AsmPrinterDwarf.cpp revision c06b4740af510c449b41bf2a2f25216f1525a0af 
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/MCAsmInfo.h"
17#include "llvm/MC/MCSection.h"
18#include "llvm/MC/MCStreamer.h"
19#include "llvm/MC/MCSymbol.h"
20#include "llvm/Target/TargetData.h"
21#include "llvm/Target/TargetLoweringObjectFile.h"
22#include "llvm/Target/TargetMachine.h"
23#include "llvm/ADT/Twine.h"
24#include "llvm/Support/Dwarf.h"
25using namespace llvm;
26
27/// EmitSLEB128 - emit the specified signed leb128 value.
28void AsmPrinter::EmitSLEB128(int Value, const char *Desc) const {
29  if (isVerbose() && Desc)
30    OutStreamer.AddComment(Desc);
31
32  if (MAI->hasLEB128()) {
33    // FIXME: MCize.
34    OutStreamer.EmitRawText("\t.sleb128\t" + Twine(Value));
35    return;
36  }
37
38  // If we don't have .sleb128, emit as .bytes.
39  int Sign = Value >> (8 * sizeof(Value) - 1);
40  bool IsMore;
41
42  do {
43    unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
44    Value >>= 7;
45    IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
46    if (IsMore) Byte |= 0x80;
47    OutStreamer.EmitIntValue(Byte, 1, /*addrspace*/0);
48  } while (IsMore);
49}
50
51/// EmitULEB128 - emit the specified signed leb128 value.
52void AsmPrinter::EmitULEB128(unsigned Value, const char *Desc,
53                             unsigned PadTo) const {
54  if (isVerbose() && Desc)
55    OutStreamer.AddComment(Desc);
56
57  if (MAI->hasLEB128() && PadTo == 0) {
58    // FIXME: MCize.
59    OutStreamer.EmitRawText("\t.uleb128\t" + Twine(Value));
60    return;
61  }
62
63  // If we don't have .uleb128 or we want to emit padding, emit as .bytes.
64  do {
65    unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
66    Value >>= 7;
67    if (Value || PadTo != 0) Byte |= 0x80;
68    OutStreamer.EmitIntValue(Byte, 1, /*addrspace*/0);
69  } while (Value);
70
71  if (PadTo) {
72    if (PadTo > 1)
73      OutStreamer.EmitFill(PadTo - 1, 0x80/*fillval*/, 0/*addrspace*/);
74    OutStreamer.EmitFill(1, 0/*fillval*/, 0/*addrspace*/);
75  }
76}
77
78/// EmitCFAByte - Emit a .byte 42 directive for a DW_CFA_xxx value.
79void AsmPrinter::EmitCFAByte(unsigned Val) const {
80  if (isVerbose()) {
81    if (Val >= dwarf::DW_CFA_offset && Val < dwarf::DW_CFA_offset+64)
82      OutStreamer.AddComment("DW_CFA_offset + Reg (" +
83                             Twine(Val-dwarf::DW_CFA_offset) + ")");
84    else
85      OutStreamer.AddComment(dwarf::CallFrameString(Val));
86  }
87  OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
88}
89
90static const char *DecodeDWARFEncoding(unsigned Encoding) {
91  switch (Encoding) {
92  case dwarf::DW_EH_PE_absptr: return "absptr";
93  case dwarf::DW_EH_PE_omit:   return "omit";
94  case dwarf::DW_EH_PE_pcrel:  return "pcrel";
95  case dwarf::DW_EH_PE_udata4: return "udata4";
96  case dwarf::DW_EH_PE_udata8: return "udata8";
97  case dwarf::DW_EH_PE_sdata4: return "sdata4";
98  case dwarf::DW_EH_PE_sdata8: return "sdata8";
99  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4: return "pcrel udata4";
100  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4: return "pcrel sdata4";
101  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8: return "pcrel udata8";
102  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8: return "pcrel sdata8";
103  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata4:
104    return "indirect pcrel udata4";
105  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata4:
106    return "indirect pcrel sdata4";
107  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata8:
108    return "indirect pcrel udata8";
109  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata8:
110    return "indirect pcrel sdata8";
111  }
112
113  return "<unknown encoding>";
114}
115
116
117/// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
118/// encoding.  If verbose assembly output is enabled, we output comments
119/// describing the encoding.  Desc is an optional string saying what the
120/// encoding is specifying (e.g. "LSDA").
121void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) {
122  if (isVerbose()) {
123    if (Desc != 0)
124      OutStreamer.AddComment(Twine(Desc)+" Encoding = " +
125                             Twine(DecodeDWARFEncoding(Val)));
126    else
127      OutStreamer.AddComment(Twine("Encoding = ") +
128                             DecodeDWARFEncoding(Val));
129  }
130
131  OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
132}
133
134/// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
135unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
136  if (Encoding == dwarf::DW_EH_PE_omit)
137    return 0;
138
139  switch (Encoding & 0x07) {
140  default: assert(0 && "Invalid encoded value.");
141  case dwarf::DW_EH_PE_absptr: return TM.getTargetData()->getPointerSize();
142  case dwarf::DW_EH_PE_udata2: return 2;
143  case dwarf::DW_EH_PE_udata4: return 4;
144  case dwarf::DW_EH_PE_udata8: return 8;
145  }
146}
147
148void AsmPrinter::EmitReference(const MCSymbol *Sym, unsigned Encoding) const {
149  const TargetLoweringObjectFile &TLOF = getObjFileLowering();
150
151  const MCExpr *Exp =
152    TLOF.getExprForDwarfReference(Sym, Mang, MMI, Encoding, OutStreamer);
153  OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding), /*addrspace*/0);
154}
155
156void AsmPrinter::EmitReference(const GlobalValue *GV, unsigned Encoding)const{
157  const TargetLoweringObjectFile &TLOF = getObjFileLowering();
158
159  const MCExpr *Exp =
160    TLOF.getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, OutStreamer);
161  OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding), /*addrspace*/0);
162}
163
164/// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
165/// section.  This can be done with a special directive if the target supports
166/// it (e.g. cygwin) or by emitting it as an offset from a label at the start
167/// of the section.
168///
169/// SectionLabel is a temporary label emitted at the start of the section that
170/// Label lives in.
171void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
172                                   const MCSymbol *SectionLabel) const {
173  // On COFF targets, we have to emit the special .secrel32 directive.
174  if (const char *SecOffDir = MAI->getDwarfSectionOffsetDirective()) {
175    // FIXME: MCize.
176    OutStreamer.EmitRawText(SecOffDir + Twine(Label->getName()));
177    return;
178  }
179
180  // Get the section that we're referring to, based on SectionLabel.
181  const MCSection &Section = SectionLabel->getSection();
182
183  // If Label has already been emitted, verify that it is in the same section as
184  // section label for sanity.
185  assert((!Label->isInSection() || &Label->getSection() == &Section) &&
186         "Section offset using wrong section base for label");
187
188  // If the section in question will end up with an address of 0 anyway, we can
189  // just emit an absolute reference to save a relocation.
190  if (Section.isBaseAddressKnownZero()) {
191    OutStreamer.EmitSymbolValue(Label, 4, 0/*AddrSpace*/);
192    return;
193  }
194
195  // Otherwise, emit it as a label difference from the start of the section.
196  EmitLabelDifference(Label, SectionLabel, 4);
197}
198
199
200