llvm/llvm/lib/Target/RISCV/RISCVRedundantCopyElimination.cpp

//=- RISCVRedundantCopyElimination.cpp - Remove useless copy for RISC-V -----=//
//
// 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 pass removes unnecessary zero copies in BBs that are targets of
// beqz/bnez instructions. For instance, the copy instruction in the code below
// can be removed because the beqz jumps to BB#2 when a0 is zero.
//  BB#1:
//    beqz %a0, <BB#2>
//  BB#2:
//    %a0 = COPY %x0
// This pass should be run after register allocation.
//
// This pass is based on the earliest versions of
// AArch64RedundantCopyElimination.
//
// FIXME: Support compares with constants other than zero? This is harder to
// do on RISC-V since branches can't have immediates.
//
//===----------------------------------------------------------------------===//

#include "RISCV.h"
#include "RISCVInstrInfo.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/Debug.h"

usingnamespacellvm;

#define DEBUG_TYPE …

STATISTIC(NumCopiesRemoved, "Number of copies removed.");

namespace {
class RISCVRedundantCopyElimination : public MachineFunctionPass { … };

} // end anonymous namespace

char RISCVRedundantCopyElimination::ID = …;

INITIALIZE_PASS(…)

static bool
guaranteesZeroRegInBlock(MachineBasicBlock &MBB,
                         const SmallVectorImpl<MachineOperand> &Cond,
                         MachineBasicBlock *TBB) { … }

bool RISCVRedundantCopyElimination::optimizeBlock(MachineBasicBlock &MBB) { … }

bool RISCVRedundantCopyElimination::runOnMachineFunction(MachineFunction &MF) { … }

FunctionPass *llvm::createRISCVRedundantCopyEliminationPass() { … }