1 //===- InstCombineAddSub.cpp ----------------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the visit functions for add, fadd, sub, and fsub.
12 //===----------------------------------------------------------------------===//
14 #include "InstCombine.h"
15 #include "llvm/Analysis/InstructionSimplify.h"
16 #include "llvm/Target/TargetData.h"
17 #include "llvm/Support/GetElementPtrTypeIterator.h"
18 #include "llvm/Support/PatternMatch.h"
20 using namespace PatternMatch;
22 /// AddOne - Add one to a ConstantInt.
23 static Constant *AddOne(Constant *C) {
24 return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
26 /// SubOne - Subtract one from a ConstantInt.
27 static Constant *SubOne(ConstantInt *C) {
28 return ConstantInt::get(C->getContext(), C->getValue()-1);
32 // dyn_castFoldableMul - If this value is a multiply that can be folded into
33 // other computations (because it has a constant operand), return the
34 // non-constant operand of the multiply, and set CST to point to the multiplier.
35 // Otherwise, return null.
37 static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) {
38 if (!V->hasOneUse() || !V->getType()->isIntegerTy())
41 Instruction *I = dyn_cast<Instruction>(V);
44 if (I->getOpcode() == Instruction::Mul)
45 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1))))
46 return I->getOperand(0);
47 if (I->getOpcode() == Instruction::Shl)
48 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) {
49 // The multiplier is really 1 << CST.
50 uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
51 uint32_t CSTVal = CST->getLimitedValue(BitWidth);
52 CST = ConstantInt::get(V->getType()->getContext(),
53 APInt(BitWidth, 1).shl(CSTVal));
54 return I->getOperand(0);
60 /// WillNotOverflowSignedAdd - Return true if we can prove that:
61 /// (sext (add LHS, RHS)) === (add (sext LHS), (sext RHS))
62 /// This basically requires proving that the add in the original type would not
63 /// overflow to change the sign bit or have a carry out.
64 bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS) {
65 // There are different heuristics we can use for this. Here are some simple
68 // Add has the property that adding any two 2's complement numbers can only
69 // have one carry bit which can change a sign. As such, if LHS and RHS each
70 // have at least two sign bits, we know that the addition of the two values
71 // will sign extend fine.
72 if (ComputeNumSignBits(LHS) > 1 && ComputeNumSignBits(RHS) > 1)
76 // If one of the operands only has one non-zero bit, and if the other operand
77 // has a known-zero bit in a more significant place than it (not including the
78 // sign bit) the ripple may go up to and fill the zero, but won't change the
79 // sign. For example, (X & ~4) + 1.
86 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
87 bool Changed = SimplifyAssociativeOrCommutative(I);
88 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
90 if (Value *V = SimplifyAddInst(LHS, RHS, I.hasNoSignedWrap(),
91 I.hasNoUnsignedWrap(), TD))
92 return ReplaceInstUsesWith(I, V);
94 // (A*B)+(A*C) -> A*(B+C) etc
95 if (Value *V = SimplifyUsingDistributiveLaws(I))
96 return ReplaceInstUsesWith(I, V);
98 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
99 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
100 // X + (signbit) --> X ^ signbit
101 const APInt& Val = CI->getValue();
102 uint32_t BitWidth = Val.getBitWidth();
103 if (Val == APInt::getSignBit(BitWidth))
104 return BinaryOperator::CreateXor(LHS, RHS);
106 // See if SimplifyDemandedBits can simplify this. This handles stuff like
107 // (X & 254)+1 -> (X&254)|1
108 if (SimplifyDemandedInstructionBits(I))
111 // zext(bool) + C -> bool ? C + 1 : C
112 if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS))
113 if (ZI->getSrcTy() == Type::getInt1Ty(I.getContext()))
114 return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI);
117 if (isa<PHINode>(LHS))
118 if (Instruction *NV = FoldOpIntoPhi(I))
121 ConstantInt *XorRHS = 0;
123 if (isa<ConstantInt>(RHSC) &&
124 match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
125 uint32_t TySizeBits = I.getType()->getScalarSizeInBits();
126 const APInt& RHSVal = cast<ConstantInt>(RHSC)->getValue();
127 unsigned ExtendAmt = 0;
128 // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
129 // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
130 if (XorRHS->getValue() == -RHSVal) {
131 if (RHSVal.isPowerOf2())
132 ExtendAmt = TySizeBits - RHSVal.logBase2() - 1;
133 else if (XorRHS->getValue().isPowerOf2())
134 ExtendAmt = TySizeBits - XorRHS->getValue().logBase2() - 1;
138 APInt Mask = APInt::getHighBitsSet(TySizeBits, ExtendAmt);
139 if (!MaskedValueIsZero(XorLHS, Mask))
144 Constant *ShAmt = ConstantInt::get(I.getType(), ExtendAmt);
145 Value *NewShl = Builder->CreateShl(XorLHS, ShAmt, "sext");
146 return BinaryOperator::CreateAShr(NewShl, ShAmt);
151 if (I.getType()->isIntegerTy(1))
152 return BinaryOperator::CreateXor(LHS, RHS);
154 if (I.getType()->isIntegerTy()) {
157 return BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1));
161 // -A + -B --> -(A + B)
162 if (Value *LHSV = dyn_castNegVal(LHS)) {
163 if (LHS->getType()->isIntOrIntVectorTy()) {
164 if (Value *RHSV = dyn_castNegVal(RHS)) {
165 Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
166 return BinaryOperator::CreateNeg(NewAdd);
170 return BinaryOperator::CreateSub(RHS, LHSV);
174 if (!isa<Constant>(RHS))
175 if (Value *V = dyn_castNegVal(RHS))
176 return BinaryOperator::CreateSub(LHS, V);
180 if (Value *X = dyn_castFoldableMul(LHS, C2)) {
181 if (X == RHS) // X*C + X --> X * (C+1)
182 return BinaryOperator::CreateMul(RHS, AddOne(C2));
184 // X*C1 + X*C2 --> X * (C1+C2)
186 if (X == dyn_castFoldableMul(RHS, C1))
187 return BinaryOperator::CreateMul(X, ConstantExpr::getAdd(C1, C2));
190 // X + X*C --> X * (C+1)
191 if (dyn_castFoldableMul(RHS, C2) == LHS)
192 return BinaryOperator::CreateMul(LHS, AddOne(C2));
194 // A+B --> A|B iff A and B have no bits set in common.
195 if (const IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
196 APInt Mask = APInt::getAllOnesValue(IT->getBitWidth());
197 APInt LHSKnownOne(IT->getBitWidth(), 0);
198 APInt LHSKnownZero(IT->getBitWidth(), 0);
199 ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne);
200 if (LHSKnownZero != 0) {
201 APInt RHSKnownOne(IT->getBitWidth(), 0);
202 APInt RHSKnownZero(IT->getBitWidth(), 0);
203 ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
205 // No bits in common -> bitwise or.
206 if ((LHSKnownZero|RHSKnownZero).isAllOnesValue())
207 return BinaryOperator::CreateOr(LHS, RHS);
211 // W*X + Y*Z --> W * (X+Z) iff W == Y
212 if (I.getType()->isIntOrIntVectorTy()) {
213 Value *W, *X, *Y, *Z;
214 if (match(LHS, m_Mul(m_Value(W), m_Value(X))) &&
215 match(RHS, m_Mul(m_Value(Y), m_Value(Z)))) {
228 Value *NewAdd = Builder->CreateAdd(X, Z, LHS->getName());
229 return BinaryOperator::CreateMul(W, NewAdd);
234 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
236 if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X
237 return BinaryOperator::CreateSub(SubOne(CRHS), X);
239 // (X & FF00) + xx00 -> (X+xx00) & FF00
240 if (LHS->hasOneUse() &&
241 match(LHS, m_And(m_Value(X), m_ConstantInt(C2)))) {
242 Constant *Anded = ConstantExpr::getAnd(CRHS, C2);
244 // See if all bits from the first bit set in the Add RHS up are included
245 // in the mask. First, get the rightmost bit.
246 const APInt &AddRHSV = CRHS->getValue();
248 // Form a mask of all bits from the lowest bit added through the top.
249 APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1));
251 // See if the and mask includes all of these bits.
252 APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue());
254 if (AddRHSHighBits == AddRHSHighBitsAnd) {
255 // Okay, the xform is safe. Insert the new add pronto.
256 Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName());
257 return BinaryOperator::CreateAnd(NewAdd, C2);
262 // Try to fold constant add into select arguments.
263 if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
264 if (Instruction *R = FoldOpIntoSelect(I, SI))
268 // add (select X 0 (sub n A)) A --> select X A n
270 SelectInst *SI = dyn_cast<SelectInst>(LHS);
273 SI = dyn_cast<SelectInst>(RHS);
276 if (SI && SI->hasOneUse()) {
277 Value *TV = SI->getTrueValue();
278 Value *FV = SI->getFalseValue();
281 // Can we fold the add into the argument of the select?
282 // We check both true and false select arguments for a matching subtract.
283 if (match(FV, m_Zero()) &&
284 match(TV, m_Sub(m_Value(N), m_Specific(A))))
285 // Fold the add into the true select value.
286 return SelectInst::Create(SI->getCondition(), N, A);
287 if (match(TV, m_Zero()) &&
288 match(FV, m_Sub(m_Value(N), m_Specific(A))))
289 // Fold the add into the false select value.
290 return SelectInst::Create(SI->getCondition(), A, N);
294 // Check for (add (sext x), y), see if we can merge this into an
295 // integer add followed by a sext.
296 if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) {
297 // (add (sext x), cst) --> (sext (add x, cst'))
298 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
300 ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
301 if (LHSConv->hasOneUse() &&
302 ConstantExpr::getSExt(CI, I.getType()) == RHSC &&
303 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
304 // Insert the new, smaller add.
305 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
307 return new SExtInst(NewAdd, I.getType());
311 // (add (sext x), (sext y)) --> (sext (add int x, y))
312 if (SExtInst *RHSConv = dyn_cast<SExtInst>(RHS)) {
313 // Only do this if x/y have the same type, if at last one of them has a
314 // single use (so we don't increase the number of sexts), and if the
315 // integer add will not overflow.
316 if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
317 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
318 WillNotOverflowSignedAdd(LHSConv->getOperand(0),
319 RHSConv->getOperand(0))) {
320 // Insert the new integer add.
321 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
322 RHSConv->getOperand(0), "addconv");
323 return new SExtInst(NewAdd, I.getType());
328 return Changed ? &I : 0;
331 Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
332 bool Changed = SimplifyAssociativeOrCommutative(I);
333 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
335 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
337 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
338 if (CFP->isExactlyValue(ConstantFP::getNegativeZero
339 (I.getType())->getValueAPF()))
340 return ReplaceInstUsesWith(I, LHS);
343 if (isa<PHINode>(LHS))
344 if (Instruction *NV = FoldOpIntoPhi(I))
349 // -A + -B --> -(A + B)
350 if (Value *LHSV = dyn_castFNegVal(LHS))
351 return BinaryOperator::CreateFSub(RHS, LHSV);
354 if (!isa<Constant>(RHS))
355 if (Value *V = dyn_castFNegVal(RHS))
356 return BinaryOperator::CreateFSub(LHS, V);
358 // Check for X+0.0. Simplify it to X if we know X is not -0.0.
359 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS))
360 if (CFP->getValueAPF().isPosZero() && CannotBeNegativeZero(LHS))
361 return ReplaceInstUsesWith(I, LHS);
363 // Check for (fadd double (sitofp x), y), see if we can merge this into an
364 // integer add followed by a promotion.
365 if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) {
366 // (fadd double (sitofp x), fpcst) --> (sitofp (add int x, intcst))
367 // ... if the constant fits in the integer value. This is useful for things
368 // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer
369 // requires a constant pool load, and generally allows the add to be better
371 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS)) {
373 ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType());
374 if (LHSConv->hasOneUse() &&
375 ConstantExpr::getSIToFP(CI, I.getType()) == CFP &&
376 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
377 // Insert the new integer add.
378 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
380 return new SIToFPInst(NewAdd, I.getType());
384 // (fadd double (sitofp x), (sitofp y)) --> (sitofp (add int x, y))
385 if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) {
386 // Only do this if x/y have the same type, if at last one of them has a
387 // single use (so we don't increase the number of int->fp conversions),
388 // and if the integer add will not overflow.
389 if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
390 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
391 WillNotOverflowSignedAdd(LHSConv->getOperand(0),
392 RHSConv->getOperand(0))) {
393 // Insert the new integer add.
394 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
395 RHSConv->getOperand(0),"addconv");
396 return new SIToFPInst(NewAdd, I.getType());
401 return Changed ? &I : 0;
405 /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
406 /// code necessary to compute the offset from the base pointer (without adding
407 /// in the base pointer). Return the result as a signed integer of intptr size.
408 Value *InstCombiner::EmitGEPOffset(User *GEP) {
409 TargetData &TD = *getTargetData();
410 gep_type_iterator GTI = gep_type_begin(GEP);
411 const Type *IntPtrTy = TD.getIntPtrType(GEP->getContext());
412 Value *Result = Constant::getNullValue(IntPtrTy);
414 // Build a mask for high order bits.
415 unsigned IntPtrWidth = TD.getPointerSizeInBits();
416 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
418 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
421 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
422 if (ConstantInt *OpC = dyn_cast<ConstantInt>(Op)) {
423 if (OpC->isZero()) continue;
425 // Handle a struct index, which adds its field offset to the pointer.
426 if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
427 Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
429 Result = Builder->CreateAdd(Result,
430 ConstantInt::get(IntPtrTy, Size),
431 GEP->getName()+".offs");
435 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
437 ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
438 Scale = ConstantExpr::getMul(OC, Scale);
439 // Emit an add instruction.
440 Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
443 // Convert to correct type.
444 if (Op->getType() != IntPtrTy)
445 Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
447 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
448 // We'll let instcombine(mul) convert this to a shl if possible.
449 Op = Builder->CreateMul(Op, Scale, GEP->getName()+".idx");
452 // Emit an add instruction.
453 Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
461 /// Optimize pointer differences into the same array into a size. Consider:
462 /// &A[10] - &A[0]: we should compile this to "10". LHS/RHS are the pointer
463 /// operands to the ptrtoint instructions for the LHS/RHS of the subtract.
465 Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS,
467 assert(TD && "Must have target data info for this");
469 // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize
471 bool Swapped = false;
472 GetElementPtrInst *GEP = 0;
473 ConstantExpr *CstGEP = 0;
475 // TODO: Could also optimize &A[i] - &A[j] -> "i-j", and "&A.foo[i] - &A.foo".
476 // For now we require one side to be the base pointer "A" or a constant
477 // expression derived from it.
478 if (GetElementPtrInst *LHSGEP = dyn_cast<GetElementPtrInst>(LHS)) {
480 if (LHSGEP->getOperand(0) == RHS) {
483 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(RHS)) {
484 // (gep X, ...) - (ce_gep X, ...)
485 if (CE->getOpcode() == Instruction::GetElementPtr &&
486 LHSGEP->getOperand(0) == CE->getOperand(0)) {
494 if (GetElementPtrInst *RHSGEP = dyn_cast<GetElementPtrInst>(RHS)) {
496 if (RHSGEP->getOperand(0) == LHS) {
499 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(LHS)) {
500 // (ce_gep X, ...) - (gep X, ...)
501 if (CE->getOpcode() == Instruction::GetElementPtr &&
502 RHSGEP->getOperand(0) == CE->getOperand(0)) {
513 // Emit the offset of the GEP and an intptr_t.
514 Value *Result = EmitGEPOffset(GEP);
516 // If we had a constant expression GEP on the other side offsetting the
517 // pointer, subtract it from the offset we have.
519 Value *CstOffset = EmitGEPOffset(CstGEP);
520 Result = Builder->CreateSub(Result, CstOffset);
524 // If we have p - gep(p, ...) then we have to negate the result.
526 Result = Builder->CreateNeg(Result, "diff.neg");
528 return Builder->CreateIntCast(Result, Ty, true);
532 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
533 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
535 if (Value *V = SimplifySubInst(Op0, Op1, I.hasNoSignedWrap(),
536 I.hasNoUnsignedWrap(), TD))
537 return ReplaceInstUsesWith(I, V);
539 // (A*B)-(A*C) -> A*(B-C) etc
540 if (Value *V = SimplifyUsingDistributiveLaws(I))
541 return ReplaceInstUsesWith(I, V);
543 // If this is a 'B = x-(-A)', change to B = x+A. This preserves NSW/NUW.
544 if (Value *V = dyn_castNegVal(Op1)) {
545 BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);
546 Res->setHasNoSignedWrap(I.hasNoSignedWrap());
547 Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
551 if (I.getType()->isIntegerTy(1))
552 return BinaryOperator::CreateXor(Op0, Op1);
554 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
555 // Replace (-1 - A) with (~A).
556 if (C->isAllOnesValue())
557 return BinaryOperator::CreateNot(Op1);
559 // C - ~X == X + (1+C)
561 if (match(Op1, m_Not(m_Value(X))))
562 return BinaryOperator::CreateAdd(X, AddOne(C));
564 // -(X >>u 31) -> (X >>s 31)
565 // -(X >>s 31) -> (X >>u 31)
567 if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op1)) {
568 if (SI->getOpcode() == Instruction::LShr) {
569 if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
570 // Check to see if we are shifting out everything but the sign bit.
571 if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
572 SI->getType()->getPrimitiveSizeInBits()-1) {
573 // Ok, the transformation is safe. Insert AShr.
574 return BinaryOperator::Create(Instruction::AShr,
575 SI->getOperand(0), CU, SI->getName());
578 } else if (SI->getOpcode() == Instruction::AShr) {
579 if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
580 // Check to see if we are shifting out everything but the sign bit.
581 if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
582 SI->getType()->getPrimitiveSizeInBits()-1) {
583 // Ok, the transformation is safe. Insert LShr.
584 return BinaryOperator::CreateLShr(
585 SI->getOperand(0), CU, SI->getName());
592 // Try to fold constant sub into select arguments.
593 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
594 if (Instruction *R = FoldOpIntoSelect(I, SI))
597 // C - zext(bool) -> bool ? C - 1 : C
598 if (ZExtInst *ZI = dyn_cast<ZExtInst>(Op1))
599 if (ZI->getSrcTy() == Type::getInt1Ty(I.getContext()))
600 return SelectInst::Create(ZI->getOperand(0), SubOne(C), C);
603 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
604 if (Op1I->getOpcode() == Instruction::Add) {
605 if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
606 return BinaryOperator::CreateNeg(Op1I->getOperand(1),
608 else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
609 return BinaryOperator::CreateNeg(Op1I->getOperand(0),
611 else if (ConstantInt *CI1 = dyn_cast<ConstantInt>(I.getOperand(0))) {
612 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(Op1I->getOperand(1)))
613 // C1-(X+C2) --> (C1-C2)-X
614 return BinaryOperator::CreateSub(
615 ConstantExpr::getSub(CI1, CI2), Op1I->getOperand(0));
619 if (Op1I->hasOneUse()) {
620 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
621 // is not used by anyone else...
623 if (Op1I->getOpcode() == Instruction::Sub) {
624 // Swap the two operands of the subexpr...
625 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
626 Op1I->setOperand(0, IIOp1);
627 Op1I->setOperand(1, IIOp0);
629 // Create the new top level add instruction...
630 return BinaryOperator::CreateAdd(Op0, Op1);
633 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
635 if (Op1I->getOpcode() == Instruction::And &&
636 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
637 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
639 Value *NewNot = Builder->CreateNot(OtherOp, "B.not");
640 return BinaryOperator::CreateAnd(Op0, NewNot);
643 // 0 - (X sdiv C) -> (X sdiv -C)
644 if (Op1I->getOpcode() == Instruction::SDiv)
645 if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
647 if (Constant *DivRHS = dyn_cast<Constant>(Op1I->getOperand(1)))
648 return BinaryOperator::CreateSDiv(Op1I->getOperand(0),
649 ConstantExpr::getNeg(DivRHS));
651 // 0 - (C << X) -> (-C << X)
652 if (Op1I->getOpcode() == Instruction::Shl)
653 if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
655 if (Value *ShlLHSNeg = dyn_castNegVal(Op1I->getOperand(0)))
656 return BinaryOperator::CreateShl(ShlLHSNeg, Op1I->getOperand(1));
658 // X - X*C --> X * (1-C)
660 if (dyn_castFoldableMul(Op1I, C2) == Op0) {
662 ConstantExpr::getSub(ConstantInt::get(I.getType(), 1),
664 return BinaryOperator::CreateMul(Op0, CP1);
667 // X - A*-B -> X + A*B
668 // X - -A*B -> X + A*B
670 if (match(Op1I, m_Mul(m_Value(A), m_Neg(m_Value(B)))) ||
671 match(Op1I, m_Mul(m_Neg(m_Value(A)), m_Value(B)))) {
672 Value *NewMul = Builder->CreateMul(A, B);
673 return BinaryOperator::CreateAdd(Op0, NewMul);
676 // X - A*Cst -> X + A*-Cst
677 // X - Cst*A -> X + A*-Cst
679 if (match(Op1I, m_Mul(m_Value(A), m_ConstantInt(BCst))) ||
680 match(Op1I, m_Mul(m_ConstantInt(BCst), m_Value(A)))) {
681 Value *NewMul = Builder->CreateMul(A, ConstantExpr::getNeg(BCst));
682 return BinaryOperator::CreateAdd(Op0, NewMul);
687 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
688 if (Op0I->getOpcode() == Instruction::Sub) {
689 if (Op0I->getOperand(0) == Op1) // (X-Y)-X == -Y
690 return BinaryOperator::CreateNeg(Op0I->getOperand(1),
696 if (Value *X = dyn_castFoldableMul(Op0, C1)) {
697 if (X == Op1) // X*C - X --> X * (C-1)
698 return BinaryOperator::CreateMul(Op1, SubOne(C1));
700 ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2)
701 if (X == dyn_castFoldableMul(Op1, C2))
702 return BinaryOperator::CreateMul(X, ConstantExpr::getSub(C1, C2));
705 // Optimize pointer differences into the same array into a size. Consider:
706 // &A[10] - &A[0]: we should compile this to "10".
708 Value *LHSOp, *RHSOp;
709 if (match(Op0, m_PtrToInt(m_Value(LHSOp))) &&
710 match(Op1, m_PtrToInt(m_Value(RHSOp))))
711 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
712 return ReplaceInstUsesWith(I, Res);
714 // trunc(p)-trunc(q) -> trunc(p-q)
715 if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) &&
716 match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp)))))
717 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
718 return ReplaceInstUsesWith(I, Res);
724 Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
725 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
727 // If this is a 'B = x-(-A)', change to B = x+A...
728 if (Value *V = dyn_castFNegVal(Op1))
729 return BinaryOperator::CreateFAdd(Op0, V);