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[ConstraintElimination] Clear new indices directly in getConstraint(NFC) 

Instead of checking if any of the new indices has a non-zero coefficient
before using the constraint, do this directly when constructing the
constraint.
This commit is contained in:
Florian Hahn 2022-09-14 15:31:25 +01:00
parent 5cff32b9f0
commit efd3ec47d9
No known key found for this signature in database
GPG Key ID: EEF712BB5E80EBBA
1 changed files with 19 additions and 15 deletions
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34
llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
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@ -90,18 +90,6 @@ struct ConstraintTy {
unsigned empty() const { return Coefficients.empty(); }
/// Returns true if any constraint has a non-zero coefficient for any of the
/// newly added indices. Zero coefficients for new indices are removed. If it
/// returns true, no new variable need to be added to the system.
bool needsNewIndices(const DenseMap<Value *, unsigned> &NewIndices) {
for (unsigned I = 0; I < NewIndices.size(); ++I) {
int64_t Last = Coefficients.pop_back_val();
if (Last != 0)
return true;
}
return false;
}
/// Returns true if all preconditions for this list of constraints are
/// satisfied given \p CS and the corresponding \p Value2Index mapping.
bool isValid(const ConstraintInfo &Info) const;
@ -384,6 +372,23 @@ ConstraintInfo::getConstraint(CmpInst::Predicate Pred, Value *Op0, Value *Op1,
return {};
R[0] = OffsetSum;
Res.Preconditions = std::move(Preconditions);
// Remove any (Coefficient, Variable) entry where the Coefficient is 0 for the
// new variables that need to be added to the system. Set NewIndexNeeded to
// true if any of the new variables has a non-zero coefficient.
bool NewIndexNeeded = false;
for (unsigned I = 0; I < NewIndices.size(); ++I) {
int64_t Last = R.back();
if (Last != 0) {
NewIndexNeeded = true;
break;
}
R.pop_back();
}
// All new variables had Coefficients of 0, so no new variables are needed.
if (!NewIndexNeeded)
NewIndices.clear();
return Res;
}
@ -645,7 +650,7 @@ tryToSimplifyOverflowMath(IntrinsicInst *II, ConstraintInfo &Info,
ConstraintInfo &Info) {
DenseMap<Value *, unsigned> NewIndices;
auto R = Info.getConstraint(Pred, A, B, NewIndices);
if (R.size() < 2 || R.needsNewIndices(NewIndices) || !R.isValid(Info))
if (R.size() < 2 || !NewIndices.empty() || !R.isValid(Info))
return false;
auto &CSToUse = Info.getCS(CmpInst::isSigned(Pred));
@ -763,8 +768,7 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT) {
DenseMap<Value *, unsigned> NewIndices;
auto R = Info.getConstraint(Cmp, NewIndices);
if (R.IsEq || R.empty() || R.needsNewIndices(NewIndices) ||
!R.isValid(Info))
if (R.IsEq || R.empty() || !NewIndices.empty() || !R.isValid(Info))
continue;
auto &CSToUse = Info.getCS(R.IsSigned);