lib/Target/AArch64/AArch64PreLegalizerCombiner.cpp

//=== lib/CodeGen/GlobalISel/AArch64PreLegalizerCombiner.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 "AArch64TargetMachine.h"
#include "llvm/CodeGen/GlobalISel/Combiner.h"
#include "llvm/CodeGen/GlobalISel/CombinerHelper.h"
#include "llvm/CodeGen/GlobalISel/CombinerInfo.h"
#include "llvm/CodeGen/GlobalISel/GISelKnownBits.h"
#include "llvm/CodeGen/GlobalISel/MIPatternMatch.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/Support/Debug.h"

#define DEBUG_TYPE "aarch64-prelegalizer-combiner"

using namespace llvm;
using namespace MIPatternMatch;

namespace {
class AArch64PreLegalizerCombinerInfo : public CombinerInfo {
  GISelKnownBits *KB;

public:
  AArch64PreLegalizerCombinerInfo(bool EnableOpt, bool OptSize, bool MinSize,
                                  GISelKnownBits *KB)
      : CombinerInfo(/*AllowIllegalOps*/ true, /*ShouldLegalizeIllegal*/ false,
                     /*LegalizerInfo*/ nullptr, EnableOpt, OptSize, MinSize),
        KB(KB) {}
  virtual bool combine(GISelChangeObserver &Observer, MachineInstr &MI,
                       MachineIRBuilder &B) const override;
};

bool AArch64PreLegalizerCombinerInfo::combine(GISelChangeObserver &Observer,
                                              MachineInstr &MI,
                                              MachineIRBuilder &B) const {
  CombinerHelper Helper(Observer, B, KB);

  switch (MI.getOpcode()) {
  default:
    return false;
  case TargetOpcode::COPY:
    return Helper.tryCombineCopy(MI);
  case TargetOpcode::G_BR:
    return Helper.tryCombineBr(MI);
  case TargetOpcode::G_LOAD:
  case TargetOpcode::G_SEXTLOAD:
  case TargetOpcode::G_ZEXTLOAD:
    return Helper.tryCombineExtendingLoads(MI);
  case TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS:
    switch (MI.getIntrinsicID()) {
    case Intrinsic::memcpy:
    case Intrinsic::memmove:
    case Intrinsic::memset: {
      // If we're at -O0 set a maxlen of 32 to inline, otherwise let the other
      // heuristics decide.
      unsigned MaxLen = EnableOpt ? 0 : 32;
      // Try to inline memcpy type calls if optimizations are enabled.
      return (!EnableOptSize) ? Helper.tryCombineMemCpyFamily(MI, MaxLen)
                              : false;
    }
    default:
      break;
    }
  }

  return false;
}

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

class AArch64PreLegalizerCombiner : public MachineFunctionPass {
public:
  static char ID;

  AArch64PreLegalizerCombiner();

  StringRef getPassName() const override { return "AArch64PreLegalizerCombiner"; }

  bool runOnMachineFunction(MachineFunction &MF) override;

  void getAnalysisUsage(AnalysisUsage &AU) const override;
};
}

void AArch64PreLegalizerCombiner::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.addRequired<TargetPassConfig>();
  AU.setPreservesCFG();
  getSelectionDAGFallbackAnalysisUsage(AU);
  AU.addRequired<GISelKnownBitsAnalysis>();
  AU.addPreserved<GISelKnownBitsAnalysis>();
  MachineFunctionPass::getAnalysisUsage(AU);
}

AArch64PreLegalizerCombiner::AArch64PreLegalizerCombiner() : MachineFunctionPass(ID) {
  initializeAArch64PreLegalizerCombinerPass(*PassRegistry::getPassRegistry());
}

bool AArch64PreLegalizerCombiner::runOnMachineFunction(MachineFunction &MF) {
  if (MF.getProperties().hasProperty(
          MachineFunctionProperties::Property::FailedISel))
    return false;
  auto *TPC = &getAnalysis<TargetPassConfig>();
  const Function &F = MF.getFunction();
  bool EnableOpt =
      MF.getTarget().getOptLevel() != CodeGenOpt::None && !skipFunction(F);
  GISelKnownBits *KB = &getAnalysis<GISelKnownBitsAnalysis>().get(MF);
  AArch64PreLegalizerCombinerInfo PCInfo(EnableOpt, F.hasOptSize(),
                                         F.hasMinSize(), KB);
  Combiner C(PCInfo, TPC);
  return C.combineMachineInstrs(MF, /*CSEInfo*/ nullptr);
}

char AArch64PreLegalizerCombiner::ID = 0;
INITIALIZE_PASS_BEGIN(AArch64PreLegalizerCombiner, DEBUG_TYPE,
                      "Combine AArch64 machine instrs before legalization",
                      false, false)
INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
INITIALIZE_PASS_DEPENDENCY(GISelKnownBitsAnalysis)
INITIALIZE_PASS_END(AArch64PreLegalizerCombiner, DEBUG_TYPE,
                    "Combine AArch64 machine instrs before legalization", false,
                    false)


namespace llvm {
FunctionPass *createAArch64PreLegalizeCombiner() {
  return new AArch64PreLegalizerCombiner();
}
} // end namespace llvm