious warning...
1845 if (FT->getNumParams() < NumActualArgs)
1846 if (!FT->isVarArg()) {
1847 std::cerr << "WARNING: While resolving call to function '"
1848 << Callee->getName() << "' arguments were dropped!\n";
1850 // Add all of the arguments in their promoted form to the arg list...
1851 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1852 const Type *PTy = getPromotedType((*AI)->getType());
1853 if (PTy != (*AI)->getType()) {
1854 // Must promote to pass through va_arg area!
1855 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1856 InsertNewInstBefore(Cast, *Caller);
1857 Args.push_back(Cast);
1859 Args.push_back(*AI);
1864 if (FT->getReturnType() == Type::VoidTy)
1865 Caller->setName(""); // Void type should not have a name...
1868 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1869 NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(),
1870 Args, Caller->getName(), Caller);
1872 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1875 // Insert a cast of the return type as necessary...
1877 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1878 if (NV->getType() != Type::VoidTy) {
1879 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1881 // If this is an invoke instruction, we should insert it after the first
1882 // non-phi, instruction in the normal successor block.
1883 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1884 BasicBlock::iterator I = II->getNormalDest()->begin();
1885 while (isa<PHINode>(I)) ++I;
1886 InsertNewInstBefore(NC, *I);
1888 // Otherwise, it's a call, just insert cast right after the call instr
1889 InsertNewInstBefore(NC, *Caller);
1891 AddUsesToWorkList(*Caller);
1893 NV = Constant::getNullValue(Caller->getType());
1897 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1898 Caller->replaceAllUsesWith(NV);
1899 Caller->getParent()->getInstList().erase(Caller);
1900 removeFromWorkList(Caller);
1906 // PHINode simplification
1908 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
1909 // If the PHI node only has one incoming value, eliminate the PHI node...
1910 if (PN.getNumIncomingValues() == 1)
1911 return ReplaceInstUsesWith(PN, PN.getIncomingValue(0));
1913 // Otherwise if all of the incoming values are the same for the PHI, replace
1914 // the PHI node with the incoming value.
1917 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
1918 if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself...
1919 if (InVal && PN.getIncomingValue(i) != InVal)
1920 return 0; // Not the same, bail out.
1922 InVal = PN.getIncomingValue(i);
1924 // The only case that could cause InVal to be null is if we have a PHI node
1925 // that only has entries for itself. In this case, there is no entry into the
1926 // loop, so kill the PHI.
1928 if (InVal == 0) InVal = Constant::getNullValue(PN.getType());
1930 // All of the incoming values are the same, replace the PHI node now.
1931 return ReplaceInstUsesWith(PN, InVal);
1935 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1936 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
1937 // If so, eliminate the noop.
1938 if ((GEP.getNumOperands() == 2 &&
1939 GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
1940 GEP.getNumOperands() == 1)
1941 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
1943 // Combine Indices - If the source pointer to this getelementptr instruction
1944 // is a getelementptr instruction, combine the indices of the two
1945 // getelementptr instructions into a single instruction.
1947 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
1948 std::vector<Value *> Indices;
1950 // Can we combine the two pointer arithmetics offsets?
1951 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
1952 isa<Constant>(GEP.getOperand(1))) {
1953 // Replace: gep (gep %P, long C1), long C2, ...
1954 // With: gep %P, long (C1+C2), ...
1955 Value *Sum = ConstantExpr::get(Instruction::Add,
1956 cast<Constant>(Src->getOperand(1)),
1957 cast<Constant>(GEP.getOperand(1)));
1958 assert(Sum && "Constant folding of longs failed!?");
1959 GEP.setOperand(0, Src->getOperand(0));
1960 GEP.setOperand(1, Sum);
1961 AddUsesToWorkList(*Src); // Reduce use count of Src
1963 } else if (Src->getNumOperands() == 2) {
1964 // Replace: gep (gep %P, long B), long A, ...
1965 // With: T = long A+B; gep %P, T, ...
1967 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
1969 Src->getName()+".sum", &GEP);
1970 GEP.setOperand(0, Src->getOperand(0));
1971 GEP.setOperand(1, Sum);
1972 WorkList.push_back(cast<Instruction>(Sum));
1974 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
1975 Src->getNumOperands() != 1) {
1976 // Otherwise we can do the fold if the first index of the GEP is a zero
1977 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
1978 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
1979 } else if (Src->getOperand(Src->getNumOperands()-1) ==
1980 Constant::getNullValue(Type::LongTy)) {
1981 // If the src gep ends with a constant array index, merge this get into
1982 // it, even if we have a non-zero array index.
1983 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
1984 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
1987 if (!Indices.empty())
1988 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
1990 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
1991 // GEP of global variable. If all of the indices for this GEP are
1992 // constants, we can promote this to a constexpr instead of an instruction.
1994 // Scan for nonconstants...
1995 std::vector<Constant*> Indices;
1996 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
1997 for (; I != E && isa<Constant>(*I); ++I)
1998 Indices.push_back(cast<Constant>(*I));
2000 if (I == E) { // If they are all constants...
2002 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2004 // Replace all uses of the GEP with the new constexpr...
2005 return ReplaceInstUsesWith(GEP, CE);
2012 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2013 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2014 if (AI.isArrayAllocation()) // Check C != 1
2015 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2016 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2017 AllocationInst *New = 0;
2019 // Create and insert the replacement instruction...
2020 if (isa<MallocInst>(AI))
2021 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
2023 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2024 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
2027 // Scan to the end of the allocation instructions, to skip over a block of
2028 // allocas if possible...
2030 BasicBlock::iterator It = New;
2031 while (isa<AllocationInst>(*It)) ++It;
2033 // Now that I is pointing to the first non-allocation-inst in the block,
2034 // insert our getelementptr instruction...
2036 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
2037 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2039 // Now make everything use the getelementptr instead of the original
2041 ReplaceInstUsesWith(AI, V);
2047 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2048 Value *Op = FI.getOperand(0);
2050 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2051 if (CastInst *CI = dyn_cast<CastInst>(Op))
2052 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2053 FI.setOperand(0, CI->getOperand(0));
2061 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2062 /// constantexpr, return the constant value being addressed by the constant
2063 /// expression, or null if something is funny.
2065 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2066 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
2067 return 0; // Do not allow stepping over the value!
2069 // Loop over all of the operands, tracking down which value we are
2071 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2072 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2073 ConstantStruct *CS = cast<ConstantStruct>(C);
2074 if (CU->getValue() >= CS->getValues().size()) return 0;
2075 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2076 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2077 ConstantArray *CA = cast<ConstantArray>(C);
2078 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2079 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2085 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2086 Value *Op = LI.getOperand(0);
2087 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2088 Op = CPR->getValue();
2090 // Instcombine load (constant global) into the value loaded...
2091 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2092 if (GV->isConstant() && !GV->isExternal())
2093 return ReplaceInstUsesWith(LI, GV->getInitializer());
2095 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2096 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2097 if (CE->getOpcode() == Instruction::GetElementPtr)
2098 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2099 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2100 if (GV->isConstant() && !GV->isExternal())
2101 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2102 return ReplaceInstUsesWith(LI, V);
2107 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2108 // Change br (not X), label True, label False to: br X, label False, True
2109 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
2110 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2111 BasicBlock *TrueDest = BI.getSuccessor(0);
2112 BasicBlock *FalseDest = BI.getSuccessor(1);
2113 // Swap Destinations and condition...
2115 BI.setSuccessor(0, FalseDest);
2116 BI.setSuccessor(1, TrueDest);
2123 void InstCombiner::removeFromWorkList(Instruction *I) {
2124 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2128 bool InstCombiner::runOnFunction(Function &F) {
2129 bool Changed = false;
2130 TD = &getAnalysis<TargetData>();
2132 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2134 while (!WorkList.empty()) {
2135 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2136 WorkList.pop_back();
2138 // Check to see if we can DCE or ConstantPropagate the instruction...
2139 // Check to see if we can DIE the instruction...
2140 if (isInstructionTriviallyDead(I)) {
2141 // Add operands to the worklist...
2142 if (I->getNumOperands() < 4)
2143 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2144 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2145 WorkList.push_back(Op);
2148 I->getParent()->getInstList().erase(I);
2149 removeFromWorkList(I);
2153 // Instruction isn't dead, see if we can constant propagate it...
2154 if (Constant *C = ConstantFoldInstruction(I)) {
2155 // Add operands to the worklist...
2156 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2157 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2158 WorkList.push_back(Op);
2159 ReplaceInstUsesWith(*I, C);
2162 I->getParent()->getInstList().erase(I);
2163 removeFromWorkList(I);
2167 // Now that we have an instruction, try combining it to simplify it...
2168 if (Instruction *Result = visit(*I)) {
2170 // Should we replace the old instruction with a new one?
2172 // Instructions can end up on the worklist more than once. Make sure
2173 // we do not process an instruction that has been deleted.
2174 removeFromWorkList(I);
2176 // Move the name to the new instruction first...
2177 std::string OldName = I->getName(); I->setName("");
2178 Result->setName(OldName);
2180 // Insert the new instruction into the basic block...
2181 BasicBlock *InstParent = I->getParent();
2182 InstParent->getInstList().insert(I, Result);
2184 // Everything uses the new instruction now...
2185 I->replaceAllUsesWith(Result);
2187 // Erase the old instruction.
2188 InstParent->getInstList().erase(I);
2190 BasicBlock::iterator II = I;
2192 // If the instruction was modified, it's possible that it is now dead.
2193 // if so, remove it.
2194 if (dceInstruction(II)) {
2195 // Instructions may end up in the worklist more than once. Erase them
2197 removeFromWorkList(I);
2203 WorkList.push_back(Result);
2204 AddUsesToWorkList(*Result);
2213 Pass *llvm::createInstructionCombiningPass() {
2214 return new InstCombiner();