[Mlir-commits] [mlir] Add a polynomial dialect shell, attributes, and types (PR #72081)

[Oleksandr Alex Zinenko]

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+//===- Polynomial.h - A storage class for polynomial types ------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_INCLUDE_MLIR_DIALECT_POLYNOMIAL_IR_POLYNOMIAL_H_
+#define MLIR_INCLUDE_MLIR_DIALECT_POLYNOMIAL_IR_POLYNOMIAL_H_
+
+#include <utility>
+
+#include "mlir/Support/LLVM.h"
+#include "llvm/ADT/APInt.h"
+#include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/Hashing.h"
+#include "llvm/ADT/SmallVector.h"
+
+namespace mlir {
+
+class MLIRContext;
+
+namespace polynomial {
+
+/// This restricts statically defined polynomials to have at most 64-bit
+/// coefficients. This may be relaxed in the future, but it seems unlikely one
+/// would want to specify 128-bit polynomials statically in the source code.
+constexpr unsigned apintBitWidth = 64;
+
+/// A class representing a monomial of a single-variable polynomial with integer
+/// coefficients.
+class Monomial {
+public:
+  Monomial(int64_t coeff, uint64_t expo)
+      : coefficient(apintBitWidth, coeff), exponent(apintBitWidth, expo) {}
+
+  Monomial(APInt coeff, APInt expo)
+      : coefficient(std::move(coeff)), exponent(std::move(expo)) {}
+
+  Monomial() : coefficient(apintBitWidth, 0), exponent(apintBitWidth, 0) {}
+
+  bool operator==(const Monomial &other) const {
+    return other.coefficient == coefficient && other.exponent == exponent;
+  }
+  bool operator!=(const Monomial &other) const {
+    return other.coefficient != coefficient || other.exponent != exponent;
+  }
+
+  /// Monomials are ordered by exponent.
+  bool operator<(const Monomial &other) const {
+    return (exponent.ult(other.exponent));
+  }
+
+  // Prints polynomial to 'os'.
+  void print(raw_ostream &os) const;
+
+  friend ::llvm::hash_code hash_value(const Monomial &arg);
+
+public:
+  APInt coefficient;
+
+  // Always unsigned
+  APInt exponent;
+};
+
+/// A single-variable polynomial with integer coefficients.
+///
+/// Eg: x^1024 + x + 1
+///
+/// The symbols used as the polynomial's indeterminate don't matter, so long as
+/// it is used consistently throughout the polynomial.
+class Polynomial {
+public:
+  Polynomial() = delete;
+
+  Polynomial(const llvm::SmallVector<Monomial> &terms) : terms(terms){};
+
+  static Polynomial fromMonomials(ArrayRef<Monomial> monomials);
+
+  /// Returns a polynomial with coefficients given by `coeffs`. The value
+  /// coeffs[i] is converted to a monomial with exponent i.
+  static Polynomial fromCoefficients(ArrayRef<int64_t> coeffs);
+
+  explicit operator bool() const { return !terms.empty(); }
+  bool operator==(const Polynomial &other) const {
+    return other.terms == terms;
+  }
+  bool operator!=(const Polynomial &other) const {
+    return !(other.terms == terms);
+  }
+
+  // Prints polynomial to 'os'.
+  void print(raw_ostream &os) const;
+  void print(raw_ostream &os, ::llvm::StringRef separator,
+             ::llvm::StringRef exponentiation) const;
+  void dump() const;
+
+  // Prints polynomial so that it can be used as a valid identifier
+  std::string toIdentifier() const;
+
+  unsigned getDegree() const;
+
+  friend ::llvm::hash_code hash_value(Polynomial arg);
+
+private:
+  // The monomial terms for this polynomial.
+  SmallVector<Monomial> terms;
+};
+
+// Make Polynomial hashable.
+inline ::llvm::hash_code hash_value(Polynomial arg) {
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ftynse wrote:

Nit: `const &` on the argument?

https://github.com/llvm/llvm-project/pull/72081