llvm/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp

//===-- PPCCTRLoops.cpp - Generate CTR loops ------------------------------===//
//
// 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 generates machine instructions for the CTR loops related pseudos:
// 1: MTCTRloop/DecreaseCTRloop
// 2: MTCTR8loop/DecreaseCTR8loop
//
// If a CTR loop can be generated:
// 1: MTCTRloop/MTCTR8loop will be converted to "mtctr"
// 2: DecreaseCTRloop/DecreaseCTR8loop will be converted to "bdnz/bdz" and
//    its user branch instruction can be deleted.
//
// If a CTR loop can not be generated due to clobber of CTR:
// 1: MTCTRloop/MTCTR8loop can be deleted.
// 2: DecreaseCTRloop/DecreaseCTR8loop will be converted to "addi -1" and
//    a "cmplwi/cmpldi".
//
// This pass runs just before register allocation, because we don't want
// register allocator to allocate register for DecreaseCTRloop if a CTR can be
// generated or if a CTR loop can not be generated, we don't have any condition
// register for the new added "cmplwi/cmpldi".
//
//===----------------------------------------------------------------------===//

#include "PPC.h"
#include "PPCInstrInfo.h"
#include "PPCSubtarget.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Register.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/PassRegistry.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include <cassert>

usingnamespacellvm;

#define DEBUG_TYPE …

STATISTIC(NumCTRLoops, "Number of CTR loops generated");
STATISTIC(NumNormalLoops, "Number of normal compare + branch loops generated");

namespace {
class PPCCTRLoops : public MachineFunctionPass { … };
} // namespace

char PPCCTRLoops::ID = …;

INITIALIZE_PASS_BEGIN(PPCCTRLoops, DEBUG_TYPE, "PowerPC CTR loops generation",
                      false, false)
INITIALIZE_PASS_DEPENDENCY(MachineLoopInfoWrapperPass)
INITIALIZE_PASS_END(PPCCTRLoops, DEBUG_TYPE, "PowerPC CTR loops generation",
                    false, false)

FunctionPass *llvm::createPPCCTRLoopsPass() { … }

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

bool PPCCTRLoops::isCTRClobber(MachineInstr *MI, bool CheckReads) const { … }

bool PPCCTRLoops::processLoop(MachineLoop *ML) { … }

void PPCCTRLoops::expandNormalLoops(MachineLoop *ML, MachineInstr *Start,
                                    MachineInstr *Dec) { … }

void PPCCTRLoops::expandCTRLoops(MachineLoop *ML, MachineInstr *Start,
                                 MachineInstr *Dec) { … }