lib/Target/Mips/MipsPreLegalizerCombiner.cpp

//=== lib/CodeGen/GlobalISel/MipsPreLegalizerCombiner.cpp --------------===//
//
// 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 does combining of machine instructions at the generic MI level,
// before the legalizer.
//
//===----------------------------------------------------------------------===//

#include "MipsTargetMachine.h"
#include "llvm/CodeGen/GlobalISel/Combiner.h"
#include "llvm/CodeGen/GlobalISel/CombinerHelper.h"
#include "llvm/CodeGen/GlobalISel/CombinerInfo.h"
#include "llvm/CodeGen/GlobalISel/MIPatternMatch.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/InitializePasses.h"

#define DEBUG_TYPE "mips-prelegalizer-combiner"

using namespace llvm;

namespace {
class MipsPreLegalizerCombinerInfo : public CombinerInfo {
public:
  MipsPreLegalizerCombinerInfo()
      : CombinerInfo(/*AllowIllegalOps*/ true, /*ShouldLegalizeIllegal*/ false,
                     /*LegalizerInfo*/ nullptr, /*EnableOpt*/ false,
                     /*EnableOptSize*/ false, /*EnableMinSize*/ false) {}
  virtual bool combine(GISelChangeObserver &Observer, MachineInstr &MI,
                       MachineIRBuilder &B) const override;
};

bool MipsPreLegalizerCombinerInfo::combine(GISelChangeObserver &Observer,
                                           MachineInstr &MI,
                                           MachineIRBuilder &B) const {
  CombinerHelper Helper(Observer, B);

  switch (MI.getOpcode()) {
  default:
    return false;
  case TargetOpcode::G_LOAD:
  case TargetOpcode::G_SEXTLOAD:
  case TargetOpcode::G_ZEXTLOAD: {
    // Don't attempt to combine non power of 2 loads or unaligned loads when
    // subtarget doesn't support them.
    auto MMO = *MI.memoperands_begin();
    const MipsSubtarget &STI =
        static_cast<const MipsSubtarget &>(MI.getMF()->getSubtarget());
    if (!isPowerOf2_64(MMO->getSize()))
      return false;
    bool isUnaligned = MMO->getAlign() < MMO->getSize();
    if (!STI.systemSupportsUnalignedAccess() && isUnaligned)
      return false;

    return Helper.tryCombineExtendingLoads(MI);
  }
  }

  return false;
}

// Pass boilerplate
// ================

class MipsPreLegalizerCombiner : public MachineFunctionPass {
public:
  static char ID;

  MipsPreLegalizerCombiner();

  StringRef getPassName() const override { return "MipsPreLegalizerCombiner"; }

  bool runOnMachineFunction(MachineFunction &MF) override;

  void getAnalysisUsage(AnalysisUsage &AU) const override;
};
} // end anonymous namespace

void MipsPreLegalizerCombiner::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.addRequired<TargetPassConfig>();
  AU.setPreservesCFG();
  getSelectionDAGFallbackAnalysisUsage(AU);
  MachineFunctionPass::getAnalysisUsage(AU);
}

MipsPreLegalizerCombiner::MipsPreLegalizerCombiner() : MachineFunctionPass(ID) {
  initializeMipsPreLegalizerCombinerPass(*PassRegistry::getPassRegistry());
}

bool MipsPreLegalizerCombiner::runOnMachineFunction(MachineFunction &MF) {
  if (MF.getProperties().hasProperty(
          MachineFunctionProperties::Property::FailedISel))
    return false;
  auto *TPC = &getAnalysis<TargetPassConfig>();
  MipsPreLegalizerCombinerInfo PCInfo;
  Combiner C(PCInfo, TPC);
  return C.combineMachineInstrs(MF, nullptr);
}

char MipsPreLegalizerCombiner::ID = 0;
INITIALIZE_PASS_BEGIN(MipsPreLegalizerCombiner, DEBUG_TYPE,
                      "Combine Mips machine instrs before legalization", false,
                      false)
INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
INITIALIZE_PASS_END(MipsPreLegalizerCombiner, DEBUG_TYPE,
                    "Combine Mips machine instrs before legalization", false,
                    false)

namespace llvm {
FunctionPass *createMipsPreLegalizeCombiner() {
  return new MipsPreLegalizerCombiner();
}
} // end namespace llvm