BPFTargetMachine.cpp revision 360784 
1//===-- BPFTargetMachine.cpp - Define TargetMachine for BPF ---------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// Implements the info about BPF target spec.
10//
11//===----------------------------------------------------------------------===//
12
13#include "BPFTargetMachine.h"
14#include "BPF.h"
15#include "MCTargetDesc/BPFMCAsmInfo.h"
16#include "TargetInfo/BPFTargetInfo.h"
17#include "llvm/CodeGen/Passes.h"
18#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
19#include "llvm/CodeGen/TargetPassConfig.h"
20#include "llvm/IR/LegacyPassManager.h"
21#include "llvm/Support/FormattedStream.h"
22#include "llvm/Support/TargetRegistry.h"
23#include "llvm/Target/TargetOptions.h"
24using namespace llvm;
25
26static cl::
27opt<bool> DisableMIPeephole("disable-bpf-peephole", cl::Hidden,
28                            cl::desc("Disable machine peepholes for BPF"));
29
30extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeBPFTarget() {
31  // Register the target.
32  RegisterTargetMachine<BPFTargetMachine> X(getTheBPFleTarget());
33  RegisterTargetMachine<BPFTargetMachine> Y(getTheBPFbeTarget());
34  RegisterTargetMachine<BPFTargetMachine> Z(getTheBPFTarget());
35
36  PassRegistry &PR = *PassRegistry::getPassRegistry();
37  initializeBPFAbstractMemberAccessPass(PR);
38  initializeBPFMIPeepholePass(PR);
39  initializeBPFMIPeepholeTruncElimPass(PR);
40}
41
42// DataLayout: little or big endian
43static std::string computeDataLayout(const Triple &TT) {
44  if (TT.getArch() == Triple::bpfeb)
45    return "E-m:e-p:64:64-i64:64-n32:64-S128";
46  else
47    return "e-m:e-p:64:64-i64:64-n32:64-S128";
48}
49
50static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
51  if (!RM.hasValue())
52    return Reloc::PIC_;
53  return *RM;
54}
55
56BPFTargetMachine::BPFTargetMachine(const Target &T, const Triple &TT,
57                                   StringRef CPU, StringRef FS,
58                                   const TargetOptions &Options,
59                                   Optional<Reloc::Model> RM,
60                                   Optional<CodeModel::Model> CM,
61                                   CodeGenOpt::Level OL, bool JIT)
62    : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
63                        getEffectiveRelocModel(RM),
64                        getEffectiveCodeModel(CM, CodeModel::Small), OL),
65      TLOF(std::make_unique<TargetLoweringObjectFileELF>()),
66      Subtarget(TT, CPU, FS, *this) {
67  initAsmInfo();
68
69  BPFMCAsmInfo *MAI =
70      static_cast<BPFMCAsmInfo *>(const_cast<MCAsmInfo *>(AsmInfo.get()));
71  MAI->setDwarfUsesRelocationsAcrossSections(!Subtarget.getUseDwarfRIS());
72}
73
74namespace {
75// BPF Code Generator Pass Configuration Options.
76class BPFPassConfig : public TargetPassConfig {
77public:
78  BPFPassConfig(BPFTargetMachine &TM, PassManagerBase &PM)
79      : TargetPassConfig(TM, PM) {}
80
81  BPFTargetMachine &getBPFTargetMachine() const {
82    return getTM<BPFTargetMachine>();
83  }
84
85  void addIRPasses() override;
86  bool addInstSelector() override;
87  void addMachineSSAOptimization() override;
88  void addPreEmitPass() override;
89};
90}
91
92TargetPassConfig *BPFTargetMachine::createPassConfig(PassManagerBase &PM) {
93  return new BPFPassConfig(*this, PM);
94}
95
96void BPFPassConfig::addIRPasses() {
97
98  addPass(createBPFAbstractMemberAccess(&getBPFTargetMachine()));
99
100  TargetPassConfig::addIRPasses();
101}
102
103// Install an instruction selector pass using
104// the ISelDag to gen BPF code.
105bool BPFPassConfig::addInstSelector() {
106  addPass(createBPFISelDag(getBPFTargetMachine()));
107
108  return false;
109}
110
111void BPFPassConfig::addMachineSSAOptimization() {
112  addPass(createBPFMISimplifyPatchablePass());
113
114  // The default implementation must be called first as we want eBPF
115  // Peephole ran at last.
116  TargetPassConfig::addMachineSSAOptimization();
117
118  const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
119  if (!DisableMIPeephole) {
120    if (Subtarget->getHasAlu32())
121      addPass(createBPFMIPeepholePass());
122    addPass(createBPFMIPeepholeTruncElimPass());
123  }
124}
125
126void BPFPassConfig::addPreEmitPass() {
127  addPass(createBPFMIPreEmitCheckingPass());
128  if (getOptLevel() != CodeGenOpt::None)
129    if (!DisableMIPeephole)
130      addPass(createBPFMIPreEmitPeepholePass());
131}
132