llvm/llvm/include/llvm/Analysis/InstructionPrecedenceTracking.h

//===-- InstructionPrecedenceTracking.h -------------------------*- 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
//
//===----------------------------------------------------------------------===//
// Implements a class that is able to define some instructions as "special"
// (e.g. as having implicit control flow, or writing memory, or having another
// interesting property) and then efficiently answers queries of the types:
// 1. Are there any special instructions in the block of interest?
// 2. Return first of the special instructions in the given block;
// 3. Check if the given instruction is preceeded by the first special
//    instruction in the same block.
// The class provides caching that allows to answer these queries quickly. The
// user must make sure that the cached data is invalidated properly whenever
// a content of some tracked block is changed.
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_INSTRUCTIONPRECEDENCETRACKING_H
#define LLVM_ANALYSIS_INSTRUCTIONPRECEDENCETRACKING_H

#include "llvm/ADT/DenseMap.h"

namespace llvm {

class BasicBlock;
class Instruction;

class InstructionPrecedenceTracking { … };

/// This class allows to keep track on instructions with implicit control flow.
/// These are instructions that may not pass execution to their successors. For
/// example, throwing calls and guards do not always do this. If we need to know
/// for sure that some instruction is guaranteed to execute if the given block
/// is reached, then we need to make sure that there is no implicit control flow
/// instruction (ICFI) preceding it. For example, this check is required if we
/// perform PRE moving non-speculable instruction to other place.
class ImplicitControlFlowTracking : public InstructionPrecedenceTracking { … };

class MemoryWriteTracking : public InstructionPrecedenceTracking { … };

} // llvm

#endif // LLVM_ANALYSIS_INSTRUCTIONPRECEDENCETRACKING_H