AsmPrinterDwarf.cpp revision aaa50b9bc5e8707015ff31dce0a3665600f6b440 
1//===-- AsmPrinterDwarf.cpp - AsmPrinter Dwarf Support --------------------===//
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// This file implements the Dwarf emissions parts of AsmPrinter.
11//
12//===----------------------------------------------------------------------===//
13
14#define DEBUG_TYPE "asm-printer"
15#include "llvm/CodeGen/AsmPrinter.h"
16#include "llvm/MC/MachineLocation.h"
17#include "llvm/MC/MCAsmInfo.h"
18#include "llvm/MC/MCSection.h"
19#include "llvm/MC/MCStreamer.h"
20#include "llvm/MC/MCSymbol.h"
21#include "llvm/DataLayout.h"
22#include "llvm/Target/TargetFrameLowering.h"
23#include "llvm/Target/TargetLoweringObjectFile.h"
24#include "llvm/Target/TargetMachine.h"
25#include "llvm/Target/TargetRegisterInfo.h"
26#include "llvm/ADT/Twine.h"
27#include "llvm/Support/Dwarf.h"
28#include "llvm/Support/ErrorHandling.h"
29using namespace llvm;
30
31//===----------------------------------------------------------------------===//
32// Dwarf Emission Helper Routines
33//===----------------------------------------------------------------------===//
34
35/// EmitSLEB128 - emit the specified signed leb128 value.
36void AsmPrinter::EmitSLEB128(int Value, const char *Desc) const {
37  if (isVerbose() && Desc)
38    OutStreamer.AddComment(Desc);
39
40  OutStreamer.EmitSLEB128IntValue(Value);
41}
42
43/// EmitULEB128 - emit the specified signed leb128 value.
44void AsmPrinter::EmitULEB128(unsigned Value, const char *Desc,
45                             unsigned PadTo) const {
46  if (isVerbose() && Desc)
47    OutStreamer.AddComment(Desc);
48
49  OutStreamer.EmitULEB128IntValue(Value, 0/*addrspace*/, PadTo);
50}
51
52/// EmitCFAByte - Emit a .byte 42 directive for a DW_CFA_xxx value.
53void AsmPrinter::EmitCFAByte(unsigned Val) const {
54  if (isVerbose()) {
55    if (Val >= dwarf::DW_CFA_offset && Val < dwarf::DW_CFA_offset+64)
56      OutStreamer.AddComment("DW_CFA_offset + Reg (" +
57                             Twine(Val-dwarf::DW_CFA_offset) + ")");
58    else
59      OutStreamer.AddComment(dwarf::CallFrameString(Val));
60  }
61  OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
62}
63
64static const char *DecodeDWARFEncoding(unsigned Encoding) {
65  switch (Encoding) {
66  case dwarf::DW_EH_PE_absptr: return "absptr";
67  case dwarf::DW_EH_PE_omit:   return "omit";
68  case dwarf::DW_EH_PE_pcrel:  return "pcrel";
69  case dwarf::DW_EH_PE_udata4: return "udata4";
70  case dwarf::DW_EH_PE_udata8: return "udata8";
71  case dwarf::DW_EH_PE_sdata4: return "sdata4";
72  case dwarf::DW_EH_PE_sdata8: return "sdata8";
73  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4: return "pcrel udata4";
74  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4: return "pcrel sdata4";
75  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8: return "pcrel udata8";
76  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8: return "pcrel sdata8";
77  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata4:
78    return "indirect pcrel udata4";
79  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata4:
80    return "indirect pcrel sdata4";
81  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata8:
82    return "indirect pcrel udata8";
83  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata8:
84    return "indirect pcrel sdata8";
85  }
86
87  return "<unknown encoding>";
88}
89
90
91/// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
92/// encoding.  If verbose assembly output is enabled, we output comments
93/// describing the encoding.  Desc is an optional string saying what the
94/// encoding is specifying (e.g. "LSDA").
95void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) const {
96  if (isVerbose()) {
97    if (Desc != 0)
98      OutStreamer.AddComment(Twine(Desc)+" Encoding = " +
99                             Twine(DecodeDWARFEncoding(Val)));
100    else
101      OutStreamer.AddComment(Twine("Encoding = ") +
102                             DecodeDWARFEncoding(Val));
103  }
104
105  OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
106}
107
108/// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
109unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
110  if (Encoding == dwarf::DW_EH_PE_omit)
111    return 0;
112
113  switch (Encoding & 0x07) {
114  default: llvm_unreachable("Invalid encoded value.");
115  case dwarf::DW_EH_PE_absptr: return TM.getDataLayout()->getPointerSize();
116  case dwarf::DW_EH_PE_udata2: return 2;
117  case dwarf::DW_EH_PE_udata4: return 4;
118  case dwarf::DW_EH_PE_udata8: return 8;
119  }
120}
121
122void AsmPrinter::EmitTTypeReference(const GlobalValue *GV,
123                                    unsigned Encoding) const {
124  if (GV) {
125    const TargetLoweringObjectFile &TLOF = getObjFileLowering();
126
127    const MCExpr *Exp =
128      TLOF.getTTypeGlobalReference(GV, Mang, MMI, Encoding, OutStreamer);
129    OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding), /*addrspace*/0);
130  } else
131    OutStreamer.EmitIntValue(0, GetSizeOfEncodedValue(Encoding), 0);
132}
133
134/// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
135/// section.  This can be done with a special directive if the target supports
136/// it (e.g. cygwin) or by emitting it as an offset from a label at the start
137/// of the section.
138///
139/// SectionLabel is a temporary label emitted at the start of the section that
140/// Label lives in.
141void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
142                                   const MCSymbol *SectionLabel) const {
143  // On COFF targets, we have to emit the special .secrel32 directive.
144  if (MAI->getDwarfSectionOffsetDirective()) {
145    OutStreamer.EmitCOFFSecRel32(Label);
146    return;
147  }
148
149  // Get the section that we're referring to, based on SectionLabel.
150  const MCSection &Section = SectionLabel->getSection();
151
152  // If Label has already been emitted, verify that it is in the same section as
153  // section label for sanity.
154  assert((!Label->isInSection() || &Label->getSection() == &Section) &&
155         "Section offset using wrong section base for label");
156
157  // If the section in question will end up with an address of 0 anyway, we can
158  // just emit an absolute reference to save a relocation.
159  if (Section.isBaseAddressKnownZero()) {
160    OutStreamer.EmitSymbolValue(Label, 4, 0/*AddrSpace*/);
161    return;
162  }
163
164  // Otherwise, emit it as a label difference from the start of the section.
165  EmitLabelDifference(Label, SectionLabel, 4);
166}
167
168//===----------------------------------------------------------------------===//
169// Dwarf Lowering Routines
170//===----------------------------------------------------------------------===//
171
172/// EmitCFIFrameMove - Emit a frame instruction.
173void AsmPrinter::EmitCFIFrameMove(const MachineMove &Move) const {
174  const TargetRegisterInfo *RI = TM.getRegisterInfo();
175
176  const MachineLocation &Dst = Move.getDestination();
177  const MachineLocation &Src = Move.getSource();
178
179  // If advancing cfa.
180  if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
181    if (Src.getReg() == MachineLocation::VirtualFP) {
182      OutStreamer.EmitCFIDefCfaOffset(-Src.getOffset());
183    } else {
184      // Reg + Offset
185      OutStreamer.EmitCFIDefCfa(RI->getDwarfRegNum(Src.getReg(), true),
186                                Src.getOffset());
187    }
188  } else if (Src.isReg() && Src.getReg() == MachineLocation::VirtualFP) {
189    assert(Dst.isReg() && "Machine move not supported yet.");
190    OutStreamer.EmitCFIDefCfaRegister(RI->getDwarfRegNum(Dst.getReg(), true));
191  } else {
192    assert(!Dst.isReg() && "Machine move not supported yet.");
193    OutStreamer.EmitCFIOffset(RI->getDwarfRegNum(Src.getReg(), true),
194                              Dst.getOffset());
195  }
196}
197