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 (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
99 // X + (signbit) --> X ^ signbit
100 const APInt &Val = CI->getValue();
102 return BinaryOperator::CreateXor(LHS, RHS);
104 // See if SimplifyDemandedBits can simplify this. This handles stuff like
105 // (X & 254)+1 -> (X&254)|1
106 if (SimplifyDemandedInstructionBits(I))
109 // zext(bool) + C -> bool ? C + 1 : C
110 if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS))
111 if (ZI->getSrcTy()->isIntegerTy(1))
112 return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI);
114 Value *XorLHS = 0; ConstantInt *XorRHS = 0;
115 if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
116 uint32_t TySizeBits = I.getType()->getScalarSizeInBits();
117 const APInt &RHSVal = CI->getValue();
118 unsigned ExtendAmt = 0;
119 // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
120 // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
121 if (XorRHS->getValue() == -RHSVal) {
122 if (RHSVal.isPowerOf2())
123 ExtendAmt = TySizeBits - RHSVal.logBase2() - 1;
124 else if (XorRHS->getValue().isPowerOf2())
125 ExtendAmt = TySizeBits - XorRHS->getValue().logBase2() - 1;
129 APInt Mask = APInt::getHighBitsSet(TySizeBits, ExtendAmt);
130 if (!MaskedValueIsZero(XorLHS, Mask))
135 Constant *ShAmt = ConstantInt::get(I.getType(), ExtendAmt);
136 Value *NewShl = Builder->CreateShl(XorLHS, ShAmt, "sext");
137 return BinaryOperator::CreateAShr(NewShl, ShAmt);
142 if (isa<Constant>(RHS) && isa<PHINode>(LHS))
143 if (Instruction *NV = FoldOpIntoPhi(I))
146 if (I.getType()->isIntegerTy(1))
147 return BinaryOperator::CreateXor(LHS, RHS);
150 if (LHS == RHS && I.getType()->isIntegerTy())
151 return BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1));
154 // -A + -B --> -(A + B)
155 if (Value *LHSV = dyn_castNegVal(LHS)) {
156 if (Value *RHSV = dyn_castNegVal(RHS)) {
157 Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
158 return BinaryOperator::CreateNeg(NewAdd);
161 return BinaryOperator::CreateSub(RHS, LHSV);
165 if (!isa<Constant>(RHS))
166 if (Value *V = dyn_castNegVal(RHS))
167 return BinaryOperator::CreateSub(LHS, V);
171 if (Value *X = dyn_castFoldableMul(LHS, C2)) {
172 if (X == RHS) // X*C + X --> X * (C+1)
173 return BinaryOperator::CreateMul(RHS, AddOne(C2));
175 // X*C1 + X*C2 --> X * (C1+C2)
177 if (X == dyn_castFoldableMul(RHS, C1))
178 return BinaryOperator::CreateMul(X, ConstantExpr::getAdd(C1, C2));
181 // X + X*C --> X * (C+1)
182 if (dyn_castFoldableMul(RHS, C2) == LHS)
183 return BinaryOperator::CreateMul(LHS, AddOne(C2));
185 // A+B --> A|B iff A and B have no bits set in common.
186 if (const IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
187 APInt Mask = APInt::getAllOnesValue(IT->getBitWidth());
188 APInt LHSKnownOne(IT->getBitWidth(), 0);
189 APInt LHSKnownZero(IT->getBitWidth(), 0);
190 ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne);
191 if (LHSKnownZero != 0) {
192 APInt RHSKnownOne(IT->getBitWidth(), 0);
193 APInt RHSKnownZero(IT->getBitWidth(), 0);
194 ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
196 // No bits in common -> bitwise or.
197 if ((LHSKnownZero|RHSKnownZero).isAllOnesValue())
198 return BinaryOperator::CreateOr(LHS, RHS);
202 // W*X + Y*Z --> W * (X+Z) iff W == Y
204 Value *W, *X, *Y, *Z;
205 if (match(LHS, m_Mul(m_Value(W), m_Value(X))) &&
206 match(RHS, m_Mul(m_Value(Y), m_Value(Z)))) {
219 Value *NewAdd = Builder->CreateAdd(X, Z, LHS->getName());
220 return BinaryOperator::CreateMul(W, NewAdd);
225 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
227 if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X
228 return BinaryOperator::CreateSub(SubOne(CRHS), X);
230 // (X & FF00) + xx00 -> (X+xx00) & FF00
231 if (LHS->hasOneUse() &&
232 match(LHS, m_And(m_Value(X), m_ConstantInt(C2))) &&
233 CRHS->getValue() == (CRHS->getValue() & C2->getValue())) {
234 // See if all bits from the first bit set in the Add RHS up are included
235 // in the mask. First, get the rightmost bit.
236 const APInt &AddRHSV = CRHS->getValue();
238 // Form a mask of all bits from the lowest bit added through the top.
239 APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1));
241 // See if the and mask includes all of these bits.
242 APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue());
244 if (AddRHSHighBits == AddRHSHighBitsAnd) {
245 // Okay, the xform is safe. Insert the new add pronto.
246 Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName());
247 return BinaryOperator::CreateAnd(NewAdd, C2);
251 // Try to fold constant add into select arguments.
252 if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
253 if (Instruction *R = FoldOpIntoSelect(I, SI))
257 // add (select X 0 (sub n A)) A --> select X A n
259 SelectInst *SI = dyn_cast<SelectInst>(LHS);
262 SI = dyn_cast<SelectInst>(RHS);
265 if (SI && SI->hasOneUse()) {
266 Value *TV = SI->getTrueValue();
267 Value *FV = SI->getFalseValue();
270 // Can we fold the add into the argument of the select?
271 // We check both true and false select arguments for a matching subtract.
272 if (match(FV, m_Zero()) && match(TV, m_Sub(m_Value(N), m_Specific(A))))
273 // Fold the add into the true select value.
274 return SelectInst::Create(SI->getCondition(), N, A);
276 if (match(TV, m_Zero()) && match(FV, m_Sub(m_Value(N), m_Specific(A))))
277 // Fold the add into the false select value.
278 return SelectInst::Create(SI->getCondition(), A, N);
282 // Check for (add (sext x), y), see if we can merge this into an
283 // integer add followed by a sext.
284 if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) {
285 // (add (sext x), cst) --> (sext (add x, cst'))
286 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
288 ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
289 if (LHSConv->hasOneUse() &&
290 ConstantExpr::getSExt(CI, I.getType()) == RHSC &&
291 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
292 // Insert the new, smaller add.
293 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
295 return new SExtInst(NewAdd, I.getType());
299 // (add (sext x), (sext y)) --> (sext (add int x, y))
300 if (SExtInst *RHSConv = dyn_cast<SExtInst>(RHS)) {
301 // Only do this if x/y have the same type, if at last one of them has a
302 // single use (so we don't increase the number of sexts), and if the
303 // integer add will not overflow.
304 if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
305 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
306 WillNotOverflowSignedAdd(LHSConv->getOperand(0),
307 RHSConv->getOperand(0))) {
308 // Insert the new integer add.
309 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
310 RHSConv->getOperand(0), "addconv");
311 return new SExtInst(NewAdd, I.getType());
316 return Changed ? &I : 0;
319 Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
320 bool Changed = SimplifyAssociativeOrCommutative(I);
321 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
323 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
325 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
326 if (CFP->isExactlyValue(ConstantFP::getNegativeZero
327 (I.getType())->getValueAPF()))
328 return ReplaceInstUsesWith(I, LHS);
331 if (isa<PHINode>(LHS))
332 if (Instruction *NV = FoldOpIntoPhi(I))
337 // -A + -B --> -(A + B)
338 if (Value *LHSV = dyn_castFNegVal(LHS))
339 return BinaryOperator::CreateFSub(RHS, LHSV);
342 if (!isa<Constant>(RHS))
343 if (Value *V = dyn_castFNegVal(RHS))
344 return BinaryOperator::CreateFSub(LHS, V);
346 // Check for X+0.0. Simplify it to X if we know X is not -0.0.
347 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS))
348 if (CFP->getValueAPF().isPosZero() && CannotBeNegativeZero(LHS))
349 return ReplaceInstUsesWith(I, LHS);
351 // Check for (fadd double (sitofp x), y), see if we can merge this into an
352 // integer add followed by a promotion.
353 if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) {
354 // (fadd double (sitofp x), fpcst) --> (sitofp (add int x, intcst))
355 // ... if the constant fits in the integer value. This is useful for things
356 // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer
357 // requires a constant pool load, and generally allows the add to be better
359 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS)) {
361 ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType());
362 if (LHSConv->hasOneUse() &&
363 ConstantExpr::getSIToFP(CI, I.getType()) == CFP &&
364 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
365 // Insert the new integer add.
366 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
368 return new SIToFPInst(NewAdd, I.getType());
372 // (fadd double (sitofp x), (sitofp y)) --> (sitofp (add int x, y))
373 if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) {
374 // Only do this if x/y have the same type, if at last one of them has a
375 // single use (so we don't increase the number of int->fp conversions),
376 // and if the integer add will not overflow.
377 if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
378 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
379 WillNotOverflowSignedAdd(LHSConv->getOperand(0),
380 RHSConv->getOperand(0))) {
381 // Insert the new integer add.
382 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
383 RHSConv->getOperand(0),"addconv");
384 return new SIToFPInst(NewAdd, I.getType());
389 return Changed ? &I : 0;
393 /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
394 /// code necessary to compute the offset from the base pointer (without adding
395 /// in the base pointer). Return the result as a signed integer of intptr size.
396 Value *InstCombiner::EmitGEPOffset(User *GEP) {
397 TargetData &TD = *getTargetData();
398 gep_type_iterator GTI = gep_type_begin(GEP);
399 const Type *IntPtrTy = TD.getIntPtrType(GEP->getContext());
400 Value *Result = Constant::getNullValue(IntPtrTy);
402 // If the GEP is inbounds, we know that none of the addressing operations will
403 // overflow in an unsigned sense.
404 bool isInBounds = cast<GEPOperator>(GEP)->isInBounds();
406 // Build a mask for high order bits.
407 unsigned IntPtrWidth = TD.getPointerSizeInBits();
408 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
410 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
413 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
414 if (ConstantInt *OpC = dyn_cast<ConstantInt>(Op)) {
415 if (OpC->isZero()) continue;
417 // Handle a struct index, which adds its field offset to the pointer.
418 if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
419 Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
422 Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
423 GEP->getName()+".offs");
427 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
429 ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
430 Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
431 // Emit an add instruction.
432 Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
435 // Convert to correct type.
436 if (Op->getType() != IntPtrTy)
437 Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
439 // We'll let instcombine(mul) convert this to a shl if possible.
440 Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
441 GEP->getName()+".idx", isInBounds /*NUW*/);
444 // Emit an add instruction.
445 Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
453 /// Optimize pointer differences into the same array into a size. Consider:
454 /// &A[10] - &A[0]: we should compile this to "10". LHS/RHS are the pointer
455 /// operands to the ptrtoint instructions for the LHS/RHS of the subtract.
457 Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS,
459 assert(TD && "Must have target data info for this");
461 // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize
463 bool Swapped = false;
464 GetElementPtrInst *GEP = 0;
465 ConstantExpr *CstGEP = 0;
467 // TODO: Could also optimize &A[i] - &A[j] -> "i-j", and "&A.foo[i] - &A.foo".
468 // For now we require one side to be the base pointer "A" or a constant
469 // expression derived from it.
470 if (GetElementPtrInst *LHSGEP = dyn_cast<GetElementPtrInst>(LHS)) {
472 if (LHSGEP->getOperand(0) == RHS) {
475 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(RHS)) {
476 // (gep X, ...) - (ce_gep X, ...)
477 if (CE->getOpcode() == Instruction::GetElementPtr &&
478 LHSGEP->getOperand(0) == CE->getOperand(0)) {
486 if (GetElementPtrInst *RHSGEP = dyn_cast<GetElementPtrInst>(RHS)) {
488 if (RHSGEP->getOperand(0) == LHS) {
491 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(LHS)) {
492 // (ce_gep X, ...) - (gep X, ...)
493 if (CE->getOpcode() == Instruction::GetElementPtr &&
494 RHSGEP->getOperand(0) == CE->getOperand(0)) {
505 // Emit the offset of the GEP and an intptr_t.
506 Value *Result = EmitGEPOffset(GEP);
508 // If we had a constant expression GEP on the other side offsetting the
509 // pointer, subtract it from the offset we have.
511 Value *CstOffset = EmitGEPOffset(CstGEP);
512 Result = Builder->CreateSub(Result, CstOffset);
516 // If we have p - gep(p, ...) then we have to negate the result.
518 Result = Builder->CreateNeg(Result, "diff.neg");
520 return Builder->CreateIntCast(Result, Ty, true);
524 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
525 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
527 if (Value *V = SimplifySubInst(Op0, Op1, I.hasNoSignedWrap(),
528 I.hasNoUnsignedWrap(), TD))
529 return ReplaceInstUsesWith(I, V);
531 // (A*B)-(A*C) -> A*(B-C) etc
532 if (Value *V = SimplifyUsingDistributiveLaws(I))
533 return ReplaceInstUsesWith(I, V);
535 // If this is a 'B = x-(-A)', change to B = x+A. This preserves NSW/NUW.
536 if (Value *V = dyn_castNegVal(Op1)) {
537 BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);
538 Res->setHasNoSignedWrap(I.hasNoSignedWrap());
539 Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
543 if (I.getType()->isIntegerTy(1))
544 return BinaryOperator::CreateXor(Op0, Op1);
546 // Replace (-1 - A) with (~A).
547 if (match(Op0, m_AllOnes()))
548 return BinaryOperator::CreateNot(Op1);
550 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
551 // C - ~X == X + (1+C)
553 if (match(Op1, m_Not(m_Value(X))))
554 return BinaryOperator::CreateAdd(X, AddOne(C));
556 // -(X >>u 31) -> (X >>s 31)
557 // -(X >>s 31) -> (X >>u 31)
559 Value *X; ConstantInt *CI;
560 if (match(Op1, m_LShr(m_Value(X), m_ConstantInt(CI))) &&
561 // Verify we are shifting out everything but the sign bit.
562 CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1)
563 return BinaryOperator::CreateAShr(X, CI);
565 if (match(Op1, m_AShr(m_Value(X), m_ConstantInt(CI))) &&
566 // Verify we are shifting out everything but the sign bit.
567 CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1)
568 return BinaryOperator::CreateLShr(X, CI);
571 // Try to fold constant sub into select arguments.
572 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
573 if (Instruction *R = FoldOpIntoSelect(I, SI))
576 // C - zext(bool) -> bool ? C - 1 : C
577 if (ZExtInst *ZI = dyn_cast<ZExtInst>(Op1))
578 if (ZI->getSrcTy()->isIntegerTy(1))
579 return SelectInst::Create(ZI->getOperand(0), SubOne(C), C);
581 // C-(X+C2) --> (C-C2)-X
583 if (match(Op1, m_Add(m_Value(X), m_ConstantInt(C2))))
584 return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X);
589 // X-(X+Y) == -Y X-(Y+X) == -Y
590 if (match(Op1, m_Add(m_Specific(Op0), m_Value(Y))) ||
591 match(Op1, m_Add(m_Value(Y), m_Specific(Op0))))
592 return BinaryOperator::CreateNeg(Y);
595 if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y))))
596 return BinaryOperator::CreateNeg(Y);
599 if (Op1->hasOneUse()) {
600 Value *X = 0, *Y = 0, *Z = 0;
604 // (X - (Y - Z)) --> (X + (Z - Y)).
605 if (match(Op1, m_Sub(m_Value(Y), m_Value(Z))))
606 return BinaryOperator::CreateAdd(Op0,
607 Builder->CreateSub(Z, Y, Op1->getName()));
609 // (X - (X & Y)) --> (X & ~Y)
611 if (match(Op1, m_And(m_Value(Y), m_Specific(Op0))) ||
612 match(Op1, m_And(m_Specific(Op0), m_Value(Y))))
613 return BinaryOperator::CreateAnd(Op0,
614 Builder->CreateNot(Y, Y->getName() + ".not"));
616 // 0 - (X sdiv C) -> (X sdiv -C)
617 if (match(Op1, m_SDiv(m_Value(X), m_Constant(C))) &&
618 match(Op0, m_Zero()))
619 return BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C));
621 // 0 - (X << Y) -> (-X << Y) when X is freely negatable.
622 if (match(Op1, m_Shl(m_Value(X), m_Value(Y))) && match(Op0, m_Zero()))
623 if (Value *XNeg = dyn_castNegVal(X))
624 return BinaryOperator::CreateShl(XNeg, Y);
626 // X - X*C --> X * (1-C)
627 if (match(Op1, m_Mul(m_Specific(Op0), m_ConstantInt(CI)))) {
628 Constant *CP1 = ConstantExpr::getSub(ConstantInt::get(I.getType(),1), CI);
629 return BinaryOperator::CreateMul(Op0, CP1);
632 // X - X<<C --> X * (1-(1<<C))
633 if (match(Op1, m_Shl(m_Specific(Op0), m_ConstantInt(CI)))) {
634 Constant *One = ConstantInt::get(I.getType(), 1);
635 C = ConstantExpr::getSub(One, ConstantExpr::getShl(One, CI));
636 return BinaryOperator::CreateMul(Op0, C);
639 // X - A*-B -> X + A*B
640 // X - -A*B -> X + A*B
642 if (match(Op1, m_Mul(m_Value(A), m_Neg(m_Value(B)))) ||
643 match(Op1, m_Mul(m_Neg(m_Value(A)), m_Value(B))))
644 return BinaryOperator::CreateAdd(Op0, Builder->CreateMul(A, B));
646 // X - A*CI -> X + A*-CI
647 // X - CI*A -> X + A*-CI
648 if (match(Op1, m_Mul(m_Value(A), m_ConstantInt(CI))) ||
649 match(Op1, m_Mul(m_ConstantInt(CI), m_Value(A)))) {
650 Value *NewMul = Builder->CreateMul(A, ConstantExpr::getNeg(CI));
651 return BinaryOperator::CreateAdd(Op0, NewMul);
656 if (Value *X = dyn_castFoldableMul(Op0, C1)) {
657 if (X == Op1) // X*C - X --> X * (C-1)
658 return BinaryOperator::CreateMul(Op1, SubOne(C1));
660 ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2)
661 if (X == dyn_castFoldableMul(Op1, C2))
662 return BinaryOperator::CreateMul(X, ConstantExpr::getSub(C1, C2));
665 // Optimize pointer differences into the same array into a size. Consider:
666 // &A[10] - &A[0]: we should compile this to "10".
668 Value *LHSOp, *RHSOp;
669 if (match(Op0, m_PtrToInt(m_Value(LHSOp))) &&
670 match(Op1, m_PtrToInt(m_Value(RHSOp))))
671 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
672 return ReplaceInstUsesWith(I, Res);
674 // trunc(p)-trunc(q) -> trunc(p-q)
675 if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) &&
676 match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp)))))
677 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
678 return ReplaceInstUsesWith(I, Res);
684 Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
685 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
687 // If this is a 'B = x-(-A)', change to B = x+A...
688 if (Value *V = dyn_castFNegVal(Op1))
689 return BinaryOperator::CreateFAdd(Op0, V);