BPFAsmBackend.cpp revision 0c7f116bb6950ef819323d855415b2f2b0aad987 
1//===-- BPFAsmBackend.cpp - BPF Assembler Backend -------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "MCTargetDesc/BPFMCTargetDesc.h"
11#include "llvm/MC/MCAsmBackend.h"
12#include "llvm/MC/MCAssembler.h"
13#include "llvm/MC/MCDirectives.h"
14#include "llvm/MC/MCELFObjectWriter.h"
15#include "llvm/MC/MCFixupKindInfo.h"
16#include "llvm/MC/MCObjectWriter.h"
17#include "llvm/MC/MCSubtargetInfo.h"
18#include "llvm/MC/MCExpr.h"
19#include "llvm/MC/MCSymbol.h"
20#include "llvm/Support/ErrorHandling.h"
21#include "llvm/Support/raw_ostream.h"
22
23using namespace llvm;
24
25namespace {
26class BPFAsmBackend : public MCAsmBackend {
27public:
28  BPFAsmBackend() : MCAsmBackend() {}
29  ~BPFAsmBackend() override {}
30
31  void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
32                  uint64_t Value, bool IsPCRel) const override;
33
34  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override;
35
36  // No instruction requires relaxation
37  bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
38                            const MCRelaxableFragment *DF,
39                            const MCAsmLayout &Layout) const override {
40    return false;
41  }
42
43  unsigned getNumFixupKinds() const override { return 1; }
44
45  bool mayNeedRelaxation(const MCInst &Inst) const override { return false; }
46
47  void relaxInstruction(const MCInst &Inst, MCInst &Res) const override {}
48
49  bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
50};
51
52bool BPFAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
53  if ((Count % 8) != 0)
54    return false;
55
56  for (uint64_t i = 0; i < Count; i += 8)
57    OW->Write64(0x15000000);
58
59  return true;
60}
61
62void BPFAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
63                               unsigned DataSize, uint64_t Value,
64                               bool IsPCRel) const {
65
66  if (Fixup.getKind() == FK_SecRel_4 || Fixup.getKind() == FK_SecRel_8) {
67    assert(Value == 0);
68    return;
69  }
70  assert(Fixup.getKind() == FK_PCRel_2);
71  *(uint16_t *)&Data[Fixup.getOffset() + 2] = (uint16_t)((Value - 8) / 8);
72}
73
74MCObjectWriter *BPFAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
75  return createBPFELFObjectWriter(OS, 0);
76}
77}
78
79MCAsmBackend *llvm::createBPFAsmBackend(const Target &T,
80                                        const MCRegisterInfo &MRI, StringRef TT,
81                                        StringRef CPU) {
82  return new BPFAsmBackend();
83}
84