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swiftshader / SwiftShader / 708ca9579181a8096193f68ad6c412a5fd302d5b / . / third_party / llvm-10.0 / llvm / lib / Transforms / InstCombine / InstCombineAddSub.cpp
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//===- InstCombineAddSub.cpp ------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the visit functions for add, fadd, sub, and fsub.
//
//===----------------------------------------------------------------------===//
#include "InstCombineInternal.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/AlignOf.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/KnownBits.h"
#include <cassert>
#include <utility>
using namespace llvm;
using namespace PatternMatch;
#define DEBUG_TYPE "instcombine"
namespace {
/// Class representing coefficient of floating-point addend.
/// This class needs to be highly efficient, which is especially true for
/// the constructor. As of I write this comment, the cost of the default
/// constructor is merely 4-byte-store-zero (Assuming compiler is able to
/// perform write-merging).
///
class FAddendCoef {
public:
// The constructor has to initialize a APFloat, which is unnecessary for
// most addends which have coefficient either 1 or -1. So, the constructor
// is expensive. In order to avoid the cost of the constructor, we should
// reuse some instances whenever possible. The pre-created instances
// FAddCombine::Add[0-5] embodies this idea.
FAddendCoef() = default;
~FAddendCoef();
// If possible, don't define operator+/operator- etc because these
// operators inevitably call FAddendCoef's constructor which is not cheap.
void operator=(const FAddendCoef &A);
void operator+=(const FAddendCoef &A);
void operator*=(const FAddendCoef &S);
void set(short C) {
assert(!insaneIntVal(C) && "Insane coefficient");
IsFp = false; IntVal = C;
}
void set(const APFloat& C);
void negate();
bool isZero() const { return isInt() ? !IntVal : getFpVal().isZero(); }
Value *getValue(Type *) const;
bool isOne() const { return isInt() && IntVal == 1; }
bool isTwo() const { return isInt() && IntVal == 2; }
bool isMinusOne() const { return isInt() && IntVal == -1; }
bool isMinusTwo() const { return isInt() && IntVal == -2; }
private:
bool insaneIntVal(int V) { return V > 4 || V < -4; }
APFloat *getFpValPtr()
{ return reinterpret_cast<APFloat *>(&FpValBuf.buffer[0]); }
const APFloat *getFpValPtr() const
{ return reinterpret_cast<const APFloat *>(&FpValBuf.buffer[0]); }
const APFloat &getFpVal() const {
assert(IsFp && BufHasFpVal && "Incorret state");
return *getFpValPtr();
}
APFloat &getFpVal() {
assert(IsFp && BufHasFpVal && "Incorret state");
return *getFpValPtr();
}
bool isInt() const { return !IsFp; }
// If the coefficient is represented by an integer, promote it to a
// floating point.
void convertToFpType(const fltSemantics &Sem);
// Construct an APFloat from a signed integer.
// TODO: We should get rid of this function when APFloat can be constructed
// from an *SIGNED* integer.
APFloat createAPFloatFromInt(const fltSemantics &Sem, int Val);
bool IsFp = false;
// True iff FpValBuf contains an instance of APFloat.
bool BufHasFpVal = false;
// The integer coefficient of an individual addend is either 1 or -1,
// and we try to simplify at most 4 addends from neighboring at most
// two instructions. So the range of <IntVal> falls in [-4, 4]. APInt
// is overkill of this end.
short IntVal = 0;
AlignedCharArrayUnion<APFloat> FpValBuf;
};
/// FAddend is used to represent floating-point addend. An addend is
/// represented as <C, V>, where the V is a symbolic value, and C is a
/// constant coefficient. A constant addend is represented as <C, 0>.
class FAddend {
public:
FAddend() = default;
void operator+=(const FAddend &T) {
assert((Val == T.Val) && "Symbolic-values disagree");
Coeff += T.Coeff;
}
Value *getSymVal() const { return Val; }
const FAddendCoef &getCoef() const { return Coeff; }
bool isConstant() const { return Val == nullptr; }
bool isZero() const { return Coeff.isZero(); }
void set(short Coefficient, Value *V) {
Coeff.set(Coefficient);
Val = V;
}
void set(const APFloat &Coefficient, Value *V) {
Coeff.set(Coefficient);
Val = V;
}
void set(const ConstantFP *Coefficient, Value *V) {
Coeff.set(Coefficient->getValueAPF());
Val = V;
}
void negate() { Coeff.negate(); }
/// Drill down the U-D chain one step to find the definition of V, and
/// try to break the definition into one or two addends.
static unsigned drillValueDownOneStep(Value* V, FAddend &A0, FAddend &A1);
/// Similar to FAddend::drillDownOneStep() except that the value being
/// splitted is the addend itself.
unsigned drillAddendDownOneStep(FAddend &Addend0, FAddend &Addend1) const;
private:
void Scale(const FAddendCoef& ScaleAmt) { Coeff *= ScaleAmt; }
// This addend has the value of "Coeff * Val".
Value *Val = nullptr;
FAddendCoef Coeff;
};
/// FAddCombine is the class for optimizing an unsafe fadd/fsub along
/// with its neighboring at most two instructions.
///
class FAddCombine {
public:
FAddCombine(InstCombiner::BuilderTy &B) : Builder(B) {}
Value *simplify(Instruction *FAdd);
private:
using AddendVect = SmallVector<const FAddend *, 4>;
Value *simplifyFAdd(AddendVect& V, unsigned InstrQuota);
/// Convert given addend to a Value
Value *createAddendVal(const FAddend &A, bool& NeedNeg);
/// Return the number of instructions needed to emit the N-ary addition.
unsigned calcInstrNumber(const AddendVect& Vect);
Value *createFSub(Value *Opnd0, Value *Opnd1);
Value *createFAdd(Value *Opnd0, Value *Opnd1);
Value *createFMul(Value *Opnd0, Value *Opnd1);
Value *createFNeg(Value *V);
Value *createNaryFAdd(const AddendVect& Opnds, unsigned InstrQuota);
void createInstPostProc(Instruction *NewInst, bool NoNumber = false);
// Debugging stuff are clustered here.
#ifndef NDEBUG
unsigned CreateInstrNum;
void initCreateInstNum() { CreateInstrNum = 0; }
void incCreateInstNum() { CreateInstrNum++; }
#else
void initCreateInstNum() {}
void incCreateInstNum() {}
#endif
InstCombiner::BuilderTy &Builder;
Instruction *Instr = nullptr;
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
//
// Implementation of
// {FAddendCoef, FAddend, FAddition, FAddCombine}.
//
//===----------------------------------------------------------------------===//
FAddendCoef::~FAddendCoef() {
if (BufHasFpVal)
getFpValPtr()->~APFloat();
}
void FAddendCoef::set(const APFloat& C) {
APFloat *P = getFpValPtr();
if (isInt()) {
// As the buffer is meanless byte stream, we cannot call
// APFloat::operator=().
new(P) APFloat(C);
} else
*P = C;
IsFp = BufHasFpVal = true;
}
void FAddendCoef::convertToFpType(const fltSemantics &Sem) {
if (!isInt())
return;
APFloat *P = getFpValPtr();
if (IntVal > 0)
new(P) APFloat(Sem, IntVal);
else {
new(P) APFloat(Sem, 0 - IntVal);
P->changeSign();
}
IsFp = BufHasFpVal = true;
}
APFloat FAddendCoef::createAPFloatFromInt(const fltSemantics &Sem, int Val) {
if (Val >= 0)
return APFloat(Sem, Val);
APFloat T(Sem, 0 - Val);
T.changeSign();
return T;
}
void FAddendCoef::operator=(const FAddendCoef &That) {
if (That.isInt())
set(That.IntVal);
else
set(That.getFpVal());
}
void FAddendCoef::operator+=(const FAddendCoef &That) {
enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven;
if (isInt() == That.isInt()) {
if (isInt())
IntVal += That.IntVal;
else
getFpVal().add(That.getFpVal(), RndMode);
return;
}
if (isInt()) {
const APFloat &T = That.getFpVal();
convertToFpType(T.getSemantics());
getFpVal().add(T, RndMode);
return;
}
APFloat &T = getFpVal();
T.add(createAPFloatFromInt(T.getSemantics(), That.IntVal), RndMode);
}
void FAddendCoef::operator*=(const FAddendCoef &That) {
if (That.isOne())
return;
if (That.isMinusOne()) {
negate();
return;
}
if (isInt() && That.isInt()) {
int Res = IntVal * (int)That.IntVal;
assert(!insaneIntVal(Res) && "Insane int value");
IntVal = Res;
return;
}
const fltSemantics &Semantic =
isInt() ? That.getFpVal().getSemantics() : getFpVal().getSemantics();
if (isInt())
convertToFpType(Semantic);
APFloat &F0 = getFpVal();
if (That.isInt())
F0.multiply(createAPFloatFromInt(Semantic, That.IntVal),
APFloat::rmNearestTiesToEven);
else
F0.multiply(That.getFpVal(), APFloat::rmNearestTiesToEven);
}
void FAddendCoef::negate() {
if (isInt())
IntVal = 0 - IntVal;
else
getFpVal().changeSign();
}
Value *FAddendCoef::getValue(Type *Ty) const {
return isInt() ?
ConstantFP::get(Ty, float(IntVal)) :
ConstantFP::get(Ty->getContext(), getFpVal());
}
// The definition of <Val> Addends
// =========================================
// A + B <1, A>, <1,B>
// A - B <1, A>, <1,B>
// 0 - B <-1, B>
// C * A, <C, A>
// A + C <1, A> <C, NULL>
// 0 +/- 0 <0, NULL> (corner case)
//
// Legend: A and B are not constant, C is constant
unsigned FAddend::drillValueDownOneStep
(Value *Val, FAddend &Addend0, FAddend &Addend1) {
Instruction *I = nullptr;
if (!Val || !(I = dyn_cast<Instruction>(Val)))
return 0;
unsigned Opcode = I->getOpcode();
if (Opcode == Instruction::FAdd || Opcode == Instruction::FSub) {
ConstantFP *C0, *C1;
Value *Opnd0 = I->getOperand(0);
Value *Opnd1 = I->getOperand(1);
if ((C0 = dyn_cast<ConstantFP>(Opnd0)) && C0->isZero())
Opnd0 = nullptr;
if ((C1 = dyn_cast<ConstantFP>(Opnd1)) && C1->isZero())
Opnd1 = nullptr;
if (Opnd0) {
if (!C0)
Addend0.set(1, Opnd0);
else
Addend0.set(C0, nullptr);
}
if (Opnd1) {
FAddend &Addend = Opnd0 ? Addend1 : Addend0;
if (!C1)
Addend.set(1, Opnd1);
else
Addend.set(C1, nullptr);
if (Opcode == Instruction::FSub)
Addend.negate();
}
if (Opnd0 || Opnd1)
return Opnd0 && Opnd1 ? 2 : 1;
// Both operands are zero. Weird!
Addend0.set(APFloat(C0->getValueAPF().getSemantics()), nullptr);
return 1;
}
if (I->getOpcode() == Instruction::FMul) {
Value *V0 = I->getOperand(0);
Value *V1 = I->getOperand(1);
if (ConstantFP *C = dyn_cast<ConstantFP>(V0)) {
Addend0.set(C, V1);
return 1;
}
if (ConstantFP *C = dyn_cast<ConstantFP>(V1)) {
Addend0.set(C, V0);
return 1;
}
}
return 0;
}
// Try to break *this* addend into two addends. e.g. Suppose this addend is
// <2.3, V>, and V = X + Y, by calling this function, we obtain two addends,
// i.e. <2.3, X> and <2.3, Y>.
unsigned FAddend::drillAddendDownOneStep
(FAddend &Addend0, FAddend &Addend1) const {
if (isConstant())
return 0;
unsigned BreakNum = FAddend::drillValueDownOneStep(Val, Addend0, Addend1);
if (!BreakNum || Coeff.isOne())
return BreakNum;
Addend0.Scale(Coeff);
if (BreakNum == 2)
Addend1.Scale(Coeff);
return BreakNum;
}
Value *FAddCombine::simplify(Instruction *I) {
assert(I->hasAllowReassoc() && I->hasNoSignedZeros() &&
"Expected 'reassoc'+'nsz' instruction");
// Currently we are not able to handle vector type.
if (I->getType()->isVectorTy())
return nullptr;
assert((I->getOpcode() == Instruction::FAdd ||
I->getOpcode() == Instruction::FSub) && "Expect add/sub");
// Save the instruction before calling other member-functions.
Instr = I;
FAddend Opnd0, Opnd1, Opnd0_0, Opnd0_1, Opnd1_0, Opnd1_1;
unsigned OpndNum = FAddend::drillValueDownOneStep(I, Opnd0, Opnd1);
// Step 1: Expand the 1st addend into Opnd0_0 and Opnd0_1.
unsigned Opnd0_ExpNum = 0;
unsigned Opnd1_ExpNum = 0;
if (!Opnd0.isConstant())
Opnd0_ExpNum = Opnd0.drillAddendDownOneStep(Opnd0_0, Opnd0_1);
// Step 2: Expand the 2nd addend into Opnd1_0 and Opnd1_1.
if (OpndNum == 2 && !Opnd1.isConstant())
Opnd1_ExpNum = Opnd1.drillAddendDownOneStep(Opnd1_0, Opnd1_1);
// Step 3: Try to optimize Opnd0_0 + Opnd0_1 + Opnd1_0 + Opnd1_1
if (Opnd0_ExpNum && Opnd1_ExpNum) {
AddendVect AllOpnds;
AllOpnds.push_back(&Opnd0_0);
AllOpnds.push_back(&Opnd1_0);
if (Opnd0_ExpNum == 2)
AllOpnds.push_back(&Opnd0_1);
if (Opnd1_ExpNum == 2)
AllOpnds.push_back(&Opnd1_1);
// Compute instruction quota. We should save at least one instruction.
unsigned InstQuota = 0;
Value *V0 = I->getOperand(0);
Value *V1 = I->getOperand(1);
InstQuota = ((!isa<Constant>(V0) && V0->hasOneUse()) &&
(!isa<Constant>(V1) && V1->hasOneUse())) ? 2 : 1;
if (Value *R = simplifyFAdd(AllOpnds, InstQuota))
return R;
}
if (OpndNum != 2) {
// The input instruction is : "I=0.0 +/- V". If the "V" were able to be
// splitted into two addends, say "V = X - Y", the instruction would have
// been optimized into "I = Y - X" in the previous steps.
//
const FAddendCoef &CE = Opnd0.getCoef();
return CE.isOne() ? Opnd0.getSymVal() : nullptr;
}
// step 4: Try to optimize Opnd0 + Opnd1_0 [+ Opnd1_1]
if (Opnd1_ExpNum) {
AddendVect AllOpnds;
AllOpnds.push_back(&Opnd0);
AllOpnds.push_back(&Opnd1_0);
if (Opnd1_ExpNum == 2)
AllOpnds.push_back(&Opnd1_1);
if (Value *R = simplifyFAdd(AllOpnds, 1))
return R;
}
// step 5: Try to optimize Opnd1 + Opnd0_0 [+ Opnd0_1]
if (Opnd0_ExpNum) {
AddendVect AllOpnds;
AllOpnds.push_back(&Opnd1);
AllOpnds.push_back(&Opnd0_0);
if (Opnd0_ExpNum == 2)
AllOpnds.push_back(&Opnd0_1);
if (Value *R = simplifyFAdd(AllOpnds, 1))
return R;
}
return nullptr;
}
Value *FAddCombine::simplifyFAdd(AddendVect& Addends, unsigned InstrQuota) {
unsigned AddendNum = Addends.size();
assert(AddendNum <= 4 && "Too many addends");
// For saving intermediate results;
unsigned NextTmpIdx = 0;
FAddend TmpResult[3];
// Points to the constant addend of the resulting simplified expression.
// If the resulting expr has constant-addend, this constant-addend is
// desirable to reside at the top of the resulting expression tree. Placing
// constant close to supper-expr(s) will potentially reveal some optimization
// opportunities in super-expr(s).
const FAddend *ConstAdd = nullptr;
// Simplified addends are placed <SimpVect>.
AddendVect SimpVect;
// The outer loop works on one symbolic-value at a time. Suppose the input
// addends are : <a1, x>, <b1, y>, <a2, x>, <c1, z>, <b2, y>, ...
// The symbolic-values will be processed in this order: x, y, z.
for (unsigned SymIdx = 0; SymIdx < AddendNum; SymIdx++) {
const FAddend *ThisAddend = Addends[SymIdx];
if (!ThisAddend) {
// This addend was processed before.
continue;
}
Value *Val = ThisAddend->getSymVal();
unsigned StartIdx = SimpVect.size();
SimpVect.push_back(ThisAddend);
// The inner loop collects addends sharing same symbolic-value, and these
// addends will be later on folded into a single addend. Following above
// example, if the symbolic value "y" is being processed, the inner loop
// will collect two addends "<b1,y>" and "<b2,Y>". These two addends will
// be later on folded into "<b1+b2, y>".
for (unsigned SameSymIdx = SymIdx + 1;
SameSymIdx < AddendNum; SameSymIdx++) {
const FAddend *T = Addends[SameSymIdx];
if (T && T->getSymVal() == Val) {
// Set null such that next iteration of the outer loop will not process
// this addend again.
Addends[SameSymIdx] = nullptr;
SimpVect.push_back(T);
}
}
// If multiple addends share same symbolic value, fold them together.
if (StartIdx + 1 != SimpVect.size()) {
FAddend &R = TmpResult[NextTmpIdx ++];
R = *SimpVect[StartIdx];
for (unsigned Idx = StartIdx + 1; Idx < SimpVect.size(); Idx++)
R += *SimpVect[Idx];
// Pop all addends being folded and push the resulting folded addend.
SimpVect.resize(StartIdx);
if (Val) {
if (!R.isZero()) {
SimpVect.push_back(&R);
}
} else {
// Don't push constant addend at this time. It will be the last element
// of <SimpVect>.
ConstAdd = &R;
}
}
}
assert((NextTmpIdx <= array_lengthof(TmpResult) + 1) &&
"out-of-bound access");
if (ConstAdd)
SimpVect.push_back(ConstAdd);
Value *Result;
if (!SimpVect.empty())
Result = createNaryFAdd(SimpVect, InstrQuota);
else {
// The addition is folded to 0.0.
Result = ConstantFP::get(Instr->getType(), 0.0);
}
return Result;
}
Value *FAddCombine::createNaryFAdd
(const AddendVect &Opnds, unsigned InstrQuota) {
assert(!Opnds.empty() && "Expect at least one addend");
// Step 1: Check if the # of instructions needed exceeds the quota.
unsigned InstrNeeded = calcInstrNumber(Opnds);
if (InstrNeeded > InstrQuota)
return nullptr;
initCreateInstNum();
// step 2: Emit the N-ary addition.
// Note that at most three instructions are involved in Fadd-InstCombine: the
// addition in question, and at most two neighboring instructions.
// The resulting optimized addition should have at least one less instruction
// than the original addition expression tree. This implies that the resulting
// N-ary addition has at most two instructions, and we don't need to worry
// about tree-height when constructing the N-ary addition.
Value *LastVal = nullptr;
bool LastValNeedNeg = false;
// Iterate the addends, creating fadd/fsub using adjacent two addends.
for (const FAddend *Opnd : Opnds) {
bool NeedNeg;
Value *V = createAddendVal(*Opnd, NeedNeg);
if (!LastVal) {
LastVal = V;
LastValNeedNeg = NeedNeg;
continue;
}
if (LastValNeedNeg == NeedNeg) {
LastVal = createFAdd(LastVal, V);
continue;
}
if (LastValNeedNeg)
LastVal = createFSub(V, LastVal);
else
LastVal = createFSub(LastVal, V);
LastValNeedNeg = false;
}
if (LastValNeedNeg) {
LastVal = createFNeg(LastVal);
}
#ifndef NDEBUG
assert(CreateInstrNum == InstrNeeded &&
"Inconsistent in instruction numbers");
#endif
return LastVal;
}
Value *FAddCombine::createFSub(Value *Opnd0, Value *Opnd1) {
Value *V = Builder.CreateFSub(Opnd0, Opnd1);
if (Instruction *I = dyn_cast<Instruction>(V))
createInstPostProc(I);
return V;
}
Value *FAddCombine::createFNeg(Value *V) {
Value *Zero = cast<Value>(ConstantFP::getZeroValueForNegation(V->getType()));
Value *NewV = createFSub(Zero, V);
if (Instruction *I = dyn_cast<Instruction>(NewV))
createInstPostProc(I, true); // fneg's don't receive instruction numbers.
return NewV;
}
Value *FAddCombine::createFAdd(Value *Opnd0, Value *Opnd1) {
Value *V = Builder.CreateFAdd(Opnd0, Opnd1);
if (Instruction *I = dyn_cast<Instruction>(V))
createInstPostProc(I);
return V;
}
Value *FAddCombine::createFMul(Value *Opnd0, Value *Opnd1) {
Value *V = Builder.CreateFMul(Opnd0, Opnd1);
if (Instruction *I = dyn_cast<Instruction>(V))
createInstPostProc(I);
return V;
}
void FAddCombine::createInstPostProc(Instruction *NewInstr, bool NoNumber) {
NewInstr->setDebugLoc(Instr->getDebugLoc());
// Keep track of the number of instruction created.
if (!NoNumber)
incCreateInstNum();
// Propagate fast-math flags
NewInstr->setFastMathFlags(Instr->getFastMathFlags());
}
// Return the number of instruction needed to emit the N-ary addition.
// NOTE: Keep this function in sync with createAddendVal().
unsigned FAddCombine::calcInstrNumber(const AddendVect &Opnds) {
unsigned OpndNum = Opnds.size();
unsigned InstrNeeded = OpndNum - 1;
// The number of addends in the form of "(-1)*x".
unsigned NegOpndNum = 0;
// Adjust the number of instructions needed to emit the N-ary add.
for (const FAddend *Opnd : Opnds) {
if (Opnd->isConstant())
continue;
// The constant check above is really for a few special constant
// coefficients.
if (isa<UndefValue>(Opnd->getSymVal()))
continue;
const FAddendCoef &CE = Opnd->getCoef();
if (CE.isMinusOne() || CE.isMinusTwo())
NegOpndNum++;
// Let the addend be "c * x". If "c == +/-1", the value of the addend
// is immediately available; otherwise, it needs exactly one instruction
// to evaluate the value.
if (!CE.isMinusOne() && !CE.isOne())
InstrNeeded++;
}
if (NegOpndNum == OpndNum)
InstrNeeded++;
return InstrNeeded;
}
// Input Addend Value NeedNeg(output)
// ================================================================
// Constant C C false
// <+/-1, V> V coefficient is -1
// <2/-2, V> "fadd V, V" coefficient is -2
// <C, V> "fmul V, C" false
//
// NOTE: Keep this function in sync with FAddCombine::calcInstrNumber.
Value *FAddCombine::createAddendVal(const FAddend &Opnd, bool &NeedNeg) {
const FAddendCoef &Coeff = Opnd.getCoef();
if (Opnd.isConstant()) {
NeedNeg = false;
return Coeff.getValue(Instr->getType());
}
Value *OpndVal = Opnd.getSymVal();
if (Coeff.isMinusOne() || Coeff.isOne()) {
NeedNeg = Coeff.isMinusOne();
return OpndVal;
}
if (Coeff.isTwo() || Coeff.isMinusTwo()) {
NeedNeg = Coeff.isMinusTwo();
return createFAdd(OpndVal, OpndVal);
}
NeedNeg = false;
return createFMul(OpndVal, Coeff.getValue(Instr->getType()));
}
// Checks if any operand is negative and we can convert add to sub.
// This function checks for following negative patterns
// ADD(XOR(OR(Z, NOT(C)), C)), 1) == NEG(AND(Z, C))
// ADD(XOR(AND(Z, C), C), 1) == NEG(OR(Z, ~C))
// XOR(AND(Z, C), (C + 1)) == NEG(OR(Z, ~C)) if C is even
static Value *checkForNegativeOperand(BinaryOperator &I,
InstCombiner::BuilderTy &Builder) {
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
// This function creates 2 instructions to replace ADD, we need at least one
// of LHS or RHS to have one use to ensure benefit in transform.
if (!LHS->hasOneUse() && !RHS->hasOneUse())
return nullptr;
Value *X = nullptr, *Y = nullptr, *Z = nullptr;
const APInt *C1 = nullptr, *C2 = nullptr;
// if ONE is on other side, swap
if (match(RHS, m_Add(m_Value(X), m_One())))
std::swap(LHS, RHS);
if (match(LHS, m_Add(m_Value(X), m_One()))) {
// if XOR on other side, swap
if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1))))
std::swap(X, RHS);
if (match(X, m_Xor(m_Value(Y), m_APInt(C1)))) {
// X = XOR(Y, C1), Y = OR(Z, C2), C2 = NOT(C1) ==> X == NOT(AND(Z, C1))
// ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, AND(Z, C1))
if (match(Y, m_Or(m_Value(Z), m_APInt(C2))) && (*C2 == ~(*C1))) {
Value *NewAnd = Builder.CreateAnd(Z, *C1);
return Builder.CreateSub(RHS, NewAnd, "sub");
} else if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && (*C1 == *C2)) {
// X = XOR(Y, C1), Y = AND(Z, C2), C2 == C1 ==> X == NOT(OR(Z, ~C1))
// ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, OR(Z, ~C1))
Value *NewOr = Builder.CreateOr(Z, ~(*C1));
return Builder.CreateSub(RHS, NewOr, "sub");
}
}
}
// Restore LHS and RHS
LHS = I.getOperand(0);
RHS = I.getOperand(1);
// if XOR is on other side, swap
if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1))))
std::swap(LHS, RHS);
// C2 is ODD
// LHS = XOR(Y, C1), Y = AND(Z, C2), C1 == (C2 + 1) => LHS == NEG(OR(Z, ~C2))
// ADD(LHS, RHS) == SUB(RHS, OR(Z, ~C2))
if (match(LHS, m_Xor(m_Value(Y), m_APInt(C1))))
if (C1->countTrailingZeros() == 0)
if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && *C1 == (*C2 + 1)) {
Value *NewOr = Builder.CreateOr(Z, ~(*C2));
return Builder.CreateSub(RHS, NewOr, "sub");
}
return nullptr;
}
/// Wrapping flags may allow combining constants separated by an extend.
static Instruction *foldNoWrapAdd(BinaryOperator &Add,
InstCombiner::BuilderTy &Builder) {
Value *Op0 = Add.getOperand(0), *Op1 = Add.getOperand(1);
Type *Ty = Add.getType();
Constant *Op1C;
if (!match(Op1, m_Constant(Op1C)))
return nullptr;
// Try this match first because it results in an add in the narrow type.
// (zext (X +nuw C2)) + C1 --> zext (X + (C2 + trunc(C1)))
Value *X;
const APInt *C1, *C2;
if (match(Op1, m_APInt(C1)) &&
match(Op0, m_OneUse(m_ZExt(m_NUWAdd(m_Value(X), m_APInt(C2))))) &&
C1->isNegative() && C1->sge(-C2->sext(C1->getBitWidth()))) {
Constant *NewC =
ConstantInt::get(X->getType(), *C2 + C1->trunc(C2->getBitWidth()));
return new ZExtInst(Builder.CreateNUWAdd(X, NewC), Ty);
}
// More general combining of constants in the wide type.
// (sext (X +nsw NarrowC)) + C --> (sext X) + (sext(NarrowC) + C)
Constant *NarrowC;
if (match(Op0, m_OneUse(m_SExt(m_NSWAdd(m_Value(X), m_Constant(NarrowC)))))) {
Constant *WideC = ConstantExpr::getSExt(NarrowC, Ty);
Constant *NewC = ConstantExpr::getAdd(WideC, Op1C);
Value *WideX = Builder.CreateSExt(X, Ty);
return BinaryOperator::CreateAdd(WideX, NewC);
}
// (zext (X +nuw NarrowC)) + C --> (zext X) + (zext(NarrowC) + C)
if (match(Op0, m_OneUse(m_ZExt(m_NUWAdd(m_Value(X), m_Constant(NarrowC)))))) {
Constant *WideC = ConstantExpr::getZExt(NarrowC, Ty);
Constant *NewC = ConstantExpr::getAdd(WideC, Op1C);
Value *WideX = Builder.CreateZExt(X, Ty);
return BinaryOperator::CreateAdd(WideX, NewC);
}
return nullptr;
}
Instruction *InstCombiner::foldAddWithConstant(BinaryOperator &Add) {
Value *Op0 = Add.getOperand(0), *Op1 = Add.getOperand(1);
Constant *Op1C;
if (!match(Op1, m_Constant(Op1C)))
return nullptr;
if (Instruction *NV = foldBinOpIntoSelectOrPhi(Add))
return NV;
Value *X;
Constant *Op00C;
// add (sub C1, X), C2 --> sub (add C1, C2), X
if (match(Op0, m_Sub(m_Constant(Op00C), m_Value(X))))
return BinaryOperator::CreateSub(ConstantExpr::getAdd(Op00C, Op1C), X);
Value *Y;
// add (sub X, Y), -1 --> add (not Y), X
if (match(Op0, m_OneUse(m_Sub(m_Value(X), m_Value(Y)))) &&
match(Op1, m_AllOnes()))
return BinaryOperator::CreateAdd(Builder.CreateNot(Y), X);
// zext(bool) + C -> bool ? C + 1 : C
if (match(Op0, m_ZExt(m_Value(X))) &&
X->getType()->getScalarSizeInBits() == 1)
return SelectInst::Create(X, AddOne(Op1C), Op1);
// sext(bool) + C -> bool ? C - 1 : C
if (match(Op0, m_SExt(m_Value(X))) &&
X->getType()->getScalarSizeInBits() == 1)
return SelectInst::Create(X, SubOne(Op1C), Op1);
// ~X + C --> (C-1) - X
if (match(Op0, m_Not(m_Value(X))))
return BinaryOperator::CreateSub(SubOne(Op1C), X);
const APInt *C;
if (!match(Op1, m_APInt(C)))
return nullptr;
// (X | C2) + C --> (X | C2) ^ C2 iff (C2 == -C)
const APInt *C2;
if (match(Op0, m_Or(m_Value(), m_APInt(C2))) && *C2 == -*C)
return BinaryOperator::CreateXor(Op0, ConstantInt::get(Add.getType(), *C2));
if (C->isSignMask()) {
// If wrapping is not allowed, then the addition must set the sign bit:
// X + (signmask) --> X | signmask
if (Add.hasNoSignedWrap() || Add.hasNoUnsignedWrap())
return BinaryOperator::CreateOr(Op0, Op1);
// If wrapping is allowed, then the addition flips the sign bit of LHS:
// X + (signmask) --> X ^ signmask
return BinaryOperator::CreateXor(Op0, Op1);
}
// Is this add the last step in a convoluted sext?
// add(zext(xor i16 X, -32768), -32768) --> sext X
Type *Ty = Add.getType();
if (match(Op0, m_ZExt(m_Xor(m_Value(X), m_APInt(C2)))) &&
C2->isMinSignedValue() && C2->sext(Ty->getScalarSizeInBits()) == *C)
return CastInst::Create(Instruction::SExt, X, Ty);
if (C->isOneValue() && Op0->hasOneUse()) {
// add (sext i1 X), 1 --> zext (not X)
// TODO: The smallest IR representation is (select X, 0, 1), and that would
// not require the one-use check. But we need to remove a transform in
// visitSelect and make sure that IR value tracking for select is equal or
// better than for these ops.
if (match(Op0, m_SExt(m_Value(X))) &&
X->getType()->getScalarSizeInBits() == 1)
return new ZExtInst(Builder.CreateNot(X), Ty);
// Shifts and add used to flip and mask off the low bit:
// add (ashr (shl i32 X, 31), 31), 1 --> and (not X), 1
const APInt *C3;
if (match(Op0, m_AShr(m_Shl(m_Value(X), m_APInt(C2)), m_APInt(C3))) &&
C2 == C3 && *C2 == Ty->getScalarSizeInBits() - 1) {
Value *NotX = Builder.CreateNot(X);
return BinaryOperator::CreateAnd(NotX, ConstantInt::get(Ty, 1));
}
}
return nullptr;
}
// Matches multiplication expression Op * C where C is a constant. Returns the
// constant value in C and the other operand in Op. Returns true if such a
// match is found.
static bool MatchMul(Value *E, Value *&Op, APInt &C) {
const APInt *AI;
if (match(E, m_Mul(m_Value(Op), m_APInt(AI)))) {
C = *AI;
return true;
}
if (match(E, m_Shl(m_Value(Op), m_APInt(AI)))) {
C = APInt(AI->getBitWidth(), 1);
C <<= *AI;
return true;
}
return false;
}
// Matches remainder expression Op % C where C is a constant. Returns the
// constant value in C and the other operand in Op. Returns the signedness of
// the remainder operation in IsSigned. Returns true if such a match is
// found.
static bool MatchRem(Value *E, Value *&Op, APInt &C, bool &IsSigned) {
const APInt *AI;
IsSigned = false;
if (match(E, m_SRem(m_Value(Op), m_APInt(AI)))) {
IsSigned = true;
C = *AI;
return true;
}
if (match(E, m_URem(m_Value(Op), m_APInt(AI)))) {
C = *AI;
return true;
}
if (match(E, m_And(m_Value(Op), m_APInt(AI))) && (*AI + 1).isPowerOf2()) {
C = *AI + 1;
return true;
}
return false;
}
// Matches division expression Op / C with the given signedness as indicated
// by IsSigned, where C is a constant. Returns the constant value in C and the
// other operand in Op. Returns true if such a match is found.
static bool MatchDiv(Value *E, Value *&Op, APInt &C, bool IsSigned) {
const APInt *AI;
if (IsSigned && match(E, m_SDiv(m_Value(Op), m_APInt(AI)))) {
C = *AI;
return true;
}
if (!IsSigned) {
if (match(E, m_UDiv(m_Value(Op), m_APInt(AI)))) {
C = *AI;
return true;
}
if (match(E, m_LShr(m_Value(Op), m_APInt(AI)))) {
C = APInt(AI->getBitWidth(), 1);
C <<= *AI;
return true;
}
}
return false;
}
// Returns whether C0 * C1 with the given signedness overflows.
static bool MulWillOverflow(APInt &C0, APInt &C1, bool IsSigned) {
bool overflow;
if (IsSigned)
(void)C0.smul_ov(C1, overflow);
else
(void)C0.umul_ov(C1, overflow);
return overflow;
}
// Simplifies X % C0 + (( X / C0 ) % C1) * C0 to X % (C0 * C1), where (C0 * C1)
// does not overflow.
Value *InstCombiner::SimplifyAddWithRemainder(BinaryOperator &I) {
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
Value *X, *MulOpV;
APInt C0, MulOpC;
bool IsSigned;
// Match I = X % C0 + MulOpV * C0
if (((MatchRem(LHS, X, C0, IsSigned) && MatchMul(RHS, MulOpV, MulOpC)) ||
(MatchRem(RHS, X, C0, IsSigned) && MatchMul(LHS, MulOpV, MulOpC))) &&
C0 == MulOpC) {
Value *RemOpV;
APInt C1;
bool Rem2IsSigned;
// Match MulOpC = RemOpV % C1
if (MatchRem(MulOpV, RemOpV, C1, Rem2IsSigned) &&
IsSigned == Rem2IsSigned) {
Value *DivOpV;
APInt DivOpC;
// Match RemOpV = X / C0
if (MatchDiv(RemOpV, DivOpV, DivOpC, IsSigned) && X == DivOpV &&
C0 == DivOpC && !MulWillOverflow(C0, C1, IsSigned)) {
Value *NewDivisor =
ConstantInt::get(X->getType()->getContext(), C0 * C1);
return IsSigned ? Builder.CreateSRem(X, NewDivisor, "srem")
: Builder.CreateURem(X, NewDivisor, "urem");
}
}
}
return nullptr;
}
/// Fold
/// (1 << NBits) - 1
/// Into:
/// ~(-(1 << NBits))
/// Because a 'not' is better for bit-tracking analysis and other transforms
/// than an 'add'. The new shl is always nsw, and is nuw if old `and` was.
static Instruction *canonicalizeLowbitMask(BinaryOperator &I,
InstCombiner::BuilderTy &Builder) {
Value *NBits;
if (!match(&I, m_Add(m_OneUse(m_Shl(m_One(), m_Value(NBits))), m_AllOnes())))
return nullptr;
Constant *MinusOne = Constant::getAllOnesValue(NBits->getType());
Value *NotMask = Builder.CreateShl(MinusOne, NBits, "notmask");
// Be wary of constant folding.
if (auto *BOp = dyn_cast<BinaryOperator>(NotMask)) {
// Always NSW. But NUW propagates from `add`.
BOp->setHasNoSignedWrap();
BOp->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
}
return BinaryOperator::CreateNot(NotMask, I.getName());
}
static Instruction *foldToUnsignedSaturatedAdd(BinaryOperator &I) {
assert(I.getOpcode() == Instruction::Add && "Expecting add instruction");
Type *Ty = I.getType();
auto getUAddSat = [&]() {
return Intrinsic::getDeclaration(I.getModule(), Intrinsic::uadd_sat, Ty);
};
// add (umin X, ~Y), Y --> uaddsat X, Y
Value *X, *Y;
if (match(&I, m_c_Add(m_c_UMin(m_Value(X), m_Not(m_Value(Y))),
m_Deferred(Y))))
return CallInst::Create(getUAddSat(), { X, Y });
// add (umin X, ~C), C --> uaddsat X, C
const APInt *C, *NotC;
if (match(&I, m_Add(m_UMin(m_Value(X), m_APInt(NotC)), m_APInt(C))) &&
*C == ~*NotC)
return CallInst::Create(getUAddSat(), { X, ConstantInt::get(Ty, *C) });
return nullptr;
}
Instruction *
InstCombiner::canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(
BinaryOperator &I) {
assert((I.getOpcode() == Instruction::Add ||
I.getOpcode() == Instruction::Or ||
I.getOpcode() == Instruction::Sub) &&
"Expecting add/or/sub instruction");
// We have a subtraction/addition between a (potentially truncated) *logical*
// right-shift of X and a "select".
Value *X, *Select;
Instruction *LowBitsToSkip, *Extract;
if (!match(&I, m_c_BinOp(m_TruncOrSelf(m_CombineAnd(
m_LShr(m_Value(X), m_Instruction(LowBitsToSkip)),
m_Instruction(Extract))),
m_Value(Select))))
return nullptr;
// `add`/`or` is commutative; but for `sub`, "select" *must* be on RHS.
if (I.getOpcode() == Instruction::Sub && I.getOperand(1) != Select)
return nullptr;
Type *XTy = X->getType();
bool HadTrunc = I.getType() != XTy;
// If there was a truncation of extracted value, then we'll need to produce
// one extra instruction, so we need to ensure one instruction will go away.
if (HadTrunc && !match(&I, m_c_BinOp(m_OneUse(m_Value()), m_Value())))
return nullptr;
// Extraction should extract high NBits bits, with shift amount calculated as:
// low bits to skip = shift bitwidth - high bits to extract
// The shift amount itself may be extended, and we need to look past zero-ext
// when matching NBits, that will matter for matching later.
Constant *C;
Value *NBits;
if (!match(
LowBitsToSkip,
m_ZExtOrSelf(m_Sub(m_Constant(C), m_ZExtOrSelf(m_Value(NBits))))) ||
!match(C, m_SpecificInt_ICMP(ICmpInst::Predicate::ICMP_EQ,
APInt(C->getType()->getScalarSizeInBits(),
X->getType()->getScalarSizeInBits()))))
return nullptr;
// Sign-extending value can be zero-extended if we `sub`tract it,
// or sign-extended otherwise.
auto SkipExtInMagic = [&I](Value *&V) {
if (I.getOpcode() == Instruction::Sub)
match(V, m_ZExtOrSelf(m_Value(V)));
else
match(V, m_SExtOrSelf(m_Value(V)));
};
// Now, finally validate the sign-extending magic.
// `select` itself may be appropriately extended, look past that.
SkipExtInMagic(Select);
ICmpInst::Predicate Pred;
const APInt *Thr;
Value *SignExtendingValue, *Zero;
bool ShouldSignext;
// It must be a select between two values we will later establish to be a
// sign-extending value and a zero constant. The condition guarding the
// sign-extension must be based on a sign bit of the same X we had in `lshr`.
if (!match(Select, m_Select(m_ICmp(Pred, m_Specific(X), m_APInt(Thr)),
m_Value(SignExtendingValue), m_Value(Zero))) ||
!isSignBitCheck(Pred, *Thr, ShouldSignext))
return nullptr;
// icmp-select pair is commutative.
if (!ShouldSignext)
std::swap(SignExtendingValue, Zero);
// If we should not perform sign-extension then we must add/or/subtract zero.
if (!match(Zero, m_Zero()))
return nullptr;
// Otherwise, it should be some constant, left-shifted by the same NBits we
// had in `lshr`. Said left-shift can also be appropriately extended.
// Again, we must look past zero-ext when looking for NBits.
SkipExtInMagic(SignExtendingValue);
Constant *SignExtendingValueBaseConstant;
if (!match(SignExtendingValue,
m_Shl(m_Constant(SignExtendingValueBaseConstant),
m_ZExtOrSelf(m_Specific(NBits)))))
return nullptr;
// If we `sub`, then the constant should be one, else it should be all-ones.
if (I.getOpcode() == Instruction::Sub
? !match(SignExtendingValueBaseConstant, m_One())
: !match(SignExtendingValueBaseConstant, m_AllOnes()))
return nullptr;
auto *NewAShr = BinaryOperator::CreateAShr(X, LowBitsToSkip,
Extract->getName() + ".sext");
NewAShr->copyIRFlags(Extract); // Preserve `exact`-ness.
if (!HadTrunc)
return NewAShr;
Builder.Insert(NewAShr);
return TruncInst::CreateTruncOrBitCast(NewAShr, I.getType());
}
Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
if (Value *V = SimplifyAddInst(I.getOperand(0), I.getOperand(1),
I.hasNoSignedWrap(), I.hasNoUnsignedWrap(),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (SimplifyAssociativeOrCommutative(I))
return &I;
if (Instruction *X = foldVectorBinop(I))
return X;
// (A*B)+(A*C) -> A*(B+C) etc
if (Value *V = SimplifyUsingDistributiveLaws(I))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldAddWithConstant(I))
return X;
if (Instruction *X = foldNoWrapAdd(I, Builder))
return X;
// FIXME: This should be moved into the above helper function to allow these
// transforms for general constant or constant splat vectors.
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
Type *Ty = I.getType();
if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
Value *XorLHS = nullptr; ConstantInt *XorRHS = nullptr;
if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
unsigned TySizeBits = Ty->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, 0, &I))
ExtendAmt = 0;
}
if (ExtendAmt) {
Constant *ShAmt = ConstantInt::get(Ty, 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()) {
KnownBits LHSKnown = computeKnownBits(XorLHS, 0, &I);
if ((XorRHS->getValue() | LHSKnown.Zero).isAllOnesValue())
return BinaryOperator::CreateSub(ConstantExpr::getAdd(XorRHS, CI),
XorLHS);
}
// (X + signmask) + C could have gotten canonicalized to (X^signmask) + C,
// transform them into (X + (signmask ^ C))
if (XorRHS->getValue().isSignMask())
return BinaryOperator::CreateAdd(XorLHS,
ConstantExpr::getXor(XorRHS, CI));
}
}
if (Ty->isIntOrIntVectorTy(1))
return BinaryOperator::CreateXor(LHS, RHS);
// X + X --> X << 1
if (LHS == RHS) {
auto *Shl = BinaryOperator::CreateShl(LHS, ConstantInt::get(Ty, 1));
Shl->setHasNoSignedWrap(I.hasNoSignedWrap());
Shl->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
return Shl;
}
Value *A, *B;
if (match(LHS, m_Neg(m_Value(A)))) {
// -A + -B --> -(A + B)
if (match(RHS, m_Neg(m_Value(B))))
return BinaryOperator::CreateNeg(Builder.CreateAdd(A, B));
// -A + B --> B - A
return BinaryOperator::CreateSub(RHS, A);
}
// A + -B --> A - B
if (match(RHS, m_Neg(m_Value(B))))
return BinaryOperator::CreateSub(LHS, B);
if (Value *V = checkForNegativeOperand(I, Builder))
return replaceInstUsesWith(I, V);
// (A + 1) + ~B --> A - B
// ~B + (A + 1) --> A - B
// (~B + A) + 1 --> A - B
// (A + ~B) + 1 --> A - B
if (match(&I, m_c_BinOp(m_Add(m_Value(A), m_One()), m_Not(m_Value(B)))) ||
match(&I, m_BinOp(m_c_Add(m_Not(m_Value(B)), m_Value(A)), m_One())))
return BinaryOperator::CreateSub(A, B);
// X % C0 + (( X / C0 ) % C1) * C0 => X % (C0 * C1)
if (Value *V = SimplifyAddWithRemainder(I)) return replaceInstUsesWith(I, V);
// A+B --> A|B iff A and B have no bits set in common.
if (haveNoCommonBitsSet(LHS, RHS, DL, &AC, &I, &DT))
return BinaryOperator::CreateOr(LHS, RHS);
// FIXME: We already did a check for ConstantInt RHS above this.
// FIXME: Is this pattern covered by another fold? No regression tests fail on
// removal.
if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
// (X & FF00) + xx00 -> (X+xx00) & FF00
Value *X;
ConstantInt *C2;
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);
}
}
}
// 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);
}
}
if (Instruction *Ext = narrowMathIfNoOverflow(I))
return Ext;
// (add (xor A, B) (and A, B)) --> (or A, B)
// (add (and A, B) (xor A, B)) --> (or A, B)
if (match(&I, m_c_BinOp(m_Xor(m_Value(A), m_Value(B)),
m_c_And(m_Deferred(A), m_Deferred(B)))))
return BinaryOperator::CreateOr(A, B);
// (add (or A, B) (and A, B)) --> (add A, B)
// (add (and A, B) (or A, B)) --> (add A, B)
if (match(&I, m_c_BinOp(m_Or(m_Value(A), m_Value(B)),
m_c_And(m_Deferred(A), m_Deferred(B))))) {
I.setOperand(0, A);
I.setOperand(1, B);
return &I;
}
// TODO(jingyue): Consider willNotOverflowSignedAdd and
// willNotOverflowUnsignedAdd to reduce the number of invocations of
// computeKnownBits.
bool Changed = false;
if (!I.hasNoSignedWrap() && willNotOverflowSignedAdd(LHS, RHS, I)) {
Changed = true;
I.setHasNoSignedWrap(true);
}
if (!I.hasNoUnsignedWrap() && willNotOverflowUnsignedAdd(LHS, RHS, I)) {
Changed = true;
I.setHasNoUnsignedWrap(true);
}
if (Instruction *V = canonicalizeLowbitMask(I, Builder))
return V;
if (Instruction *V =
canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(I))
return V;
if (Instruction *SatAdd = foldToUnsignedSaturatedAdd(I))
return SatAdd;
return Changed ? &I : nullptr;
}
/// Eliminate an op from a linear interpolation (lerp) pattern.
static Instruction *factorizeLerp(BinaryOperator &I,
InstCombiner::BuilderTy &Builder) {
Value *X, *Y, *Z;
if (!match(&I, m_c_FAdd(m_OneUse(m_c_FMul(m_Value(Y),
m_OneUse(m_FSub(m_FPOne(),
m_Value(Z))))),
m_OneUse(m_c_FMul(m_Value(X), m_Deferred(Z))))))
return nullptr;
// (Y * (1.0 - Z)) + (X * Z) --> Y + Z * (X - Y) [8 commuted variants]
Value *XY = Builder.CreateFSubFMF(X, Y, &I);
Value *MulZ = Builder.CreateFMulFMF(Z, XY, &I);
return BinaryOperator::CreateFAddFMF(Y, MulZ, &I);
}
/// Factor a common operand out of fadd/fsub of fmul/fdiv.
static Instruction *factorizeFAddFSub(BinaryOperator &I,
InstCombiner::BuilderTy &Builder) {
assert((I.getOpcode() == Instruction::FAdd ||
I.getOpcode() == Instruction::FSub) && "Expecting fadd/fsub");
assert(I.hasAllowReassoc() && I.hasNoSignedZeros() &&
"FP factorization requires FMF");
if (Instruction *Lerp = factorizeLerp(I, Builder))
return Lerp;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
Value *X, *Y, *Z;
bool IsFMul;
if ((match(Op0, m_OneUse(m_FMul(m_Value(X), m_Value(Z)))) &&
match(Op1, m_OneUse(m_c_FMul(m_Value(Y), m_Specific(Z))))) ||
(match(Op0, m_OneUse(m_FMul(m_Value(Z), m_Value(X)))) &&
match(Op1, m_OneUse(m_c_FMul(m_Value(Y), m_Specific(Z))))))
IsFMul = true;
else if (match(Op0, m_OneUse(m_FDiv(m_Value(X), m_Value(Z)))) &&
match(Op1, m_OneUse(m_FDiv(m_Value(Y), m_Specific(Z)))))
IsFMul = false;
else
return nullptr;
// (X * Z) + (Y * Z) --> (X + Y) * Z
// (X * Z) - (Y * Z) --> (X - Y) * Z
// (X / Z) + (Y / Z) --> (X + Y) / Z
// (X / Z) - (Y / Z) --> (X - Y) / Z
bool IsFAdd = I.getOpcode() == Instruction::FAdd;
Value *XY = IsFAdd ? Builder.CreateFAddFMF(X, Y, &I)
: Builder.CreateFSubFMF(X, Y, &I);
// Bail out if we just created a denormal constant.
// TODO: This is copied from a previous implementation. Is it necessary?
const APFloat *C;
if (match(XY, m_APFloat(C)) && !C->isNormal())
return nullptr;
return IsFMul ? BinaryOperator::CreateFMulFMF(XY, Z, &I)
: BinaryOperator::CreateFDivFMF(XY, Z, &I);
}
Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
if (Value *V = SimplifyFAddInst(I.getOperand(0), I.getOperand(1),
I.getFastMathFlags(),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (SimplifyAssociativeOrCommutative(I))
return &I;
if (Instruction *X = foldVectorBinop(I))
return X;
if (Instruction *FoldedFAdd = foldBinOpIntoSelectOrPhi(I))
return FoldedFAdd;
// (-X) + Y --> Y - X
Value *X, *Y;
if (match(&I, m_c_FAdd(m_FNeg(m_Value(X)), m_Value(Y))))
return BinaryOperator::CreateFSubFMF(Y, X, &I);
// Similar to above, but look through fmul/fdiv for the negated term.
// (-X * Y) + Z --> Z - (X * Y) [4 commuted variants]
Value *Z;
if (match(&I, m_c_FAdd(m_OneUse(m_c_FMul(m_FNeg(m_Value(X)), m_Value(Y))),
m_Value(Z)))) {
Value *XY = Builder.CreateFMulFMF(X, Y, &I);
return BinaryOperator::CreateFSubFMF(Z, XY, &I);
}
// (-X / Y) + Z --> Z - (X / Y) [2 commuted variants]
// (X / -Y) + Z --> Z - (X / Y) [2 commuted variants]
if (match(&I, m_c_FAdd(m_OneUse(m_FDiv(m_FNeg(m_Value(X)), m_Value(Y))),
m_Value(Z))) ||
match(&I, m_c_FAdd(m_OneUse(m_FDiv(m_Value(X), m_FNeg(m_Value(Y)))),
m_Value(Z)))) {
Value *XY = Builder.CreateFDivFMF(X, Y, &I);
return BinaryOperator::CreateFSubFMF(Z, XY, &I);
}
// Check for (fadd double (sitofp x), y), see if we can merge this into an
// integer add followed by a promotion.
Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) {
Value *LHSIntVal = LHSConv->getOperand(0);
Type *FPType = LHSConv->getType();
// TODO: This check is overly conservative. In many cases known bits
// analysis can tell us that the result of the addition has less significant
// bits than the integer type can hold.
auto IsValidPromotion = [](Type *FTy, Type *ITy) {
Type *FScalarTy = FTy->getScalarType();
Type *IScalarTy = ITy->getScalarType();
// Do we have enough bits in the significand to represent the result of
// the integer addition?
unsigned MaxRepresentableBits =
APFloat::semanticsPrecision(FScalarTy->getFltSemantics());
return IScalarTy->getIntegerBitWidth() <= MaxRepresentableBits;
};
// (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))
if (IsValidPromotion(FPType, LHSIntVal->getType())) {
Constant *CI =
ConstantExpr::getFPToSI(CFP, LHSIntVal->getType());
if (LHSConv->hasOneUse() &&
ConstantExpr::getSIToFP(CI, I.getType()) == CFP &&
willNotOverflowSignedAdd(LHSIntVal, CI, I)) {
// Insert the new integer add.
Value *NewAdd = Builder.CreateNSWAdd(LHSIntVal, 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)) {
Value *RHSIntVal = RHSConv->getOperand(0);
// It's enough to check LHS types only because we require int types to
// be the same for this transform.
if (IsValidPromotion(FPType, LHSIntVal->getType())) {
// Only do this if x/y have the same type, if at least 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 (LHSIntVal->getType() == RHSIntVal->getType() &&
(LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
willNotOverflowSignedAdd(LHSIntVal, RHSIntVal, I)) {
// Insert the new integer add.
Value *NewAdd = Builder.CreateNSWAdd(LHSIntVal, RHSIntVal, "addconv");
return new SIToFPInst(NewAdd, I.getType());
}
}
}
}
// Handle specials cases for FAdd with selects feeding the operation
if (Value *V = SimplifySelectsFeedingBinaryOp(I, LHS, RHS))
return replaceInstUsesWith(I, V);
if (I.hasAllowReassoc() && I.hasNoSignedZeros()) {
if (Instruction *F = factorizeFAddFSub(I, Builder))
return F;
if (Value *V = FAddCombine(Builder).simplify(&I))
return replaceInstUsesWith(I, V);
}
return nullptr;
}
/// 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, bool IsNUW) {
// 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 = nullptr, *GEP2 = nullptr;
// 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;
}
}
}
if (!GEP1)
// No GEP found.
return nullptr;
if (GEP2) {
// (gep X, ...) - (gep X, ...)
//
// Avoid duplicating the arithmetic if there are more than one non-constant
// indices between the two GEPs and either GEP has a non-constant index and
// multiple users. If zero non-constant index, the result is a constant and
// there is no duplication. If one non-constant index, the result is an add
// or sub with a constant, which is no larger than the original code, and
// there's no duplicated arithmetic, even if either GEP has multiple
// users. If more than one non-constant indices combined, as long as the GEP
// with at least one non-constant index doesn't have multiple users, there
// is no duplication.
unsigned NumNonConstantIndices1 = GEP1->countNonConstantIndices();
unsigned NumNonConstantIndices2 = GEP2->countNonConstantIndices();
if (NumNonConstantIndices1 + NumNonConstantIndices2 > 1 &&
((NumNonConstantIndices1 > 0 && !GEP1->hasOneUse()) ||
(NumNonConstantIndices2 > 0 && !GEP2->hasOneUse()))) {
return nullptr;
}
}
// Emit the offset of the GEP and an intptr_t.
Value *Result = EmitGEPOffset(GEP1);
// If this is a single inbounds GEP and the original sub was nuw,
// then the final multiplication is also nuw. We match an extra add zero
// here, because that's what EmitGEPOffset() generates.
Instruction *I;
if (IsNUW && !GEP2 && !Swapped && GEP1->isInBounds() &&
match(Result, m_Add(m_Instruction(I), m_Zero())) &&
I->getOpcode() == Instruction::Mul)
I->setHasNoUnsignedWrap();
// 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) {
if (Value *V = SimplifySubInst(I.getOperand(0), I.getOperand(1),
I.hasNoSignedWrap(), I.hasNoUnsignedWrap(),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldVectorBinop(I))
return X;
// (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.
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = dyn_castNegVal(Op1)) {
BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);
if (const auto *BO = dyn_cast<BinaryOperator>(Op1)) {
assert(BO->getOpcode() == Instruction::Sub &&
"Expected a subtraction operator!");
if (BO->hasNoSignedWrap() && I.hasNoSignedWrap())
Res->setHasNoSignedWrap(true);
} else {
if (cast<Constant>(Op1)->isNotMinSignedValue() && I.hasNoSignedWrap())
Res->setHasNoSignedWrap(true);
}
return Res;
}
if (I.getType()->isIntOrIntVectorTy(1))
return BinaryOperator::CreateXor(Op0, Op1);
// Replace (-1 - A) with (~A).
if (match(Op0, m_AllOnes()))
return BinaryOperator::CreateNot(Op1);
// (~X) - (~Y) --> Y - X
Value *X, *Y;
if (match(Op0, m_Not(m_Value(X))) && match(Op1, m_Not(m_Value(Y))))
return BinaryOperator::CreateSub(Y, X);
// (X + -1) - Y --> ~Y + X
if (match(Op0, m_OneUse(m_Add(m_Value(X), m_AllOnes()))))
return BinaryOperator::CreateAdd(Builder.CreateNot(Op1), X);
// Y - (X + 1) --> ~X + Y
if (match(Op1, m_OneUse(m_Add(m_Value(X), m_One()))))
return BinaryOperator::CreateAdd(Builder.CreateNot(X), Op0);
// Y - ~X --> (X + 1) + Y
if (match(Op1, m_OneUse(m_Not(m_Value(X))))) {
return BinaryOperator::CreateAdd(
Builder.CreateAdd(Op0, ConstantInt::get(I.getType(), 1)), X);
}
if (Constant *C = dyn_cast<Constant>(Op0)) {
bool IsNegate = match(C, m_ZeroInt());
Value *X;
if (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) {
// 0 - (zext bool) --> sext bool
// C - (zext bool) --> bool ? C - 1 : C
if (IsNegate)
return CastInst::CreateSExtOrBitCast(X, I.getType());
return SelectInst::Create(X, SubOne(C), C);
}
if (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) {
// 0 - (sext bool) --> zext bool
// C - (sext bool) --> bool ? C + 1 : C
if (IsNegate)
return CastInst::CreateZExtOrBitCast(X, I.getType());
return SelectInst::Create(X, AddOne(C), C);
}
// C - ~X == X + (1+C)
if (match(Op1, m_Not(m_Value(X))))
return BinaryOperator::CreateAdd(X, AddOne(C));
// Try to fold constant sub into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
// Try to fold constant sub into PHI values.
if (PHINode *PN = dyn_cast<PHINode>(Op1))
if (Instruction *R = foldOpIntoPhi(I, PN))
return R;
Constant *C2;
// C-(C2-X) --> X+(C-C2)
if (match(Op1, m_Sub(m_Constant(C2), m_Value(X))))
return BinaryOperator::CreateAdd(X, ConstantExpr::getSub(C, C2));
// C-(X+C2) --> (C-C2)-X
if (match(Op1, m_Add(m_Value(X), m_Constant(C2))))
return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X);
}
const APInt *Op0C;
if (match(Op0, m_APInt(Op0C))) {
if (Op0C->isNullValue()) {
Value *Op1Wide;
match(Op1, m_TruncOrSelf(m_Value(Op1Wide)));
bool HadTrunc = Op1Wide != Op1;
bool NoTruncOrTruncIsOneUse = !HadTrunc || Op1->hasOneUse();
unsigned BitWidth = Op1Wide->getType()->getScalarSizeInBits();
Value *X;
const APInt *ShAmt;
// -(X >>u 31) -> (X >>s 31)
if (NoTruncOrTruncIsOneUse &&
match(Op1Wide, m_LShr(m_Value(X), m_APInt(ShAmt))) &&
*ShAmt == BitWidth - 1) {
Value *ShAmtOp = cast<Instruction>(Op1Wide)->getOperand(1);
Instruction *NewShift = BinaryOperator::CreateAShr(X, ShAmtOp);
NewShift->copyIRFlags(Op1Wide);
if (!HadTrunc)
return NewShift;
Builder.Insert(NewShift);
return TruncInst::CreateTruncOrBitCast(NewShift, Op1->getType());
}
// -(X >>s 31) -> (X >>u 31)
if (NoTruncOrTruncIsOneUse &&
match(Op1Wide, m_AShr(m_Value(X), m_APInt(ShAmt))) &&
*ShAmt == BitWidth - 1) {
Value *ShAmtOp = cast<Instruction>(Op1Wide)->getOperand(1);
Instruction *NewShift = BinaryOperator::CreateLShr(X, ShAmtOp);
NewShift->copyIRFlags(Op1Wide);
if (!HadTrunc)
return NewShift;
Builder.Insert(NewShift);
return TruncInst::CreateTruncOrBitCast(NewShift, Op1->getType());
}
if (!HadTrunc && Op1->hasOneUse()) {
Value *LHS, *RHS;
SelectPatternFlavor SPF = matchSelectPattern(Op1, LHS, RHS).Flavor;
if (SPF == SPF_ABS || SPF == SPF_NABS) {
// This is a negate of an ABS/NABS pattern. Just swap the operands
// of the select.
cast<SelectInst>(Op1)->swapValues();
// Don't swap prof metadata, we didn't change the branch behavior.
return replaceInstUsesWith(I, Op1);
}
}
}
// Turn this into a xor if LHS is 2^n-1 and the remaining bits are known
// zero.
if (Op0C->isMask()) {
KnownBits RHSKnown = computeKnownBits(Op1, 0, &I);
if ((*Op0C | RHSKnown.Zero).isAllOnesValue())
return BinaryOperator::CreateXor(Op1, Op0);
}
}
{
Value *Y;
// X-(X+Y) == -Y X-(Y+X) == -Y
if (match(Op1, m_c_Add(m_Specific(Op0), m_Value(Y))))
return BinaryOperator::CreateNeg(Y);
// (X-Y)-X == -Y
if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y))))
return BinaryOperator::CreateNeg(Y);
}
// (sub (or A, B) (and A, B)) --> (xor A, B)
{
Value *A, *B;
if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
match(Op0, m_c_Or(m_Specific(A), m_Specific(B))))
return BinaryOperator::CreateXor(A, B);
}
// (sub (and A, B) (or A, B)) --> neg (xor A, B)
{
Value *A, *B;
if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
match(Op1, m_c_Or(m_Specific(A), m_Specific(B))) &&
(Op0->hasOneUse() || Op1->hasOneUse()))
return BinaryOperator::CreateNeg(Builder.CreateXor(A, B));
}
// (sub (or A, B), (xor A, B)) --> (and A, B)
{
Value *A, *B;
if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
match(Op0, m_c_Or(m_Specific(A), m_Specific(B))))
return BinaryOperator::CreateAnd(A, B);
}
// (sub (xor A, B) (or A, B)) --> neg (and A, B)
{
Value *A, *B;
if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
match(Op1, m_c_Or(m_Specific(A), m_Specific(B))) &&
(Op0->hasOneUse() || Op1->hasOneUse()))
return BinaryOperator::CreateNeg(Builder.CreateAnd(A, B));
}
{
Value *Y;
// ((X | Y) - X) --> (~X & Y)
if (match(Op0, m_OneUse(m_c_Or(m_Value(Y), m_Specific(Op1)))))
return BinaryOperator::CreateAnd(
Y, Builder.CreateNot(Op1, Op1->getName() + ".not"));
}
{
// (sub (and Op1, (neg X)), Op1) --> neg (and Op1, (add X, -1))
Value *X;
if (match(Op0, m_OneUse(m_c_And(m_Specific(Op1),
m_OneUse(m_Neg(m_Value(X))))))) {
return BinaryOperator::CreateNeg(Builder.CreateAnd(
Op1, Builder.CreateAdd(X, Constant::getAllOnesValue(I.getType()))));
}
}
{
// (sub (and Op1, C), Op1) --> neg (and Op1, ~C)
Constant *C;
if (match(Op0, m_OneUse(m_And(m_Specific(Op1), m_Constant(C))))) {
return BinaryOperator::CreateNeg(
Builder.CreateAnd(Op1, Builder.CreateNot(C)));
}
}
{
// If we have a subtraction between some value and a select between
// said value and something else, sink subtraction into select hands, i.e.:
// sub (select %Cond, %TrueVal, %FalseVal), %Op1
// ->
// select %Cond, (sub %TrueVal, %Op1), (sub %FalseVal, %Op1)
// or
// sub %Op0, (select %Cond, %TrueVal, %FalseVal)
// ->
// select %Cond, (sub %Op0, %TrueVal), (sub %Op0, %FalseVal)
// This will result in select between new subtraction and 0.
auto SinkSubIntoSelect =
[Ty = I.getType()](Value *Select, Value *OtherHandOfSub,
auto SubBuilder) -> Instruction * {
Value *Cond, *TrueVal, *FalseVal;
if (!match(Select, m_OneUse(m_Select(m_Value(Cond), m_Value(TrueVal),
m_Value(FalseVal)))))
return nullptr;
if (OtherHandOfSub != TrueVal && OtherHandOfSub != FalseVal)
return nullptr;
// While it is really tempting to just create two subtractions and let
// InstCombine fold one of those to 0, it isn't possible to do so
// because of worklist visitation order. So ugly it is.
bool OtherHandOfSubIsTrueVal = OtherHandOfSub == TrueVal;
Value *NewSub = SubBuilder(OtherHandOfSubIsTrueVal ? FalseVal : TrueVal);
Constant *Zero = Constant::getNullValue(Ty);
SelectInst *NewSel =
SelectInst::Create(Cond, OtherHandOfSubIsTrueVal ? Zero : NewSub,
OtherHandOfSubIsTrueVal ? NewSub : Zero);
// Preserve prof metadata if any.
NewSel->copyMetadata(cast<Instruction>(*Select));
return NewSel;
};
if (Instruction *NewSel = SinkSubIntoSelect(
/*Select=*/Op0, /*OtherHandOfSub=*/Op1,
[Builder = &Builder, Op1](Value *OtherHandOfSelect) {
return Builder->CreateSub(OtherHandOfSelect,
/*OtherHandOfSub=*/Op1);
}))
return NewSel;
if (Instruction *NewSel = SinkSubIntoSelect(
/*Select=*/Op1, /*OtherHandOfSub=*/Op0,
[Builder = &Builder, Op0](Value *OtherHandOfSelect) {
return Builder->CreateSub(/*OtherHandOfSub=*/Op0,
OtherHandOfSelect);
}))
return NewSel;
}
if (Op1->hasOneUse()) {
Value *X = nullptr, *Y = nullptr, *Z = nullptr;
Constant *C = nullptr;
// (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_c_And(m_Value(Y), m_Specific(Op0))))
return BinaryOperator::CreateAnd(Op0,
Builder.CreateNot(Y, Y->getName() + ".not"));
// 0 - (X sdiv C) -> (X sdiv -C) provided the negation doesn't overflow.
if (match(Op0, m_Zero())) {
Constant *Op11C;
if (match(Op1, m_SDiv(m_Value(X), m_Constant(Op11C))) &&
!Op11C->containsUndefElement() && Op11C->isNotMinSignedValue() &&
Op11C->isNotOneValue()) {
Instruction *BO =
BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(Op11C));
BO->setIsExact(cast<BinaryOperator>(Op1)->isExact());
return BO;
}
}
// 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);
// Subtracting -1/0 is the same as adding 1/0:
// sub [nsw] Op0, sext(bool Y) -> add [nsw] Op0, zext(bool Y)
// 'nuw' is dropped in favor of the canonical form.
if (match(Op1, m_SExt(m_Value(Y))) &&
Y->getType()->getScalarSizeInBits() == 1) {
Value *Zext = Builder.CreateZExt(Y, I.getType());
BinaryOperator *Add = BinaryOperator::CreateAdd(Op0, Zext);
Add->setHasNoSignedWrap(I.hasNoSignedWrap());
return Add;
}
// sub [nsw] X, zext(bool Y) -> add [nsw] X, sext(bool Y)
// 'nuw' is dropped in favor of the canonical form.
if (match(Op1, m_ZExt(m_Value(Y))) && Y->getType()->isIntOrIntVectorTy(1)) {
Value *Sext = Builder.CreateSExt(Y, I.getType());
BinaryOperator *Add = BinaryOperator::CreateAdd(Op0, Sext);
Add->setHasNoSignedWrap(I.hasNoSignedWrap());
return Add;
}
// X - A*-B -> X + A*B
// X - -A*B -> X + A*B
Value *A, *B;
if (match(Op1, m_c_Mul(m_Value(A), m_Neg(m_Value(B)))))
return BinaryOperator::CreateAdd(Op0, Builder.CreateMul(A, B));
// X - A*C -> X + A*-C
// No need to handle commuted multiply because multiply handling will
// ensure constant will be move to the right hand side.
if (match(Op1, m_Mul(m_Value(A), m_Constant(C))) && !isa<ConstantExpr>(C)) {
Value *NewMul = Builder.CreateMul(A, ConstantExpr::getNeg(C));
return BinaryOperator::CreateAdd(Op0, NewMul);
}
}
{
// ~A - Min/Max(~A, O) -> Max/Min(A, ~O) - A
// ~A - Min/Max(O, ~A) -> Max/Min(A, ~O) - A
// Min/Max(~A, O) - ~A -> A - Max/Min(A, ~O)
// Min/Max(O, ~A) - ~A -> A - Max/Min(A, ~O)
// So long as O here is freely invertible, this will be neutral or a win.
Value *LHS, *RHS, *A;
Value *NotA = Op0, *MinMax = Op1;
SelectPatternFlavor SPF = matchSelectPattern(MinMax, LHS, RHS).Flavor;
if (!SelectPatternResult::isMinOrMax(SPF)) {
NotA = Op1;
MinMax = Op0;
SPF = matchSelectPattern(MinMax, LHS, RHS).Flavor;
}
if (SelectPatternResult::isMinOrMax(SPF) &&
match(NotA, m_Not(m_Value(A))) && (NotA == LHS || NotA == RHS)) {
if (NotA == LHS)
std::swap(LHS, RHS);
// LHS is now O above and expected to have at least 2 uses (the min/max)
// NotA is epected to have 2 uses from the min/max and 1 from the sub.
if (isFreeToInvert(LHS, !LHS->hasNUsesOrMore(3)) &&
!NotA->hasNUsesOrMore(4)) {
// Note: We don't generate the inverse max/min, just create the not of
// it and let other folds do the rest.
Value *Not = Builder.CreateNot(MinMax);
if (NotA == Op0)
return BinaryOperator::CreateSub(Not, A);
else
return BinaryOperator::CreateSub(A, Not);
}
}
}
// Optimize pointer differences into the same array into a size. Consider:
// &A[10] - &A[0]: we should compile this to "10".
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(),
I.hasNoUnsignedWrap()))
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(),
/* IsNUW */ false))
return replaceInstUsesWith(I, Res);
// Canonicalize a shifty way to code absolute value to the common pattern.
// There are 2 potential commuted variants.
// We're relying on the fact that we only do this transform when the shift has
// exactly 2 uses and the xor has exactly 1 use (otherwise, we might increase
// instructions).
Value *A;
const APInt *ShAmt;
Type *Ty = I.getType();
if (match(Op1, m_AShr(m_Value(A), m_APInt(ShAmt))) &&
Op1->hasNUses(2) && *ShAmt == Ty->getScalarSizeInBits() - 1 &&
match(Op0, m_OneUse(m_c_Xor(m_Specific(A), m_Specific(Op1))))) {
// B = ashr i32 A, 31 ; smear the sign bit
// sub (xor A, B), B ; flip bits if negative and subtract -1 (add 1)
// --> (A < 0) ? -A : A
Value *Cmp = Builder.CreateICmpSLT(A, ConstantInt::getNullValue(Ty));
// Copy the nuw/nsw flags from the sub to the negate.
Value *Neg = Builder.CreateNeg(A, "", I.hasNoUnsignedWrap(),
I.hasNoSignedWrap());
return SelectInst::Create(Cmp, Neg, A);
}
if (Instruction *V =
canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(I))
return V;
if (Instruction *Ext = narrowMathIfNoOverflow(I))
return Ext;
bool Changed = false;
if (!I.hasNoSignedWrap() && willNotOverflowSignedSub(Op0, Op1, I)) {
Changed = true;
I.setHasNoSignedWrap(true);
}
if (!I.hasNoUnsignedWrap() && willNotOverflowUnsignedSub(Op0, Op1, I)) {
Changed = true;
I.setHasNoUnsignedWrap(true);
}
return Changed ? &I : nullptr;
}
/// This eliminates floating-point negation in either 'fneg(X)' or
/// 'fsub(-0.0, X)' form by combining into a constant operand.
static Instruction *foldFNegIntoConstant(Instruction &I) {
Value *X;
Constant *C;
// Fold negation into constant operand. This is limited with one-use because
// fneg is assumed better for analysis and cheaper in codegen than fmul/fdiv.
// -(X * C) --> X * (-C)
// FIXME: It's arguable whether these should be m_OneUse or not. The current
// belief is that the FNeg allows for better reassociation opportunities.
if (match(&I, m_FNeg(m_OneUse(m_FMul(m_Value(X), m_Constant(C))))))
return BinaryOperator::CreateFMulFMF(X, ConstantExpr::getFNeg(C), &I);
// -(X / C) --> X / (-C)
if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Value(X), m_Constant(C))))))
return BinaryOperator::CreateFDivFMF(X, ConstantExpr::getFNeg(C), &I);
// -(C / X) --> (-C) / X
if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Constant(C), m_Value(X))))))
return BinaryOperator::CreateFDivFMF(ConstantExpr::getFNeg(C), X, &I);
return nullptr;
}
static Instruction *hoistFNegAboveFMulFDiv(Instruction &I,
InstCombiner::BuilderTy &Builder) {
Value *FNeg;
if (!match(&I, m_FNeg(m_Value(FNeg))))
return nullptr;
Value *X, *Y;
if (match(FNeg, m_OneUse(m_FMul(m_Value(X), m_Value(Y)))))
return BinaryOperator::CreateFMulFMF(Builder.CreateFNegFMF(X, &I), Y, &I);
if (match(FNeg, m_OneUse(m_FDiv(m_Value(X), m_Value(Y)))))
return BinaryOperator::CreateFDivFMF(Builder.CreateFNegFMF(X, &I), Y, &I);
return nullptr;
}
Instruction *InstCombiner::visitFNeg(UnaryOperator &I) {
Value *Op = I.getOperand(0);
if (Value *V = SimplifyFNegInst(Op, I.getFastMathFlags(),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldFNegIntoConstant(I))
return X;
Value *X, *Y;
// If we can ignore the sign of zeros: -(X - Y) --> (Y - X)
if (I.hasNoSignedZeros() &&
match(Op, m_OneUse(m_FSub(m_Value(X), m_Value(Y)))))
return BinaryOperator::CreateFSubFMF(Y, X, &I);
if (Instruction *R = hoistFNegAboveFMulFDiv(I, Builder))
return R;
return nullptr;
}
Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
if (Value *V = SimplifyFSubInst(I.getOperand(0), I.getOperand(1),
I.getFastMathFlags(),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldVectorBinop(I))
return X;
// Subtraction from -0.0 is the canonical form of fneg.
// fsub nsz 0, X ==> fsub nsz -0.0, X
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (I.hasNoSignedZeros() && match(Op0, m_PosZeroFP()))
return BinaryOperator::CreateFNegFMF(Op1, &I);
if (Instruction *X = foldFNegIntoConstant(I))
return X;
if (Instruction *R = hoistFNegAboveFMulFDiv(I, Builder))
return R;
Value *X, *Y;
Constant *C;
// If Op0 is not -0.0 or we can ignore -0.0: Z - (X - Y) --> Z + (Y - X)
// Canonicalize to fadd to make analysis easier.
// This can also help codegen because fadd is commutative.
// Note that if this fsub was really an fneg, the fadd with -0.0 will get
// killed later. We still limit that particular transform with 'hasOneUse'
// because an fneg is assumed better/cheaper than a generic fsub.
if (I.hasNoSignedZeros() || CannotBeNegativeZero(Op0, SQ.TLI)) {
if (match(Op1, m_OneUse(m_FSub(m_Value(X), m_Value(Y))))) {
Value *NewSub = Builder.CreateFSubFMF(Y, X, &I);
return BinaryOperator::CreateFAddFMF(Op0, NewSub, &I);
}
}
if (isa<Constant>(Op0))
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *NV = FoldOpIntoSelect(I, SI))
return NV;
// X - C --> X + (-C)
// But don't transform constant expressions because there's an inverse fold
// for X + (-Y) --> X - Y.
if (match(Op1, m_Constant(C)) && !isa<ConstantExpr>(Op1))
return BinaryOperator::CreateFAddFMF(Op0, ConstantExpr::getFNeg(C), &I);
// X - (-Y) --> X + Y
if (match(Op1, m_FNeg(m_Value(Y))))
return BinaryOperator::CreateFAddFMF(Op0, Y, &I);
// Similar to above, but look through a cast of the negated value:
// X - (fptrunc(-Y)) --> X + fptrunc(Y)
Type *Ty = I.getType();
if (match(Op1, m_OneUse(m_FPTrunc(m_FNeg(m_Value(Y))))))
return BinaryOperator::CreateFAddFMF(Op0, Builder.CreateFPTrunc(Y, Ty), &I);
// X - (fpext(-Y)) --> X + fpext(Y)
if (match(Op1, m_OneUse(m_FPExt(m_FNeg(m_Value(Y))))))
return BinaryOperator::CreateFAddFMF(Op0, Builder.CreateFPExt(Y, Ty), &I);
// Similar to above, but look through fmul/fdiv of the negated value:
// Op0 - (-X * Y) --> Op0 + (X * Y)
// Op0 - (Y * -X) --> Op0 + (X * Y)
if (match(Op1, m_OneUse(m_c_FMul(m_FNeg(m_Value(X)), m_Value(Y))))) {
Value *FMul = Builder.CreateFMulFMF(X, Y, &I);
return BinaryOperator::CreateFAddFMF(Op0, FMul, &I);
}
// Op0 - (-X / Y) --> Op0 + (X / Y)
// Op0 - (X / -Y) --> Op0 + (X / Y)
if (match(Op1, m_OneUse(m_FDiv(m_FNeg(m_Value(X)), m_Value(Y)))) ||
match(Op1, m_OneUse(m_FDiv(m_Value(X), m_FNeg(m_Value(Y)))))) {
Value *FDiv = Builder.CreateFDivFMF(X, Y, &I);
return BinaryOperator::CreateFAddFMF(Op0, FDiv, &I);
}
// Handle special cases for FSub with selects feeding the operation
if (Value *V = SimplifySelectsFeedingBinaryOp(I, Op0, Op1))
return replaceInstUsesWith(I, V);
if (I.hasAllowReassoc() && I.hasNoSignedZeros()) {
// (Y - X) - Y --> -X
if (match(Op0, m_FSub(m_Specific(Op1), m_Value(X))))
return BinaryOperator::CreateFNegFMF(X, &I);
// Y - (X + Y) --> -X
// Y - (Y + X) --> -X
if (match(Op1, m_c_FAdd(m_Specific(Op0), m_Value(X))))
return BinaryOperator::CreateFNegFMF(X, &I);
// (X * C) - X --> X * (C - 1.0)
if (match(Op0, m_FMul(m_Specific(Op1), m_Constant(C)))) {
Constant *CSubOne = ConstantExpr::getFSub(C, ConstantFP::get(Ty, 1.0));
return BinaryOperator::CreateFMulFMF(Op1, CSubOne, &I);
}
// X - (X * C) --> X * (1.0 - C)
if (match(Op1, m_FMul(m_Specific(Op0), m_Constant(C)))) {
Constant *OneSubC = ConstantExpr::getFSub(ConstantFP::get(Ty, 1.0), C);
return BinaryOperator::CreateFMulFMF(Op0, OneSubC, &I);
}
if (Instruction *F = factorizeFAddFSub(I, Builder))
return F;
// TODO: This performs reassociative folds for FP ops. Some fraction of the
// functionality has been subsumed by simple pattern matching here and in
// InstSimplify. We should let a dedicated reassociation pass handle more
// complex pattern matching and remove this from InstCombine.
if (Value *V = FAddCombine(Builder).simplify(&I))
return replaceInstUsesWith(I, V);
}
return nullptr;
}