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// Copyright 2013 Google Inc. All Rights Reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// Declares the interface for transform policy objects. The policy object is
// used to configure and guide the behaviour of the transformation process
// applied to a block-graph. The concepts in here are general for block-graphs,
// regardless of the image format or machine format of the underlying data.
#include "syzygy/block_graph/block_graph.h"
namespace block_graph {
// The interface that guides image and basic-block decomposition decisions.
class TransformPolicyInterface {
virtual ~TransformPolicyInterface() { }
// This brings in a few types for the convenience of implementations of this
// class.
typedef block_graph::BlockGraph BlockGraph;
// Determines if the given block is safe for basic-block decomposition.
// @param block The block to evaluate.
// @returns true if it is safe to basic block decompose the given block,
// false otherwise.
virtual bool BlockIsSafeToBasicBlockDecompose(
const BlockGraph::Block* block) const = 0;
// Returns true if the given references @p ref from @p referrer may be safely
// redirected. If both the referrer and the referenced blocks are irregular
// in any way we cannot safely assume that @p reference has call semantics,
// i.e., where a return address is at the top of stack at entry. For any
// instrumentation or manipulation that uses return address swizzling,
// instrumenting an unsafe reference generally leads to crashes.
// @param referrer The block containing the reference.
// @param reference The reference itself.
// @returns true if the reference is safe and may be thunked, false otherwise.
virtual bool ReferenceIsSafeToRedirect(
const BlockGraph::Block* referrer,
const BlockGraph::Reference& reference) const = 0;
} // namespace block_graph