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 // Swap the two operands of the subexpr...
517 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
518 Op1I->setOperand(0, IIOp1);
519 Op1I->setOperand(1, IIOp0);
521 // Create the new top level add instruction...
522 return BinaryOperator::create(Instruction::Add, Op0, Op1);
525 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
527 if (Op1I->getOpcode() == Instruction::And &&
528 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
529 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
531 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
532 return BinaryOperator::create(Instruction::And, Op0, NewNot);
535 // X - X*C --> X * (1-C)
536 if (dyn_castFoldableMul(Op1I) == Op0) {
538 ConstantExpr::get(Instruction::Sub,
539 ConstantInt::get(I.getType(), 1),
540 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
541 assert(CP1 && "Couldn't constant fold 1-C?");
542 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
546 // X*C - X --> X * (C-1)
547 if (dyn_castFoldableMul(Op0) == Op1) {
549 ConstantExpr::get(Instruction::Sub,
550 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
551 ConstantInt::get(I.getType(), 1));
552 assert(CP1 && "Couldn't constant fold C - 1?");
553 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
559 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
560 bool Changed = SimplifyCommutative(I);
561 Value *Op0 = I.getOperand(0);
563 // Simplify mul instructions with a constant RHS...
564 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
565 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
567 // ((X << C1)*C2) == (X * (C2 << C1))
568 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
569 if (SI->getOpcode() == Instruction::Shl)
570 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
571 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
572 ConstantExpr::get(Instruction::Shl, CI, ShOp));
574 if (CI->isNullValue())
575 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
576 if (CI->equalsInt(1)) // X * 1 == X
577 return ReplaceInstUsesWith(I, Op0);
578 if (CI->isAllOnesValue()) // X * -1 == 0 - X
579 return BinaryOperator::createNeg(Op0, I.getName());
581 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
582 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
583 return new ShiftInst(Instruction::Shl, Op0,
584 ConstantUInt::get(Type::UByteTy, C));
586 ConstantFP *Op1F = cast<ConstantFP>(Op1);
587 if (Op1F->isNullValue())
588 return ReplaceInstUsesWith(I, Op1);
590 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
591 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
592 if (Op1F->getValue() == 1.0)
593 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
597 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
598 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
599 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
601 return Changed ? &I : 0;
604 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
606 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
607 if (RHS->equalsInt(1))
608 return ReplaceInstUsesWith(I, I.getOperand(0));
610 // Check to see if this is an unsigned division with an exact power of 2,
611 // if so, convert to a right shift.
612 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
613 if (uint64_t Val = C->getValue()) // Don't break X / 0
614 if (uint64_t C = Log2(Val))
615 return new ShiftInst(Instruction::Shr, I.getOperand(0),
616 ConstantUInt::get(Type::UByteTy, C));
619 // 0 / X == 0, we don't need to preserve faults!
620 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
621 if (LHS->equalsInt(0))
622 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
628 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
629 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
630 if (RHS->equalsInt(1)) // X % 1 == 0
631 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
633 // Check to see if this is an unsigned remainder with an exact power of 2,
634 // if so, convert to a bitwise and.
635 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
636 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
638 return BinaryOperator::create(Instruction::And, I.getOperand(0),
639 ConstantUInt::get(I.getType(), Val-1));
642 // 0 % X == 0, we don't need to preserve faults!
643 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
644 if (LHS->equalsInt(0))
645 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
650 // isMaxValueMinusOne - return true if this is Max-1
651 static bool isMaxValueMinusOne(const ConstantInt *C) {
652 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
653 // Calculate -1 casted to the right type...
654 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
655 uint64_t Val = ~0ULL; // All ones
656 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
657 return CU->getValue() == Val-1;
660 const ConstantSInt *CS = cast<ConstantSInt>(C);
662 // Calculate 0111111111..11111
663 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
664 int64_t Val = INT64_MAX; // All ones
665 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
666 return CS->getValue() == Val-1;
669 // isMinValuePlusOne - return true if this is Min+1
670 static bool isMinValuePlusOne(const ConstantInt *C) {
671 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
672 return CU->getValue() == 1;
674 const ConstantSInt *CS = cast<ConstantSInt>(C);
676 // Calculate 1111111111000000000000
677 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
678 int64_t Val = -1; // All ones
679 Val <<= TypeBits-1; // Shift over to the right spot
680 return CS->getValue() == Val+1;
683 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
684 /// are carefully arranged to allow folding of expressions such as:
686 /// (A < B) | (A > B) --> (A != B)
688 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
689 /// represents that the comparison is true if A == B, and bit value '1' is true
692 static unsigned getSetCondCode(const SetCondInst *SCI) {
693 switch (SCI->getOpcode()) {
695 case Instruction::SetGT: return 1;
696 case Instruction::SetEQ: return 2;
697 case Instruction::SetGE: return 3;
698 case Instruction::SetLT: return 4;
699 case Instruction::SetNE: return 5;
700 case Instruction::SetLE: return 6;
703 assert(0 && "Invalid SetCC opcode!");
708 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
709 /// opcode and two operands into either a constant true or false, or a brand new
710 /// SetCC instruction.
711 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
713 case 0: return ConstantBool::False;
714 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
715 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
716 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
717 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
718 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
719 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
720 case 7: return ConstantBool::True;
721 default: assert(0 && "Illegal SetCCCode!"); return 0;
725 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
726 struct FoldSetCCLogical {
729 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
730 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
731 bool shouldApply(Value *V) const {
732 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
733 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
734 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
737 Instruction *apply(BinaryOperator &Log) const {
738 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
739 if (SCI->getOperand(0) != LHS) {
740 assert(SCI->getOperand(1) == LHS);
741 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
744 unsigned LHSCode = getSetCondCode(SCI);
745 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
747 switch (Log.getOpcode()) {
748 case Instruction::And: Code = LHSCode & RHSCode; break;
749 case Instruction::Or: Code = LHSCode | RHSCode; break;
750 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
751 default: assert(0 && "Illegal logical opcode!"); return 0;
754 Value *RV = getSetCCValue(Code, LHS, RHS);
755 if (Instruction *I = dyn_cast<Instruction>(RV))
757 // Otherwise, it's a constant boolean value...
758 return IC.ReplaceInstUsesWith(Log, RV);
763 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
764 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
765 // guaranteed to be either a shift instruction or a binary operator.
766 Instruction *InstCombiner::OptAndOp(Instruction *Op,
767 ConstantIntegral *OpRHS,
768 ConstantIntegral *AndRHS,
769 BinaryOperator &TheAnd) {
770 Value *X = Op->getOperand(0);
771 Constant *Together = 0;
772 if (!isa<ShiftInst>(Op))
773 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
775 switch (Op->getOpcode()) {
776 case Instruction::Xor:
777 if (Together->isNullValue()) {
778 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
779 return BinaryOperator::create(Instruction::And, X, AndRHS);
780 } else if (Op->hasOneUse()) {
781 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
782 std::string OpName = Op->getName(); Op->setName("");
783 Instruction *And = BinaryOperator::create(Instruction::And,
785 InsertNewInstBefore(And, TheAnd);
786 return BinaryOperator::create(Instruction::Xor, And, Together);
789 case Instruction::Or:
790 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
791 if (Together->isNullValue())
792 return BinaryOperator::create(Instruction::And, X, AndRHS);
794 if (Together == AndRHS) // (X | C) & C --> C
795 return ReplaceInstUsesWith(TheAnd, AndRHS);
797 if (Op->hasOneUse() && Together != OpRHS) {
798 // (X | C1) & C2 --> (X | (C1&C2)) & C2
799 std::string Op0Name = Op->getName(); Op->setName("");
800 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
802 InsertNewInstBefore(Or, TheAnd);
803 return BinaryOperator::create(Instruction::And, Or, AndRHS);
807 case Instruction::Add:
808 if (Op->hasOneUse()) {
809 // Adding a one to a single bit bit-field should be turned into an XOR
810 // of the bit. First thing to check is to see if this AND is with a
811 // single bit constant.
812 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
814 // Clear bits that are not part of the constant.
815 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
817 // If there is only one bit set...
818 if ((AndRHSV & (AndRHSV-1)) == 0) {
819 // Ok, at this point, we know that we are masking the result of the
820 // ADD down to exactly one bit. If the constant we are adding has
821 // no bits set below this bit, then we can eliminate the ADD.
822 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
824 // Check to see if any bits below the one bit set in AndRHSV are set.
825 if ((AddRHS & (AndRHSV-1)) == 0) {
826 // If not, the only thing that can effect the output of the AND is
827 // the bit specified by AndRHSV. If that bit is set, the effect of
828 // the XOR is to toggle the bit. If it is clear, then the ADD has
830 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
831 TheAnd.setOperand(0, X);
834 std::string Name = Op->getName(); Op->setName("");
835 // Pull the XOR out of the AND.
836 Instruction *NewAnd =
837 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
838 InsertNewInstBefore(NewAnd, TheAnd);
839 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
846 case Instruction::Shl: {
847 // We know that the AND will not produce any of the bits shifted in, so if
848 // the anded constant includes them, clear them now!
850 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
851 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
852 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
854 TheAnd.setOperand(1, CI);
859 case Instruction::Shr:
860 // We know that the AND will not produce any of the bits shifted in, so if
861 // the anded constant includes them, clear them now! This only applies to
862 // unsigned shifts, because a signed shr may bring in set bits!
864 if (AndRHS->getType()->isUnsigned()) {
865 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
866 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
867 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
869 TheAnd.setOperand(1, CI);
879 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
880 bool Changed = SimplifyCommutative(I);
881 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
883 // and X, X = X and X, 0 == 0
884 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
885 return ReplaceInstUsesWith(I, Op1);
888 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
889 if (RHS->isAllOnesValue())
890 return ReplaceInstUsesWith(I, Op0);
892 // Optimize a variety of ((val OP C1) & C2) combinations...
893 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
894 Instruction *Op0I = cast<Instruction>(Op0);
895 Value *X = Op0I->getOperand(0);
896 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
897 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
902 Value *Op0NotVal = dyn_castNotVal(Op0);
903 Value *Op1NotVal = dyn_castNotVal(Op1);
905 // (~A & ~B) == (~(A | B)) - Demorgan's Law
906 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
907 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
908 Op1NotVal,I.getName()+".demorgan");
909 InsertNewInstBefore(Or, I);
910 return BinaryOperator::createNot(Or);
913 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
914 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
916 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
917 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
918 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
921 return Changed ? &I : 0;
926 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
927 bool Changed = SimplifyCommutative(I);
928 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
930 // or X, X = X or X, 0 == X
931 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
932 return ReplaceInstUsesWith(I, Op0);
935 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
936 if (RHS->isAllOnesValue())
937 return ReplaceInstUsesWith(I, Op1);
939 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
940 // (X & C1) | C2 --> (X | C2) & (C1|C2)
941 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
942 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
943 std::string Op0Name = Op0I->getName(); Op0I->setName("");
944 Instruction *Or = BinaryOperator::create(Instruction::Or,
945 Op0I->getOperand(0), RHS,
947 InsertNewInstBefore(Or, I);
948 return BinaryOperator::create(Instruction::And, Or,
949 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
952 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
953 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
954 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
955 std::string Op0Name = Op0I->getName(); Op0I->setName("");
956 Instruction *Or = BinaryOperator::create(Instruction::Or,
957 Op0I->getOperand(0), RHS,
959 InsertNewInstBefore(Or, I);
960 return BinaryOperator::create(Instruction::Xor, Or,
961 ConstantExpr::get(Instruction::And, Op0CI,
967 // (A & C1)|(A & C2) == A & (C1|C2)
968 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
969 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
970 if (LHS->getOperand(0) == RHS->getOperand(0))
971 if (Constant *C0 = dyn_castMaskingAnd(LHS))
972 if (Constant *C1 = dyn_castMaskingAnd(RHS))
973 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
974 ConstantExpr::get(Instruction::Or, C0, C1));
976 Value *Op0NotVal = dyn_castNotVal(Op0);
977 Value *Op1NotVal = dyn_castNotVal(Op1);
979 if (Op1 == Op0NotVal) // ~A | A == -1
980 return ReplaceInstUsesWith(I,
981 ConstantIntegral::getAllOnesValue(I.getType()));
983 if (Op0 == Op1NotVal) // A | ~A == -1
984 return ReplaceInstUsesWith(I,
985 ConstantIntegral::getAllOnesValue(I.getType()));
987 // (~A | ~B) == (~(A & B)) - Demorgan's Law
988 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
989 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
990 Op1NotVal,I.getName()+".demorgan",
992 WorkList.push_back(And);
993 return BinaryOperator::createNot(And);
996 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
997 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
998 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1001 return Changed ? &I : 0;
1006 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1007 bool Changed = SimplifyCommutative(I);
1008 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1012 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1014 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1016 if (RHS->isNullValue())
1017 return ReplaceInstUsesWith(I, Op0);
1019 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1020 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1021 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1022 if (RHS == ConstantBool::True && SCI->hasOneUse())
1023 return new SetCondInst(SCI->getInverseCondition(),
1024 SCI->getOperand(0), SCI->getOperand(1));
1026 // ~(c-X) == X-c-1 == X+(-c-1)
1027 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1028 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1029 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1030 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1031 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1032 ConstantInt::get(I.getType(), 1));
1033 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1037 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1038 switch (Op0I->getOpcode()) {
1039 case Instruction::Add:
1040 // ~(X-c) --> (-c-1)-X
1041 if (RHS->isAllOnesValue()) {
1042 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1043 Constant::getNullValue(Op0CI->getType()), Op0CI);
1044 return BinaryOperator::create(Instruction::Sub,
1045 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1046 ConstantInt::get(I.getType(), 1)),
1047 Op0I->getOperand(0));
1050 case Instruction::And:
1051 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1052 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1053 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1055 case Instruction::Or:
1056 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1057 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1058 return BinaryOperator::create(Instruction::And, Op0,
1066 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1068 return ReplaceInstUsesWith(I,
1069 ConstantIntegral::getAllOnesValue(I.getType()));
1071 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1073 return ReplaceInstUsesWith(I,
1074 ConstantIntegral::getAllOnesValue(I.getType()));
1076 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1077 if (Op1I->getOpcode() == Instruction::Or)
1078 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1079 cast<BinaryOperator>(Op1I)->swapOperands();
1081 std::swap(Op0, Op1);
1082 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1084 std::swap(Op0, Op1);
1087 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1088 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1089 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1090 cast<BinaryOperator>(Op0I)->swapOperands();
1091 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1092 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1093 WorkList.push_back(cast<Instruction>(NotB));
1094 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1099 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1100 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1101 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1102 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1103 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1105 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1106 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1107 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1110 return Changed ? &I : 0;
1113 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1114 static Constant *AddOne(ConstantInt *C) {
1115 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1116 ConstantInt::get(C->getType(), 1));
1117 assert(Result && "Constant folding integer addition failed!");
1120 static Constant *SubOne(ConstantInt *C) {
1121 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1122 ConstantInt::get(C->getType(), 1));
1123 assert(Result && "Constant folding integer addition failed!");
1127 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1128 // true when both operands are equal...
1130 static bool isTrueWhenEqual(Instruction &I) {
1131 return I.getOpcode() == Instruction::SetEQ ||
1132 I.getOpcode() == Instruction::SetGE ||
1133 I.getOpcode() == Instruction::SetLE;
1136 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1137 bool Changed = SimplifyCommutative(I);
1138 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1139 const Type *Ty = Op0->getType();
1143 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1145 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1146 if (isa<ConstantPointerNull>(Op1) &&
1147 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1148 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1151 // setcc's with boolean values can always be turned into bitwise operations
1152 if (Ty == Type::BoolTy) {
1153 // If this is <, >, or !=, we can change this into a simple xor instruction
1154 if (!isTrueWhenEqual(I))
1155 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1157 // Otherwise we need to make a temporary intermediate instruction and insert
1158 // it into the instruction stream. This is what we are after:
1160 // seteq bool %A, %B -> ~(A^B)
1161 // setle bool %A, %B -> ~A | B
1162 // setge bool %A, %B -> A | ~B
1164 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1165 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1167 InsertNewInstBefore(Xor, I);
1168 return BinaryOperator::createNot(Xor);
1171 // Handle the setXe cases...
1172 assert(I.getOpcode() == Instruction::SetGE ||
1173 I.getOpcode() == Instruction::SetLE);
1175 if (I.getOpcode() == Instruction::SetGE)
1176 std::swap(Op0, Op1); // Change setge -> setle
1178 // Now we just have the SetLE case.
1179 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1180 InsertNewInstBefore(Not, I);
1181 return BinaryOperator::create(Instruction::Or, Not, Op1);
1184 // Check to see if we are doing one of many comparisons against constant
1185 // integers at the end of their ranges...
1187 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1188 // Simplify seteq and setne instructions...
1189 if (I.getOpcode() == Instruction::SetEQ ||
1190 I.getOpcode() == Instruction::SetNE) {
1191 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1193 // If the first operand is (and|or|xor) with a constant, and the second
1194 // operand is a constant, simplify a bit.
1195 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1196 switch (BO->getOpcode()) {
1197 case Instruction::Add:
1198 if (CI->isNullValue()) {
1199 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1200 // efficiently invertible, or if the add has just this one use.
1201 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1202 if (Value *NegVal = dyn_castNegVal(BOp1))
1203 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1204 else if (Value *NegVal = dyn_castNegVal(BOp0))
1205 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1206 else if (BO->hasOneUse()) {
1207 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1209 InsertNewInstBefore(Neg, I);
1210 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1214 case Instruction::Xor:
1215 // For the xor case, we can xor two constants together, eliminating
1216 // the explicit xor.
1217 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1218 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1219 ConstantExpr::get(Instruction::Xor, CI, BOC));
1222 case Instruction::Sub:
1223 // Replace (([sub|xor] A, B) != 0) with (A != B)
1224 if (CI->isNullValue())
1225 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1229 case Instruction::Or:
1230 // If bits are being or'd in that are not present in the constant we
1231 // are comparing against, then the comparison could never succeed!
1232 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1233 Constant *NotCI = NotConstant(CI);
1234 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1235 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1239 case Instruction::And:
1240 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1241 // If bits are being compared against that are and'd out, then the
1242 // comparison can never succeed!
1243 if (!ConstantExpr::get(Instruction::And, CI,
1244 NotConstant(BOC))->isNullValue())
1245 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1247 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1248 // to be a signed value as appropriate.
1249 if (isSignBit(BOC)) {
1250 Value *X = BO->getOperand(0);
1251 // If 'X' is not signed, insert a cast now...
1252 if (!BOC->getType()->isSigned()) {
1254 switch (BOC->getType()->getPrimitiveID()) {
1255 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1256 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1257 case Type::UIntTyID: DestTy = Type::IntTy; break;
1258 case Type::ULongTyID: DestTy = Type::LongTy; break;
1259 default: assert(0 && "Invalid unsigned integer type!"); abort();
1261 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1262 InsertNewInstBefore(NewCI, I);
1265 return new SetCondInst(isSetNE ? Instruction::SetLT :
1266 Instruction::SetGE, X,
1267 Constant::getNullValue(X->getType()));
1275 // Check to see if we are comparing against the minimum or maximum value...
1276 if (CI->isMinValue()) {
1277 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1278 return ReplaceInstUsesWith(I, ConstantBool::False);
1279 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1280 return ReplaceInstUsesWith(I, ConstantBool::True);
1281 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1282 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1283 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1284 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1286 } else if (CI->isMaxValue()) {
1287 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1288 return ReplaceInstUsesWith(I, ConstantBool::False);
1289 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1290 return ReplaceInstUsesWith(I, ConstantBool::True);
1291 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1292 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1293 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1294 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1296 // Comparing against a value really close to min or max?
1297 } else if (isMinValuePlusOne(CI)) {
1298 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1299 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1300 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1301 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1303 } else if (isMaxValueMinusOne(CI)) {
1304 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1305 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1306 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1307 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1311 // Test to see if the operands of the setcc are casted versions of other
1312 // values. If the cast can be stripped off both arguments, we do so now.
1313 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1314 Value *CastOp0 = CI->getOperand(0);
1315 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1316 !isa<Argument>(Op1) &&
1317 (I.getOpcode() == Instruction::SetEQ ||
1318 I.getOpcode() == Instruction::SetNE)) {
1319 // We keep moving the cast from the left operand over to the right
1320 // operand, where it can often be eliminated completely.
1323 // If operand #1 is a cast instruction, see if we can eliminate it as
1325 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1326 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1328 Op1 = CI2->getOperand(0);
1330 // If Op1 is a constant, we can fold the cast into the constant.
1331 if (Op1->getType() != Op0->getType())
1332 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1333 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1335 // Otherwise, cast the RHS right before the setcc
1336 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1337 InsertNewInstBefore(cast<Instruction>(Op1), I);
1339 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1342 // Handle the special case of: setcc (cast bool to X), <cst>
1343 // This comes up when you have code like
1346 // For generality, we handle any zero-extension of any operand comparison
1348 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1349 const Type *SrcTy = CastOp0->getType();
1350 const Type *DestTy = Op0->getType();
1351 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1352 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1353 // Ok, we have an expansion of operand 0 into a new type. Get the
1354 // constant value, masink off bits which are not set in the RHS. These
1355 // could be set if the destination value is signed.
1356 uint64_t ConstVal = ConstantRHS->getRawValue();
1357 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1359 // If the constant we are comparing it with has high bits set, which
1360 // don't exist in the original value, the values could never be equal,
1361 // because the source would be zero extended.
1363 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1364 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1365 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1366 switch (I.getOpcode()) {
1367 default: assert(0 && "Unknown comparison type!");
1368 case Instruction::SetEQ:
1369 return ReplaceInstUsesWith(I, ConstantBool::False);
1370 case Instruction::SetNE:
1371 return ReplaceInstUsesWith(I, ConstantBool::True);
1372 case Instruction::SetLT:
1373 case Instruction::SetLE:
1374 if (DestTy->isSigned() && HasSignBit)
1375 return ReplaceInstUsesWith(I, ConstantBool::False);
1376 return ReplaceInstUsesWith(I, ConstantBool::True);
1377 case Instruction::SetGT:
1378 case Instruction::SetGE:
1379 if (DestTy->isSigned() && HasSignBit)
1380 return ReplaceInstUsesWith(I, ConstantBool::True);
1381 return ReplaceInstUsesWith(I, ConstantBool::False);
1385 // Otherwise, we can replace the setcc with a setcc of the smaller
1387 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1388 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1392 return Changed ? &I : 0;
1397 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1398 assert(I.getOperand(1)->getType() == Type::UByteTy);
1399 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1400 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1402 // shl X, 0 == X and shr X, 0 == X
1403 // shl 0, X == 0 and shr 0, X == 0
1404 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1405 Op0 == Constant::getNullValue(Op0->getType()))
1406 return ReplaceInstUsesWith(I, Op0);
1408 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1410 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1411 if (CSI->isAllOnesValue())
1412 return ReplaceInstUsesWith(I, CSI);
1414 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1415 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1416 // of a signed value.
1418 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1419 if (CUI->getValue() >= TypeBits &&
1420 (!Op0->getType()->isSigned() || isLeftShift))
1421 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1423 // ((X*C1) << C2) == (X * (C1 << C2))
1424 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1425 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1426 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1427 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1428 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1431 // If the operand is an bitwise operator with a constant RHS, and the
1432 // shift is the only use, we can pull it out of the shift.
1433 if (Op0->hasOneUse())
1434 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1435 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1436 bool isValid = true; // Valid only for And, Or, Xor
1437 bool highBitSet = false; // Transform if high bit of constant set?
1439 switch (Op0BO->getOpcode()) {
1440 default: isValid = false; break; // Do not perform transform!
1441 case Instruction::Or:
1442 case Instruction::Xor:
1445 case Instruction::And:
1450 // If this is a signed shift right, and the high bit is modified
1451 // by the logical operation, do not perform the transformation.
1452 // The highBitSet boolean indicates the value of the high bit of
1453 // the constant which would cause it to be modified for this
1456 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1457 uint64_t Val = Op0C->getRawValue();
1458 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1462 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1464 Instruction *NewShift =
1465 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1468 InsertNewInstBefore(NewShift, I);
1470 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1475 // If this is a shift of a shift, see if we can fold the two together...
1476 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1477 if (ConstantUInt *ShiftAmt1C =
1478 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1479 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1480 unsigned ShiftAmt2 = CUI->getValue();
1482 // Check for (A << c1) << c2 and (A >> c1) >> c2
1483 if (I.getOpcode() == Op0SI->getOpcode()) {
1484 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1485 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1486 ConstantUInt::get(Type::UByteTy, Amt));
1489 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1490 // signed types, we can only support the (A >> c1) << c2 configuration,
1491 // because it can not turn an arbitrary bit of A into a sign bit.
1492 if (I.getType()->isUnsigned() || isLeftShift) {
1493 // Calculate bitmask for what gets shifted off the edge...
1494 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1496 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1498 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1501 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1502 C, Op0SI->getOperand(0)->getName()+".mask");
1503 InsertNewInstBefore(Mask, I);
1505 // Figure out what flavor of shift we should use...
1506 if (ShiftAmt1 == ShiftAmt2)
1507 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1508 else if (ShiftAmt1 < ShiftAmt2) {
1509 return new ShiftInst(I.getOpcode(), Mask,
1510 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1512 return new ShiftInst(Op0SI->getOpcode(), Mask,
1513 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1523 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1526 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1527 const Type *DstTy) {
1529 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1530 // are identical and the bits don't get reinterpreted (for example
1531 // int->float->int would not be allowed)
1532 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1535 // Allow free casting and conversion of sizes as long as the sign doesn't
1537 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1538 unsigned SrcSize = SrcTy->getPrimitiveSize();
1539 unsigned MidSize = MidTy->getPrimitiveSize();
1540 unsigned DstSize = DstTy->getPrimitiveSize();
1542 // Cases where we are monotonically decreasing the size of the type are
1543 // always ok, regardless of what sign changes are going on.
1545 if (SrcSize >= MidSize && MidSize >= DstSize)
1548 // Cases where the source and destination type are the same, but the middle
1549 // type is bigger are noops.
1551 if (SrcSize == DstSize && MidSize > SrcSize)
1554 // If we are monotonically growing, things are more complex.
1556 if (SrcSize <= MidSize && MidSize <= DstSize) {
1557 // We have eight combinations of signedness to worry about. Here's the
1559 static const int SignTable[8] = {
1560 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1561 1, // U U U Always ok
1562 1, // U U S Always ok
1563 3, // U S U Ok iff SrcSize != MidSize
1564 3, // U S S Ok iff SrcSize != MidSize
1565 0, // S U U Never ok
1566 2, // S U S Ok iff MidSize == DstSize
1567 1, // S S U Always ok
1568 1, // S S S Always ok
1571 // Choose an action based on the current entry of the signtable that this
1572 // cast of cast refers to...
1573 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1574 switch (SignTable[Row]) {
1575 case 0: return false; // Never ok
1576 case 1: return true; // Always ok
1577 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1578 case 3: // Ok iff SrcSize != MidSize
1579 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1580 default: assert(0 && "Bad entry in sign table!");
1585 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1586 // like: short -> ushort -> uint, because this can create wrong results if
1587 // the input short is negative!
1592 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1593 if (V->getType() == Ty || isa<Constant>(V)) return false;
1594 if (const CastInst *CI = dyn_cast<CastInst>(V))
1595 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1600 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1601 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1602 /// casts that are known to not do anything...
1604 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1605 Instruction *InsertBefore) {
1606 if (V->getType() == DestTy) return V;
1607 if (Constant *C = dyn_cast<Constant>(V))
1608 return ConstantExpr::getCast(C, DestTy);
1610 CastInst *CI = new CastInst(V, DestTy, V->getName());
1611 InsertNewInstBefore(CI, *InsertBefore);
1615 // CastInst simplification
1617 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1618 Value *Src = CI.getOperand(0);
1620 // If the user is casting a value to the same type, eliminate this cast
1622 if (CI.getType() == Src->getType())
1623 return ReplaceInstUsesWith(CI, Src);
1625 // If casting the result of another cast instruction, try to eliminate this
1628 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1629 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1630 CSrc->getType(), CI.getType())) {
1631 // This instruction now refers directly to the cast's src operand. This
1632 // has a good chance of making CSrc dead.
1633 CI.setOperand(0, CSrc->getOperand(0));
1637 // If this is an A->B->A cast, and we are dealing with integral types, try
1638 // to convert this into a logical 'and' instruction.
1640 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1641 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1642 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1643 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1644 assert(CSrc->getType() != Type::ULongTy &&
1645 "Cannot have type bigger than ulong!");
1646 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1647 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1648 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1653 // If casting the result of a getelementptr instruction with no offset, turn
1654 // this into a cast of the original pointer!
1656 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1657 bool AllZeroOperands = true;
1658 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1659 if (!isa<Constant>(GEP->getOperand(i)) ||
1660 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1661 AllZeroOperands = false;
1664 if (AllZeroOperands) {
1665 CI.setOperand(0, GEP->getOperand(0));
1670 // If we are casting a malloc or alloca to a pointer to a type of the same
1671 // size, rewrite the allocation instruction to allocate the "right" type.
1673 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
1674 if (AI->hasOneUse() && !AI->isArrayAllocation())
1675 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
1676 // Get the type really allocated and the type casted to...
1677 const Type *AllocElTy = AI->getAllocatedType();
1678 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
1679 const Type *CastElTy = PTy->getElementType();
1680 unsigned CastElTySize = TD->getTypeSize(CastElTy);
1682 // If the allocation is for an even multiple of the cast type size
1683 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
1684 Value *Amt = ConstantUInt::get(Type::UIntTy,
1685 AllocElTySize/CastElTySize);
1686 std::string Name = AI->getName(); AI->setName("");
1687 AllocationInst *New;
1688 if (isa<MallocInst>(AI))
1689 New = new MallocInst(CastElTy, Amt, Name);
1691 New = new AllocaInst(CastElTy, Amt, Name);
1692 InsertNewInstBefore(New, CI);
1693 return ReplaceInstUsesWith(CI, New);
1697 // If the source value is an instruction with only this use, we can attempt to
1698 // propagate the cast into the instruction. Also, only handle integral types
1700 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1701 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
1702 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1703 const Type *DestTy = CI.getType();
1704 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1705 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1707 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1708 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1710 switch (SrcI->getOpcode()) {
1711 case Instruction::Add:
1712 case Instruction::Mul:
1713 case Instruction::And:
1714 case Instruction::Or:
1715 case Instruction::Xor:
1716 // If we are discarding information, or just changing the sign, rewrite.
1717 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1718 // Don't insert two casts if they cannot be eliminated. We allow two
1719 // casts to be inserted if the sizes are the same. This could only be
1720 // converting signedness, which is a noop.
1721 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1722 !ValueRequiresCast(Op0, DestTy)) {
1723 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1724 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1725 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1726 ->getOpcode(), Op0c, Op1c);
1730 case Instruction::Shl:
1731 // Allow changing the sign of the source operand. Do not allow changing
1732 // the size of the shift, UNLESS the shift amount is a constant. We
1733 // mush not change variable sized shifts to a smaller size, because it
1734 // is undefined to shift more bits out than exist in the value.
1735 if (DestBitSize == SrcBitSize ||
1736 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1737 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1738 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1747 // CallInst simplification
1749 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1750 return visitCallSite(&CI);
1753 // InvokeInst simplification
1755 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1756 return visitCallSite(&II);
1759 // getPromotedType - Return the specified type promoted as it would be to pass
1760 // though a va_arg area...
1761 static const Type *getPromotedType(const Type *Ty) {
1762 switch (Ty->getPrimitiveID()) {
1763 case Type::SByteTyID:
1764 case Type::ShortTyID: return Type::IntTy;
1765 case Type::UByteTyID:
1766 case Type::UShortTyID: return Type::UIntTy;
1767 case Type::FloatTyID: return Type::DoubleTy;
1772 // visitCallSite - Improvements for call and invoke instructions.
1774 Instruction *InstCombiner::visitCallSite(CallSite CS) {
1775 bool Changed = false;
1777 // If the callee is a constexpr cast of a function, attempt to move the cast
1778 // to the arguments of the call/invoke.
1779 if (transformConstExprCastCall(CS)) return 0;
1781 Value *Callee = CS.getCalledValue();
1782 const PointerType *PTy = cast<PointerType>(Callee->getType());
1783 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1784 if (FTy->isVarArg()) {
1785 // See if we can optimize any arguments passed through the varargs area of
1787 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
1788 E = CS.arg_end(); I != E; ++I)
1789 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
1790 // If this cast does not effect the value passed through the varargs
1791 // area, we can eliminate the use of the cast.
1792 Value *Op = CI->getOperand(0);
1793 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
1800 return Changed ? CS.getInstruction() : 0;
1803 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1804 // attempt to move the cast to the arguments of the call/invoke.
1806 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1807 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1808 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1809 if (CE->getOpcode() != Instruction::Cast ||
1810 !isa<ConstantPointerRef>(CE->getOperand(0)))
1812 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1813 if (!isa<Function>(CPR->getValue())) return false;
1814 Function *Callee = cast<Function>(CPR->getValue());
1815 Instruction *Caller = CS.getInstruction();
1817 // Okay, this is a cast from a function to a different type. Unless doing so
1818 // would cause a type conversion of one of our arguments, change this call to
1819 // be a direct call with arguments casted to the appropriate types.
1821 const FunctionType *FT = Callee->getFunctionType();
1822 const Type *OldRetTy = Caller->getType();
1824 if (Callee->isExternal() &&
1825 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
1826 !Caller->use_empty())
1827 return false; // Cannot transform this return value...
1829 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1830 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1832 CallSite::arg_iterator AI = CS.arg_begin();
1833 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1834 const Type *ParamTy = FT->getParamType(i);
1835 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1836 if (Callee->isExternal() && !isConvertible) return false;
1839 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1840 Callee->isExternal())
1841 return false; // Do not delete arguments unless we have a function body...
1843 // Okay, we decided that this is a safe thing to do: go ahead and start
1844 // inserting cast instructions as necessary...
1845 std::vector<Value*> Args;
1846 Args.reserve(NumActualArgs);
1848 AI = CS.arg_begin();
1849 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1850 const Type *ParamTy = FT->getParamType(i);
1851 if ((*AI)->getType() == ParamTy) {
1852 Args.push_back(*AI);
1854 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1855 InsertNewInstBefore(Cast, *Caller);
1856 Args.push_back(Cast);
1860 // If the function takes more arguments than the call was taking, add them
1862 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1863 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1865 // If we are removing arguments to the function, emit an obnoxious warning...
1866 if (FT->getNumParams() < NumActualArgs)
1867 if (!FT->isVarArg()) {
1868 std::cerr << "WARNING: While resolving call to function '"
1869 << Callee->getName() << "' arguments were dropped!\n";
1871 // Add all of the arguments in their promoted form to the arg list...
1872 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1873 const Type *PTy = getPromotedType((*AI)->getType());
1874 if (PTy != (*AI)->getType()) {
1875 // Must promote to pass through va_arg area!
1876 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1877 InsertNewInstBefore(Cast, *Caller);
1878 Args.push_back(Cast);
1880 Args.push_back(*AI);
1885 if (FT->getReturnType() == Type::VoidTy)
1886 Caller->setName(""); // Void type should not have a name...
1889 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1890 NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(),
1891 Args, Caller->getName(), Caller);
1893 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1896 // Insert a cast of the return type as necessary...
1898 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1899 if (NV->getType() != Type::VoidTy) {
1900 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1902 // If this is an invoke instruction, we should insert it after the first
1903 // non-phi, instruction in the normal successor block.
1904 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1905 BasicBlock::iterator I = II->getNormalDest()->begin();
1906 while (isa<PHINode>(I)) ++I;
1907 InsertNewInstBefore(NC, *I);
1909 // Otherwise, it's a call, just insert cast right after the call instr
1910 InsertNewInstBefore(NC, *Caller);
1912 AddUsesToWorkList(*Caller);
1914 NV = Constant::getNullValue(Caller->getType());
1918 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1919 Caller->replaceAllUsesWith(NV);
1920 Caller->getParent()->getInstList().erase(Caller);
1921 removeFromWorkList(Caller);
1927 // PHINode simplification
1929 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
1930 if (Value *V = hasConstantValue(&PN))
1931 return ReplaceInstUsesWith(PN, V);
1936 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1937 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
1938 // If so, eliminate the noop.
1939 if ((GEP.getNumOperands() == 2 &&
1940 GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
1941 GEP.getNumOperands() == 1)
1942 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
1944 // Combine Indices - If the source pointer to this getelementptr instruction
1945 // is a getelementptr instruction, combine the indices of the two
1946 // getelementptr instructions into a single instruction.
1948 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
1949 std::vector<Value *> Indices;
1951 // Can we combine the two pointer arithmetics offsets?
1952 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
1953 isa<Constant>(GEP.getOperand(1))) {
1954 // Replace: gep (gep %P, long C1), long C2, ...
1955 // With: gep %P, long (C1+C2), ...
1956 Value *Sum = ConstantExpr::get(Instruction::Add,
1957 cast<Constant>(Src->getOperand(1)),
1958 cast<Constant>(GEP.getOperand(1)));
1959 assert(Sum && "Constant folding of longs failed!?");
1960 GEP.setOperand(0, Src->getOperand(0));
1961 GEP.setOperand(1, Sum);
1962 AddUsesToWorkList(*Src); // Reduce use count of Src
1964 } else if (Src->getNumOperands() == 2) {
1965 // Replace: gep (gep %P, long B), long A, ...
1966 // With: T = long A+B; gep %P, T, ...
1968 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
1970 Src->getName()+".sum", &GEP);
1971 GEP.setOperand(0, Src->getOperand(0));
1972 GEP.setOperand(1, Sum);
1973 WorkList.push_back(cast<Instruction>(Sum));
1975 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
1976 Src->getNumOperands() != 1) {
1977 // Otherwise we can do the fold if the first index of the GEP is a zero
1978 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
1979 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
1980 } else if (Src->getOperand(Src->getNumOperands()-1) ==
1981 Constant::getNullValue(Type::LongTy)) {
1982 // If the src gep ends with a constant array index, merge this get into
1983 // it, even if we have a non-zero array index.
1984 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
1985 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
1988 if (!Indices.empty())
1989 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
1991 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
1992 // GEP of global variable. If all of the indices for this GEP are
1993 // constants, we can promote this to a constexpr instead of an instruction.
1995 // Scan for nonconstants...
1996 std::vector<Constant*> Indices;
1997 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
1998 for (; I != E && isa<Constant>(*I); ++I)
1999 Indices.push_back(cast<Constant>(*I));
2001 if (I == E) { // If they are all constants...
2003 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2005 // Replace all uses of the GEP with the new constexpr...
2006 return ReplaceInstUsesWith(GEP, CE);
2013 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2014 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2015 if (AI.isArrayAllocation()) // Check C != 1
2016 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2017 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2018 AllocationInst *New = 0;
2020 // Create and insert the replacement instruction...
2021 if (isa<MallocInst>(AI))
2022 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
2024 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2025 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
2028 // Scan to the end of the allocation instructions, to skip over a block of
2029 // allocas if possible...
2031 BasicBlock::iterator It = New;
2032 while (isa<AllocationInst>(*It)) ++It;
2034 // Now that I is pointing to the first non-allocation-inst in the block,
2035 // insert our getelementptr instruction...
2037 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
2038 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2040 // Now make everything use the getelementptr instead of the original
2042 ReplaceInstUsesWith(AI, V);
2048 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2049 Value *Op = FI.getOperand(0);
2051 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2052 if (CastInst *CI = dyn_cast<CastInst>(Op))
2053 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2054 FI.setOperand(0, CI->getOperand(0));
2062 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2063 /// constantexpr, return the constant value being addressed by the constant
2064 /// expression, or null if something is funny.
2066 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2067 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
2068 return 0; // Do not allow stepping over the value!
2070 // Loop over all of the operands, tracking down which value we are
2072 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2073 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2074 ConstantStruct *CS = cast<ConstantStruct>(C);
2075 if (CU->getValue() >= CS->getValues().size()) return 0;
2076 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2077 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2078 ConstantArray *CA = cast<ConstantArray>(C);
2079 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2080 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2086 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2087 Value *Op = LI.getOperand(0);
2088 if (LI.isVolatile()) return 0;
2090 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
2091 Op = CPR->getValue();
2093 // Instcombine load (constant global) into the value loaded...
2094 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2095 if (GV->isConstant() && !GV->isExternal())
2096 return ReplaceInstUsesWith(LI, GV->getInitializer());
2098 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2099 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2100 if (CE->getOpcode() == Instruction::GetElementPtr)
2101 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2102 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2103 if (GV->isConstant() && !GV->isExternal())
2104 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2105 return ReplaceInstUsesWith(LI, V);
2110 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2111 // Change br (not X), label True, label False to: br X, label False, True
2112 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
2113 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2114 BasicBlock *TrueDest = BI.getSuccessor(0);
2115 BasicBlock *FalseDest = BI.getSuccessor(1);
2116 // Swap Destinations and condition...
2118 BI.setSuccessor(0, FalseDest);
2119 BI.setSuccessor(1, TrueDest);
2126 void InstCombiner::removeFromWorkList(Instruction *I) {
2127 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2131 bool InstCombiner::runOnFunction(Function &F) {
2132 bool Changed = false;
2133 TD = &getAnalysis<TargetData>();
2135 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2137 while (!WorkList.empty()) {
2138 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2139 WorkList.pop_back();
2141 // Check to see if we can DCE or ConstantPropagate the instruction...
2142 // Check to see if we can DIE the instruction...
2143 if (isInstructionTriviallyDead(I)) {
2144 // Add operands to the worklist...
2145 if (I->getNumOperands() < 4)
2146 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2147 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2148 WorkList.push_back(Op);
2151 I->getParent()->getInstList().erase(I);
2152 removeFromWorkList(I);
2156 // Instruction isn't dead, see if we can constant propagate it...
2157 if (Constant *C = ConstantFoldInstruction(I)) {
2158 // Add operands to the worklist...
2159 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2160 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
2161 WorkList.push_back(Op);
2162 ReplaceInstUsesWith(*I, C);
2165 I->getParent()->getInstList().erase(I);
2166 removeFromWorkList(I);
2170 // Now that we have an instruction, try combining it to simplify it...
2171 if (Instruction *Result = visit(*I)) {
2173 // Should we replace the old instruction with a new one?
2175 // Instructions can end up on the worklist more than once. Make sure
2176 // we do not process an instruction that has been deleted.
2177 removeFromWorkList(I);
2179 // Move the name to the new instruction first...
2180 std::string OldName = I->getName(); I->setName("");
2181 Result->setName(OldName);
2183 // Insert the new instruction into the basic block...
2184 BasicBlock *InstParent = I->getParent();
2185 InstParent->getInstList().insert(I, Result);
2187 // Everything uses the new instruction now...
2188 I->replaceAllUsesWith(Result);
2190 // Erase the old instruction.
2191 InstParent->getInstList().erase(I);
2193 BasicBlock::iterator II = I;
2195 // If the instruction was modified, it's possible that it is now dead.
2196 // if so, remove it.
2197 if (dceInstruction(II)) {
2198 // Instructions may end up in the worklist more than once. Erase them
2200 removeFromWorkList(I);
2206 WorkList.push_back(Result);
2207 AddUsesToWorkList(*Result);
2216 Pass *llvm::createInstructionCombiningPass() {
2217 return new InstCombiner();