llvm/mlir/include/mlir/Transforms/OneToNTypeConversion.h

//===-- OneToNTypeConversion.h - Utils for 1:N type conversion --*- C++ -*-===//
//
// Licensed 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
//
//===----------------------------------------------------------------------===//
//
// This file provides utils for implementing (poor-man's) dialect conversion
// passes with 1:N type conversions.
//
// The main function, `applyPartialOneToNConversion`, first applies a set of
// `RewritePattern`s, which produce unrealized casts to convert the operands and
// results from and to the source types, and then replaces all newly added
// unrealized casts by user-provided materializations. For this to work, the
// main function requires a special `TypeConverter`, a special
// `PatternRewriter`, and special RewritePattern`s, which extend their
// respective base classes for 1:N type converions.
//
// Note that this is much more simple-minded than the "real" dialect conversion,
// which checks for legality before applying patterns and does probably many
// other additional things. Ideally, some of the extensions here could be
// integrated there.
//
//===----------------------------------------------------------------------===//

#ifndef MLIR_TRANSFORMS_ONETONTYPECONVERSION_H
#define MLIR_TRANSFORMS_ONETONTYPECONVERSION_H

#include "mlir/IR/PatternMatch.h"
#include "mlir/Transforms/DialectConversion.h"
#include "llvm/ADT/SmallVector.h"

namespace mlir {

/// Extends `TypeConverter` with 1:N target materializations. Such
/// materializations have to provide the "reverse" of 1:N type conversions,
/// i.e., they need to materialize N values with target types into one value
/// with a source type (which isn't possible in the base class currently).
class OneToNTypeConverter : public TypeConverter { … };

/// Stores a 1:N mapping of types and provides several useful accessors. This
/// class extends `SignatureConversion`, which already supports 1:N type
/// mappings but lacks some accessors into the mapping as well as access to the
/// original types.
class OneToNTypeMapping : public TypeConverter::SignatureConversion { … };

/// Extends the basic `RewritePattern` class with a type converter member and
/// some accessors to it. This is useful for patterns that are not
/// `ConversionPattern`s but still require access to a type converter.
class RewritePatternWithConverter : public mlir::RewritePattern { … };

/// Specialization of `PatternRewriter` that `OneToNConversionPattern`s use. The
/// class provides additional rewrite methods that are specific to 1:N type
/// conversions.
class OneToNPatternRewriter : public PatternRewriter { … };

/// Base class for patterns with 1:N type conversions. Derived classes have to
/// overwrite the `matchAndRewrite` overlaod that provides additional
/// information for 1:N type conversions.
class OneToNConversionPattern : public RewritePatternWithConverter { … };

/// This class is a wrapper around `OneToNConversionPattern` for matching
/// against instances of a particular op class.
template <typename SourceOp>
class OneToNOpConversionPattern : public OneToNConversionPattern { … };

/// Applies the given set of patterns recursively on the given op and adds user
/// materializations where necessary. The patterns are expected to be
/// `OneToNConversionPattern`, which help converting the types of the operands
/// and results of the matched ops. The provided type converter is used to
/// convert the operands of matched ops from their original types to operands
/// with different types. Unlike in `DialectConversion`, this supports 1:N type
/// conversions. Those conversions at the "boundary" of the pattern application,
/// where converted results are not consumed by replaced ops that expect the
/// converted operands or vice versa, the function inserts user materializations
/// from the type converter. Also unlike `DialectConversion`, there are no legal
/// or illegal types; the function simply applies the given patterns and does
/// not fail if some ops or types remain unconverted (i.e., the conversion is
/// only "partial").
LogicalResult
applyPartialOneToNConversion(Operation *op, OneToNTypeConverter &typeConverter,
                             const FrozenRewritePatternSet &patterns);

/// Add a pattern to the given pattern list to convert the signature of a
/// FunctionOpInterface op with the given type converter. This only supports
/// ops which use FunctionType to represent their type. This is intended to be
/// used with the 1:N dialect conversion.
void populateOneToNFunctionOpInterfaceTypeConversionPattern(
    StringRef functionLikeOpName, TypeConverter &converter,
    RewritePatternSet &patterns);
template <typename FuncOpT>
void populateOneToNFunctionOpInterfaceTypeConversionPattern(
    TypeConverter &converter, RewritePatternSet &patterns) { … }

} // namespace mlir

#endif // MLIR_TRANSFORMS_ONETONTYPECONVERSION_H