AsmPrinterDwarf.cpp revision 98eea4dc9750c7333821212b567f80cc9bd4e915 
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/CodeGen/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/Target/TargetData.h"
22#include "llvm/Target/TargetFrameInfo.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"
28using namespace llvm;
29
30//===----------------------------------------------------------------------===//
31// Dwarf Emission Helper Routines
32//===----------------------------------------------------------------------===//
33
34/// EmitSLEB128 - emit the specified signed leb128 value.
35void AsmPrinter::EmitSLEB128(int Value, const char *Desc) const {
36  if (isVerbose() && Desc)
37    OutStreamer.AddComment(Desc);
38
39  if (MAI->hasLEB128()) {
40    OutStreamer.EmitSLEB128IntValue(Value);
41    return;
42  }
43
44  // If we don't have .sleb128, emit as .bytes.
45  int Sign = Value >> (8 * sizeof(Value) - 1);
46  bool IsMore;
47
48  do {
49    unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
50    Value >>= 7;
51    IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
52    if (IsMore) Byte |= 0x80;
53    OutStreamer.EmitIntValue(Byte, 1, /*addrspace*/0);
54  } while (IsMore);
55}
56
57/// EmitULEB128 - emit the specified signed leb128 value.
58void AsmPrinter::EmitULEB128(unsigned Value, const char *Desc,
59                             unsigned PadTo) const {
60  if (isVerbose() && Desc)
61    OutStreamer.AddComment(Desc);
62
63  // FIXME: Should we add a PadTo option to the streamer?
64  if (MAI->hasLEB128() && PadTo == 0) {
65    OutStreamer.EmitULEB128IntValue(Value);
66    return;
67  }
68
69  // If we don't have .uleb128 or we want to emit padding, emit as .bytes.
70  do {
71    unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
72    Value >>= 7;
73    if (Value || PadTo != 0) Byte |= 0x80;
74    OutStreamer.EmitIntValue(Byte, 1, /*addrspace*/0);
75  } while (Value);
76
77  if (PadTo) {
78    if (PadTo > 1)
79      OutStreamer.EmitFill(PadTo - 1, 0x80/*fillval*/, 0/*addrspace*/);
80    OutStreamer.EmitFill(1, 0/*fillval*/, 0/*addrspace*/);
81  }
82}
83
84/// EmitCFAByte - Emit a .byte 42 directive for a DW_CFA_xxx value.
85void AsmPrinter::EmitCFAByte(unsigned Val) const {
86  if (isVerbose()) {
87    if (Val >= dwarf::DW_CFA_offset && Val < dwarf::DW_CFA_offset+64)
88      OutStreamer.AddComment("DW_CFA_offset + Reg (" +
89                             Twine(Val-dwarf::DW_CFA_offset) + ")");
90    else
91      OutStreamer.AddComment(dwarf::CallFrameString(Val));
92  }
93  OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
94}
95
96static const char *DecodeDWARFEncoding(unsigned Encoding) {
97  switch (Encoding) {
98  case dwarf::DW_EH_PE_absptr: return "absptr";
99  case dwarf::DW_EH_PE_omit:   return "omit";
100  case dwarf::DW_EH_PE_pcrel:  return "pcrel";
101  case dwarf::DW_EH_PE_udata4: return "udata4";
102  case dwarf::DW_EH_PE_udata8: return "udata8";
103  case dwarf::DW_EH_PE_sdata4: return "sdata4";
104  case dwarf::DW_EH_PE_sdata8: return "sdata8";
105  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4: return "pcrel udata4";
106  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4: return "pcrel sdata4";
107  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8: return "pcrel udata8";
108  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8: return "pcrel sdata8";
109  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata4:
110    return "indirect pcrel udata4";
111  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata4:
112    return "indirect pcrel sdata4";
113  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata8:
114    return "indirect pcrel udata8";
115  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata8:
116    return "indirect pcrel sdata8";
117  }
118
119  return "<unknown encoding>";
120}
121
122
123/// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
124/// encoding.  If verbose assembly output is enabled, we output comments
125/// describing the encoding.  Desc is an optional string saying what the
126/// encoding is specifying (e.g. "LSDA").
127void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) const {
128  if (isVerbose()) {
129    if (Desc != 0)
130      OutStreamer.AddComment(Twine(Desc)+" Encoding = " +
131                             Twine(DecodeDWARFEncoding(Val)));
132    else
133      OutStreamer.AddComment(Twine("Encoding = ") +
134                             DecodeDWARFEncoding(Val));
135  }
136
137  OutStreamer.EmitIntValue(Val, 1, 0/*addrspace*/);
138}
139
140/// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
141unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
142  if (Encoding == dwarf::DW_EH_PE_omit)
143    return 0;
144
145  switch (Encoding & 0x07) {
146  default: assert(0 && "Invalid encoded value.");
147  case dwarf::DW_EH_PE_absptr: return TM.getTargetData()->getPointerSize();
148  case dwarf::DW_EH_PE_udata2: return 2;
149  case dwarf::DW_EH_PE_udata4: return 4;
150  case dwarf::DW_EH_PE_udata8: return 8;
151  }
152}
153
154void AsmPrinter::EmitReference(const MCSymbol *Sym, unsigned Encoding) const {
155  const TargetLoweringObjectFile &TLOF = getObjFileLowering();
156
157  const MCExpr *Exp =
158    TLOF.getExprForDwarfReference(Sym, Mang, MMI, Encoding, OutStreamer);
159  OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding), /*addrspace*/0);
160}
161
162void AsmPrinter::EmitReference(const GlobalValue *GV, unsigned Encoding)const{
163  const TargetLoweringObjectFile &TLOF = getObjFileLowering();
164
165  const MCExpr *Exp =
166    TLOF.getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, OutStreamer);
167  OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding), /*addrspace*/0);
168}
169
170/// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
171/// section.  This can be done with a special directive if the target supports
172/// it (e.g. cygwin) or by emitting it as an offset from a label at the start
173/// of the section.
174///
175/// SectionLabel is a temporary label emitted at the start of the section that
176/// Label lives in.
177void AsmPrinter::EmitSectionOffset(const MCSymbol *Label,
178                                   const MCSymbol *SectionLabel) const {
179  // On COFF targets, we have to emit the special .secrel32 directive.
180  if (const char *SecOffDir = MAI->getDwarfSectionOffsetDirective()) {
181    // FIXME: MCize.
182    OutStreamer.EmitRawText(SecOffDir + Twine(Label->getName()));
183    return;
184  }
185
186  // Get the section that we're referring to, based on SectionLabel.
187  const MCSection &Section = SectionLabel->getSection();
188
189  // If Label has already been emitted, verify that it is in the same section as
190  // section label for sanity.
191  assert((!Label->isInSection() || &Label->getSection() == &Section) &&
192         "Section offset using wrong section base for label");
193
194  // If the section in question will end up with an address of 0 anyway, we can
195  // just emit an absolute reference to save a relocation.
196  if (Section.isBaseAddressKnownZero()) {
197    OutStreamer.EmitSymbolValue(Label, 4, 0/*AddrSpace*/);
198    return;
199  }
200
201  // Otherwise, emit it as a label difference from the start of the section.
202  EmitLabelDifference(Label, SectionLabel, 4);
203}
204
205//===----------------------------------------------------------------------===//
206// Dwarf Lowering Routines
207//===----------------------------------------------------------------------===//
208
209
210/// EmitFrameMoves - Emit frame instructions to describe the layout of the
211/// frame.
212void AsmPrinter::EmitFrameMoves(const std::vector<MachineMove> &Moves,
213                                MCSymbol *BaseLabel, bool isEH) const {
214  const TargetRegisterInfo *RI = TM.getRegisterInfo();
215
216  int stackGrowth = TM.getTargetData()->getPointerSize();
217  if (TM.getFrameInfo()->getStackGrowthDirection() !=
218      TargetFrameInfo::StackGrowsUp)
219    stackGrowth *= -1;
220
221  for (unsigned i = 0, N = Moves.size(); i < N; ++i) {
222    const MachineMove &Move = Moves[i];
223    MCSymbol *Label = Move.getLabel();
224    // Throw out move if the label is invalid.
225    if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
226
227    const MachineLocation &Dst = Move.getDestination();
228    const MachineLocation &Src = Move.getSource();
229
230    // Advance row if new location.
231    if (BaseLabel && Label) {
232      MCSymbol *ThisSym = Label;
233      if (ThisSym != BaseLabel) {
234        EmitCFAByte(dwarf::DW_CFA_advance_loc4);
235        EmitLabelDifference(ThisSym, BaseLabel, 4);
236        BaseLabel = ThisSym;
237      }
238    }
239
240    // If advancing cfa.
241    if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
242      assert(!Src.isReg() && "Machine move not supported yet.");
243
244      if (Src.getReg() == MachineLocation::VirtualFP) {
245        EmitCFAByte(dwarf::DW_CFA_def_cfa_offset);
246      } else {
247        EmitCFAByte(dwarf::DW_CFA_def_cfa);
248        EmitULEB128(RI->getDwarfRegNum(Src.getReg(), isEH), "Register");
249      }
250
251      EmitULEB128(-Src.getOffset(), "Offset");
252      continue;
253    }
254
255    if (Src.isReg() && Src.getReg() == MachineLocation::VirtualFP) {
256      assert(Dst.isReg() && "Machine move not supported yet.");
257      EmitCFAByte(dwarf::DW_CFA_def_cfa_register);
258      EmitULEB128(RI->getDwarfRegNum(Dst.getReg(), isEH), "Register");
259      continue;
260    }
261
262    unsigned Reg = RI->getDwarfRegNum(Src.getReg(), isEH);
263    int Offset = Dst.getOffset() / stackGrowth;
264
265    if (Offset < 0) {
266      EmitCFAByte(dwarf::DW_CFA_offset_extended_sf);
267      EmitULEB128(Reg, "Reg");
268      EmitSLEB128(Offset, "Offset");
269    } else if (Reg < 64) {
270      EmitCFAByte(dwarf::DW_CFA_offset + Reg);
271      EmitULEB128(Offset, "Offset");
272    } else {
273      EmitCFAByte(dwarf::DW_CFA_offset_extended);
274      EmitULEB128(Reg, "Reg");
275      EmitULEB128(Offset, "Offset");
276    }
277  }
278}
279