llvm/mlir/lib/Transforms/Utils/LoopInvariantCodeMotionUtils.cpp

//===- LoopInvariantCodeMotionUtils.cpp - LICM Utils ------------*- 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
//
//===----------------------------------------------------------------------===//
//
// This file contains the implementation of the core LICM algorithm.
//
//===----------------------------------------------------------------------===//

#include "mlir/Transforms/LoopInvariantCodeMotionUtils.h"

#include "mlir/IR/Operation.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/Interfaces/LoopLikeInterface.h"
#include "mlir/Interfaces/SideEffectInterfaces.h"
#include "mlir/Interfaces/SubsetOpInterface.h"
#include "llvm/Support/Debug.h"
#include <queue>

#define DEBUG_TYPE …

usingnamespacemlir;

/// Checks whether the given op can be hoisted by checking that
/// - the op and none of its contained operations depend on values inside of the
///   loop (by means of calling definedOutside).
/// - the op has no side-effects.
static bool canBeHoisted(Operation *op,
                         function_ref<bool(OpOperand &)> condition) { … }

static bool canBeHoisted(Operation *op,
                         function_ref<bool(Value)> definedOutside) { … }

size_t mlir::moveLoopInvariantCode(
    ArrayRef<Region *> regions,
    function_ref<bool(Value, Region *)> isDefinedOutsideRegion,
    function_ref<bool(Operation *, Region *)> shouldMoveOutOfRegion,
    function_ref<void(Operation *, Region *)> moveOutOfRegion) { … }

size_t mlir::moveLoopInvariantCode(LoopLikeOpInterface loopLike) { … }

namespace {
/// Helper data structure that keeps track of equivalent/disjoint subset ops.
class MatchingSubsets { … };
} // namespace

/// If the given value has a single use by an op that is a terminator, return
/// that use. Otherwise, return nullptr.
static OpOperand *getSingleTerminatorUse(Value value) { … }

LogicalResult
MatchingSubsets::populateSubsetOpsAtIterArg(LoopLikeOpInterface loopLike,
                                            BlockArgument iterArg,
                                            bool collectHoistableOps) { … }

/// Hoist all subset ops that operate on the idx-th region iter_arg of the given
/// loop-like op and index into loop-invariant subset locations. Return the
/// newly created loop op (that has extra iter_args) or the original loop op if
/// nothing was hoisted.
static LoopLikeOpInterface hoistSubsetAtIterArg(RewriterBase &rewriter,
                                                LoopLikeOpInterface loopLike,
                                                BlockArgument iterArg) { … }

LoopLikeOpInterface
mlir::hoistLoopInvariantSubsets(RewriterBase &rewriter,
                                LoopLikeOpInterface loopLike) { … }