1 //===- InstructionCombining.cpp - Combine multiple instructions -----------===//
3 // InstructionCombining - Combine instructions to form fewer, simple
4 // instructions. This pass does not modify the CFG This pass is where algebraic
5 // simplification happens.
7 // This pass combines things like:
13 // This is a simple worklist driven algorithm.
15 // This pass guarantees that the following cannonicalizations are performed on
17 // 1. If a binary operator has a constant operand, it is moved to the RHS
18 // 2. Logical operators with constant operands are always grouped so that
19 // 'or's are performed first, then 'and's, then 'xor's.
20 // 3. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible
21 // 4. All SetCC instructions on boolean values are replaced with logical ops
22 // N. This list is incomplete
24 //===----------------------------------------------------------------------===//
26 #include "llvm/Transforms/Scalar.h"
27 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
28 #include "llvm/Transforms/Utils/Local.h"
29 #include "llvm/Instructions.h"
30 #include "llvm/Pass.h"
31 #include "llvm/Constants.h"
32 #include "llvm/ConstantHandling.h"
33 #include "llvm/DerivedTypes.h"
34 #include "llvm/GlobalVariable.h"
35 #include "llvm/Support/InstIterator.h"
36 #include "llvm/Support/InstVisitor.h"
37 #include "llvm/Support/CallSite.h"
38 #include "Support/Statistic.h"
42 Statistic<> NumCombined ("instcombine", "Number of insts combined");
43 Statistic<> NumConstProp("instcombine", "Number of constant folds");
44 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
46 class InstCombiner : public FunctionPass,
47 public InstVisitor<InstCombiner, Instruction*> {
48 // Worklist of all of the instructions that need to be simplified.
49 std::vector<Instruction*> WorkList;
51 void AddUsesToWorkList(Instruction &I) {
52 // The instruction was simplified, add all users of the instruction to
53 // the work lists because they might get more simplified now...
55 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
57 WorkList.push_back(cast<Instruction>(*UI));
60 // removeFromWorkList - remove all instances of I from the worklist.
61 void removeFromWorkList(Instruction *I);
63 virtual bool runOnFunction(Function &F);
65 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
69 // Visitation implementation - Implement instruction combining for different
70 // instruction types. The semantics are as follows:
72 // null - No change was made
73 // I - Change was made, I is still valid, I may be dead though
74 // otherwise - Change was made, replace I with returned instruction
76 Instruction *visitAdd(BinaryOperator &I);
77 Instruction *visitSub(BinaryOperator &I);
78 Instruction *visitMul(BinaryOperator &I);
79 Instruction *visitDiv(BinaryOperator &I);
80 Instruction *visitRem(BinaryOperator &I);
81 Instruction *visitAnd(BinaryOperator &I);
82 Instruction *visitOr (BinaryOperator &I);
83 Instruction *visitXor(BinaryOperator &I);
84 Instruction *visitSetCondInst(BinaryOperator &I);
85 Instruction *visitShiftInst(ShiftInst &I);
86 Instruction *visitCastInst(CastInst &CI);
87 Instruction *visitCallInst(CallInst &CI);
88 Instruction *visitInvokeInst(InvokeInst &II);
89 Instruction *visitPHINode(PHINode &PN);
90 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
91 Instruction *visitAllocationInst(AllocationInst &AI);
92 Instruction *visitLoadInst(LoadInst &LI);
93 Instruction *visitBranchInst(BranchInst &BI);
95 // visitInstruction - Specify what to return for unhandled instructions...
96 Instruction *visitInstruction(Instruction &I) { return 0; }
99 bool transformConstExprCastCall(CallSite CS);
101 // InsertNewInstBefore - insert an instruction New before instruction Old
102 // in the program. Add the new instruction to the worklist.
104 void InsertNewInstBefore(Instruction *New, Instruction &Old) {
105 assert(New && New->getParent() == 0 &&
106 "New instruction already inserted into a basic block!");
107 BasicBlock *BB = Old.getParent();
108 BB->getInstList().insert(&Old, New); // Insert inst
109 WorkList.push_back(New); // Add to worklist
112 // ReplaceInstUsesWith - This method is to be used when an instruction is
113 // found to be dead, replacable with another preexisting expression. Here
114 // we add all uses of I to the worklist, replace all uses of I with the new
115 // value, then return I, so that the inst combiner will know that I was
118 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
119 AddUsesToWorkList(I); // Add all modified instrs to worklist
120 I.replaceAllUsesWith(V);
124 // SimplifyCommutative - This performs a few simplifications for commutative
126 bool SimplifyCommutative(BinaryOperator &I);
129 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
132 // getComplexity: Assign a complexity or rank value to LLVM Values...
133 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
134 static unsigned getComplexity(Value *V) {
135 if (isa<Instruction>(V)) {
136 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
140 if (isa<Argument>(V)) return 2;
141 return isa<Constant>(V) ? 0 : 1;
144 // isOnlyUse - Return true if this instruction will be deleted if we stop using
146 static bool isOnlyUse(Value *V) {
147 return V->use_size() == 1 || isa<Constant>(V);
150 // SimplifyCommutative - This performs a few simplifications for commutative
153 // 1. Order operands such that they are listed from right (least complex) to
154 // left (most complex). This puts constants before unary operators before
157 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
158 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
160 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
161 bool Changed = false;
162 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
163 Changed = !I.swapOperands();
165 if (!I.isAssociative()) return Changed;
166 Instruction::BinaryOps Opcode = I.getOpcode();
167 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
168 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
169 if (isa<Constant>(I.getOperand(1))) {
170 Constant *Folded = ConstantExpr::get(I.getOpcode(),
171 cast<Constant>(I.getOperand(1)),
172 cast<Constant>(Op->getOperand(1)));
173 I.setOperand(0, Op->getOperand(0));
174 I.setOperand(1, Folded);
176 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
177 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
178 isOnlyUse(Op) && isOnlyUse(Op1)) {
179 Constant *C1 = cast<Constant>(Op->getOperand(1));
180 Constant *C2 = cast<Constant>(Op1->getOperand(1));
182 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
183 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
184 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
187 WorkList.push_back(New);
188 I.setOperand(0, New);
189 I.setOperand(1, Folded);
196 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
197 // if the LHS is a constant zero (which is the 'negate' form).
199 static inline Value *dyn_castNegVal(Value *V) {
200 if (BinaryOperator::isNeg(V))
201 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
203 // Constants can be considered to be negated values if they can be folded...
204 if (Constant *C = dyn_cast<Constant>(V))
205 return ConstantExpr::get(Instruction::Sub,
206 Constant::getNullValue(V->getType()), C);
210 static inline Value *dyn_castNotVal(Value *V) {
211 if (BinaryOperator::isNot(V))
212 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
214 // Constants can be considered to be not'ed values...
215 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
216 return ConstantExpr::get(Instruction::Xor,
217 ConstantIntegral::getAllOnesValue(C->getType()),C);
221 // dyn_castFoldableMul - If this value is a multiply that can be folded into
222 // other computations (because it has a constant operand), return the
223 // non-constant operand of the multiply.
225 static inline Value *dyn_castFoldableMul(Value *V) {
226 if (V->use_size() == 1 && V->getType()->isInteger())
227 if (Instruction *I = dyn_cast<Instruction>(V))
228 if (I->getOpcode() == Instruction::Mul)
229 if (isa<Constant>(I->getOperand(1)))
230 return I->getOperand(0);
234 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
235 // a constant, return the constant being anded with.
237 static inline Constant *dyn_castMaskingAnd(Value *V) {
238 if (Instruction *I = dyn_cast<Instruction>(V))
239 if (I->getOpcode() == Instruction::And)
240 return dyn_cast<Constant>(I->getOperand(1));
242 // If this is a constant, it acts just like we were masking with it.
243 return dyn_cast<Constant>(V);
246 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
248 static unsigned Log2(uint64_t Val) {
249 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
252 if (Val & 1) return 0; // Multiple bits set?
259 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
260 bool Changed = SimplifyCommutative(I);
261 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
263 // Eliminate 'add int %X, 0'
264 if (RHS == Constant::getNullValue(I.getType()))
265 return ReplaceInstUsesWith(I, LHS);
268 if (Value *V = dyn_castNegVal(LHS))
269 return BinaryOperator::create(Instruction::Sub, RHS, V);
272 if (!isa<Constant>(RHS))
273 if (Value *V = dyn_castNegVal(RHS))
274 return BinaryOperator::create(Instruction::Sub, LHS, V);
276 // X*C + X --> X * (C+1)
277 if (dyn_castFoldableMul(LHS) == RHS) {
279 ConstantExpr::get(Instruction::Add,
280 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
281 ConstantInt::get(I.getType(), 1));
282 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
285 // X + X*C --> X * (C+1)
286 if (dyn_castFoldableMul(RHS) == LHS) {
288 ConstantExpr::get(Instruction::Add,
289 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
290 ConstantInt::get(I.getType(), 1));
291 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
294 // (A & C1)+(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
295 if (Constant *C1 = dyn_castMaskingAnd(LHS))
296 if (Constant *C2 = dyn_castMaskingAnd(RHS))
297 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
298 return BinaryOperator::create(Instruction::Or, LHS, RHS);
300 return Changed ? &I : 0;
303 // isSignBit - Return true if the value represented by the constant only has the
304 // highest order bit set.
305 static bool isSignBit(ConstantInt *CI) {
306 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
307 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
310 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
311 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
313 if (Op0 == Op1) // sub X, X -> 0
314 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
316 // If this is a 'B = x-(-A)', change to B = x+A...
317 if (Value *V = dyn_castNegVal(Op1))
318 return BinaryOperator::create(Instruction::Add, Op0, V);
320 // Replace (-1 - A) with (~A)...
321 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0))
322 if (C->isAllOnesValue())
323 return BinaryOperator::createNot(Op1);
325 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
326 if (Op1I->use_size() == 1) {
327 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
328 // is not used by anyone else...
330 if (Op1I->getOpcode() == Instruction::Sub) {
331 // Swap the two operands of the subexpr...
332 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
333 Op1I->setOperand(0, IIOp1);
334 Op1I->setOperand(1, IIOp0);
336 // Create the new top level add instruction...
337 return BinaryOperator::create(Instruction::Add, Op0, Op1);
340 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
342 if (Op1I->getOpcode() == Instruction::And &&
343 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
344 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
346 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
347 return BinaryOperator::create(Instruction::And, Op0, NewNot);
350 // X - X*C --> X * (1-C)
351 if (dyn_castFoldableMul(Op1I) == Op0) {
353 ConstantExpr::get(Instruction::Sub,
354 ConstantInt::get(I.getType(), 1),
355 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
356 assert(CP1 && "Couldn't constant fold 1-C?");
357 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
361 // X*C - X --> X * (C-1)
362 if (dyn_castFoldableMul(Op0) == Op1) {
364 ConstantExpr::get(Instruction::Sub,
365 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
366 ConstantInt::get(I.getType(), 1));
367 assert(CP1 && "Couldn't constant fold C - 1?");
368 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
374 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
375 bool Changed = SimplifyCommutative(I);
376 Value *Op0 = I.getOperand(0);
378 // Simplify mul instructions with a constant RHS...
379 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
380 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
381 const Type *Ty = CI->getType();
382 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
384 case -1: // X * -1 -> -X
385 return BinaryOperator::createNeg(Op0, I.getName());
387 return ReplaceInstUsesWith(I, Op1); // Eliminate 'mul double %X, 0'
389 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul int %X, 1'
390 case 2: // Convert 'mul int %X, 2' to 'add int %X, %X'
391 return BinaryOperator::create(Instruction::Add, Op0, Op0, I.getName());
394 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
395 return new ShiftInst(Instruction::Shl, Op0,
396 ConstantUInt::get(Type::UByteTy, C));
398 ConstantFP *Op1F = cast<ConstantFP>(Op1);
399 if (Op1F->isNullValue())
400 return ReplaceInstUsesWith(I, Op1);
402 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
403 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
404 if (Op1F->getValue() == 1.0)
405 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
409 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
410 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
411 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
413 return Changed ? &I : 0;
416 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
418 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
419 if (RHS->equalsInt(1))
420 return ReplaceInstUsesWith(I, I.getOperand(0));
422 // Check to see if this is an unsigned division with an exact power of 2,
423 // if so, convert to a right shift.
424 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
425 if (uint64_t Val = C->getValue()) // Don't break X / 0
426 if (uint64_t C = Log2(Val))
427 return new ShiftInst(Instruction::Shr, I.getOperand(0),
428 ConstantUInt::get(Type::UByteTy, C));
431 // 0 / X == 0, we don't need to preserve faults!
432 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
433 if (LHS->equalsInt(0))
434 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
440 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
441 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
442 if (RHS->equalsInt(1)) // X % 1 == 0
443 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
445 // Check to see if this is an unsigned remainder with an exact power of 2,
446 // if so, convert to a bitwise and.
447 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
448 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
450 return BinaryOperator::create(Instruction::And, I.getOperand(0),
451 ConstantUInt::get(I.getType(), Val-1));
454 // 0 % X == 0, we don't need to preserve faults!
455 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
456 if (LHS->equalsInt(0))
457 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
462 // isMaxValueMinusOne - return true if this is Max-1
463 static bool isMaxValueMinusOne(const ConstantInt *C) {
464 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
465 // Calculate -1 casted to the right type...
466 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
467 uint64_t Val = ~0ULL; // All ones
468 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
469 return CU->getValue() == Val-1;
472 const ConstantSInt *CS = cast<ConstantSInt>(C);
474 // Calculate 0111111111..11111
475 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
476 int64_t Val = INT64_MAX; // All ones
477 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
478 return CS->getValue() == Val-1;
481 // isMinValuePlusOne - return true if this is Min+1
482 static bool isMinValuePlusOne(const ConstantInt *C) {
483 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
484 return CU->getValue() == 1;
486 const ConstantSInt *CS = cast<ConstantSInt>(C);
488 // Calculate 1111111111000000000000
489 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
490 int64_t Val = -1; // All ones
491 Val <<= TypeBits-1; // Shift over to the right spot
492 return CS->getValue() == Val+1;
496 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
497 bool Changed = SimplifyCommutative(I);
498 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
500 // and X, X = X and X, 0 == 0
501 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
502 return ReplaceInstUsesWith(I, Op1);
505 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
506 if (RHS->isAllOnesValue())
507 return ReplaceInstUsesWith(I, Op0);
509 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
510 Value *X = Op0I->getOperand(0);
511 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
512 if (Op0I->getOpcode() == Instruction::Xor) {
513 if ((*RHS & *Op0CI)->isNullValue()) {
514 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
515 return BinaryOperator::create(Instruction::And, X, RHS);
516 } else if (isOnlyUse(Op0)) {
517 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
518 std::string Op0Name = Op0I->getName(); Op0I->setName("");
519 Instruction *And = BinaryOperator::create(Instruction::And,
521 InsertNewInstBefore(And, I);
522 return BinaryOperator::create(Instruction::Xor, And, *RHS & *Op0CI);
524 } else if (Op0I->getOpcode() == Instruction::Or) {
525 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
526 if ((*RHS & *Op0CI)->isNullValue())
527 return BinaryOperator::create(Instruction::And, X, RHS);
529 Constant *Together = *RHS & *Op0CI;
530 if (Together == RHS) // (X | C) & C --> C
531 return ReplaceInstUsesWith(I, RHS);
533 if (isOnlyUse(Op0)) {
534 if (Together != Op0CI) {
535 // (X | C1) & C2 --> (X | (C1&C2)) & C2
536 std::string Op0Name = Op0I->getName(); Op0I->setName("");
537 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
539 InsertNewInstBefore(Or, I);
540 return BinaryOperator::create(Instruction::And, Or, RHS);
547 Value *Op0NotVal = dyn_castNotVal(Op0);
548 Value *Op1NotVal = dyn_castNotVal(Op1);
550 // (~A & ~B) == (~(A | B)) - Demorgan's Law
551 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
552 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
553 Op1NotVal,I.getName()+".demorgan");
554 InsertNewInstBefore(Or, I);
555 return BinaryOperator::createNot(Or);
558 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
559 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
561 return Changed ? &I : 0;
566 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
567 bool Changed = SimplifyCommutative(I);
568 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
570 // or X, X = X or X, 0 == X
571 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
572 return ReplaceInstUsesWith(I, Op0);
575 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
576 if (RHS->isAllOnesValue())
577 return ReplaceInstUsesWith(I, Op1);
579 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
580 // (X & C1) | C2 --> (X | C2) & (C1|C2)
581 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
582 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
583 std::string Op0Name = Op0I->getName(); Op0I->setName("");
584 Instruction *Or = BinaryOperator::create(Instruction::Or,
585 Op0I->getOperand(0), RHS,
587 InsertNewInstBefore(Or, I);
588 return BinaryOperator::create(Instruction::And, Or, *RHS | *Op0CI);
591 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
592 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
593 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
594 std::string Op0Name = Op0I->getName(); Op0I->setName("");
595 Instruction *Or = BinaryOperator::create(Instruction::Or,
596 Op0I->getOperand(0), RHS,
598 InsertNewInstBefore(Or, I);
599 return BinaryOperator::create(Instruction::Xor, Or, *Op0CI & *~*RHS);
604 Value *Op0NotVal = dyn_castNotVal(Op0);
605 Value *Op1NotVal = dyn_castNotVal(Op1);
607 if (Op1 == Op0NotVal) // ~A | A == -1
608 return ReplaceInstUsesWith(I,
609 ConstantIntegral::getAllOnesValue(I.getType()));
611 if (Op0 == Op1NotVal) // A | ~A == -1
612 return ReplaceInstUsesWith(I,
613 ConstantIntegral::getAllOnesValue(I.getType()));
615 // (~A | ~B) == (~(A & B)) - Demorgan's Law
616 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
617 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
618 Op1NotVal,I.getName()+".demorgan",
620 WorkList.push_back(And);
621 return BinaryOperator::createNot(And);
624 return Changed ? &I : 0;
629 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
630 bool Changed = SimplifyCommutative(I);
631 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
635 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
637 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
639 if (RHS->isNullValue())
640 return ReplaceInstUsesWith(I, Op0);
642 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
643 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
644 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
645 if (RHS == ConstantBool::True && SCI->use_size() == 1)
646 return new SetCondInst(SCI->getInverseCondition(),
647 SCI->getOperand(0), SCI->getOperand(1));
649 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
650 if (Op0I->getOpcode() == Instruction::And) {
651 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
652 if ((*RHS & *Op0CI)->isNullValue())
653 return BinaryOperator::create(Instruction::Or, Op0, RHS);
654 } else if (Op0I->getOpcode() == Instruction::Or) {
655 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
656 if ((*RHS & *Op0CI) == RHS)
657 return BinaryOperator::create(Instruction::And, Op0, ~*RHS);
662 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
664 return ReplaceInstUsesWith(I,
665 ConstantIntegral::getAllOnesValue(I.getType()));
667 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
669 return ReplaceInstUsesWith(I,
670 ConstantIntegral::getAllOnesValue(I.getType()));
672 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
673 if (Op1I->getOpcode() == Instruction::Or)
674 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
675 cast<BinaryOperator>(Op1I)->swapOperands();
678 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
683 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
684 if (Op0I->getOpcode() == Instruction::Or && Op0I->use_size() == 1) {
685 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
686 cast<BinaryOperator>(Op0I)->swapOperands();
687 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
688 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
689 WorkList.push_back(cast<Instruction>(NotB));
690 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
695 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
696 if (Constant *C1 = dyn_castMaskingAnd(Op0))
697 if (Constant *C2 = dyn_castMaskingAnd(Op1))
698 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
699 return BinaryOperator::create(Instruction::Or, Op0, Op1);
701 return Changed ? &I : 0;
704 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
705 static Constant *AddOne(ConstantInt *C) {
706 Constant *Result = ConstantExpr::get(Instruction::Add, C,
707 ConstantInt::get(C->getType(), 1));
708 assert(Result && "Constant folding integer addition failed!");
711 static Constant *SubOne(ConstantInt *C) {
712 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
713 ConstantInt::get(C->getType(), 1));
714 assert(Result && "Constant folding integer addition failed!");
718 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
719 // true when both operands are equal...
721 static bool isTrueWhenEqual(Instruction &I) {
722 return I.getOpcode() == Instruction::SetEQ ||
723 I.getOpcode() == Instruction::SetGE ||
724 I.getOpcode() == Instruction::SetLE;
727 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
728 bool Changed = SimplifyCommutative(I);
729 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
730 const Type *Ty = Op0->getType();
734 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
736 // setcc <global*>, 0 - Global value addresses are never null!
737 if (isa<GlobalValue>(Op0) && isa<ConstantPointerNull>(Op1))
738 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
740 // setcc's with boolean values can always be turned into bitwise operations
741 if (Ty == Type::BoolTy) {
742 // If this is <, >, or !=, we can change this into a simple xor instruction
743 if (!isTrueWhenEqual(I))
744 return BinaryOperator::create(Instruction::Xor, Op0, Op1, I.getName());
746 // Otherwise we need to make a temporary intermediate instruction and insert
747 // it into the instruction stream. This is what we are after:
749 // seteq bool %A, %B -> ~(A^B)
750 // setle bool %A, %B -> ~A | B
751 // setge bool %A, %B -> A | ~B
753 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
754 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
756 InsertNewInstBefore(Xor, I);
757 return BinaryOperator::createNot(Xor, I.getName());
760 // Handle the setXe cases...
761 assert(I.getOpcode() == Instruction::SetGE ||
762 I.getOpcode() == Instruction::SetLE);
764 if (I.getOpcode() == Instruction::SetGE)
765 std::swap(Op0, Op1); // Change setge -> setle
767 // Now we just have the SetLE case.
768 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
769 InsertNewInstBefore(Not, I);
770 return BinaryOperator::create(Instruction::Or, Not, Op1, I.getName());
773 // Check to see if we are doing one of many comparisons against constant
774 // integers at the end of their ranges...
776 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
777 // Simplify seteq and setne instructions...
778 if (I.getOpcode() == Instruction::SetEQ ||
779 I.getOpcode() == Instruction::SetNE) {
780 bool isSetNE = I.getOpcode() == Instruction::SetNE;
782 if (CI->isNullValue()) { // Simplify [seteq|setne] X, 0
783 CastInst *Val = new CastInst(Op0, Type::BoolTy, I.getName()+".not");
784 if (isSetNE) return Val;
786 // seteq X, 0 -> not (cast X to bool)
787 InsertNewInstBefore(Val, I);
788 return BinaryOperator::createNot(Val, I.getName());
791 // If the first operand is (and|or|xor) with a constant, and the second
792 // operand is a constant, simplify a bit.
793 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
794 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1)))
795 if (BO->getOpcode() == Instruction::Or) {
796 // If bits are being or'd in that are not present in the constant we
797 // are comparing against, then the comparison could never succeed!
798 if (!(*BOC & *~*CI)->isNullValue())
799 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
800 } else if (BO->getOpcode() == Instruction::And) {
801 // If bits are being compared against that are and'd out, then the
802 // comparison can never succeed!
803 if (!(*CI & *~*BOC)->isNullValue())
804 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
805 } else if (BO->getOpcode() == Instruction::Xor) {
806 // For the xor case, we can always just xor the two constants
807 // together, potentially eliminating the explicit xor.
808 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
813 // Check to see if we are comparing against the minimum or maximum value...
814 if (CI->isMinValue()) {
815 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
816 return ReplaceInstUsesWith(I, ConstantBool::False);
817 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
818 return ReplaceInstUsesWith(I, ConstantBool::True);
819 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
820 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
821 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
822 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
824 } else if (CI->isMaxValue()) {
825 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
826 return ReplaceInstUsesWith(I, ConstantBool::False);
827 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
828 return ReplaceInstUsesWith(I, ConstantBool::True);
829 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
830 return BinaryOperator::create(Instruction::SetEQ, Op0,Op1, I.getName());
831 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
832 return BinaryOperator::create(Instruction::SetNE, Op0,Op1, I.getName());
834 // Comparing against a value really close to min or max?
835 } else if (isMinValuePlusOne(CI)) {
836 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
837 return BinaryOperator::create(Instruction::SetEQ, Op0,
838 SubOne(CI), I.getName());
839 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
840 return BinaryOperator::create(Instruction::SetNE, Op0,
841 SubOne(CI), I.getName());
843 } else if (isMaxValueMinusOne(CI)) {
844 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
845 return BinaryOperator::create(Instruction::SetEQ, Op0,
846 AddOne(CI), I.getName());
847 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
848 return BinaryOperator::create(Instruction::SetNE, Op0,
849 AddOne(CI), I.getName());
853 return Changed ? &I : 0;
858 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
859 assert(I.getOperand(1)->getType() == Type::UByteTy);
860 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
862 // shl X, 0 == X and shr X, 0 == X
863 // shl 0, X == 0 and shr 0, X == 0
864 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
865 Op0 == Constant::getNullValue(Op0->getType()))
866 return ReplaceInstUsesWith(I, Op0);
868 // If this is a shift of a shift, see if we can fold the two together...
869 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0)) {
870 if (isa<Constant>(Op1) && isa<Constant>(Op0SI->getOperand(1))) {
871 ConstantUInt *ShiftAmt1C = cast<ConstantUInt>(Op0SI->getOperand(1));
872 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
873 unsigned ShiftAmt2 = cast<ConstantUInt>(Op1)->getValue();
875 // Check for (A << c1) << c2 and (A >> c1) >> c2
876 if (I.getOpcode() == Op0SI->getOpcode()) {
877 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
878 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
879 ConstantUInt::get(Type::UByteTy, Amt));
882 if (I.getType()->isUnsigned()) { // Check for (A << c1) >> c2 or visaversa
883 // Calculate bitmask for what gets shifted off the edge...
884 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
885 if (I.getOpcode() == Instruction::Shr)
886 C = ConstantExpr::getShift(Instruction::Shr, C, ShiftAmt1C);
888 C = ConstantExpr::getShift(Instruction::Shl, C, ShiftAmt1C);
891 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
892 C, Op0SI->getOperand(0)->getName()+".mask",&I);
893 WorkList.push_back(Mask);
895 // Figure out what flavor of shift we should use...
896 if (ShiftAmt1 == ShiftAmt2)
897 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
898 else if (ShiftAmt1 < ShiftAmt2) {
899 return new ShiftInst(I.getOpcode(), Mask,
900 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
902 return new ShiftInst(Op0SI->getOpcode(), Mask,
903 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
909 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr of
912 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
913 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
914 if (CUI->getValue() >= TypeBits &&
915 (!Op0->getType()->isSigned() || I.getOpcode() == Instruction::Shl))
916 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
918 // Check to see if we are shifting left by 1. If so, turn it into an add
920 if (I.getOpcode() == Instruction::Shl && CUI->equalsInt(1))
921 // Convert 'shl int %X, 1' to 'add int %X, %X'
922 return BinaryOperator::create(Instruction::Add, Op0, Op0, I.getName());
926 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
927 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
928 if (I.getOpcode() == Instruction::Shr && CSI->isAllOnesValue())
929 return ReplaceInstUsesWith(I, CSI);
935 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
938 static inline bool isEliminableCastOfCast(const CastInst &CI,
939 const CastInst *CSrc) {
940 assert(CI.getOperand(0) == CSrc);
941 const Type *SrcTy = CSrc->getOperand(0)->getType();
942 const Type *MidTy = CSrc->getType();
943 const Type *DstTy = CI.getType();
945 // It is legal to eliminate the instruction if casting A->B->A if the sizes
946 // are identical and the bits don't get reinterpreted (for example
947 // int->float->int would not be allowed)
948 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
951 // Allow free casting and conversion of sizes as long as the sign doesn't
953 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
954 unsigned SrcSize = SrcTy->getPrimitiveSize();
955 unsigned MidSize = MidTy->getPrimitiveSize();
956 unsigned DstSize = DstTy->getPrimitiveSize();
958 // Cases where we are monotonically decreasing the size of the type are
959 // always ok, regardless of what sign changes are going on.
961 if (SrcSize >= MidSize && MidSize >= DstSize)
964 // Cases where the source and destination type are the same, but the middle
965 // type is bigger are noops.
967 if (SrcSize == DstSize && MidSize > SrcSize)
970 // If we are monotonically growing, things are more complex.
972 if (SrcSize <= MidSize && MidSize <= DstSize) {
973 // We have eight combinations of signedness to worry about. Here's the
975 static const int SignTable[8] = {
976 // CODE, SrcSigned, MidSigned, DstSigned, Comment
977 1, // U U U Always ok
978 1, // U U S Always ok
979 3, // U S U Ok iff SrcSize != MidSize
980 3, // U S S Ok iff SrcSize != MidSize
982 2, // S U S Ok iff MidSize == DstSize
983 1, // S S U Always ok
984 1, // S S S Always ok
987 // Choose an action based on the current entry of the signtable that this
988 // cast of cast refers to...
989 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
990 switch (SignTable[Row]) {
991 case 0: return false; // Never ok
992 case 1: return true; // Always ok
993 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
994 case 3: // Ok iff SrcSize != MidSize
995 return SrcSize != MidSize || SrcTy == Type::BoolTy;
996 default: assert(0 && "Bad entry in sign table!");
1001 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1002 // like: short -> ushort -> uint, because this can create wrong results if
1003 // the input short is negative!
1009 // CastInst simplification
1011 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1012 Value *Src = CI.getOperand(0);
1014 // If the user is casting a value to the same type, eliminate this cast
1016 if (CI.getType() == Src->getType())
1017 return ReplaceInstUsesWith(CI, Src);
1019 // If casting the result of another cast instruction, try to eliminate this
1022 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1023 if (isEliminableCastOfCast(CI, CSrc)) {
1024 // This instruction now refers directly to the cast's src operand. This
1025 // has a good chance of making CSrc dead.
1026 CI.setOperand(0, CSrc->getOperand(0));
1030 // If this is an A->B->A cast, and we are dealing with integral types, try
1031 // to convert this into a logical 'and' instruction.
1033 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1034 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1035 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1036 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1037 assert(CSrc->getType() != Type::ULongTy &&
1038 "Cannot have type bigger than ulong!");
1039 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1040 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1041 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1046 // If casting the result of a getelementptr instruction with no offset, turn
1047 // this into a cast of the original pointer!
1049 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1050 bool AllZeroOperands = true;
1051 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1052 if (!isa<Constant>(GEP->getOperand(i)) ||
1053 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
1054 AllZeroOperands = false;
1057 if (AllZeroOperands) {
1058 CI.setOperand(0, GEP->getOperand(0));
1063 // If this is a cast to bool (which is effectively a "!=0" test), then we can
1064 // perform a few optimizations...
1066 if (CI.getType() == Type::BoolTy) {
1067 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Src)) {
1068 Value *Op0 = BO->getOperand(0), *Op1 = BO->getOperand(1);
1070 switch (BO->getOpcode()) {
1071 case Instruction::Sub:
1072 case Instruction::Xor:
1073 // Replace (cast ([sub|xor] A, B) to bool) with (setne A, B)
1074 return new SetCondInst(Instruction::SetNE, Op0, Op1);
1076 // Replace (cast (add A, B) to bool) with (setne A, -B) if B is
1077 // efficiently invertible, or if the add has just this one use.
1078 case Instruction::Add:
1079 if (Value *NegVal = dyn_castNegVal(Op1))
1080 return new SetCondInst(Instruction::SetNE, Op0, NegVal);
1081 else if (Value *NegVal = dyn_castNegVal(Op0))
1082 return new SetCondInst(Instruction::SetNE, NegVal, Op1);
1083 else if (BO->use_size() == 1) {
1084 Instruction *Neg = BinaryOperator::createNeg(Op1, BO->getName());
1086 InsertNewInstBefore(Neg, CI);
1087 return new SetCondInst(Instruction::SetNE, Op0, Neg);
1091 case Instruction::And:
1092 // Replace (cast (and X, (1 << size(X)-1)) to bool) with x < 0,
1093 // converting X to be a signed value as appropriate. Don't worry about
1094 // bool values, as they will be optimized other ways if they occur in
1095 // this configuration.
1096 if (ConstantInt *CInt = dyn_cast<ConstantInt>(Op1))
1097 if (isSignBit(CInt)) {
1098 // If 'X' is not signed, insert a cast now...
1099 if (!CInt->getType()->isSigned()) {
1101 switch (CInt->getType()->getPrimitiveID()) {
1102 case Type::UByteTyID: DestTy = Type::SByteTy; break;
1103 case Type::UShortTyID: DestTy = Type::ShortTy; break;
1104 case Type::UIntTyID: DestTy = Type::IntTy; break;
1105 case Type::ULongTyID: DestTy = Type::LongTy; break;
1106 default: assert(0 && "Invalid unsigned integer type!"); abort();
1108 CastInst *NewCI = new CastInst(Op0, DestTy,
1109 Op0->getName()+".signed");
1110 InsertNewInstBefore(NewCI, CI);
1113 return new SetCondInst(Instruction::SetLT, Op0,
1114 Constant::getNullValue(Op0->getType()));
1125 // CallInst simplification
1127 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
1128 if (transformConstExprCastCall(&CI)) return 0;
1132 // InvokeInst simplification
1134 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
1135 if (transformConstExprCastCall(&II)) return 0;
1139 // getPromotedType - Return the specified type promoted as it would be to pass
1140 // though a va_arg area...
1141 static const Type *getPromotedType(const Type *Ty) {
1142 switch (Ty->getPrimitiveID()) {
1143 case Type::SByteTyID:
1144 case Type::ShortTyID: return Type::IntTy;
1145 case Type::UByteTyID:
1146 case Type::UShortTyID: return Type::UIntTy;
1147 case Type::FloatTyID: return Type::DoubleTy;
1152 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
1153 // attempt to move the cast to the arguments of the call/invoke.
1155 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
1156 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
1157 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
1158 if (CE->getOpcode() != Instruction::Cast ||
1159 !isa<ConstantPointerRef>(CE->getOperand(0)))
1161 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
1162 if (!isa<Function>(CPR->getValue())) return false;
1163 Function *Callee = cast<Function>(CPR->getValue());
1164 Instruction *Caller = CS.getInstruction();
1166 // Okay, this is a cast from a function to a different type. Unless doing so
1167 // would cause a type conversion of one of our arguments, change this call to
1168 // be a direct call with arguments casted to the appropriate types.
1170 const FunctionType *FT = Callee->getFunctionType();
1171 const Type *OldRetTy = Caller->getType();
1173 if (Callee->isExternal() &&
1174 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()))
1175 return false; // Cannot transform this return value...
1177 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
1178 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
1180 CallSite::arg_iterator AI = CS.arg_begin();
1181 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
1182 const Type *ParamTy = FT->getParamType(i);
1183 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
1184 if (Callee->isExternal() && !isConvertible) return false;
1187 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1188 Callee->isExternal())
1189 return false; // Do not delete arguments unless we have a function body...
1191 // Okay, we decided that this is a safe thing to do: go ahead and start
1192 // inserting cast instructions as necessary...
1193 std::vector<Value*> Args;
1194 Args.reserve(NumActualArgs);
1196 AI = CS.arg_begin();
1197 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1198 const Type *ParamTy = FT->getParamType(i);
1199 if ((*AI)->getType() == ParamTy) {
1200 Args.push_back(*AI);
1202 Instruction *Cast = new CastInst(*AI, ParamTy, "tmp");
1203 InsertNewInstBefore(Cast, *Caller);
1204 Args.push_back(Cast);
1208 // If the function takes more arguments than the call was taking, add them
1210 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1211 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1213 // If we are removing arguments to the function, emit an obnoxious warning...
1214 if (FT->getNumParams() < NumActualArgs)
1215 if (!FT->isVarArg()) {
1216 std::cerr << "WARNING: While resolving call to function '"
1217 << Callee->getName() << "' arguments were dropped!\n";
1219 // Add all of the arguments in their promoted form to the arg list...
1220 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1221 const Type *PTy = getPromotedType((*AI)->getType());
1222 if (PTy != (*AI)->getType()) {
1223 // Must promote to pass through va_arg area!
1224 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
1225 InsertNewInstBefore(Cast, *Caller);
1226 Args.push_back(Cast);
1228 Args.push_back(*AI);
1233 if (FT->getReturnType() == Type::VoidTy)
1234 Caller->setName(""); // Void type should not have a name...
1237 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1238 NC = new InvokeInst(Callee, II->getNormalDest(), II->getExceptionalDest(),
1239 Args, Caller->getName(), Caller);
1241 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
1244 // Insert a cast of the return type as necessary...
1246 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
1247 if (NV->getType() != Type::VoidTy) {
1248 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
1249 InsertNewInstBefore(NC, *Caller);
1250 AddUsesToWorkList(*Caller);
1252 NV = Constant::getNullValue(Caller->getType());
1256 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
1257 Caller->replaceAllUsesWith(NV);
1258 Caller->getParent()->getInstList().erase(Caller);
1259 removeFromWorkList(Caller);
1265 // PHINode simplification
1267 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
1268 // If the PHI node only has one incoming value, eliminate the PHI node...
1269 if (PN.getNumIncomingValues() == 1)
1270 return ReplaceInstUsesWith(PN, PN.getIncomingValue(0));
1272 // Otherwise if all of the incoming values are the same for the PHI, replace
1273 // the PHI node with the incoming value.
1276 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
1277 if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself...
1278 if (InVal && PN.getIncomingValue(i) != InVal)
1279 return 0; // Not the same, bail out.
1281 InVal = PN.getIncomingValue(i);
1283 // The only case that could cause InVal to be null is if we have a PHI node
1284 // that only has entries for itself. In this case, there is no entry into the
1285 // loop, so kill the PHI.
1287 if (InVal == 0) InVal = Constant::getNullValue(PN.getType());
1289 // All of the incoming values are the same, replace the PHI node now.
1290 return ReplaceInstUsesWith(PN, InVal);
1294 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1295 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
1296 // If so, eliminate the noop.
1297 if ((GEP.getNumOperands() == 2 &&
1298 GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
1299 GEP.getNumOperands() == 1)
1300 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
1302 // Combine Indices - If the source pointer to this getelementptr instruction
1303 // is a getelementptr instruction, combine the indices of the two
1304 // getelementptr instructions into a single instruction.
1306 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
1307 std::vector<Value *> Indices;
1309 // Can we combine the two pointer arithmetics offsets?
1310 if (Src->getNumOperands() == 2 && isa<Constant>(Src->getOperand(1)) &&
1311 isa<Constant>(GEP.getOperand(1))) {
1312 // Replace: gep (gep %P, long C1), long C2, ...
1313 // With: gep %P, long (C1+C2), ...
1314 Value *Sum = ConstantExpr::get(Instruction::Add,
1315 cast<Constant>(Src->getOperand(1)),
1316 cast<Constant>(GEP.getOperand(1)));
1317 assert(Sum && "Constant folding of longs failed!?");
1318 GEP.setOperand(0, Src->getOperand(0));
1319 GEP.setOperand(1, Sum);
1320 AddUsesToWorkList(*Src); // Reduce use count of Src
1322 } else if (Src->getNumOperands() == 2) {
1323 // Replace: gep (gep %P, long B), long A, ...
1324 // With: T = long A+B; gep %P, T, ...
1326 Value *Sum = BinaryOperator::create(Instruction::Add, Src->getOperand(1),
1328 Src->getName()+".sum", &GEP);
1329 GEP.setOperand(0, Src->getOperand(0));
1330 GEP.setOperand(1, Sum);
1331 WorkList.push_back(cast<Instruction>(Sum));
1333 } else if (*GEP.idx_begin() == Constant::getNullValue(Type::LongTy) &&
1334 Src->getNumOperands() != 1) {
1335 // Otherwise we can do the fold if the first index of the GEP is a zero
1336 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end());
1337 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
1338 } else if (Src->getOperand(Src->getNumOperands()-1) ==
1339 Constant::getNullValue(Type::LongTy)) {
1340 // If the src gep ends with a constant array index, merge this get into
1341 // it, even if we have a non-zero array index.
1342 Indices.insert(Indices.end(), Src->idx_begin(), Src->idx_end()-1);
1343 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
1346 if (!Indices.empty())
1347 return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
1349 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
1350 // GEP of global variable. If all of the indices for this GEP are
1351 // constants, we can promote this to a constexpr instead of an instruction.
1353 // Scan for nonconstants...
1354 std::vector<Constant*> Indices;
1355 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
1356 for (; I != E && isa<Constant>(*I); ++I)
1357 Indices.push_back(cast<Constant>(*I));
1359 if (I == E) { // If they are all constants...
1361 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
1363 // Replace all uses of the GEP with the new constexpr...
1364 return ReplaceInstUsesWith(GEP, CE);
1371 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
1372 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
1373 if (AI.isArrayAllocation()) // Check C != 1
1374 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
1375 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
1376 AllocationInst *New = 0;
1378 // Create and insert the replacement instruction...
1379 if (isa<MallocInst>(AI))
1380 New = new MallocInst(NewTy, 0, AI.getName(), &AI);
1382 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
1383 New = new AllocaInst(NewTy, 0, AI.getName(), &AI);
1386 // Scan to the end of the allocation instructions, to skip over a block of
1387 // allocas if possible...
1389 BasicBlock::iterator It = New;
1390 while (isa<AllocationInst>(*It)) ++It;
1392 // Now that I is pointing to the first non-allocation-inst in the block,
1393 // insert our getelementptr instruction...
1395 std::vector<Value*> Idx(2, Constant::getNullValue(Type::LongTy));
1396 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
1398 // Now make everything use the getelementptr instead of the original
1400 ReplaceInstUsesWith(AI, V);
1406 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
1407 /// constantexpr, return the constant value being addressed by the constant
1408 /// expression, or null if something is funny.
1410 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
1411 if (CE->getOperand(1) != Constant::getNullValue(Type::LongTy))
1412 return 0; // Do not allow stepping over the value!
1414 // Loop over all of the operands, tracking down which value we are
1416 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
1417 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
1418 ConstantStruct *CS = cast<ConstantStruct>(C);
1419 if (CU->getValue() >= CS->getValues().size()) return 0;
1420 C = cast<Constant>(CS->getValues()[CU->getValue()]);
1421 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
1422 ConstantArray *CA = cast<ConstantArray>(C);
1423 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
1424 C = cast<Constant>(CA->getValues()[CS->getValue()]);
1430 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
1431 Value *Op = LI.getOperand(0);
1432 if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Op))
1433 Op = CPR->getValue();
1435 // Instcombine load (constant global) into the value loaded...
1436 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
1437 if (GV->isConstant() && !GV->isExternal())
1438 return ReplaceInstUsesWith(LI, GV->getInitializer());
1440 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
1441 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
1442 if (CE->getOpcode() == Instruction::GetElementPtr)
1443 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
1444 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
1445 if (GV->isConstant() && !GV->isExternal())
1446 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
1447 return ReplaceInstUsesWith(LI, V);
1452 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
1453 // Change br (not X), label True, label False to: br X, label False, True
1454 if (BI.isConditional() && !isa<Constant>(BI.getCondition()))
1455 if (Value *V = dyn_castNotVal(BI.getCondition())) {
1456 BasicBlock *TrueDest = BI.getSuccessor(0);
1457 BasicBlock *FalseDest = BI.getSuccessor(1);
1458 // Swap Destinations and condition...
1460 BI.setSuccessor(0, FalseDest);
1461 BI.setSuccessor(1, TrueDest);
1468 void InstCombiner::removeFromWorkList(Instruction *I) {
1469 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
1473 bool InstCombiner::runOnFunction(Function &F) {
1474 bool Changed = false;
1476 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
1478 while (!WorkList.empty()) {
1479 Instruction *I = WorkList.back(); // Get an instruction from the worklist
1480 WorkList.pop_back();
1482 // Check to see if we can DCE or ConstantPropagate the instruction...
1483 // Check to see if we can DIE the instruction...
1484 if (isInstructionTriviallyDead(I)) {
1485 // Add operands to the worklist...
1486 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
1487 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
1488 WorkList.push_back(Op);
1491 BasicBlock::iterator BBI = I;
1492 if (dceInstruction(BBI)) {
1493 removeFromWorkList(I);
1498 // Instruction isn't dead, see if we can constant propagate it...
1499 if (Constant *C = ConstantFoldInstruction(I)) {
1500 // Add operands to the worklist...
1501 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
1502 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
1503 WorkList.push_back(Op);
1504 ReplaceInstUsesWith(*I, C);
1507 BasicBlock::iterator BBI = I;
1508 if (dceInstruction(BBI)) {
1509 removeFromWorkList(I);
1514 // Now that we have an instruction, try combining it to simplify it...
1515 if (Instruction *Result = visit(*I)) {
1517 // Should we replace the old instruction with a new one?
1519 // Instructions can end up on the worklist more than once. Make sure
1520 // we do not process an instruction that has been deleted.
1521 removeFromWorkList(I);
1522 ReplaceInstWithInst(I, Result);
1524 BasicBlock::iterator II = I;
1526 // If the instruction was modified, it's possible that it is now dead.
1527 // if so, remove it.
1528 if (dceInstruction(II)) {
1529 // Instructions may end up in the worklist more than once. Erase them
1531 removeFromWorkList(I);
1537 WorkList.push_back(Result);
1538 AddUsesToWorkList(*Result);
1547 Pass *createInstructionCombiningPass() {
1548 return new InstCombiner();