text: //===-- BPFTargetMachine.cpp - Define TargetMachine for BPF ---------------===//
  //
  // 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
  //
  //===----------------------------------------------------------------------===//
  //
  // Implements the info about BPF target spec.
  //
  //===----------------------------------------------------------------------===//
  
  #include "BPFTargetMachine.h"
  #include "BPF.h"
  #include "MCTargetDesc/BPFMCAsmInfo.h"
  #include "TargetInfo/BPFTargetInfo.h"
  #include "llvm/CodeGen/Passes.h"
  #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
  #include "llvm/CodeGen/TargetPassConfig.h"
  #include "llvm/IR/LegacyPassManager.h"
  #include "llvm/Support/FormattedStream.h"
  #include "llvm/Support/TargetRegistry.h"
  #include "llvm/Target/TargetOptions.h"
  using namespace llvm;
  
  static cl::
  opt<bool> DisableMIPeephole("disable-bpf-peephole", cl::Hidden,
                              cl::desc("Disable machine peepholes for BPF"));
  
  extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeBPFTarget() {
    // Register the target.
    RegisterTargetMachine<BPFTargetMachine> X(getTheBPFleTarget());
    RegisterTargetMachine<BPFTargetMachine> Y(getTheBPFbeTarget());
    RegisterTargetMachine<BPFTargetMachine> Z(getTheBPFTarget());
  
    PassRegistry &PR = *PassRegistry::getPassRegistry();
    initializeBPFAbstractMemberAccessPass(PR);
    initializeBPFMIPeepholePass(PR);
    initializeBPFMIPeepholeTruncElimPass(PR);
  }
  
  // DataLayout: little or big endian
  static std::string computeDataLayout(const Triple &TT) {
    if (TT.getArch() == Triple::bpfeb)
      return "E-m:e-p:64:64-i64:64-n32:64-S128";
    else
      return "e-m:e-p:64:64-i64:64-n32:64-S128";
  }
  
  static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
    if (!RM.hasValue())
      return Reloc::PIC_;
    return *RM;
  }
  
  BPFTargetMachine::BPFTargetMachine(const Target &T, const Triple &TT,
                                     StringRef CPU, StringRef FS,
                                     const TargetOptions &Options,
                                     Optional<Reloc::Model> RM,
                                     Optional<CodeModel::Model> CM,
                                     CodeGenOpt::Level OL, bool JIT)
      : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
                          getEffectiveRelocModel(RM),
                          getEffectiveCodeModel(CM, CodeModel::Small), OL),
        TLOF(std::make_unique<TargetLoweringObjectFileELF>()),
        Subtarget(TT, std::string(CPU), std::string(FS), *this) {
    initAsmInfo();
  
    BPFMCAsmInfo *MAI =
        static_cast<BPFMCAsmInfo *>(const_cast<MCAsmInfo *>(AsmInfo.get()));
    MAI->setDwarfUsesRelocationsAcrossSections(!Subtarget.getUseDwarfRIS());
  }
  
  namespace {
  // BPF Code Generator Pass Configuration Options.
  class BPFPassConfig : public TargetPassConfig {
  public:
    BPFPassConfig(BPFTargetMachine &TM, PassManagerBase &PM)
        : TargetPassConfig(TM, PM) {}
  
    BPFTargetMachine &getBPFTargetMachine() const {
      return getTM<BPFTargetMachine>();
    }
  
    void addIRPasses() override;
    bool addInstSelector() override;
    void addMachineSSAOptimization() override;
    void addPreEmitPass() override;
  };
  }
  
  TargetPassConfig *BPFTargetMachine::createPassConfig(PassManagerBase &PM) {
    return new BPFPassConfig(*this, PM);
  }
  
  void BPFPassConfig::addIRPasses() {
  
    addPass(createBPFAbstractMemberAccess(&getBPFTargetMachine()));
  
    TargetPassConfig::addIRPasses();
  }
  
  // Install an instruction selector pass using
  // the ISelDag to gen BPF code.
  bool BPFPassConfig::addInstSelector() {
    addPass(createBPFISelDag(getBPFTargetMachine()));
  
    return false;
  }
  
  void BPFPassConfig::addMachineSSAOptimization() {
    addPass(createBPFMISimplifyPatchablePass());
  
    // The default implementation must be called first as we want eBPF
    // Peephole ran at last.
    TargetPassConfig::addMachineSSAOptimization();
  
    const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
    if (!DisableMIPeephole) {
      if (Subtarget->getHasAlu32())
        addPass(createBPFMIPeepholePass());
      addPass(createBPFMIPeepholeTruncElimPass());
    }
  }
  
  void BPFPassConfig::addPreEmitPass() {
    addPass(createBPFMIPreEmitCheckingPass());
    if (getOptLevel() != CodeGenOpt::None)
      if (!DisableMIPeephole)
        addPass(createBPFMIPreEmitPeepholePass());
  }
  