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 // Replace (-1 - A) with (~A)...
492 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0))
493 if (C->isAllOnesValue())
494 return BinaryOperator::createNot(Op1);
496 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
497 if (Op1I->hasOneUse()) {
498 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
499 // is not used by anyone else...
501 if (Op1I->getOpcode() == Instruction::Sub) {
502 // Swap the two operands of the subexpr...
503 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
504 Op1I->setOperand(0, IIOp1);
505 Op1I->setOperand(1, IIOp0);
507 // Create the new top level add instruction...
508 return BinaryOperator::create(Instruction::Add, Op0, Op1);
511 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
513 if (Op1I->getOpcode() == Instruction::And &&
514 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
515 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
517 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
518 return BinaryOperator::create(Instruction::And, Op0, NewNot);
521 // X - X*C --> X * (1-C)
522 if (dyn_castFoldableMul(Op1I) == Op0) {
524 ConstantExpr::get(Instruction::Sub,
525 ConstantInt::get(I.getType(), 1),
526 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
527 assert(CP1 && "Couldn't constant fold 1-C?");
528 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
532 // X*C - X --> X * (C-1)
533 if (dyn_castFoldableMul(Op0) == Op1) {
535 ConstantExpr::get(Instruction::Sub,
536 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
537 ConstantInt::get(I.getType(), 1));
538 assert(CP1 && "Couldn't constant fold C - 1?");
539 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
545 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
546 bool Changed = SimplifyCommutative(I);
547 Value *Op0 = I.getOperand(0);
549 // Simplify mul instructions with a constant RHS...
550 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
551 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
553 // ((X << C1)*C2) == (X * (C2 << C1))
554 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
555 if (SI->getOpcode() == Instruction::Shl)
556 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
557 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
560 if (CI->isNullValue())
561 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
562 if (CI->equalsInt(1)) // X * 1 == X
563 return ReplaceInstUsesWith(I, Op0);
564 if (CI->isAllOnesValue()) // X * -1 == 0 - X
565 return BinaryOperator::createNeg(Op0, I.getName());
567 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
568 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
569 return new ShiftInst(Instruction::Shl, Op0,
570 ConstantUInt::get(Type::UByteTy, C));
572 ConstantFP *Op1F = cast<ConstantFP>(Op1);
573 if (Op1F->isNullValue())
574 return ReplaceInstUsesWith(I, Op1);
576 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
577 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
578 if (Op1F->getValue() == 1.0)
579 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
583 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
584 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
585 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
587 return Changed ? &I : 0;
590 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
592 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
593 if (RHS->equalsInt(1))
594 return ReplaceInstUsesWith(I, I.getOperand(0));
596 // Check to see if this is an unsigned division with an exact power of 2,
597 // if so, convert to a right shift.
598 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
599 if (uint64_t Val = C->getValue()) // Don't break X / 0
600 if (uint64_t C = Log2(Val))
601 return new ShiftInst(Instruction::Shr, I.getOperand(0),
602 ConstantUInt::get(Type::UByteTy, C));
605 // 0 / X == 0, we don't need to preserve faults!
606 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
607 if (LHS->equalsInt(0))
608 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
614 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
615 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
616 if (RHS->equalsInt(1)) // X % 1 == 0
617 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
619 // Check to see if this is an unsigned remainder with an exact power of 2,
620 // if so, convert to a bitwise and.
621 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
622 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
624 return BinaryOperator::create(Instruction::And, I.getOperand(0),
625 ConstantUInt::get(I.getType(), Val-1));
628 // 0 % X == 0, we don't need to preserve faults!
629 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
630 if (LHS->equalsInt(0))
631 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
636 // isMaxValueMinusOne - return true if this is Max-1
637 static bool isMaxValueMinusOne(const ConstantInt *C) {
638 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
639 // Calculate -1 casted to the right type...
640 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
641 uint64_t Val = ~0ULL; // All ones
642 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
643 return CU->getValue() == Val-1;
646 const ConstantSInt *CS = cast<ConstantSInt>(C);
648 // Calculate 0111111111..11111
649 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
650 int64_t Val = INT64_MAX; // All ones
651 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
652 return CS->getValue() == Val-1;
655 // isMinValuePlusOne - return true if this is Min+1
656 static bool isMinValuePlusOne(const ConstantInt *C) {
657 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
658 return CU->getValue() == 1;
660 const ConstantSInt *CS = cast<ConstantSInt>(C);
662 // Calculate 1111111111000000000000
663 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
664 int64_t Val = -1; // All ones
665 Val <<= TypeBits-1; // Shift over to the right spot
666 return CS->getValue() == Val+1;
669 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
670 /// are carefully arranged to allow folding of expressions such as:
672 /// (A < B) | (A > B) --> (A != B)
674 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
675 /// represents that the comparison is true if A == B, and bit value '1' is true
678 static unsigned getSetCondCode(const SetCondInst *SCI) {
679 switch (SCI->getOpcode()) {
681 case Instruction::SetGT: return 1;
682 case Instruction::SetEQ: return 2;
683 case Instruction::SetGE: return 3;
684 case Instruction::SetLT: return 4;
685 case Instruction::SetNE: return 5;
686 case Instruction::SetLE: return 6;
689 assert(0 && "Invalid SetCC opcode!");
694 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
695 /// opcode and two operands into either a constant true or false, or a brand new
696 /// SetCC instruction.
697 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
699 case 0: return ConstantBool::False;
700 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
701 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
702 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
703 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
704 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
705 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
706 case 7: return ConstantBool::True;
707 default: assert(0 && "Illegal SetCCCode!"); return 0;
711 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
712 struct FoldSetCCLogical {
715 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
716 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
717 bool shouldApply(Value *V) const {
718 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
719 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
720 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
723 Instruction *apply(BinaryOperator &Log) const {
724 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
725 if (SCI->getOperand(0) != LHS) {
726 assert(SCI->getOperand(1) == LHS);
727 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
730 unsigned LHSCode = getSetCondCode(SCI);
731 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
733 switch (Log.getOpcode()) {
734 case Instruction::And: Code = LHSCode & RHSCode; break;
735 case Instruction::Or: Code = LHSCode | RHSCode; break;
736 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
737 default: assert(0 && "Illegal logical opcode!"); return 0;
740 Value *RV = getSetCCValue(Code, LHS, RHS);
741 if (Instruction *I = dyn_cast<Instruction>(RV))
743 // Otherwise, it's a constant boolean value...
744 return IC.ReplaceInstUsesWith(Log, RV);
749 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
750 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
751 // guaranteed to be either a shift instruction or a binary operator.
752 Instruction *InstCombiner::OptAndOp(Instruction *Op,
753 ConstantIntegral *OpRHS,
754 ConstantIntegral *AndRHS,
755 BinaryOperator &TheAnd) {
756 Value *X = Op->getOperand(0);
757 switch (Op->getOpcode()) {
758 case Instruction::Xor:
759 if ((*AndRHS & *OpRHS)->isNullValue()) {
760 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
761 return BinaryOperator::create(Instruction::And, X, AndRHS);
762 } else if (Op->hasOneUse()) {
763 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
764 std::string OpName = Op->getName(); Op->setName("");
765 Instruction *And = BinaryOperator::create(Instruction::And,
767 InsertNewInstBefore(And, TheAnd);
768 return BinaryOperator::create(Instruction::Xor, And, *AndRHS & *OpRHS);
771 case Instruction::Or:
772 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
773 if ((*AndRHS & *OpRHS)->isNullValue())
774 return BinaryOperator::create(Instruction::And, X, AndRHS);
776 Constant *Together = *AndRHS & *OpRHS;
777 if (Together == AndRHS) // (X | C) & C --> C
778 return ReplaceInstUsesWith(TheAnd, AndRHS);
780 if (Op->hasOneUse() && Together != OpRHS) {
781 // (X | C1) & C2 --> (X | (C1&C2)) & C2
782 std::string Op0Name = Op->getName(); Op->setName("");
783 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
785 InsertNewInstBefore(Or, TheAnd);
786 return BinaryOperator::create(Instruction::And, Or, AndRHS);
790 case Instruction::Add:
791 if (Op->hasOneUse()) {
792 // Adding a one to a single bit bit-field should be turned into an XOR
793 // of the bit. First thing to check is to see if this AND is with a
794 // single bit constant.
795 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
797 // Clear bits that are not part of the constant.
798 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
800 // If there is only one bit set...
801 if ((AndRHSV & (AndRHSV-1)) == 0) {
802 // Ok, at this point, we know that we are masking the result of the
803 // ADD down to exactly one bit. If the constant we are adding has
804 // no bits set below this bit, then we can eliminate the ADD.
805 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
807 // Check to see if any bits below the one bit set in AndRHSV are set.
808 if ((AddRHS & (AndRHSV-1)) == 0) {
809 // If not, the only thing that can effect the output of the AND is
810 // the bit specified by AndRHSV. If that bit is set, the effect of
811 // the XOR is to toggle the bit. If it is clear, then the ADD has
813 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
814 TheAnd.setOperand(0, X);
817 std::string Name = Op->getName(); Op->setName("");
818 // Pull the XOR out of the AND.
819 Instruction *NewAnd =
820 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
821 InsertNewInstBefore(NewAnd, TheAnd);
822 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
829 case Instruction::Shl: {
830 // We know that the AND will not produce any of the bits shifted in, so if
831 // the anded constant includes them, clear them now!
833 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
834 Constant *CI = *AndRHS & *(*AllOne << *OpRHS);
836 TheAnd.setOperand(1, CI);
841 case Instruction::Shr:
842 // We know that the AND will not produce any of the bits shifted in, so if
843 // the anded constant includes them, clear them now! This only applies to
844 // unsigned shifts, because a signed shr may bring in set bits!
846 if (AndRHS->getType()->isUnsigned()) {
847 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
848 Constant *CI = *AndRHS & *(*AllOne >> *OpRHS);
850 TheAnd.setOperand(1, CI);
860 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
861 bool Changed = SimplifyCommutative(I);
862 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
864 // and X, X = X and X, 0 == 0
865 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
866 return ReplaceInstUsesWith(I, Op1);
869 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
870 if (RHS->isAllOnesValue())
871 return ReplaceInstUsesWith(I, Op0);
873 // Optimize a variety of ((val OP C1) & C2) combinations...
874 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
875 Instruction *Op0I = cast<Instruction>(Op0);
876 Value *X = Op0I->getOperand(0);
877 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
878 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
883 Value *Op0NotVal = dyn_castNotVal(Op0);
884 Value *Op1NotVal = dyn_castNotVal(Op1);
886 // (~A & ~B) == (~(A | B)) - Demorgan's Law
887 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
888 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
889 Op1NotVal,I.getName()+".demorgan");
890 InsertNewInstBefore(Or, I);
891 return BinaryOperator::createNot(Or);
894 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
895 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
897 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
898 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
899 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
902 return Changed ? &I : 0;
907 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
908 bool Changed = SimplifyCommutative(I);
909 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
911 // or X, X = X or X, 0 == X
912 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
913 return ReplaceInstUsesWith(I, Op0);
916 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
917 if (RHS->isAllOnesValue())
918 return ReplaceInstUsesWith(I, Op1);
920 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
921 // (X & C1) | C2 --> (X | C2) & (C1|C2)
922 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
923 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
924 std::string Op0Name = Op0I->getName(); Op0I->setName("");
925 Instruction *Or = BinaryOperator::create(Instruction::Or,
926 Op0I->getOperand(0), RHS,
928 InsertNewInstBefore(Or, I);
929 return BinaryOperator::create(Instruction::And, Or, *RHS | *Op0CI);
932 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
933 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
934 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
935 std::string Op0Name = Op0I->getName(); Op0I->setName("");
936 Instruction *Or = BinaryOperator::create(Instruction::Or,
937 Op0I->getOperand(0), RHS,
939 InsertNewInstBefore(Or, I);
940 return BinaryOperator::create(Instruction::Xor, Or, *Op0CI & *~*RHS);
945 // (A & C1)|(A & C2) == A & (C1|C2)
946 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
947 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
948 if (LHS->getOperand(0) == RHS->getOperand(0))
949 if (Constant *C0 = dyn_castMaskingAnd(LHS))
950 if (Constant *C1 = dyn_castMaskingAnd(RHS))
951 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
954 Value *Op0NotVal = dyn_castNotVal(Op0);
955 Value *Op1NotVal = dyn_castNotVal(Op1);
957 if (Op1 == Op0NotVal) // ~A | A == -1
958 return ReplaceInstUsesWith(I,
959 ConstantIntegral::getAllOnesValue(I.getType()));
961 if (Op0 == Op1NotVal) // A | ~A == -1
962 return ReplaceInstUsesWith(I,
963 ConstantIntegral::getAllOnesValue(I.getType()));
965 // (~A | ~B) == (~(A & B)) - Demorgan's Law
966 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
967 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
968 Op1NotVal,I.getName()+".demorgan",
970 WorkList.push_back(And);
971 return BinaryOperator::createNot(And);
974 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
975 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
976 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
979 return Changed ? &I : 0;
984 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
985 bool Changed = SimplifyCommutative(I);
986 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
990 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
992 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
994 if (RHS->isNullValue())
995 return ReplaceInstUsesWith(I, Op0);
997 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
998 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
999 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1000 if (RHS == ConstantBool::True && SCI->hasOneUse())
1001 return new SetCondInst(SCI->getInverseCondition(),
1002 SCI->getOperand(0), SCI->getOperand(1));
1004 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1005 if (Op0I->getOpcode() == Instruction::And) {
1006 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1007 if ((*RHS & *Op0CI)->isNullValue())
1008 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1009 } else if (Op0I->getOpcode() == Instruction::Or) {
1010 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1011 if ((*RHS & *Op0CI) == RHS)
1012 return BinaryOperator::create(Instruction::And, Op0, ~*RHS);
1017 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1019 return ReplaceInstUsesWith(I,
1020 ConstantIntegral::getAllOnesValue(I.getType()));
1022 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1024 return ReplaceInstUsesWith(I,
1025 ConstantIntegral::getAllOnesValue(I.getType()));
1027 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1028 if (Op1I->getOpcode() == Instruction::Or)
1029 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1030 cast<BinaryOperator>(Op1I)->swapOperands();
1032 std::swap(Op0, Op1);
1033 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1035 std::swap(Op0, Op1);
1038 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1039 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1040 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1041 cast<BinaryOperator>(Op0I)->swapOperands();
1042 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1043 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1044 WorkList.push_back(cast<Instruction>(NotB));
1045 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1050 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1051 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1052 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1053 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1054 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1056 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1057 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1058 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1061 return Changed ? &I : 0;
1064 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1065 static Constant *AddOne(ConstantInt *C) {
1066 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1067 ConstantInt::get(C->getType(), 1));
1068 assert(Result && "Constant folding integer addition failed!");
1071 static Constant *SubOne(ConstantInt *C) {
1072 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1073 ConstantInt::get(C->getType(), 1));
1074 assert(Result && "Constant folding integer addition failed!");
1078 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1079 // true when both operands are equal...
1081 static bool isTrueWhenEqual(Instruction &I) {
1082 return I.getOpcode() == Instruction::SetEQ ||
1083 I.getOpcode() == Instruction::SetGE ||
1084 I.getOpcode() == Instruction::SetLE;
1087 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1088 bool Changed = SimplifyCommutative(I);
1089 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1090 const Type *Ty = Op0->getType();
1094 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1096 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1097 if (isa<ConstantPointerNull>(Op1) &&
1098 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1099 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1102 // setcc's with boolean values can always be turned into bitwise operations
1103 if (Ty == Type::BoolTy) {
1104 // If this is <, >, or !=, we can change this into a simple xor instruction
1105 if (!isTrueWhenEqual(I))
1106 return BinaryOperator::create(Instruction::Xor, Op0, Op1, I.getName());
1108 // Otherwise we need to make a temporary intermediate instruction and insert
1109 // it into the instruction stream. This is what we are after:
1111 // seteq bool %A, %B -> ~(A^B)
1112 // setle bool %A, %B -> ~A | B
1113 // setge bool %A, %B -> A | ~B
1115 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1116 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1118 InsertNewInstBefore(Xor, I);
1119 return BinaryOperator::createNot(Xor, I.getName());
1122 // Handle the setXe cases...
1123 assert(I.getOpcode() == Instruction::SetGE ||
1124 I.getOpcode() == Instruction::SetLE);
1126 if (I.getOpcode() == Instruction::SetGE)
1127 std::swap(Op0, Op1); // Change setge -> setle
1129 // Now we just have the SetLE case.
1130 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1131 InsertNewInstBefore(Not, I);
1132 return BinaryOperator::create(Instruction::Or, Not, Op1, I.getName());
1135 // Check to see if we are doing one of many comparisons against constant
1136 // integers at the end of their ranges...
1138 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1139 // Simplify seteq and setne instructions...
1140 if (I.getOpcode() == Instruction::SetEQ ||
1141 I.getOpcode() == Instruction::SetNE) {
1142 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1144 // If the first operand is (and|or|xor) with a constant, and the second
1145 // operand is a constant, simplify a bit.
1146 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1147 switch (BO->getOpcode()) {
1148 case Instruction::Add:
1149 if (CI->isNullValue()) {
1150 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1151 // efficiently invertible, or if the add has just this one use.
1152 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1153 if (Value *NegVal = dyn_castNegVal(BOp1))
1154 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1155 else if (Value *NegVal = dyn_castNegVal(BOp0))
1156 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1157 else if (BO->hasOneUse()) {
1158 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1160 InsertNewInstBefore(Neg, I);
1161 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1165 case Instruction::Xor:
1166 // For the xor case, we can xor two constants together, eliminating
1167 // the explicit xor.
1168 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1169 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1173 case Instruction::Sub:
1174 // Replace (([sub|xor] A, B) != 0) with (A != B)
1175 if (CI->isNullValue())
1176 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1180 case Instruction::Or:
1181 // If bits are being or'd in that are not present in the constant we
1182 // are comparing against, then the comparison could never succeed!
1183 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1184 if (!(*BOC & *~*CI)->isNullValue())
1185 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1188 case Instruction::And:
1189 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1190 // If bits are being compared against that are and'd out, then the
1191 // comparison can never succeed!
1192 if (!(*CI & *~*BOC)->isNullValue())
1193 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1195 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1196 // to be a signed value as appropriate.
1197 if (isSignBit(BOC)) {
1198 Value *X = BO->getOperand(0);
1199 // If 'X' is not signed, insert a cast now...
1200 if (!BOC->getType()->isSigned()) {
1202 switch (BOC->getType()->getPrimitiveID()) {
1203 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1204 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1205 case Type::UIntTyID: DestTy = Type::IntTy; break;
1206 case Type::ULongTyID: DestTy = Type::LongTy; break;
1207 default: assert(0 && "Invalid unsigned integer type!"); abort();
1209 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1210 InsertNewInstBefore(NewCI, I);
1213 return new SetCondInst(isSetNE ? Instruction::SetLT :
1214 Instruction::SetGE, X,
1215 Constant::getNullValue(X->getType()));
1223 // Check to see if we are comparing against the minimum or maximum value...
1224 if (CI->isMinValue()) {
1225 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1226 return ReplaceInstUsesWith(I, ConstantBool::False);
1227 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1228 return ReplaceInstUsesWith(I, ConstantBool::True);
1229 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1230 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
1231 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1232 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
1234 } else if (CI->isMaxValue()) {
1235 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1236 return ReplaceInstUsesWith(I, ConstantBool::False);
1237 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1238 return ReplaceInstUsesWith(I, ConstantBool::True);
1239 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1240 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
1241 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1242 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
1244 // Comparing against a value really close to min or max?
1245 } else if (isMinValuePlusOne(CI)) {
1246 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1247 return BinaryOperator::create(Instruction::SetEQ, Op0,
1248 SubOne(CI), I.getName());
1249 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1250 return BinaryOperator::create(Instruction::SetNE, Op0,
1251 SubOne(CI), I.getName());
1253 } else if (isMaxValueMinusOne(CI)) {
1254 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1255 return BinaryOperator::create(Instruction::SetEQ, Op0,
1256 AddOne(CI), I.getName());
1257 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1258 return BinaryOperator::create(Instruction::SetNE, Op0,
1259 AddOne(CI), I.getName());
1263 return Changed ? &I : 0;
1268 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1269 assert(I.getOperand(1)->getType() == Type::UByteTy);
1270 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1271 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1273 // shl X, 0 == X and shr X, 0 == X
1274 // shl 0, X == 0 and shr 0, X == 0
1275 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1276 Op0 == Constant::getNullValue(Op0->getType()))
1277 return ReplaceInstUsesWith(I, Op0);
1279 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1281 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1282 if (CSI->isAllOnesValue())
1283 return ReplaceInstUsesWith(I, CSI);
1285 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1286 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1287 // of a signed value.
1289 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1290 if (CUI->getValue() >= TypeBits &&
1291 (!Op0->getType()->isSigned() || isLeftShift))
1292 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1294 // ((X*C1) << C2) == (X * (C1 << C2))
1295 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1296 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1297 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1298 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1302 // If the operand is an bitwise operator with a constant RHS, and the
1303 // shift is the only use, we can pull it out of the shift.
1304 if (Op0->hasOneUse())
1305 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1306 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1307 bool isValid = true; // Valid only for And, Or, Xor
1308 bool highBitSet = false; // Transform if high bit of constant set?
1310 switch (Op0BO->getOpcode()) {
1311 default: isValid = false; break; // Do not perform transform!
1312 case Instruction::Or:
1313 case Instruction::Xor:
1316 case Instruction::And:
1321 // If this is a signed shift right, and the high bit is modified
1322 // by the logical operation, do not perform the transformation.
1323 // The highBitSet boolean indicates the value of the high bit of
1324 // the constant which would cause it to be modified for this
1327 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1328 uint64_t Val = Op0C->getRawValue();
1329 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1334 ConstantFoldShiftInstruction(I.getOpcode(), Op0C, CUI);
1336 Instruction *NewShift =
1337 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1340 InsertNewInstBefore(NewShift, I);
1342 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1347 // If this is a shift of a shift, see if we can fold the two together...
1348 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1349 if (ConstantUInt *ShiftAmt1C =
1350 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1351 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1352 unsigned ShiftAmt2 = CUI->getValue();
1354 // Check for (A << c1) << c2 and (A >> c1) >> c2
1355 if (I.getOpcode() == Op0SI->getOpcode()) {
1356 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1357 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1358 ConstantUInt::get(Type::UByteTy, Amt));
1361 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1362 // signed types, we can only support the (A >> c1) << c2 configuration,
1363 // because it can not turn an arbitrary bit of A into a sign bit.
1364 if (I.getType()->isUnsigned() || isLeftShift) {
1365 // Calculate bitmask for what gets shifted off the edge...
1366 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1368 C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
1370 C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
1373 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1374 C, Op0SI->getOperand(0)->getName()+".mask");
1375 InsertNewInstBefore(Mask, I);
1377 // Figure out what flavor of shift we should use...
1378 if (ShiftAmt1 == ShiftAmt2)
1379 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1380 else if (ShiftAmt1 < ShiftAmt2) {
1381 return new ShiftInst(I.getOpcode(), Mask,
1382 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1384 return new ShiftInst(Op0SI->getOpcode(), Mask,
1385 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1395 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1398 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1399 const Type *DstTy) {
1401 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1402 // are identical and the bits don't get reinterpreted (for example
1403 // int->float->int would not be allowed)
1404 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1407 // Allow free casting and conversion of sizes as long as the sign doesn't
1409 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1410 unsigned SrcSize = SrcTy->getPrimitiveSize();
1411 unsigned MidSize = MidTy->getPrimitiveSize();
1412 unsigned DstSize = DstTy->getPrimitiveSize();
1414 // Cases where we are monotonically decreasing the size of the type are
1415 // always ok, regardless of what sign changes are going on.
1417 if (SrcSize >= MidSize && MidSize >= DstSize)
1420 // Cases where the source and destination type are the same, but the middle
1421 // type is bigger are noops.
1423 if (SrcSize == DstSize && MidSize > SrcSize)
1426 // If we are monotonically growing, things are more complex.
1428 if (SrcSize <= MidSize && MidSize <= DstSize) {
1429 // We have eight combinations of signedness to worry about. Here's the
1431 static const int SignTable[8] = {
1432 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1433 1, // U U U Always ok
1434 1, // U U S Always ok
1435 3, // U S U Ok iff SrcSize != MidSize
1436 3, // U S S Ok iff SrcSize != MidSize
1437 0, // S U U Never ok
1438 2, // S U S Ok iff MidSize == DstSize
1439 1, // S S U Always ok
1440 1, // S S S Always ok
1443 // Choose an action based on the current entry of the signtable that this
1444 // cast of cast refers to...
1445 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1446 switch (SignTable[Row]) {
1447 case 0: return false; // Never ok
1448 case 1: return true; // Always ok
1449 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1450 case 3: // Ok iff SrcSize != MidSize
1451 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1452 default: assert(0 && "Bad entry in sign table!");
1457 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1458 // like: short -> ushort -> uint, because this can create wrong results if
1459 // the input short is negative!
1464 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1465 if (V->getType() == Ty || isa<Constant>(V)) return false;
1466 if (const CastInst *CI = dyn_cast<CastInst>(V))
1467 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1472 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1473 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1474 /// casts that are known to not do anything...
1476 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1477 Instruction *InsertBefore) {
1478 if (V->getType() == DestTy) return V;
1479 if (Constant *C = dyn_cast<Constant>(V))
1480 return ConstantExpr::getCast(C, DestTy);
1482 CastInst *CI = new CastInst(V, DestTy, V->getName());
1483 InsertNewInstBefore(CI, *InsertBefore);
1487 // CastInst simplification
1489 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1490 Value *Src = CI.getOperand(0);
1492 // If the user is casting a value to the same type, eliminate this cast
1494 if (CI.getType() == Src->getType())
1495 return ReplaceInstUsesWith(CI, Src);
1497 // If casting the result of another cast instruction, try to eliminate this
1500 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1501 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1502 CSrc->getType(), CI.getType())) {
1503 // This instruction now refers directly to the cast's src operand. This
1504 // has a good chance of making CSrc dead.
1505 CI.setOperand(0, CSrc->getOperand(0));
1509 // If this is an A->B->A cast, and we are dealing with integral types, try
1510 // to convert this into a logical 'and' instruction.
1512 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1513 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1514 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1515 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1516 assert(CSrc->getType() != Type::ULongTy &&
1517 "Cannot have type bigger than ulong!");
1518 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1519 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1520 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1525 // If casting the result of a getelementptr instruction with no offset, turn
1526 // this into a cast of the original pointer!
1528 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1529 bool AllZeroOperands = true;
1530 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1531 if (!isa<Constant>(GEP->getOperand(i)) ||
1532 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1533 AllZeroOperands = false;
1536 if (AllZeroOperands) {
1537 CI.setOperand(0, GEP->getOperand(0));
1542 // If we are casting a malloc or alloca to a pointer to a type of the same
1543 // size, rewrite the allocation instruction to allocate the "right" type.
1545 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1546 if (AI->hasOneUse())
1547 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1548 // Get the type really allocated and the type casted to...
1549 const Type *AllocElTy = AI->getAllocatedType();
1550 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1551 const Type *CastElTy = PTy->getElementType();
1552 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1554 // If the allocation is for an even multiple of the cast type size
1555 if (AllocElTySize % CastElTySize == 0) {
1556 Value *Amt = ConstantUInt::get(Type::UIntTy,
1557 AllocElTySize/CastElTySize);
1558 std::string Name = AI->getName(); AI->setName("");
1559 AllocationInst *New;
1560 if (isa<MallocInst>(AI))
1561 New = new MallocInst(CastElTy, Amt, Name);
1563 New = new AllocaInst(CastElTy, Amt, Name);
1564 InsertNewInstBefore(New, CI);
1565 return ReplaceInstUsesWith(CI, New);
1569 // If the source value is an instruction with only this use, we can attempt to
1570 // propagate the cast into the instruction. Also, only handle integral types
1572 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1573 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1574 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1575 const Type *DestTy = CI.getType();
1576 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1577 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1579 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1580 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1582 switch (SrcI->getOpcode()) {
1583 case Instruction::Add:
1584 case Instruction::Mul:
1585 case Instruction::And:
1586 case Instruction::Or:
1587 case Instruction::Xor:
1588 // If we are discarding information, or just changing the sign, rewrite.
1589 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1590 // Don't insert two casts if they cannot be eliminated. We allow two
1591 // casts to be inserted if the sizes are the same. This could only be
1592 // converting signedness, which is a noop.
1593 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1594 !ValueRequiresCast(Op0, DestTy)) {
1595 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1596 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1597 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1598 ->getOpcode(), Op0c, Op1c);
1602 case Instruction::Shl:
1603 // Allow changing the sign of the source operand. Do not allow changing
1604 // the size of the shift, UNLESS the shift amount is a constant. We
1605 // mush not change variable sized shifts to a smaller size, because it
1606 // is undefined to shift more bits out than exist in the value.
1607 if (DestBitSize == SrcBitSize ||
1608 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1609 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1610 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1619 // CallInst simplification
1621 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1622 return visitCallSite(&CI);
1625 // InvokeInst simplification
1627 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1628 return visitCallSite(&II);
1631 // getPromotedType - Return the specified type promoted as it would be to pass
1632 // though a va_arg area...
1633 static const Type *getPromotedType(const Type *Ty) {
1634 switch (Ty->getPrimitiveID()) {
1635 case Type::SByteTyID:
1636 case Type::ShortTyID: return Type::IntTy;
1637 case Type::UByteTyID:
1638 case Type::UShortTyID: return Type::UIntTy;
1639 case Type::FloatTyID: return Type::DoubleTy;
1644 // visitCallSite - Improvements for call and invoke instructions.
1646 Instruction *InstCombiner::visitCallSite(CallSite CS) {
1647 bool Changed = false;
1649 // If the callee is a constexpr cast of a function, attempt to move the cast
1650 // to the arguments of the call/invoke.
1651 if (transformConstExprCastCall(CS)) return 0;
1653 Value *Callee = CS.getCalledValue();
1654 const PointerType *PTy = cast<PointerType>(Callee->getType());
1655 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1656 if (FTy->isVarArg()) {
1657 // See if we can optimize any arguments passed through the varargs area of
1659 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
1660 E = CS.arg_end(); I != E; ++I)
1661 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
1662 // If this cast does not effect the value passed through the varargs
1663 // area, we can eliminate the use of the cast.
1664 Value *Op = CI->getOperand(0);
1665 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
1672 return Changed ? CS.getInstruction() : 0;
1675 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1676 // attempt to move the cast to the arguments of the call/invoke.
1678 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1679 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1680 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1681 if (CE->getOpcode() != Instruction::Cast ||
1682 !isa<ConstantPointerRef>(CE->getOperand(0)))
1684 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1685 if (!isa<Function>(CPR->getValue())) return false;
1686 Function *Callee = cast<Function>(CPR->getValue());
1687 Instruction *Caller = CS.getInstruction();
1689 // Okay, this is a cast from a function to a different type. Unless doing so
1690 // would cause a type conversion of one of our arguments, change this call to
1691 // be a direct call with arguments casted to the appropriate types.
1693 const FunctionType *FT = Callee->getFunctionType();
1694 const Type *OldRetTy = Caller->getType();
1696 if (Callee->isExternal() &&
1697 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()))
1698 return false; // Cannot transform this return value...
1700 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1701 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1703 CallSite::arg_iterator AI = CS.arg_begin();
1704 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1705 const Type *ParamTy = FT->getParamType(i);
1706 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1707 if (Callee->isExternal() && !isConvertible) return false;
1710 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1711 Callee->isExternal())
1712 return false; // Do not delete arguments unless we have a function body...
1714 // Okay, we decided that this is a safe thing to do: go ahead and start
1715 // inserting cast instructions as necessary...
1716 std::vector<Value*> Args;
1717 Args.reserve(NumActualArgs);
1719 AI = CS.arg_begin();
1720 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1721 const Type *ParamTy = FT->getParamType(i);
1722 if ((*AI)->getType() == ParamTy) {
1723 Args.push_back(*AI);
1725 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1726 InsertNewInstBefore(Cast, *Caller);
1727 Args.push_back(Cast);
1731 // If the function takes more arguments than the call was taking, add them
1733 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1734 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1736 // If we are removing arguments to the function, emit an obnoxious warning...
1737 if (FT->getNumParams() < NumActualArgs)
1738 if (!FT->isVarArg()) {
1739 std::cerr << "WARNING: While resolving call to function '"
1740 << Callee->getName() << "' arguments were dropped!\n";
1742 // Add all of the arguments in their promoted form to the arg list...
1743 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1744 const Type *PTy = getPromotedType((*AI)->getType());
1745 if (PTy != (*AI)->getType()) {
1746 // Must promote to pass through va_arg area!
1747 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1748 InsertNewInstBefore(Cast, *Caller);
1749 Args.push_back(Cast);
1751 Args.push_back(*AI);
1756 if (FT->getReturnType() == Type::VoidTy)
1757 Caller->setName(""); // Void type should not have a name...
1760 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1761 NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(),
1762 Args, Caller->getName(), Caller);
1764 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1767 // Insert a cast of the return type as necessary...
1769 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1770 if (NV->getType() != Type::VoidTy) {
1771 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1773 // If this is an invoke instruction, we should insert it after the first
1774 // non-phi, instruction in the normal successor block.
1775 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1776 BasicBlock::iterator I = II->getNormalDest()->begin();
1777 while (isa<PHINode>(I)) ++I;
1778 InsertNewInstBefore(NC, *I);
1780 // Otherwise, it's a call, just insert cast right after the call instr
1781 InsertNewInstBefore(NC, *Caller);
1783 AddUsesToWorkList(*Caller);
1785 NV = Constant::getNullValue(Caller->getType());
1789 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1790 Caller->replaceAllUsesWith(NV);
1791 Caller->getParent()->getInstList().erase(Caller);
1792 removeFromWorkList(Caller);
1798 // PHINode simplification
1800 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
1801 // If the PHI node only has one incoming value, eliminate the PHI node...
1802 if (PN.getNumIncomingValues() == 1)
1803 return ReplaceInstUsesWith(PN, PN.getIncomingValue(0));
1805 // Otherwise if all of the incoming values are the same for the PHI, replace
1806 // the PHI node with the incoming value.
1809 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
1810 if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself...
1811 if (InVal && PN.getIncomingValue(i) != InVal)
1812 return 0; // Not the same, bail out.
1814 InVal = PN.getIncomingValue(i);
1816 // The only case that could cause InVal to be null is if we have a PHI node
1817 // that only has entries for itself. In this case, there is no entry into the
1818 // loop, so kill the PHI.
1820 if (InVal == 0) InVal = Constant::getNullValue(PN.getType());
1822 // All of the incoming values are the same, replace the PHI node now.
1823 return ReplaceInstUsesWith(PN, InVal);
1827 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1828 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
1829 // If so, eliminate the noop.
1830 if ((GEP.getNumOperands() == 2 &&
1831 GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
1832 GEP.getNumOperands() == 1)
1833 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
1835 // Combine Indices - If the source pointer to this getelementptr instruction
1836 // is a getelementptr instruction, combine the indices of the two
1837 // getelementptr instructions into a single instruction.
1839 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
1840 std::vector<Value *> Indices;
1842 // Can we combine the two pointer arithmetics offsets?
1843 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
1844 isa<Constant>(GEP.getOperand(1))) {
1845 // Replace: gep (gep %P, long C1), long C2, ...
1846 // With: gep %P, long (C1+C2), ...
1847 Value *Sum = ConstantExpr::get(Instruction::Add,
1848 cast<Constant>(Src->getOperand(1)),
1849 cast<Constant>(GEP.getOperand(1)));
1850 assert(Sum && "Constant folding of longs failed!?");
1851 GEP.setOperand(0, Src->getOperand(0));
1852 GEP.setOperand(1, Sum);
1853 AddUsesToWorkList(*Src); // Reduce use count of Src
1855 } else if (Src->getNumOperands() == 2) {
1856 // Replace: gep (gep %P, long B), long A, ...
1857 // With: T = long A+B; gep %P, T, ...
1859 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
1861 Src->getName()+".sum", &GEP);
1862 GEP.setOperand(0, Src->getOperand(0));
1863 GEP.setOperand(1, Sum);
1864 WorkList.push_back(cast<Instruction>(Sum));
1866 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
1867 Src->getNumOperands() != 1) {
1868 // Otherwise we can do the fold if the first index of the GEP is a zero
1869 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
1870 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
1871 } else if (Src->getOperand(Src->getNumOperands()-1) ==
1872 Constant::getNullValue(Type::LongTy)) {
1873 // If the src gep ends with a constant array index, merge this get into
1874 // it, even if we have a non-zero array index.
1875 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
1876 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
1879 if (!Indices.empty())
1880 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
1882 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
1883 // GEP of global variable. If all of the indices for this GEP are
1884 // constants, we can promote this to a constexpr instead of an instruction.
1886 // Scan for nonconstants...
1887 std::vector<Constant*> Indices;
1888 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
1889 for (; I != E && isa<Constant>(*I); ++I)
1890 Indices.push_back(cast<Constant>(*I));
1892 if (I == E) { // If they are all constants...
1894 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
1896 // Replace all uses of the GEP with the new constexpr...
1897 return ReplaceInstUsesWith(GEP, CE);
1904 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
1905 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
1906 if (AI.isArrayAllocation()) // Check C != 1
1907 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
1908 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
1909 AllocationInst *New = 0;
1911 // Create and insert the replacement instruction...
1912 if (isa<MallocInst>(AI))
1913 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
1915 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
1916 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
1919 // Scan to the end of the allocation instructions, to skip over a block of
1920 // allocas if possible...
1922 BasicBlock::iterator It = New;
1923 while (isa<AllocationInst>(*It)) ++It;
1925 // Now that I is pointing to the first non-allocation-inst in the block,
1926 // insert our getelementptr instruction...
1928 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
1929 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
1931 // Now make everything use the getelementptr instead of the original
1933 ReplaceInstUsesWith(AI, V);
1939 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
1940 /// constantexpr, return the constant value being addressed by the constant
1941 /// expression, or null if something is funny.
1943 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
1944 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
1945 return 0; // Do not allow stepping over the value!
1947 // Loop over all of the operands, tracking down which value we are
1949 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
1950 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
1951 ConstantStruct *CS = cast<ConstantStruct>(C);
1952 if (CU->getValue() >= CS->getValues().size()) return 0;
1953 C = cast<Constant>(CS->getValues()[CU->getValue()]);
1954 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
1955 ConstantArray *CA = cast<ConstantArray>(C);
1956 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
1957 C = cast<Constant>(CA->getValues()[CS->getValue()]);
1963 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
1964 Value *Op = LI.getOperand(0);
1965 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
1966 Op = CPR->getValue();
1968 // Instcombine load (constant global) into the value loaded...
1969 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
1970 if (GV->isConstant() && !GV->isExternal())
1971 return ReplaceInstUsesWith(LI, GV->getInitializer());
1973 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
1974 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
1975 if (CE->getOpcode() == Instruction::GetElementPtr)
1976 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
1977 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
1978 if (GV->isConstant() && !GV->isExternal())
1979 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
1980 return ReplaceInstUsesWith(LI, V);
1985 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
1986 // Change br (not X), label True, label False to: br X, label False, True
1987 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
1988 if (Value *V = dyn_castNotVal(BI.getCondition())) {
1989 BasicBlock *TrueDest = BI.getSuccessor(0);
1990 BasicBlock *FalseDest = BI.getSuccessor(1);
1991 // Swap Destinations and condition...
1993 BI.setSuccessor(0, FalseDest);
1994 BI.setSuccessor(1, TrueDest);
2001 void InstCombiner::removeFromWorkList(Instruction *I) {
2002 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2006 bool InstCombiner::runOnFunction(Function &F) {
2007 bool Changed = false;
2008 TD = &getAnalysis<TargetData>();
2010 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2012 while (!WorkList.empty()) {
2013 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2014 WorkList.pop_back();
2016 // Check to see if we can DCE or ConstantPropagate the instruction...
2017 // Check to see if we can DIE the instruction...
2018 if (isInstructionTriviallyDead(I)) {
2019 // Add operands to the worklist...
2020 if (I->getNumOperands() < 4)
2021 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2022 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2023 WorkList.push_back(Op);
2026 I->getParent()->getInstList().erase(I);
2027 removeFromWorkList(I);
2031 // Instruction isn't dead, see if we can constant propagate it...
2032 if (Constant *C = ConstantFoldInstruction(I)) {
2033 // Add operands to the worklist...
2034 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2035 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2036 WorkList.push_back(Op);
2037 ReplaceInstUsesWith(*I, C);
2040 I->getParent()->getInstList().erase(I);
2041 removeFromWorkList(I);
2045 // Now that we have an instruction, try combining it to simplify it...
2046 if (Instruction *Result = visit(*I)) {
2048 // Should we replace the old instruction with a new one?
2050 // Instructions can end up on the worklist more than once. Make sure
2051 // we do not process an instruction that has been deleted.
2052 removeFromWorkList(I);
2054 // Move the name to the new instruction first...
2055 std::string OldName = I->getName(); I->setName("");
2056 Result->setName(OldName);
2058 // Insert the new instruction into the basic block...
2059 BasicBlock *InstParent = I->getParent();
2060 InstParent->getInstList().insert(I, Result);
2062 // Everything uses the new instruction now...
2063 I->replaceAllUsesWith(Result);
2065 // Erase the old instruction.
2066 InstParent->getInstList().erase(I);
2068 BasicBlock::iterator II = I;
2070 // If the instruction was modified, it's possible that it is now dead.
2071 // if so, remove it.
2072 if (dceInstruction(II)) {
2073 // Instructions may end up in the worklist more than once. Erase them
2075 removeFromWorkList(I);
2081 WorkList.push_back(Result);
2082 AddUsesToWorkList(*Result);
2091 Pass *createInstructionCombiningPass() {
2092 return new InstCombiner();