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llvm-mirror/lib/Transforms/InstCombine/InstCombineAddSub.cpp
Chad Rosier f3d4646377 Add instcombine patterns for the following transformations: 
(x & y) | (x ^ y) -> x | y 
 (x & y) + (x ^ y) -> x | y 

Patch by Manman Ren.
rdar://10770603

llvm-svn: 155674
2012-04-26 23:29:14 +00:00

726 lines
26 KiB
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//===- InstCombineAddSub.cpp ----------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the visit functions for add, fadd, sub, and fsub.
//
//===----------------------------------------------------------------------===//
#include "InstCombine.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/PatternMatch.h"
using namespace llvm;
using namespace PatternMatch;
/// AddOne - Add one to a ConstantInt.
static Constant *AddOne(Constant *C) {
return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
}
/// SubOne - Subtract one from a ConstantInt.
static Constant *SubOne(ConstantInt *C) {
return ConstantInt::get(C->getContext(), C->getValue()-1);
}
// dyn_castFoldableMul - If this value is a multiply that can be folded into
// other computations (because it has a constant operand), return the
// non-constant operand of the multiply, and set CST to point to the multiplier.
// Otherwise, return null.
//
static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) {
if (!V->hasOneUse() || !V->getType()->isIntegerTy())
return 0;
Instruction *I = dyn_cast<Instruction>(V);
if (I == 0) return 0;
if (I->getOpcode() == Instruction::Mul)
if ((CST = dyn_cast<ConstantInt>(I->getOperand(1))))
return I->getOperand(0);
if (I->getOpcode() == Instruction::Shl)
if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) {
// The multiplier is really 1 << CST.
uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
uint32_t CSTVal = CST->getLimitedValue(BitWidth);
CST = ConstantInt::get(V->getType()->getContext(),
APInt(BitWidth, 1).shl(CSTVal));
return I->getOperand(0);
}
return 0;
}
/// 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 = SimplifyAssociativeOrCommutative(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);
// (A*B)+(A*C) -> A*(B+C) etc
if (Value *V = SimplifyUsingDistributiveLaws(I))
return ReplaceInstUsesWith(I, V);
if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
// X + (signbit) --> X ^ signbit
const APInt &Val = CI->getValue();
if (Val.isSignBit())
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()->isIntegerTy(1))
return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI);
Value *XorLHS = 0; ConstantInt *XorRHS = 0;
if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
uint32_t TySizeBits = I.getType()->getScalarSizeInBits();
const APInt &RHSVal = CI->getValue();
unsigned ExtendAmt = 0;
// 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 (XorRHS->getValue() == -RHSVal) {
if (RHSVal.isPowerOf2())
ExtendAmt = TySizeBits - RHSVal.logBase2() - 1;
else if (XorRHS->getValue().isPowerOf2())
ExtendAmt = TySizeBits - XorRHS->getValue().logBase2() - 1;
}
if (ExtendAmt) {
APInt Mask = APInt::getHighBitsSet(TySizeBits, ExtendAmt);
if (!MaskedValueIsZero(XorLHS, Mask))
ExtendAmt = 0;
}
if (ExtendAmt) {
Constant *ShAmt = ConstantInt::get(I.getType(), ExtendAmt);
Value *NewShl = Builder->CreateShl(XorLHS, ShAmt, "sext");
return BinaryOperator::CreateAShr(NewShl, ShAmt);
}
// If this is a xor that was canonicalized from a sub, turn it back into
// a sub and fuse this add with it.
if (LHS->hasOneUse() && (XorRHS->getValue()+1).isPowerOf2()) {
IntegerType *IT = cast<IntegerType>(I.getType());
APInt LHSKnownOne(IT->getBitWidth(), 0);
APInt LHSKnownZero(IT->getBitWidth(), 0);
ComputeMaskedBits(XorLHS, LHSKnownZero, LHSKnownOne);
if ((XorRHS->getValue() | LHSKnownZero).isAllOnesValue())
return BinaryOperator::CreateSub(ConstantExpr::getAdd(XorRHS, CI),
XorLHS);
}
}
}
if (isa<Constant>(RHS) && isa<PHINode>(LHS))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
if (I.getType()->isIntegerTy(1))
return BinaryOperator::CreateXor(LHS, RHS);
// X + X --> X << 1
if (LHS == RHS) {
BinaryOperator *New =
BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1));
New->setHasNoSignedWrap(I.hasNoSignedWrap());
New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
return New;
}
// -A + B --> B - A
// -A + -B --> -(A + B)
if (Value *LHSV = dyn_castNegVal(LHS)) {
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));
// A+B --> A|B iff A and B have no bits set in common.
if (IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
APInt LHSKnownOne(IT->getBitWidth(), 0);
APInt LHSKnownZero(IT->getBitWidth(), 0);
ComputeMaskedBits(LHS, LHSKnownZero, LHSKnownOne);
if (LHSKnownZero != 0) {
APInt RHSKnownOne(IT->getBitWidth(), 0);
APInt RHSKnownZero(IT->getBitWidth(), 0);
ComputeMaskedBits(RHS, 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
{
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))) &&
CRHS->getValue() == (CRHS->getValue() & C2->getValue())) {
// 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());
}
}
}
// Check for (x & y) + (x ^ y)
{
Value *A = 0, *B = 0;
if (match(RHS, m_Xor(m_Value(A), m_Value(B))) &&
(match(LHS, m_And(m_Specific(A), m_Specific(B))) ||
match(LHS, m_And(m_Specific(B), m_Specific(A)))))
return BinaryOperator::CreateOr(A, B);
if (match(LHS, m_Xor(m_Value(A), m_Value(B))) &&
(match(RHS, m_And(m_Specific(A), m_Specific(B))) ||
match(RHS, m_And(m_Specific(B), m_Specific(A)))))
return BinaryOperator::CreateOr(A, B);
}
return Changed ? &I : 0;
}
Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
bool Changed = SimplifyAssociativeOrCommutative(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 (fadd 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)) {
// (fadd 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());
}
}
// (fadd 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);
Type *IntPtrTy = TD.getIntPtrType(GEP->getContext());
Value *Result = Constant::getNullValue(IntPtrTy);
// If the GEP is inbounds, we know that none of the addressing operations will
// overflow in an unsigned sense.
bool isInBounds = cast<GEPOperator>(GEP)->isInBounds();
// 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 (StructType *STy = dyn_cast<StructType>(*GTI)) {
Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
if (Size)
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, isInBounds/*NUW*/);
// 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) {
// We'll let instcombine(mul) convert this to a shl if possible.
Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
GEP->getName()+".idx", isInBounds /*NUW*/);
}
// 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,
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;
GEPOperator *GEP1 = 0, *GEP2 = 0;
// For now we require one side to be the base pointer "A" or a constant
// GEP derived from it.
if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) {
// (gep X, ...) - X
if (LHSGEP->getOperand(0) == RHS) {
GEP1 = LHSGEP;
Swapped = false;
} else if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) {
// (gep X, ...) - (gep X, ...)
if (LHSGEP->getOperand(0)->stripPointerCasts() ==
RHSGEP->getOperand(0)->stripPointerCasts()) {
GEP2 = RHSGEP;
GEP1 = LHSGEP;
Swapped = false;
}
}
}
if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) {
// X - (gep X, ...)
if (RHSGEP->getOperand(0) == LHS) {
GEP1 = RHSGEP;
Swapped = true;
} else if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) {
// (gep X, ...) - (gep X, ...)
if (RHSGEP->getOperand(0)->stripPointerCasts() ==
LHSGEP->getOperand(0)->stripPointerCasts()) {
GEP2 = LHSGEP;
GEP1 = RHSGEP;
Swapped = true;
}
}
}
// Avoid duplicating the arithmetic if GEP2 has non-constant indices and
// multiple users.
if (GEP1 == 0 ||
(GEP2 != 0 && !GEP2->hasAllConstantIndices() && !GEP2->hasOneUse()))
return 0;
// Emit the offset of the GEP and an intptr_t.
Value *Result = EmitGEPOffset(GEP1);
// If we had a constant expression GEP on the other side offsetting the
// pointer, subtract it from the offset we have.
if (GEP2) {
Value *Offset = EmitGEPOffset(GEP2);
Result = Builder->CreateSub(Result, Offset);
}
// 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 (Value *V = SimplifySubInst(Op0, Op1, I.hasNoSignedWrap(),
I.hasNoUnsignedWrap(), TD))
return ReplaceInstUsesWith(I, V);
// (A*B)-(A*C) -> A*(B-C) etc
if (Value *V = SimplifyUsingDistributiveLaws(I))
return ReplaceInstUsesWith(I, V);
// 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 (I.getType()->isIntegerTy(1))
return BinaryOperator::CreateXor(Op0, Op1);
// Replace (-1 - A) with (~A).
if (match(Op0, m_AllOnes()))
return BinaryOperator::CreateNot(Op1);
if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
// 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()) {
Value *X; ConstantInt *CI;
if (match(Op1, m_LShr(m_Value(X), m_ConstantInt(CI))) &&
// Verify we are shifting out everything but the sign bit.
CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1)
return BinaryOperator::CreateAShr(X, CI);
if (match(Op1, m_AShr(m_Value(X), m_ConstantInt(CI))) &&
// Verify we are shifting out everything but the sign bit.
CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1)
return BinaryOperator::CreateLShr(X, CI);
}
// 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()->isIntegerTy(1))
return SelectInst::Create(ZI->getOperand(0), SubOne(C), C);
// C-(X+C2) --> (C-C2)-X
ConstantInt *C2;
if (match(Op1, m_Add(m_Value(X), m_ConstantInt(C2))))
return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X);
if (SimplifyDemandedInstructionBits(I))
return &I;
}
{ Value *Y;
// X-(X+Y) == -Y X-(Y+X) == -Y
if (match(Op1, m_Add(m_Specific(Op0), m_Value(Y))) ||
match(Op1, m_Add(m_Value(Y), m_Specific(Op0))))
return BinaryOperator::CreateNeg(Y);
// (X-Y)-X == -Y
if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y))))
return BinaryOperator::CreateNeg(Y);
}
if (Op1->hasOneUse()) {
Value *X = 0, *Y = 0, *Z = 0;
Constant *C = 0;
ConstantInt *CI = 0;
// (X - (Y - Z)) --> (X + (Z - Y)).
if (match(Op1, m_Sub(m_Value(Y), m_Value(Z))))
return BinaryOperator::CreateAdd(Op0,
Builder->CreateSub(Z, Y, Op1->getName()));
// (X - (X & Y)) --> (X & ~Y)
//
if (match(Op1, m_And(m_Value(Y), m_Specific(Op0))) ||
match(Op1, m_And(m_Specific(Op0), m_Value(Y))))
return BinaryOperator::CreateAnd(Op0,
Builder->CreateNot(Y, Y->getName() + ".not"));
// 0 - (X sdiv C) -> (X sdiv -C)
if (match(Op1, m_SDiv(m_Value(X), m_Constant(C))) &&
match(Op0, m_Zero()))
return BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C));
// 0 - (X << Y) -> (-X << Y) when X is freely negatable.
if (match(Op1, m_Shl(m_Value(X), m_Value(Y))) && match(Op0, m_Zero()))
if (Value *XNeg = dyn_castNegVal(X))
return BinaryOperator::CreateShl(XNeg, Y);
// X - X*C --> X * (1-C)
if (match(Op1, m_Mul(m_Specific(Op0), m_ConstantInt(CI)))) {
Constant *CP1 = ConstantExpr::getSub(ConstantInt::get(I.getType(),1), CI);
return BinaryOperator::CreateMul(Op0, CP1);
}
// X - X<<C --> X * (1-(1<<C))
if (match(Op1, m_Shl(m_Specific(Op0), m_ConstantInt(CI)))) {
Constant *One = ConstantInt::get(I.getType(), 1);
C = ConstantExpr::getSub(One, ConstantExpr::getShl(One, CI));
return BinaryOperator::CreateMul(Op0, C);
}
// X - A*-B -> X + A*B
// X - -A*B -> X + A*B
Value *A, *B;
if (match(Op1, m_Mul(m_Value(A), m_Neg(m_Value(B)))) ||
match(Op1, m_Mul(m_Neg(m_Value(A)), m_Value(B))))
return BinaryOperator::CreateAdd(Op0, Builder->CreateMul(A, B));
// X - A*CI -> X + A*-CI
// X - CI*A -> X + A*-CI
if (match(Op1, m_Mul(m_Value(A), m_ConstantInt(CI))) ||
match(Op1, m_Mul(m_ConstantInt(CI), m_Value(A)))) {
Value *NewMul = Builder->CreateMul(A, ConstantExpr::getNeg(CI));
return BinaryOperator::CreateAdd(Op0, NewMul);
}
}
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);
return 0;
}
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