mlir/Presburger: optimize to avoid creating copies (#97897)

Optimize the Presburger library to avoid unnecessarily creating copies.
While at it, fix some other minor issues in the codebase.

Author: artagnon

mlir/include/mlir/Analysis/Presburger/QuasiPolynomial.h

@@ -36,10 +36,10 @@ namespace presburger {
 // g_{ij} : Q^n -> Q are affine functionals.
 class QuasiPolynomial : public PresburgerSpace {
 public:
-  QuasiPolynomial(unsigned numVars, SmallVector<Fraction> coeffs = {},
-                  std::vector<std::vector<SmallVector<Fraction>>> aff = {});
+  QuasiPolynomial(unsigned numVars, ArrayRef<Fraction> coeffs = {},
+                  ArrayRef<std::vector<SmallVector<Fraction>>> aff = {});
 
-  QuasiPolynomial(unsigned numVars, Fraction constant);
+  QuasiPolynomial(unsigned numVars, const Fraction &constant);
 
   // Find the number of inputs (numDomain) to the polynomial.
   // numSymbols is set to zero.
@@ -57,7 +57,7 @@ class QuasiPolynomial : public PresburgerSpace {
   QuasiPolynomial operator+(const QuasiPolynomial &x) const;
   QuasiPolynomial operator-(const QuasiPolynomial &x) const;
   QuasiPolynomial operator*(const QuasiPolynomial &x) const;
-  QuasiPolynomial operator/(const Fraction x) const;
+  QuasiPolynomial operator/(const Fraction &x) const;
 
   // Removes terms which evaluate to zero from the expression
   // and folds affine functions which are constant into the
@@ -77,4 +77,4 @@ class QuasiPolynomial : public PresburgerSpace {
 } // namespace presburger
 } // namespace mlir
 
-#endif // MLIR_ANALYSIS_PRESBURGER_QUASIPOLYNOMIAL_H
+#endif // MLIR_ANALYSIS_PRESBURGER_QUASIPOLYNOMIAL_H

mlir/lib/Analysis/Presburger/Barvinok.cpp

@@ -361,7 +361,7 @@ mlir::presburger::detail::computePolytopeGeneratingFunction(
       continue;
     // If this subset corresponds to a vertex that has not been considered,
     // store it.
-    vertices.push_back(*vertex);
+    vertices.emplace_back(*vertex);
 
     // If a vertex is formed by the intersection of more than d facets, we
     // assume that any d-subset of these facets can be solved to obtain its
@@ -472,10 +472,10 @@ mlir::presburger::detail::computePolytopeGeneratingFunction(
 Point mlir::presburger::detail::getNonOrthogonalVector(
     ArrayRef<Point> vectors) {
   unsigned dim = vectors[0].size();
-  assert(
-      llvm::all_of(vectors,
-                   [&](const Point &vector) { return vector.size() == dim; }) &&
-      "all vectors need to be the same size!");
+  assert(llvm::all_of(
+             vectors,
+             [&dim](const Point &vector) { return vector.size() == dim; }) &&
+         "all vectors need to be the same size!");
 
   SmallVector<Fraction> newPoint = {Fraction(1, 1)};
   Fraction maxDisallowedValue = -Fraction(1, 0),
@@ -493,7 +493,7 @@ Point mlir::presburger::detail::getNonOrthogonalVector(
       // Find the biggest such value
       maxDisallowedValue = std::max(maxDisallowedValue, disallowedValue);
     }
-    newPoint.push_back(maxDisallowedValue + 1);
+    newPoint.emplace_back(maxDisallowedValue + 1);
   }
   return newPoint;
 }
@@ -519,19 +519,20 @@ QuasiPolynomial mlir::presburger::detail::getCoefficientInRationalFunction(
   unsigned numParam = num[0].getNumInputs();
   // We use the `isEqual` method of PresburgerSpace, which QuasiPolynomial
   // inherits from.
-  assert(
-      llvm::all_of(
-          num, [&](const QuasiPolynomial &qp) { return num[0].isEqual(qp); }) &&
-      "the quasipolynomials should all belong to the same space!");
+  assert(llvm::all_of(num,
+                      [&num](const QuasiPolynomial &qp) {
+                        return num[0].isEqual(qp);
+                      }) &&
+         "the quasipolynomials should all belong to the same space!");
 
   std::vector<QuasiPolynomial> coefficients;
   coefficients.reserve(power + 1);
 
-  coefficients.push_back(num[0] / den[0]);
+  coefficients.emplace_back(num[0] / den[0]);
   for (unsigned i = 1; i <= power; ++i) {
     // If the power is not there in the numerator, the coefficient is zero.
-    coefficients.push_back(i < num.size() ? num[i]
-                                          : QuasiPolynomial(numParam, 0));
+    coefficients.emplace_back(i < num.size() ? num[i]
+                                             : QuasiPolynomial(numParam, 0));
 
     // After den.size(), the coefficients are zero, so we stop
     // subtracting at that point (if it is less than i).
@@ -573,15 +574,15 @@ substituteMuInTerm(unsigned numParams, const ParamPoint &v,
   SmallVector<Fraction> coefficients;
   coefficients.reserve(numDims);
   for (const Point &d : ds)
-    coefficients.push_back(-dotProduct(mu, d));
+    coefficients.emplace_back(-dotProduct(mu, d));
 
   // Then, the affine function is a single floor expression, given by the
   // corresponding column of v.
   ParamPoint vTranspose = v.transpose();
   std::vector<std::vector<SmallVector<Fraction>>> affine;
   affine.reserve(numDims);
   for (unsigned j = 0; j < numDims; ++j)
-    affine.push_back({SmallVector<Fraction>(vTranspose.getRow(j))});
+    affine.push_back({SmallVector<Fraction>{vTranspose.getRow(j)}});
 
   QuasiPolynomial num(numParams, coefficients, affine);
   num = num.simplify();
@@ -593,7 +594,7 @@ substituteMuInTerm(unsigned numParams, const ParamPoint &v,
   for (const Point &d : ds) {
     // This term in the denominator is
     // (1 - t^dens.back())
-    dens.push_back(dotProduct(d, mu));
+    dens.emplace_back(dotProduct(d, mu));
   }
 
   return {num, dens};
@@ -641,7 +642,7 @@ std::vector<QuasiPolynomial> getBinomialCoefficients(const QuasiPolynomial &n,
   coefficients.emplace_back(numParams, 1);
   for (unsigned j = 1; j <= r; ++j)
     // We use the recursive formula for binomial coefficients here and below.
-    coefficients.push_back(
+    coefficients.emplace_back(
         (coefficients[j - 1] * (n - QuasiPolynomial(numParams, j - 1)) /
          Fraction(j, 1))
             .simplify());
@@ -656,7 +657,7 @@ std::vector<Fraction> getBinomialCoefficients(const Fraction &n,
   coefficients.reserve((int64_t)floor(r));
   coefficients.emplace_back(1);
   for (unsigned j = 1; j <= r; ++j)
-    coefficients.push_back(coefficients[j - 1] * (n - (j - 1)) / (j));
+    coefficients.emplace_back(coefficients[j - 1] * (n - (j - 1)) / (j));
   return coefficients;
 }
 
@@ -764,8 +765,8 @@ mlir::presburger::detail::computeNumTerms(const GeneratingFunction &gf) {
     eachTermDenCoefficients.reserve(r);
     for (const Fraction &den : dens) {
       singleTermDenCoefficients = getBinomialCoefficients(den + 1, den + 1);
-      eachTermDenCoefficients.push_back(
-          ArrayRef<Fraction>(singleTermDenCoefficients).slice(1));
+      eachTermDenCoefficients.emplace_back(
+          ArrayRef<Fraction>(singleTermDenCoefficients).drop_front());
     }
 
     // Now we find the coefficients in Q(s) itself

mlir/lib/Analysis/Presburger/IntegerRelation.cpp

@@ -511,10 +511,10 @@ void IntegerRelation::getLowerAndUpperBoundIndices(
       continue;
     if (atIneq(r, pos) >= 1) {
       // Lower bound.
-      lbIndices->push_back(r);
+      lbIndices->emplace_back(r);
     } else if (atIneq(r, pos) <= -1) {
       // Upper bound.
-      ubIndices->push_back(r);
+      ubIndices->emplace_back(r);
     }
   }
 
@@ -528,7 +528,7 @@ void IntegerRelation::getLowerAndUpperBoundIndices(
       continue;
     if (containsConstraintDependentOnRange(r, /*isEq=*/true))
       continue;
-    eqIndices->push_back(r);
+    eqIndices->emplace_back(r);
   }
 }
 
@@ -791,7 +791,7 @@ IntMatrix IntegerRelation::getBoundedDirections() const {
   // processes all the inequalities.
   for (unsigned i = 0, e = getNumInequalities(); i < e; ++i) {
     if (simplex.isBoundedAlongConstraint(i))
-      boundedIneqs.push_back(i);
+      boundedIneqs.emplace_back(i);
   }
 
   // The direction vector is given by the coefficients and does not include the
@@ -1981,13 +1981,13 @@ void IntegerRelation::fourierMotzkinEliminate(unsigned pos, bool darkShadow,
   for (unsigned r = 0, e = getNumInequalities(); r < e; r++) {
     if (atIneq(r, pos) == 0) {
       // Var does not appear in bound.
-      nbIndices.push_back(r);
+      nbIndices.emplace_back(r);
     } else if (atIneq(r, pos) >= 1) {
       // Lower bound.
-      lbIndices.push_back(r);
+      lbIndices.emplace_back(r);
     } else {
       // Upper bound.
-      ubIndices.push_back(r);
+      ubIndices.emplace_back(r);
     }
   }
 
@@ -2028,8 +2028,8 @@ void IntegerRelation::fourierMotzkinEliminate(unsigned pos, bool darkShadow,
           continue;
         assert(lbCoeff >= 1 && ubCoeff >= 1 && "bounds wrongly identified");
         DynamicAPInt lcm = llvm::lcm(lbCoeff, ubCoeff);
-        ineq.push_back(atIneq(ubPos, l) * (lcm / ubCoeff) +
-                       atIneq(lbPos, l) * (lcm / lbCoeff));
+        ineq.emplace_back(atIneq(ubPos, l) * (lcm / ubCoeff) +
+                          atIneq(lbPos, l) * (lcm / lbCoeff));
         assert(lcm > 0 && "lcm should be positive!");
         if (lcm != 1)
           allLCMsAreOne = false;
@@ -2057,7 +2057,7 @@ void IntegerRelation::fourierMotzkinEliminate(unsigned pos, bool darkShadow,
     for (unsigned l = 0, e = getNumCols(); l < e; l++) {
       if (l == pos)
         continue;
-      ineq.push_back(atIneq(nbPos, l));
+      ineq.emplace_back(atIneq(nbPos, l));
     }
     newRel.addInequality(ineq);
   }
@@ -2072,7 +2072,7 @@ void IntegerRelation::fourierMotzkinEliminate(unsigned pos, bool darkShadow,
     for (unsigned l = 0, e = getNumCols(); l < e; l++) {
       if (l == pos)
         continue;
-      eq.push_back(atEq(r, l));
+      eq.emplace_back(atEq(r, l));
     }
     newRel.addEquality(eq);
   }
@@ -2264,8 +2264,8 @@ IntegerRelation::unionBoundingBox(const IntegerRelation &otherCst) {
                    std::negate<DynamicAPInt>());
     std::copy(maxUb.begin(), maxUb.end(), newUb.begin() + getNumDimVars());
 
-    boundingLbs.push_back(newLb);
-    boundingUbs.push_back(newUb);
+    boundingLbs.emplace_back(newLb);
+    boundingUbs.emplace_back(newUb);
   }
 
   // Clear all constraints and add the lower/upper bounds for the bounding box.
@@ -2309,7 +2309,7 @@ static void getIndependentConstraints(const IntegerRelation &cst, unsigned pos,
         break;
     }
     if (c == pos + num)
-      nbIneqIndices.push_back(r);
+      nbIneqIndices.emplace_back(r);
   }
 
   for (unsigned r = 0, e = cst.getNumEqualities(); r < e; r++) {
@@ -2320,7 +2320,7 @@ static void getIndependentConstraints(const IntegerRelation &cst, unsigned pos,
         break;
     }
     if (c == pos + num)
-      nbEqIndices.push_back(r);
+      nbEqIndices.emplace_back(r);
   }
 }
 

mlir/lib/Analysis/Presburger/LinearTransform.cpp

@@ -51,7 +51,7 @@ IntegerRelation LinearTransform::applyTo(const IntegerRelation &rel) const {
     const DynamicAPInt &c = eq.back();
 
     SmallVector<DynamicAPInt, 8> newEq = preMultiplyWithRow(eq.drop_back());
-    newEq.push_back(c);
+    newEq.emplace_back(c);
     result.addEquality(newEq);
   }
 
@@ -61,7 +61,7 @@ IntegerRelation LinearTransform::applyTo(const IntegerRelation &rel) const {
     const DynamicAPInt &c = ineq.back();
 
     SmallVector<DynamicAPInt, 8> newIneq = preMultiplyWithRow(ineq.drop_back());
-    newIneq.push_back(c);
+    newIneq.emplace_back(c);
     result.addInequality(newIneq);
   }
 

mlir/lib/Analysis/Presburger/PWMAFunction.cpp

@@ -46,7 +46,7 @@ static SmallVector<DynamicAPInt, 8> subtractExprs(ArrayRef<DynamicAPInt> vecA,
   SmallVector<DynamicAPInt, 8> result;
   result.reserve(vecA.size());
   for (unsigned i = 0, e = vecA.size(); i < e; ++i)
-    result.push_back(vecA[i] - vecB[i]);
+    result.emplace_back(vecA[i] - vecB[i]);
   return result;
 }
 
@@ -78,7 +78,7 @@ MultiAffineFunction::valueAt(ArrayRef<DynamicAPInt> point) const {
   // function of; we have computed one possible set of values and use them here.
   pointHomogenous.reserve(pointHomogenous.size() + divValues.size());
   for (const std::optional<DynamicAPInt> &divVal : divValues)
-    pointHomogenous.push_back(*divVal);
+    pointHomogenous.emplace_back(*divVal);
   // The matrix `output` has an affine expression in the ith row, corresponding
   // to the expression for the ith value in the output vector. The last column
   // of the matrix contains the constant term. Let v be the input point with
@@ -295,7 +295,7 @@ void PWMAFunction::addPiece(const Piece &piece) {
   assert(piece.isConsistent() && "Piece should be consistent");
   assert(piece.domain.intersect(getDomain()).isIntegerEmpty() &&
          "Piece should be disjoint from the function");
-  pieces.push_back(piece);
+  pieces.emplace_back(piece);
 }
 
 void PWMAFunction::print(raw_ostream &os) const {