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"
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 *visitLoadInst(LoadInst &LI);
106 Instruction *visitBranchInst(BranchInst &BI);
108 // visitInstruction - Specify what to return for unhandled instructions...
109 Instruction *visitInstruction(Instruction &I) { return 0; }
112 Instruction *visitCallSite(CallSite CS);
113 bool transformConstExprCastCall(CallSite CS);
115 // InsertNewInstBefore - insert an instruction New before instruction Old
116 // in the program. Add the new instruction to the worklist.
118 void InsertNewInstBefore(Instruction *New, Instruction &Old) {
119 assert(New && New->getParent() == 0 &&
120 "New instruction already inserted into a basic block!");
121 BasicBlock *BB = Old.getParent();
122 BB->getInstList().insert(&Old, New); // Insert inst
123 WorkList.push_back(New); // Add to worklist
127 // ReplaceInstUsesWith - This method is to be used when an instruction is
128 // found to be dead, replacable with another preexisting expression. Here
129 // we add all uses of I to the worklist, replace all uses of I with the new
130 // value, then return I, so that the inst combiner will know that I was
133 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
134 AddUsesToWorkList(I); // Add all modified instrs to worklist
135 I.replaceAllUsesWith(V);
139 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
140 /// InsertBefore instruction. This is specialized a bit to avoid inserting
141 /// casts that are known to not do anything...
143 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
144 Instruction *InsertBefore);
146 // SimplifyCommutative - This performs a few simplifications for commutative
148 bool SimplifyCommutative(BinaryOperator &I);
150 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
151 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
154 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
157 // getComplexity: Assign a complexity or rank value to LLVM Values...
158 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
159 static unsigned getComplexity(Value *V) {
160 if (isa<Instruction>(V)) {
161 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
165 if (isa<Argument>(V)) return 2;
166 return isa<Constant>(V) ? 0 : 1;
169 // isOnlyUse - Return true if this instruction will be deleted if we stop using
171 static bool isOnlyUse(Value *V) {
172 return V->hasOneUse() || isa<Constant>(V);
175 // SimplifyCommutative - This performs a few simplifications for commutative
178 // 1. Order operands such that they are listed from right (least complex) to
179 // left (most complex). This puts constants before unary operators before
182 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
183 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
185 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
186 bool Changed = false;
187 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
188 Changed = !I.swapOperands();
190 if (!I.isAssociative()) return Changed;
191 Instruction::BinaryOps Opcode = I.getOpcode();
192 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
193 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
194 if (isa<Constant>(I.getOperand(1))) {
195 Constant *Folded = ConstantExpr::get(I.getOpcode(),
196 cast<Constant>(I.getOperand(1)),
197 cast<Constant>(Op->getOperand(1)));
198 I.setOperand(0, Op->getOperand(0));
199 I.setOperand(1, Folded);
201 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
202 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
203 isOnlyUse(Op) && isOnlyUse(Op1)) {
204 Constant *C1 = cast<Constant>(Op->getOperand(1));
205 Constant *C2 = cast<Constant>(Op1->getOperand(1));
207 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
208 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
209 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
212 WorkList.push_back(New);
213 I.setOperand(0, New);
214 I.setOperand(1, Folded);
221 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
222 // if the LHS is a constant zero (which is the 'negate' form).
224 static inline Value *dyn_castNegVal(Value *V) {
225 if (BinaryOperator::isNeg(V))
226 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
228 // Constants can be considered to be negated values if they can be folded...
229 if (Constant *C = dyn_cast<Constant>(V))
230 return ConstantExpr::get(Instruction::Sub,
231 Constant::getNullValue(V->getType()), C);
235 static inline Value *dyn_castNotVal(Value *V) {
236 if (BinaryOperator::isNot(V))
237 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
239 // Constants can be considered to be not'ed values...
240 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
241 return ConstantExpr::get(Instruction::Xor,
242 ConstantIntegral::getAllOnesValue(C->getType()),C);
246 // dyn_castFoldableMul - If this value is a multiply that can be folded into
247 // other computations (because it has a constant operand), return the
248 // non-constant operand of the multiply.
250 static inline Value *dyn_castFoldableMul(Value *V) {
251 if (V->hasOneUse() && V->getType()->isInteger())
252 if (Instruction *I = dyn_cast<Instruction>(V))
253 if (I->getOpcode() == Instruction::Mul)
254 if (isa<Constant>(I->getOperand(1)))
255 return I->getOperand(0);
259 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
260 // a constant, return the constant being anded with.
262 template<class ValueType>
263 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
264 if (Instruction *I = dyn_cast<Instruction>(V))
265 if (I->getOpcode() == Instruction::And)
266 return dyn_cast<Constant>(I->getOperand(1));
268 // If this is a constant, it acts just like we were masking with it.
269 return dyn_cast<Constant>(V);
272 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
274 static unsigned Log2(uint64_t Val) {
275 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
278 if (Val & 1) return 0; // Multiple bits set?
286 /// AssociativeOpt - Perform an optimization on an associative operator. This
287 /// function is designed to check a chain of associative operators for a
288 /// potential to apply a certain optimization. Since the optimization may be
289 /// applicable if the expression was reassociated, this checks the chain, then
290 /// reassociates the expression as necessary to expose the optimization
291 /// opportunity. This makes use of a special Functor, which must define
292 /// 'shouldApply' and 'apply' methods.
294 template<typename Functor>
295 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
296 unsigned Opcode = Root.getOpcode();
297 Value *LHS = Root.getOperand(0);
299 // Quick check, see if the immediate LHS matches...
300 if (F.shouldApply(LHS))
301 return F.apply(Root);
303 // Otherwise, if the LHS is not of the same opcode as the root, return.
304 Instruction *LHSI = dyn_cast<Instruction>(LHS);
305 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
306 // Should we apply this transform to the RHS?
307 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
309 // If not to the RHS, check to see if we should apply to the LHS...
310 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
311 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
315 // If the functor wants to apply the optimization to the RHS of LHSI,
316 // reassociate the expression from ((? op A) op B) to (? op (A op B))
318 BasicBlock *BB = Root.getParent();
319 // All of the instructions have a single use and have no side-effects,
320 // because of this, we can pull them all into the current basic block.
321 if (LHSI->getParent() != BB) {
322 // Move all of the instructions from root to LHSI into the current
324 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
325 Instruction *LastUse = &Root;
326 while (TmpLHSI->getParent() == BB) {
328 TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
331 // Loop over all of the instructions in other blocks, moving them into
333 Value *TmpLHS = TmpLHSI;
335 TmpLHSI = cast<Instruction>(TmpLHS);
336 // Remove from current block...
337 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
338 // Insert before the last instruction...
339 BB->getInstList().insert(LastUse, TmpLHSI);
340 TmpLHS = TmpLHSI->getOperand(0);
341 } while (TmpLHSI != LHSI);
344 // Now all of the instructions are in the current basic block, go ahead
345 // and perform the reassociation.
346 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
348 // First move the selected RHS to the LHS of the root...
349 Root.setOperand(0, LHSI->getOperand(1));
351 // Make what used to be the LHS of the root be the user of the root...
352 Value *ExtraOperand = TmpLHSI->getOperand(1);
353 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
354 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
355 BB->getInstList().remove(&Root); // Remove root from the BB
356 BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
358 // Now propagate the ExtraOperand down the chain of instructions until we
360 while (TmpLHSI != LHSI) {
361 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
362 Value *NextOp = NextLHSI->getOperand(1);
363 NextLHSI->setOperand(1, ExtraOperand);
365 ExtraOperand = NextOp;
368 // Now that the instructions are reassociated, have the functor perform
369 // the transformation...
370 return F.apply(Root);
373 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
379 // AddRHS - Implements: X + X --> X << 1
382 AddRHS(Value *rhs) : RHS(rhs) {}
383 bool shouldApply(Value *LHS) const { return LHS == RHS; }
384 Instruction *apply(BinaryOperator &Add) const {
385 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
386 ConstantInt::get(Type::UByteTy, 1));
390 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
392 struct AddMaskingAnd {
394 AddMaskingAnd(Constant *c) : C2(c) {}
395 bool shouldApply(Value *LHS) const {
396 if (Constant *C1 = dyn_castMaskingAnd(LHS))
397 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
400 Instruction *apply(BinaryOperator &Add) const {
401 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
408 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
409 bool Changed = SimplifyCommutative(I);
410 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
413 if (RHS == Constant::getNullValue(I.getType()))
414 return ReplaceInstUsesWith(I, LHS);
417 if (I.getType()->isInteger())
418 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
421 if (Value *V = dyn_castNegVal(LHS))
422 return BinaryOperator::create(Instruction::Sub, RHS, V);
425 if (!isa<Constant>(RHS))
426 if (Value *V = dyn_castNegVal(RHS))
427 return BinaryOperator::create(Instruction::Sub, LHS, V);
429 // X*C + X --> X * (C+1)
430 if (dyn_castFoldableMul(LHS) == RHS) {
432 ConstantExpr::get(Instruction::Add,
433 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
434 ConstantInt::get(I.getType(), 1));
435 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
438 // X + X*C --> X * (C+1)
439 if (dyn_castFoldableMul(RHS) == LHS) {
441 ConstantExpr::get(Instruction::Add,
442 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
443 ConstantInt::get(I.getType(), 1));
444 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
447 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
448 if (Constant *C2 = dyn_castMaskingAnd(RHS))
449 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
451 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
452 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
453 switch (ILHS->getOpcode()) {
454 case Instruction::Xor:
455 // ~X + C --> (C-1) - X
456 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
457 if (XorRHS->isAllOnesValue())
458 return BinaryOperator::create(Instruction::Sub,
459 *CRHS - *ConstantInt::get(I.getType(), 1),
460 ILHS->getOperand(0));
467 return Changed ? &I : 0;
470 // isSignBit - Return true if the value represented by the constant only has the
471 // highest order bit set.
472 static bool isSignBit(ConstantInt *CI) {
473 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
474 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
477 static unsigned getTypeSizeInBits(const Type *Ty) {
478 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
481 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
482 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
484 if (Op0 == Op1) // sub X, X -> 0
485 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
487 // If this is a 'B = x-(-A)', change to B = x+A...
488 if (Value *V = dyn_castNegVal(Op1))
489 return BinaryOperator::create(Instruction::Add, Op0, V);
491 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
492 // Replace (-1 - A) with (~A)...
493 if (C->isAllOnesValue())
494 return BinaryOperator::createNot(Op1);
496 // C - ~X == X + (1+C)
497 if (BinaryOperator::isNot(Op1))
498 return BinaryOperator::create(Instruction::Add,
499 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
500 *C + *ConstantInt::get(I.getType(), 1));
503 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
504 if (Op1I->hasOneUse()) {
505 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
506 // is not used by anyone else...
508 if (Op1I->getOpcode() == Instruction::Sub) {
509 // Swap the two operands of the subexpr...
510 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
511 Op1I->setOperand(0, IIOp1);
512 Op1I->setOperand(1, IIOp0);
514 // Create the new top level add instruction...
515 return BinaryOperator::create(Instruction::Add, Op0, Op1);
518 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
520 if (Op1I->getOpcode() == Instruction::And &&
521 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
522 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
524 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
525 return BinaryOperator::create(Instruction::And, Op0, NewNot);
528 // X - X*C --> X * (1-C)
529 if (dyn_castFoldableMul(Op1I) == Op0) {
531 ConstantExpr::get(Instruction::Sub,
532 ConstantInt::get(I.getType(), 1),
533 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
534 assert(CP1 && "Couldn't constant fold 1-C?");
535 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
539 // X*C - X --> X * (C-1)
540 if (dyn_castFoldableMul(Op0) == Op1) {
542 ConstantExpr::get(Instruction::Sub,
543 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
544 ConstantInt::get(I.getType(), 1));
545 assert(CP1 && "Couldn't constant fold C - 1?");
546 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
552 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
553 bool Changed = SimplifyCommutative(I);
554 Value *Op0 = I.getOperand(0);
556 // Simplify mul instructions with a constant RHS...
557 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
558 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
560 // ((X << C1)*C2) == (X * (C2 << C1))
561 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
562 if (SI->getOpcode() == Instruction::Shl)
563 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
564 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
567 if (CI->isNullValue())
568 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
569 if (CI->equalsInt(1)) // X * 1 == X
570 return ReplaceInstUsesWith(I, Op0);
571 if (CI->isAllOnesValue()) // X * -1 == 0 - X
572 return BinaryOperator::createNeg(Op0, I.getName());
574 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
575 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
576 return new ShiftInst(Instruction::Shl, Op0,
577 ConstantUInt::get(Type::UByteTy, C));
579 ConstantFP *Op1F = cast<ConstantFP>(Op1);
580 if (Op1F->isNullValue())
581 return ReplaceInstUsesWith(I, Op1);
583 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
584 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
585 if (Op1F->getValue() == 1.0)
586 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
590 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
591 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
592 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
594 return Changed ? &I : 0;
597 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
599 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
600 if (RHS->equalsInt(1))
601 return ReplaceInstUsesWith(I, I.getOperand(0));
603 // Check to see if this is an unsigned division with an exact power of 2,
604 // if so, convert to a right shift.
605 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
606 if (uint64_t Val = C->getValue()) // Don't break X / 0
607 if (uint64_t C = Log2(Val))
608 return new ShiftInst(Instruction::Shr, I.getOperand(0),
609 ConstantUInt::get(Type::UByteTy, C));
612 // 0 / X == 0, we don't need to preserve faults!
613 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
614 if (LHS->equalsInt(0))
615 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
621 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
622 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
623 if (RHS->equalsInt(1)) // X % 1 == 0
624 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
626 // Check to see if this is an unsigned remainder with an exact power of 2,
627 // if so, convert to a bitwise and.
628 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
629 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
631 return BinaryOperator::create(Instruction::And, I.getOperand(0),
632 ConstantUInt::get(I.getType(), Val-1));
635 // 0 % X == 0, we don't need to preserve faults!
636 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
637 if (LHS->equalsInt(0))
638 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
643 // isMaxValueMinusOne - return true if this is Max-1
644 static bool isMaxValueMinusOne(const ConstantInt *C) {
645 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
646 // Calculate -1 casted to the right type...
647 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
648 uint64_t Val = ~0ULL; // All ones
649 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
650 return CU->getValue() == Val-1;
653 const ConstantSInt *CS = cast<ConstantSInt>(C);
655 // Calculate 0111111111..11111
656 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
657 int64_t Val = INT64_MAX; // All ones
658 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
659 return CS->getValue() == Val-1;
662 // isMinValuePlusOne - return true if this is Min+1
663 static bool isMinValuePlusOne(const ConstantInt *C) {
664 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
665 return CU->getValue() == 1;
667 const ConstantSInt *CS = cast<ConstantSInt>(C);
669 // Calculate 1111111111000000000000
670 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
671 int64_t Val = -1; // All ones
672 Val <<= TypeBits-1; // Shift over to the right spot
673 return CS->getValue() == Val+1;
676 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
677 /// are carefully arranged to allow folding of expressions such as:
679 /// (A < B) | (A > B) --> (A != B)
681 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
682 /// represents that the comparison is true if A == B, and bit value '1' is true
685 static unsigned getSetCondCode(const SetCondInst *SCI) {
686 switch (SCI->getOpcode()) {
688 case Instruction::SetGT: return 1;
689 case Instruction::SetEQ: return 2;
690 case Instruction::SetGE: return 3;
691 case Instruction::SetLT: return 4;
692 case Instruction::SetNE: return 5;
693 case Instruction::SetLE: return 6;
696 assert(0 && "Invalid SetCC opcode!");
701 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
702 /// opcode and two operands into either a constant true or false, or a brand new
703 /// SetCC instruction.
704 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
706 case 0: return ConstantBool::False;
707 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
708 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
709 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
710 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
711 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
712 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
713 case 7: return ConstantBool::True;
714 default: assert(0 && "Illegal SetCCCode!"); return 0;
718 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
719 struct FoldSetCCLogical {
722 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
723 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
724 bool shouldApply(Value *V) const {
725 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
726 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
727 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
730 Instruction *apply(BinaryOperator &Log) const {
731 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
732 if (SCI->getOperand(0) != LHS) {
733 assert(SCI->getOperand(1) == LHS);
734 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
737 unsigned LHSCode = getSetCondCode(SCI);
738 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
740 switch (Log.getOpcode()) {
741 case Instruction::And: Code = LHSCode & RHSCode; break;
742 case Instruction::Or: Code = LHSCode | RHSCode; break;
743 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
744 default: assert(0 && "Illegal logical opcode!"); return 0;
747 Value *RV = getSetCCValue(Code, LHS, RHS);
748 if (Instruction *I = dyn_cast<Instruction>(RV))
750 // Otherwise, it's a constant boolean value...
751 return IC.ReplaceInstUsesWith(Log, RV);
756 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
757 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
758 // guaranteed to be either a shift instruction or a binary operator.
759 Instruction *InstCombiner::OptAndOp(Instruction *Op,
760 ConstantIntegral *OpRHS,
761 ConstantIntegral *AndRHS,
762 BinaryOperator &TheAnd) {
763 Value *X = Op->getOperand(0);
764 switch (Op->getOpcode()) {
765 case Instruction::Xor:
766 if ((*AndRHS & *OpRHS)->isNullValue()) {
767 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
768 return BinaryOperator::create(Instruction::And, X, AndRHS);
769 } else if (Op->hasOneUse()) {
770 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
771 std::string OpName = Op->getName(); Op->setName("");
772 Instruction *And = BinaryOperator::create(Instruction::And,
774 InsertNewInstBefore(And, TheAnd);
775 return BinaryOperator::create(Instruction::Xor, And, *AndRHS & *OpRHS);
778 case Instruction::Or:
779 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
780 if ((*AndRHS & *OpRHS)->isNullValue())
781 return BinaryOperator::create(Instruction::And, X, AndRHS);
783 Constant *Together = *AndRHS & *OpRHS;
784 if (Together == AndRHS) // (X | C) & C --> C
785 return ReplaceInstUsesWith(TheAnd, AndRHS);
787 if (Op->hasOneUse() && Together != OpRHS) {
788 // (X | C1) & C2 --> (X | (C1&C2)) & C2
789 std::string Op0Name = Op->getName(); Op->setName("");
790 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
792 InsertNewInstBefore(Or, TheAnd);
793 return BinaryOperator::create(Instruction::And, Or, AndRHS);
797 case Instruction::Add:
798 if (Op->hasOneUse()) {
799 // Adding a one to a single bit bit-field should be turned into an XOR
800 // of the bit. First thing to check is to see if this AND is with a
801 // single bit constant.
802 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
804 // Clear bits that are not part of the constant.
805 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
807 // If there is only one bit set...
808 if ((AndRHSV & (AndRHSV-1)) == 0) {
809 // Ok, at this point, we know that we are masking the result of the
810 // ADD down to exactly one bit. If the constant we are adding has
811 // no bits set below this bit, then we can eliminate the ADD.
812 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
814 // Check to see if any bits below the one bit set in AndRHSV are set.
815 if ((AddRHS & (AndRHSV-1)) == 0) {
816 // If not, the only thing that can effect the output of the AND is
817 // the bit specified by AndRHSV. If that bit is set, the effect of
818 // the XOR is to toggle the bit. If it is clear, then the ADD has
820 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
821 TheAnd.setOperand(0, X);
824 std::string Name = Op->getName(); Op->setName("");
825 // Pull the XOR out of the AND.
826 Instruction *NewAnd =
827 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
828 InsertNewInstBefore(NewAnd, TheAnd);
829 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
836 case Instruction::Shl: {
837 // We know that the AND will not produce any of the bits shifted in, so if
838 // the anded constant includes them, clear them now!
840 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
841 Constant *CI = *AndRHS & *(*AllOne << *OpRHS);
843 TheAnd.setOperand(1, CI);
848 case Instruction::Shr:
849 // We know that the AND will not produce any of the bits shifted in, so if
850 // the anded constant includes them, clear them now! This only applies to
851 // unsigned shifts, because a signed shr may bring in set bits!
853 if (AndRHS->getType()->isUnsigned()) {
854 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
855 Constant *CI = *AndRHS & *(*AllOne >> *OpRHS);
857 TheAnd.setOperand(1, CI);
867 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
868 bool Changed = SimplifyCommutative(I);
869 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
871 // and X, X = X and X, 0 == 0
872 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
873 return ReplaceInstUsesWith(I, Op1);
876 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
877 if (RHS->isAllOnesValue())
878 return ReplaceInstUsesWith(I, Op0);
880 // Optimize a variety of ((val OP C1) & C2) combinations...
881 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
882 Instruction *Op0I = cast<Instruction>(Op0);
883 Value *X = Op0I->getOperand(0);
884 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
885 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
890 Value *Op0NotVal = dyn_castNotVal(Op0);
891 Value *Op1NotVal = dyn_castNotVal(Op1);
893 // (~A & ~B) == (~(A | B)) - Demorgan's Law
894 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
895 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
896 Op1NotVal,I.getName()+".demorgan");
897 InsertNewInstBefore(Or, I);
898 return BinaryOperator::createNot(Or);
901 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
902 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
904 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
905 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
906 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
909 return Changed ? &I : 0;
914 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
915 bool Changed = SimplifyCommutative(I);
916 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
918 // or X, X = X or X, 0 == X
919 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
920 return ReplaceInstUsesWith(I, Op0);
923 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
924 if (RHS->isAllOnesValue())
925 return ReplaceInstUsesWith(I, Op1);
927 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
928 // (X & C1) | C2 --> (X | C2) & (C1|C2)
929 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
930 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
931 std::string Op0Name = Op0I->getName(); Op0I->setName("");
932 Instruction *Or = BinaryOperator::create(Instruction::Or,
933 Op0I->getOperand(0), RHS,
935 InsertNewInstBefore(Or, I);
936 return BinaryOperator::create(Instruction::And, Or, *RHS | *Op0CI);
939 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
940 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
941 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
942 std::string Op0Name = Op0I->getName(); Op0I->setName("");
943 Instruction *Or = BinaryOperator::create(Instruction::Or,
944 Op0I->getOperand(0), RHS,
946 InsertNewInstBefore(Or, I);
947 return BinaryOperator::create(Instruction::Xor, Or, *Op0CI & *~*RHS);
952 // (A & C1)|(A & C2) == A & (C1|C2)
953 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
954 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
955 if (LHS->getOperand(0) == RHS->getOperand(0))
956 if (Constant *C0 = dyn_castMaskingAnd(LHS))
957 if (Constant *C1 = dyn_castMaskingAnd(RHS))
958 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
961 Value *Op0NotVal = dyn_castNotVal(Op0);
962 Value *Op1NotVal = dyn_castNotVal(Op1);
964 if (Op1 == Op0NotVal) // ~A | A == -1
965 return ReplaceInstUsesWith(I,
966 ConstantIntegral::getAllOnesValue(I.getType()));
968 if (Op0 == Op1NotVal) // A | ~A == -1
969 return ReplaceInstUsesWith(I,
970 ConstantIntegral::getAllOnesValue(I.getType()));
972 // (~A | ~B) == (~(A & B)) - Demorgan's Law
973 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
974 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
975 Op1NotVal,I.getName()+".demorgan",
977 WorkList.push_back(And);
978 return BinaryOperator::createNot(And);
981 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
982 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
983 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
986 return Changed ? &I : 0;
991 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
992 bool Changed = SimplifyCommutative(I);
993 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
997 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
999 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1001 if (RHS->isNullValue())
1002 return ReplaceInstUsesWith(I, Op0);
1004 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1005 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1006 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1007 if (RHS == ConstantBool::True && SCI->hasOneUse())
1008 return new SetCondInst(SCI->getInverseCondition(),
1009 SCI->getOperand(0), SCI->getOperand(1));
1011 // ~(c-X) == X-c-1 == X+(-c-1)
1012 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue() &&
1013 isa<Constant>(Op0I->getOperand(0))) {
1014 Constant *ConstantRHS = *-*cast<Constant>(Op0I->getOperand(0)) -
1015 *ConstantInt::get(I.getType(), 1);
1016 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1020 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1021 switch (Op0I->getOpcode()) {
1022 case Instruction::Add:
1023 // ~(X-c) --> (-c-1)-X
1024 if (RHS->isAllOnesValue())
1025 return BinaryOperator::create(Instruction::Sub,
1027 *ConstantInt::get(I.getType(), 1),
1028 Op0I->getOperand(0));
1030 case Instruction::And:
1031 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1032 if ((*RHS & *Op0CI)->isNullValue())
1033 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1035 case Instruction::Or:
1036 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1037 if ((*RHS & *Op0CI) == RHS)
1038 return BinaryOperator::create(Instruction::And, Op0, ~*RHS);
1045 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1047 return ReplaceInstUsesWith(I,
1048 ConstantIntegral::getAllOnesValue(I.getType()));
1050 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1052 return ReplaceInstUsesWith(I,
1053 ConstantIntegral::getAllOnesValue(I.getType()));
1055 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1056 if (Op1I->getOpcode() == Instruction::Or)
1057 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1058 cast<BinaryOperator>(Op1I)->swapOperands();
1060 std::swap(Op0, Op1);
1061 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1063 std::swap(Op0, Op1);
1066 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1067 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1068 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1069 cast<BinaryOperator>(Op0I)->swapOperands();
1070 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1071 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1072 WorkList.push_back(cast<Instruction>(NotB));
1073 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1078 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1079 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1080 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1081 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1082 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1084 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1085 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1086 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1089 return Changed ? &I : 0;
1092 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1093 static Constant *AddOne(ConstantInt *C) {
1094 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1095 ConstantInt::get(C->getType(), 1));
1096 assert(Result && "Constant folding integer addition failed!");
1099 static Constant *SubOne(ConstantInt *C) {
1100 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1101 ConstantInt::get(C->getType(), 1));
1102 assert(Result && "Constant folding integer addition failed!");
1106 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1107 // true when both operands are equal...
1109 static bool isTrueWhenEqual(Instruction &I) {
1110 return I.getOpcode() == Instruction::SetEQ ||
1111 I.getOpcode() == Instruction::SetGE ||
1112 I.getOpcode() == Instruction::SetLE;
1115 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1116 bool Changed = SimplifyCommutative(I);
1117 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1118 const Type *Ty = Op0->getType();
1122 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1124 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1125 if (isa<ConstantPointerNull>(Op1) &&
1126 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1127 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1130 // setcc's with boolean values can always be turned into bitwise operations
1131 if (Ty == Type::BoolTy) {
1132 // If this is <, >, or !=, we can change this into a simple xor instruction
1133 if (!isTrueWhenEqual(I))
1134 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1136 // Otherwise we need to make a temporary intermediate instruction and insert
1137 // it into the instruction stream. This is what we are after:
1139 // seteq bool %A, %B -> ~(A^B)
1140 // setle bool %A, %B -> ~A | B
1141 // setge bool %A, %B -> A | ~B
1143 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1144 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1146 InsertNewInstBefore(Xor, I);
1147 return BinaryOperator::createNot(Xor);
1150 // Handle the setXe cases...
1151 assert(I.getOpcode() == Instruction::SetGE ||
1152 I.getOpcode() == Instruction::SetLE);
1154 if (I.getOpcode() == Instruction::SetGE)
1155 std::swap(Op0, Op1); // Change setge -> setle
1157 // Now we just have the SetLE case.
1158 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1159 InsertNewInstBefore(Not, I);
1160 return BinaryOperator::create(Instruction::Or, Not, Op1);
1163 // Check to see if we are doing one of many comparisons against constant
1164 // integers at the end of their ranges...
1166 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1167 // Simplify seteq and setne instructions...
1168 if (I.getOpcode() == Instruction::SetEQ ||
1169 I.getOpcode() == Instruction::SetNE) {
1170 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1172 // If the first operand is (and|or|xor) with a constant, and the second
1173 // operand is a constant, simplify a bit.
1174 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1175 switch (BO->getOpcode()) {
1176 case Instruction::Add:
1177 if (CI->isNullValue()) {
1178 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1179 // efficiently invertible, or if the add has just this one use.
1180 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1181 if (Value *NegVal = dyn_castNegVal(BOp1))
1182 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1183 else if (Value *NegVal = dyn_castNegVal(BOp0))
1184 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1185 else if (BO->hasOneUse()) {
1186 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1188 InsertNewInstBefore(Neg, I);
1189 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1193 case Instruction::Xor:
1194 // For the xor case, we can xor two constants together, eliminating
1195 // the explicit xor.
1196 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1197 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1201 case Instruction::Sub:
1202 // Replace (([sub|xor] A, B) != 0) with (A != B)
1203 if (CI->isNullValue())
1204 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1208 case Instruction::Or:
1209 // If bits are being or'd in that are not present in the constant we
1210 // are comparing against, then the comparison could never succeed!
1211 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1212 if (!(*BOC & *~*CI)->isNullValue())
1213 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1216 case Instruction::And:
1217 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1218 // If bits are being compared against that are and'd out, then the
1219 // comparison can never succeed!
1220 if (!(*CI & *~*BOC)->isNullValue())
1221 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1223 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1224 // to be a signed value as appropriate.
1225 if (isSignBit(BOC)) {
1226 Value *X = BO->getOperand(0);
1227 // If 'X' is not signed, insert a cast now...
1228 if (!BOC->getType()->isSigned()) {
1230 switch (BOC->getType()->getPrimitiveID()) {
1231 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1232 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1233 case Type::UIntTyID: DestTy = Type::IntTy; break;
1234 case Type::ULongTyID: DestTy = Type::LongTy; break;
1235 default: assert(0 && "Invalid unsigned integer type!"); abort();
1237 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1238 InsertNewInstBefore(NewCI, I);
1241 return new SetCondInst(isSetNE ? Instruction::SetLT :
1242 Instruction::SetGE, X,
1243 Constant::getNullValue(X->getType()));
1251 // Check to see if we are comparing against the minimum or maximum value...
1252 if (CI->isMinValue()) {
1253 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1254 return ReplaceInstUsesWith(I, ConstantBool::False);
1255 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1256 return ReplaceInstUsesWith(I, ConstantBool::True);
1257 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1258 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1259 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1260 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1262 } else if (CI->isMaxValue()) {
1263 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1264 return ReplaceInstUsesWith(I, ConstantBool::False);
1265 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1266 return ReplaceInstUsesWith(I, ConstantBool::True);
1267 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1268 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1269 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1270 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1272 // Comparing against a value really close to min or max?
1273 } else if (isMinValuePlusOne(CI)) {
1274 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1275 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1276 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1277 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1279 } else if (isMaxValueMinusOne(CI)) {
1280 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1281 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1282 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1283 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1287 // Test to see if the operands of the setcc are casted versions of other
1288 // values. If the cast can be stripped off both arguments, we do so now.
1289 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1290 Value *CastOp0 = CI->getOperand(0);
1291 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1292 !isa<Argument>(Op1) &&
1293 (I.getOpcode() == Instruction::SetEQ ||
1294 I.getOpcode() == Instruction::SetNE)) {
1295 // We keep moving the cast from the left operand over to the right
1296 // operand, where it can often be eliminated completely.
1299 // If operand #1 is a cast instruction, see if we can eliminate it as
1301 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1302 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1304 Op1 = CI2->getOperand(0);
1306 // If Op1 is a constant, we can fold the cast into the constant.
1307 if (Op1->getType() != Op0->getType())
1308 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1309 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1311 // Otherwise, cast the RHS right before the setcc
1312 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1313 InsertNewInstBefore(cast<Instruction>(Op1), I);
1315 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1318 // Handle the special case of: setcc (cast bool to X), <cst>
1319 // This comes up when you have code like
1322 // For generality, we handle any zero-extension of any operand comparison
1324 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1325 const Type *SrcTy = CastOp0->getType();
1326 const Type *DestTy = Op0->getType();
1327 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1328 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1329 // Ok, we have an expansion of operand 0 into a new type. Get the
1330 // constant value, masink off bits which are not set in the RHS. These
1331 // could be set if the destination value is signed.
1332 uint64_t ConstVal = ConstantRHS->getRawValue();
1333 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1335 // If the constant we are comparing it with has high bits set, which
1336 // don't exist in the original value, the values could never be equal,
1337 // because the source would be zero extended.
1339 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1340 bool HasSignBit = 1ULL << (DestTy->getPrimitiveSize()*8-1);
1341 if (ConstVal & ((1ULL << SrcBits)-1)) {
1342 switch (I.getOpcode()) {
1343 default: assert(0 && "Unknown comparison type!");
1344 case Instruction::SetEQ:
1345 return ReplaceInstUsesWith(I, ConstantBool::False);
1346 case Instruction::SetNE:
1347 return ReplaceInstUsesWith(I, ConstantBool::True);
1348 case Instruction::SetLT:
1349 case Instruction::SetLE:
1350 if (DestTy->isSigned() && HasSignBit)
1351 return ReplaceInstUsesWith(I, ConstantBool::False);
1352 return ReplaceInstUsesWith(I, ConstantBool::True);
1353 case Instruction::SetGT:
1354 case Instruction::SetGE:
1355 if (DestTy->isSigned() && HasSignBit)
1356 return ReplaceInstUsesWith(I, ConstantBool::True);
1357 return ReplaceInstUsesWith(I, ConstantBool::False);
1361 // Otherwise, we can replace the setcc with a setcc of the smaller
1363 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1364 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1368 return Changed ? &I : 0;
1373 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1374 assert(I.getOperand(1)->getType() == Type::UByteTy);
1375 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1376 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1378 // shl X, 0 == X and shr X, 0 == X
1379 // shl 0, X == 0 and shr 0, X == 0
1380 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1381 Op0 == Constant::getNullValue(Op0->getType()))
1382 return ReplaceInstUsesWith(I, Op0);
1384 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1386 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1387 if (CSI->isAllOnesValue())
1388 return ReplaceInstUsesWith(I, CSI);
1390 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1391 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1392 // of a signed value.
1394 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1395 if (CUI->getValue() >= TypeBits &&
1396 (!Op0->getType()->isSigned() || isLeftShift))
1397 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1399 // ((X*C1) << C2) == (X * (C1 << C2))
1400 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1401 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1402 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1403 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1407 // If the operand is an bitwise operator with a constant RHS, and the
1408 // shift is the only use, we can pull it out of the shift.
1409 if (Op0->hasOneUse())
1410 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1411 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1412 bool isValid = true; // Valid only for And, Or, Xor
1413 bool highBitSet = false; // Transform if high bit of constant set?
1415 switch (Op0BO->getOpcode()) {
1416 default: isValid = false; break; // Do not perform transform!
1417 case Instruction::Or:
1418 case Instruction::Xor:
1421 case Instruction::And:
1426 // If this is a signed shift right, and the high bit is modified
1427 // by the logical operation, do not perform the transformation.
1428 // The highBitSet boolean indicates the value of the high bit of
1429 // the constant which would cause it to be modified for this
1432 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1433 uint64_t Val = Op0C->getRawValue();
1434 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1439 ConstantFoldShiftInstruction(I.getOpcode(), Op0C, CUI);
1441 Instruction *NewShift =
1442 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1445 InsertNewInstBefore(NewShift, I);
1447 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1452 // If this is a shift of a shift, see if we can fold the two together...
1453 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1454 if (ConstantUInt *ShiftAmt1C =
1455 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1456 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1457 unsigned ShiftAmt2 = CUI->getValue();
1459 // Check for (A << c1) << c2 and (A >> c1) >> c2
1460 if (I.getOpcode() == Op0SI->getOpcode()) {
1461 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1462 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1463 ConstantUInt::get(Type::UByteTy, Amt));
1466 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1467 // signed types, we can only support the (A >> c1) << c2 configuration,
1468 // because it can not turn an arbitrary bit of A into a sign bit.
1469 if (I.getType()->isUnsigned() || isLeftShift) {
1470 // Calculate bitmask for what gets shifted off the edge...
1471 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1473 C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
1475 C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
1478 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1479 C, Op0SI->getOperand(0)->getName()+".mask");
1480 InsertNewInstBefore(Mask, I);
1482 // Figure out what flavor of shift we should use...
1483 if (ShiftAmt1 == ShiftAmt2)
1484 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1485 else if (ShiftAmt1 < ShiftAmt2) {
1486 return new ShiftInst(I.getOpcode(), Mask,
1487 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1489 return new ShiftInst(Op0SI->getOpcode(), Mask,
1490 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1500 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1503 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1504 const Type *DstTy) {
1506 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1507 // are identical and the bits don't get reinterpreted (for example
1508 // int->float->int would not be allowed)
1509 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1512 // Allow free casting and conversion of sizes as long as the sign doesn't
1514 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1515 unsigned SrcSize = SrcTy->getPrimitiveSize();
1516 unsigned MidSize = MidTy->getPrimitiveSize();
1517 unsigned DstSize = DstTy->getPrimitiveSize();
1519 // Cases where we are monotonically decreasing the size of the type are
1520 // always ok, regardless of what sign changes are going on.
1522 if (SrcSize >= MidSize && MidSize >= DstSize)
1525 // Cases where the source and destination type are the same, but the middle
1526 // type is bigger are noops.
1528 if (SrcSize == DstSize && MidSize > SrcSize)
1531 // If we are monotonically growing, things are more complex.
1533 if (SrcSize <= MidSize && MidSize <= DstSize) {
1534 // We have eight combinations of signedness to worry about. Here's the
1536 static const int SignTable[8] = {
1537 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1538 1, // U U U Always ok
1539 1, // U U S Always ok
1540 3, // U S U Ok iff SrcSize != MidSize
1541 3, // U S S Ok iff SrcSize != MidSize
1542 0, // S U U Never ok
1543 2, // S U S Ok iff MidSize == DstSize
1544 1, // S S U Always ok
1545 1, // S S S Always ok
1548 // Choose an action based on the current entry of the signtable that this
1549 // cast of cast refers to...
1550 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1551 switch (SignTable[Row]) {
1552 case 0: return false; // Never ok
1553 case 1: return true; // Always ok
1554 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1555 case 3: // Ok iff SrcSize != MidSize
1556 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1557 default: assert(0 && "Bad entry in sign table!");
1562 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1563 // like: short -> ushort -> uint, because this can create wrong results if
1564 // the input short is negative!
1569 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1570 if (V->getType() == Ty || isa<Constant>(V)) return false;
1571 if (const CastInst *CI = dyn_cast<CastInst>(V))
1572 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1577 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1578 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1579 /// casts that are known to not do anything...
1581 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1582 Instruction *InsertBefore) {
1583 if (V->getType() == DestTy) return V;
1584 if (Constant *C = dyn_cast<Constant>(V))
1585 return ConstantExpr::getCast(C, DestTy);
1587 CastInst *CI = new CastInst(V, DestTy, V->getName());
1588 InsertNewInstBefore(CI, *InsertBefore);
1592 // CastInst simplification
1594 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1595 Value *Src = CI.getOperand(0);
1597 // If the user is casting a value to the same type, eliminate this cast
1599 if (CI.getType() == Src->getType())
1600 return ReplaceInstUsesWith(CI, Src);
1602 // If casting the result of another cast instruction, try to eliminate this
1605 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1606 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1607 CSrc->getType(), CI.getType())) {
1608 // This instruction now refers directly to the cast's src operand. This
1609 // has a good chance of making CSrc dead.
1610 CI.setOperand(0, CSrc->getOperand(0));
1614 // If this is an A->B->A cast, and we are dealing with integral types, try
1615 // to convert this into a logical 'and' instruction.
1617 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1618 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1619 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1620 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1621 assert(CSrc->getType() != Type::ULongTy &&
1622 "Cannot have type bigger than ulong!");
1623 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1624 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1625 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1630 // If casting the result of a getelementptr instruction with no offset, turn
1631 // this into a cast of the original pointer!
1633 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1634 bool AllZeroOperands = true;
1635 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1636 if (!isa<Constant>(GEP->getOperand(i)) ||
1637 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1638 AllZeroOperands = false;
1641 if (AllZeroOperands) {
1642 CI.setOperand(0, GEP->getOperand(0));
1647 // If we are casting a malloc or alloca to a pointer to a type of the same
1648 // size, rewrite the allocation instruction to allocate the "right" type.
1650 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1651 if (AI->hasOneUse() && !AI->isArrayAllocation())
1652 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1653 // Get the type really allocated and the type casted to...
1654 const Type *AllocElTy = AI->getAllocatedType();
1655 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1656 const Type *CastElTy = PTy->getElementType();
1657 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1659 // If the allocation is for an even multiple of the cast type size
1660 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1661 Value *Amt = ConstantUInt::get(Type::UIntTy,
1662 AllocElTySize/CastElTySize);
1663 std::string Name = AI->getName(); AI->setName("");
1664 AllocationInst *New;
1665 if (isa<MallocInst>(AI))
1666 New = new MallocInst(CastElTy, Amt, Name);
1668 New = new AllocaInst(CastElTy, Amt, Name);
1669 InsertNewInstBefore(New, CI);
1670 return ReplaceInstUsesWith(CI, New);
1674 // If the source value is an instruction with only this use, we can attempt to
1675 // propagate the cast into the instruction. Also, only handle integral types
1677 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1678 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1679 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1680 const Type *DestTy = CI.getType();
1681 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1682 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1684 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1685 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1687 switch (SrcI->getOpcode()) {
1688 case Instruction::Add:
1689 case Instruction::Mul:
1690 case Instruction::And:
1691 case Instruction::Or:
1692 case Instruction::Xor:
1693 // If we are discarding information, or just changing the sign, rewrite.
1694 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1695 // Don't insert two casts if they cannot be eliminated. We allow two
1696 // casts to be inserted if the sizes are the same. This could only be
1697 // converting signedness, which is a noop.
1698 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1699 !ValueRequiresCast(Op0, DestTy)) {
1700 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1701 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1702 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1703 ->getOpcode(), Op0c, Op1c);
1707 case Instruction::Shl:
1708 // Allow changing the sign of the source operand. Do not allow changing
1709 // the size of the shift, UNLESS the shift amount is a constant. We
1710 // mush not change variable sized shifts to a smaller size, because it
1711 // is undefined to shift more bits out than exist in the value.
1712 if (DestBitSize == SrcBitSize ||
1713 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1714 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1715 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1724 // CallInst simplification
1726 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1727 return visitCallSite(&CI);
1730 // InvokeInst simplification
1732 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1733 return visitCallSite(&II);
1736 // getPromotedType - Return the specified type promoted as it would be to pass
1737 // though a va_arg area...
1738 static const Type *getPromotedType(const Type *Ty) {
1739 switch (Ty->getPrimitiveID()) {
1740 case Type::SByteTyID:
1741 case Type::ShortTyID: return Type::IntTy;
1742 case Type::UByteTyID:
1743 case Type::UShortTyID: return Type::UIntTy;
1744 case Type::FloatTyID: return Type::DoubleTy;
1749 // visitCallSite - Improvements for call and invoke instructions.
1751 Instruction *InstCombiner::visitCallSite(CallSite CS) {
1752 bool Changed = false;
1754 // If the callee is a constexpr cast of a function, attempt to move the cast
1755 // to the arguments of the call/invoke.
1756 if (transformConstExprCastCall(CS)) return 0;
1758 Value *Callee = CS.getCalledValue();
1759 const PointerType *PTy = cast<PointerType>(Callee->getType());
1760 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1761 if (FTy->isVarArg()) {
1762 // See if we can optimize any arguments passed through the varargs area of
1764 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
1765 E = CS.arg_end(); I != E; ++I)
1766 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
1767 // If this cast does not effect the value passed through the varargs
1768 // area, we can eliminate the use of the cast.
1769 Value *Op = CI->getOperand(0);
1770 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
1777 return Changed ? CS.getInstruction() : 0;
1780 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1781 // attempt to move the cast to the arguments of the call/invoke.
1783 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1784 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1785 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1786 if (CE->getOpcode() != Instruction::Cast ||
1787 !isa<ConstantPointerRef>(CE->getOperand(0)))
1789 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1790 if (!isa<Function>(CPR->getValue())) return false;
1791 Function *Callee = cast<Function>(CPR->getValue());
1792 Instruction *Caller = CS.getInstruction();
1794 // Okay, this is a cast from a function to a different type. Unless doing so
1795 // would cause a type conversion of one of our arguments, change this call to
1796 // be a direct call with arguments casted to the appropriate types.
1798 const FunctionType *FT = Callee->getFunctionType();
1799 const Type *OldRetTy = Caller->getType();
1801 if (Callee->isExternal() &&
1802 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()))
1803 return false; // Cannot transform this return value...
1805 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1806 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1808 CallSite::arg_iterator AI = CS.arg_begin();
1809 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1810 const Type *ParamTy = FT->getParamType(i);
1811 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1812 if (Callee->isExternal() && !isConvertible) return false;
1815 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1816 Callee->isExternal())
1817 return false; // Do not delete arguments unless we have a function body...
1819 // Okay, we decided that this is a safe thing to do: go ahead and start
1820 // inserting cast instructions as necessary...
1821 std::vector<Value*> Args;
1822 Args.reserve(NumActualArgs);
1824 AI = CS.arg_begin();
1825 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1826 const Type *ParamTy = FT->getParamType(i);
1827 if ((*AI)->getType() == ParamTy) {
1828 Args.push_back(*AI);
1830 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1831 InsertNewInstBefore(Cast, *Caller);
1832 Args.push_back(Cast);
1836 // If the function takes more arguments than the call was taking, add them
1838 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1839 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1841 // If we are removing arguments to the function, emit an obnoxious warning...
1842 if (FT->getNumParams() < NumActualArgs)
1843 if (!FT->isVarArg()) {
1844 std::cerr << "WARNING: While resolving call to function '"
1845 << Callee->getName() << "' arguments were dropped!\n";
1847 // Add all of the arguments in their promoted form to the arg list...
1848 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1849 const Type *PTy = getPromotedType((*AI)->getType());
1850 if (PTy != (*AI)->getType()) {
1851 // Must promote to pass through va_arg area!
1852 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1853 InsertNewInstBefore(Cast, *Caller);
1854 Args.push_back(Cast);
1856 Args.push_back(*AI);
1861 if (FT->getReturnType() == Type::VoidTy)
1862 Caller->setName(""); // Void type should not have a name...
1865 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1866 NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(),
1867 Args, Caller->getName(), Caller);
1869 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1872 // Insert a cast of the return type as necessary...
1874 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1875 if (NV->getType() != Type::VoidTy) {
1876 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1878 // If this is an invoke instruction, we should insert it after the first
1879 // non-phi, instruction in the normal successor block.
1880 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1881 BasicBlock::iterator I = II->getNormalDest()->begin();
1882 while (isa<PHINode>(I)) ++I;
1883 InsertNewInstBefore(NC, *I);
1885 // Otherwise, it's a call, just insert cast right after the call instr
1886 InsertNewInstBefore(NC, *Caller);
1888 AddUsesToWorkList(*Caller);
1890 NV = Constant::getNullValue(Caller->getType());
1894 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1895 Caller->replaceAllUsesWith(NV);
1896 Caller->getParent()->getInstList().erase(Caller);
1897 removeFromWorkList(Caller);
1903 // PHINode simplification
1905 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
1906 // If the PHI node only has one incoming value, eliminate the PHI node...
1907 if (PN.getNumIncomingValues() == 1)
1908 return ReplaceInstUsesWith(PN, PN.getIncomingValue(0));
1910 // Otherwise if all of the incoming values are the same for the PHI, replace
1911 // the PHI node with the incoming value.
1914 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
1915 if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself...
1916 if (InVal && PN.getIncomingValue(i) != InVal)
1917 return 0; // Not the same, bail out.
1919 InVal = PN.getIncomingValue(i);
1921 // The only case that could cause InVal to be null is if we have a PHI node
1922 // that only has entries for itself. In this case, there is no entry into the
1923 // loop, so kill the PHI.
1925 if (InVal == 0) InVal = Constant::getNullValue(PN.getType());
1927 // All of the incoming values are the same, replace the PHI node now.
1928 return ReplaceInstUsesWith(PN, InVal);
1932 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1933 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
1934 // If so, eliminate the noop.
1935 if ((GEP.getNumOperands() == 2 &&
1936 GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
1937 GEP.getNumOperands() == 1)
1938 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
1940 // Combine Indices - If the source pointer to this getelementptr instruction
1941 // is a getelementptr instruction, combine the indices of the two
1942 // getelementptr instructions into a single instruction.
1944 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
1945 std::vector<Value *> Indices;
1947 // Can we combine the two pointer arithmetics offsets?
1948 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
1949 isa<Constant>(GEP.getOperand(1))) {
1950 // Replace: gep (gep %P, long C1), long C2, ...
1951 // With: gep %P, long (C1+C2), ...
1952 Value *Sum = ConstantExpr::get(Instruction::Add,
1953 cast<Constant>(Src->getOperand(1)),
1954 cast<Constant>(GEP.getOperand(1)));
1955 assert(Sum && "Constant folding of longs failed!?");
1956 GEP.setOperand(0, Src->getOperand(0));
1957 GEP.setOperand(1, Sum);
1958 AddUsesToWorkList(*Src); // Reduce use count of Src
1960 } else if (Src->getNumOperands() == 2) {
1961 // Replace: gep (gep %P, long B), long A, ...
1962 // With: T = long A+B; gep %P, T, ...
1964 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
1966 Src->getName()+".sum", &GEP);
1967 GEP.setOperand(0, Src->getOperand(0));
1968 GEP.setOperand(1, Sum);
1969 WorkList.push_back(cast<Instruction>(Sum));
1971 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
1972 Src->getNumOperands() != 1) {
1973 // Otherwise we can do the fold if the first index of the GEP is a zero
1974 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
1975 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
1976 } else if (Src->getOperand(Src->getNumOperands()-1) ==
1977 Constant::getNullValue(Type::LongTy)) {
1978 // If the src gep ends with a constant array index, merge this get into
1979 // it, even if we have a non-zero array index.
1980 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
1981 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
1984 if (!Indices.empty())
1985 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
1987 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
1988 // GEP of global variable. If all of the indices for this GEP are
1989 // constants, we can promote this to a constexpr instead of an instruction.
1991 // Scan for nonconstants...
1992 std::vector<Constant*> Indices;
1993 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
1994 for (; I != E && isa<Constant>(*I); ++I)
1995 Indices.push_back(cast<Constant>(*I));
1997 if (I == E) { // If they are all constants...
1999 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2001 // Replace all uses of the GEP with the new constexpr...
2002 return ReplaceInstUsesWith(GEP, CE);
2009 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2010 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2011 if (AI.isArrayAllocation()) // Check C != 1
2012 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2013 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2014 AllocationInst *New = 0;
2016 // Create and insert the replacement instruction...
2017 if (isa<MallocInst>(AI))
2018 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
2020 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2021 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
2024 // Scan to the end of the allocation instructions, to skip over a block of
2025 // allocas if possible...
2027 BasicBlock::iterator It = New;
2028 while (isa<AllocationInst>(*It)) ++It;
2030 // Now that I is pointing to the first non-allocation-inst in the block,
2031 // insert our getelementptr instruction...
2033 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
2034 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2036 // Now make everything use the getelementptr instead of the original
2038 ReplaceInstUsesWith(AI, V);
2044 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2045 /// constantexpr, return the constant value being addressed by the constant
2046 /// expression, or null if something is funny.
2048 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2049 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
2050 return 0; // Do not allow stepping over the value!
2052 // Loop over all of the operands, tracking down which value we are
2054 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2055 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2056 ConstantStruct *CS = cast<ConstantStruct>(C);
2057 if (CU->getValue() >= CS->getValues().size()) return 0;
2058 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2059 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2060 ConstantArray *CA = cast<ConstantArray>(C);
2061 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2062 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2068 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2069 Value *Op = LI.getOperand(0);
2070 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2071 Op = CPR->getValue();
2073 // Instcombine load (constant global) into the value loaded...
2074 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2075 if (GV->isConstant() && !GV->isExternal())
2076 return ReplaceInstUsesWith(LI, GV->getInitializer());
2078 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2079 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2080 if (CE->getOpcode() == Instruction::GetElementPtr)
2081 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2082 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2083 if (GV->isConstant() && !GV->isExternal())
2084 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2085 return ReplaceInstUsesWith(LI, V);
2090 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2091 // Change br (not X), label True, label False to: br X, label False, True
2092 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
2093 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2094 BasicBlock *TrueDest = BI.getSuccessor(0);
2095 BasicBlock *FalseDest = BI.getSuccessor(1);
2096 // Swap Destinations and condition...
2098 BI.setSuccessor(0, FalseDest);
2099 BI.setSuccessor(1, TrueDest);
2106 void InstCombiner::removeFromWorkList(Instruction *I) {
2107 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2111 bool InstCombiner::runOnFunction(Function &F) {
2112 bool Changed = false;
2113 TD = &getAnalysis<TargetData>();
2115 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2117 while (!WorkList.empty()) {
2118 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2119 WorkList.pop_back();
2121 // Check to see if we can DCE or ConstantPropagate the instruction...
2122 // Check to see if we can DIE the instruction...
2123 if (isInstructionTriviallyDead(I)) {
2124 // Add operands to the worklist...
2125 if (I->getNumOperands() < 4)
2126 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2127 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2128 WorkList.push_back(Op);
2131 I->getParent()->getInstList().erase(I);
2132 removeFromWorkList(I);
2136 // Instruction isn't dead, see if we can constant propagate it...
2137 if (Constant *C = ConstantFoldInstruction(I)) {
2138 // Add operands to the worklist...
2139 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2140 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2141 WorkList.push_back(Op);
2142 ReplaceInstUsesWith(*I, C);
2145 I->getParent()->getInstList().erase(I);
2146 removeFromWorkList(I);
2150 // Now that we have an instruction, try combining it to simplify it...
2151 if (Instruction *Result = visit(*I)) {
2153 // Should we replace the old instruction with a new one?
2155 // Instructions can end up on the worklist more than once. Make sure
2156 // we do not process an instruction that has been deleted.
2157 removeFromWorkList(I);
2159 // Move the name to the new instruction first...
2160 std::string OldName = I->getName(); I->setName("");
2161 Result->setName(OldName);
2163 // Insert the new instruction into the basic block...
2164 BasicBlock *InstParent = I->getParent();
2165 InstParent->getInstList().insert(I, Result);
2167 // Everything uses the new instruction now...
2168 I->replaceAllUsesWith(Result);
2170 // Erase the old instruction.
2171 InstParent->getInstList().erase(I);
2173 BasicBlock::iterator II = I;
2175 // If the instruction was modified, it's possible that it is now dead.
2176 // if so, remove it.
2177 if (dceInstruction(II)) {
2178 // Instructions may end up in the worklist more than once. Erase them
2180 removeFromWorkList(I);
2186 WorkList.push_back(Result);
2187 AddUsesToWorkList(*Result);
2196 Pass *createInstructionCombiningPass() {
2197 return new InstCombiner();