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//===- RISCVMacroFusion.cpp - RISCV Macro Fusion --------------------------===//
//
// 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 This file contains the RISCV implementation of the DAG scheduling
/// mutation to pair instructions back to back.
//
//===----------------------------------------------------------------------===//
//
#include "RISCVMacroFusion.h"
#include "RISCVSubtarget.h"
#include "llvm/CodeGen/MacroFusion.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
using namespace llvm;
// Fuse LUI followed by ADDI or ADDIW.
// rd = imm[31:0] which decomposes to
// lui rd, imm[31:12]
// addi(w) rd, rd, imm[11:0]
static bool isLUIADDI(const MachineInstr *FirstMI,
const MachineInstr &SecondMI) {
if (SecondMI.getOpcode() != RISCV::ADDI &&
SecondMI.getOpcode() != RISCV::ADDIW)
return false;
// Assume the 1st instr to be a wildcard if it is unspecified.
if (!FirstMI)
return true;
if (FirstMI->getOpcode() != RISCV::LUI)
return false;
// The first operand of ADDI might be a frame index.
if (!SecondMI.getOperand(1).isReg())
return false;
Register FirstDest = FirstMI->getOperand(0).getReg();
// Destination of LUI should be the ADDI(W) source register.
if (SecondMI.getOperand(1).getReg() != FirstDest)
return false;
// If the input is virtual make sure this is the only user.
if (FirstDest.isVirtual()) {
auto &MRI = SecondMI.getMF()->getRegInfo();
return MRI.hasOneNonDBGUse(FirstDest);
}
// If the FirstMI destination is non-virtual, it should match the SecondMI
// destination.
return SecondMI.getOperand(0).getReg() == FirstDest;
}
static bool shouldScheduleAdjacent(const TargetInstrInfo &TII,
const TargetSubtargetInfo &TSI,
const MachineInstr *FirstMI,
const MachineInstr &SecondMI) {
const RISCVSubtarget &ST = static_cast<const RISCVSubtarget &>(TSI);
if (ST.hasLUIADDIFusion() && isLUIADDI(FirstMI, SecondMI))
return true;
return false;
}
std::unique_ptr<ScheduleDAGMutation> llvm::createRISCVMacroFusionDAGMutation() {
return createMacroFusionDAGMutation(shouldScheduleAdjacent);
}
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