[MLIR][Presburger] add a non-const Matrix::getRow() returning a MutableArrayRef

Reviewed By: Groverkss

Differential Revision: https://reviews.llvm.org/D122136

mlir/include/mlir/Analysis/Presburger/Matrix.h

@@ -72,7 +72,8 @@ public:
   /// reallocations.
   void reserveRows(unsigned rows);
 
-  /// Get an ArrayRef corresponding to the specified row.
+  /// Get a [Mutable]ArrayRef corresponding to the specified row.
+  MutableArrayRef<int64_t> getRow(unsigned row);
   ArrayRef<int64_t> getRow(unsigned row) const;
 
   /// Insert columns having positions pos, pos + 1, ... pos + count - 1.

mlir/lib/Analysis/Presburger/Matrix.cpp

@@ -101,6 +101,10 @@ void Matrix::swapColumns(unsigned column, unsigned otherColumn) {
     std::swap(at(row, column), at(row, otherColumn));
 }
 
+MutableArrayRef<int64_t> Matrix::getRow(unsigned row) {
+  return {&data[row * nReservedColumns], nColumns};
+}
+
 ArrayRef<int64_t> Matrix::getRow(unsigned row) const {
   return {&data[row * nReservedColumns], nColumns};
 }