mlir/lib/Transforms/Utils/SideEffectUtils.cpp

//===- SideEffectUtils.cpp - Side Effect 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
//
//===----------------------------------------------------------------------===//

#include "mlir/Transforms/SideEffectUtils.h"
#include "mlir/IR/Operation.h"
#include "mlir/Interfaces/SideEffectInterfaces.h"

using namespace mlir;

bool mlir::isSideEffectFree(Operation *op) {
  if (auto memInterface = dyn_cast<MemoryEffectOpInterface>(op)) {
    // If the op has side-effects, it cannot be moved.
    if (!memInterface.hasNoEffect())
      return false;
    // If the op does not have recursive side effects, then it can be moved.
    if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>())
      return true;
  } else if (!op->hasTrait<OpTrait::HasRecursiveSideEffects>()) {
    // Otherwise, if the op does not implement the memory effect interface and
    // it does not have recursive side effects, then it cannot be known that the
    // op is moveable.
    return false;
  }

  // Recurse into the regions and ensure that all nested ops can also be moved.
  for (Region &region : op->getRegions())
    for (Operation &op : region.getOps())
      if (!isSideEffectFree(&op))
        return false;
  return true;
}