Skip to content

[InstCombine] move foldAndOrOfICmpsOfAndWithPow2 into foldLogOpOfMaskedICmps #121970

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Jan 8, 2025
Merged

[InstCombine] move foldAndOrOfICmpsOfAndWithPow2 into foldLogOpOfMaskedICmps #121970

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
227 changes: 98 additions & 129 deletions llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -514,7 +514,8 @@ static Value *foldLogOpOfMaskedICmpsAsymmetric(
/// into a single (icmp(A & X) ==/!= Y).
static Value *foldLogOpOfMaskedICmps(ICmpInst *LHS, ICmpInst *RHS, bool IsAnd,
bool IsLogical,
InstCombiner::BuilderTy &Builder) {
InstCombiner::BuilderTy &Builder,
const SimplifyQuery &Q) {
Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr, *E = nullptr;
ICmpInst::Predicate PredL = LHS->getPredicate(), PredR = RHS->getPredicate();
std::optional<std::pair<unsigned, unsigned>> MaskPair =
Expand Down Expand Up @@ -587,93 +588,107 @@ static Value *foldLogOpOfMaskedICmps(ICmpInst *LHS, ICmpInst *RHS, bool IsAnd,
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.
const APInt *ConstB, *ConstD;
if (!match(B, m_APInt(ConstB)) || !match(D, m_APInt(ConstD)))
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 = *ConstB & *ConstD;
if (NewMask == *ConstB)
return LHS;
else if (NewMask == *ConstD)
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 = *ConstB | *ConstD;
if (NewMask == *ConstB)
return LHS;
else if (NewMask == *ConstD)
return RHS;
}

if (Mask & (BMask_Mixed | BMask_NotMixed)) {
// 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.

// NotMixed:
// (icmp ne (A & B), C) & (icmp ne (A & D), E)
// -> (icmp ne (A & (B & D)), (C & E))
// Check the intersection (B & D) for inequality.
// Assume that (B & D) == B || (B & D) == D, i.e B/D is a subset of D/B
// and (B & D) & (C ^ E) == 0, bits of C and E, which are shared by both the
// B and the D, don't contradict.
// Note that we can assume (~B & C) == 0 && (~D & E) == 0, previous
// operation should delete these icmps if it hadn't been met.

const APInt *OldConstC, *OldConstE;
if (!match(C, m_APInt(OldConstC)) || !match(E, m_APInt(OldConstE)))
return nullptr;

auto FoldBMixed = [&](ICmpInst::Predicate CC, bool IsNot) -> Value * {
CC = IsNot ? CmpInst::getInversePredicate(CC) : CC;
const APInt ConstC = PredL != CC ? *ConstB ^ *OldConstC : *OldConstC;
const APInt ConstE = PredR != CC ? *ConstD ^ *OldConstE : *OldConstE;
if (match(B, m_APInt(ConstB)) && match(D, m_APInt(ConstD))) {
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 = *ConstB & *ConstD;
if (NewMask == *ConstB)
return LHS;
if (NewMask == *ConstD)
return RHS;
}

if (((*ConstB & *ConstD) & (ConstC ^ ConstE)).getBoolValue())
return IsNot ? nullptr : ConstantInt::get(LHS->getType(), !IsAnd);
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 = *ConstB | *ConstD;
if (NewMask == *ConstB)
return LHS;
if (NewMask == *ConstD)
return RHS;
}

if (IsNot && !ConstB->isSubsetOf(*ConstD) && !ConstD->isSubsetOf(*ConstB))
if (Mask & (BMask_Mixed | BMask_NotMixed)) {
// 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.

// NotMixed:
// (icmp ne (A & B), C) & (icmp ne (A & D), E)
// -> (icmp ne (A & (B & D)), (C & E))
// Check the intersection (B & D) for inequality.
// Assume that (B & D) == B || (B & D) == D, i.e B/D is a subset of D/B
// and (B & D) & (C ^ E) == 0, bits of C and E, which are shared by both
// the B and the D, don't contradict. Note that we can assume (~B & C) ==
// 0 && (~D & E) == 0, previous operation should delete these icmps if it
// hadn't been met.

const APInt *OldConstC, *OldConstE;
if (!match(C, m_APInt(OldConstC)) || !match(E, m_APInt(OldConstE)))
return nullptr;

APInt BD, CE;
if (IsNot) {
BD = *ConstB & *ConstD;
CE = ConstC & ConstE;
} else {
BD = *ConstB | *ConstD;
CE = ConstC | ConstE;
}
Value *NewAnd = Builder.CreateAnd(A, BD);
Value *CEVal = ConstantInt::get(A->getType(), CE);
return Builder.CreateICmp(CC, CEVal, NewAnd);
};
auto FoldBMixed = [&](ICmpInst::Predicate CC, bool IsNot) -> Value * {
CC = IsNot ? CmpInst::getInversePredicate(CC) : CC;
const APInt ConstC = PredL != CC ? *ConstB ^ *OldConstC : *OldConstC;
const APInt ConstE = PredR != CC ? *ConstD ^ *OldConstE : *OldConstE;

if (((*ConstB & *ConstD) & (ConstC ^ ConstE)).getBoolValue())
return IsNot ? nullptr : ConstantInt::get(LHS->getType(), !IsAnd);

if (IsNot && !ConstB->isSubsetOf(*ConstD) &&
!ConstD->isSubsetOf(*ConstB))
return nullptr;

APInt BD, CE;
if (IsNot) {
BD = *ConstB & *ConstD;
CE = ConstC & ConstE;
} else {
BD = *ConstB | *ConstD;
CE = ConstC | ConstE;
}
Value *NewAnd = Builder.CreateAnd(A, BD);
Value *CEVal = ConstantInt::get(A->getType(), CE);
return Builder.CreateICmp(CC, CEVal, NewAnd);
};

if (Mask & BMask_Mixed)
return FoldBMixed(NewCC, false);
if (Mask & BMask_NotMixed) // can be else also
return FoldBMixed(NewCC, true);
}
}

if (Mask & BMask_Mixed)
return FoldBMixed(NewCC, false);
if (Mask & BMask_NotMixed) // can be else also
return FoldBMixed(NewCC, true);
// (icmp eq (A & B), 0) | (icmp eq (A & D), 0)
// -> (icmp ne (A & (B|D)), (B|D))
// (icmp ne (A & B), 0) & (icmp ne (A & D), 0)
// -> (icmp eq (A & (B|D)), (B|D))
// iff B and D is known to be a power of two
if (Mask & Mask_NotAllZeros &&
isKnownToBeAPowerOfTwo(B, /*OrZero=*/false, /*Depth=*/0, Q) &&
isKnownToBeAPowerOfTwo(D, /*OrZero=*/false, /*Depth=*/0, Q)) {
// If this is a logical and/or, then we must prevent propagation of a
// poison value from the RHS by inserting freeze.
if (IsLogical)
D = Builder.CreateFreeze(D);
Value *Mask = Builder.CreateOr(B, D);
Value *Masked = Builder.CreateAnd(A, Mask);
return Builder.CreateICmp(NewCC, Masked, Mask);
}
return nullptr;
}
Expand Down Expand Up @@ -776,46 +791,6 @@ foldAndOrOfICmpsWithPow2AndWithZero(InstCombiner::BuilderTy &Builder,
return Builder.CreateICmp(Pred, And, Op);
}

// 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 *InstCombinerImpl::foldAndOrOfICmpsOfAndWithPow2(ICmpInst *LHS,
ICmpInst *RHS,
Instruction *CxtI,
bool IsAnd,
bool IsLogical) {
CmpInst::Predicate Pred = IsAnd ? CmpInst::ICMP_NE : CmpInst::ICMP_EQ;
if (LHS->getPredicate() != Pred || RHS->getPredicate() != Pred)
return nullptr;

if (!match(LHS->getOperand(1), m_Zero()) ||
!match(RHS->getOperand(1), m_Zero()))
return nullptr;

Value *L1, *L2, *R1, *R2;
if (match(LHS->getOperand(0), m_And(m_Value(L1), m_Value(L2))) &&
match(RHS->getOperand(0), m_And(m_Value(R1), m_Value(R2)))) {
if (L1 == R2 || L2 == R2)
std::swap(R1, R2);
if (L2 == R1)
std::swap(L1, L2);

if (L1 == R1 &&
isKnownToBeAPowerOfTwo(L2, false, 0, CxtI) &&
isKnownToBeAPowerOfTwo(R2, false, 0, CxtI)) {
// If this is a logical and/or, then we must prevent propagation of a
// poison value from the RHS by inserting freeze.
if (IsLogical)
R2 = Builder.CreateFreeze(R2);
Value *Mask = Builder.CreateOr(L2, R2);
Value *Masked = Builder.CreateAnd(L1, Mask);
auto NewPred = IsAnd ? CmpInst::ICMP_EQ : CmpInst::ICMP_NE;
return Builder.CreateICmp(NewPred, Masked, Mask);
}
}

return nullptr;
}

/// General pattern:
/// X & Y
///
Expand Down Expand Up @@ -3327,12 +3302,6 @@ Value *InstCombinerImpl::foldAndOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
bool IsLogical) {
const SimplifyQuery Q = SQ.getWithInstruction(&I);

// Fold (iszero(A & K1) | iszero(A & K2)) -> (A & (K1 | K2)) != (K1 | K2)
// 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, &I, IsAnd, IsLogical))
return V;

ICmpInst::Predicate PredL = LHS->getPredicate(), PredR = RHS->getPredicate();
Value *LHS0 = LHS->getOperand(0), *RHS0 = RHS->getOperand(0);
Value *LHS1 = LHS->getOperand(1), *RHS1 = RHS->getOperand(1);
Expand All @@ -3359,7 +3328,7 @@ Value *InstCombinerImpl::foldAndOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
// handle (roughly):
// (icmp ne (A & B), C) | (icmp ne (A & D), E)
// (icmp eq (A & B), C) & (icmp eq (A & D), E)
if (Value *V = foldLogOpOfMaskedICmps(LHS, RHS, IsAnd, IsLogical, Builder))
if (Value *V = foldLogOpOfMaskedICmps(LHS, RHS, IsAnd, IsLogical, Builder, Q))
return V;

if (Value *V =
Expand Down
3 changes: 0 additions & 3 deletions llvm/lib/Transforms/InstCombine/InstCombineInternal.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -435,9 +435,6 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
Instruction *
canonicalizeConditionalNegationViaMathToSelect(BinaryOperator &i);

Value *foldAndOrOfICmpsOfAndWithPow2(ICmpInst *LHS, ICmpInst *RHS,
Instruction *CxtI, bool IsAnd,
bool IsLogical = false);
Value *matchSelectFromAndOr(Value *A, Value *B, Value *C, Value *D,
bool InvertFalseVal = false);
Value *getSelectCondition(Value *A, Value *B, bool ABIsTheSame);
Expand Down
7 changes: 3 additions & 4 deletions llvm/test/Transforms/InstCombine/onehot_merge.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1147,10 +1147,9 @@ define i1 @foo1_and_signbit_lshr_without_shifting_signbit_not_pwr2_logical(i32 %
define i1 @two_types_of_bittest(i8 %x, i8 %c) {
; CHECK-LABEL: @two_types_of_bittest(
; CHECK-NEXT: [[T0:%.*]] = shl nuw i8 1, [[C:%.*]]
; CHECK-NEXT: [[ICMP1:%.*]] = icmp slt i8 [[X:%.*]], 0
; CHECK-NEXT: [[AND:%.*]] = and i8 [[X]], [[T0]]
; CHECK-NEXT: [[ICMP2:%.*]] = icmp ne i8 [[AND]], 0
; CHECK-NEXT: [[RET:%.*]] = and i1 [[ICMP1]], [[ICMP2]]
; CHECK-NEXT: [[TMP1:%.*]] = or i8 [[T0]], -128
; CHECK-NEXT: [[TMP2:%.*]] = and i8 [[X:%.*]], [[TMP1]]
; CHECK-NEXT: [[RET:%.*]] = icmp eq i8 [[TMP2]], [[TMP1]]
; CHECK-NEXT: ret i1 [[RET]]
;
%t0 = shl i8 1, %c
Expand Down
Loading