Skip to content

[ConstraintElimination] Add eq/ne facts to signed constraint system #121423

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 23, 2025
Merged

[ConstraintElimination] Add eq/ne facts to signed constraint system #121423

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
37 changes: 30 additions & 7 deletions llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -313,7 +313,8 @@ class ConstraintInfo {
/// New variables that need to be added to the system are collected in
/// \p NewVariables.
ConstraintTy getConstraint(CmpInst::Predicate Pred, Value *Op0, Value *Op1,
SmallVectorImpl<Value *> &NewVariables) const;
SmallVectorImpl<Value *> &NewVariables,
bool ForceSignedSystem = false) const;

/// Turns a comparison of the form \p Op0 \p Pred \p Op1 into a vector of
/// constraints using getConstraint. Returns an empty constraint if the result
Expand All @@ -330,6 +331,14 @@ class ConstraintInfo {
void transferToOtherSystem(CmpInst::Predicate Pred, Value *A, Value *B,
unsigned NumIn, unsigned NumOut,
SmallVectorImpl<StackEntry> &DFSInStack);

private:
/// Adds facts into constraint system. \p ForceSignedSystem can be set when
/// the \p Pred is eq/ne, and signed constraint system is used when it's
/// specified.
void addFactImpl(CmpInst::Predicate Pred, Value *A, Value *B, unsigned NumIn,
unsigned NumOut, SmallVectorImpl<StackEntry> &DFSInStack,
bool ForceSignedSystem);
};

/// Represents a (Coefficient * Variable) entry after IR decomposition.
Expand Down Expand Up @@ -636,8 +645,12 @@ static Decomposition decompose(Value *V,

ConstraintTy
ConstraintInfo::getConstraint(CmpInst::Predicate Pred, Value *Op0, Value *Op1,
SmallVectorImpl<Value *> &NewVariables) const {
SmallVectorImpl<Value *> &NewVariables,
bool ForceSignedSystem) const {
assert(NewVariables.empty() && "NewVariables must be empty when passed in");
assert((!ForceSignedSystem || CmpInst::isEquality(Pred)) &&
"signed system can only be forced on eq/ne");

bool IsEq = false;
bool IsNe = false;

Expand All @@ -652,15 +665,15 @@ ConstraintInfo::getConstraint(CmpInst::Predicate Pred, Value *Op0, Value *Op1,
break;
}
case CmpInst::ICMP_EQ:
if (match(Op1, m_Zero())) {
if (!ForceSignedSystem && match(Op1, m_Zero())) {
Pred = CmpInst::ICMP_ULE;
} else {
IsEq = true;
Pred = CmpInst::ICMP_ULE;
}
break;
case CmpInst::ICMP_NE:
if (match(Op1, m_Zero())) {
if (!ForceSignedSystem && match(Op1, m_Zero())) {
Pred = CmpInst::getSwappedPredicate(CmpInst::ICMP_UGT);
std::swap(Op0, Op1);
} else {
Expand All @@ -677,7 +690,7 @@ ConstraintInfo::getConstraint(CmpInst::Predicate Pred, Value *Op0, Value *Op1,
return {};

SmallVector<ConditionTy, 4> Preconditions;
bool IsSigned = CmpInst::isSigned(Pred);
bool IsSigned = ForceSignedSystem || CmpInst::isSigned(Pred);
auto &Value2Index = getValue2Index(IsSigned);
auto ADec = decompose(Op0->stripPointerCastsSameRepresentation(),
Preconditions, IsSigned, DL);
Expand Down Expand Up @@ -737,7 +750,7 @@ ConstraintInfo::getConstraint(CmpInst::Predicate Pred, Value *Op0, Value *Op1,
int64_t OffsetSum;
if (AddOverflow(Offset1, Offset2, OffsetSum))
return {};
if (Pred == (IsSigned ? CmpInst::ICMP_SLT : CmpInst::ICMP_ULT))
if (Pred == CmpInst::ICMP_SLT || Pred == CmpInst::ICMP_ULT)
if (AddOverflow(OffsetSum, int64_t(-1), OffsetSum))
return {};
R[0] = OffsetSum;
Expand Down Expand Up @@ -1580,10 +1593,20 @@ static bool checkOrAndOpImpliedByOther(
void ConstraintInfo::addFact(CmpInst::Predicate Pred, Value *A, Value *B,
unsigned NumIn, unsigned NumOut,
SmallVectorImpl<StackEntry> &DFSInStack) {
addFactImpl(Pred, A, B, NumIn, NumOut, DFSInStack, false);
// If the Pred is eq/ne, also add the fact to signed system.
if (CmpInst::isEquality(Pred))
addFactImpl(Pred, A, B, NumIn, NumOut, DFSInStack, true);
}

void ConstraintInfo::addFactImpl(CmpInst::Predicate Pred, Value *A, Value *B,
unsigned NumIn, unsigned NumOut,
SmallVectorImpl<StackEntry> &DFSInStack,
bool ForceSignedSystem) {
// If the constraint has a pre-condition, skip the constraint if it does not
// hold.
SmallVector<Value *> NewVariables;
auto R = getConstraint(Pred, A, B, NewVariables);
auto R = getConstraint(Pred, A, B, NewVariables, ForceSignedSystem);

// TODO: Support non-equality for facts as well.
if (!R.isValid(*this) || R.isNe())
Expand Down
50 changes: 50 additions & 0 deletions llvm/test/Transforms/ConstraintElimination/eq.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -424,3 +424,53 @@ bc_equal:
not_eq:
ret i1 false
}

define i1 @test_eq_for_signed_cmp(i32 noundef %v0, i32 noundef %v1, i32 noundef %v2) {
; CHECK-LABEL: @test_eq_for_signed_cmp(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[V2:%.*]], [[V0:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp sge i32 [[V0]], [[V1:%.*]]
; CHECK-NEXT: [[AND0:%.*]] = and i1 [[CMP1]], [[CMP]]
; CHECK-NEXT: [[CMP4:%.*]] = icmp sgt i32 [[V1]], [[V2]]
; CHECK-NEXT: [[AND1:%.*]] = and i1 false, [[AND0]]
; CHECK-NEXT: ret i1 [[AND1]]
;
entry:
%cmp = icmp eq i32 %v2, %v0
%cmp1 = icmp sge i32 %v0, %v1
%and0 = and i1 %cmp1, %cmp
%cmp4 = icmp sgt i32 %v1, %v2
%and1 = and i1 %cmp4, %and0
ret i1 %and1
}

define i1 @test_eq_for_signed_cmp_with_decompsition(i32 noundef %v0, i32 noundef %v1, i32 noundef %v2, i32 noundef %addend0, i32 noundef %addend1) {
; CHECK-LABEL: @test_eq_for_signed_cmp_with_decompsition(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[V0ADD:%.*]] = add nsw i32 [[V0:%.*]], [[ADDEND0:%.*]]
; CHECK-NEXT: [[V1ADD:%.*]] = add nsw i32 [[V1:%.*]], [[ADDEND1:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[V2:%.*]], [[V0ADD]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp sge i32 [[V0ADD]], [[V1ADD]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp sge i32 [[ADDEND0]], 0
; CHECK-NEXT: [[CMP3:%.*]] = icmp slt i32 [[ADDEND0]], [[ADDEND1]]
; CHECK-NEXT: [[AND0:%.*]] = and i1 [[CMP1]], [[CMP]]
; CHECK-NEXT: [[AND1:%.*]] = and i1 [[AND0]], [[CMP2]]
; CHECK-NEXT: [[AND2:%.*]] = and i1 [[AND1]], [[CMP3]]
; CHECK-NEXT: [[CMP4:%.*]] = icmp sgt i32 [[V1]], [[V2]]
; CHECK-NEXT: [[AND3:%.*]] = and i1 false, [[AND2]]
; CHECK-NEXT: ret i1 [[AND3]]
;
entry:
%v0add = add nsw i32 %v0, %addend0
%v1add = add nsw i32 %v1, %addend1
%cmp = icmp eq i32 %v2, %v0add
%cmp1 = icmp sge i32 %v0add, %v1add
%cmp2 = icmp sge i32 %addend0, 0
%cmp3 = icmp slt i32 %addend0, %addend1
%and0 = and i1 %cmp1, %cmp
%and1 = and i1 %and0, %cmp2
%and2 = and i1 %and1, %cmp3
%cmp4 = icmp sgt i32 %v1, %v2
%and3 = and i1 %cmp4, %and2
ret i1 %and3
}
6 changes: 2 additions & 4 deletions llvm/test/Transforms/ConstraintElimination/ne.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -71,8 +71,7 @@ define i1 @test_ne_eq_0(i8 %a, i8 %b) {
; CHECK-NEXT: [[RES_13:%.*]] = xor i1 [[RES_12]], false
; CHECK-NEXT: [[RES_14:%.*]] = xor i1 [[RES_13]], false
; CHECK-NEXT: [[RES_15:%.*]] = xor i1 [[RES_14]], false
; CHECK-NEXT: [[C_12:%.*]] = icmp sgt i8 [[A]], 0
; CHECK-NEXT: [[RES_16:%.*]] = xor i1 [[RES_15]], [[C_12]]
; CHECK-NEXT: [[RES_16:%.*]] = xor i1 [[RES_15]], false
; CHECK-NEXT: ret i1 [[RES_16]]
;
entry:
Expand Down Expand Up @@ -209,8 +208,7 @@ define i1 @test_ne_eq_1(i8 %a, i8 %b) {
; CHECK-NEXT: [[RES_13:%.*]] = xor i1 [[RES_12]], true
; CHECK-NEXT: [[RES_14:%.*]] = xor i1 [[RES_13]], true
; CHECK-NEXT: [[RES_15:%.*]] = xor i1 [[RES_14]], false
; CHECK-NEXT: [[C_12:%.*]] = icmp sgt i8 [[A]], 0
; CHECK-NEXT: [[RES_16:%.*]] = xor i1 [[RES_15]], [[C_12]]
; CHECK-NEXT: [[RES_16:%.*]] = xor i1 [[RES_15]], true
; CHECK-NEXT: ret i1 [[RES_16]]
;
entry:
Expand Down
3 changes: 1 addition & 2 deletions llvm/test/Transforms/ConstraintElimination/pr105785.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,7 @@ define void @pr105785(ptr %p) {
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i32 [[FOR_IND2]], 3
; CHECK-NEXT: br i1 [[CMP2]], label %[[FOR_BODY3]], label %[[FOR_COND]]
; CHECK: [[FOR_BODY3]]:
; CHECK-NEXT: [[SCMP:%.*]] = call i32 @llvm.scmp.i32.i32(i32 [[FOR_IND]], i32 1)
; CHECK-NEXT: store i32 [[SCMP]], ptr [[P]], align 4
; CHECK-NEXT: store i32 -1, ptr [[P]], align 4
; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[FOR_IND2]], 1
; CHECK-NEXT: br label %[[FOR_COND1]]
; CHECK: [[FOR_END6]]:
Expand Down
Loading