AsmPrinterDwarf.cpp revision 3574eca1b02600bac4e625297f4ecf745f4c4f32 
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::EmitReference(const MCSymbol *Sym, unsigned Encoding) const {
123  const TargetLoweringObjectFile &TLOF = getObjFileLowering();
124
125  const MCExpr *Exp =
126    TLOF.getExprForDwarfReference(Sym, Encoding, OutStreamer);
127  OutStreamer.EmitAbsValue(Exp, GetSizeOfEncodedValue(Encoding));
128}
129
130void AsmPrinter::EmitReference(const GlobalValue *GV, unsigned Encoding)const{
131  const TargetLoweringObjectFile &TLOF = getObjFileLowering();
132
133  const MCExpr *Exp =
134    TLOF.getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, OutStreamer);
135  OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding), /*addrspace*/0);
136}
137
138/// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
139/// section.  This can be done with a special directive if the target supports
140/// it (e.g. cygwin) or by emitting it as an offset from a label at the start
141/// of the section.
142///
143/// SectionLabel is a temporary label emitted at the start of the section that
144/// Label lives in.
145void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
146                                   const MCSymbol *SectionLabel) const {
147  // On COFF targets, we have to emit the special .secrel32 directive.
148  if (MAI->getDwarfSectionOffsetDirective()) {
149    OutStreamer.EmitCOFFSecRel32(Label);
150    return;
151  }
152
153  // Get the section that we're referring to, based on SectionLabel.
154  const MCSection &Section = SectionLabel->getSection();
155
156  // If Label has already been emitted, verify that it is in the same section as
157  // section label for sanity.
158  assert((!Label->isInSection() || &Label->getSection() == &Section) &&
159         "Section offset using wrong section base for label");
160
161  // If the section in question will end up with an address of 0 anyway, we can
162  // just emit an absolute reference to save a relocation.
163  if (Section.isBaseAddressKnownZero()) {
164    OutStreamer.EmitSymbolValue(Label, 4, 0/*AddrSpace*/);
165    return;
166  }
167
168  // Otherwise, emit it as a label difference from the start of the section.
169  EmitLabelDifference(Label, SectionLabel, 4);
170}
171
172//===----------------------------------------------------------------------===//
173// Dwarf Lowering Routines
174//===----------------------------------------------------------------------===//
175
176/// EmitCFIFrameMove - Emit a frame instruction.
177void AsmPrinter::EmitCFIFrameMove(const MachineMove &Move) const {
178  const TargetRegisterInfo *RI = TM.getRegisterInfo();
179
180  const MachineLocation &Dst = Move.getDestination();
181  const MachineLocation &Src = Move.getSource();
182
183  // If advancing cfa.
184  if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
185    if (Src.getReg() == MachineLocation::VirtualFP) {
186      OutStreamer.EmitCFIDefCfaOffset(-Src.getOffset());
187    } else {
188      // Reg + Offset
189      OutStreamer.EmitCFIDefCfa(RI->getDwarfRegNum(Src.getReg(), true),
190                                Src.getOffset());
191    }
192  } else if (Src.isReg() && Src.getReg() == MachineLocation::VirtualFP) {
193    assert(Dst.isReg() && "Machine move not supported yet.");
194    OutStreamer.EmitCFIDefCfaRegister(RI->getDwarfRegNum(Dst.getReg(), true));
195  } else {
196    assert(!Dst.isReg() && "Machine move not supported yet.");
197    OutStreamer.EmitCFIOffset(RI->getDwarfRegNum(Src.getReg(), true),
198                              Dst.getOffset());
199  }
200}
201