llvm/mlir/lib/Dialect/Linalg/Transforms/EraseUnusedOperandsAndResults.cpp

//===- EraseUnusedOperandsAndResults.cpp ----------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "mlir/Dialect/Linalg/Transforms/Transforms.h"

#include "mlir/Dialect/Linalg/IR/Linalg.h"

usingnamespacemlir;
usingnamespacemlir::linalg;

/// Return `true` if the `result` of an operation `genericOp` is dead.
static bool isResultValueDead(linalg::GenericOp genericOp, OpResult result) { … }

namespace {

struct DeduplicateAndRemoveDeadOperandsAndResults
    : public OpRewritePattern<GenericOp> { … };

/// Remove unused cycles.
/// We can remove unused cycle within a payload of generic region
/// if these conditions are met:
/// - Result from out operand is dead.
/// - Block arg from out operand has a single use in the %cycle
/// instruction.
/// - Cycle has a single use and it is in yield.
struct RemoveUnusedCycleInGenericOp : public OpRewritePattern<GenericOp> { … };

/// Fold uses of duplicate inputs in the body of a linalg.generic. E.g.:
/// ```
/// linalg.generic ins(%a, %b, %a, %b) outs(%a)
/// ^bb0(%in0, %in1, %in2, %in3, %out1)
/// ```
/// Assuming that all %a and %b have the same index map:
/// * All uses of %in0 and %in2 are replaced with %out1
/// * All uses of %in1 are replaced with %in3
/// This pattern can enable additional canonicalizations: In the above example,
/// %in0, %in1 and %in3 have no uses anymore and their corresponding operands
/// can be folded away. This pattern does not modify uses of output block args.
struct FoldDuplicateInputBbArgs : public OpRewritePattern<GenericOp> { … };

} // namespace

void mlir::linalg::populateEraseUnusedOperandsAndResultsPatterns(
    RewritePatternSet &patterns) { … }

void mlir::linalg::populateEraseUnnecessaryInputsPatterns(
    RewritePatternSet &patterns) { … }