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()->isInteger())
39 if (Instruction *I = dyn_cast<Instruction>(V)) {
40 if (I->getOpcode() == Instruction::Mul)
41 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1))))
42 return I->getOperand(0);
43 if (I->getOpcode() == Instruction::Shl)
44 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) {
45 // The multiplier is really 1 << CST.
46 uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
47 uint32_t CSTVal = CST->getLimitedValue(BitWidth);
48 CST = ConstantInt::get(V->getType()->getContext(),
49 APInt(BitWidth, 1).shl(CSTVal));
50 return I->getOperand(0);
57 /// WillNotOverflowSignedAdd - Return true if we can prove that:
58 /// (sext (add LHS, RHS)) === (add (sext LHS), (sext RHS))
59 /// This basically requires proving that the add in the original type would not
60 /// overflow to change the sign bit or have a carry out.
61 bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS) {
62 // There are different heuristics we can use for this. Here are some simple
65 // Add has the property that adding any two 2's complement numbers can only
66 // have one carry bit which can change a sign. As such, if LHS and RHS each
67 // have at least two sign bits, we know that the addition of the two values
68 // will sign extend fine.
69 if (ComputeNumSignBits(LHS) > 1 && ComputeNumSignBits(RHS) > 1)
73 // If one of the operands only has one non-zero bit, and if the other operand
74 // has a known-zero bit in a more significant place than it (not including the
75 // sign bit) the ripple may go up to and fill the zero, but won't change the
76 // sign. For example, (X & ~4) + 1.
83 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
84 bool Changed = SimplifyCommutative(I);
85 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
87 if (Value *V = SimplifyAddInst(LHS, RHS, I.hasNoSignedWrap(),
88 I.hasNoUnsignedWrap(), TD))
89 return ReplaceInstUsesWith(I, V);
92 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
93 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
94 // X + (signbit) --> X ^ signbit
95 const APInt& Val = CI->getValue();
96 uint32_t BitWidth = Val.getBitWidth();
97 if (Val == APInt::getSignBit(BitWidth))
98 return BinaryOperator::CreateXor(LHS, RHS);
100 // See if SimplifyDemandedBits can simplify this. This handles stuff like
101 // (X & 254)+1 -> (X&254)|1
102 if (SimplifyDemandedInstructionBits(I))
105 // zext(bool) + C -> bool ? C + 1 : C
106 if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS))
107 if (ZI->getSrcTy() == Type::getInt1Ty(I.getContext()))
108 return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI);
111 if (isa<PHINode>(LHS))
112 if (Instruction *NV = FoldOpIntoPhi(I))
115 ConstantInt *XorRHS = 0;
117 if (isa<ConstantInt>(RHSC) &&
118 match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
119 uint32_t TySizeBits = I.getType()->getScalarSizeInBits();
120 const APInt& RHSVal = cast<ConstantInt>(RHSC)->getValue();
122 uint32_t Size = TySizeBits / 2;
123 APInt C0080Val(APInt(TySizeBits, 1ULL).shl(Size - 1));
124 APInt CFF80Val(-C0080Val);
126 if (TySizeBits > Size) {
127 // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
128 // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
129 if ((RHSVal == CFF80Val && XorRHS->getValue() == C0080Val) ||
130 (RHSVal == C0080Val && XorRHS->getValue() == CFF80Val)) {
131 // This is a sign extend if the top bits are known zero.
132 if (!MaskedValueIsZero(XorLHS,
133 APInt::getHighBitsSet(TySizeBits, TySizeBits - Size)))
134 Size = 0; // Not a sign ext, but can't be any others either.
139 C0080Val = APIntOps::lshr(C0080Val, Size);
140 CFF80Val = APIntOps::ashr(CFF80Val, Size);
143 // FIXME: This shouldn't be necessary. When the backends can handle types
144 // with funny bit widths then this switch statement should be removed. It
145 // is just here to get the size of the "middle" type back up to something
146 // that the back ends can handle.
147 const Type *MiddleType = 0;
152 case 8: MiddleType = IntegerType::get(I.getContext(), Size); break;
155 Value *NewTrunc = Builder->CreateTrunc(XorLHS, MiddleType, "sext");
156 return new SExtInst(NewTrunc, I.getType(), I.getName());
161 if (I.getType() == Type::getInt1Ty(I.getContext()))
162 return BinaryOperator::CreateXor(LHS, RHS);
164 if (I.getType()->isInteger()) {
167 return BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1));
169 if (Instruction *RHSI = dyn_cast<Instruction>(RHS)) {
170 if (RHSI->getOpcode() == Instruction::Sub)
171 if (LHS == RHSI->getOperand(1)) // A + (B - A) --> B
172 return ReplaceInstUsesWith(I, RHSI->getOperand(0));
174 if (Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
175 if (LHSI->getOpcode() == Instruction::Sub)
176 if (RHS == LHSI->getOperand(1)) // (B - A) + A --> B
177 return ReplaceInstUsesWith(I, LHSI->getOperand(0));
182 // -A + -B --> -(A + B)
183 if (Value *LHSV = dyn_castNegVal(LHS)) {
184 if (LHS->getType()->isIntOrIntVector()) {
185 if (Value *RHSV = dyn_castNegVal(RHS)) {
186 Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
187 return BinaryOperator::CreateNeg(NewAdd);
191 return BinaryOperator::CreateSub(RHS, LHSV);
195 if (!isa<Constant>(RHS))
196 if (Value *V = dyn_castNegVal(RHS))
197 return BinaryOperator::CreateSub(LHS, V);
201 if (Value *X = dyn_castFoldableMul(LHS, C2)) {
202 if (X == RHS) // X*C + X --> X * (C+1)
203 return BinaryOperator::CreateMul(RHS, AddOne(C2));
205 // X*C1 + X*C2 --> X * (C1+C2)
207 if (X == dyn_castFoldableMul(RHS, C1))
208 return BinaryOperator::CreateMul(X, ConstantExpr::getAdd(C1, C2));
211 // X + X*C --> X * (C+1)
212 if (dyn_castFoldableMul(RHS, C2) == LHS)
213 return BinaryOperator::CreateMul(LHS, AddOne(C2));
215 // X + ~X --> -1 since ~X = -X-1
216 if (match(LHS, m_Not(m_Specific(RHS))) ||
217 match(RHS, m_Not(m_Specific(LHS))))
218 return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
220 // A+B --> A|B iff A and B have no bits set in common.
221 if (const IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
222 APInt Mask = APInt::getAllOnesValue(IT->getBitWidth());
223 APInt LHSKnownOne(IT->getBitWidth(), 0);
224 APInt LHSKnownZero(IT->getBitWidth(), 0);
225 ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne);
226 if (LHSKnownZero != 0) {
227 APInt RHSKnownOne(IT->getBitWidth(), 0);
228 APInt RHSKnownZero(IT->getBitWidth(), 0);
229 ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
231 // No bits in common -> bitwise or.
232 if ((LHSKnownZero|RHSKnownZero).isAllOnesValue())
233 return BinaryOperator::CreateOr(LHS, RHS);
237 // W*X + Y*Z --> W * (X+Z) iff W == Y
238 if (I.getType()->isIntOrIntVector()) {
239 Value *W, *X, *Y, *Z;
240 if (match(LHS, m_Mul(m_Value(W), m_Value(X))) &&
241 match(RHS, m_Mul(m_Value(Y), m_Value(Z)))) {
254 Value *NewAdd = Builder->CreateAdd(X, Z, LHS->getName());
255 return BinaryOperator::CreateMul(W, NewAdd);
260 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
262 if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X
263 return BinaryOperator::CreateSub(SubOne(CRHS), X);
265 // (X & FF00) + xx00 -> (X+xx00) & FF00
266 if (LHS->hasOneUse() &&
267 match(LHS, m_And(m_Value(X), m_ConstantInt(C2)))) {
268 Constant *Anded = ConstantExpr::getAnd(CRHS, C2);
270 // See if all bits from the first bit set in the Add RHS up are included
271 // in the mask. First, get the rightmost bit.
272 const APInt &AddRHSV = CRHS->getValue();
274 // Form a mask of all bits from the lowest bit added through the top.
275 APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1));
277 // See if the and mask includes all of these bits.
278 APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue());
280 if (AddRHSHighBits == AddRHSHighBitsAnd) {
281 // Okay, the xform is safe. Insert the new add pronto.
282 Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName());
283 return BinaryOperator::CreateAnd(NewAdd, C2);
288 // Try to fold constant add into select arguments.
289 if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
290 if (Instruction *R = FoldOpIntoSelect(I, SI))
294 // add (select X 0 (sub n A)) A --> select X A n
296 SelectInst *SI = dyn_cast<SelectInst>(LHS);
299 SI = dyn_cast<SelectInst>(RHS);
302 if (SI && SI->hasOneUse()) {
303 Value *TV = SI->getTrueValue();
304 Value *FV = SI->getFalseValue();
307 // Can we fold the add into the argument of the select?
308 // We check both true and false select arguments for a matching subtract.
309 if (match(FV, m_Zero()) &&
310 match(TV, m_Sub(m_Value(N), m_Specific(A))))
311 // Fold the add into the true select value.
312 return SelectInst::Create(SI->getCondition(), N, A);
313 if (match(TV, m_Zero()) &&
314 match(FV, m_Sub(m_Value(N), m_Specific(A))))
315 // Fold the add into the false select value.
316 return SelectInst::Create(SI->getCondition(), A, N);
320 // Check for (add (sext x), y), see if we can merge this into an
321 // integer add followed by a sext.
322 if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) {
323 // (add (sext x), cst) --> (sext (add x, cst'))
324 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
326 ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
327 if (LHSConv->hasOneUse() &&
328 ConstantExpr::getSExt(CI, I.getType()) == RHSC &&
329 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
330 // Insert the new, smaller add.
331 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
333 return new SExtInst(NewAdd, I.getType());
337 // (add (sext x), (sext y)) --> (sext (add int x, y))
338 if (SExtInst *RHSConv = dyn_cast<SExtInst>(RHS)) {
339 // Only do this if x/y have the same type, if at last one of them has a
340 // single use (so we don't increase the number of sexts), and if the
341 // integer add will not overflow.
342 if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
343 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
344 WillNotOverflowSignedAdd(LHSConv->getOperand(0),
345 RHSConv->getOperand(0))) {
346 // Insert the new integer add.
347 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
348 RHSConv->getOperand(0), "addconv");
349 return new SExtInst(NewAdd, I.getType());
354 return Changed ? &I : 0;
357 Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
358 bool Changed = SimplifyCommutative(I);
359 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
361 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
363 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
364 if (CFP->isExactlyValue(ConstantFP::getNegativeZero
365 (I.getType())->getValueAPF()))
366 return ReplaceInstUsesWith(I, LHS);
369 if (isa<PHINode>(LHS))
370 if (Instruction *NV = FoldOpIntoPhi(I))
375 // -A + -B --> -(A + B)
376 if (Value *LHSV = dyn_castFNegVal(LHS))
377 return BinaryOperator::CreateFSub(RHS, LHSV);
380 if (!isa<Constant>(RHS))
381 if (Value *V = dyn_castFNegVal(RHS))
382 return BinaryOperator::CreateFSub(LHS, V);
384 // Check for X+0.0. Simplify it to X if we know X is not -0.0.
385 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS))
386 if (CFP->getValueAPF().isPosZero() && CannotBeNegativeZero(LHS))
387 return ReplaceInstUsesWith(I, LHS);
389 // Check for (add double (sitofp x), y), see if we can merge this into an
390 // integer add followed by a promotion.
391 if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) {
392 // (add double (sitofp x), fpcst) --> (sitofp (add int x, intcst))
393 // ... if the constant fits in the integer value. This is useful for things
394 // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer
395 // requires a constant pool load, and generally allows the add to be better
397 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS)) {
399 ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType());
400 if (LHSConv->hasOneUse() &&
401 ConstantExpr::getSIToFP(CI, I.getType()) == CFP &&
402 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
403 // Insert the new integer add.
404 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
406 return new SIToFPInst(NewAdd, I.getType());
410 // (add double (sitofp x), (sitofp y)) --> (sitofp (add int x, y))
411 if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) {
412 // Only do this if x/y have the same type, if at last one of them has a
413 // single use (so we don't increase the number of int->fp conversions),
414 // and if the integer add will not overflow.
415 if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
416 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
417 WillNotOverflowSignedAdd(LHSConv->getOperand(0),
418 RHSConv->getOperand(0))) {
419 // Insert the new integer add.
420 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
421 RHSConv->getOperand(0),"addconv");
422 return new SIToFPInst(NewAdd, I.getType());
427 return Changed ? &I : 0;
431 /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
432 /// code necessary to compute the offset from the base pointer (without adding
433 /// in the base pointer). Return the result as a signed integer of intptr size.
434 Value *InstCombiner::EmitGEPOffset(User *GEP) {
435 TargetData &TD = *getTargetData();
436 gep_type_iterator GTI = gep_type_begin(GEP);
437 const Type *IntPtrTy = TD.getIntPtrType(GEP->getContext());
438 Value *Result = Constant::getNullValue(IntPtrTy);
440 // Build a mask for high order bits.
441 unsigned IntPtrWidth = TD.getPointerSizeInBits();
442 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
444 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
447 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
448 if (ConstantInt *OpC = dyn_cast<ConstantInt>(Op)) {
449 if (OpC->isZero()) continue;
451 // Handle a struct index, which adds its field offset to the pointer.
452 if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
453 Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
455 Result = Builder->CreateAdd(Result,
456 ConstantInt::get(IntPtrTy, Size),
457 GEP->getName()+".offs");
461 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
463 ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
464 Scale = ConstantExpr::getMul(OC, Scale);
465 // Emit an add instruction.
466 Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
469 // Convert to correct type.
470 if (Op->getType() != IntPtrTy)
471 Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
473 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
474 // We'll let instcombine(mul) convert this to a shl if possible.
475 Op = Builder->CreateMul(Op, Scale, GEP->getName()+".idx");
478 // Emit an add instruction.
479 Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
487 /// Optimize pointer differences into the same array into a size. Consider:
488 /// &A[10] - &A[0]: we should compile this to "10". LHS/RHS are the pointer
489 /// operands to the ptrtoint instructions for the LHS/RHS of the subtract.
491 Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS,
493 assert(TD && "Must have target data info for this");
495 // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize
497 bool Swapped = false;
498 GetElementPtrInst *GEP = 0;
499 ConstantExpr *CstGEP = 0;
501 // TODO: Could also optimize &A[i] - &A[j] -> "i-j", and "&A.foo[i] - &A.foo".
502 // For now we require one side to be the base pointer "A" or a constant
503 // expression derived from it.
504 if (GetElementPtrInst *LHSGEP = dyn_cast<GetElementPtrInst>(LHS)) {
506 if (LHSGEP->getOperand(0) == RHS) {
509 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(RHS)) {
510 // (gep X, ...) - (ce_gep X, ...)
511 if (CE->getOpcode() == Instruction::GetElementPtr &&
512 LHSGEP->getOperand(0) == CE->getOperand(0)) {
520 if (GetElementPtrInst *RHSGEP = dyn_cast<GetElementPtrInst>(RHS)) {
522 if (RHSGEP->getOperand(0) == LHS) {
525 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(LHS)) {
526 // (ce_gep X, ...) - (gep X, ...)
527 if (CE->getOpcode() == Instruction::GetElementPtr &&
528 RHSGEP->getOperand(0) == CE->getOperand(0)) {
539 // Emit the offset of the GEP and an intptr_t.
540 Value *Result = EmitGEPOffset(GEP);
542 // If we had a constant expression GEP on the other side offsetting the
543 // pointer, subtract it from the offset we have.
545 Value *CstOffset = EmitGEPOffset(CstGEP);
546 Result = Builder->CreateSub(Result, CstOffset);
550 // If we have p - gep(p, ...) then we have to negate the result.
552 Result = Builder->CreateNeg(Result, "diff.neg");
554 return Builder->CreateIntCast(Result, Ty, true);
558 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
559 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
561 if (Op0 == Op1) // sub X, X -> 0
562 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
564 // If this is a 'B = x-(-A)', change to B = x+A. This preserves NSW/NUW.
565 if (Value *V = dyn_castNegVal(Op1)) {
566 BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);
567 Res->setHasNoSignedWrap(I.hasNoSignedWrap());
568 Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
572 if (isa<UndefValue>(Op0))
573 return ReplaceInstUsesWith(I, Op0); // undef - X -> undef
574 if (isa<UndefValue>(Op1))
575 return ReplaceInstUsesWith(I, Op1); // X - undef -> undef
576 if (I.getType() == Type::getInt1Ty(I.getContext()))
577 return BinaryOperator::CreateXor(Op0, Op1);
579 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
580 // Replace (-1 - A) with (~A).
581 if (C->isAllOnesValue())
582 return BinaryOperator::CreateNot(Op1);
584 // C - ~X == X + (1+C)
586 if (match(Op1, m_Not(m_Value(X))))
587 return BinaryOperator::CreateAdd(X, AddOne(C));
589 // -(X >>u 31) -> (X >>s 31)
590 // -(X >>s 31) -> (X >>u 31)
592 if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op1)) {
593 if (SI->getOpcode() == Instruction::LShr) {
594 if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
595 // Check to see if we are shifting out everything but the sign bit.
596 if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
597 SI->getType()->getPrimitiveSizeInBits()-1) {
598 // Ok, the transformation is safe. Insert AShr.
599 return BinaryOperator::Create(Instruction::AShr,
600 SI->getOperand(0), CU, SI->getName());
603 } else if (SI->getOpcode() == Instruction::AShr) {
604 if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
605 // Check to see if we are shifting out everything but the sign bit.
606 if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
607 SI->getType()->getPrimitiveSizeInBits()-1) {
608 // Ok, the transformation is safe. Insert LShr.
609 return BinaryOperator::CreateLShr(
610 SI->getOperand(0), CU, SI->getName());
617 // Try to fold constant sub into select arguments.
618 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
619 if (Instruction *R = FoldOpIntoSelect(I, SI))
622 // C - zext(bool) -> bool ? C - 1 : C
623 if (ZExtInst *ZI = dyn_cast<ZExtInst>(Op1))
624 if (ZI->getSrcTy() == Type::getInt1Ty(I.getContext()))
625 return SelectInst::Create(ZI->getOperand(0), SubOne(C), C);
628 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
629 if (Op1I->getOpcode() == Instruction::Add) {
630 if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
631 return BinaryOperator::CreateNeg(Op1I->getOperand(1),
633 else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
634 return BinaryOperator::CreateNeg(Op1I->getOperand(0),
636 else if (ConstantInt *CI1 = dyn_cast<ConstantInt>(I.getOperand(0))) {
637 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(Op1I->getOperand(1)))
638 // C1-(X+C2) --> (C1-C2)-X
639 return BinaryOperator::CreateSub(
640 ConstantExpr::getSub(CI1, CI2), Op1I->getOperand(0));
644 if (Op1I->hasOneUse()) {
645 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
646 // is not used by anyone else...
648 if (Op1I->getOpcode() == Instruction::Sub) {
649 // Swap the two operands of the subexpr...
650 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
651 Op1I->setOperand(0, IIOp1);
652 Op1I->setOperand(1, IIOp0);
654 // Create the new top level add instruction...
655 return BinaryOperator::CreateAdd(Op0, Op1);
658 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
660 if (Op1I->getOpcode() == Instruction::And &&
661 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
662 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
664 Value *NewNot = Builder->CreateNot(OtherOp, "B.not");
665 return BinaryOperator::CreateAnd(Op0, NewNot);
668 // 0 - (X sdiv C) -> (X sdiv -C)
669 if (Op1I->getOpcode() == Instruction::SDiv)
670 if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
672 if (Constant *DivRHS = dyn_cast<Constant>(Op1I->getOperand(1)))
673 return BinaryOperator::CreateSDiv(Op1I->getOperand(0),
674 ConstantExpr::getNeg(DivRHS));
676 // X - X*C --> X * (1-C)
678 if (dyn_castFoldableMul(Op1I, C2) == Op0) {
680 ConstantExpr::getSub(ConstantInt::get(I.getType(), 1),
682 return BinaryOperator::CreateMul(Op0, CP1);
687 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
688 if (Op0I->getOpcode() == Instruction::Add) {
689 if (Op0I->getOperand(0) == Op1) // (Y+X)-Y == X
690 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
691 else if (Op0I->getOperand(1) == Op1) // (X+Y)-Y == X
692 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
693 } else if (Op0I->getOpcode() == Instruction::Sub) {
694 if (Op0I->getOperand(0) == Op1) // (X-Y)-X == -Y
695 return BinaryOperator::CreateNeg(Op0I->getOperand(1),
701 if (Value *X = dyn_castFoldableMul(Op0, C1)) {
702 if (X == Op1) // X*C - X --> X * (C-1)
703 return BinaryOperator::CreateMul(Op1, SubOne(C1));
705 ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2)
706 if (X == dyn_castFoldableMul(Op1, C2))
707 return BinaryOperator::CreateMul(X, ConstantExpr::getSub(C1, C2));
710 // Optimize pointer differences into the same array into a size. Consider:
711 // &A[10] - &A[0]: we should compile this to "10".
713 Value *LHSOp, *RHSOp;
714 if (match(Op0, m_PtrToInt(m_Value(LHSOp))) &&
715 match(Op1, m_PtrToInt(m_Value(RHSOp))))
716 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
717 return ReplaceInstUsesWith(I, Res);
719 // trunc(p)-trunc(q) -> trunc(p-q)
720 if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) &&
721 match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp)))))
722 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
723 return ReplaceInstUsesWith(I, Res);
729 Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
730 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
732 // If this is a 'B = x-(-A)', change to B = x+A...
733 if (Value *V = dyn_castFNegVal(Op1))
734 return BinaryOperator::CreateFAdd(Op0, V);
736 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
737 if (Op1I->getOpcode() == Instruction::FAdd) {
738 if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
739 return BinaryOperator::CreateFNeg(Op1I->getOperand(1),
741 else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
742 return BinaryOperator::CreateFNeg(Op1I->getOperand(0),