1 //===- InstructionCombining.cpp - Combine multiple instructions -----------===//
3 // InstructionCombining - Combine instructions to form fewer, simple
4 // instructions. This pass does not modify the CFG This pass is where algebraic
5 // simplification happens.
7 // This pass combines things like:
13 // This is a simple worklist driven algorithm.
15 // This pass guarantees that the following canonicalizations are performed on
17 // 1. If a binary operator has a constant operand, it is moved to the RHS
18 // 2. Bitwise operators with constant operands are always grouped so that
19 // shifts are performed first, then or's, then and's, then xor's.
20 // 3. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible
21 // 4. All SetCC instructions on boolean values are replaced with logical ops
22 // 5. add X, X is represented as (X*2) => (X << 1)
23 // 6. Multiplies with a power-of-two constant argument are transformed into
25 // N. This list is incomplete
27 //===----------------------------------------------------------------------===//
29 #include "llvm/Transforms/Scalar.h"
30 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
31 #include "llvm/Transforms/Utils/Local.h"
32 #include "llvm/Instructions.h"
33 #include "llvm/Pass.h"
34 #include "llvm/Constants.h"
35 #include "llvm/ConstantHandling.h"
36 #include "llvm/DerivedTypes.h"
37 #include "llvm/GlobalVariable.h"
38 #include "llvm/Support/InstIterator.h"
39 #include "llvm/Support/InstVisitor.h"
40 #include "llvm/Support/CallSite.h"
41 #include "Support/Statistic.h"
45 Statistic<> NumCombined ("instcombine", "Number of insts combined");
46 Statistic<> NumConstProp("instcombine", "Number of constant folds");
47 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
49 class InstCombiner : public FunctionPass,
50 public InstVisitor<InstCombiner, Instruction*> {
51 // Worklist of all of the instructions that need to be simplified.
52 std::vector<Instruction*> WorkList;
54 void AddUsesToWorkList(Instruction &I) {
55 // The instruction was simplified, add all users of the instruction to
56 // the work lists because they might get more simplified now...
58 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
60 WorkList.push_back(cast<Instruction>(*UI));
63 // removeFromWorkList - remove all instances of I from the worklist.
64 void removeFromWorkList(Instruction *I);
66 virtual bool runOnFunction(Function &F);
68 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
72 // Visitation implementation - Implement instruction combining for different
73 // instruction types. The semantics are as follows:
75 // null - No change was made
76 // I - Change was made, I is still valid, I may be dead though
77 // otherwise - Change was made, replace I with returned instruction
79 Instruction *visitAdd(BinaryOperator &I);
80 Instruction *visitSub(BinaryOperator &I);
81 Instruction *visitMul(BinaryOperator &I);
82 Instruction *visitDiv(BinaryOperator &I);
83 Instruction *visitRem(BinaryOperator &I);
84 Instruction *visitAnd(BinaryOperator &I);
85 Instruction *visitOr (BinaryOperator &I);
86 Instruction *visitXor(BinaryOperator &I);
87 Instruction *visitSetCondInst(BinaryOperator &I);
88 Instruction *visitShiftInst(ShiftInst &I);
89 Instruction *visitCastInst(CastInst &CI);
90 Instruction *visitCallInst(CallInst &CI);
91 Instruction *visitInvokeInst(InvokeInst &II);
92 Instruction *visitPHINode(PHINode &PN);
93 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
94 Instruction *visitAllocationInst(AllocationInst &AI);
95 Instruction *visitLoadInst(LoadInst &LI);
96 Instruction *visitBranchInst(BranchInst &BI);
98 // visitInstruction - Specify what to return for unhandled instructions...
99 Instruction *visitInstruction(Instruction &I) { return 0; }
102 bool transformConstExprCastCall(CallSite CS);
104 // InsertNewInstBefore - insert an instruction New before instruction Old
105 // in the program. Add the new instruction to the worklist.
107 void InsertNewInstBefore(Instruction *New, Instruction &Old) {
108 assert(New && New->getParent() == 0 &&
109 "New instruction already inserted into a basic block!");
110 BasicBlock *BB = Old.getParent();
111 BB->getInstList().insert(&Old, New); // Insert inst
112 WorkList.push_back(New); // Add to worklist
116 // ReplaceInstUsesWith - This method is to be used when an instruction is
117 // found to be dead, replacable with another preexisting expression. Here
118 // we add all uses of I to the worklist, replace all uses of I with the new
119 // value, then return I, so that the inst combiner will know that I was
122 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
123 AddUsesToWorkList(I); // Add all modified instrs to worklist
124 I.replaceAllUsesWith(V);
128 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
129 /// InsertBefore instruction. This is specialized a bit to avoid inserting
130 /// casts that are known to not do anything...
132 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
133 Instruction *InsertBefore);
135 // SimplifyCommutative - This performs a few simplifications for commutative
137 bool SimplifyCommutative(BinaryOperator &I);
140 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
143 // getComplexity: Assign a complexity or rank value to LLVM Values...
144 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
145 static unsigned getComplexity(Value *V) {
146 if (isa<Instruction>(V)) {
147 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
151 if (isa<Argument>(V)) return 2;
152 return isa<Constant>(V) ? 0 : 1;
155 // isOnlyUse - Return true if this instruction will be deleted if we stop using
157 static bool isOnlyUse(Value *V) {
158 return V->use_size() == 1 || isa<Constant>(V);
161 // SimplifyCommutative - This performs a few simplifications for commutative
164 // 1. Order operands such that they are listed from right (least complex) to
165 // left (most complex). This puts constants before unary operators before
168 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
169 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
171 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
172 bool Changed = false;
173 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
174 Changed = !I.swapOperands();
176 if (!I.isAssociative()) return Changed;
177 Instruction::BinaryOps Opcode = I.getOpcode();
178 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
179 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
180 if (isa<Constant>(I.getOperand(1))) {
181 Constant *Folded = ConstantExpr::get(I.getOpcode(),
182 cast<Constant>(I.getOperand(1)),
183 cast<Constant>(Op->getOperand(1)));
184 I.setOperand(0, Op->getOperand(0));
185 I.setOperand(1, Folded);
187 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
188 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
189 isOnlyUse(Op) && isOnlyUse(Op1)) {
190 Constant *C1 = cast<Constant>(Op->getOperand(1));
191 Constant *C2 = cast<Constant>(Op1->getOperand(1));
193 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
194 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
195 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
198 WorkList.push_back(New);
199 I.setOperand(0, New);
200 I.setOperand(1, Folded);
207 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
208 // if the LHS is a constant zero (which is the 'negate' form).
210 static inline Value *dyn_castNegVal(Value *V) {
211 if (BinaryOperator::isNeg(V))
212 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
214 // Constants can be considered to be negated values if they can be folded...
215 if (Constant *C = dyn_cast<Constant>(V))
216 return ConstantExpr::get(Instruction::Sub,
217 Constant::getNullValue(V->getType()), C);
221 static inline Value *dyn_castNotVal(Value *V) {
222 if (BinaryOperator::isNot(V))
223 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
225 // Constants can be considered to be not'ed values...
226 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
227 return ConstantExpr::get(Instruction::Xor,
228 ConstantIntegral::getAllOnesValue(C->getType()),C);
232 // dyn_castFoldableMul - If this value is a multiply that can be folded into
233 // other computations (because it has a constant operand), return the
234 // non-constant operand of the multiply.
236 static inline Value *dyn_castFoldableMul(Value *V) {
237 if (V->use_size() == 1 && V->getType()->isInteger())
238 if (Instruction *I = dyn_cast<Instruction>(V))
239 if (I->getOpcode() == Instruction::Mul)
240 if (isa<Constant>(I->getOperand(1)))
241 return I->getOperand(0);
245 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
246 // a constant, return the constant being anded with.
248 template<class ValueType>
249 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
250 if (Instruction *I = dyn_cast<Instruction>(V))
251 if (I->getOpcode() == Instruction::And)
252 return dyn_cast<Constant>(I->getOperand(1));
254 // If this is a constant, it acts just like we were masking with it.
255 return dyn_cast<Constant>(V);
258 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
260 static unsigned Log2(uint64_t Val) {
261 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
264 if (Val & 1) return 0; // Multiple bits set?
272 /// AssociativeOpt - Perform an optimization on an associative operator. This
273 /// function is designed to check a chain of associative operators for a
274 /// potential to apply a certain optimization. Since the optimization may be
275 /// applicable if the expression was reassociated, this checks the chain, then
276 /// reassociates the expression as necessary to expose the optimization
277 /// opportunity. This makes use of a special Functor, which must define
278 /// 'shouldApply' and 'apply' methods.
280 template<typename Functor>
281 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
282 unsigned Opcode = Root.getOpcode();
283 Value *LHS = Root.getOperand(0);
285 // Quick check, see if the immediate LHS matches...
286 if (F.shouldApply(LHS))
287 return F.apply(Root);
289 // Otherwise, if the LHS is not of the same opcode as the root, return.
290 Instruction *LHSI = dyn_cast<Instruction>(LHS);
291 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->use_size() == 1) {
292 // Should we apply this transform to the RHS?
293 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
295 // If not to the RHS, check to see if we should apply to the LHS...
296 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
297 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
301 // If the functor wants to apply the optimization to the RHS of LHSI,
302 // reassociate the expression from ((? op A) op B) to (? op (A op B))
304 BasicBlock *BB = Root.getParent();
305 // All of the instructions have a single use and have no side-effects,
306 // because of this, we can pull them all into the current basic block.
307 if (LHSI->getParent() != BB) {
308 // Move all of the instructions from root to LHSI into the current
310 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
311 Instruction *LastUse = &Root;
312 while (TmpLHSI->getParent() == BB) {
314 TmpLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
317 // Loop over all of the instructions in other blocks, moving them into
319 Value *TmpLHS = TmpLHSI;
321 TmpLHSI = cast<Instruction>(TmpLHS);
322 // Remove from current block...
323 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
324 // Insert before the last instruction...
325 BB->getInstList().insert(LastUse, TmpLHSI);
326 TmpLHS = TmpLHSI->getOperand(0);
327 } while (TmpLHSI != LHSI);
330 // Now all of the instructions are in the current basic block, go ahead
331 // and perform the reassociation.
332 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
334 // First move the selected RHS to the LHS of the root...
335 Root.setOperand(0, LHSI->getOperand(1));
337 // Make what used to be the LHS of the root be the user of the root...
338 Value *ExtraOperand = TmpLHSI->getOperand(1);
339 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
340 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
341 BB->getInstList().remove(&Root); // Remove root from the BB
342 BB->getInstList().insert(TmpLHSI, &Root); // Insert root before TmpLHSI
344 // Now propagate the ExtraOperand down the chain of instructions until we
346 while (TmpLHSI != LHSI) {
347 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
348 Value *NextOp = NextLHSI->getOperand(1);
349 NextLHSI->setOperand(1, ExtraOperand);
351 ExtraOperand = NextOp;
354 // Now that the instructions are reassociated, have the functor perform
355 // the transformation...
356 return F.apply(Root);
359 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
365 // AddRHS - Implements: X + X --> X << 1
368 AddRHS(Value *rhs) : RHS(rhs) {}
369 bool shouldApply(Value *LHS) const { return LHS == RHS; }
370 Instruction *apply(BinaryOperator &Add) const {
371 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
372 ConstantInt::get(Type::UByteTy, 1));
376 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
378 struct AddMaskingAnd {
380 AddMaskingAnd(Constant *c) : C2(c) {}
381 bool shouldApply(Value *LHS) const {
382 if (Constant *C1 = dyn_castMaskingAnd(LHS))
383 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
386 Instruction *apply(BinaryOperator &Add) const {
387 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
394 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
395 bool Changed = SimplifyCommutative(I);
396 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
399 if (RHS == Constant::getNullValue(I.getType()))
400 return ReplaceInstUsesWith(I, LHS);
403 if (I.getType()->isInteger())
404 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
407 if (Value *V = dyn_castNegVal(LHS))
408 return BinaryOperator::create(Instruction::Sub, RHS, V);
411 if (!isa<Constant>(RHS))
412 if (Value *V = dyn_castNegVal(RHS))
413 return BinaryOperator::create(Instruction::Sub, LHS, V);
415 // X*C + X --> X * (C+1)
416 if (dyn_castFoldableMul(LHS) == RHS) {
418 ConstantExpr::get(Instruction::Add,
419 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
420 ConstantInt::get(I.getType(), 1));
421 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
424 // X + X*C --> X * (C+1)
425 if (dyn_castFoldableMul(RHS) == LHS) {
427 ConstantExpr::get(Instruction::Add,
428 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
429 ConstantInt::get(I.getType(), 1));
430 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
433 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
434 if (Constant *C2 = dyn_castMaskingAnd(RHS))
435 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
437 return Changed ? &I : 0;
440 // isSignBit - Return true if the value represented by the constant only has the
441 // highest order bit set.
442 static bool isSignBit(ConstantInt *CI) {
443 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
444 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
447 static unsigned getTypeSizeInBits(const Type *Ty) {
448 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
451 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
452 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
454 if (Op0 == Op1) // sub X, X -> 0
455 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
457 // If this is a 'B = x-(-A)', change to B = x+A...
458 if (Value *V = dyn_castNegVal(Op1))
459 return BinaryOperator::create(Instruction::Add, Op0, V);
461 // Replace (-1 - A) with (~A)...
462 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0))
463 if (C->isAllOnesValue())
464 return BinaryOperator::createNot(Op1);
466 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
467 if (Op1I->use_size() == 1) {
468 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
469 // is not used by anyone else...
471 if (Op1I->getOpcode() == Instruction::Sub) {
472 // Swap the two operands of the subexpr...
473 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
474 Op1I->setOperand(0, IIOp1);
475 Op1I->setOperand(1, IIOp0);
477 // Create the new top level add instruction...
478 return BinaryOperator::create(Instruction::Add, Op0, Op1);
481 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
483 if (Op1I->getOpcode() == Instruction::And &&
484 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
485 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
487 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
488 return BinaryOperator::create(Instruction::And, Op0, NewNot);
491 // X - X*C --> X * (1-C)
492 if (dyn_castFoldableMul(Op1I) == Op0) {
494 ConstantExpr::get(Instruction::Sub,
495 ConstantInt::get(I.getType(), 1),
496 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
497 assert(CP1 && "Couldn't constant fold 1-C?");
498 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
502 // X*C - X --> X * (C-1)
503 if (dyn_castFoldableMul(Op0) == Op1) {
505 ConstantExpr::get(Instruction::Sub,
506 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
507 ConstantInt::get(I.getType(), 1));
508 assert(CP1 && "Couldn't constant fold C - 1?");
509 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
515 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
516 bool Changed = SimplifyCommutative(I);
517 Value *Op0 = I.getOperand(0);
519 // Simplify mul instructions with a constant RHS...
520 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
521 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
523 // ((X << C1)*C2) == (X * (C2 << C1))
524 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
525 if (SI->getOpcode() == Instruction::Shl)
526 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
527 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
530 if (CI->isNullValue())
531 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
532 if (CI->equalsInt(1)) // X * 1 == X
533 return ReplaceInstUsesWith(I, Op0);
534 if (CI->isAllOnesValue()) // X * -1 == 0 - X
535 return BinaryOperator::createNeg(Op0, I.getName());
537 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
538 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
539 return new ShiftInst(Instruction::Shl, Op0,
540 ConstantUInt::get(Type::UByteTy, C));
542 ConstantFP *Op1F = cast<ConstantFP>(Op1);
543 if (Op1F->isNullValue())
544 return ReplaceInstUsesWith(I, Op1);
546 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
547 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
548 if (Op1F->getValue() == 1.0)
549 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
553 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
554 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
555 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
557 return Changed ? &I : 0;
560 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
562 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
563 if (RHS->equalsInt(1))
564 return ReplaceInstUsesWith(I, I.getOperand(0));
566 // Check to see if this is an unsigned division with an exact power of 2,
567 // if so, convert to a right shift.
568 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
569 if (uint64_t Val = C->getValue()) // Don't break X / 0
570 if (uint64_t C = Log2(Val))
571 return new ShiftInst(Instruction::Shr, I.getOperand(0),
572 ConstantUInt::get(Type::UByteTy, C));
575 // 0 / X == 0, we don't need to preserve faults!
576 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
577 if (LHS->equalsInt(0))
578 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
584 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
585 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
586 if (RHS->equalsInt(1)) // X % 1 == 0
587 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
589 // Check to see if this is an unsigned remainder with an exact power of 2,
590 // if so, convert to a bitwise and.
591 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
592 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
594 return BinaryOperator::create(Instruction::And, I.getOperand(0),
595 ConstantUInt::get(I.getType(), Val-1));
598 // 0 % X == 0, we don't need to preserve faults!
599 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
600 if (LHS->equalsInt(0))
601 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
606 // isMaxValueMinusOne - return true if this is Max-1
607 static bool isMaxValueMinusOne(const ConstantInt *C) {
608 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
609 // Calculate -1 casted to the right type...
610 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
611 uint64_t Val = ~0ULL; // All ones
612 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
613 return CU->getValue() == Val-1;
616 const ConstantSInt *CS = cast<ConstantSInt>(C);
618 // Calculate 0111111111..11111
619 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
620 int64_t Val = INT64_MAX; // All ones
621 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
622 return CS->getValue() == Val-1;
625 // isMinValuePlusOne - return true if this is Min+1
626 static bool isMinValuePlusOne(const ConstantInt *C) {
627 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
628 return CU->getValue() == 1;
630 const ConstantSInt *CS = cast<ConstantSInt>(C);
632 // Calculate 1111111111000000000000
633 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
634 int64_t Val = -1; // All ones
635 Val <<= TypeBits-1; // Shift over to the right spot
636 return CS->getValue() == Val+1;
639 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
640 /// are carefully arranged to allow folding of expressions such as:
642 /// (A < B) | (A > B) --> (A != B)
644 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
645 /// represents that the comparison is true if A == B, and bit value '1' is true
648 static unsigned getSetCondCode(const SetCondInst *SCI) {
649 switch (SCI->getOpcode()) {
651 case Instruction::SetGT: return 1;
652 case Instruction::SetEQ: return 2;
653 case Instruction::SetGE: return 3;
654 case Instruction::SetLT: return 4;
655 case Instruction::SetNE: return 5;
656 case Instruction::SetLE: return 6;
659 assert(0 && "Invalid SetCC opcode!");
664 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
665 /// opcode and two operands into either a constant true or false, or a brand new
666 /// SetCC instruction.
667 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
669 case 0: return ConstantBool::False;
670 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
671 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
672 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
673 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
674 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
675 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
676 case 7: return ConstantBool::True;
677 default: assert(0 && "Illegal SetCCCode!"); return 0;
681 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
682 struct FoldSetCCLogical {
685 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
686 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
687 bool shouldApply(Value *V) const {
688 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
689 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
690 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
693 Instruction *apply(BinaryOperator &Log) const {
694 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
695 if (SCI->getOperand(0) != LHS) {
696 assert(SCI->getOperand(1) == LHS);
697 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
700 unsigned LHSCode = getSetCondCode(SCI);
701 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
703 switch (Log.getOpcode()) {
704 case Instruction::And: Code = LHSCode & RHSCode; break;
705 case Instruction::Or: Code = LHSCode | RHSCode; break;
706 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
707 default: assert(0 && "Illegal logical opcode!");
710 Value *RV = getSetCCValue(Code, LHS, RHS);
711 if (Instruction *I = dyn_cast<Instruction>(RV))
713 // Otherwise, it's a constant boolean value...
714 return IC.ReplaceInstUsesWith(Log, RV);
720 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
721 bool Changed = SimplifyCommutative(I);
722 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
724 // and X, X = X and X, 0 == 0
725 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
726 return ReplaceInstUsesWith(I, Op1);
729 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
730 if (RHS->isAllOnesValue())
731 return ReplaceInstUsesWith(I, Op0);
733 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
734 Value *X = Op0I->getOperand(0);
735 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
736 if (Op0I->getOpcode() == Instruction::Xor) {
737 if ((*RHS & *Op0CI)->isNullValue()) {
738 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
739 return BinaryOperator::create(Instruction::And, X, RHS);
740 } else if (isOnlyUse(Op0)) {
741 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
742 std::string Op0Name = Op0I->getName(); Op0I->setName("");
743 Instruction *And = BinaryOperator::create(Instruction::And,
745 InsertNewInstBefore(And, I);
746 return BinaryOperator::create(Instruction::Xor, And, *RHS & *Op0CI);
748 } else if (Op0I->getOpcode() == Instruction::Or) {
749 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
750 if ((*RHS & *Op0CI)->isNullValue())
751 return BinaryOperator::create(Instruction::And, X, RHS);
753 Constant *Together = *RHS & *Op0CI;
754 if (Together == RHS) // (X | C) & C --> C
755 return ReplaceInstUsesWith(I, RHS);
757 if (isOnlyUse(Op0)) {
758 if (Together != Op0CI) {
759 // (X | C1) & C2 --> (X | (C1&C2)) & C2
760 std::string Op0Name = Op0I->getName(); Op0I->setName("");
761 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
763 InsertNewInstBefore(Or, I);
764 return BinaryOperator::create(Instruction::And, Or, RHS);
767 } else if (Op0I->getOpcode() == Instruction::Add &&
768 Op0I->use_size() == 1) {
769 // Adding a one to a single bit bit-field should be turned into an XOR
770 // of the bit. First thing to check is to see if this AND is with a
771 // single bit constant.
772 unsigned long long AndRHS = cast<ConstantInt>(RHS)->getRawValue();
774 // Clear bits that are not part of the constant.
775 AndRHS &= (1ULL << RHS->getType()->getPrimitiveSize()*8)-1;
777 // If there is only one bit set...
778 if ((AndRHS & (AndRHS-1)) == 0) {
779 // Ok, at this point, we know that we are masking the result of the
780 // ADD down to exactly one bit. If the constant we are adding has
781 // no bits set below this bit, then we can eliminate the ADD.
782 unsigned long long AddRHS = cast<ConstantInt>(Op0CI)->getRawValue();
784 // Check to see if any bits below the one bit set in AndRHS are set.
785 if ((AddRHS & (AndRHS-1)) == 0) {
786 // If not, the only thing that can effect the output of the AND is
787 // the bit specified by AndRHS. If that bit is set, the effect of
788 // the XOR is to toggle the bit. If it is clear, then the ADD has
790 if ((AddRHS & AndRHS) == 0) { // Bit is not set, noop
791 I.setOperand(0, Op0I->getOperand(0));
794 std::string Name = Op0I->getName(); Op0I->setName("");
795 // Pull the XOR out of the AND.
796 Instruction *NewAnd =
797 BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
799 InsertNewInstBefore(NewAnd, I);
800 return BinaryOperator::create(Instruction::Xor, NewAnd, RHS);
808 Value *Op0NotVal = dyn_castNotVal(Op0);
809 Value *Op1NotVal = dyn_castNotVal(Op1);
811 // (~A & ~B) == (~(A | B)) - Demorgan's Law
812 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
813 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
814 Op1NotVal,I.getName()+".demorgan");
815 InsertNewInstBefore(Or, I);
816 return BinaryOperator::createNot(Or);
819 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
820 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
822 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
823 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
824 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
827 return Changed ? &I : 0;
832 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
833 bool Changed = SimplifyCommutative(I);
834 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
836 // or X, X = X or X, 0 == X
837 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
838 return ReplaceInstUsesWith(I, Op0);
841 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
842 if (RHS->isAllOnesValue())
843 return ReplaceInstUsesWith(I, Op1);
845 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
846 // (X & C1) | C2 --> (X | C2) & (C1|C2)
847 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
848 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
849 std::string Op0Name = Op0I->getName(); Op0I->setName("");
850 Instruction *Or = BinaryOperator::create(Instruction::Or,
851 Op0I->getOperand(0), RHS,
853 InsertNewInstBefore(Or, I);
854 return BinaryOperator::create(Instruction::And, Or, *RHS | *Op0CI);
857 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
858 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
859 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
860 std::string Op0Name = Op0I->getName(); Op0I->setName("");
861 Instruction *Or = BinaryOperator::create(Instruction::Or,
862 Op0I->getOperand(0), RHS,
864 InsertNewInstBefore(Or, I);
865 return BinaryOperator::create(Instruction::Xor, Or, *Op0CI & *~*RHS);
870 // (A & C1)|(A & C2) == A & (C1|C2)
871 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
872 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
873 if (LHS->getOperand(0) == RHS->getOperand(0))
874 if (Constant *C0 = dyn_castMaskingAnd(LHS))
875 if (Constant *C1 = dyn_castMaskingAnd(RHS))
876 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
879 Value *Op0NotVal = dyn_castNotVal(Op0);
880 Value *Op1NotVal = dyn_castNotVal(Op1);
882 if (Op1 == Op0NotVal) // ~A | A == -1
883 return ReplaceInstUsesWith(I,
884 ConstantIntegral::getAllOnesValue(I.getType()));
886 if (Op0 == Op1NotVal) // A | ~A == -1
887 return ReplaceInstUsesWith(I,
888 ConstantIntegral::getAllOnesValue(I.getType()));
890 // (~A | ~B) == (~(A & B)) - Demorgan's Law
891 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
892 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
893 Op1NotVal,I.getName()+".demorgan",
895 WorkList.push_back(And);
896 return BinaryOperator::createNot(And);
899 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
900 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
901 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
904 return Changed ? &I : 0;
909 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
910 bool Changed = SimplifyCommutative(I);
911 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
915 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
917 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
919 if (RHS->isNullValue())
920 return ReplaceInstUsesWith(I, Op0);
922 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
923 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
924 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
925 if (RHS == ConstantBool::True && SCI->use_size() == 1)
926 return new SetCondInst(SCI->getInverseCondition(),
927 SCI->getOperand(0), SCI->getOperand(1));
929 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
930 if (Op0I->getOpcode() == Instruction::And) {
931 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
932 if ((*RHS & *Op0CI)->isNullValue())
933 return BinaryOperator::create(Instruction::Or, Op0, RHS);
934 } else if (Op0I->getOpcode() == Instruction::Or) {
935 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
936 if ((*RHS & *Op0CI) == RHS)
937 return BinaryOperator::create(Instruction::And, Op0, ~*RHS);
942 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
944 return ReplaceInstUsesWith(I,
945 ConstantIntegral::getAllOnesValue(I.getType()));
947 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
949 return ReplaceInstUsesWith(I,
950 ConstantIntegral::getAllOnesValue(I.getType()));
952 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
953 if (Op1I->getOpcode() == Instruction::Or)
954 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
955 cast<BinaryOperator>(Op1I)->swapOperands();
958 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
963 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
964 if (Op0I->getOpcode() == Instruction::Or && Op0I->use_size() == 1) {
965 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
966 cast<BinaryOperator>(Op0I)->swapOperands();
967 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
968 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
969 WorkList.push_back(cast<Instruction>(NotB));
970 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
975 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
976 if (Constant *C1 = dyn_castMaskingAnd(Op0))
977 if (Constant *C2 = dyn_castMaskingAnd(Op1))
978 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
979 return BinaryOperator::create(Instruction::Or, Op0, Op1);
981 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
982 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
983 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
986 return Changed ? &I : 0;
989 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
990 static Constant *AddOne(ConstantInt *C) {
991 Constant *Result = ConstantExpr::get(Instruction::Add, C,
992 ConstantInt::get(C->getType(), 1));
993 assert(Result && "Constant folding integer addition failed!");
996 static Constant *SubOne(ConstantInt *C) {
997 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
998 ConstantInt::get(C->getType(), 1));
999 assert(Result && "Constant folding integer addition failed!");
1003 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1004 // true when both operands are equal...
1006 static bool isTrueWhenEqual(Instruction &I) {
1007 return I.getOpcode() == Instruction::SetEQ ||
1008 I.getOpcode() == Instruction::SetGE ||
1009 I.getOpcode() == Instruction::SetLE;
1012 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1013 bool Changed = SimplifyCommutative(I);
1014 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1015 const Type *Ty = Op0->getType();
1019 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1021 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1022 if (isa<ConstantPointerNull>(Op1) &&
1023 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1024 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1027 // setcc's with boolean values can always be turned into bitwise operations
1028 if (Ty == Type::BoolTy) {
1029 // If this is <, >, or !=, we can change this into a simple xor instruction
1030 if (!isTrueWhenEqual(I))
1031 return BinaryOperator::create(Instruction::Xor, Op0, Op1, I.getName());
1033 // Otherwise we need to make a temporary intermediate instruction and insert
1034 // it into the instruction stream. This is what we are after:
1036 // seteq bool %A, %B -> ~(A^B)
1037 // setle bool %A, %B -> ~A | B
1038 // setge bool %A, %B -> A | ~B
1040 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1041 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1043 InsertNewInstBefore(Xor, I);
1044 return BinaryOperator::createNot(Xor, I.getName());
1047 // Handle the setXe cases...
1048 assert(I.getOpcode() == Instruction::SetGE ||
1049 I.getOpcode() == Instruction::SetLE);
1051 if (I.getOpcode() == Instruction::SetGE)
1052 std::swap(Op0, Op1); // Change setge -> setle
1054 // Now we just have the SetLE case.
1055 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1056 InsertNewInstBefore(Not, I);
1057 return BinaryOperator::create(Instruction::Or, Not, Op1, I.getName());
1060 // Check to see if we are doing one of many comparisons against constant
1061 // integers at the end of their ranges...
1063 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1064 // Simplify seteq and setne instructions...
1065 if (I.getOpcode() == Instruction::SetEQ ||
1066 I.getOpcode() == Instruction::SetNE) {
1067 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1069 // If the first operand is (and|or|xor) with a constant, and the second
1070 // operand is a constant, simplify a bit.
1071 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1072 switch (BO->getOpcode()) {
1073 case Instruction::Add:
1074 if (CI->isNullValue()) {
1075 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1076 // efficiently invertible, or if the add has just this one use.
1077 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1078 if (Value *NegVal = dyn_castNegVal(BOp1))
1079 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1080 else if (Value *NegVal = dyn_castNegVal(BOp0))
1081 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1082 else if (BO->use_size() == 1) {
1083 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1085 InsertNewInstBefore(Neg, I);
1086 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1090 case Instruction::Xor:
1091 // For the xor case, we can xor two constants together, eliminating
1092 // the explicit xor.
1093 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1094 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1098 case Instruction::Sub:
1099 // Replace (([sub|xor] A, B) != 0) with (A != B)
1100 if (CI->isNullValue())
1101 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1105 case Instruction::Or:
1106 // If bits are being or'd in that are not present in the constant we
1107 // are comparing against, then the comparison could never succeed!
1108 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1109 if (!(*BOC & *~*CI)->isNullValue())
1110 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1113 case Instruction::And:
1114 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1115 // If bits are being compared against that are and'd out, then the
1116 // comparison can never succeed!
1117 if (!(*CI & *~*BOC)->isNullValue())
1118 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1120 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1121 // to be a signed value as appropriate.
1122 if (isSignBit(BOC)) {
1123 Value *X = BO->getOperand(0);
1124 // If 'X' is not signed, insert a cast now...
1125 if (!BOC->getType()->isSigned()) {
1127 switch (BOC->getType()->getPrimitiveID()) {
1128 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1129 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1130 case Type::UIntTyID: DestTy = Type::IntTy; break;
1131 case Type::ULongTyID: DestTy = Type::LongTy; break;
1132 default: assert(0 && "Invalid unsigned integer type!"); abort();
1134 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1135 InsertNewInstBefore(NewCI, I);
1138 return new SetCondInst(isSetNE ? Instruction::SetLT :
1139 Instruction::SetGE, X,
1140 Constant::getNullValue(X->getType()));
1148 // Check to see if we are comparing against the minimum or maximum value...
1149 if (CI->isMinValue()) {
1150 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1151 return ReplaceInstUsesWith(I, ConstantBool::False);
1152 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1153 return ReplaceInstUsesWith(I, ConstantBool::True);
1154 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1155 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
1156 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1157 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
1159 } else if (CI->isMaxValue()) {
1160 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1161 return ReplaceInstUsesWith(I, ConstantBool::False);
1162 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1163 return ReplaceInstUsesWith(I, ConstantBool::True);
1164 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1165 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
1166 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1167 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
1169 // Comparing against a value really close to min or max?
1170 } else if (isMinValuePlusOne(CI)) {
1171 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1172 return BinaryOperator::create(Instruction::SetEQ, Op0,
1173 SubOne(CI), I.getName());
1174 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1175 return BinaryOperator::create(Instruction::SetNE, Op0,
1176 SubOne(CI), I.getName());
1178 } else if (isMaxValueMinusOne(CI)) {
1179 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1180 return BinaryOperator::create(Instruction::SetEQ, Op0,
1181 AddOne(CI), I.getName());
1182 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1183 return BinaryOperator::create(Instruction::SetNE, Op0,
1184 AddOne(CI), I.getName());
1188 return Changed ? &I : 0;
1193 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1194 assert(I.getOperand(1)->getType() == Type::UByteTy);
1195 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1196 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1198 // shl X, 0 == X and shr X, 0 == X
1199 // shl 0, X == 0 and shr 0, X == 0
1200 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1201 Op0 == Constant::getNullValue(Op0->getType()))
1202 return ReplaceInstUsesWith(I, Op0);
1204 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1206 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1207 if (CSI->isAllOnesValue())
1208 return ReplaceInstUsesWith(I, CSI);
1210 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1211 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1212 // of a signed value.
1214 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1215 if (CUI->getValue() >= TypeBits &&
1216 (!Op0->getType()->isSigned() || isLeftShift))
1217 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1219 // ((X*C1) << C2) == (X * (C1 << C2))
1220 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1221 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1222 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1223 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1227 // If the operand is an bitwise operator with a constant RHS, and the
1228 // shift is the only use, we can pull it out of the shift.
1229 if (Op0->use_size() == 1)
1230 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1231 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1232 bool isValid = true; // Valid only for And, Or, Xor
1233 bool highBitSet = false; // Transform if high bit of constant set?
1235 switch (Op0BO->getOpcode()) {
1236 default: isValid = false; break; // Do not perform transform!
1237 case Instruction::Or:
1238 case Instruction::Xor:
1241 case Instruction::And:
1246 // If this is a signed shift right, and the high bit is modified
1247 // by the logical operation, do not perform the transformation.
1248 // The highBitSet boolean indicates the value of the high bit of
1249 // the constant which would cause it to be modified for this
1252 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1253 uint64_t Val = Op0C->getRawValue();
1254 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1259 ConstantFoldShiftInstruction(I.getOpcode(), Op0C, CUI);
1261 Instruction *NewShift =
1262 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1265 InsertNewInstBefore(NewShift, I);
1267 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1272 // If this is a shift of a shift, see if we can fold the two together...
1273 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1274 if (ConstantUInt *ShiftAmt1C =
1275 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1276 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1277 unsigned ShiftAmt2 = CUI->getValue();
1279 // Check for (A << c1) << c2 and (A >> c1) >> c2
1280 if (I.getOpcode() == Op0SI->getOpcode()) {
1281 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1282 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1283 ConstantUInt::get(Type::UByteTy, Amt));
1286 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1287 // signed types, we can only support the (A >> c1) << c2 configuration,
1288 // because it can not turn an arbitrary bit of A into a sign bit.
1289 if (I.getType()->isUnsigned() || isLeftShift) {
1290 // Calculate bitmask for what gets shifted off the edge...
1291 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1293 C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
1295 C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
1298 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1299 C, Op0SI->getOperand(0)->getName()+".mask");
1300 InsertNewInstBefore(Mask, I);
1302 // Figure out what flavor of shift we should use...
1303 if (ShiftAmt1 == ShiftAmt2)
1304 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1305 else if (ShiftAmt1 < ShiftAmt2) {
1306 return new ShiftInst(I.getOpcode(), Mask,
1307 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1309 return new ShiftInst(Op0SI->getOpcode(), Mask,
1310 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1320 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1323 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1324 const Type *DstTy) {
1326 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1327 // are identical and the bits don't get reinterpreted (for example
1328 // int->float->int would not be allowed)
1329 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1332 // Allow free casting and conversion of sizes as long as the sign doesn't
1334 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1335 unsigned SrcSize = SrcTy->getPrimitiveSize();
1336 unsigned MidSize = MidTy->getPrimitiveSize();
1337 unsigned DstSize = DstTy->getPrimitiveSize();
1339 // Cases where we are monotonically decreasing the size of the type are
1340 // always ok, regardless of what sign changes are going on.
1342 if (SrcSize >= MidSize && MidSize >= DstSize)
1345 // Cases where the source and destination type are the same, but the middle
1346 // type is bigger are noops.
1348 if (SrcSize == DstSize && MidSize > SrcSize)
1351 // If we are monotonically growing, things are more complex.
1353 if (SrcSize <= MidSize && MidSize <= DstSize) {
1354 // We have eight combinations of signedness to worry about. Here's the
1356 static const int SignTable[8] = {
1357 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1358 1, // U U U Always ok
1359 1, // U U S Always ok
1360 3, // U S U Ok iff SrcSize != MidSize
1361 3, // U S S Ok iff SrcSize != MidSize
1362 0, // S U U Never ok
1363 2, // S U S Ok iff MidSize == DstSize
1364 1, // S S U Always ok
1365 1, // S S S Always ok
1368 // Choose an action based on the current entry of the signtable that this
1369 // cast of cast refers to...
1370 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1371 switch (SignTable[Row]) {
1372 case 0: return false; // Never ok
1373 case 1: return true; // Always ok
1374 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1375 case 3: // Ok iff SrcSize != MidSize
1376 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1377 default: assert(0 && "Bad entry in sign table!");
1382 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1383 // like: short -> ushort -> uint, because this can create wrong results if
1384 // the input short is negative!
1389 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1390 if (V->getType() == Ty || isa<Constant>(V)) return false;
1391 if (const CastInst *CI = dyn_cast<CastInst>(V))
1392 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1397 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1398 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1399 /// casts that are known to not do anything...
1401 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1402 Instruction *InsertBefore) {
1403 if (V->getType() == DestTy) return V;
1404 if (Constant *C = dyn_cast<Constant>(V))
1405 return ConstantExpr::getCast(C, DestTy);
1407 CastInst *CI = new CastInst(V, DestTy, V->getName());
1408 InsertNewInstBefore(CI, *InsertBefore);
1412 // CastInst simplification
1414 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1415 Value *Src = CI.getOperand(0);
1417 // If the user is casting a value to the same type, eliminate this cast
1419 if (CI.getType() == Src->getType())
1420 return ReplaceInstUsesWith(CI, Src);
1422 // If casting the result of another cast instruction, try to eliminate this
1425 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1426 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1427 CSrc->getType(), CI.getType())) {
1428 // This instruction now refers directly to the cast's src operand. This
1429 // has a good chance of making CSrc dead.
1430 CI.setOperand(0, CSrc->getOperand(0));
1434 // If this is an A->B->A cast, and we are dealing with integral types, try
1435 // to convert this into a logical 'and' instruction.
1437 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1438 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1439 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1440 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1441 assert(CSrc->getType() != Type::ULongTy &&
1442 "Cannot have type bigger than ulong!");
1443 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1444 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1445 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1450 // If casting the result of a getelementptr instruction with no offset, turn
1451 // this into a cast of the original pointer!
1453 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1454 bool AllZeroOperands = true;
1455 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1456 if (!isa<Constant>(GEP->getOperand(i)) ||
1457 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1458 AllZeroOperands = false;
1461 if (AllZeroOperands) {
1462 CI.setOperand(0, GEP->getOperand(0));
1467 // If the source value is an instruction with only this use, we can attempt to
1468 // propagate the cast into the instruction. Also, only handle integral types
1470 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
1471 if (SrcI->use_size() == 1 && Src->getType()->isIntegral() &&
1472 CI.getType()->isInteger()) { // Don't mess with casts to bool here
1473 const Type *DestTy = CI.getType();
1474 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
1475 unsigned DestBitSize = getTypeSizeInBits(DestTy);
1477 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
1478 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
1480 switch (SrcI->getOpcode()) {
1481 case Instruction::Add:
1482 case Instruction::Mul:
1483 case Instruction::And:
1484 case Instruction::Or:
1485 case Instruction::Xor:
1486 // If we are discarding information, or just changing the sign, rewrite.
1487 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
1488 // Don't insert two casts if they cannot be eliminated. We allow two
1489 // casts to be inserted if the sizes are the same. This could only be
1490 // converting signedness, which is a noop.
1491 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
1492 !ValueRequiresCast(Op0, DestTy)) {
1493 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1494 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
1495 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
1496 ->getOpcode(), Op0c, Op1c);
1500 case Instruction::Shl:
1501 // Allow changing the sign of the source operand. Do not allow changing
1502 // the size of the shift, UNLESS the shift amount is a constant. We
1503 // mush not change variable sized shifts to a smaller size, because it
1504 // is undefined to shift more bits out than exist in the value.
1505 if (DestBitSize == SrcBitSize ||
1506 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
1507 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
1508 return new ShiftInst(Instruction::Shl, Op0c, Op1);
1517 // CallInst simplification
1519 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1520 if (transformConstExprCastCall(&CI)) return 0;
1524 // InvokeInst simplification
1526 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1527 if (transformConstExprCastCall(&II)) return 0;
1531 // getPromotedType - Return the specified type promoted as it would be to pass
1532 // though a va_arg area...
1533 static const Type *getPromotedType(const Type *Ty) {
1534 switch (Ty->getPrimitiveID()) {
1535 case Type::SByteTyID:
1536 case Type::ShortTyID: return Type::IntTy;
1537 case Type::UByteTyID:
1538 case Type::UShortTyID: return Type::UIntTy;
1539 case Type::FloatTyID: return Type::DoubleTy;
1544 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1545 // attempt to move the cast to the arguments of the call/invoke.
1547 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1548 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1549 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1550 if (CE->getOpcode() != Instruction::Cast ||
1551 !isa<ConstantPointerRef>(CE->getOperand(0)))
1553 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1554 if (!isa<Function>(CPR->getValue())) return false;
1555 Function *Callee = cast<Function>(CPR->getValue());
1556 Instruction *Caller = CS.getInstruction();
1558 // Okay, this is a cast from a function to a different type. Unless doing so
1559 // would cause a type conversion of one of our arguments, change this call to
1560 // be a direct call with arguments casted to the appropriate types.
1562 const FunctionType *FT = Callee->getFunctionType();
1563 const Type *OldRetTy = Caller->getType();
1565 if (Callee->isExternal() &&
1566 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()))
1567 return false; // Cannot transform this return value...
1569 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1570 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1572 CallSite::arg_iterator AI = CS.arg_begin();
1573 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1574 const Type *ParamTy = FT->getParamType(i);
1575 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1576 if (Callee->isExternal() && !isConvertible) return false;
1579 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1580 Callee->isExternal())
1581 return false; // Do not delete arguments unless we have a function body...
1583 // Okay, we decided that this is a safe thing to do: go ahead and start
1584 // inserting cast instructions as necessary...
1585 std::vector<Value*> Args;
1586 Args.reserve(NumActualArgs);
1588 AI = CS.arg_begin();
1589 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1590 const Type *ParamTy = FT->getParamType(i);
1591 if ((*AI)->getType() == ParamTy) {
1592 Args.push_back(*AI);
1594 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1595 InsertNewInstBefore(Cast, *Caller);
1596 Args.push_back(Cast);
1600 // If the function takes more arguments than the call was taking, add them
1602 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1603 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1605 // If we are removing arguments to the function, emit an obnoxious warning...
1606 if (FT->getNumParams() < NumActualArgs)
1607 if (!FT->isVarArg()) {
1608 std::cerr << "WARNING: While resolving call to function '"
1609 << Callee->getName() << "' arguments were dropped!\n";
1611 // Add all of the arguments in their promoted form to the arg list...
1612 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1613 const Type *PTy = getPromotedType((*AI)->getType());
1614 if (PTy != (*AI)->getType()) {
1615 // Must promote to pass through va_arg area!
1616 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1617 InsertNewInstBefore(Cast, *Caller);
1618 Args.push_back(Cast);
1620 Args.push_back(*AI);
1625 if (FT->getReturnType() == Type::VoidTy)
1626 Caller->setName(""); // Void type should not have a name...
1629 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1630 NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(),
1631 Args, Caller->getName(), Caller);
1633 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1636 // Insert a cast of the return type as necessary...
1638 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1639 if (NV->getType() != Type::VoidTy) {
1640 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1641 InsertNewInstBefore(NC, *Caller);
1642 AddUsesToWorkList(*Caller);
1644 NV = Constant::getNullValue(Caller->getType());
1648 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1649 Caller->replaceAllUsesWith(NV);
1650 Caller->getParent()->getInstList().erase(Caller);
1651 removeFromWorkList(Caller);
1657 // PHINode simplification
1659 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
1660 // If the PHI node only has one incoming value, eliminate the PHI node...
1661 if (PN.getNumIncomingValues() == 1)
1662 return ReplaceInstUsesWith(PN, PN.getIncomingValue(0));
1664 // Otherwise if all of the incoming values are the same for the PHI, replace
1665 // the PHI node with the incoming value.
1668 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
1669 if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself...
1670 if (InVal && PN.getIncomingValue(i) != InVal)
1671 return 0; // Not the same, bail out.
1673 InVal = PN.getIncomingValue(i);
1675 // The only case that could cause InVal to be null is if we have a PHI node
1676 // that only has entries for itself. In this case, there is no entry into the
1677 // loop, so kill the PHI.
1679 if (InVal == 0) InVal = Constant::getNullValue(PN.getType());
1681 // All of the incoming values are the same, replace the PHI node now.
1682 return ReplaceInstUsesWith(PN, InVal);
1686 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1687 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
1688 // If so, eliminate the noop.
1689 if ((GEP.getNumOperands() == 2 &&
1690 GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
1691 GEP.getNumOperands() == 1)
1692 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
1694 // Combine Indices - If the source pointer to this getelementptr instruction
1695 // is a getelementptr instruction, combine the indices of the two
1696 // getelementptr instructions into a single instruction.
1698 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
1699 std::vector<Value *> Indices;
1701 // Can we combine the two pointer arithmetics offsets?
1702 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
1703 isa<Constant>(GEP.getOperand(1))) {
1704 // Replace: gep (gep %P, long C1), long C2, ...
1705 // With: gep %P, long (C1+C2), ...
1706 Value *Sum = ConstantExpr::get(Instruction::Add,
1707 cast<Constant>(Src->getOperand(1)),
1708 cast<Constant>(GEP.getOperand(1)));
1709 assert(Sum && "Constant folding of longs failed!?");
1710 GEP.setOperand(0, Src->getOperand(0));
1711 GEP.setOperand(1, Sum);
1712 AddUsesToWorkList(*Src); // Reduce use count of Src
1714 } else if (Src->getNumOperands() == 2) {
1715 // Replace: gep (gep %P, long B), long A, ...
1716 // With: T = long A+B; gep %P, T, ...
1718 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
1720 Src->getName()+".sum", &GEP);
1721 GEP.setOperand(0, Src->getOperand(0));
1722 GEP.setOperand(1, Sum);
1723 WorkList.push_back(cast<Instruction>(Sum));
1725 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
1726 Src->getNumOperands() != 1) {
1727 // Otherwise we can do the fold if the first index of the GEP is a zero
1728 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
1729 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
1730 } else if (Src->getOperand(Src->getNumOperands()-1) ==
1731 Constant::getNullValue(Type::LongTy)) {
1732 // If the src gep ends with a constant array index, merge this get into
1733 // it, even if we have a non-zero array index.
1734 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
1735 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
1738 if (!Indices.empty())
1739 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
1741 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
1742 // GEP of global variable. If all of the indices for this GEP are
1743 // constants, we can promote this to a constexpr instead of an instruction.
1745 // Scan for nonconstants...
1746 std::vector<Constant*> Indices;
1747 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
1748 for (; I != E && isa<Constant>(*I); ++I)
1749 Indices.push_back(cast<Constant>(*I));
1751 if (I == E) { // If they are all constants...
1753 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
1755 // Replace all uses of the GEP with the new constexpr...
1756 return ReplaceInstUsesWith(GEP, CE);
1763 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
1764 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
1765 if (AI.isArrayAllocation()) // Check C != 1
1766 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
1767 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
1768 AllocationInst *New = 0;
1770 // Create and insert the replacement instruction...
1771 if (isa<MallocInst>(AI))
1772 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
1774 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
1775 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
1778 // Scan to the end of the allocation instructions, to skip over a block of
1779 // allocas if possible...
1781 BasicBlock::iterator It = New;
1782 while (isa<AllocationInst>(*It)) ++It;
1784 // Now that I is pointing to the first non-allocation-inst in the block,
1785 // insert our getelementptr instruction...
1787 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
1788 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
1790 // Now make everything use the getelementptr instead of the original
1792 ReplaceInstUsesWith(AI, V);
1798 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
1799 /// constantexpr, return the constant value being addressed by the constant
1800 /// expression, or null if something is funny.
1802 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
1803 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
1804 return 0; // Do not allow stepping over the value!
1806 // Loop over all of the operands, tracking down which value we are
1808 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
1809 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
1810 ConstantStruct *CS = cast<ConstantStruct>(C);
1811 if (CU->getValue() >= CS->getValues().size()) return 0;
1812 C = cast<Constant>(CS->getValues()[CU->getValue()]);
1813 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
1814 ConstantArray *CA = cast<ConstantArray>(C);
1815 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
1816 C = cast<Constant>(CA->getValues()[CS->getValue()]);
1822 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
1823 Value *Op = LI.getOperand(0);
1824 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
1825 Op = CPR->getValue();
1827 // Instcombine load (constant global) into the value loaded...
1828 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
1829 if (GV->isConstant() && !GV->isExternal())
1830 return ReplaceInstUsesWith(LI, GV->getInitializer());
1832 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
1833 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
1834 if (CE->getOpcode() == Instruction::GetElementPtr)
1835 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
1836 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
1837 if (GV->isConstant() && !GV->isExternal())
1838 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
1839 return ReplaceInstUsesWith(LI, V);
1844 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
1845 // Change br (not X), label True, label False to: br X, label False, True
1846 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
1847 if (Value *V = dyn_castNotVal(BI.getCondition())) {
1848 BasicBlock *TrueDest = BI.getSuccessor(0);
1849 BasicBlock *FalseDest = BI.getSuccessor(1);
1850 // Swap Destinations and condition...
1852 BI.setSuccessor(0, FalseDest);
1853 BI.setSuccessor(1, TrueDest);
1860 void InstCombiner::removeFromWorkList(Instruction *I) {
1861 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
1865 bool InstCombiner::runOnFunction(Function &F) {
1866 bool Changed = false;
1868 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
1870 while (!WorkList.empty()) {
1871 Instruction *I = WorkList.back(); // Get an instruction from the worklist
1872 WorkList.pop_back();
1874 // Check to see if we can DCE or ConstantPropagate the instruction...
1875 // Check to see if we can DIE the instruction...
1876 if (isInstructionTriviallyDead(I)) {
1877 // Add operands to the worklist...
1878 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
1879 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
1880 WorkList.push_back(Op);
1883 BasicBlock::iterator BBI = I;
1884 if (dceInstruction(BBI)) {
1885 removeFromWorkList(I);
1890 // Instruction isn't dead, see if we can constant propagate it...
1891 if (Constant *C = ConstantFoldInstruction(I)) {
1892 // Add operands to the worklist...
1893 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
1894 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
1895 WorkList.push_back(Op);
1896 ReplaceInstUsesWith(*I, C);
1899 BasicBlock::iterator BBI = I;
1900 if (dceInstruction(BBI)) {
1901 removeFromWorkList(I);
1906 // Now that we have an instruction, try combining it to simplify it...
1907 if (Instruction *Result = visit(*I)) {
1909 // Should we replace the old instruction with a new one?
1911 // Instructions can end up on the worklist more than once. Make sure
1912 // we do not process an instruction that has been deleted.
1913 removeFromWorkList(I);
1914 ReplaceInstWithInst(I, Result);
1916 BasicBlock::iterator II = I;
1918 // If the instruction was modified, it's possible that it is now dead.
1919 // if so, remove it.
1920 if (dceInstruction(II)) {
1921 // Instructions may end up in the worklist more than once. Erase them
1923 removeFromWorkList(I);
1929 WorkList.push_back(Result);
1930 AddUsesToWorkList(*Result);
1939 Pass *createInstructionCombiningPass() {
1940 return new InstCombiner();