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InstCombineAndOrXor.cpp
2644 lines (2328 loc) · 101 KB
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InstCombineAndOrXor.cpp
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//===- InstCombineAndOrXor.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 visitAnd, visitOr, and visitXor functions.
//
//===----------------------------------------------------------------------===//
#include "InstCombineInternal.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Transforms/Utils/CmpInstAnalysis.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
using namespace PatternMatch;
#define DEBUG_TYPE "instcombine"
/// Similar to getICmpCode but for FCmpInst. This encodes a fcmp predicate into
/// a four bit mask.
static unsigned getFCmpCode(FCmpInst::Predicate CC) {
assert(FCmpInst::FCMP_FALSE <= CC && CC <= FCmpInst::FCMP_TRUE &&
"Unexpected FCmp predicate!");
// Take advantage of the bit pattern of FCmpInst::Predicate here.
// U L G E
static_assert(FCmpInst::FCMP_FALSE == 0, ""); // 0 0 0 0
static_assert(FCmpInst::FCMP_OEQ == 1, ""); // 0 0 0 1
static_assert(FCmpInst::FCMP_OGT == 2, ""); // 0 0 1 0
static_assert(FCmpInst::FCMP_OGE == 3, ""); // 0 0 1 1
static_assert(FCmpInst::FCMP_OLT == 4, ""); // 0 1 0 0
static_assert(FCmpInst::FCMP_OLE == 5, ""); // 0 1 0 1
static_assert(FCmpInst::FCMP_ONE == 6, ""); // 0 1 1 0
static_assert(FCmpInst::FCMP_ORD == 7, ""); // 0 1 1 1
static_assert(FCmpInst::FCMP_UNO == 8, ""); // 1 0 0 0
static_assert(FCmpInst::FCMP_UEQ == 9, ""); // 1 0 0 1
static_assert(FCmpInst::FCMP_UGT == 10, ""); // 1 0 1 0
static_assert(FCmpInst::FCMP_UGE == 11, ""); // 1 0 1 1
static_assert(FCmpInst::FCMP_ULT == 12, ""); // 1 1 0 0
static_assert(FCmpInst::FCMP_ULE == 13, ""); // 1 1 0 1
static_assert(FCmpInst::FCMP_UNE == 14, ""); // 1 1 1 0
static_assert(FCmpInst::FCMP_TRUE == 15, ""); // 1 1 1 1
return CC;
}
/// This is the complement of getICmpCode, which turns an opcode and two
/// operands into either a constant true or false, or a brand new ICmp
/// instruction. The sign is passed in to determine which kind of predicate to
/// use in the new icmp instruction.
static Value *getNewICmpValue(bool Sign, unsigned Code, Value *LHS, Value *RHS,
InstCombiner::BuilderTy *Builder) {
ICmpInst::Predicate NewPred;
if (Value *NewConstant = getICmpValue(Sign, Code, LHS, RHS, NewPred))
return NewConstant;
return Builder->CreateICmp(NewPred, LHS, RHS);
}
/// This is the complement of getFCmpCode, which turns an opcode and two
/// operands into either a FCmp instruction, or a true/false constant.
static Value *getFCmpValue(unsigned Code, Value *LHS, Value *RHS,
InstCombiner::BuilderTy *Builder) {
const auto Pred = static_cast<FCmpInst::Predicate>(Code);
assert(FCmpInst::FCMP_FALSE <= Pred && Pred <= FCmpInst::FCMP_TRUE &&
"Unexpected FCmp predicate!");
if (Pred == FCmpInst::FCMP_FALSE)
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);
if (Pred == FCmpInst::FCMP_TRUE)
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 1);
return Builder->CreateFCmp(Pred, LHS, RHS);
}
/// \brief Transform BITWISE_OP(BSWAP(A),BSWAP(B)) to BSWAP(BITWISE_OP(A, B))
/// \param I Binary operator to transform.
/// \return Pointer to node that must replace the original binary operator, or
/// null pointer if no transformation was made.
Value *InstCombiner::SimplifyBSwap(BinaryOperator &I) {
assert(I.isBitwiseLogicOp() && "Unexpected opcode for bswap simplifying");
Value *OldLHS = I.getOperand(0);
Value *OldRHS = I.getOperand(1);
Value *NewLHS;
if (!match(OldLHS, m_BSwap(m_Value(NewLHS))))
return nullptr;
Value *NewRHS;
const APInt *C;
if (match(OldRHS, m_BSwap(m_Value(NewRHS)))) {
// OP( BSWAP(x), BSWAP(y) ) -> BSWAP( OP(x, y) )
if (!OldLHS->hasOneUse() && !OldRHS->hasOneUse())
return nullptr;
// NewRHS initialized by the matcher.
} else if (match(OldRHS, m_APInt(C))) {
// OP( BSWAP(x), CONSTANT ) -> BSWAP( OP(x, BSWAP(CONSTANT) ) )
if (!OldLHS->hasOneUse())
return nullptr;
NewRHS = ConstantInt::get(I.getType(), C->byteSwap());
} else
return nullptr;
Value *BinOp = Builder->CreateBinOp(I.getOpcode(), NewLHS, NewRHS);
Function *F = Intrinsic::getDeclaration(I.getModule(), Intrinsic::bswap,
I.getType());
return Builder->CreateCall(F, BinOp);
}
/// This handles expressions of the form ((val OP C1) & C2). Where
/// the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'.
Instruction *InstCombiner::OptAndOp(BinaryOperator *Op,
ConstantInt *OpRHS,
ConstantInt *AndRHS,
BinaryOperator &TheAnd) {
Value *X = Op->getOperand(0);
Constant *Together = nullptr;
if (!Op->isShift())
Together = ConstantExpr::getAnd(AndRHS, OpRHS);
switch (Op->getOpcode()) {
default: break;
case Instruction::Xor:
if (Op->hasOneUse()) {
// (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
Value *And = Builder->CreateAnd(X, AndRHS);
And->takeName(Op);
return BinaryOperator::CreateXor(And, Together);
}
break;
case Instruction::Or:
if (Op->hasOneUse()){
ConstantInt *TogetherCI = dyn_cast<ConstantInt>(Together);
if (TogetherCI && !TogetherCI->isZero()){
// (X | C1) & C2 --> (X & (C2^(C1&C2))) | C1
// NOTE: This reduces the number of bits set in the & mask, which
// can expose opportunities for store narrowing.
Together = ConstantExpr::getXor(AndRHS, Together);
Value *And = Builder->CreateAnd(X, Together);
And->takeName(Op);
return BinaryOperator::CreateOr(And, OpRHS);
}
}
break;
case Instruction::Add:
if (Op->hasOneUse()) {
// Adding a one to a single bit bit-field should be turned into an XOR
// of the bit. First thing to check is to see if this AND is with a
// single bit constant.
const APInt &AndRHSV = AndRHS->getValue();
// If there is only one bit set.
if (AndRHSV.isPowerOf2()) {
// Ok, at this point, we know that we are masking the result of the
// ADD down to exactly one bit. If the constant we are adding has
// no bits set below this bit, then we can eliminate the ADD.
const APInt& AddRHS = OpRHS->getValue();
// Check to see if any bits below the one bit set in AndRHSV are set.
if ((AddRHS & (AndRHSV - 1)).isNullValue()) {
// If not, the only thing that can effect the output of the AND is
// the bit specified by AndRHSV. If that bit is set, the effect of
// the XOR is to toggle the bit. If it is clear, then the ADD has
// no effect.
if ((AddRHS & AndRHSV).isNullValue()) { // Bit is not set, noop
TheAnd.setOperand(0, X);
return &TheAnd;
} else {
// Pull the XOR out of the AND.
Value *NewAnd = Builder->CreateAnd(X, AndRHS);
NewAnd->takeName(Op);
return BinaryOperator::CreateXor(NewAnd, AndRHS);
}
}
}
}
break;
case Instruction::Shl: {
// We know that the AND will not produce any of the bits shifted in, so if
// the anded constant includes them, clear them now!
//
uint32_t BitWidth = AndRHS->getType()->getBitWidth();
uint32_t OpRHSVal = OpRHS->getLimitedValue(BitWidth);
APInt ShlMask(APInt::getHighBitsSet(BitWidth, BitWidth-OpRHSVal));
ConstantInt *CI = Builder->getInt(AndRHS->getValue() & ShlMask);
if (CI->getValue() == ShlMask)
// Masking out bits that the shift already masks.
return replaceInstUsesWith(TheAnd, Op); // No need for the and.
if (CI != AndRHS) { // Reducing bits set in and.
TheAnd.setOperand(1, CI);
return &TheAnd;
}
break;
}
case Instruction::LShr: {
// We know that the AND will not produce any of the bits shifted in, so if
// the anded constant includes them, clear them now! This only applies to
// unsigned shifts, because a signed shr may bring in set bits!
//
uint32_t BitWidth = AndRHS->getType()->getBitWidth();
uint32_t OpRHSVal = OpRHS->getLimitedValue(BitWidth);
APInt ShrMask(APInt::getLowBitsSet(BitWidth, BitWidth - OpRHSVal));
ConstantInt *CI = Builder->getInt(AndRHS->getValue() & ShrMask);
if (CI->getValue() == ShrMask)
// Masking out bits that the shift already masks.
return replaceInstUsesWith(TheAnd, Op);
if (CI != AndRHS) {
TheAnd.setOperand(1, CI); // Reduce bits set in and cst.
return &TheAnd;
}
break;
}
case Instruction::AShr:
// Signed shr.
// See if this is shifting in some sign extension, then masking it out
// with an and.
if (Op->hasOneUse()) {
uint32_t BitWidth = AndRHS->getType()->getBitWidth();
uint32_t OpRHSVal = OpRHS->getLimitedValue(BitWidth);
APInt ShrMask(APInt::getLowBitsSet(BitWidth, BitWidth - OpRHSVal));
Constant *C = Builder->getInt(AndRHS->getValue() & ShrMask);
if (C == AndRHS) { // Masking out bits shifted in.
// (Val ashr C1) & C2 -> (Val lshr C1) & C2
// Make the argument unsigned.
Value *ShVal = Op->getOperand(0);
ShVal = Builder->CreateLShr(ShVal, OpRHS, Op->getName());
return BinaryOperator::CreateAnd(ShVal, AndRHS, TheAnd.getName());
}
}
break;
}
return nullptr;
}
/// Emit a computation of: (V >= Lo && V < Hi) if Inside is true, otherwise
/// (V < Lo || V >= Hi). This method expects that Lo <= Hi. IsSigned indicates
/// whether to treat V, Lo, and Hi as signed or not.
Value *InstCombiner::insertRangeTest(Value *V, const APInt &Lo, const APInt &Hi,
bool isSigned, bool Inside) {
assert((isSigned ? Lo.sle(Hi) : Lo.ule(Hi)) &&
"Lo is not <= Hi in range emission code!");
Type *Ty = V->getType();
if (Lo == Hi)
return Inside ? ConstantInt::getFalse(Ty) : ConstantInt::getTrue(Ty);
// V >= Min && V < Hi --> V < Hi
// V < Min || V >= Hi --> V >= Hi
ICmpInst::Predicate Pred = Inside ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_UGE;
if (isSigned ? Lo.isMinSignedValue() : Lo.isMinValue()) {
Pred = isSigned ? ICmpInst::getSignedPredicate(Pred) : Pred;
return Builder->CreateICmp(Pred, V, ConstantInt::get(Ty, Hi));
}
// V >= Lo && V < Hi --> V - Lo u< Hi - Lo
// V < Lo || V >= Hi --> V - Lo u>= Hi - Lo
Value *VMinusLo =
Builder->CreateSub(V, ConstantInt::get(Ty, Lo), V->getName() + ".off");
Constant *HiMinusLo = ConstantInt::get(Ty, Hi - Lo);
return Builder->CreateICmp(Pred, VMinusLo, HiMinusLo);
}
/// Classify (icmp eq (A & B), C) and (icmp ne (A & B), C) as matching patterns
/// that can be simplified.
/// One of A and B is considered the mask. The other is the value. This is
/// described as the "AMask" or "BMask" part of the enum. If the enum contains
/// only "Mask", then both A and B can be considered masks. If A is the mask,
/// then it was proven that (A & C) == C. This is trivial if C == A or C == 0.
/// If both A and C are constants, this proof is also easy.
/// For the following explanations, we assume that A is the mask.
///
/// "AllOnes" declares that the comparison is true only if (A & B) == A or all
/// bits of A are set in B.
/// Example: (icmp eq (A & 3), 3) -> AMask_AllOnes
///
/// "AllZeros" declares that the comparison is true only if (A & B) == 0 or all
/// bits of A are cleared in B.
/// Example: (icmp eq (A & 3), 0) -> Mask_AllZeroes
///
/// "Mixed" declares that (A & B) == C and C might or might not contain any
/// number of one bits and zero bits.
/// Example: (icmp eq (A & 3), 1) -> AMask_Mixed
///
/// "Not" means that in above descriptions "==" should be replaced by "!=".
/// Example: (icmp ne (A & 3), 3) -> AMask_NotAllOnes
///
/// If the mask A contains a single bit, then the following is equivalent:
/// (icmp eq (A & B), A) equals (icmp ne (A & B), 0)
/// (icmp ne (A & B), A) equals (icmp eq (A & B), 0)
enum MaskedICmpType {
AMask_AllOnes = 1,
AMask_NotAllOnes = 2,
BMask_AllOnes = 4,
BMask_NotAllOnes = 8,
Mask_AllZeros = 16,
Mask_NotAllZeros = 32,
AMask_Mixed = 64,
AMask_NotMixed = 128,
BMask_Mixed = 256,
BMask_NotMixed = 512
};
/// Return the set of patterns (from MaskedICmpType) that (icmp SCC (A & B), C)
/// satisfies.
static unsigned getMaskedICmpType(Value *A, Value *B, Value *C,
ICmpInst::Predicate Pred) {
ConstantInt *ACst = dyn_cast<ConstantInt>(A);
ConstantInt *BCst = dyn_cast<ConstantInt>(B);
ConstantInt *CCst = dyn_cast<ConstantInt>(C);
bool IsEq = (Pred == ICmpInst::ICMP_EQ);
bool IsAPow2 = (ACst && !ACst->isZero() && ACst->getValue().isPowerOf2());
bool IsBPow2 = (BCst && !BCst->isZero() && BCst->getValue().isPowerOf2());
unsigned MaskVal = 0;
if (CCst && CCst->isZero()) {
// if C is zero, then both A and B qualify as mask
MaskVal |= (IsEq ? (Mask_AllZeros | AMask_Mixed | BMask_Mixed)
: (Mask_NotAllZeros | AMask_NotMixed | BMask_NotMixed));
if (IsAPow2)
MaskVal |= (IsEq ? (AMask_NotAllOnes | AMask_NotMixed)
: (AMask_AllOnes | AMask_Mixed));
if (IsBPow2)
MaskVal |= (IsEq ? (BMask_NotAllOnes | BMask_NotMixed)
: (BMask_AllOnes | BMask_Mixed));
return MaskVal;
}
if (A == C) {
MaskVal |= (IsEq ? (AMask_AllOnes | AMask_Mixed)
: (AMask_NotAllOnes | AMask_NotMixed));
if (IsAPow2)
MaskVal |= (IsEq ? (Mask_NotAllZeros | AMask_NotMixed)
: (Mask_AllZeros | AMask_Mixed));
} else if (ACst && CCst && ConstantExpr::getAnd(ACst, CCst) == CCst) {
MaskVal |= (IsEq ? AMask_Mixed : AMask_NotMixed);
}
if (B == C) {
MaskVal |= (IsEq ? (BMask_AllOnes | BMask_Mixed)
: (BMask_NotAllOnes | BMask_NotMixed));
if (IsBPow2)
MaskVal |= (IsEq ? (Mask_NotAllZeros | BMask_NotMixed)
: (Mask_AllZeros | BMask_Mixed));
} else if (BCst && CCst && ConstantExpr::getAnd(BCst, CCst) == CCst) {
MaskVal |= (IsEq ? BMask_Mixed : BMask_NotMixed);
}
return MaskVal;
}
/// Convert an analysis of a masked ICmp into its equivalent if all boolean
/// operations had the opposite sense. Since each "NotXXX" flag (recording !=)
/// is adjacent to the corresponding normal flag (recording ==), this just
/// involves swapping those bits over.
static unsigned conjugateICmpMask(unsigned Mask) {
unsigned NewMask;
NewMask = (Mask & (AMask_AllOnes | BMask_AllOnes | Mask_AllZeros |
AMask_Mixed | BMask_Mixed))
<< 1;
NewMask |= (Mask & (AMask_NotAllOnes | BMask_NotAllOnes | Mask_NotAllZeros |
AMask_NotMixed | BMask_NotMixed))
>> 1;
return NewMask;
}
/// Handle (icmp(A & B) ==/!= C) &/| (icmp(A & D) ==/!= E).
/// Return the set of pattern classes (from MaskedICmpType) that both LHS and
/// RHS satisfy.
static unsigned getMaskedTypeForICmpPair(Value *&A, Value *&B, Value *&C,
Value *&D, Value *&E, ICmpInst *LHS,
ICmpInst *RHS,
ICmpInst::Predicate &PredL,
ICmpInst::Predicate &PredR) {
if (LHS->getOperand(0)->getType() != RHS->getOperand(0)->getType())
return 0;
// vectors are not (yet?) supported
if (LHS->getOperand(0)->getType()->isVectorTy())
return 0;
// Here comes the tricky part:
// LHS might be of the form L11 & L12 == X, X == L21 & L22,
// and L11 & L12 == L21 & L22. The same goes for RHS.
// Now we must find those components L** and R**, that are equal, so
// that we can extract the parameters A, B, C, D, and E for the canonical
// above.
Value *L1 = LHS->getOperand(0);
Value *L2 = LHS->getOperand(1);
Value *L11, *L12, *L21, *L22;
// Check whether the icmp can be decomposed into a bit test.
if (decomposeBitTestICmp(LHS, PredL, L11, L12, L2)) {
L21 = L22 = L1 = nullptr;
} else {
// Look for ANDs in the LHS icmp.
if (!L1->getType()->isIntegerTy()) {
// You can icmp pointers, for example. They really aren't masks.
L11 = L12 = nullptr;
} else if (!match(L1, m_And(m_Value(L11), m_Value(L12)))) {
// Any icmp can be viewed as being trivially masked; if it allows us to
// remove one, it's worth it.
L11 = L1;
L12 = Constant::getAllOnesValue(L1->getType());
}
if (!L2->getType()->isIntegerTy()) {
// You can icmp pointers, for example. They really aren't masks.
L21 = L22 = nullptr;
} else if (!match(L2, m_And(m_Value(L21), m_Value(L22)))) {
L21 = L2;
L22 = Constant::getAllOnesValue(L2->getType());
}
}
// Bail if LHS was a icmp that can't be decomposed into an equality.
if (!ICmpInst::isEquality(PredL))
return 0;
Value *R1 = RHS->getOperand(0);
Value *R2 = RHS->getOperand(1);
Value *R11, *R12;
bool Ok = false;
if (decomposeBitTestICmp(RHS, PredR, R11, R12, R2)) {
if (R11 == L11 || R11 == L12 || R11 == L21 || R11 == L22) {
A = R11;
D = R12;
} else if (R12 == L11 || R12 == L12 || R12 == L21 || R12 == L22) {
A = R12;
D = R11;
} else {
return 0;
}
E = R2;
R1 = nullptr;
Ok = true;
} else if (R1->getType()->isIntegerTy()) {
if (!match(R1, m_And(m_Value(R11), m_Value(R12)))) {
// As before, model no mask as a trivial mask if it'll let us do an
// optimization.
R11 = R1;
R12 = Constant::getAllOnesValue(R1->getType());
}
if (R11 == L11 || R11 == L12 || R11 == L21 || R11 == L22) {
A = R11;
D = R12;
E = R2;
Ok = true;
} else if (R12 == L11 || R12 == L12 || R12 == L21 || R12 == L22) {
A = R12;
D = R11;
E = R2;
Ok = true;
}
}
// Bail if RHS was a icmp that can't be decomposed into an equality.
if (!ICmpInst::isEquality(PredR))
return 0;
// Look for ANDs on the right side of the RHS icmp.
if (!Ok && R2->getType()->isIntegerTy()) {
if (!match(R2, m_And(m_Value(R11), m_Value(R12)))) {
R11 = R2;
R12 = Constant::getAllOnesValue(R2->getType());
}
if (R11 == L11 || R11 == L12 || R11 == L21 || R11 == L22) {
A = R11;
D = R12;
E = R1;
Ok = true;
} else if (R12 == L11 || R12 == L12 || R12 == L21 || R12 == L22) {
A = R12;
D = R11;
E = R1;
Ok = true;
} else {
return 0;
}
}
if (!Ok)
return 0;
if (L11 == A) {
B = L12;
C = L2;
} else if (L12 == A) {
B = L11;
C = L2;
} else if (L21 == A) {
B = L22;
C = L1;
} else if (L22 == A) {
B = L21;
C = L1;
}
unsigned LeftType = getMaskedICmpType(A, B, C, PredL);
unsigned RightType = getMaskedICmpType(A, D, E, PredR);
return LeftType & RightType;
}
/// Try to fold (icmp(A & B) ==/!= C) &/| (icmp(A & D) ==/!= E)
/// into a single (icmp(A & X) ==/!= Y).
static Value *foldLogOpOfMaskedICmps(ICmpInst *LHS, ICmpInst *RHS, bool IsAnd,
llvm::InstCombiner::BuilderTy *Builder) {
Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr, *E = nullptr;
ICmpInst::Predicate PredL = LHS->getPredicate(), PredR = RHS->getPredicate();
unsigned Mask =
getMaskedTypeForICmpPair(A, B, C, D, E, LHS, RHS, PredL, PredR);
if (Mask == 0)
return nullptr;
assert(ICmpInst::isEquality(PredL) && ICmpInst::isEquality(PredR) &&
"Expected equality predicates for masked type of icmps.");
// In full generality:
// (icmp (A & B) Op C) | (icmp (A & D) Op E)
// == ![ (icmp (A & B) !Op C) & (icmp (A & D) !Op E) ]
//
// If the latter can be converted into (icmp (A & X) Op Y) then the former is
// equivalent to (icmp (A & X) !Op Y).
//
// Therefore, we can pretend for the rest of this function that we're dealing
// with the conjunction, provided we flip the sense of any comparisons (both
// input and output).
// In most cases we're going to produce an EQ for the "&&" case.
ICmpInst::Predicate NewCC = IsAnd ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE;
if (!IsAnd) {
// Convert the masking analysis into its equivalent with negated
// comparisons.
Mask = conjugateICmpMask(Mask);
}
if (Mask & Mask_AllZeros) {
// (icmp eq (A & B), 0) & (icmp eq (A & D), 0)
// -> (icmp eq (A & (B|D)), 0)
Value *NewOr = Builder->CreateOr(B, D);
Value *NewAnd = Builder->CreateAnd(A, NewOr);
// We can't use C as zero because we might actually handle
// (icmp ne (A & B), B) & (icmp ne (A & D), D)
// with B and D, having a single bit set.
Value *Zero = Constant::getNullValue(A->getType());
return Builder->CreateICmp(NewCC, NewAnd, Zero);
}
if (Mask & BMask_AllOnes) {
// (icmp eq (A & B), B) & (icmp eq (A & D), D)
// -> (icmp eq (A & (B|D)), (B|D))
Value *NewOr = Builder->CreateOr(B, D);
Value *NewAnd = Builder->CreateAnd(A, NewOr);
return Builder->CreateICmp(NewCC, NewAnd, NewOr);
}
if (Mask & AMask_AllOnes) {
// (icmp eq (A & B), A) & (icmp eq (A & D), A)
// -> (icmp eq (A & (B&D)), A)
Value *NewAnd1 = Builder->CreateAnd(B, D);
Value *NewAnd2 = Builder->CreateAnd(A, NewAnd1);
return Builder->CreateICmp(NewCC, NewAnd2, A);
}
// Remaining cases assume at least that B and D are constant, and depend on
// their actual values. This isn't strictly necessary, just a "handle the
// easy cases for now" decision.
ConstantInt *BCst = dyn_cast<ConstantInt>(B);
if (!BCst)
return nullptr;
ConstantInt *DCst = dyn_cast<ConstantInt>(D);
if (!DCst)
return nullptr;
if (Mask & (Mask_NotAllZeros | BMask_NotAllOnes)) {
// (icmp ne (A & B), 0) & (icmp ne (A & D), 0) and
// (icmp ne (A & B), B) & (icmp ne (A & D), D)
// -> (icmp ne (A & B), 0) or (icmp ne (A & D), 0)
// Only valid if one of the masks is a superset of the other (check "B&D" is
// the same as either B or D).
APInt NewMask = BCst->getValue() & DCst->getValue();
if (NewMask == BCst->getValue())
return LHS;
else if (NewMask == DCst->getValue())
return RHS;
}
if (Mask & AMask_NotAllOnes) {
// (icmp ne (A & B), B) & (icmp ne (A & D), D)
// -> (icmp ne (A & B), A) or (icmp ne (A & D), A)
// Only valid if one of the masks is a superset of the other (check "B|D" is
// the same as either B or D).
APInt NewMask = BCst->getValue() | DCst->getValue();
if (NewMask == BCst->getValue())
return LHS;
else if (NewMask == DCst->getValue())
return RHS;
}
if (Mask & BMask_Mixed) {
// (icmp eq (A & B), C) & (icmp eq (A & D), E)
// We already know that B & C == C && D & E == E.
// If we can prove that (B & D) & (C ^ E) == 0, that is, the bits of
// C and E, which are shared by both the mask B and the mask D, don't
// contradict, then we can transform to
// -> (icmp eq (A & (B|D)), (C|E))
// Currently, we only handle the case of B, C, D, and E being constant.
// We can't simply use C and E because we might actually handle
// (icmp ne (A & B), B) & (icmp eq (A & D), D)
// with B and D, having a single bit set.
ConstantInt *CCst = dyn_cast<ConstantInt>(C);
if (!CCst)
return nullptr;
ConstantInt *ECst = dyn_cast<ConstantInt>(E);
if (!ECst)
return nullptr;
if (PredL != NewCC)
CCst = cast<ConstantInt>(ConstantExpr::getXor(BCst, CCst));
if (PredR != NewCC)
ECst = cast<ConstantInt>(ConstantExpr::getXor(DCst, ECst));
// If there is a conflict, we should actually return a false for the
// whole construct.
if (((BCst->getValue() & DCst->getValue()) &
(CCst->getValue() ^ ECst->getValue())).getBoolValue())
return ConstantInt::get(LHS->getType(), !IsAnd);
Value *NewOr1 = Builder->CreateOr(B, D);
Value *NewOr2 = ConstantExpr::getOr(CCst, ECst);
Value *NewAnd = Builder->CreateAnd(A, NewOr1);
return Builder->CreateICmp(NewCC, NewAnd, NewOr2);
}
return nullptr;
}
/// Try to fold a signed range checked with lower bound 0 to an unsigned icmp.
/// Example: (icmp sge x, 0) & (icmp slt x, n) --> icmp ult x, n
/// If \p Inverted is true then the check is for the inverted range, e.g.
/// (icmp slt x, 0) | (icmp sgt x, n) --> icmp ugt x, n
Value *InstCombiner::simplifyRangeCheck(ICmpInst *Cmp0, ICmpInst *Cmp1,
bool Inverted) {
// Check the lower range comparison, e.g. x >= 0
// InstCombine already ensured that if there is a constant it's on the RHS.
ConstantInt *RangeStart = dyn_cast<ConstantInt>(Cmp0->getOperand(1));
if (!RangeStart)
return nullptr;
ICmpInst::Predicate Pred0 = (Inverted ? Cmp0->getInversePredicate() :
Cmp0->getPredicate());
// Accept x > -1 or x >= 0 (after potentially inverting the predicate).
if (!((Pred0 == ICmpInst::ICMP_SGT && RangeStart->isMinusOne()) ||
(Pred0 == ICmpInst::ICMP_SGE && RangeStart->isZero())))
return nullptr;
ICmpInst::Predicate Pred1 = (Inverted ? Cmp1->getInversePredicate() :
Cmp1->getPredicate());
Value *Input = Cmp0->getOperand(0);
Value *RangeEnd;
if (Cmp1->getOperand(0) == Input) {
// For the upper range compare we have: icmp x, n
RangeEnd = Cmp1->getOperand(1);
} else if (Cmp1->getOperand(1) == Input) {
// For the upper range compare we have: icmp n, x
RangeEnd = Cmp1->getOperand(0);
Pred1 = ICmpInst::getSwappedPredicate(Pred1);
} else {
return nullptr;
}
// Check the upper range comparison, e.g. x < n
ICmpInst::Predicate NewPred;
switch (Pred1) {
case ICmpInst::ICMP_SLT: NewPred = ICmpInst::ICMP_ULT; break;
case ICmpInst::ICMP_SLE: NewPred = ICmpInst::ICMP_ULE; break;
default: return nullptr;
}
// This simplification is only valid if the upper range is not negative.
KnownBits Known = computeKnownBits(RangeEnd, /*Depth=*/0, Cmp1);
if (!Known.isNonNegative())
return nullptr;
if (Inverted)
NewPred = ICmpInst::getInversePredicate(NewPred);
return Builder->CreateICmp(NewPred, Input, RangeEnd);
}
static Value *
foldAndOrOfEqualityCmpsWithConstants(ICmpInst *LHS, ICmpInst *RHS,
bool JoinedByAnd,
InstCombiner::BuilderTy *Builder) {
Value *X = LHS->getOperand(0);
if (X != RHS->getOperand(0))
return nullptr;
const APInt *C1, *C2;
if (!match(LHS->getOperand(1), m_APInt(C1)) ||
!match(RHS->getOperand(1), m_APInt(C2)))
return nullptr;
// We only handle (X != C1 && X != C2) and (X == C1 || X == C2).
ICmpInst::Predicate Pred = LHS->getPredicate();
if (Pred != RHS->getPredicate())
return nullptr;
if (JoinedByAnd && Pred != ICmpInst::ICMP_NE)
return nullptr;
if (!JoinedByAnd && Pred != ICmpInst::ICMP_EQ)
return nullptr;
// The larger unsigned constant goes on the right.
if (C1->ugt(*C2))
std::swap(C1, C2);
APInt Xor = *C1 ^ *C2;
if (Xor.isPowerOf2()) {
// If LHSC and RHSC differ by only one bit, then set that bit in X and
// compare against the larger constant:
// (X == C1 || X == C2) --> (X | (C1 ^ C2)) == C2
// (X != C1 && X != C2) --> (X | (C1 ^ C2)) != C2
// We choose an 'or' with a Pow2 constant rather than the inverse mask with
// 'and' because that may lead to smaller codegen from a smaller constant.
Value *Or = Builder->CreateOr(X, ConstantInt::get(X->getType(), Xor));
return Builder->CreateICmp(Pred, Or, ConstantInt::get(X->getType(), *C2));
}
// Special case: get the ordering right when the values wrap around zero.
// Ie, we assumed the constants were unsigned when swapping earlier.
if (C1->isNullValue() && C2->isAllOnesValue())
std::swap(C1, C2);
if (*C1 == *C2 - 1) {
// (X == 13 || X == 14) --> X - 13 <=u 1
// (X != 13 && X != 14) --> X - 13 >u 1
// An 'add' is the canonical IR form, so favor that over a 'sub'.
Value *Add = Builder->CreateAdd(X, ConstantInt::get(X->getType(), -(*C1)));
auto NewPred = JoinedByAnd ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_ULE;
return Builder->CreateICmp(NewPred, Add, ConstantInt::get(X->getType(), 1));
}
return nullptr;
}
// Fold (iszero(A & K1) | iszero(A & K2)) -> (A & (K1 | K2)) != (K1 | K2)
// Fold (!iszero(A & K1) & !iszero(A & K2)) -> (A & (K1 | K2)) == (K1 | K2)
Value *InstCombiner::foldAndOrOfICmpsOfAndWithPow2(ICmpInst *LHS, ICmpInst *RHS,
bool JoinedByAnd,
Instruction &CxtI) {
ICmpInst::Predicate Pred = LHS->getPredicate();
if (Pred != RHS->getPredicate())
return nullptr;
if (JoinedByAnd && Pred != ICmpInst::ICMP_NE)
return nullptr;
if (!JoinedByAnd && Pred != ICmpInst::ICMP_EQ)
return nullptr;
// TODO support vector splats
ConstantInt *LHSC = dyn_cast<ConstantInt>(LHS->getOperand(1));
ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS->getOperand(1));
if (!LHSC || !RHSC || !LHSC->isZero() || !RHSC->isZero())
return nullptr;
Value *A, *B, *C, *D;
if (match(LHS->getOperand(0), m_And(m_Value(A), m_Value(B))) &&
match(RHS->getOperand(0), m_And(m_Value(C), m_Value(D)))) {
if (A == D || B == D)
std::swap(C, D);
if (B == C)
std::swap(A, B);
if (A == C &&
isKnownToBeAPowerOfTwo(B, false, 0, &CxtI) &&
isKnownToBeAPowerOfTwo(D, false, 0, &CxtI)) {
Value *Mask = Builder->CreateOr(B, D);
Value *Masked = Builder->CreateAnd(A, Mask);
auto NewPred = JoinedByAnd ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE;
return Builder->CreateICmp(NewPred, Masked, Mask);
}
}
return nullptr;
}
/// Fold (icmp)&(icmp) if possible.
Value *InstCombiner::foldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS,
Instruction &CxtI) {
// Fold (!iszero(A & K1) & !iszero(A & K2)) -> (A & (K1 | K2)) == (K1 | K2)
// if K1 and K2 are a one-bit mask.
if (Value *V = foldAndOrOfICmpsOfAndWithPow2(LHS, RHS, true, CxtI))
return V;
ICmpInst::Predicate PredL = LHS->getPredicate(), PredR = RHS->getPredicate();
// (icmp1 A, B) & (icmp2 A, B) --> (icmp3 A, B)
if (PredicatesFoldable(PredL, PredR)) {
if (LHS->getOperand(0) == RHS->getOperand(1) &&
LHS->getOperand(1) == RHS->getOperand(0))
LHS->swapOperands();
if (LHS->getOperand(0) == RHS->getOperand(0) &&
LHS->getOperand(1) == RHS->getOperand(1)) {
Value *Op0 = LHS->getOperand(0), *Op1 = LHS->getOperand(1);
unsigned Code = getICmpCode(LHS) & getICmpCode(RHS);
bool isSigned = LHS->isSigned() || RHS->isSigned();
return getNewICmpValue(isSigned, Code, Op0, Op1, Builder);
}
}
// handle (roughly): (icmp eq (A & B), C) & (icmp eq (A & D), E)
if (Value *V = foldLogOpOfMaskedICmps(LHS, RHS, true, Builder))
return V;
// E.g. (icmp sge x, 0) & (icmp slt x, n) --> icmp ult x, n
if (Value *V = simplifyRangeCheck(LHS, RHS, /*Inverted=*/false))
return V;
// E.g. (icmp slt x, n) & (icmp sge x, 0) --> icmp ult x, n
if (Value *V = simplifyRangeCheck(RHS, LHS, /*Inverted=*/false))
return V;
if (Value *V = foldAndOrOfEqualityCmpsWithConstants(LHS, RHS, true, Builder))
return V;
// This only handles icmp of constants: (icmp1 A, C1) & (icmp2 B, C2).
Value *LHS0 = LHS->getOperand(0), *RHS0 = RHS->getOperand(0);
ConstantInt *LHSC = dyn_cast<ConstantInt>(LHS->getOperand(1));
ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS->getOperand(1));
if (!LHSC || !RHSC)
return nullptr;
if (LHSC == RHSC && PredL == PredR) {
// (icmp ult A, C) & (icmp ult B, C) --> (icmp ult (A|B), C)
// where C is a power of 2 or
// (icmp eq A, 0) & (icmp eq B, 0) --> (icmp eq (A|B), 0)
if ((PredL == ICmpInst::ICMP_ULT && LHSC->getValue().isPowerOf2()) ||
(PredL == ICmpInst::ICMP_EQ && LHSC->isZero())) {
Value *NewOr = Builder->CreateOr(LHS0, RHS0);
return Builder->CreateICmp(PredL, NewOr, LHSC);
}
}
// (trunc x) == C1 & (and x, CA) == C2 -> (and x, CA|CMAX) == C1|C2
// where CMAX is the all ones value for the truncated type,
// iff the lower bits of C2 and CA are zero.
if (PredL == ICmpInst::ICMP_EQ && PredL == PredR && LHS->hasOneUse() &&
RHS->hasOneUse()) {
Value *V;
ConstantInt *AndC, *SmallC = nullptr, *BigC = nullptr;
// (trunc x) == C1 & (and x, CA) == C2
// (and x, CA) == C2 & (trunc x) == C1
if (match(RHS0, m_Trunc(m_Value(V))) &&
match(LHS0, m_And(m_Specific(V), m_ConstantInt(AndC)))) {
SmallC = RHSC;
BigC = LHSC;
} else if (match(LHS0, m_Trunc(m_Value(V))) &&
match(RHS0, m_And(m_Specific(V), m_ConstantInt(AndC)))) {
SmallC = LHSC;
BigC = RHSC;
}
if (SmallC && BigC) {
unsigned BigBitSize = BigC->getType()->getBitWidth();
unsigned SmallBitSize = SmallC->getType()->getBitWidth();
// Check that the low bits are zero.
APInt Low = APInt::getLowBitsSet(BigBitSize, SmallBitSize);
if ((Low & AndC->getValue()).isNullValue() &&
(Low & BigC->getValue()).isNullValue()) {
Value *NewAnd = Builder->CreateAnd(V, Low | AndC->getValue());
APInt N = SmallC->getValue().zext(BigBitSize) | BigC->getValue();
Value *NewVal = ConstantInt::get(AndC->getType()->getContext(), N);
return Builder->CreateICmp(PredL, NewAnd, NewVal);
}
}
}
// From here on, we only handle:
// (icmp1 A, C1) & (icmp2 A, C2) --> something simpler.
if (LHS0 != RHS0)
return nullptr;
// ICMP_[US][GL]E X, C is folded to ICMP_[US][GL]T elsewhere.
if (PredL == ICmpInst::ICMP_UGE || PredL == ICmpInst::ICMP_ULE ||
PredR == ICmpInst::ICMP_UGE || PredR == ICmpInst::ICMP_ULE ||
PredL == ICmpInst::ICMP_SGE || PredL == ICmpInst::ICMP_SLE ||
PredR == ICmpInst::ICMP_SGE || PredR == ICmpInst::ICMP_SLE)
return nullptr;
// We can't fold (ugt x, C) & (sgt x, C2).
if (!PredicatesFoldable(PredL, PredR))
return nullptr;
// Ensure that the larger constant is on the RHS.
bool ShouldSwap;
if (CmpInst::isSigned(PredL) ||
(ICmpInst::isEquality(PredL) && CmpInst::isSigned(PredR)))
ShouldSwap = LHSC->getValue().sgt(RHSC->getValue());
else
ShouldSwap = LHSC->getValue().ugt(RHSC->getValue());
if (ShouldSwap) {
std::swap(LHS, RHS);
std::swap(LHSC, RHSC);
std::swap(PredL, PredR);
}
// At this point, we know we have two icmp instructions
// comparing a value against two constants and and'ing the result
// together. Because of the above check, we know that we only have
// icmp eq, icmp ne, icmp [su]lt, and icmp [SU]gt here. We also know
// (from the icmp folding check above), that the two constants
// are not equal and that the larger constant is on the RHS
assert(LHSC != RHSC && "Compares not folded above?");
switch (PredL) {
default:
llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_NE:
switch (PredR) {
default:
llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_ULT:
if (LHSC == SubOne(RHSC)) // (X != 13 & X u< 14) -> X < 13
return Builder->CreateICmpULT(LHS0, LHSC);
if (LHSC->isNullValue()) // (X != 0 & X u< 14) -> X-1 u< 13
return insertRangeTest(LHS0, LHSC->getValue() + 1, RHSC->getValue(),
false, true);
break; // (X != 13 & X u< 15) -> no change
case ICmpInst::ICMP_SLT:
if (LHSC == SubOne(RHSC)) // (X != 13 & X s< 14) -> X < 13
return Builder->CreateICmpSLT(LHS0, LHSC);
break; // (X != 13 & X s< 15) -> no change
case ICmpInst::ICMP_NE:
// Potential folds for this case should already be handled.
break;
}
break;
case ICmpInst::ICMP_UGT:
switch (PredR) {
default:
llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_NE:
if (RHSC == AddOne(LHSC)) // (X u> 13 & X != 14) -> X u> 14
return Builder->CreateICmp(PredL, LHS0, RHSC);
break; // (X u> 13 & X != 15) -> no change
case ICmpInst::ICMP_ULT: // (X u> 13 & X u< 15) -> (X-14) <u 1
return insertRangeTest(LHS0, LHSC->getValue() + 1, RHSC->getValue(),
false, true);
}
break;
case ICmpInst::ICMP_SGT:
switch (PredR) {
default:
llvm_unreachable("Unknown integer condition code!");
case ICmpInst::ICMP_NE:
if (RHSC == AddOne(LHSC)) // (X s> 13 & X != 14) -> X s> 14
return Builder->CreateICmp(PredL, LHS0, RHSC);
break; // (X s> 13 & X != 15) -> no change
case ICmpInst::ICMP_SLT: // (X s> 13 & X s< 15) -> (X-14) s< 1
return insertRangeTest(LHS0, LHSC->getValue() + 1, RHSC->getValue(), true,
true);
}
break;
}
return nullptr;
}
/// Optimize (fcmp)&(fcmp). NOTE: Unlike the rest of instcombine, this returns
/// a Value which should already be inserted into the function.
Value *InstCombiner::foldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS) {
Value *Op0LHS = LHS->getOperand(0), *Op0RHS = LHS->getOperand(1);
Value *Op1LHS = RHS->getOperand(0), *Op1RHS = RHS->getOperand(1);
FCmpInst::Predicate Op0CC = LHS->getPredicate(), Op1CC = RHS->getPredicate();
if (Op0LHS == Op1RHS && Op0RHS == Op1LHS) {
// Swap RHS operands to match LHS.
Op1CC = FCmpInst::getSwappedPredicate(Op1CC);
std::swap(Op1LHS, Op1RHS);
}
// Simplify (fcmp cc0 x, y) & (fcmp cc1 x, y).
// Suppose the relation between x and y is R, where R is one of
// U(1000), L(0100), G(0010) or E(0001), and CC0 and CC1 are the bitmasks for
// testing the desired relations.
//
// Since (R & CC0) and (R & CC1) are either R or 0, we actually have this:
// bool(R & CC0) && bool(R & CC1)