split add/sub out to its own file. Eliminate use of

dyn_castNotVal in the X+~X transform.  dyn_castNotVal is
dramatic overkill for what the xform needed.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92704 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 695 deletions

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index ee037a85b7..62f74210d5 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -464,701 +464,6 @@ Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I,
 }
 
 
-/// WillNotOverflowSignedAdd - Return true if we can prove that:
-///    (sext (add LHS, RHS))  === (add (sext LHS), (sext RHS))
-/// This basically requires proving that the add in the original type would not
-/// overflow to change the sign bit or have a carry out.
-bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS) {
-  // There are different heuristics we can use for this.  Here are some simple
-  // ones.
-  
-  // Add has the property that adding any two 2's complement numbers can only 
-  // have one carry bit which can change a sign.  As such, if LHS and RHS each
-  // have at least two sign bits, we know that the addition of the two values
-  // will sign extend fine.
-  if (ComputeNumSignBits(LHS) > 1 && ComputeNumSignBits(RHS) > 1)
-    return true;
-  
-  
-  // If one of the operands only has one non-zero bit, and if the other operand
-  // has a known-zero bit in a more significant place than it (not including the
-  // sign bit) the ripple may go up to and fill the zero, but won't change the
-  // sign.  For example, (X & ~4) + 1.
-  
-  // TODO: Implement.
-  
-  return false;
-}
-
-
-Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
-  bool Changed = SimplifyCommutative(I);
-  Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
-
-  if (Value *V = SimplifyAddInst(LHS, RHS, I.hasNoSignedWrap(),
-                                 I.hasNoUnsignedWrap(), TD))
-    return ReplaceInstUsesWith(I, V);
-
-  
-  if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
-    if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
-      // X + (signbit) --> X ^ signbit
-      const APInt& Val = CI->getValue();
-      uint32_t BitWidth = Val.getBitWidth();
-      if (Val == APInt::getSignBit(BitWidth))
-        return BinaryOperator::CreateXor(LHS, RHS);
-      
-      // See if SimplifyDemandedBits can simplify this.  This handles stuff like
-      // (X & 254)+1 -> (X&254)|1
-      if (SimplifyDemandedInstructionBits(I))
-        return &I;
-
-      // zext(bool) + C -> bool ? C + 1 : C
-      if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS))
-        if (ZI->getSrcTy() == Type::getInt1Ty(I.getContext()))
-          return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI);
-    }
-
-    if (isa<PHINode>(LHS))
-      if (Instruction *NV = FoldOpIntoPhi(I))
-        return NV;
-    
-    ConstantInt *XorRHS = 0;
-    Value *XorLHS = 0;
-    if (isa<ConstantInt>(RHSC) &&
-        match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
-      uint32_t TySizeBits = I.getType()->getScalarSizeInBits();
-      const APInt& RHSVal = cast<ConstantInt>(RHSC)->getValue();
-      
-      uint32_t Size = TySizeBits / 2;
-      APInt C0080Val(APInt(TySizeBits, 1ULL).shl(Size - 1));
-      APInt CFF80Val(-C0080Val);
-      do {
-        if (TySizeBits > Size) {
-          // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
-          // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
-          if ((RHSVal == CFF80Val && XorRHS->getValue() == C0080Val) ||
-              (RHSVal == C0080Val && XorRHS->getValue() == CFF80Val)) {
-            // This is a sign extend if the top bits are known zero.
-            if (!MaskedValueIsZero(XorLHS, 
-                   APInt::getHighBitsSet(TySizeBits, TySizeBits - Size)))
-              Size = 0;  // Not a sign ext, but can't be any others either.
-            break;
-          }
-        }
-        Size >>= 1;
-        C0080Val = APIntOps::lshr(C0080Val, Size);
-        CFF80Val = APIntOps::ashr(CFF80Val, Size);
-      } while (Size >= 1);
-      
-      // FIXME: This shouldn't be necessary. When the backends can handle types
-      // with funny bit widths then this switch statement should be removed. It
-      // is just here to get the size of the "middle" type back up to something
-      // that the back ends can handle.
-      const Type *MiddleType = 0;
-      switch (Size) {
-        default: break;
-        case 32:
-        case 16:
-        case  8: MiddleType = IntegerType::get(I.getContext(), Size); break;
-      }
-      if (MiddleType) {
-        Value *NewTrunc = Builder->CreateTrunc(XorLHS, MiddleType, "sext");
-        return new SExtInst(NewTrunc, I.getType(), I.getName());
-      }
-    }
-  }
-
-  if (I.getType() == Type::getInt1Ty(I.getContext()))
-    return BinaryOperator::CreateXor(LHS, RHS);
-
-  if (I.getType()->isInteger()) {
-    // X + X --> X << 1
-    if (LHS == RHS)
-      return BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1));
-
-    if (Instruction *RHSI = dyn_cast<Instruction>(RHS)) {
-      if (RHSI->getOpcode() == Instruction::Sub)
-        if (LHS == RHSI->getOperand(1))                   // A + (B - A) --> B
-          return ReplaceInstUsesWith(I, RHSI->getOperand(0));
-    }
-    if (Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
-      if (LHSI->getOpcode() == Instruction::Sub)
-        if (RHS == LHSI->getOperand(1))                   // (B - A) + A --> B
-          return ReplaceInstUsesWith(I, LHSI->getOperand(0));
-    }
-  }
-
-  // -A + B  -->  B - A
-  // -A + -B  -->  -(A + B)
-  if (Value *LHSV = dyn_castNegVal(LHS)) {
-    if (LHS->getType()->isIntOrIntVector()) {
-      if (Value *RHSV = dyn_castNegVal(RHS)) {
-        Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
-        return BinaryOperator::CreateNeg(NewAdd);
-      }
-    }
-    
-    return BinaryOperator::CreateSub(RHS, LHSV);
-  }
-
-  // A + -B  -->  A - B
-  if (!isa<Constant>(RHS))
-    if (Value *V = dyn_castNegVal(RHS))
-      return BinaryOperator::CreateSub(LHS, V);
-
-
-  ConstantInt *C2;
-  if (Value *X = dyn_castFoldableMul(LHS, C2)) {
-    if (X == RHS)   // X*C + X --> X * (C+1)
-      return BinaryOperator::CreateMul(RHS, AddOne(C2));
-
-    // X*C1 + X*C2 --> X * (C1+C2)
-    ConstantInt *C1;
-    if (X == dyn_castFoldableMul(RHS, C1))
-      return BinaryOperator::CreateMul(X, ConstantExpr::getAdd(C1, C2));
-  }
-
-  // X + X*C --> X * (C+1)
-  if (dyn_castFoldableMul(RHS, C2) == LHS)
-    return BinaryOperator::CreateMul(LHS, AddOne(C2));
-
-  // X + ~X --> -1   since   ~X = -X-1
-  if (dyn_castNotVal(LHS) == RHS ||
-      dyn_castNotVal(RHS) == LHS)
-    return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
-  
-
-  // A+B --> A|B iff A and B have no bits set in common.
-  if (const IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
-    APInt Mask = APInt::getAllOnesValue(IT->getBitWidth());
-    APInt LHSKnownOne(IT->getBitWidth(), 0);
-    APInt LHSKnownZero(IT->getBitWidth(), 0);
-    ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne);
-    if (LHSKnownZero != 0) {
-      APInt RHSKnownOne(IT->getBitWidth(), 0);
-      APInt RHSKnownZero(IT->getBitWidth(), 0);
-      ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
-      
-      // No bits in common -> bitwise or.
-      if ((LHSKnownZero|RHSKnownZero).isAllOnesValue())
-        return BinaryOperator::CreateOr(LHS, RHS);
-    }
-  }
-
-  // W*X + Y*Z --> W * (X+Z)  iff W == Y
-  if (I.getType()->isIntOrIntVector()) {
-    Value *W, *X, *Y, *Z;
-    if (match(LHS, m_Mul(m_Value(W), m_Value(X))) &&
-        match(RHS, m_Mul(m_Value(Y), m_Value(Z)))) {
-      if (W != Y) {
-        if (W == Z) {
-          std::swap(Y, Z);
-        } else if (Y == X) {
-          std::swap(W, X);
-        } else if (X == Z) {
-          std::swap(Y, Z);
-          std::swap(W, X);
-        }
-      }
-
-      if (W == Y) {
-        Value *NewAdd = Builder->CreateAdd(X, Z, LHS->getName());
-        return BinaryOperator::CreateMul(W, NewAdd);
-      }
-    }
-  }
-
-  if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
-    Value *X = 0;
-    if (match(LHS, m_Not(m_Value(X))))    // ~X + C --> (C-1) - X
-      return BinaryOperator::CreateSub(SubOne(CRHS), X);
-
-    // (X & FF00) + xx00  -> (X+xx00) & FF00
-    if (LHS->hasOneUse() &&
-        match(LHS, m_And(m_Value(X), m_ConstantInt(C2)))) {
-      Constant *Anded = ConstantExpr::getAnd(CRHS, C2);
-      if (Anded == CRHS) {
-        // See if all bits from the first bit set in the Add RHS up are included
-        // in the mask.  First, get the rightmost bit.
-        const APInt &AddRHSV = CRHS->getValue();
-
-        // Form a mask of all bits from the lowest bit added through the top.
-        APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1));
-
-        // See if the and mask includes all of these bits.
-        APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue());
-
-        if (AddRHSHighBits == AddRHSHighBitsAnd) {
-          // Okay, the xform is safe.  Insert the new add pronto.
-          Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName());
-          return BinaryOperator::CreateAnd(NewAdd, C2);
-        }
-      }
-    }
-
-    // Try to fold constant add into select arguments.
-    if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
-      if (Instruction *R = FoldOpIntoSelect(I, SI))
-        return R;
-  }
-
-  // add (select X 0 (sub n A)) A  -->  select X A n
-  {
-    SelectInst *SI = dyn_cast<SelectInst>(LHS);
-    Value *A = RHS;
-    if (!SI) {
-      SI = dyn_cast<SelectInst>(RHS);
-      A = LHS;
-    }
-    if (SI && SI->hasOneUse()) {
-      Value *TV = SI->getTrueValue();
-      Value *FV = SI->getFalseValue();
-      Value *N;
-
-      // Can we fold the add into the argument of the select?
-      // We check both true and false select arguments for a matching subtract.
-      if (match(FV, m_Zero()) &&
-          match(TV, m_Sub(m_Value(N), m_Specific(A))))
-        // Fold the add into the true select value.
-        return SelectInst::Create(SI->getCondition(), N, A);
-      if (match(TV, m_Zero()) &&
-          match(FV, m_Sub(m_Value(N), m_Specific(A))))
-        // Fold the add into the false select value.
-        return SelectInst::Create(SI->getCondition(), A, N);
-    }
-  }
-
-  // Check for (add (sext x), y), see if we can merge this into an
-  // integer add followed by a sext.
-  if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) {
-    // (add (sext x), cst) --> (sext (add x, cst'))
-    if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
-      Constant *CI = 
-        ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
-      if (LHSConv->hasOneUse() &&
-          ConstantExpr::getSExt(CI, I.getType()) == RHSC &&
-          WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
-        // Insert the new, smaller add.
-        Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 
-                                              CI, "addconv");
-        return new SExtInst(NewAdd, I.getType());
-      }
-    }
-    
-    // (add (sext x), (sext y)) --> (sext (add int x, y))
-    if (SExtInst *RHSConv = dyn_cast<SExtInst>(RHS)) {
-      // Only do this if x/y have the same type, if at last one of them has a
-      // single use (so we don't increase the number of sexts), and if the
-      // integer add will not overflow.
-      if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
-          (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
-          WillNotOverflowSignedAdd(LHSConv->getOperand(0),
-                                   RHSConv->getOperand(0))) {
-        // Insert the new integer add.
-        Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 
-                                              RHSConv->getOperand(0), "addconv");
-        return new SExtInst(NewAdd, I.getType());
-      }
-    }
-  }
-
-  return Changed ? &I : 0;
-}
-
-Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
-  bool Changed = SimplifyCommutative(I);
-  Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
-
-  if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
-    // X + 0 --> X
-    if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
-      if (CFP->isExactlyValue(ConstantFP::getNegativeZero
-                              (I.getType())->getValueAPF()))
-        return ReplaceInstUsesWith(I, LHS);
-    }
-
-    if (isa<PHINode>(LHS))
-      if (Instruction *NV = FoldOpIntoPhi(I))
-        return NV;
-  }
-
-  // -A + B  -->  B - A
-  // -A + -B  -->  -(A + B)
-  if (Value *LHSV = dyn_castFNegVal(LHS))
-    return BinaryOperator::CreateFSub(RHS, LHSV);
-
-  // A + -B  -->  A - B
-  if (!isa<Constant>(RHS))
-    if (Value *V = dyn_castFNegVal(RHS))
-      return BinaryOperator::CreateFSub(LHS, V);
-
-  // Check for X+0.0.  Simplify it to X if we know X is not -0.0.
-  if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS))
-    if (CFP->getValueAPF().isPosZero() && CannotBeNegativeZero(LHS))
-      return ReplaceInstUsesWith(I, LHS);
-
-  // Check for (add double (sitofp x), y), see if we can merge this into an
-  // integer add followed by a promotion.
-  if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) {
-    // (add double (sitofp x), fpcst) --> (sitofp (add int x, intcst))
-    // ... if the constant fits in the integer value.  This is useful for things
-    // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer
-    // requires a constant pool load, and generally allows the add to be better
-    // instcombined.
-    if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS)) {
-      Constant *CI = 
-      ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType());
-      if (LHSConv->hasOneUse() &&
-          ConstantExpr::getSIToFP(CI, I.getType()) == CFP &&
-          WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
-        // Insert the new integer add.
-        Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
-                                              CI, "addconv");
-        return new SIToFPInst(NewAdd, I.getType());
-      }
-    }
-    
-    // (add double (sitofp x), (sitofp y)) --> (sitofp (add int x, y))
-    if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) {
-      // Only do this if x/y have the same type, if at last one of them has a
-      // single use (so we don't increase the number of int->fp conversions),
-      // and if the integer add will not overflow.
-      if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
-          (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
-          WillNotOverflowSignedAdd(LHSConv->getOperand(0),
-                                   RHSConv->getOperand(0))) {
-        // Insert the new integer add.
-        Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 
-                                              RHSConv->getOperand(0),"addconv");
-        return new SIToFPInst(NewAdd, I.getType());
-      }
-    }
-  }
-  
-  return Changed ? &I : 0;
-}
-
-
-/// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
-/// code necessary to compute the offset from the base pointer (without adding
-/// in the base pointer).  Return the result as a signed integer of intptr size.
-Value *InstCombiner::EmitGEPOffset(User *GEP) {
-  TargetData &TD = *getTargetData();
-  gep_type_iterator GTI = gep_type_begin(GEP);
-  const Type *IntPtrTy = TD.getIntPtrType(GEP->getContext());
-  Value *Result = Constant::getNullValue(IntPtrTy);
-
-  // Build a mask for high order bits.
-  unsigned IntPtrWidth = TD.getPointerSizeInBits();
-  uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
-
-  for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
-       ++i, ++GTI) {
-    Value *Op = *i;
-    uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
-    if (ConstantInt *OpC = dyn_cast<ConstantInt>(Op)) {
-      if (OpC->isZero()) continue;
-      
-      // Handle a struct index, which adds its field offset to the pointer.
-      if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
-        Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
-        
-        Result = Builder->CreateAdd(Result,
-                                    ConstantInt::get(IntPtrTy, Size),
-                                    GEP->getName()+".offs");
-        continue;
-      }
-      
-      Constant *Scale = ConstantInt::get(IntPtrTy, Size);
-      Constant *OC =
-              ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
-      Scale = ConstantExpr::getMul(OC, Scale);
-      // Emit an add instruction.
-      Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
-      continue;
-    }
-    // Convert to correct type.
-    if (Op->getType() != IntPtrTy)
-      Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
-    if (Size != 1) {
-      Constant *Scale = ConstantInt::get(IntPtrTy, Size);
-      // We'll let instcombine(mul) convert this to a shl if possible.
-      Op = Builder->CreateMul(Op, Scale, GEP->getName()+".idx");
-    }
-
-    // Emit an add instruction.
-    Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
-  }
-  return Result;
-}
-
-
-
-
-/// Optimize pointer differences into the same array into a size.  Consider:
-///  &A[10] - &A[0]: we should compile this to "10".  LHS/RHS are the pointer
-/// operands to the ptrtoint instructions for the LHS/RHS of the subtract.
-///
-Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS,
-                                               const Type *Ty) {
-  assert(TD && "Must have target data info for this");
-  
-  // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize
-  // this.
-  bool Swapped = false;
-  GetElementPtrInst *GEP = 0;
-  ConstantExpr *CstGEP = 0;
-  
-  // TODO: Could also optimize &A[i] - &A[j] -> "i-j", and "&A.foo[i] - &A.foo".
-  // For now we require one side to be the base pointer "A" or a constant
-  // expression derived from it.
-  if (GetElementPtrInst *LHSGEP = dyn_cast<GetElementPtrInst>(LHS)) {
-    // (gep X, ...) - X
-    if (LHSGEP->getOperand(0) == RHS) {
-      GEP = LHSGEP;
-      Swapped = false;
-    } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(RHS)) {
-      // (gep X, ...) - (ce_gep X, ...)
-      if (CE->getOpcode() == Instruction::GetElementPtr &&
-          LHSGEP->getOperand(0) == CE->getOperand(0)) {
-        CstGEP = CE;
-        GEP = LHSGEP;
-        Swapped = false;
-      }
-    }
-  }
-  
-  if (GetElementPtrInst *RHSGEP = dyn_cast<GetElementPtrInst>(RHS)) {
-    // X - (gep X, ...)
-    if (RHSGEP->getOperand(0) == LHS) {
-      GEP = RHSGEP;
-      Swapped = true;
-    } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(LHS)) {
-      // (ce_gep X, ...) - (gep X, ...)
-      if (CE->getOpcode() == Instruction::GetElementPtr &&
-          RHSGEP->getOperand(0) == CE->getOperand(0)) {
-        CstGEP = CE;
-        GEP = RHSGEP;
-        Swapped = true;
-      }
-    }
-  }
-  
-  if (GEP == 0)
-    return 0;
-  
-  // Emit the offset of the GEP and an intptr_t.
-  Value *Result = EmitGEPOffset(GEP);
-  
-  // If we had a constant expression GEP on the other side offsetting the
-  // pointer, subtract it from the offset we have.
-  if (CstGEP) {
-    Value *CstOffset = EmitGEPOffset(CstGEP);
-    Result = Builder->CreateSub(Result, CstOffset);
-  }
-  
-
-  // If we have p - gep(p, ...)  then we have to negate the result.
-  if (Swapped)
-    Result = Builder->CreateNeg(Result, "diff.neg");
-
-  return Builder->CreateIntCast(Result, Ty, true);
-}
-
-
-Instruction *InstCombiner::visitSub(BinaryOperator &I) {
-  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
-
-  if (Op0 == Op1)                        // sub X, X  -> 0
-    return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
-
-  // If this is a 'B = x-(-A)', change to B = x+A.  This preserves NSW/NUW.
-  if (Value *V = dyn_castNegVal(Op1)) {
-    BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);
-    Res->setHasNoSignedWrap(I.hasNoSignedWrap());
-    Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
-    return Res;
-  }
-
-  if (isa<UndefValue>(Op0))
-    return ReplaceInstUsesWith(I, Op0);    // undef - X -> undef
-  if (isa<UndefValue>(Op1))
-    return ReplaceInstUsesWith(I, Op1);    // X - undef -> undef
-  if (I.getType() == Type::getInt1Ty(I.getContext()))
-    return BinaryOperator::CreateXor(Op0, Op1);
-  
-  if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
-    // Replace (-1 - A) with (~A).
-    if (C->isAllOnesValue())
-      return BinaryOperator::CreateNot(Op1);
-
-    // C - ~X == X + (1+C)
-    Value *X = 0;
-    if (match(Op1, m_Not(m_Value(X))))
-      return BinaryOperator::CreateAdd(X, AddOne(C));
-
-    // -(X >>u 31) -> (X >>s 31)
-    // -(X >>s 31) -> (X >>u 31)
-    if (C->isZero()) {
-      if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op1)) {
-        if (SI->getOpcode() == Instruction::LShr) {
-          if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
-            // Check to see if we are shifting out everything but the sign bit.
-            if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
-                SI->getType()->getPrimitiveSizeInBits()-1) {
-              // Ok, the transformation is safe.  Insert AShr.
-              return BinaryOperator::Create(Instruction::AShr, 
-                                          SI->getOperand(0), CU, SI->getName());
-            }
-          }
-        } else if (SI->getOpcode() == Instruction::AShr) {
-          if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
-            // Check to see if we are shifting out everything but the sign bit.
-            if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
-                SI->getType()->getPrimitiveSizeInBits()-1) {
-              // Ok, the transformation is safe.  Insert LShr. 
-              return BinaryOperator::CreateLShr(
-                                          SI->getOperand(0), CU, SI->getName());
-            }
-          }
-        }
-      }
-    }
-
-    // Try to fold constant sub into select arguments.
-    if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
-      if (Instruction *R = FoldOpIntoSelect(I, SI))
-        return R;
-
-    // C - zext(bool) -> bool ? C - 1 : C
-    if (ZExtInst *ZI = dyn_cast<ZExtInst>(Op1))
-      if (ZI->getSrcTy() == Type::getInt1Ty(I.getContext()))
-        return SelectInst::Create(ZI->getOperand(0), SubOne(C), C);
-  }
-
-  if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
-    if (Op1I->getOpcode() == Instruction::Add) {
-      if (Op1I->getOperand(0) == Op0)              // X-(X+Y) == -Y
-        return BinaryOperator::CreateNeg(Op1I->getOperand(1),
-                                         I.getName());
-      else if (Op1I->getOperand(1) == Op0)         // X-(Y+X) == -Y
-        return BinaryOperator::CreateNeg(Op1I->getOperand(0),
-                                         I.getName());
-      else if (ConstantInt *CI1 = dyn_cast<ConstantInt>(I.getOperand(0))) {
-        if (ConstantInt *CI2 = dyn_cast<ConstantInt>(Op1I->getOperand(1)))
-          // C1-(X+C2) --> (C1-C2)-X
-          return BinaryOperator::CreateSub(
-            ConstantExpr::getSub(CI1, CI2), Op1I->getOperand(0));
-      }
-    }
-
-    if (Op1I->hasOneUse()) {
-      // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
-      // is not used by anyone else...
-      //
-      if (Op1I->getOpcode() == Instruction::Sub) {
-        // Swap the two operands of the subexpr...
-        Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
-        Op1I->setOperand(0, IIOp1);
-        Op1I->setOperand(1, IIOp0);
-
-        // Create the new top level add instruction...
-        return BinaryOperator::CreateAdd(Op0, Op1);
-      }
-
-      // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
-      //
-      if (Op1I->getOpcode() == Instruction::And &&
-          (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
-        Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
-
-        Value *NewNot = Builder->CreateNot(OtherOp, "B.not");
-        return BinaryOperator::CreateAnd(Op0, NewNot);
-      }
-
-      // 0 - (X sdiv C)  -> (X sdiv -C)
-      if (Op1I->getOpcode() == Instruction::SDiv)
-        if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
-          if (CSI->isZero())
-            if (Constant *DivRHS = dyn_cast<Constant>(Op1I->getOperand(1)))
-              return BinaryOperator::CreateSDiv(Op1I->getOperand(0),
-                                          ConstantExpr::getNeg(DivRHS));
-
-      // X - X*C --> X * (1-C)
-      ConstantInt *C2 = 0;
-      if (dyn_castFoldableMul(Op1I, C2) == Op0) {
-        Constant *CP1 = 
-          ConstantExpr::getSub(ConstantInt::get(I.getType(), 1),
-                                             C2);
-        return BinaryOperator::CreateMul(Op0, CP1);
-      }
-    }
-  }
-
-  if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
-    if (Op0I->getOpcode() == Instruction::Add) {
-      if (Op0I->getOperand(0) == Op1)             // (Y+X)-Y == X
-        return ReplaceInstUsesWith(I, Op0I->getOperand(1));
-      else if (Op0I->getOperand(1) == Op1)        // (X+Y)-Y == X
-        return ReplaceInstUsesWith(I, Op0I->getOperand(0));
-    } else if (Op0I->getOpcode() == Instruction::Sub) {
-      if (Op0I->getOperand(0) == Op1)             // (X-Y)-X == -Y
-        return BinaryOperator::CreateNeg(Op0I->getOperand(1),
-                                         I.getName());
-    }
-  }
-
-  ConstantInt *C1;
-  if (Value *X = dyn_castFoldableMul(Op0, C1)) {
-    if (X == Op1)  // X*C - X --> X * (C-1)
-      return BinaryOperator::CreateMul(Op1, SubOne(C1));
-
-    ConstantInt *C2;   // X*C1 - X*C2 -> X * (C1-C2)
-    if (X == dyn_castFoldableMul(Op1, C2))
-      return BinaryOperator::CreateMul(X, ConstantExpr::getSub(C1, C2));
-  }
-  
-  // Optimize pointer differences into the same array into a size.  Consider:
-  //  &A[10] - &A[0]: we should compile this to "10".
-  if (TD) {
-    Value *LHSOp, *RHSOp;
-    if (match(Op0, m_PtrToInt(m_Value(LHSOp))) &&
-        match(Op1, m_PtrToInt(m_Value(RHSOp))))
-      if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
-        return ReplaceInstUsesWith(I, Res);
-    
-    // trunc(p)-trunc(q) -> trunc(p-q)
-    if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) &&
-        match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp)))))
-      if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
-        return ReplaceInstUsesWith(I, Res);
-  }
-  
-  return 0;
-}
-
-Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
-  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
-
-  // If this is a 'B = x-(-A)', change to B = x+A...
-  if (Value *V = dyn_castFNegVal(Op1))
-    return BinaryOperator::CreateFAdd(Op0, V);
-
-  if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
-    if (Op1I->getOpcode() == Instruction::FAdd) {
-      if (Op1I->getOperand(0) == Op0)              // X-(X+Y) == -Y
-        return BinaryOperator::CreateFNeg(Op1I->getOperand(1),
-                                          I.getName());
-      else if (Op1I->getOperand(1) == Op0)         // X-(Y+X) == -Y
-        return BinaryOperator::CreateFNeg(Op1I->getOperand(0),
-                                          I.getName());
-    }
-  }
-
-  return 0;
-}
-
 /// getICmpCode - Encode a icmp predicate into a three bit mask.  These bits
 /// are carefully arranged to allow folding of expressions such as:
 ///