llvm/llvm/include/llvm/CodeGen/DetectDeadLanes.h

//===- DetectDeadLanes.h - SubRegister Lane Usage Analysis --*- 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
//
//===----------------------------------------------------------------------===//
//
/// \file
/// Analysis that tracks defined/used subregister lanes across COPY instructions
/// and instructions that get lowered to a COPY (PHI, REG_SEQUENCE,
/// INSERT_SUBREG, EXTRACT_SUBREG).
/// The information is used to detect dead definitions and the usage of
/// (completely) undefined values and mark the operands as such.
/// This pass is necessary because the dead/undef status is not obvious anymore
/// when subregisters are involved.
///
/// Example:
///    %0 = some definition
///    %1 = IMPLICIT_DEF
///    %2 = REG_SEQUENCE %0, sub0, %1, sub1
///    %3 = EXTRACT_SUBREG %2, sub1
///       = use %3
/// The %0 definition is dead and %3 contains an undefined value.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_DETECTDEADLANES_H
#define LLVM_CODEGEN_DETECTDEADLANES_H

#include "llvm/ADT/BitVector.h"
#include "llvm/MC/LaneBitmask.h"
#include <deque>

namespace llvm {

class MachineInstr;
class MachineOperand;
class MachineRegisterInfo;
class TargetRegisterInfo;

class DeadLaneDetector { … };

} // end namespace llvm

#endif // LLVM_CODEGEN_DETECTDEADLANES_H