1 //===- InstructionCombining.cpp - Combine multiple instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // InstructionCombining - Combine instructions to form fewer, simple
11 // instructions. This pass does not modify the CFG This pass is where algebraic
12 // simplification happens.
14 // This pass combines things like:
20 // This is a simple worklist driven algorithm.
22 // This pass guarantees that the following canonicalizations are performed on
24 // 1. If a binary operator has a constant operand, it is moved to the RHS
25 // 2. Bitwise operators with constant operands are always grouped so that
26 // shifts are performed first, then or's, then and's, then xor's.
27 // 3. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible
28 // 4. All SetCC instructions on boolean values are replaced with logical ops
29 // 5. add X, X is represented as (X*2) => (X << 1)
30 // 6. Multiplies with a power-of-two constant argument are transformed into
32 // N. This list is incomplete
34 //===----------------------------------------------------------------------===//
36 #include "llvm/Transforms/Scalar.h"
37 #include "llvm/Instructions.h"
38 #include "llvm/Pass.h"
39 #include "llvm/Constants.h"
40 #include "llvm/DerivedTypes.h"
41 #include "llvm/GlobalVariable.h"
42 #include "llvm/Target/TargetData.h"
43 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
44 #include "llvm/Transforms/Utils/Local.h"
45 #include "llvm/Support/InstIterator.h"
46 #include "llvm/Support/InstVisitor.h"
47 #include "llvm/Support/CallSite.h"
48 #include "Support/Statistic.h"
53 Statistic<> NumCombined ("instcombine", "Number of insts combined");
54 Statistic<> NumConstProp("instcombine", "Number of constant folds");
55 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
57 class InstCombiner : public FunctionPass,
58 public InstVisitor<InstCombiner, Instruction*> {
59 // Worklist of all of the instructions that need to be simplified.
60 std::vector<Instruction*> WorkList;
63 void AddUsesToWorkList(Instruction &I) {
64 // The instruction was simplified, add all users of the instruction to
65 // the work lists because they might get more simplified now...
67 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
69 WorkList.push_back(cast<Instruction>(*UI));
72 // removeFromWorkList - remove all instances of I from the worklist.
73 void removeFromWorkList(Instruction *I);
75 virtual bool runOnFunction(Function &F);
77 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
78 AU.addRequired<TargetData>();
82 // Visitation implementation - Implement instruction combining for different
83 // instruction types. The semantics are as follows:
85 // null - No change was made
86 // I - Change was made, I is still valid, I may be dead though
87 // otherwise - Change was made, replace I with returned instruction
89 Instruction *visitAdd(BinaryOperator &I);
90 Instruction *visitSub(BinaryOperator &I);
91 Instruction *visitMul(BinaryOperator &I);
92 Instruction *visitDiv(BinaryOperator &I);
93 Instruction *visitRem(BinaryOperator &I);
94 Instruction *visitAnd(BinaryOperator &I);
95 Instruction *visitOr (BinaryOperator &I);
96 Instruction *visitXor(BinaryOperator &I);
97 Instruction *visitSetCondInst(BinaryOperator &I);
98 Instruction *visitShiftInst(ShiftInst &I);
99 Instruction *visitCastInst(CastInst &CI);
100 Instruction *visitCallInst(CallInst &CI);
101 Instruction *visitInvokeInst(InvokeInst &II);
102 Instruction *visitPHINode(PHINode &PN);
103 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
104 Instruction *visitAllocationInst(AllocationInst &AI);
105 Instruction *visitFreeInst(FreeInst &FI);
106 Instruction *visitLoadInst(LoadInst &LI);
107 Instruction *visitBranchInst(BranchInst &BI);
109 // visitInstruction - Specify what to return for unhandled instructions...
110 Instruction *visitInstruction(Instruction &I) { return 0; }
113 Instruction *visitCallSite(CallSite CS);
114 bool transformConstExprCastCall(CallSite CS);
116 // InsertNewInstBefore - insert an instruction New before instruction Old
117 // in the program. Add the new instruction to the worklist.
119 void InsertNewInstBefore(Instruction *New, Instruction &Old) {
120 assert(New && New->getParent() == 0 &&
121 "New instruction already inserted into a basic block!");
122 BasicBlock *BB = Old.getParent();
123 BB->getInstList().insert(&Old, New); // Insert inst
124 WorkList.push_back(New); // Add to worklist
128 // ReplaceInstUsesWith - This method is to be used when an instruction is
129 // found to be dead, replacable with another preexisting expression. Here
130 // we add all uses of I to the worklist, replace all uses of I with the new
131 // value, then return I, so that the inst combiner will know that I was
134 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
135 AddUsesToWorkList(I); // Add all modified instrs to worklist
136 I.replaceAllUsesWith(V);
140 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
141 /// InsertBefore instruction. This is specialized a bit to avoid inserting
142 /// casts that are known to not do anything...
144 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
145 Instruction *InsertBefore);
147 // SimplifyCommutative - This performs a few simplifications for commutative
149 bool SimplifyCommutative(BinaryOperator &I);
151 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
152 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
155 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
158 // getComplexity: Assign a complexity or rank value to LLVM Values...
159 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
160 static unsigned getComplexity(Value *V) {
161 if (isa<Instruction>(V)) {
162 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
166 if (isa<Argument>(V)) return 2;
167 return isa<Constant>(V) ? 0 : 1;
170 // isOnlyUse - Return true if this instruction will be deleted if we stop using
172 static bool isOnlyUse(Value *V) {
173 return V->hasOneUse() || isa<Constant>(V);
176 // SimplifyCommutative - This performs a few simplifications for commutative
179 // 1. Order operands such that they are listed from right (least complex) to
180 // left (most complex). This puts constants before unary operators before
183 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
184 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
186 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
187 bool Changed = false;
188 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
189 Changed = !I.swapOperands();
191 if (!I.isAssociative()) return Changed;
192 Instruction::BinaryOps Opcode = I.getOpcode();
193 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
194 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
195 if (isa<Constant>(I.getOperand(1))) {
196 Constant *Folded = ConstantExpr::get(I.getOpcode(),
197 cast<Constant>(I.getOperand(1)),
198 cast<Constant>(Op->getOperand(1)));
199 I.setOperand(0, Op->getOperand(0));
200 I.setOperand(1, Folded);
202 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
203 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
204 isOnlyUse(Op) && isOnlyUse(Op1)) {
205 Constant *C1 = cast<Constant>(Op->getOperand(1));
206 Constant *C2 = cast<Constant>(Op1->getOperand(1));
208 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
209 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
210 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
213 WorkList.push_back(New);
214 I.setOperand(0, New);
215 I.setOperand(1, Folded);
222 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
223 // if the LHS is a constant zero (which is the 'negate' form).
225 static inline Value *dyn_castNegVal(Value *V) {
226 if (BinaryOperator::isNeg(V))
227 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
229 // Constants can be considered to be negated values if they can be folded...
230 if (Constant *C = dyn_cast<Constant>(V))
231 return ConstantExpr::get(Instruction::Sub,
232 Constant::getNullValue(V->getType()), C);
236 static Constant *NotConstant(Constant *C) {
237 return ConstantExpr::get(Instruction::Xor, C,
238 ConstantIntegral::getAllOnesValue(C->getType()));
241 static inline Value *dyn_castNotVal(Value *V) {
242 if (BinaryOperator::isNot(V))
243 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
245 // Constants can be considered to be not'ed values...
246 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
247 return NotConstant(C);
251 // dyn_castFoldableMul - If this value is a multiply that can be folded into
252 // other computations (because it has a constant operand), return the
253 // non-constant operand of the multiply.
255 static inline Value *dyn_castFoldableMul(Value *V) {
256 if (V->hasOneUse() && V->getType()->isInteger())
257 if (Instruction *I = dyn_cast<Instruction>(V))
258 if (I->getOpcode() == Instruction::Mul)
259 if (isa<Constant>(I->getOperand(1)))
260 return I->getOperand(0);
264 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
265 // a constant, return the constant being anded with.
267 template<class ValueType>
268 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
269 if (Instruction *I = dyn_cast<Instruction>(V))
270 if (I->getOpcode() == Instruction::And)
271 return dyn_cast<Constant>(I->getOperand(1));
273 // If this is a constant, it acts just like we were masking with it.
274 return dyn_cast<Constant>(V);
277 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
279 static unsigned Log2(uint64_t Val) {
280 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
283 if (Val & 1) return 0; // Multiple bits set?
291 /// AssociativeOpt - Perform an optimization on an associative operator. This
292 /// function is designed to check a chain of associative operators for a
293 /// potential to apply a certain optimization. Since the optimization may be
294 /// applicable if the expression was reassociated, this checks the chain, then
295 /// reassociates the expression as necessary to expose the optimization
296 /// opportunity. This makes use of a special Functor, which must define
297 /// 'shouldApply' and 'apply' methods.
299 template<typename Functor>
300 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
301 unsigned Opcode = Root.getOpcode();
302 Value *LHS = Root.getOperand(0);
304 // Quick check, see if the immediate LHS matches...
305 if (F.shouldApply(LHS))
306 return F.apply(Root);
308 // Otherwise, if the LHS is not of the same opcode as the root, return.
309 Instruction *LHSI = dyn_cast<Instruction>(LHS);
310 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
311 // Should we apply this transform to the RHS?
312 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
314 // If not to the RHS, check to see if we should apply to the LHS...
315 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
316 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
320 // If the functor wants to apply the optimization to the RHS of LHSI,
321 // reassociate the expression from ((? op A) op B) to (? op (A op B))
323 BasicBlock *BB = Root.getParent();
324 // All of the instructions have a single use and have no side-effects,
325 // because of this, we can pull them all into the current basic block.
326 if (LHSI->getParent() != BB) {
327 // Move all of the instructions from root to LHSI into the current
329 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
330 Instruction *LastUse = &Root;
331 while (TmpLHSI->getParent() == BB) {
333 TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
336 // Loop over all of the instructions in other blocks, moving them into
338 Value *TmpLHS = TmpLHSI;
340 TmpLHSI = cast<Instruction>(TmpLHS);
341 // Remove from current block...
342 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
343 // Insert before the last instruction...
344 BB->getInstList().insert(LastUse, TmpLHSI);
345 TmpLHS = TmpLHSI->getOperand(0);
346 } while (TmpLHSI != LHSI);
349 // Now all of the instructions are in the current basic block, go ahead
350 // and perform the reassociation.
351 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
353 // First move the selected RHS to the LHS of the root...
354 Root.setOperand(0, LHSI->getOperand(1));
356 // Make what used to be the LHS of the root be the user of the root...
357 Value *ExtraOperand = TmpLHSI->getOperand(1);
358 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
359 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
360 BB->getInstList().remove(&Root); // Remove root from the BB
361 BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
363 // Now propagate the ExtraOperand down the chain of instructions until we
365 while (TmpLHSI != LHSI) {
366 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
367 Value *NextOp = NextLHSI->getOperand(1);
368 NextLHSI->setOperand(1, ExtraOperand);
370 ExtraOperand = NextOp;
373 // Now that the instructions are reassociated, have the functor perform
374 // the transformation...
375 return F.apply(Root);
378 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
384 // AddRHS - Implements: X + X --> X << 1
387 AddRHS(Value *rhs) : RHS(rhs) {}
388 bool shouldApply(Value *LHS) const { return LHS == RHS; }
389 Instruction *apply(BinaryOperator &Add) const {
390 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
391 ConstantInt::get(Type::UByteTy, 1));
395 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
397 struct AddMaskingAnd {
399 AddMaskingAnd(Constant *c) : C2(c) {}
400 bool shouldApply(Value *LHS) const {
401 if (Constant *C1 = dyn_castMaskingAnd(LHS))
402 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
405 Instruction *apply(BinaryOperator &Add) const {
406 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
413 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
414 bool Changed = SimplifyCommutative(I);
415 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
418 if (RHS == Constant::getNullValue(I.getType()))
419 return ReplaceInstUsesWith(I, LHS);
422 if (I.getType()->isInteger())
423 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
426 if (Value *V = dyn_castNegVal(LHS))
427 return BinaryOperator::create(Instruction::Sub, RHS, V);
430 if (!isa<Constant>(RHS))
431 if (Value *V = dyn_castNegVal(RHS))
432 return BinaryOperator::create(Instruction::Sub, LHS, V);
434 // X*C + X --> X * (C+1)
435 if (dyn_castFoldableMul(LHS) == RHS) {
437 ConstantExpr::get(Instruction::Add,
438 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
439 ConstantInt::get(I.getType(), 1));
440 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
443 // X + X*C --> X * (C+1)
444 if (dyn_castFoldableMul(RHS) == LHS) {
446 ConstantExpr::get(Instruction::Add,
447 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
448 ConstantInt::get(I.getType(), 1));
449 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
452 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
453 if (Constant *C2 = dyn_castMaskingAnd(RHS))
454 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
456 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
457 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
458 switch (ILHS->getOpcode()) {
459 case Instruction::Xor:
460 // ~X + C --> (C-1) - X
461 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
462 if (XorRHS->isAllOnesValue())
463 return BinaryOperator::create(Instruction::Sub,
464 ConstantExpr::get(Instruction::Sub,
465 CRHS, ConstantInt::get(I.getType(), 1)),
466 ILHS->getOperand(0));
473 return Changed ? &I : 0;
476 // isSignBit - Return true if the value represented by the constant only has the
477 // highest order bit set.
478 static bool isSignBit(ConstantInt *CI) {
479 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
480 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
483 static unsigned getTypeSizeInBits(const Type *Ty) {
484 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
487 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
488 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
490 if (Op0 == Op1) // sub X, X -> 0
491 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
493 // If this is a 'B = x-(-A)', change to B = x+A...
494 if (Value *V = dyn_castNegVal(Op1))
495 return BinaryOperator::create(Instruction::Add, Op0, V);
497 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
498 // Replace (-1 - A) with (~A)...
499 if (C->isAllOnesValue())
500 return BinaryOperator::createNot(Op1);
502 // C - ~X == X + (1+C)
503 if (BinaryOperator::isNot(Op1))
504 return BinaryOperator::create(Instruction::Add,
505 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
506 ConstantExpr::get(Instruction::Add, C,
507 ConstantInt::get(I.getType(), 1)));
510 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
511 if (Op1I->hasOneUse()) {
512 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
513 // is not used by anyone else...
515 if (Op1I->getOpcode() == Instruction::Sub &&
516 !Op1I->getType()->isFloatingPoint()) {
517 // Swap the two operands of the subexpr...
518 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
519 Op1I->setOperand(0, IIOp1);
520 Op1I->setOperand(1, IIOp0);
522 // Create the new top level add instruction...
523 return BinaryOperator::create(Instruction::Add, Op0, Op1);
526 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
528 if (Op1I->getOpcode() == Instruction::And &&
529 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
530 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
532 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
533 return BinaryOperator::create(Instruction::And, Op0, NewNot);
536 // X - X*C --> X * (1-C)
537 if (dyn_castFoldableMul(Op1I) == Op0) {
539 ConstantExpr::get(Instruction::Sub,
540 ConstantInt::get(I.getType(), 1),
541 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
542 assert(CP1 && "Couldn't constant fold 1-C?");
543 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
547 // X*C - X --> X * (C-1)
548 if (dyn_castFoldableMul(Op0) == Op1) {
550 ConstantExpr::get(Instruction::Sub,
551 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
552 ConstantInt::get(I.getType(), 1));
553 assert(CP1 && "Couldn't constant fold C - 1?");
554 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
560 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
561 bool Changed = SimplifyCommutative(I);
562 Value *Op0 = I.getOperand(0);
564 // Simplify mul instructions with a constant RHS...
565 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
566 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
568 // ((X << C1)*C2) == (X * (C2 << C1))
569 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
570 if (SI->getOpcode() == Instruction::Shl)
571 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
572 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
573 ConstantExpr::get(Instruction::Shl, CI, ShOp));
575 if (CI->isNullValue())
576 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
577 if (CI->equalsInt(1)) // X * 1 == X
578 return ReplaceInstUsesWith(I, Op0);
579 if (CI->isAllOnesValue()) // X * -1 == 0 - X
580 return BinaryOperator::createNeg(Op0, I.getName());
582 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
583 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
584 return new ShiftInst(Instruction::Shl, Op0,
585 ConstantUInt::get(Type::UByteTy, C));
587 ConstantFP *Op1F = cast<ConstantFP>(Op1);
588 if (Op1F->isNullValue())
589 return ReplaceInstUsesWith(I, Op1);
591 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
592 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
593 if (Op1F->getValue() == 1.0)
594 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
598 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
599 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
600 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
602 return Changed ? &I : 0;
605 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
607 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
608 if (RHS->equalsInt(1))
609 return ReplaceInstUsesWith(I, I.getOperand(0));
611 // Check to see if this is an unsigned division with an exact power of 2,
612 // if so, convert to a right shift.
613 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
614 if (uint64_t Val = C->getValue()) // Don't break X / 0
615 if (uint64_t C = Log2(Val))
616 return new ShiftInst(Instruction::Shr, I.getOperand(0),
617 ConstantUInt::get(Type::UByteTy, C));
620 // 0 / X == 0, we don't need to preserve faults!
621 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
622 if (LHS->equalsInt(0))
623 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
629 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
630 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
631 if (RHS->equalsInt(1)) // X % 1 == 0
632 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
634 // Check to see if this is an unsigned remainder with an exact power of 2,
635 // if so, convert to a bitwise and.
636 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
637 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
639 return BinaryOperator::create(Instruction::And, I.getOperand(0),
640 ConstantUInt::get(I.getType(), Val-1));
643 // 0 % X == 0, we don't need to preserve faults!
644 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
645 if (LHS->equalsInt(0))
646 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
651 // isMaxValueMinusOne - return true if this is Max-1
652 static bool isMaxValueMinusOne(const ConstantInt *C) {
653 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
654 // Calculate -1 casted to the right type...
655 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
656 uint64_t Val = ~0ULL; // All ones
657 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
658 return CU->getValue() == Val-1;
661 const ConstantSInt *CS = cast<ConstantSInt>(C);
663 // Calculate 0111111111..11111
664 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
665 int64_t Val = INT64_MAX; // All ones
666 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
667 return CS->getValue() == Val-1;
670 // isMinValuePlusOne - return true if this is Min+1
671 static bool isMinValuePlusOne(const ConstantInt *C) {
672 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
673 return CU->getValue() == 1;
675 const ConstantSInt *CS = cast<ConstantSInt>(C);
677 // Calculate 1111111111000000000000
678 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
679 int64_t Val = -1; // All ones
680 Val <<= TypeBits-1; // Shift over to the right spot
681 return CS->getValue() == Val+1;
684 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
685 /// are carefully arranged to allow folding of expressions such as:
687 /// (A < B) | (A > B) --> (A != B)
689 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
690 /// represents that the comparison is true if A == B, and bit value '1' is true
693 static unsigned getSetCondCode(const SetCondInst *SCI) {
694 switch (SCI->getOpcode()) {
696 case Instruction::SetGT: return 1;
697 case Instruction::SetEQ: return 2;
698 case Instruction::SetGE: return 3;
699 case Instruction::SetLT: return 4;
700 case Instruction::SetNE: return 5;
701 case Instruction::SetLE: return 6;
704 assert(0 && "Invalid SetCC opcode!");
709 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
710 /// opcode and two operands into either a constant true or false, or a brand new
711 /// SetCC instruction.
712 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
714 case 0: return ConstantBool::False;
715 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
716 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
717 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
718 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
719 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
720 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
721 case 7: return ConstantBool::True;
722 default: assert(0 && "Illegal SetCCCode!"); return 0;
726 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
727 struct FoldSetCCLogical {
730 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
731 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
732 bool shouldApply(Value *V) const {
733 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
734 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
735 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
738 Instruction *apply(BinaryOperator &Log) const {
739 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
740 if (SCI->getOperand(0) != LHS) {
741 assert(SCI->getOperand(1) == LHS);
742 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
745 unsigned LHSCode = getSetCondCode(SCI);
746 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
748 switch (Log.getOpcode()) {
749 case Instruction::And: Code = LHSCode & RHSCode; break;
750 case Instruction::Or: Code = LHSCode | RHSCode; break;
751 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
752 default: assert(0 && "Illegal logical opcode!"); return 0;
755 Value *RV = getSetCCValue(Code, LHS, RHS);
756 if (Instruction *I = dyn_cast<Instruction>(RV))
758 // Otherwise, it's a constant boolean value...
759 return IC.ReplaceInstUsesWith(Log, RV);
764 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
765 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
766 // guaranteed to be either a shift instruction or a binary operator.
767 Instruction *InstCombiner::OptAndOp(Instruction *Op,
768 ConstantIntegral *OpRHS,
769 ConstantIntegral *AndRHS,
770 BinaryOperator &TheAnd) {
771 Value *X = Op->getOperand(0);
772 Constant *Together = 0;
773 if (!isa<ShiftInst>(Op))
774 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
776 switch (Op->getOpcode()) {
777 case Instruction::Xor:
778 if (Together->isNullValue()) {
779 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
780 return BinaryOperator::create(Instruction::And, X, AndRHS);
781 } else if (Op->hasOneUse()) {
782 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
783 std::string OpName = Op->getName(); Op->setName("");
784 Instruction *And = BinaryOperator::create(Instruction::And,
786 InsertNewInstBefore(And, TheAnd);
787 return BinaryOperator::create(Instruction::Xor, And, Together);
790 case Instruction::Or:
791 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
792 if (Together->isNullValue())
793 return BinaryOperator::create(Instruction::And, X, AndRHS);
795 if (Together == AndRHS) // (X | C) & C --> C
796 return ReplaceInstUsesWith(TheAnd, AndRHS);
798 if (Op->hasOneUse() && Together != OpRHS) {
799 // (X | C1) & C2 --> (X | (C1&C2)) & C2
800 std::string Op0Name = Op->getName(); Op->setName("");
801 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
803 InsertNewInstBefore(Or, TheAnd);
804 return BinaryOperator::create(Instruction::And, Or, AndRHS);
808 case Instruction::Add:
809 if (Op->hasOneUse()) {
810 // Adding a one to a single bit bit-field should be turned into an XOR
811 // of the bit. First thing to check is to see if this AND is with a
812 // single bit constant.
813 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
815 // Clear bits that are not part of the constant.
816 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
818 // If there is only one bit set...
819 if ((AndRHSV & (AndRHSV-1)) == 0) {
820 // Ok, at this point, we know that we are masking the result of the
821 // ADD down to exactly one bit. If the constant we are adding has
822 // no bits set below this bit, then we can eliminate the ADD.
823 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
825 // Check to see if any bits below the one bit set in AndRHSV are set.
826 if ((AddRHS & (AndRHSV-1)) == 0) {
827 // If not, the only thing that can effect the output of the AND is
828 // the bit specified by AndRHSV. If that bit is set, the effect of
829 // the XOR is to toggle the bit. If it is clear, then the ADD has
831 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
832 TheAnd.setOperand(0, X);
835 std::string Name = Op->getName(); Op->setName("");
836 // Pull the XOR out of the AND.
837 Instruction *NewAnd =
838 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
839 InsertNewInstBefore(NewAnd, TheAnd);
840 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
847 case Instruction::Shl: {
848 // We know that the AND will not produce any of the bits shifted in, so if
849 // the anded constant includes them, clear them now!
851 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
852 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
853 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
855 TheAnd.setOperand(1, CI);
860 case Instruction::Shr:
861 // We know that the AND will not produce any of the bits shifted in, so if
862 // the anded constant includes them, clear them now! This only applies to
863 // unsigned shifts, because a signed shr may bring in set bits!
865 if (AndRHS->getType()->isUnsigned()) {
866 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
867 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
868 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
870 TheAnd.setOperand(1, CI);
880 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
881 bool Changed = SimplifyCommutative(I);
882 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
884 // and X, X = X and X, 0 == 0
885 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
886 return ReplaceInstUsesWith(I, Op1);
889 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
890 if (RHS->isAllOnesValue())
891 return ReplaceInstUsesWith(I, Op0);
893 // Optimize a variety of ((val OP C1) & C2) combinations...
894 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
895 Instruction *Op0I = cast<Instruction>(Op0);
896 Value *X = Op0I->getOperand(0);
897 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
898 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
903 Value *Op0NotVal = dyn_castNotVal(Op0);
904 Value *Op1NotVal = dyn_castNotVal(Op1);
906 // (~A & ~B) == (~(A | B)) - Demorgan's Law
907 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
908 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
909 Op1NotVal,I.getName()+".demorgan");
910 InsertNewInstBefore(Or, I);
911 return BinaryOperator::createNot(Or);
914 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
915 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
917 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
918 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
919 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
922 return Changed ? &I : 0;
927 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
928 bool Changed = SimplifyCommutative(I);
929 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
931 // or X, X = X or X, 0 == X
932 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
933 return ReplaceInstUsesWith(I, Op0);
936 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
937 if (RHS->isAllOnesValue())
938 return ReplaceInstUsesWith(I, Op1);
940 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
941 // (X & C1) | C2 --> (X | C2) & (C1|C2)
942 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
943 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
944 std::string Op0Name = Op0I->getName(); Op0I->setName("");
945 Instruction *Or = BinaryOperator::create(Instruction::Or,
946 Op0I->getOperand(0), RHS,
948 InsertNewInstBefore(Or, I);
949 return BinaryOperator::create(Instruction::And, Or,
950 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
953 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
954 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
955 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
956 std::string Op0Name = Op0I->getName(); Op0I->setName("");
957 Instruction *Or = BinaryOperator::create(Instruction::Or,
958 Op0I->getOperand(0), RHS,
960 InsertNewInstBefore(Or, I);
961 return BinaryOperator::create(Instruction::Xor, Or,
962 ConstantExpr::get(Instruction::And, Op0CI,
968 // (A & C1)|(A & C2) == A & (C1|C2)
969 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
970 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
971 if (LHS->getOperand(0) == RHS->getOperand(0))
972 if (Constant *C0 = dyn_castMaskingAnd(LHS))
973 if (Constant *C1 = dyn_castMaskingAnd(RHS))
974 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
975 ConstantExpr::get(Instruction::Or, C0, C1));
977 Value *Op0NotVal = dyn_castNotVal(Op0);
978 Value *Op1NotVal = dyn_castNotVal(Op1);
980 if (Op1 == Op0NotVal) // ~A | A == -1
981 return ReplaceInstUsesWith(I,
982 ConstantIntegral::getAllOnesValue(I.getType()));
984 if (Op0 == Op1NotVal) // A | ~A == -1
985 return ReplaceInstUsesWith(I,
986 ConstantIntegral::getAllOnesValue(I.getType()));
988 // (~A | ~B) == (~(A & B)) - Demorgan's Law
989 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
990 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
991 Op1NotVal,I.getName()+".demorgan",
993 WorkList.push_back(And);
994 return BinaryOperator::createNot(And);
997 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
998 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
999 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1002 return Changed ? &I : 0;
1005 // XorSelf - Implements: X ^ X --> 0
1008 XorSelf(Value *rhs) : RHS(rhs) {}
1009 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1010 Instruction *apply(BinaryOperator &Xor) const {
1016 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1017 bool Changed = SimplifyCommutative(I);
1018 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1020 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1021 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1022 assert(Result == &I && "AssociativeOpt didn't work?");
1023 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1026 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1028 if (RHS->isNullValue())
1029 return ReplaceInstUsesWith(I, Op0);
1031 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1032 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1033 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1034 if (RHS == ConstantBool::True && SCI->hasOneUse())
1035 return new SetCondInst(SCI->getInverseCondition(),
1036 SCI->getOperand(0), SCI->getOperand(1));
1038 // ~(c-X) == X-c-1 == X+(-c-1)
1039 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1040 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1041 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1042 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1043 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1044 ConstantInt::get(I.getType(), 1));
1045 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1049 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1050 switch (Op0I->getOpcode()) {
1051 case Instruction::Add:
1052 // ~(X-c) --> (-c-1)-X
1053 if (RHS->isAllOnesValue()) {
1054 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1055 Constant::getNullValue(Op0CI->getType()), Op0CI);
1056 return BinaryOperator::create(Instruction::Sub,
1057 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1058 ConstantInt::get(I.getType(), 1)),
1059 Op0I->getOperand(0));
1062 case Instruction::And:
1063 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1064 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1065 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1067 case Instruction::Or:
1068 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1069 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1070 return BinaryOperator::create(Instruction::And, Op0,
1078 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1080 return ReplaceInstUsesWith(I,
1081 ConstantIntegral::getAllOnesValue(I.getType()));
1083 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1085 return ReplaceInstUsesWith(I,
1086 ConstantIntegral::getAllOnesValue(I.getType()));
1088 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1089 if (Op1I->getOpcode() == Instruction::Or)
1090 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1091 cast<BinaryOperator>(Op1I)->swapOperands();
1093 std::swap(Op0, Op1);
1094 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1096 std::swap(Op0, Op1);
1099 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1100 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1101 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1102 cast<BinaryOperator>(Op0I)->swapOperands();
1103 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1104 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1105 WorkList.push_back(cast<Instruction>(NotB));
1106 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1111 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1112 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1113 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1114 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1115 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1117 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1118 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1119 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1122 return Changed ? &I : 0;
1125 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1126 static Constant *AddOne(ConstantInt *C) {
1127 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1128 ConstantInt::get(C->getType(), 1));
1129 assert(Result && "Constant folding integer addition failed!");
1132 static Constant *SubOne(ConstantInt *C) {
1133 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1134 ConstantInt::get(C->getType(), 1));
1135 assert(Result && "Constant folding integer addition failed!");
1139 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1140 // true when both operands are equal...
1142 static bool isTrueWhenEqual(Instruction &I) {
1143 return I.getOpcode() == Instruction::SetEQ ||
1144 I.getOpcode() == Instruction::SetGE ||
1145 I.getOpcode() == Instruction::SetLE;
1148 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1149 bool Changed = SimplifyCommutative(I);
1150 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1151 const Type *Ty = Op0->getType();
1155 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1157 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1158 if (isa<ConstantPointerNull>(Op1) &&
1159 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1160 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1163 // setcc's with boolean values can always be turned into bitwise operations
1164 if (Ty == Type::BoolTy) {
1165 // If this is <, >, or !=, we can change this into a simple xor instruction
1166 if (!isTrueWhenEqual(I))
1167 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1169 // Otherwise we need to make a temporary intermediate instruction and insert
1170 // it into the instruction stream. This is what we are after:
1172 // seteq bool %A, %B -> ~(A^B)
1173 // setle bool %A, %B -> ~A | B
1174 // setge bool %A, %B -> A | ~B
1176 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1177 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1179 InsertNewInstBefore(Xor, I);
1180 return BinaryOperator::createNot(Xor);
1183 // Handle the setXe cases...
1184 assert(I.getOpcode() == Instruction::SetGE ||
1185 I.getOpcode() == Instruction::SetLE);
1187 if (I.getOpcode() == Instruction::SetGE)
1188 std::swap(Op0, Op1); // Change setge -> setle
1190 // Now we just have the SetLE case.
1191 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1192 InsertNewInstBefore(Not, I);
1193 return BinaryOperator::create(Instruction::Or, Not, Op1);
1196 // Check to see if we are doing one of many comparisons against constant
1197 // integers at the end of their ranges...
1199 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1200 // Simplify seteq and setne instructions...
1201 if (I.getOpcode() == Instruction::SetEQ ||
1202 I.getOpcode() == Instruction::SetNE) {
1203 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1205 // If the first operand is (and|or|xor) with a constant, and the second
1206 // operand is a constant, simplify a bit.
1207 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1208 switch (BO->getOpcode()) {
1209 case Instruction::Add:
1210 if (CI->isNullValue()) {
1211 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1212 // efficiently invertible, or if the add has just this one use.
1213 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1214 if (Value *NegVal = dyn_castNegVal(BOp1))
1215 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1216 else if (Value *NegVal = dyn_castNegVal(BOp0))
1217 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1218 else if (BO->hasOneUse()) {
1219 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1221 InsertNewInstBefore(Neg, I);
1222 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1226 case Instruction::Xor:
1227 // For the xor case, we can xor two constants together, eliminating
1228 // the explicit xor.
1229 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1230 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1231 ConstantExpr::get(Instruction::Xor, CI, BOC));
1234 case Instruction::Sub:
1235 // Replace (([sub|xor] A, B) != 0) with (A != B)
1236 if (CI->isNullValue())
1237 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1241 case Instruction::Or:
1242 // If bits are being or'd in that are not present in the constant we
1243 // are comparing against, then the comparison could never succeed!
1244 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1245 Constant *NotCI = NotConstant(CI);
1246 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1247 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1251 case Instruction::And:
1252 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1253 // If bits are being compared against that are and'd out, then the
1254 // comparison can never succeed!
1255 if (!ConstantExpr::get(Instruction::And, CI,
1256 NotConstant(BOC))->isNullValue())
1257 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1259 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1260 // to be a signed value as appropriate.
1261 if (isSignBit(BOC)) {
1262 Value *X = BO->getOperand(0);
1263 // If 'X' is not signed, insert a cast now...
1264 if (!BOC->getType()->isSigned()) {
1266 switch (BOC->getType()->getPrimitiveID()) {
1267 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1268 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1269 case Type::UIntTyID: DestTy = Type::IntTy; break;
1270 case Type::ULongTyID: DestTy = Type::LongTy; break;
1271 default: assert(0 && "Invalid unsigned integer type!"); abort();
1273 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1274 InsertNewInstBefore(NewCI, I);
1277 return new SetCondInst(isSetNE ? Instruction::SetLT :
1278 Instruction::SetGE, X,
1279 Constant::getNullValue(X->getType()));
1287 // Check to see if we are comparing against the minimum or maximum value...
1288 if (CI->isMinValue()) {
1289 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1290 return ReplaceInstUsesWith(I, ConstantBool::False);
1291 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1292 return ReplaceInstUsesWith(I, ConstantBool::True);
1293 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1294 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1295 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1296 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1298 } else if (CI->isMaxValue()) {
1299 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1300 return ReplaceInstUsesWith(I, ConstantBool::False);
1301 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1302 return ReplaceInstUsesWith(I, ConstantBool::True);
1303 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1304 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1305 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1306 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1308 // Comparing against a value really close to min or max?
1309 } else if (isMinValuePlusOne(CI)) {
1310 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1311 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1312 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1313 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1315 } else if (isMaxValueMinusOne(CI)) {
1316 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1317 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1318 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1319 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1323 // Test to see if the operands of the setcc are casted versions of other
1324 // values. If the cast can be stripped off both arguments, we do so now.
1325 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1326 Value *CastOp0 = CI->getOperand(0);
1327 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1328 !isa<Argument>(Op1) &&
1329 (I.getOpcode() == Instruction::SetEQ ||
1330 I.getOpcode() == Instruction::SetNE)) {
1331 // We keep moving the cast from the left operand over to the right
1332 // operand, where it can often be eliminated completely.
1335 // If operand #1 is a cast instruction, see if we can eliminate it as
1337 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1338 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1340 Op1 = CI2->getOperand(0);
1342 // If Op1 is a constant, we can fold the cast into the constant.
1343 if (Op1->getType() != Op0->getType())
1344 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1345 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1347 // Otherwise, cast the RHS right before the setcc
1348 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1349 InsertNewInstBefore(cast<Instruction>(Op1), I);
1351 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1354 // Handle the special case of: setcc (cast bool to X), <cst>
1355 // This comes up when you have code like
1358 // For generality, we handle any zero-extension of any operand comparison
1360 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1361 const Type *SrcTy = CastOp0->getType();
1362 const Type *DestTy = Op0->getType();
1363 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1364 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1365 // Ok, we have an expansion of operand 0 into a new type. Get the
1366 // constant value, masink off bits which are not set in the RHS. These
1367 // could be set if the destination value is signed.
1368 uint64_t ConstVal = ConstantRHS->getRawValue();
1369 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1371 // If the constant we are comparing it with has high bits set, which
1372 // don't exist in the original value, the values could never be equal,
1373 // because the source would be zero extended.
1375 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1376 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1377 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1378 switch (I.getOpcode()) {
1379 default: assert(0 && "Unknown comparison type!");
1380 case Instruction::SetEQ:
1381 return ReplaceInstUsesWith(I, ConstantBool::False);
1382 case Instruction::SetNE:
1383 return ReplaceInstUsesWith(I, ConstantBool::True);
1384 case Instruction::SetLT:
1385 case Instruction::SetLE:
1386 if (DestTy->isSigned() && HasSignBit)
1387 return ReplaceInstUsesWith(I, ConstantBool::False);
1388 return ReplaceInstUsesWith(I, ConstantBool::True);
1389 case Instruction::SetGT:
1390 case Instruction::SetGE:
1391 if (DestTy->isSigned() && HasSignBit)
1392 return ReplaceInstUsesWith(I, ConstantBool::True);
1393 return ReplaceInstUsesWith(I, ConstantBool::False);
1397 // Otherwise, we can replace the setcc with a setcc of the smaller
1399 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1400 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1404 return Changed ? &I : 0;
1409 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1410 assert(I.getOperand(1)->getType() == Type::UByteTy);
1411 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1412 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1414 // shl X, 0 == X and shr X, 0 == X
1415 // shl 0, X == 0 and shr 0, X == 0
1416 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1417 Op0 == Constant::getNullValue(Op0->getType()))
1418 return ReplaceInstUsesWith(I, Op0);
1420 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1422 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1423 if (CSI->isAllOnesValue())
1424 return ReplaceInstUsesWith(I, CSI);
1426 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1427 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1428 // of a signed value.
1430 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1431 if (CUI->getValue() >= TypeBits &&
1432 (!Op0->getType()->isSigned() || isLeftShift))
1433 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1435 // ((X*C1) << C2) == (X * (C1 << C2))
1436 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1437 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1438 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1439 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1440 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1443 // If the operand is an bitwise operator with a constant RHS, and the
1444 // shift is the only use, we can pull it out of the shift.
1445 if (Op0->hasOneUse())
1446 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1447 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1448 bool isValid = true; // Valid only for And, Or, Xor
1449 bool highBitSet = false; // Transform if high bit of constant set?
1451 switch (Op0BO->getOpcode()) {
1452 default: isValid = false; break; // Do not perform transform!
1453 case Instruction::Or:
1454 case Instruction::Xor:
1457 case Instruction::And:
1462 // If this is a signed shift right, and the high bit is modified
1463 // by the logical operation, do not perform the transformation.
1464 // The highBitSet boolean indicates the value of the high bit of
1465 // the constant which would cause it to be modified for this
1468 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1469 uint64_t Val = Op0C->getRawValue();
1470 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1474 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1476 Instruction *NewShift =
1477 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1480 InsertNewInstBefore(NewShift, I);
1482 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1487 // If this is a shift of a shift, see if we can fold the two together...
1488 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1489 if (ConstantUInt *ShiftAmt1C =
1490 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1491 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1492 unsigned ShiftAmt2 = CUI->getValue();
1494 // Check for (A << c1) << c2 and (A >> c1) >> c2
1495 if (I.getOpcode() == Op0SI->getOpcode()) {
1496 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1497 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1498 ConstantUInt::get(Type::UByteTy, Amt));
1501 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1502 // signed types, we can only support the (A >> c1) << c2 configuration,
1503 // because it can not turn an arbitrary bit of A into a sign bit.
1504 if (I.getType()->isUnsigned() || isLeftShift) {
1505 // Calculate bitmask for what gets shifted off the edge...
1506 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1508 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1510 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1513 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1514 C, Op0SI->getOperand(0)->getName()+".mask");
1515 InsertNewInstBefore(Mask, I);
1517 // Figure out what flavor of shift we should use...
1518 if (ShiftAmt1 == ShiftAmt2)
1519 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1520 else if (ShiftAmt1 < ShiftAmt2) {
1521 return new ShiftInst(I.getOpcode(), Mask,
1522 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1524 return new ShiftInst(Op0SI->getOpcode(), Mask,
1525 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1535 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1538 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1539 const Type *DstTy) {
1541 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1542 // are identical and the bits don't get reinterpreted (for example
1543 // int->float->int would not be allowed)
1544 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1547 // Allow free casting and conversion of sizes as long as the sign doesn't
1549 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1550 unsigned SrcSize = SrcTy->getPrimitiveSize();
1551 unsigned MidSize = MidTy->getPrimitiveSize();
1552 unsigned DstSize = DstTy->getPrimitiveSize();
1554 // Cases where we are monotonically decreasing the size of the type are
1555 // always ok, regardless of what sign changes are going on.
1557 if (SrcSize >= MidSize && MidSize >= DstSize)
1560 // Cases where the source and destination type are the same, but the middle
1561 // type is bigger are noops.
1563 if (SrcSize == DstSize && MidSize > SrcSize)
1566 // If we are monotonically growing, things are more complex.
1568 if (SrcSize <= MidSize && MidSize <= DstSize) {
1569 // We have eight combinations of signedness to worry about. Here's the
1571 static const int SignTable[8] = {
1572 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1573 1, // U U U Always ok
1574 1, // U U S Always ok
1575 3, // U S U Ok iff SrcSize != MidSize
1576 3, // U S S Ok iff SrcSize != MidSize
1577 0, // S U U Never ok
1578 2, // S U S Ok iff MidSize == DstSize
1579 1, // S S U Always ok
1580 1, // S S S Always ok
1583 // Choose an action based on the current entry of the signtable that this
1584 // cast of cast refers to...
1585 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1586 switch (SignTable[Row]) {
1587 case 0: return false; // Never ok
1588 case 1: return true; // Always ok
1589 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1590 case 3: // Ok iff SrcSize != MidSize
1591 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1592 default: assert(0 && "Bad entry in sign table!");
1597 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1598 // like: short -> ushort -> uint, because this can create wrong results if
1599 // the input short is negative!
1604 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1605 if (V->getType() == Ty || isa<Constant>(V)) return false;
1606 if (const CastInst *CI = dyn_cast<CastInst>(V))
1607 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1612 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1613 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1614 /// casts that are known to not do anything...
1616 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1617 Instruction *InsertBefore) {
1618 if (V->getType() == DestTy) return V;
1619 if (Constant *C = dyn_cast<Constant>(V))
1620 return ConstantExpr::getCast(C, DestTy);
1622 CastInst *CI = new CastInst(V, DestTy, V->getName());
1623 InsertNewInstBefore(CI, *InsertBefore);
1627 // CastInst simplification
1629 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1630 Value *Src = CI.getOperand(0);
1632 // If the user is casting a value to the same type, eliminate this cast
1634 if (CI.getType() == Src->getType())
1635 return ReplaceInstUsesWith(CI, Src);
1637 // If casting the result of another cast instruction, try to eliminate this
1640 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1641 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1642 CSrc->getType(), CI.getType())) {
1643 // This instruction now refers directly to the cast's src operand. This
1644 // has a good chance of making CSrc dead.
1645 CI.setOperand(0, CSrc->getOperand(0));
1649 // If this is an A->B->A cast, and we are dealing with integral types, try
1650 // to convert this into a logical 'and' instruction.
1652 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1653 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1654 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1655 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1656 assert(CSrc->getType() != Type::ULongTy &&
1657 "Cannot have type bigger than ulong!");
1658 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1659 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1660 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1665 // If casting the result of a getelementptr instruction with no offset, turn
1666 // this into a cast of the original pointer!
1668 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1669 bool AllZeroOperands = true;
1670 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1671 if (!isa<Constant>(GEP->getOperand(i)) ||
1672 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1673 AllZeroOperands = false;
1676 if (AllZeroOperands) {
1677 CI.setOperand(0, GEP->getOperand(0));
1682 // If we are casting a malloc or alloca to a pointer to a type of the same
1683 // size, rewrite the allocation instruction to allocate the "right" type.
1685 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1686 if (AI->hasOneUse() && !AI->isArrayAllocation())
1687 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1688 // Get the type really allocated and the type casted to...
1689 const Type *AllocElTy = AI->getAllocatedType();
1690 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1691 const Type *CastElTy = PTy->getElementType();
1692 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1694 // If the allocation is for an even multiple of the cast type size
1695 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1696 Value *Amt = ConstantUInt::get(Type::UIntTy,
1697 AllocElTySize/CastElTySize);
1698 std::string Name = AI->getName(); AI->setName("");
1699 AllocationInst *New;
1700 if (isa<MallocInst>(AI))
1701 New = new MallocInst(CastElTy, Amt, Name);
1703 New = new AllocaInst(CastElTy, Amt, Name);
1704 InsertNewInstBefore(New, CI);
1705 return ReplaceInstUsesWith(CI, New);
1709 // If the source value is an instruction with only this use, we can attempt to
1710 // propagate the cast into the instruction. Also, only handle integral types
1712 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1713 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1714 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1715 const Type *DestTy = CI.getType();
1716 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1717 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1719 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1720 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1722 switch (SrcI->getOpcode()) {
1723 case Instruction::Add:
1724 case Instruction::Mul:
1725 case Instruction::And:
1726 case Instruction::Or:
1727 case Instruction::Xor:
1728 // If we are discarding information, or just changing the sign, rewrite.
1729 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1730 // Don't insert two casts if they cannot be eliminated. We allow two
1731 // casts to be inserted if the sizes are the same. This could only be
1732 // converting signedness, which is a noop.
1733 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1734 !ValueRequiresCast(Op0, DestTy)) {
1735 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1736 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1737 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1738 ->getOpcode(), Op0c, Op1c);
1742 case Instruction::Shl:
1743 // Allow changing the sign of the source operand. Do not allow changing
1744 // the size of the shift, UNLESS the shift amount is a constant. We
1745 // mush not change variable sized shifts to a smaller size, because it
1746 // is undefined to shift more bits out than exist in the value.
1747 if (DestBitSize == SrcBitSize ||
1748 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1749 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1750 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1759 // CallInst simplification
1761 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1762 return visitCallSite(&CI);
1765 // InvokeInst simplification
1767 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1768 return visitCallSite(&II);
1771 // getPromotedType - Return the specified type promoted as it would be to pass
1772 // though a va_arg area...
1773 static const Type *getPromotedType(const Type *Ty) {
1774 switch (Ty->getPrimitiveID()) {
1775 case Type::SByteTyID:
1776 case Type::ShortTyID: return Type::IntTy;
1777 case Type::UByteTyID:
1778 case Type::UShortTyID: return Type::UIntTy;
1779 case Type::FloatTyID: return Type::DoubleTy;
1784 // visitCallSite - Improvements for call and invoke instructions.
1786 Instruction *InstCombiner::visitCallSite(CallSite CS) {
1787 bool Changed = false;
1789 // If the callee is a constexpr cast of a function, attempt to move the cast
1790 // to the arguments of the call/invoke.
1791 if (transformConstExprCastCall(CS)) return 0;
1793 Value *Callee = CS.getCalledValue();
1794 const PointerType *PTy = cast<PointerType>(Callee->getType());
1795 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1796 if (FTy->isVarArg()) {
1797 // See if we can optimize any arguments passed through the varargs area of
1799 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
1800 E = CS.arg_end(); I != E; ++I)
1801 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
1802 // If this cast does not effect the value passed through the varargs
1803 // area, we can eliminate the use of the cast.
1804 Value *Op = CI->getOperand(0);
1805 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
1812 return Changed ? CS.getInstruction() : 0;
1815 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1816 // attempt to move the cast to the arguments of the call/invoke.
1818 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1819 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1820 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1821 if (CE->getOpcode() != Instruction::Cast ||
1822 !isa<ConstantPointerRef>(CE->getOperand(0)))
1824 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1825 if (!isa<Function>(CPR->getValue())) return false;
1826 Function *Callee = cast<Function>(CPR->getValue());
1827 Instruction *Caller = CS.getInstruction();
1829 // Okay, this is a cast from a function to a different type. Unless doing so
1830 // would cause a type conversion of one of our arguments, change this call to
1831 // be a direct call with arguments casted to the appropriate types.
1833 const FunctionType *FT = Callee->getFunctionType();
1834 const Type *OldRetTy = Caller->getType();
1836 // Check to see if we are changing the return type...
1837 if (OldRetTy != FT->getReturnType()) {
1838 if (Callee->isExternal() &&
1839 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
1840 !Caller->use_empty())
1841 return false; // Cannot transform this return value...
1843 // If the callsite is an invoke instruction, and the return value is used by
1844 // a PHI node in a successor, we cannot change the return type of the call
1845 // because there is no place to put the cast instruction (without breaking
1846 // the critical edge). Bail out in this case.
1847 if (!Caller->use_empty())
1848 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
1849 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
1851 if (PHINode *PN = dyn_cast<PHINode>(*UI))
1852 if (PN->getParent() == II->getNormalDest() ||
1853 PN->getParent() == II->getUnwindDest())
1857 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1858 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1860 CallSite::arg_iterator AI = CS.arg_begin();
1861 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1862 const Type *ParamTy = FT->getParamType(i);
1863 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1864 if (Callee->isExternal() && !isConvertible) return false;
1867 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1868 Callee->isExternal())
1869 return false; // Do not delete arguments unless we have a function body...
1871 // Okay, we decided that this is a safe thing to do: go ahead and start
1872 // inserting cast instructions as necessary...
1873 std::vector<Value*> Args;
1874 Args.reserve(NumActualArgs);
1876 AI = CS.arg_begin();
1877 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1878 const Type *ParamTy = FT->getParamType(i);
1879 if ((*AI)->getType() == ParamTy) {
1880 Args.push_back(*AI);
1882 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1883 InsertNewInstBefore(Cast, *Caller);
1884 Args.push_back(Cast);
1888 // If the function takes more arguments than the call was taking, add them
1890 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1891 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1893 // If we are removing arguments to the function, emit an obnoxious warning...
1894 if (FT->getNumParams() < NumActualArgs)
1895 if (!FT->isVarArg()) {
1896 std::cerr << "WARNING: While resolving call to function '"
1897 << Callee->getName() << "' arguments were dropped!\n";
1899 // Add all of the arguments in their promoted form to the arg list...
1900 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1901 const Type *PTy = getPromotedType((*AI)->getType());
1902 if (PTy != (*AI)->getType()) {
1903 // Must promote to pass through va_arg area!
1904 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1905 InsertNewInstBefore(Cast, *Caller);
1906 Args.push_back(Cast);
1908 Args.push_back(*AI);
1913 if (FT->getReturnType() == Type::VoidTy)
1914 Caller->setName(""); // Void type should not have a name...
1917 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1918 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
1919 Args, Caller->getName(), Caller);
1921 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1924 // Insert a cast of the return type as necessary...
1926 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1927 if (NV->getType() != Type::VoidTy) {
1928 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1930 // If this is an invoke instruction, we should insert it after the first
1931 // non-phi, instruction in the normal successor block.
1932 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1933 BasicBlock::iterator I = II->getNormalDest()->begin();
1934 while (isa<PHINode>(I)) ++I;
1935 InsertNewInstBefore(NC, *I);
1937 // Otherwise, it's a call, just insert cast right after the call instr
1938 InsertNewInstBefore(NC, *Caller);
1940 AddUsesToWorkList(*Caller);
1942 NV = Constant::getNullValue(Caller->getType());
1946 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1947 Caller->replaceAllUsesWith(NV);
1948 Caller->getParent()->getInstList().erase(Caller);
1949 removeFromWorkList(Caller);
1955 // PHINode simplification
1957 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
1958 if (Value *V = hasConstantValue(&PN))
1959 return ReplaceInstUsesWith(PN, V);
1964 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1965 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
1966 // If so, eliminate the noop.
1967 if ((GEP.getNumOperands() == 2 &&
1968 GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
1969 GEP.getNumOperands() == 1)
1970 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
1972 // Combine Indices - If the source pointer to this getelementptr instruction
1973 // is a getelementptr instruction, combine the indices of the two
1974 // getelementptr instructions into a single instruction.
1976 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
1977 std::vector<Value *> Indices;
1979 // Can we combine the two pointer arithmetics offsets?
1980 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
1981 isa<Constant>(GEP.getOperand(1))) {
1982 // Replace: gep (gep %P, long C1), long C2, ...
1983 // With: gep %P, long (C1+C2), ...
1984 Value *Sum = ConstantExpr::get(Instruction::Add,
1985 cast<Constant>(Src->getOperand(1)),
1986 cast<Constant>(GEP.getOperand(1)));
1987 assert(Sum && "Constant folding of longs failed!?");
1988 GEP.setOperand(0, Src->getOperand(0));
1989 GEP.setOperand(1, Sum);
1990 AddUsesToWorkList(*Src); // Reduce use count of Src
1992 } else if (Src->getNumOperands() == 2) {
1993 // Replace: gep (gep %P, long B), long A, ...
1994 // With: T = long A+B; gep %P, T, ...
1996 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
1998 Src->getName()+".sum", &GEP);
1999 GEP.setOperand(0, Src->getOperand(0));
2000 GEP.setOperand(1, Sum);
2001 WorkList.push_back(cast<Instruction>(Sum));
2003 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
2004 Src->getNumOperands() != 1) {
2005 // Otherwise we can do the fold if the first index of the GEP is a zero
2006 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
2007 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2008 } else if (Src->getOperand(Src->getNumOperands()-1) ==
2009 Constant::getNullValue(Type::LongTy)) {
2010 // If the src gep ends with a constant array index, merge this get into
2011 // it, even if we have a non-zero array index.
2012 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
2013 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
2016 if (!Indices.empty())
2017 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
2019 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
2020 // GEP of global variable. If all of the indices for this GEP are
2021 // constants, we can promote this to a constexpr instead of an instruction.
2023 // Scan for nonconstants...
2024 std::vector<Constant*> Indices;
2025 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2026 for (; I != E && isa<Constant>(*I); ++I)
2027 Indices.push_back(cast<Constant>(*I));
2029 if (I == E) { // If they are all constants...
2031 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2033 // Replace all uses of the GEP with the new constexpr...
2034 return ReplaceInstUsesWith(GEP, CE);
2041 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2042 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2043 if (AI.isArrayAllocation()) // Check C != 1
2044 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2045 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2046 AllocationInst *New = 0;
2048 // Create and insert the replacement instruction...
2049 if (isa<MallocInst>(AI))
2050 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
2052 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2053 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
2056 // Scan to the end of the allocation instructions, to skip over a block of
2057 // allocas if possible...
2059 BasicBlock::iterator It = New;
2060 while (isa<AllocationInst>(*It)) ++It;
2062 // Now that I is pointing to the first non-allocation-inst in the block,
2063 // insert our getelementptr instruction...
2065 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
2066 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2068 // Now make everything use the getelementptr instead of the original
2070 ReplaceInstUsesWith(AI, V);
2076 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2077 Value *Op = FI.getOperand(0);
2079 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2080 if (CastInst *CI = dyn_cast<CastInst>(Op))
2081 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2082 FI.setOperand(0, CI->getOperand(0));
2090 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2091 /// constantexpr, return the constant value being addressed by the constant
2092 /// expression, or null if something is funny.
2094 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2095 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
2096 return 0; // Do not allow stepping over the value!
2098 // Loop over all of the operands, tracking down which value we are
2100 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2101 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2102 ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
2103 if (CS == 0) return 0;
2104 if (CU->getValue() >= CS->getValues().size()) return 0;
2105 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2106 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2107 ConstantArray *CA = dyn_cast<ConstantArray>(C);
2108 if (CA == 0) return 0;
2109 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2110 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2116 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2117 Value *Op = LI.getOperand(0);
2118 if (LI.isVolatile()) return 0;
2120 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2121 Op = CPR->getValue();
2123 // Instcombine load (constant global) into the value loaded...
2124 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2125 if (GV->isConstant() && !GV->isExternal())
2126 return ReplaceInstUsesWith(LI, GV->getInitializer());
2128 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2129 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2130 if (CE->getOpcode() == Instruction::GetElementPtr)
2131 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2132 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2133 if (GV->isConstant() && !GV->isExternal())
2134 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2135 return ReplaceInstUsesWith(LI, V);
2140 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2141 // Change br (not X), label True, label False to: br X, label False, True
2142 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
2143 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2144 BasicBlock *TrueDest = BI.getSuccessor(0);
2145 BasicBlock *FalseDest = BI.getSuccessor(1);
2146 // Swap Destinations and condition...
2148 BI.setSuccessor(0, FalseDest);
2149 BI.setSuccessor(1, TrueDest);
2156 void InstCombiner::removeFromWorkList(Instruction *I) {
2157 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2161 bool InstCombiner::runOnFunction(Function &F) {
2162 bool Changed = false;
2163 TD = &getAnalysis<TargetData>();
2165 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2167 while (!WorkList.empty()) {
2168 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2169 WorkList.pop_back();
2171 // Check to see if we can DCE or ConstantPropagate the instruction...
2172 // Check to see if we can DIE the instruction...
2173 if (isInstructionTriviallyDead(I)) {
2174 // Add operands to the worklist...
2175 if (I->getNumOperands() < 4)
2176 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2177 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2178 WorkList.push_back(Op);
2181 I->getParent()->getInstList().erase(I);
2182 removeFromWorkList(I);
2186 // Instruction isn't dead, see if we can constant propagate it...
2187 if (Constant *C = ConstantFoldInstruction(I)) {
2188 // Add operands to the worklist...
2189 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2190 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2191 WorkList.push_back(Op);
2192 ReplaceInstUsesWith(*I, C);
2195 I->getParent()->getInstList().erase(I);
2196 removeFromWorkList(I);
2200 // Now that we have an instruction, try combining it to simplify it...
2201 if (Instruction *Result = visit(*I)) {
2203 // Should we replace the old instruction with a new one?
2205 // Instructions can end up on the worklist more than once. Make sure
2206 // we do not process an instruction that has been deleted.
2207 removeFromWorkList(I);
2209 // Move the name to the new instruction first...
2210 std::string OldName = I->getName(); I->setName("");
2211 Result->setName(OldName);
2213 // Insert the new instruction into the basic block...
2214 BasicBlock *InstParent = I->getParent();
2215 InstParent->getInstList().insert(I, Result);
2217 // Everything uses the new instruction now...
2218 I->replaceAllUsesWith(Result);
2220 // Erase the old instruction.
2221 InstParent->getInstList().erase(I);
2223 BasicBlock::iterator II = I;
2225 // If the instruction was modified, it's possible that it is now dead.
2226 // if so, remove it.
2227 if (dceInstruction(II)) {
2228 // Instructions may end up in the worklist more than once. Erase them
2230 removeFromWorkList(I);
2236 WorkList.push_back(Result);
2237 AddUsesToWorkList(*Result);
2246 Pass *llvm::createInstructionCombiningPass() {
2247 return new InstCombiner();