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[ConstraintElimination] Use logic from 3771310eed for queries only. 

The logic added in 3771310eed was placed sub-optimally. Applying the
transform in ::getConstraint meant that it would also impact conditions
that are added to the system by the signed <-> unsigned transfer logic.

This meant we failed to add some signed facts to the signed system. To
make sure we still add as many useful facts to the signed/unsigned
systems, move the logic to the point where we query the system.
This commit is contained in:
Florian Hahn 2022-10-08 11:03:44 +01:00
parent 0c4f0bf40d
commit 9d31d1c214
No known key found for this signature in database
GPG Key ID: CF59919C6547A668
2 changed files with 18 additions and 15 deletions
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31
llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
View File

@ -111,11 +111,7 @@ class ConstraintInfo {
ConstraintSystem UnsignedCS;
ConstraintSystem SignedCS;
const DataLayout &DL;
public:
ConstraintInfo(const DataLayout &DL) : DL(DL) {}
DenseMap<Value *, unsigned> &getValue2Index(bool Signed) {
return Signed ? SignedValue2Index : UnsignedValue2Index;
}
@ -331,14 +327,6 @@ ConstraintInfo::getConstraint(CmpInst::Predicate Pred, Value *Op0, Value *Op1,
Pred != CmpInst::ICMP_SLE && Pred != CmpInst::ICMP_SLT)
return {};
// If both operands are known to be non-negative, change signed predicates to
// unsigned ones. This increases the reasoning effectiveness in combination
// with the signed <-> unsigned transfer logic.
if (CmpInst::isSigned(Pred) &&
isKnownNonNegative(Op0, DL, /*Depth=*/MaxAnalysisRecursionDepth - 1) &&
isKnownNonNegative(Op1, DL, /*Depth=*/MaxAnalysisRecursionDepth - 1))
Pred = CmpInst::getUnsignedPredicate(Pred);
SmallVector<PreconditionTy, 4> Preconditions;
bool IsSigned = CmpInst::isSigned(Pred);
auto &Value2Index = getValue2Index(IsSigned);
@ -754,7 +742,7 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT) {
bool Changed = false;
DT.updateDFSNumbers();
ConstraintInfo Info(F.getParent()->getDataLayout());
ConstraintInfo Info;
State S(DT);
// First, collect conditions implied by branches and blocks with their
@ -837,7 +825,22 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT) {
LLVM_DEBUG(dbgs() << "Checking " << *Cmp << "\n");
SmallVector<Value *> NewVariables;
auto R = Info.getConstraint(Cmp, NewVariables);
CmpInst::Predicate Pred = Cmp->getPredicate();
Value *A = Cmp->getOperand(0);
Value *B = Cmp->getOperand(1);
const DataLayout &DL = Cmp->getModule()->getDataLayout();
// If both operands are known to be non-negative, change signed
// predicates to unsigned ones. This increases the reasoning
// effectiveness in combination with the signed <-> unsigned transfer
// logic.
if (CmpInst::isSigned(Pred) &&
isKnownNonNegative(A, DL,
/*Depth=*/MaxAnalysisRecursionDepth - 1) &&
isKnownNonNegative(B, DL, /*Depth=*/MaxAnalysisRecursionDepth - 1))
Pred = CmpInst::getUnsignedPredicate(Pred);
auto R = Info.getConstraint(Pred, A, B, NewVariables);
if (R.IsEq || R.empty() || !NewVariables.empty() || !R.isValid(Info))
continue;

2
llvm/test/Transforms/ConstraintElimination/signed-query-unsigned-system.ll
View File

@ -149,7 +149,7 @@ define i1 @sge_neg_1_sge_0_known(i8 %a) {
; CHECK-NEXT: [[A_NE_0:%.*]] = icmp sge i16 [[EXT]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[A_NE_0]])
; CHECK-NEXT: [[T:%.*]] = icmp sge i16 [[EXT]], -1
; CHECK-NEXT: ret i1 [[T]]
; CHECK-NEXT: ret i1 true
;
%ext = zext i8 %a to i16
%a.ne.0 = icmp sge i16 %ext, 0