[Mlir-commits] [mlir] mlir/Presburger: contribute a free-standing parser (PR #94916)
Kunwar Grover
llvmlistbot at llvm.org
Sun Jul 7 05:42:26 PDT 2024
================
@@ -0,0 +1,345 @@
+//===- ParseStructs.h - Presburger Parse Structrures ------------*- 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_ANALYSIS_PRESBURGER_PARSER_PARSESTRUCTS_H
+#define MLIR_ANALYSIS_PRESBURGER_PARSER_PARSESTRUCTS_H
+
+#include "mlir/Analysis/Presburger/IntegerRelation.h"
+#include "mlir/Analysis/Presburger/PresburgerSpace.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
+#include <cstdint>
+
+namespace mlir::presburger {
+using llvm::ArrayRef;
+using llvm::SmallVector;
+using llvm::SmallVectorImpl;
+
+/// This structure is central to the parser and flattener, and holds the number
+/// of dimensions, symbols, locals, and the constant term.
+struct ParseInfo {
+ unsigned numDims = 0;
+ unsigned numSymbols = 0;
+ unsigned numExprs = 0;
+ unsigned numDivs = 0;
+
+ constexpr unsigned getDimStartIdx() const { return 0; }
+ constexpr unsigned getSymbolStartIdx() const { return numDims; }
+ constexpr unsigned getLocalVarStartIdx() const {
+ return numDims + numSymbols;
+ }
+ constexpr unsigned getNumCols() const {
+ return numDims + numSymbols + numDivs + 1;
+ }
+ constexpr unsigned getConstantIdx() const { return getNumCols() - 1; }
+
+ constexpr bool isDimIdx(unsigned i) const { return i < getSymbolStartIdx(); }
+ constexpr bool isSymbolIdx(unsigned i) const {
+ return i >= getSymbolStartIdx() && i < getLocalVarStartIdx();
+ }
+ constexpr bool isLocalVarIdx(unsigned i) const {
+ return i >= getLocalVarStartIdx() && i < getConstantIdx();
+ }
+ constexpr bool isConstantIdx(unsigned i) const {
+ return i == getConstantIdx();
+ }
+};
+
+/// Helper for storing coefficients in canonical form: dims followed by symbols,
+/// followed by locals, and finally the constant term.
+///
+/// (x, y)[a, b]: y * 91 + x + 3 * a + 7
+/// coefficients: [1, 91, 3, 0, 7]
+struct CoefficientVector {
+ ParseInfo info;
+ SmallVector<int64_t, 8> coefficients;
+
+ CoefficientVector(const ParseInfo &info, int64_t c = 0) : info(info) {
+ coefficients.resize(info.getNumCols());
+ coefficients[info.getConstantIdx()] = c;
+ }
+
+ // Copyable and movable
+ CoefficientVector(const CoefficientVector &o) = default;
+ CoefficientVector &operator=(const CoefficientVector &o) = default;
+ CoefficientVector(CoefficientVector &&o)
+ : info(o.info), coefficients(std::move(o.coefficients)) {
+ o.coefficients.clear();
+ }
+
+ ArrayRef<int64_t> getCoefficients() const { return coefficients; }
+ int64_t getConstant() const { return coefficients[info.getConstantIdx()]; }
+ size_t size() const { return coefficients.size(); }
+ operator ArrayRef<int64_t>() const { return coefficients; }
+ void resize(size_t size) { coefficients.resize(size); }
+ operator bool() const {
+ return any_of(coefficients, [](int64_t c) { return c; });
+ }
+ int64_t &operator[](unsigned i) {
+ assert(i < coefficients.size());
+ return coefficients[i];
+ }
+ int64_t &back() { return coefficients.back(); }
+ int64_t back() const { return coefficients.back(); }
+ void clear() {
+ for_each(coefficients, [](auto &coeff) { coeff = 0; });
+ }
+
+ CoefficientVector &operator+=(const CoefficientVector &l) {
+ coefficients.resize(l.size());
+ for (auto [idx, c] : enumerate(l.getCoefficients()))
+ coefficients[idx] += c;
+ return *this;
+ }
+ CoefficientVector &operator*=(int64_t c) {
+ for_each(coefficients, [c](auto &coeff) { coeff *= c; });
+ return *this;
+ }
+ CoefficientVector &operator/=(int64_t c) {
+ assert(c && "Division by zero");
+ for_each(coefficients, [c](auto &coeff) { coeff /= c; });
+ return *this;
+ }
+
+ CoefficientVector operator+(const CoefficientVector &l) const {
+ CoefficientVector ret(*this);
+ return ret += l;
+ }
+ CoefficientVector operator*(int64_t c) const {
+ CoefficientVector ret(*this);
+ return ret *= c;
+ }
+ CoefficientVector operator/(int64_t c) const {
+ CoefficientVector ret(*this);
+ return ret /= c;
+ }
+
+ bool isConstant() const {
+ return all_of(drop_end(coefficients), [](int64_t c) { return !c; });
+ }
+ CoefficientVector getPadded(size_t newSize) const {
+ assert(newSize >= size() &&
+ "Padding size should be greater than expr size");
+ CoefficientVector ret(info);
+ ret.resize(newSize);
+
+ // Start constructing the result by taking the dims and symbols of the
+ // coefficients.
+ for (const auto &[col, coeff] : enumerate(drop_end(coefficients)))
+ ret[col] = coeff;
+
+ // Put the constant at the end.
+ ret.back() = back();
+ return ret;
+ }
+
+ uint64_t factorMulFromLinearTerm() const {
+ uint64_t gcd = 1;
+ for (int64_t val : coefficients)
+ gcd = std::gcd(gcd, std::abs(val));
+ return gcd;
+ }
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+ bool hasMultipleCoefficients() const {
+ return count_if(coefficients, [](auto &coeff) { return coeff; }) > 1;
+ }
+ LLVM_DUMP_METHOD void dump() const;
+#endif
+};
+
+enum class DimOrSymbolKind {
+ DimId,
+ Symbol,
+};
+
+using DimOrSymbolExpr = std::pair<DimOrSymbolKind, unsigned>;
+enum class DivKind { FloorDiv, Mod };
+
+/// Represents a pure Affine expression. Linear expressions are represented with
+/// divisor = 1, and no nestedDivTerms.
+///
+/// 3 - a * (3 + (3 - x div 3) div 4 + y div 7) div 4
+/// ^ linearDivident = 3, mulFactor = 1, divisor = 1
+/// ^ nest: 1, mulFactor: -a
+/// ^ nest: 1, linearDividend
+/// ^ nest: 2, linearDividend
+/// ^ nest: 3
+/// ^ nest: 2
+/// ^ nest: 2
+/// nest: 1, divisor ^
+///
+/// Where div = floordiv|mod; ceildiv is pre-reduced
+struct PureAffineExprImpl {
+ ParseInfo info;
+ DivKind kind = DivKind::FloorDiv;
+ using PureAffineExpr = std::unique_ptr<PureAffineExprImpl>;
+
+ int64_t mulFactor = 1;
+ CoefficientVector linearDividend;
+ int64_t divisor = 1;
+ SmallVector<PureAffineExpr, 4> nestedDivTerms;
----------------
Groverkss wrote:
I don't understand why you need a AST form of an affine expression. Why can't these operations be done directly on Presburger constructs?
https://github.com/llvm/llvm-project/pull/94916
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