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 = (int64_t)cast<ConstantInt>(CI)->getRawValue();
375 case -1: // X * -1 -> -X
376 return BinaryOperator::createNeg(Op0, I.getName());
378 return ReplaceInstUsesWith(I, Op1); // Eliminate 'mul double %X, 0'
380 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul int %X, 1'
381 case 2: // Convert 'mul int %X, 2' to 'add int %X, %X'
382 return BinaryOperator::create(Instruction::Add, Op0, Op0, I.getName());
385 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
386 return new ShiftInst(Instruction::Shl, Op0,
387 ConstantUInt::get(Type::UByteTy, C));
389 ConstantFP *Op1F = cast<ConstantFP>(Op1);
390 if (Op1F->isNullValue())
391 return ReplaceInstUsesWith(I, Op1);
393 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
394 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
395 if (Op1F->getValue() == 1.0)
396 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
400 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
401 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
402 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
404 return Changed ? &I : 0;
407 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
409 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
410 if (RHS->equalsInt(1))
411 return ReplaceInstUsesWith(I, I.getOperand(0));
413 // Check to see if this is an unsigned division with an exact power of 2,
414 // if so, convert to a right shift.
415 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
416 if (uint64_t Val = C->getValue()) // Don't break X / 0
417 if (uint64_t C = Log2(Val))
418 return new ShiftInst(Instruction::Shr, I.getOperand(0),
419 ConstantUInt::get(Type::UByteTy, C));
422 // 0 / X == 0, we don't need to preserve faults!
423 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
424 if (LHS->equalsInt(0))
425 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
431 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
432 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
433 if (RHS->equalsInt(1)) // X % 1 == 0
434 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
436 // Check to see if this is an unsigned remainder with an exact power of 2,
437 // if so, convert to a bitwise and.
438 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
439 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
441 return BinaryOperator::create(Instruction::And, I.getOperand(0),
442 ConstantUInt::get(I.getType(), Val-1));
445 // 0 % X == 0, we don't need to preserve faults!
446 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
447 if (LHS->equalsInt(0))
448 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
453 // isMaxValueMinusOne - return true if this is Max-1
454 static bool isMaxValueMinusOne(const ConstantInt *C) {
455 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
456 // Calculate -1 casted to the right type...
457 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
458 uint64_t Val = ~0ULL; // All ones
459 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
460 return CU->getValue() == Val-1;
463 const ConstantSInt *CS = cast<ConstantSInt>(C);
465 // Calculate 0111111111..11111
466 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
467 int64_t Val = INT64_MAX; // All ones
468 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
469 return CS->getValue() == Val-1;
472 // isMinValuePlusOne - return true if this is Min+1
473 static bool isMinValuePlusOne(const ConstantInt *C) {
474 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
475 return CU->getValue() == 1;
477 const ConstantSInt *CS = cast<ConstantSInt>(C);
479 // Calculate 1111111111000000000000
480 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
481 int64_t Val = -1; // All ones
482 Val <<= TypeBits-1; // Shift over to the right spot
483 return CS->getValue() == Val+1;
487 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
488 bool Changed = SimplifyCommutative(I);
489 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
491 // and X, X = X and X, 0 == 0
492 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
493 return ReplaceInstUsesWith(I, Op1);
496 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
497 if (RHS->isAllOnesValue())
498 return ReplaceInstUsesWith(I, Op0);
500 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
501 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
502 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
503 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
504 std::string Op0Name = Op0I->getName(); Op0I->setName("");
505 Instruction *And = BinaryOperator::create(Instruction::And,
506 Op0I->getOperand(0), RHS,
508 InsertNewInstBefore(And, I);
509 return BinaryOperator::create(Instruction::Xor, And, *RHS & *Op0CI);
513 Value *Op0NotVal = dyn_castNotVal(Op0);
514 Value *Op1NotVal = dyn_castNotVal(Op1);
516 // (~A & ~B) == (~(A | B)) - Demorgan's Law
517 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
518 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
519 Op1NotVal,I.getName()+".demorgan");
520 InsertNewInstBefore(Or, I);
521 return BinaryOperator::createNot(Or);
524 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
525 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
527 return Changed ? &I : 0;
532 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
533 bool Changed = SimplifyCommutative(I);
534 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
536 // or X, X = X or X, 0 == X
537 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
538 return ReplaceInstUsesWith(I, Op0);
541 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1))
542 if (RHS->isAllOnesValue())
543 return ReplaceInstUsesWith(I, Op1);
545 Value *Op0NotVal = dyn_castNotVal(Op0);
546 Value *Op1NotVal = dyn_castNotVal(Op1);
548 if (Op1 == Op0NotVal) // ~A | A == -1
549 return ReplaceInstUsesWith(I,
550 ConstantIntegral::getAllOnesValue(I.getType()));
552 if (Op0 == Op1NotVal) // A | ~A == -1
553 return ReplaceInstUsesWith(I,
554 ConstantIntegral::getAllOnesValue(I.getType()));
556 // (~A | ~B) == (~(A & B)) - Demorgan's Law
557 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
558 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
559 Op1NotVal,I.getName()+".demorgan",
561 WorkList.push_back(And);
562 return BinaryOperator::createNot(And);
565 return Changed ? &I : 0;
570 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
571 bool Changed = SimplifyCommutative(I);
572 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
576 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
578 if (ConstantIntegral *Op1C = dyn_cast<ConstantIntegral>(Op1)) {
580 if (Op1C->isNullValue())
581 return ReplaceInstUsesWith(I, Op0);
583 // Is this a "NOT" instruction?
584 if (Op1C->isAllOnesValue()) {
585 // xor (xor X, -1), -1 = not (not X) = X
586 if (Value *X = dyn_castNotVal(Op0))
587 return ReplaceInstUsesWith(I, X);
589 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
590 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0))
591 if (SCI->use_size() == 1)
592 return new SetCondInst(SCI->getInverseCondition(),
593 SCI->getOperand(0), SCI->getOperand(1));
597 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
599 return ReplaceInstUsesWith(I,
600 ConstantIntegral::getAllOnesValue(I.getType()));
602 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
604 return ReplaceInstUsesWith(I,
605 ConstantIntegral::getAllOnesValue(I.getType()));
607 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
608 if (Op1I->getOpcode() == Instruction::Or)
609 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
610 cast<BinaryOperator>(Op1I)->swapOperands();
613 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
618 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
619 if (Op0I->getOpcode() == Instruction::Or && Op0I->use_size() == 1) {
620 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
621 cast<BinaryOperator>(Op0I)->swapOperands();
622 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
623 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
624 WorkList.push_back(cast<Instruction>(NotB));
625 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
630 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
631 if (Constant *C1 = dyn_castMaskingAnd(Op0))
632 if (Constant *C2 = dyn_castMaskingAnd(Op1))
633 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
634 return BinaryOperator::create(Instruction::Or, Op0, Op1);
636 return Changed ? &I : 0;
639 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
640 static Constant *AddOne(ConstantInt *C) {
641 Constant *Result = ConstantExpr::get(Instruction::Add, C,
642 ConstantInt::get(C->getType(), 1));
643 assert(Result && "Constant folding integer addition failed!");
646 static Constant *SubOne(ConstantInt *C) {
647 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
648 ConstantInt::get(C->getType(), 1));
649 assert(Result && "Constant folding integer addition failed!");
653 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
654 // true when both operands are equal...
656 static bool isTrueWhenEqual(Instruction &I) {
657 return I.getOpcode() == Instruction::SetEQ ||
658 I.getOpcode() == Instruction::SetGE ||
659 I.getOpcode() == Instruction::SetLE;
662 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
663 bool Changed = SimplifyCommutative(I);
664 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
665 const Type *Ty = Op0->getType();
669 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
671 // setcc <global*>, 0 - Global value addresses are never null!
672 if (isa<GlobalValue>(Op0) && isa<ConstantPointerNull>(Op1))
673 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
675 // setcc's with boolean values can always be turned into bitwise operations
676 if (Ty == Type::BoolTy) {
677 // If this is <, >, or !=, we can change this into a simple xor instruction
678 if (!isTrueWhenEqual(I))
679 return BinaryOperator::create(Instruction::Xor, Op0, Op1, I.getName());
681 // Otherwise we need to make a temporary intermediate instruction and insert
682 // it into the instruction stream. This is what we are after:
684 // seteq bool %A, %B -> ~(A^B)
685 // setle bool %A, %B -> ~A | B
686 // setge bool %A, %B -> A | ~B
688 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
689 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
691 InsertNewInstBefore(Xor, I);
692 return BinaryOperator::createNot(Xor, I.getName());
695 // Handle the setXe cases...
696 assert(I.getOpcode() == Instruction::SetGE ||
697 I.getOpcode() == Instruction::SetLE);
699 if (I.getOpcode() == Instruction::SetGE)
700 std::swap(Op0, Op1); // Change setge -> setle
702 // Now we just have the SetLE case.
703 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
704 InsertNewInstBefore(Not, I);
705 return BinaryOperator::create(Instruction::Or, Not, Op1, I.getName());
708 // Check to see if we are doing one of many comparisons against constant
709 // integers at the end of their ranges...
711 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
712 // Simplify seteq and setne instructions...
713 if (I.getOpcode() == Instruction::SetEQ ||
714 I.getOpcode() == Instruction::SetNE) {
715 bool isSetNE = I.getOpcode() == Instruction::SetNE;
717 if (CI->isNullValue()) { // Simplify [seteq|setne] X, 0
718 CastInst *Val = new CastInst(Op0, Type::BoolTy, I.getName()+".not");
719 if (isSetNE) return Val;
721 // seteq X, 0 -> not (cast X to bool)
722 InsertNewInstBefore(Val, I);
723 return BinaryOperator::createNot(Val, I.getName());
726 // If the first operand is (and|or|xor) with a constant, and the second
727 // operand is a constant, simplify a bit.
728 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
729 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1)))
730 if (BO->getOpcode() == Instruction::Or) {
731 // If bits are being or'd in that are not present in the constant we
732 // are comparing against, then the comparison could never succeed!
733 if (!(*BOC & *~*CI)->isNullValue())
734 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
735 } else if (BO->getOpcode() == Instruction::And) {
736 // If bits are being compared against that are and'd out, then the
737 // comparison can never succeed!
738 if (!(*CI & *~*BOC)->isNullValue())
739 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
740 } else if (BO->getOpcode() == Instruction::Xor) {
741 // For the xor case, we can always just xor the two constants
742 // together, potentially eliminating the explicit xor.
743 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
748 // Check to see if we are comparing against the minimum or maximum value...
749 if (CI->isMinValue()) {
750 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
751 return ReplaceInstUsesWith(I, ConstantBool::False);
752 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
753 return ReplaceInstUsesWith(I, ConstantBool::True);
754 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
755 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
756 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
757 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
759 } else if (CI->isMaxValue()) {
760 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
761 return ReplaceInstUsesWith(I, ConstantBool::False);
762 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
763 return ReplaceInstUsesWith(I, ConstantBool::True);
764 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
765 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
766 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
767 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
769 // Comparing against a value really close to min or max?
770 } else if (isMinValuePlusOne(CI)) {
771 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
772 return BinaryOperator::create(Instruction::SetEQ, Op0,
773 SubOne(CI), I.getName());
774 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
775 return BinaryOperator::create(Instruction::SetNE, Op0,
776 SubOne(CI), I.getName());
778 } else if (isMaxValueMinusOne(CI)) {
779 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
780 return BinaryOperator::create(Instruction::SetEQ, Op0,
781 AddOne(CI), I.getName());
782 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
783 return BinaryOperator::create(Instruction::SetNE, Op0,
784 AddOne(CI), I.getName());
788 return Changed ? &I : 0;
793 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
794 assert(I.getOperand(1)->getType() == Type::UByteTy);
795 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
797 // shl X, 0 == X and shr X, 0 == X
798 // shl 0, X == 0 and shr 0, X == 0
799 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
800 Op0 == Constant::getNullValue(Op0->getType()))
801 return ReplaceInstUsesWith(I, Op0);
803 // If this is a shift of a shift, see if we can fold the two together...
804 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0)) {
805 if (isa<Constant>(Op1) && isa<Constant>(Op0SI->getOperand(1))) {
806 ConstantUInt *ShiftAmt1C = cast<ConstantUInt>(Op0SI->getOperand(1));
807 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
808 unsigned ShiftAmt2 = cast<ConstantUInt>(Op1)->getValue();
810 // Check for (A << c1) << c2 and (A >> c1) >> c2
811 if (I.getOpcode() == Op0SI->getOpcode()) {
812 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
813 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
814 ConstantUInt::get(Type::UByteTy, Amt));
817 if (I.getType()->isUnsigned()) { // Check for (A << c1) >> c2 or visaversa
818 // Calculate bitmask for what gets shifted off the edge...
819 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
820 if (I.getOpcode() == Instruction::Shr)
821 C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
823 C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
826 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
827 C, Op0SI->getOperand(0)->getName()+".mask",&I);
828 WorkList.push_back(Mask);
830 // Figure out what flavor of shift we should use...
831 if (ShiftAmt1 == ShiftAmt2)
832 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
833 else if (ShiftAmt1 < ShiftAmt2) {
834 return new ShiftInst(I.getOpcode(), Mask,
835 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
837 return new ShiftInst(Op0SI->getOpcode(), Mask,
838 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
844 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr of
847 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
848 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
849 if (CUI->getValue() >= TypeBits &&
850 (!Op0->getType()->isSigned() || I.getOpcode() == Instruction::Shl))
851 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
853 // Check to see if we are shifting left by 1. If so, turn it into an add
855 if (I.getOpcode() == Instruction::Shl && CUI->equalsInt(1))
856 // Convert 'shl int %X, 1' to 'add int %X, %X'
857 return BinaryOperator::create(Instruction::Add, Op0, Op0, I.getName());
861 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
862 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
863 if (I.getOpcode() == Instruction::Shr && CSI->isAllOnesValue())
864 return ReplaceInstUsesWith(I, CSI);
870 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
873 static inline bool isEliminableCastOfCast(const CastInst &CI,
874 const CastInst *CSrc) {
875 assert(CI.getOperand(0) == CSrc);
876 const Type *SrcTy = CSrc->getOperand(0)->getType();
877 const Type *MidTy = CSrc->getType();
878 const Type *DstTy = CI.getType();
880 // It is legal to eliminate the instruction if casting A->B->A if the sizes
881 // are identical and the bits don't get reinterpreted (for example
882 // int->float->int would not be allowed)
883 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
886 // Allow free casting and conversion of sizes as long as the sign doesn't
888 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
889 unsigned SrcSize = SrcTy->getPrimitiveSize();
890 unsigned MidSize = MidTy->getPrimitiveSize();
891 unsigned DstSize = DstTy->getPrimitiveSize();
893 // Cases where we are monotonically decreasing the size of the type are
894 // always ok, regardless of what sign changes are going on.
896 if (SrcSize >= MidSize && MidSize >= DstSize)
899 // Cases where the source and destination type are the same, but the middle
900 // type is bigger are noops.
902 if (SrcSize == DstSize && MidSize > SrcSize)
905 // If we are monotonically growing, things are more complex.
907 if (SrcSize <= MidSize && MidSize <= DstSize) {
908 // We have eight combinations of signedness to worry about. Here's the
910 static const int SignTable[8] = {
911 // CODE, SrcSigned, MidSigned, DstSigned, Comment
912 1, // U U U Always ok
913 1, // U U S Always ok
914 3, // U S U Ok iff SrcSize != MidSize
915 3, // U S S Ok iff SrcSize != MidSize
917 2, // S U S Ok iff MidSize == DstSize
918 1, // S S U Always ok
919 1, // S S S Always ok
922 // Choose an action based on the current entry of the signtable that this
923 // cast of cast refers to...
924 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
925 switch (SignTable[Row]) {
926 case 0: return false; // Never ok
927 case 1: return true; // Always ok
928 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
929 case 3: // Ok iff SrcSize != MidSize
930 return SrcSize != MidSize || SrcTy == Type::BoolTy;
931 default: assert(0 && "Bad entry in sign table!");
936 // Otherwise, we cannot succeed. Specifically we do not want to allow things
937 // like: short -> ushort -> uint, because this can create wrong results if
938 // the input short is negative!
944 // CastInst simplification
946 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
947 Value *Src = CI.getOperand(0);
949 // If the user is casting a value to the same type, eliminate this cast
951 if (CI.getType() == Src->getType())
952 return ReplaceInstUsesWith(CI, Src);
954 // If casting the result of another cast instruction, try to eliminate this
957 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
958 if (isEliminableCastOfCast(CI, CSrc)) {
959 // This instruction now refers directly to the cast's src operand. This
960 // has a good chance of making CSrc dead.
961 CI.setOperand(0, CSrc->getOperand(0));
965 // If this is an A->B->A cast, and we are dealing with integral types, try
966 // to convert this into a logical 'and' instruction.
968 if (CSrc->getOperand(0)->getType() == CI.getType() &&
969 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
970 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
971 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
972 assert(CSrc->getType() != Type::ULongTy &&
973 "Cannot have type bigger than ulong!");
974 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
975 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
976 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
981 // If casting the result of a getelementptr instruction with no offset, turn
982 // this into a cast of the original pointer!
984 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
985 bool AllZeroOperands = true;
986 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
987 if (!isa<Constant>(GEP->getOperand(i)) ||
988 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
989 AllZeroOperands = false;
992 if (AllZeroOperands) {
993 CI.setOperand(0, GEP->getOperand(0));
998 // If this is a cast to bool (which is effectively a "!=0" test), then we can
999 // perform a few optimizations...
1001 if (CI.getType() == Type::BoolTy) {
1002 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Src)) {
1003 Value *Op0 = BO->getOperand(0), *Op1 = BO->getOperand(1);
1005 switch (BO->getOpcode()) {
1006 case Instruction::Sub:
1007 case Instruction::Xor:
1008 // Replace (cast ([sub|xor] A, B) to bool) with (setne A, B)
1009 return new SetCondInst(Instruction::SetNE, Op0, Op1);
1011 // Replace (cast (add A, B) to bool) with (setne A, -B) if B is
1012 // efficiently invertible, or if the add has just this one use.
1013 case Instruction::Add:
1014 if (Value *NegVal = dyn_castNegVal(Op1))
1015 return new SetCondInst(Instruction::SetNE, Op0, NegVal);
1016 else if (Value *NegVal = dyn_castNegVal(Op0))
1017 return new SetCondInst(Instruction::SetNE, NegVal, Op1);
1018 else if (BO->use_size() == 1) {
1019 Instruction *Neg = BinaryOperator::createNeg(Op1, BO->getName());
1021 InsertNewInstBefore(Neg, CI);
1022 return new SetCondInst(Instruction::SetNE, Op0, Neg);
1026 case Instruction::And:
1027 // Replace (cast (and X, (1 << size(X)-1)) to bool) with x < 0,
1028 // converting X to be a signed value as appropriate. Don't worry about
1029 // bool values, as they will be optimized other ways if they occur in
1030 // this configuration.
1031 if (ConstantInt *CInt = dyn_cast<ConstantInt>(Op1))
1032 if (isSignBit(CInt)) {
1033 // If 'X' is not signed, insert a cast now...
1034 if (!CInt->getType()->isSigned()) {
1036 switch (CInt->getType()->getPrimitiveID()) {
1037 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1038 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1039 case Type::UIntTyID: DestTy = Type::IntTy; break;
1040 case Type::ULongTyID: DestTy = Type::LongTy; break;
1041 default: assert(0 && "Invalid unsigned integer type!"); abort();
1043 CastInst *NewCI = new CastInst(Op0, DestTy,
1044 Op0->getName()+".signed");
1045 InsertNewInstBefore(NewCI, CI);
1048 return new SetCondInst(Instruction::SetLT, Op0,
1049 Constant::getNullValue(Op0->getType()));
1060 // CallInst simplification
1062 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1063 if (transformConstExprCastCall(&CI)) return 0;
1067 // InvokeInst simplification
1069 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1070 if (transformConstExprCastCall(&II)) return 0;
1074 // getPromotedType - Return the specified type promoted as it would be to pass
1075 // though a va_arg area...
1076 static const Type *getPromotedType(const Type *Ty) {
1077 switch (Ty->getPrimitiveID()) {
1078 case Type::SByteTyID:
1079 case Type::ShortTyID: return Type::IntTy;
1080 case Type::UByteTyID:
1081 case Type::UShortTyID: return Type::UIntTy;
1082 case Type::FloatTyID: return Type::DoubleTy;
1087 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1088 // attempt to move the cast to the arguments of the call/invoke.
1090 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1091 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1092 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1093 if (CE->getOpcode() != Instruction::Cast ||
1094 !isa<ConstantPointerRef>(CE->getOperand(0)))
1096 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1097 if (!isa<Function>(CPR->getValue())) return false;
1098 Function *Callee = cast<Function>(CPR->getValue());
1099 Instruction *Caller = CS.getInstruction();
1101 // Okay, this is a cast from a function to a different type. Unless doing so
1102 // would cause a type conversion of one of our arguments, change this call to
1103 // be a direct call with arguments casted to the appropriate types.
1105 const FunctionType *FT = Callee->getFunctionType();
1106 const Type *OldRetTy = Caller->getType();
1108 if (Callee->isExternal() &&
1109 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()))
1110 return false; // Cannot transform this return value...
1112 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1113 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1115 CallSite::arg_iterator AI = CS.arg_begin();
1116 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1117 const Type *ParamTy = FT->getParamType(i);
1118 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1119 if (Callee->isExternal() && !isConvertible) return false;
1122 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1123 Callee->isExternal())
1124 return false; // Do not delete arguments unless we have a function body...
1126 // Okay, we decided that this is a safe thing to do: go ahead and start
1127 // inserting cast instructions as necessary...
1128 std::vector<Value*> Args;
1129 Args.reserve(NumActualArgs);
1131 AI = CS.arg_begin();
1132 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1133 const Type *ParamTy = FT->getParamType(i);
1134 if ((*AI)->getType() == ParamTy) {
1135 Args.push_back(*AI);
1137 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1138 InsertNewInstBefore(Cast, *Caller);
1139 Args.push_back(Cast);
1143 // If the function takes more arguments than the call was taking, add them
1145 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1146 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1148 // If we are removing arguments to the function, emit an obnoxious warning...
1149 if (FT->getNumParams() < NumActualArgs)
1150 if (!FT->isVarArg()) {
1151 std::cerr << "WARNING: While resolving call to function '"
1152 << Callee->getName() << "' arguments were dropped!\n";
1154 // Add all of the arguments in their promoted form to the arg list...
1155 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1156 const Type *PTy = getPromotedType((*AI)->getType());
1157 if (PTy != (*AI)->getType()) {
1158 // Must promote to pass through va_arg area!
1159 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1160 InsertNewInstBefore(Cast, *Caller);
1161 Args.push_back(Cast);
1163 Args.push_back(*AI);
1168 if (FT->getReturnType() == Type::VoidTy)
1169 Caller->setName(""); // Void type should not have a name...
1172 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1173 NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(),
1174 Args, Caller->getName(), Caller);
1176 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1179 // Insert a cast of the return type as necessary...
1181 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1182 if (NV->getType() != Type::VoidTy) {
1183 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1184 InsertNewInstBefore(NC, *Caller);
1185 AddUsesToWorkList(*Caller);
1187 NV = Constant::getNullValue(Caller->getType());
1191 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1192 Caller->replaceAllUsesWith(NV);
1193 Caller->getParent()->getInstList().erase(Caller);
1194 removeFromWorkList(Caller);
1200 // PHINode simplification
1202 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
1203 // If the PHI node only has one incoming value, eliminate the PHI node...
1204 if (PN.getNumIncomingValues() == 1)
1205 return ReplaceInstUsesWith(PN, PN.getIncomingValue(0));
1207 // Otherwise if all of the incoming values are the same for the PHI, replace
1208 // the PHI node with the incoming value.
1211 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
1212 if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself...
1213 if (InVal && PN.getIncomingValue(i) != InVal)
1214 return 0; // Not the same, bail out.
1216 InVal = PN.getIncomingValue(i);
1218 // The only case that could cause InVal to be null is if we have a PHI node
1219 // that only has entries for itself. In this case, there is no entry into the
1220 // loop, so kill the PHI.
1222 if (InVal == 0) InVal = Constant::getNullValue(PN.getType());
1224 // All of the incoming values are the same, replace the PHI node now.
1225 return ReplaceInstUsesWith(PN, InVal);
1229 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1230 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
1231 // If so, eliminate the noop.
1232 if ((GEP.getNumOperands() == 2 &&
1233 GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
1234 GEP.getNumOperands() == 1)
1235 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
1237 // Combine Indices - If the source pointer to this getelementptr instruction
1238 // is a getelementptr instruction, combine the indices of the two
1239 // getelementptr instructions into a single instruction.
1241 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
1242 std::vector<Value *> Indices;
1244 // Can we combine the two pointer arithmetics offsets?
1245 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
1246 isa<Constant>(GEP.getOperand(1))) {
1247 // Replace: gep (gep %P, long C1), long C2, ...
1248 // With: gep %P, long (C1+C2), ...
1249 Value *Sum = ConstantExpr::get(Instruction::Add,
1250 cast<Constant>(Src->getOperand(1)),
1251 cast<Constant>(GEP.getOperand(1)));
1252 assert(Sum && "Constant folding of longs failed!?");
1253 GEP.setOperand(0, Src->getOperand(0));
1254 GEP.setOperand(1, Sum);
1255 AddUsesToWorkList(*Src); // Reduce use count of Src
1257 } else if (Src->getNumOperands() == 2) {
1258 // Replace: gep (gep %P, long B), long A, ...
1259 // With: T = long A+B; gep %P, T, ...
1261 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
1263 Src->getName()+".sum", &GEP);
1264 GEP.setOperand(0, Src->getOperand(0));
1265 GEP.setOperand(1, Sum);
1266 WorkList.push_back(cast<Instruction>(Sum));
1268 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
1269 Src->getNumOperands() != 1) {
1270 // Otherwise we can do the fold if the first index of the GEP is a zero
1271 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
1272 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
1273 } else if (Src->getOperand(Src->getNumOperands()-1) ==
1274 Constant::getNullValue(Type::LongTy)) {
1275 // If the src gep ends with a constant array index, merge this get into
1276 // it, even if we have a non-zero array index.
1277 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
1278 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
1281 if (!Indices.empty())
1282 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
1284 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
1285 // GEP of global variable. If all of the indices for this GEP are
1286 // constants, we can promote this to a constexpr instead of an instruction.
1288 // Scan for nonconstants...
1289 std::vector<Constant*> Indices;
1290 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
1291 for (; I != E && isa<Constant>(*I); ++I)
1292 Indices.push_back(cast<Constant>(*I));
1294 if (I == E) { // If they are all constants...
1296 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
1298 // Replace all uses of the GEP with the new constexpr...
1299 return ReplaceInstUsesWith(GEP, CE);
1306 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
1307 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
1308 if (AI.isArrayAllocation()) // Check C != 1
1309 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
1310 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
1311 AllocationInst *New = 0;
1313 // Create and insert the replacement instruction...
1314 if (isa<MallocInst>(AI))
1315 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
1317 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
1318 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
1321 // Scan to the end of the allocation instructions, to skip over a block of
1322 // allocas if possible...
1324 BasicBlock::iterator It = New;
1325 while (isa<AllocationInst>(*It)) ++It;
1327 // Now that I is pointing to the first non-allocation-inst in the block,
1328 // insert our getelementptr instruction...
1330 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
1331 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
1333 // Now make everything use the getelementptr instead of the original
1335 ReplaceInstUsesWith(AI, V);
1341 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
1342 /// constantexpr, return the constant value being addressed by the constant
1343 /// expression, or null if something is funny.
1345 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
1346 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
1347 return 0; // Do not allow stepping over the value!
1349 // Loop over all of the operands, tracking down which value we are
1351 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
1352 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
1353 ConstantStruct *CS = cast<ConstantStruct>(C);
1354 if (CU->getValue() >= CS->getValues().size()) return 0;
1355 C = cast<Constant>(CS->getValues()[CU->getValue()]);
1356 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
1357 ConstantArray *CA = cast<ConstantArray>(C);
1358 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
1359 C = cast<Constant>(CA->getValues()[CS->getValue()]);
1365 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
1366 Value *Op = LI.getOperand(0);
1367 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
1368 Op = CPR->getValue();
1370 // Instcombine load (constant global) into the value loaded...
1371 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
1372 if (GV->isConstant() && !GV->isExternal())
1373 return ReplaceInstUsesWith(LI, GV->getInitializer());
1375 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
1376 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
1377 if (CE->getOpcode() == Instruction::GetElementPtr)
1378 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
1379 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
1380 if (GV->isConstant() && !GV->isExternal())
1381 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
1382 return ReplaceInstUsesWith(LI, V);
1387 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
1388 // Change br (not X), label True, label False to: br X, label False, True
1389 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
1390 if (Value *V = dyn_castNotVal(BI.getCondition())) {
1391 BasicBlock *TrueDest = BI.getSuccessor(0);
1392 BasicBlock *FalseDest = BI.getSuccessor(1);
1393 // Swap Destinations and condition...
1395 BI.setSuccessor(0, FalseDest);
1396 BI.setSuccessor(1, TrueDest);
1403 void InstCombiner::removeFromWorkList(Instruction *I) {
1404 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
1408 bool InstCombiner::runOnFunction(Function &F) {
1409 bool Changed = false;
1411 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
1413 while (!WorkList.empty()) {
1414 Instruction *I = WorkList.back(); // Get an instruction from the worklist
1415 WorkList.pop_back();
1417 // Check to see if we can DCE or ConstantPropagate the instruction...
1418 // Check to see if we can DIE the instruction...
1419 if (isInstructionTriviallyDead(I)) {
1420 // Add operands to the worklist...
1421 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
1422 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
1423 WorkList.push_back(Op);
1426 BasicBlock::iterator BBI = I;
1427 if (dceInstruction(BBI)) {
1428 removeFromWorkList(I);
1433 // Instruction isn't dead, see if we can constant propagate it...
1434 if (Constant *C = ConstantFoldInstruction(I)) {
1435 // Add operands to the worklist...
1436 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
1437 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
1438 WorkList.push_back(Op);
1439 ReplaceInstUsesWith(*I, C);
1442 BasicBlock::iterator BBI = I;
1443 if (dceInstruction(BBI)) {
1444 removeFromWorkList(I);
1449 // Now that we have an instruction, try combining it to simplify it...
1450 if (Instruction *Result = visit(*I)) {
1452 // Should we replace the old instruction with a new one?
1454 // Instructions can end up on the worklist more than once. Make sure
1455 // we do not process an instruction that has been deleted.
1456 removeFromWorkList(I);
1457 ReplaceInstWithInst(I, Result);
1459 BasicBlock::iterator II = I;
1461 // If the instruction was modified, it's possible that it is now dead.
1462 // if so, remove it.
1463 if (dceInstruction(II)) {
1464 // Instructions may end up in the worklist more than once. Erase them
1466 removeFromWorkList(I);
1472 WorkList.push_back(Result);
1473 AddUsesToWorkList(*Result);
1482 Pass *createInstructionCombiningPass() {
1483 return new InstCombiner();