llvm/llvm/lib/CodeGen/CriticalAntiDepBreaker.cpp

//===- CriticalAntiDepBreaker.cpp - Anti-dep breaker ----------------------===//
//
// 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 implements the CriticalAntiDepBreaker class, which
// implements register anti-dependence breaking along a blocks
// critical path during post-RA scheduler.
//
//===----------------------------------------------------------------------===//

#include "CriticalAntiDepBreaker.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <utility>

usingnamespacellvm;

#define DEBUG_TYPE …

CriticalAntiDepBreaker::CriticalAntiDepBreaker(MachineFunction &MFi,
                                               const RegisterClassInfo &RCI)
    : … { … }

CriticalAntiDepBreaker::~CriticalAntiDepBreaker() = default;

void CriticalAntiDepBreaker::StartBlock(MachineBasicBlock *BB) { … }

void CriticalAntiDepBreaker::FinishBlock() { … }

void CriticalAntiDepBreaker::Observe(MachineInstr &MI, unsigned Count,
                                     unsigned InsertPosIndex) { … }

/// CriticalPathStep - Return the next SUnit after SU on the bottom-up
/// critical path.
static const SDep *CriticalPathStep(const SUnit *SU) { … }

void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr &MI) { … }

void CriticalAntiDepBreaker::ScanInstruction(MachineInstr &MI, unsigned Count) { … }

// Check all machine operands that reference the antidependent register and must
// be replaced by NewReg. Return true if any of their parent instructions may
// clobber the new register.
//
// Note: AntiDepReg may be referenced by a two-address instruction such that
// it's use operand is tied to a def operand. We guard against the case in which
// the two-address instruction also defines NewReg, as may happen with
// pre/postincrement loads. In this case, both the use and def operands are in
// RegRefs because the def is inserted by PrescanInstruction and not erased
// during ScanInstruction. So checking for an instruction with definitions of
// both NewReg and AntiDepReg covers it.
bool
CriticalAntiDepBreaker::isNewRegClobberedByRefs(RegRefIter RegRefBegin,
                                                RegRefIter RegRefEnd,
                                                unsigned NewReg) { … }

unsigned CriticalAntiDepBreaker::
findSuitableFreeRegister(RegRefIter RegRefBegin,
                         RegRefIter RegRefEnd,
                         unsigned AntiDepReg,
                         unsigned LastNewReg,
                         const TargetRegisterClass *RC,
                         SmallVectorImpl<unsigned> &Forbid) { … }

unsigned CriticalAntiDepBreaker::
BreakAntiDependencies(const std::vector<SUnit> &SUnits,
                      MachineBasicBlock::iterator Begin,
                      MachineBasicBlock::iterator End,
                      unsigned InsertPosIndex,
                      DbgValueVector &DbgValues) { … }

AntiDepBreaker *
llvm::createCriticalAntiDepBreaker(MachineFunction &MFi,
                                   const RegisterClassInfo &RCI) { … }