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 //===----------------------------------------------------------------------===//
17 #include "llvm/Transforms/Scalar.h"
18 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
19 #include "llvm/Transforms/Utils/Local.h"
20 #include "llvm/Instructions.h"
21 #include "llvm/Pass.h"
22 #include "llvm/Constants.h"
23 #include "llvm/ConstantHandling.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/GlobalVariable.h"
26 #include "llvm/Support/InstIterator.h"
27 #include "llvm/Support/InstVisitor.h"
28 #include "llvm/Support/CallSite.h"
29 #include "Support/Statistic.h"
33 Statistic<> NumCombined ("instcombine", "Number of insts combined");
34 Statistic<> NumConstProp("instcombine", "Number of constant folds");
35 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
37 class InstCombiner : public FunctionPass,
38 public InstVisitor<InstCombiner, Instruction*> {
39 // Worklist of all of the instructions that need to be simplified.
40 std::vector<Instruction*> WorkList;
42 void AddUsesToWorkList(Instruction &I) {
43 // The instruction was simplified, add all users of the instruction to
44 // the work lists because they might get more simplified now...
46 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
48 WorkList.push_back(cast<Instruction>(*UI));
51 // removeFromWorkList - remove all instances of I from the worklist.
52 void removeFromWorkList(Instruction *I);
54 virtual bool runOnFunction(Function &F);
56 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
60 // Visitation implementation - Implement instruction combining for different
61 // instruction types. The semantics are as follows:
63 // null - No change was made
64 // I - Change was made, I is still valid, I may be dead though
65 // otherwise - Change was made, replace I with returned instruction
67 Instruction *visitAdd(BinaryOperator &I);
68 Instruction *visitSub(BinaryOperator &I);
69 Instruction *visitMul(BinaryOperator &I);
70 Instruction *visitDiv(BinaryOperator &I);
71 Instruction *visitRem(BinaryOperator &I);
72 Instruction *visitAnd(BinaryOperator &I);
73 Instruction *visitOr (BinaryOperator &I);
74 Instruction *visitXor(BinaryOperator &I);
75 Instruction *visitSetCondInst(BinaryOperator &I);
76 Instruction *visitShiftInst(ShiftInst &I);
77 Instruction *visitCastInst(CastInst &CI);
78 Instruction *visitCallInst(CallInst &CI);
79 Instruction *visitInvokeInst(InvokeInst &II);
80 Instruction *visitPHINode(PHINode &PN);
81 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
82 Instruction *visitAllocationInst(AllocationInst &AI);
83 Instruction *visitLoadInst(LoadInst &LI);
84 Instruction *visitBranchInst(BranchInst &BI);
86 // visitInstruction - Specify what to return for unhandled instructions...
87 Instruction *visitInstruction(Instruction &I) { return 0; }
90 bool transformConstExprCastCall(CallSite CS);
92 // InsertNewInstBefore - insert an instruction New before instruction Old
93 // in the program. Add the new instruction to the worklist.
95 void InsertNewInstBefore(Instruction *New, Instruction &Old) {
96 assert(New && New->getParent() == 0 &&
97 "New instruction already inserted into a basic block!");
98 BasicBlock *BB = Old.getParent();
99 BB->getInstList().insert(&Old, New); // Insert inst
100 WorkList.push_back(New); // Add to worklist
103 // ReplaceInstUsesWith - This method is to be used when an instruction is
104 // found to be dead, replacable with another preexisting expression. Here
105 // we add all uses of I to the worklist, replace all uses of I with the new
106 // value, then return I, so that the inst combiner will know that I was
109 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
110 AddUsesToWorkList(I); // Add all modified instrs to worklist
111 I.replaceAllUsesWith(V);
115 // SimplifyCommutative - This performs a few simplifications for commutative
117 bool SimplifyCommutative(BinaryOperator &I);
120 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
123 // getComplexity: Assign a complexity or rank value to LLVM Values...
124 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
125 static unsigned getComplexity(Value *V) {
126 if (isa<Instruction>(V)) {
127 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
131 if (isa<Argument>(V)) return 2;
132 return isa<Constant>(V) ? 0 : 1;
135 // isOnlyUse - Return true if this instruction will be deleted if we stop using
137 static bool isOnlyUse(Value *V) {
138 return V->use_size() == 1 || isa<Constant>(V);
141 // SimplifyCommutative - This performs a few simplifications for commutative
144 // 1. Order operands such that they are listed from right (least complex) to
145 // left (most complex). This puts constants before unary operators before
148 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
149 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
151 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
152 bool Changed = false;
153 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
154 Changed = !I.swapOperands();
156 if (!I.isAssociative()) return Changed;
157 Instruction::BinaryOps Opcode = I.getOpcode();
158 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
159 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
160 if (isa<Constant>(I.getOperand(1))) {
161 Constant *Folded = ConstantExpr::get(I.getOpcode(),
162 cast<Constant>(I.getOperand(1)),
163 cast<Constant>(Op->getOperand(1)));
164 I.setOperand(0, Op->getOperand(0));
165 I.setOperand(1, Folded);
167 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
168 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
169 isOnlyUse(Op) && isOnlyUse(Op1)) {
170 Constant *C1 = cast<Constant>(Op->getOperand(1));
171 Constant *C2 = cast<Constant>(Op1->getOperand(1));
173 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
174 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
175 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
178 WorkList.push_back(New);
179 I.setOperand(0, New);
180 I.setOperand(1, Folded);
187 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
188 // if the LHS is a constant zero (which is the 'negate' form).
190 static inline Value *dyn_castNegVal(Value *V) {
191 if (BinaryOperator::isNeg(V))
192 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
194 // Constants can be considered to be negated values if they can be folded...
195 if (Constant *C = dyn_cast<Constant>(V))
196 return ConstantExpr::get(Instruction::Sub,
197 Constant::getNullValue(V->getType()), C);
201 static inline Value *dyn_castNotVal(Value *V) {
202 if (BinaryOperator::isNot(V))
203 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
205 // Constants can be considered to be not'ed values...
206 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
207 return ConstantExpr::get(Instruction::Xor,
208 ConstantIntegral::getAllOnesValue(C->getType()),C);
212 // dyn_castFoldableMul - If this value is a multiply that can be folded into
213 // other computations (because it has a constant operand), return the
214 // non-constant operand of the multiply.
216 static inline Value *dyn_castFoldableMul(Value *V) {
217 if (V->use_size() == 1 && V->getType()->isInteger())
218 if (Instruction *I = dyn_cast<Instruction>(V))
219 if (I->getOpcode() == Instruction::Mul)
220 if (isa<Constant>(I->getOperand(1)))
221 return I->getOperand(0);
225 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
226 // a constant, return the constant being anded with.
228 static inline Constant *dyn_castMaskingAnd(Value *V) {
229 if (Instruction *I = dyn_cast<Instruction>(V))
230 if (I->getOpcode() == Instruction::And)
231 return dyn_cast<Constant>(I->getOperand(1));
233 // If this is a constant, it acts just like we were masking with it.
234 return dyn_cast<Constant>(V);
237 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
239 static unsigned Log2(uint64_t Val) {
240 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
243 if (Val & 1) return 0; // Multiple bits set?
250 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
251 bool Changed = SimplifyCommutative(I);
252 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
254 // Eliminate 'add int %X, 0'
255 if (RHS == Constant::getNullValue(I.getType()))
256 return ReplaceInstUsesWith(I, LHS);
259 if (Value *V = dyn_castNegVal(LHS))
260 return BinaryOperator::create(Instruction::Sub, RHS, V);
263 if (!isa<Constant>(RHS))
264 if (Value *V = dyn_castNegVal(RHS))
265 return BinaryOperator::create(Instruction::Sub, LHS, V);
267 // X*C + X --> X * (C+1)
268 if (dyn_castFoldableMul(LHS) == RHS) {
270 ConstantExpr::get(Instruction::Add,
271 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
272 ConstantInt::get(I.getType(), 1));
273 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
276 // X + X*C --> X * (C+1)
277 if (dyn_castFoldableMul(RHS) == LHS) {
279 ConstantExpr::get(Instruction::Add,
280 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
281 ConstantInt::get(I.getType(), 1));
282 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
285 // (A & C1)+(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
286 if (Constant *C1 = dyn_castMaskingAnd(LHS))
287 if (Constant *C2 = dyn_castMaskingAnd(RHS))
288 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
289 return BinaryOperator::create(Instruction::Or, LHS, RHS);
291 return Changed ? &I : 0;
294 // isSignBit - Return true if the value represented by the constant only has the
295 // highest order bit set.
296 static bool isSignBit(ConstantInt *CI) {
297 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
298 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
301 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
302 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
304 if (Op0 == Op1) // sub X, X -> 0
305 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
307 // If this is a 'B = x-(-A)', change to B = x+A...
308 if (Value *V = dyn_castNegVal(Op1))
309 return BinaryOperator::create(Instruction::Add, Op0, V);
311 // Replace (-1 - A) with (~A)...
312 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0))
313 if (C->isAllOnesValue())
314 return BinaryOperator::createNot(Op1);
316 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
317 if (Op1I->use_size() == 1) {
318 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
319 // is not used by anyone else...
321 if (Op1I->getOpcode() == Instruction::Sub) {
322 // Swap the two operands of the subexpr...
323 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
324 Op1I->setOperand(0, IIOp1);
325 Op1I->setOperand(1, IIOp0);
327 // Create the new top level add instruction...
328 return BinaryOperator::create(Instruction::Add, Op0, Op1);
331 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
333 if (Op1I->getOpcode() == Instruction::And &&
334 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
335 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
337 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
338 return BinaryOperator::create(Instruction::And, Op0, NewNot);
341 // X - X*C --> X * (1-C)
342 if (dyn_castFoldableMul(Op1I) == Op0) {
344 ConstantExpr::get(Instruction::Sub,
345 ConstantInt::get(I.getType(), 1),
346 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
347 assert(CP1 && "Couldn't constant fold 1-C?");
348 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
352 // X*C - X --> X * (C-1)
353 if (dyn_castFoldableMul(Op0) == Op1) {
355 ConstantExpr::get(Instruction::Sub,
356 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
357 ConstantInt::get(I.getType(), 1));
358 assert(CP1 && "Couldn't constant fold C - 1?");
359 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
365 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
366 bool Changed = SimplifyCommutative(I);
367 Value *Op0 = I.getOperand(0);
369 // Simplify mul instructions with a constant RHS...
370 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
371 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
372 const Type *Ty = CI->getType();
373 int64_t Val = Ty->isSigned() ? cast<ConstantSInt>(CI)->getValue() :
374 (int64_t)cast<ConstantUInt>(CI)->getValue();
376 case -1: // X * -1 -> -X
377 return BinaryOperator::createNeg(Op0, I.getName());
379 return ReplaceInstUsesWith(I, Op1); // Eliminate 'mul double %X, 0'
381 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul int %X, 1'
382 case 2: // Convert 'mul int %X, 2' to 'add int %X, %X'
383 return BinaryOperator::create(Instruction::Add, Op0, Op0, I.getName());
386 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
387 return new ShiftInst(Instruction::Shl, Op0,
388 ConstantUInt::get(Type::UByteTy, C));
390 ConstantFP *Op1F = cast<ConstantFP>(Op1);
391 if (Op1F->isNullValue())
392 return ReplaceInstUsesWith(I, Op1);
394 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
395 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
396 if (Op1F->getValue() == 1.0)
397 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
401 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
402 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
403 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
405 return Changed ? &I : 0;
408 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
410 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
411 if (RHS->equalsInt(1))
412 return ReplaceInstUsesWith(I, I.getOperand(0));
414 // Check to see if this is an unsigned division with an exact power of 2,
415 // if so, convert to a right shift.
416 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
417 if (uint64_t Val = C->getValue()) // Don't break X / 0
418 if (uint64_t C = Log2(Val))
419 return new ShiftInst(Instruction::Shr, I.getOperand(0),
420 ConstantUInt::get(Type::UByteTy, C));
423 // 0 / X == 0, we don't need to preserve faults!
424 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
425 if (LHS->equalsInt(0))
426 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
432 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
433 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
434 if (RHS->equalsInt(1)) // X % 1 == 0
435 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
437 // Check to see if this is an unsigned remainder with an exact power of 2,
438 // if so, convert to a bitwise and.
439 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
440 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
442 return BinaryOperator::create(Instruction::And, I.getOperand(0),
443 ConstantUInt::get(I.getType(), Val-1));
446 // 0 % X == 0, we don't need to preserve faults!
447 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
448 if (LHS->equalsInt(0))
449 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
454 // isMaxValueMinusOne - return true if this is Max-1
455 static bool isMaxValueMinusOne(const ConstantInt *C) {
456 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
457 // Calculate -1 casted to the right type...
458 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
459 uint64_t Val = ~0ULL; // All ones
460 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
461 return CU->getValue() == Val-1;
464 const ConstantSInt *CS = cast<ConstantSInt>(C);
466 // Calculate 0111111111..11111
467 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
468 int64_t Val = INT64_MAX; // All ones
469 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
470 return CS->getValue() == Val-1;
473 // isMinValuePlusOne - return true if this is Min+1
474 static bool isMinValuePlusOne(const ConstantInt *C) {
475 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
476 return CU->getValue() == 1;
478 const ConstantSInt *CS = cast<ConstantSInt>(C);
480 // Calculate 1111111111000000000000
481 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
482 int64_t Val = -1; // All ones
483 Val <<= TypeBits-1; // Shift over to the right spot
484 return CS->getValue() == Val+1;
488 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
489 bool Changed = SimplifyCommutative(I);
490 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
492 // and X, X = X and X, 0 == 0
493 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
494 return ReplaceInstUsesWith(I, Op1);
497 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1))
498 if (RHS->isAllOnesValue())
499 return ReplaceInstUsesWith(I, Op0);
501 Value *Op0NotVal = dyn_castNotVal(Op0);
502 Value *Op1NotVal = dyn_castNotVal(Op1);
504 // (~A & ~B) == (~(A | B)) - Demorgan's Law
505 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
506 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
507 Op1NotVal,I.getName()+".demorgan",
509 WorkList.push_back(Or);
510 return BinaryOperator::createNot(Or);
513 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
514 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
516 return Changed ? &I : 0;
521 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
522 bool Changed = SimplifyCommutative(I);
523 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
525 // or X, X = X or X, 0 == X
526 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
527 return ReplaceInstUsesWith(I, Op0);
530 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1))
531 if (RHS->isAllOnesValue())
532 return ReplaceInstUsesWith(I, Op1);
534 Value *Op0NotVal = dyn_castNotVal(Op0);
535 Value *Op1NotVal = dyn_castNotVal(Op1);
537 if (Op1 == Op0NotVal) // ~A | A == -1
538 return ReplaceInstUsesWith(I,
539 ConstantIntegral::getAllOnesValue(I.getType()));
541 if (Op0 == Op1NotVal) // A | ~A == -1
542 return ReplaceInstUsesWith(I,
543 ConstantIntegral::getAllOnesValue(I.getType()));
545 // (~A | ~B) == (~(A & B)) - Demorgan's Law
546 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
547 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
548 Op1NotVal,I.getName()+".demorgan",
550 WorkList.push_back(And);
551 return BinaryOperator::createNot(And);
554 return Changed ? &I : 0;
559 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
560 bool Changed = SimplifyCommutative(I);
561 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
565 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
567 if (ConstantIntegral *Op1C = dyn_cast<ConstantIntegral>(Op1)) {
569 if (Op1C->isNullValue())
570 return ReplaceInstUsesWith(I, Op0);
572 // Is this a "NOT" instruction?
573 if (Op1C->isAllOnesValue()) {
574 // xor (xor X, -1), -1 = not (not X) = X
575 if (Value *X = dyn_castNotVal(Op0))
576 return ReplaceInstUsesWith(I, X);
578 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
579 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0))
580 if (SCI->use_size() == 1)
581 return new SetCondInst(SCI->getInverseCondition(),
582 SCI->getOperand(0), SCI->getOperand(1));
586 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
588 return ReplaceInstUsesWith(I,
589 ConstantIntegral::getAllOnesValue(I.getType()));
591 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
593 return ReplaceInstUsesWith(I,
594 ConstantIntegral::getAllOnesValue(I.getType()));
596 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
597 if (Op1I->getOpcode() == Instruction::Or)
598 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
599 cast<BinaryOperator>(Op1I)->swapOperands();
602 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
607 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
608 if (Op0I->getOpcode() == Instruction::Or && Op0I->use_size() == 1) {
609 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
610 cast<BinaryOperator>(Op0I)->swapOperands();
611 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
612 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
613 WorkList.push_back(cast<Instruction>(NotB));
614 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
619 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
620 if (Constant *C1 = dyn_castMaskingAnd(Op0))
621 if (Constant *C2 = dyn_castMaskingAnd(Op1))
622 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
623 return BinaryOperator::create(Instruction::Or, Op0, Op1);
625 return Changed ? &I : 0;
628 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
629 static Constant *AddOne(ConstantInt *C) {
630 Constant *Result = ConstantExpr::get(Instruction::Add, C,
631 ConstantInt::get(C->getType(), 1));
632 assert(Result && "Constant folding integer addition failed!");
635 static Constant *SubOne(ConstantInt *C) {
636 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
637 ConstantInt::get(C->getType(), 1));
638 assert(Result && "Constant folding integer addition failed!");
642 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
643 // true when both operands are equal...
645 static bool isTrueWhenEqual(Instruction &I) {
646 return I.getOpcode() == Instruction::SetEQ ||
647 I.getOpcode() == Instruction::SetGE ||
648 I.getOpcode() == Instruction::SetLE;
651 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
652 bool Changed = SimplifyCommutative(I);
653 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
654 const Type *Ty = Op0->getType();
658 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
660 // setcc <global*>, 0 - Global value addresses are never null!
661 if (isa<GlobalValue>(Op0) && isa<ConstantPointerNull>(Op1))
662 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
664 // setcc's with boolean values can always be turned into bitwise operations
665 if (Ty == Type::BoolTy) {
666 // If this is <, >, or !=, we can change this into a simple xor instruction
667 if (!isTrueWhenEqual(I))
668 return BinaryOperator::create(Instruction::Xor, Op0, Op1, I.getName());
670 // Otherwise we need to make a temporary intermediate instruction and insert
671 // it into the instruction stream. This is what we are after:
673 // seteq bool %A, %B -> ~(A^B)
674 // setle bool %A, %B -> ~A | B
675 // setge bool %A, %B -> A | ~B
677 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
678 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
680 InsertNewInstBefore(Xor, I);
681 return BinaryOperator::createNot(Xor, I.getName());
684 // Handle the setXe cases...
685 assert(I.getOpcode() == Instruction::SetGE ||
686 I.getOpcode() == Instruction::SetLE);
688 if (I.getOpcode() == Instruction::SetGE)
689 std::swap(Op0, Op1); // Change setge -> setle
691 // Now we just have the SetLE case.
692 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
693 InsertNewInstBefore(Not, I);
694 return BinaryOperator::create(Instruction::Or, Not, Op1, I.getName());
697 // Check to see if we are doing one of many comparisons against constant
698 // integers at the end of their ranges...
700 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
701 if (CI->isNullValue()) {
702 if (I.getOpcode() == Instruction::SetNE)
703 return new CastInst(Op0, Type::BoolTy, I.getName());
704 else if (I.getOpcode() == Instruction::SetEQ) {
705 // seteq X, 0 -> not (cast X to bool)
706 Instruction *Val = new CastInst(Op0, Type::BoolTy, I.getName()+".not");
707 InsertNewInstBefore(Val, I);
708 return BinaryOperator::createNot(Val, I.getName());
712 // Check to see if we are comparing against the minimum or maximum value...
713 if (CI->isMinValue()) {
714 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
715 return ReplaceInstUsesWith(I, ConstantBool::False);
716 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
717 return ReplaceInstUsesWith(I, ConstantBool::True);
718 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
719 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
720 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
721 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
723 } else if (CI->isMaxValue()) {
724 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
725 return ReplaceInstUsesWith(I, ConstantBool::False);
726 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
727 return ReplaceInstUsesWith(I, ConstantBool::True);
728 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
729 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
730 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
731 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
733 // Comparing against a value really close to min or max?
734 } else if (isMinValuePlusOne(CI)) {
735 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
736 return BinaryOperator::create(Instruction::SetEQ, Op0,
737 SubOne(CI), I.getName());
738 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
739 return BinaryOperator::create(Instruction::SetNE, Op0,
740 SubOne(CI), I.getName());
742 } else if (isMaxValueMinusOne(CI)) {
743 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
744 return BinaryOperator::create(Instruction::SetEQ, Op0,
745 AddOne(CI), I.getName());
746 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
747 return BinaryOperator::create(Instruction::SetNE, Op0,
748 AddOne(CI), I.getName());
752 return Changed ? &I : 0;
757 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
758 assert(I.getOperand(1)->getType() == Type::UByteTy);
759 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
761 // shl X, 0 == X and shr X, 0 == X
762 // shl 0, X == 0 and shr 0, X == 0
763 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
764 Op0 == Constant::getNullValue(Op0->getType()))
765 return ReplaceInstUsesWith(I, Op0);
767 // If this is a shift of a shift, see if we can fold the two together...
768 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0)) {
769 if (isa<Constant>(Op1) && isa<Constant>(Op0SI->getOperand(1))) {
770 ConstantUInt *ShiftAmt1C = cast<ConstantUInt>(Op0SI->getOperand(1));
771 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
772 unsigned ShiftAmt2 = cast<ConstantUInt>(Op1)->getValue();
774 // Check for (A << c1) << c2 and (A >> c1) >> c2
775 if (I.getOpcode() == Op0SI->getOpcode()) {
776 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
777 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
778 ConstantUInt::get(Type::UByteTy, Amt));
781 if (I.getType()->isUnsigned()) { // Check for (A << c1) >> c2 or visaversa
782 // Calculate bitmask for what gets shifted off the edge...
783 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
784 if (I.getOpcode() == Instruction::Shr)
785 C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
787 C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
790 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
791 C, Op0SI->getOperand(0)->getName()+".mask",&I);
792 WorkList.push_back(Mask);
794 // Figure out what flavor of shift we should use...
795 if (ShiftAmt1 == ShiftAmt2)
796 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
797 else if (ShiftAmt1 < ShiftAmt2) {
798 return new ShiftInst(I.getOpcode(), Mask,
799 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
801 return new ShiftInst(Op0SI->getOpcode(), Mask,
802 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
808 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr of
811 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
812 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
813 if (CUI->getValue() >= TypeBits &&
814 (!Op0->getType()->isSigned() || I.getOpcode() == Instruction::Shl))
815 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
817 // Check to see if we are shifting left by 1. If so, turn it into an add
819 if (I.getOpcode() == Instruction::Shl && CUI->equalsInt(1))
820 // Convert 'shl int %X, 1' to 'add int %X, %X'
821 return BinaryOperator::create(Instruction::Add, Op0, Op0, I.getName());
825 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
826 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
827 if (I.getOpcode() == Instruction::Shr && CSI->isAllOnesValue())
828 return ReplaceInstUsesWith(I, CSI);
834 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
837 static inline bool isEliminableCastOfCast(const CastInst &CI,
838 const CastInst *CSrc) {
839 assert(CI.getOperand(0) == CSrc);
840 const Type *SrcTy = CSrc->getOperand(0)->getType();
841 const Type *MidTy = CSrc->getType();
842 const Type *DstTy = CI.getType();
844 // It is legal to eliminate the instruction if casting A->B->A if the sizes
845 // are identical and the bits don't get reinterpreted (for example
846 // int->float->int would not be allowed)
847 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
850 // Allow free casting and conversion of sizes as long as the sign doesn't
852 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
853 unsigned SrcSize = SrcTy->getPrimitiveSize();
854 unsigned MidSize = MidTy->getPrimitiveSize();
855 unsigned DstSize = DstTy->getPrimitiveSize();
857 // Cases where we are monotonically decreasing the size of the type are
858 // always ok, regardless of what sign changes are going on.
860 if (SrcSize >= MidSize && MidSize >= DstSize)
863 // Cases where the source and destination type are the same, but the middle
864 // type is bigger are noops.
866 if (SrcSize == DstSize && MidSize > SrcSize)
869 // If we are monotonically growing, things are more complex.
871 if (SrcSize <= MidSize && MidSize <= DstSize) {
872 // We have eight combinations of signedness to worry about. Here's the
874 static const int SignTable[8] = {
875 // CODE, SrcSigned, MidSigned, DstSigned, Comment
876 1, // U U U Always ok
877 1, // U U S Always ok
878 3, // U S U Ok iff SrcSize != MidSize
879 3, // U S S Ok iff SrcSize != MidSize
881 2, // S U S Ok iff MidSize == DstSize
882 1, // S S U Always ok
883 1, // S S S Always ok
886 // Choose an action based on the current entry of the signtable that this
887 // cast of cast refers to...
888 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
889 switch (SignTable[Row]) {
890 case 0: return false; // Never ok
891 case 1: return true; // Always ok
892 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
893 case 3: // Ok iff SrcSize != MidSize
894 return SrcSize != MidSize || SrcTy == Type::BoolTy;
895 default: assert(0 && "Bad entry in sign table!");
900 // Otherwise, we cannot succeed. Specifically we do not want to allow things
901 // like: short -> ushort -> uint, because this can create wrong results if
902 // the input short is negative!
908 // CastInst simplification
910 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
911 Value *Src = CI.getOperand(0);
913 // If the user is casting a value to the same type, eliminate this cast
915 if (CI.getType() == Src->getType())
916 return ReplaceInstUsesWith(CI, Src);
918 // If casting the result of another cast instruction, try to eliminate this
921 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
922 if (isEliminableCastOfCast(CI, CSrc)) {
923 // This instruction now refers directly to the cast's src operand. This
924 // has a good chance of making CSrc dead.
925 CI.setOperand(0, CSrc->getOperand(0));
929 // If this is an A->B->A cast, and we are dealing with integral types, try
930 // to convert this into a logical 'and' instruction.
932 if (CSrc->getOperand(0)->getType() == CI.getType() &&
933 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
934 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
935 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
936 assert(CSrc->getType() != Type::ULongTy &&
937 "Cannot have type bigger than ulong!");
938 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
939 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
940 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
945 // If casting the result of a getelementptr instruction with no offset, turn
946 // this into a cast of the original pointer!
948 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
949 bool AllZeroOperands = true;
950 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
951 if (!isa<Constant>(GEP->getOperand(i)) ||
952 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
953 AllZeroOperands = false;
956 if (AllZeroOperands) {
957 CI.setOperand(0, GEP->getOperand(0));
962 // If this is a cast to bool (which is effectively a "!=0" test), then we can
963 // perform a few optimizations...
965 if (CI.getType() == Type::BoolTy) {
966 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Src)) {
967 Value *Op0 = BO->getOperand(0), *Op1 = BO->getOperand(1);
969 switch (BO->getOpcode()) {
970 case Instruction::Sub:
971 case Instruction::Xor:
972 // Replace (cast ([sub|xor] A, B) to bool) with (setne A, B)
973 return new SetCondInst(Instruction::SetNE, Op0, Op1);
975 // Replace (cast (add A, B) to bool) with (setne A, -B) if B is
976 // efficiently invertible, or if the add has just this one use.
977 case Instruction::Add:
978 if (Value *NegVal = dyn_castNegVal(Op1))
979 return new SetCondInst(Instruction::SetNE, Op0, NegVal);
980 else if (Value *NegVal = dyn_castNegVal(Op0))
981 return new SetCondInst(Instruction::SetNE, NegVal, Op1);
982 else if (BO->use_size() == 1) {
983 Instruction *Neg = BinaryOperator::createNeg(Op1, BO->getName());
985 InsertNewInstBefore(Neg, CI);
986 return new SetCondInst(Instruction::SetNE, Op0, Neg);
990 case Instruction::And:
991 // Replace (cast (and X, (1 << size(X)-1)) to bool) with x < 0,
992 // converting X to be a signed value as appropriate. Don't worry about
993 // bool values, as they will be optimized other ways if they occur in
994 // this configuration.
995 if (ConstantInt *CInt = dyn_cast<ConstantInt>(Op1))
996 if (isSignBit(CInt)) {
997 // If 'X' is not signed, insert a cast now...
998 if (!CInt->getType()->isSigned()) {
1000 switch (CInt->getType()->getPrimitiveID()) {
1001 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1002 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1003 case Type::UIntTyID: DestTy = Type::IntTy; break;
1004 case Type::ULongTyID: DestTy = Type::LongTy; break;
1005 default: assert(0 && "Invalid unsigned integer type!"); abort();
1007 CastInst *NewCI = new CastInst(Op0, DestTy,
1008 Op0->getName()+".signed");
1009 InsertNewInstBefore(NewCI, CI);
1012 return new SetCondInst(Instruction::SetLT, Op0,
1013 Constant::getNullValue(Op0->getType()));
1024 // CallInst simplification
1026 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1027 if (transformConstExprCastCall(&CI)) return 0;
1031 // InvokeInst simplification
1033 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1034 if (transformConstExprCastCall(&II)) return 0;
1038 // getPromotedType - Return the specified type promoted as it would be to pass
1039 // though a va_arg area...
1040 static const Type *getPromotedType(const Type *Ty) {
1041 switch (Ty->getPrimitiveID()) {
1042 case Type::SByteTyID:
1043 case Type::ShortTyID: return Type::IntTy;
1044 case Type::UByteTyID:
1045 case Type::UShortTyID: return Type::UIntTy;
1046 case Type::FloatTyID: return Type::DoubleTy;
1051 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1052 // attempt to move the cast to the arguments of the call/invoke.
1054 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1055 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1056 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1057 if (CE->getOpcode() != Instruction::Cast ||
1058 !isa<ConstantPointerRef>(CE->getOperand(0)))
1060 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1061 if (!isa<Function>(CPR->getValue())) return false;
1062 Function *Callee = cast<Function>(CPR->getValue());
1063 Instruction *Caller = CS.getInstruction();
1065 // Okay, this is a cast from a function to a different type. Unless doing so
1066 // would cause a type conversion of one of our arguments, change this call to
1067 // be a direct call with arguments casted to the appropriate types.
1069 const FunctionType *FT = Callee->getFunctionType();
1070 const Type *OldRetTy = Caller->getType();
1072 if (Callee->isExternal() &&
1073 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()))
1074 return false; // Cannot transform this return value...
1076 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1077 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1079 CallSite::arg_iterator AI = CS.arg_begin();
1080 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1081 const Type *ParamTy = FT->getParamType(i);
1082 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1083 if (Callee->isExternal() && !isConvertible) return false;
1086 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1087 Callee->isExternal())
1088 return false; // Do not delete arguments unless we have a function body...
1090 // Okay, we decided that this is a safe thing to do: go ahead and start
1091 // inserting cast instructions as necessary...
1092 std::vector<Value*> Args;
1093 Args.reserve(NumActualArgs);
1095 AI = CS.arg_begin();
1096 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1097 const Type *ParamTy = FT->getParamType(i);
1098 if ((*AI)->getType() == ParamTy) {
1099 Args.push_back(*AI);
1101 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1102 InsertNewInstBefore(Cast, *Caller);
1103 Args.push_back(Cast);
1107 // If the function takes more arguments than the call was taking, add them
1109 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1110 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1112 // If we are removing arguments to the function, emit an obnoxious warning...
1113 if (FT->getNumParams() < NumActualArgs)
1114 if (!FT->isVarArg()) {
1115 std::cerr << "WARNING: While resolving call to function '"
1116 << Callee->getName() << "' arguments were dropped!\n";
1118 // Add all of the arguments in their promoted form to the arg list...
1119 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1120 const Type *PTy = getPromotedType((*AI)->getType());
1121 if (PTy != (*AI)->getType()) {
1122 // Must promote to pass through va_arg area!
1123 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1124 InsertNewInstBefore(Cast, *Caller);
1125 Args.push_back(Cast);
1127 Args.push_back(*AI);
1132 if (FT->getReturnType() == Type::VoidTy)
1133 Caller->setName(""); // Void type should not have a name...
1136 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1137 NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(),
1138 Args, Caller->getName(), Caller);
1140 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1143 // Insert a cast of the return type as necessary...
1145 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1146 if (NV->getType() != Type::VoidTy) {
1147 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1148 InsertNewInstBefore(NC, *Caller);
1149 AddUsesToWorkList(*Caller);
1151 NV = Constant::getNullValue(Caller->getType());
1155 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1156 Caller->replaceAllUsesWith(NV);
1157 Caller->getParent()->getInstList().erase(Caller);
1158 removeFromWorkList(Caller);
1164 // PHINode simplification
1166 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
1167 // If the PHI node only has one incoming value, eliminate the PHI node...
1168 if (PN.getNumIncomingValues() == 1)
1169 return ReplaceInstUsesWith(PN, PN.getIncomingValue(0));
1171 // Otherwise if all of the incoming values are the same for the PHI, replace
1172 // the PHI node with the incoming value.
1175 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
1176 if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself...
1177 if (InVal && PN.getIncomingValue(i) != InVal)
1178 return 0; // Not the same, bail out.
1180 InVal = PN.getIncomingValue(i);
1182 // The only case that could cause InVal to be null is if we have a PHI node
1183 // that only has entries for itself. In this case, there is no entry into the
1184 // loop, so kill the PHI.
1186 if (InVal == 0) InVal = Constant::getNullValue(PN.getType());
1188 // All of the incoming values are the same, replace the PHI node now.
1189 return ReplaceInstUsesWith(PN, InVal);
1193 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1194 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
1195 // If so, eliminate the noop.
1196 if ((GEP.getNumOperands() == 2 &&
1197 GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
1198 GEP.getNumOperands() == 1)
1199 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
1201 // Combine Indices - If the source pointer to this getelementptr instruction
1202 // is a getelementptr instruction, combine the indices of the two
1203 // getelementptr instructions into a single instruction.
1205 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
1206 std::vector<Value *> Indices;
1208 // Can we combine the two pointer arithmetics offsets?
1209 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
1210 isa<Constant>(GEP.getOperand(1))) {
1211 // Replace: gep (gep %P, long C1), long C2, ...
1212 // With: gep %P, long (C1+C2), ...
1213 Value *Sum = ConstantExpr::get(Instruction::Add,
1214 cast<Constant>(Src->getOperand(1)),
1215 cast<Constant>(GEP.getOperand(1)));
1216 assert(Sum && "Constant folding of longs failed!?");
1217 GEP.setOperand(0, Src->getOperand(0));
1218 GEP.setOperand(1, Sum);
1219 AddUsesToWorkList(*Src); // Reduce use count of Src
1221 } else if (Src->getNumOperands() == 2) {
1222 // Replace: gep (gep %P, long B), long A, ...
1223 // With: T = long A+B; gep %P, T, ...
1225 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
1227 Src->getName()+".sum", &GEP);
1228 GEP.setOperand(0, Src->getOperand(0));
1229 GEP.setOperand(1, Sum);
1230 WorkList.push_back(cast<Instruction>(Sum));
1232 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
1233 Src->getNumOperands() != 1) {
1234 // Otherwise we can do the fold if the first index of the GEP is a zero
1235 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
1236 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
1237 } else if (Src->getOperand(Src->getNumOperands()-1) ==
1238 Constant::getNullValue(Type::LongTy)) {
1239 // If the src gep ends with a constant array index, merge this get into
1240 // it, even if we have a non-zero array index.
1241 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
1242 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
1245 if (!Indices.empty())
1246 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
1248 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
1249 // GEP of global variable. If all of the indices for this GEP are
1250 // constants, we can promote this to a constexpr instead of an instruction.
1252 // Scan for nonconstants...
1253 std::vector<Constant*> Indices;
1254 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
1255 for (; I != E && isa<Constant>(*I); ++I)
1256 Indices.push_back(cast<Constant>(*I));
1258 if (I == E) { // If they are all constants...
1260 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
1262 // Replace all uses of the GEP with the new constexpr...
1263 return ReplaceInstUsesWith(GEP, CE);
1270 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
1271 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
1272 if (AI.isArrayAllocation()) // Check C != 1
1273 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
1274 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
1275 AllocationInst *New = 0;
1277 // Create and insert the replacement instruction...
1278 if (isa<MallocInst>(AI))
1279 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
1281 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
1282 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
1285 // Scan to the end of the allocation instructions, to skip over a block of
1286 // allocas if possible...
1288 BasicBlock::iterator It = New;
1289 while (isa<AllocationInst>(*It)) ++It;
1291 // Now that I is pointing to the first non-allocation-inst in the block,
1292 // insert our getelementptr instruction...
1294 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
1295 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
1297 // Now make everything use the getelementptr instead of the original
1299 ReplaceInstUsesWith(AI, V);
1305 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
1306 /// constantexpr, return the constant value being addressed by the constant
1307 /// expression, or null if something is funny.
1309 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
1310 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
1311 return 0; // Do not allow stepping over the value!
1313 // Loop over all of the operands, tracking down which value we are
1315 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
1316 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
1317 ConstantStruct *CS = cast<ConstantStruct>(C);
1318 if (CU->getValue() >= CS->getValues().size()) return 0;
1319 C = cast<Constant>(CS->getValues()[CU->getValue()]);
1320 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
1321 ConstantArray *CA = cast<ConstantArray>(C);
1322 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
1323 C = cast<Constant>(CA->getValues()[CS->getValue()]);
1329 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
1330 Value *Op = LI.getOperand(0);
1331 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
1332 Op = CPR->getValue();
1334 // Instcombine load (constant global) into the value loaded...
1335 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
1336 if (GV->isConstant() && !GV->isExternal())
1337 return ReplaceInstUsesWith(LI, GV->getInitializer());
1339 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
1340 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
1341 if (CE->getOpcode() == Instruction::GetElementPtr)
1342 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
1343 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
1344 if (GV->isConstant() && !GV->isExternal())
1345 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
1346 return ReplaceInstUsesWith(LI, V);
1351 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
1352 // Change br (not X), label True, label False to: br X, label False, True
1353 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
1354 if (Value *V = dyn_castNotVal(BI.getCondition())) {
1355 BasicBlock *TrueDest = BI.getSuccessor(0);
1356 BasicBlock *FalseDest = BI.getSuccessor(1);
1357 // Swap Destinations and condition...
1359 BI.setSuccessor(0, FalseDest);
1360 BI.setSuccessor(1, TrueDest);
1367 void InstCombiner::removeFromWorkList(Instruction *I) {
1368 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
1372 bool InstCombiner::runOnFunction(Function &F) {
1373 bool Changed = false;
1375 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
1377 while (!WorkList.empty()) {
1378 Instruction *I = WorkList.back(); // Get an instruction from the worklist
1379 WorkList.pop_back();
1381 // Check to see if we can DCE or ConstantPropagate the instruction...
1382 // Check to see if we can DIE the instruction...
1383 if (isInstructionTriviallyDead(I)) {
1384 // Add operands to the worklist...
1385 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
1386 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
1387 WorkList.push_back(Op);
1390 BasicBlock::iterator BBI = I;
1391 if (dceInstruction(BBI)) {
1392 removeFromWorkList(I);
1397 // Instruction isn't dead, see if we can constant propagate it...
1398 if (Constant *C = ConstantFoldInstruction(I)) {
1399 // Add operands to the worklist...
1400 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
1401 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
1402 WorkList.push_back(Op);
1403 ReplaceInstUsesWith(*I, C);
1406 BasicBlock::iterator BBI = I;
1407 if (dceInstruction(BBI)) {
1408 removeFromWorkList(I);
1413 // Now that we have an instruction, try combining it to simplify it...
1414 if (Instruction *Result = visit(*I)) {
1416 // Should we replace the old instruction with a new one?
1418 // Instructions can end up on the worklist more than once. Make sure
1419 // we do not process an instruction that has been deleted.
1420 removeFromWorkList(I);
1421 ReplaceInstWithInst(I, Result);
1423 BasicBlock::iterator II = I;
1425 // If the instruction was modified, it's possible that it is now dead.
1426 // if so, remove it.
1427 if (dceInstruction(II)) {
1428 // Instructions may end up in the worklist more than once. Erase them
1430 removeFromWorkList(I);
1436 WorkList.push_back(Result);
1437 AddUsesToWorkList(*Result);
1446 Pass *createInstructionCombiningPass() {
1447 return new InstCombiner();