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

[Mehdi Amini]

================
@@ -0,0 +1,157 @@
+//===- 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 INCLUDE_MLIR_DIALECT_POLYNOMIAL_IR_POLYNOMIAL_H_
+#define 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"
+
+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;
+
+namespace detail {
+struct PolynomialStorage;
+} // namespace detail
+
+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(Monomial arg);
+
+public:
+  APInt coefficient;
+
+  // Always unsigned
+  APInt exponent;
+};
+
+/// A single-variable polynomial with integer coefficients. Polynomials are
+/// immutable and uniqued.
+///
+/// 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:
+  using ImplType = detail::PolynomialStorage;
+
+  constexpr Polynomial() = default;
+  explicit Polynomial(ImplType *terms) : terms(terms) {}
+
+  static Polynomial fromMonomials(ArrayRef<Monomial> monomials,
+                                  MLIRContext *context);
+  /// Returns a polynomial with coefficients given by `coeffs`
+  static Polynomial fromCoefficients(ArrayRef<int64_t> coeffs,
+                                     MLIRContext *context);
+
+  MLIRContext *getContext() const;
+
+  explicit operator bool() const { return terms != nullptr; }
+  bool operator==(Polynomial other) const { return other.terms == terms; }
+  bool operator!=(Polynomial other) const { return !(other.terms == terms); }
+
+  // Prints polynomial to 'os'.
+  void print(raw_ostream &os) const;
+  void print(raw_ostream &os, const std::string &separator,
+             const std::string &exponentiation) const;
+  void dump() const;
+
+  // Prints polynomial so that it can be used as a valid identifier
+  std::string toIdentifier() const;
+
+  // A polynomial's terms are canonically stored in order of increasing degree.
+  ArrayRef<Monomial> getTerms() const;
+
+  unsigned getDegree() const;
+
+  friend ::llvm::hash_code hash_value(Polynomial arg);
+
+private:
+  ImplType *terms{nullptr};
+};
+
+// Make Polynomial hashable.
+inline ::llvm::hash_code hash_value(Polynomial arg) {
+  return ::llvm::hash_value(arg.terms);
+}
+
+inline ::llvm::hash_code hash_value(Monomial arg) {
+  return ::llvm::hash_value(arg.coefficient) ^ ::llvm::hash_value(arg.exponent);
----------------
joker-eph wrote:

Using `^` seems uncommon? Isn't `llvm::hash_combine` enough for you here?

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