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#include "ByteStreamer.h"
15#include "DwarfDebug.h"
16#include "DwarfExpression.h"
17#include "llvm/ADT/Twine.h"
18#include "llvm/CodeGen/AsmPrinter.h"
19#include "llvm/CodeGen/DIE.h"
20#include "llvm/CodeGen/MachineFunction.h"
21#include "llvm/CodeGen/MachineModuleInfo.h"
22#include "llvm/IR/DataLayout.h"
23#include "llvm/MC/MCAsmInfo.h"
24#include "llvm/MC/MCRegisterInfo.h"
25#include "llvm/MC/MCSection.h"
26#include "llvm/MC/MCStreamer.h"
27#include "llvm/MC/MCSymbol.h"
28#include "llvm/MC/MachineLocation.h"
29#include "llvm/Support/Dwarf.h"
30#include "llvm/Support/ErrorHandling.h"
31#include "llvm/Target/TargetLoweringObjectFile.h"
32#include "llvm/Target/TargetMachine.h"
33#include "llvm/Target/TargetSubtargetInfo.h"
34using namespace llvm;
35
36#define DEBUG_TYPE "asm-printer"
37
38//===----------------------------------------------------------------------===//
39// Dwarf Emission Helper Routines
40//===----------------------------------------------------------------------===//
41
42/// EmitSLEB128 - emit the specified signed leb128 value.
43void AsmPrinter::EmitSLEB128(int64_t Value, const char *Desc) const {
44  if (isVerbose() && Desc)
45    OutStreamer.AddComment(Desc);
46
47  OutStreamer.EmitSLEB128IntValue(Value);
48}
49
50/// EmitULEB128 - emit the specified signed leb128 value.
51void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc,
52                             unsigned PadTo) const {
53  if (isVerbose() && Desc)
54    OutStreamer.AddComment(Desc);
55
56  OutStreamer.EmitULEB128IntValue(Value, PadTo);
57}
58
59/// EmitCFAByte - Emit a .byte 42 directive for a DW_CFA_xxx value.
60void AsmPrinter::EmitCFAByte(unsigned Val) const {
61  if (isVerbose()) {
62    if (Val >= dwarf::DW_CFA_offset && Val < dwarf::DW_CFA_offset + 64)
63      OutStreamer.AddComment("DW_CFA_offset + Reg (" +
64                             Twine(Val - dwarf::DW_CFA_offset) + ")");
65    else
66      OutStreamer.AddComment(dwarf::CallFrameString(Val));
67  }
68  OutStreamer.EmitIntValue(Val, 1);
69}
70
71static const char *DecodeDWARFEncoding(unsigned Encoding) {
72  switch (Encoding) {
73  case dwarf::DW_EH_PE_absptr:
74    return "absptr";
75  case dwarf::DW_EH_PE_omit:
76    return "omit";
77  case dwarf::DW_EH_PE_pcrel:
78    return "pcrel";
79  case dwarf::DW_EH_PE_udata4:
80    return "udata4";
81  case dwarf::DW_EH_PE_udata8:
82    return "udata8";
83  case dwarf::DW_EH_PE_sdata4:
84    return "sdata4";
85  case dwarf::DW_EH_PE_sdata8:
86    return "sdata8";
87  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
88    return "pcrel udata4";
89  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
90    return "pcrel sdata4";
91  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
92    return "pcrel udata8";
93  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
94    return "pcrel sdata8";
95  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4
96      :
97    return "indirect pcrel udata4";
98  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
99      :
100    return "indirect pcrel sdata4";
101  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8
102      :
103    return "indirect pcrel udata8";
104  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8
105      :
106    return "indirect pcrel sdata8";
107  }
108
109  return "<unknown encoding>";
110}
111
112/// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
113/// encoding.  If verbose assembly output is enabled, we output comments
114/// describing the encoding.  Desc is an optional string saying what the
115/// encoding is specifying (e.g. "LSDA").
116void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) const {
117  if (isVerbose()) {
118    if (Desc)
119      OutStreamer.AddComment(Twine(Desc) + " Encoding = " +
120                             Twine(DecodeDWARFEncoding(Val)));
121    else
122      OutStreamer.AddComment(Twine("Encoding = ") + DecodeDWARFEncoding(Val));
123  }
124
125  OutStreamer.EmitIntValue(Val, 1);
126}
127
128/// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
129unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
130  if (Encoding == dwarf::DW_EH_PE_omit)
131    return 0;
132
133  switch (Encoding & 0x07) {
134  default:
135    llvm_unreachable("Invalid encoded value.");
136  case dwarf::DW_EH_PE_absptr:
137    return TM.getDataLayout()->getPointerSize();
138  case dwarf::DW_EH_PE_udata2:
139    return 2;
140  case dwarf::DW_EH_PE_udata4:
141    return 4;
142  case dwarf::DW_EH_PE_udata8:
143    return 8;
144  }
145}
146
147void AsmPrinter::EmitTTypeReference(const GlobalValue *GV,
148                                    unsigned Encoding) const {
149  if (GV) {
150    const TargetLoweringObjectFile &TLOF = getObjFileLowering();
151
152    const MCExpr *Exp =
153        TLOF.getTTypeGlobalReference(GV, Encoding, *Mang, TM, MMI, OutStreamer);
154    OutStreamer.EmitValue(Exp, GetSizeOfEncodedValue(Encoding));
155  } else
156    OutStreamer.EmitIntValue(0, GetSizeOfEncodedValue(Encoding));
157}
158
159/// EmitSectionOffset - Emit the 4-byte offset of Label from the start of its
160/// section.  This can be done with a special directive if the target supports
161/// it (e.g. cygwin) or by emitting it as an offset from a label at the start
162/// of the section.
163///
164/// SectionLabel is a temporary label emitted at the start of the section that
165/// Label lives in.
166void AsmPrinter::emitSectionOffset(const MCSymbol *Label) const {
167  // On COFF targets, we have to emit the special .secrel32 directive.
168  if (MAI->needsDwarfSectionOffsetDirective()) {
169    OutStreamer.EmitCOFFSecRel32(Label);
170    return;
171  }
172
173  // If the format uses relocations with dwarf, refer to the symbol directly.
174  if (MAI->doesDwarfUseRelocationsAcrossSections()) {
175    OutStreamer.EmitSymbolValue(Label, 4);
176    return;
177  }
178
179  // Otherwise, emit it as a label difference from the start of the section.
180  EmitLabelDifference(Label, Label->getSection().getBeginSymbol(), 4);
181}
182
183/// EmitDwarfRegOp - Emit dwarf register operation.
184void AsmPrinter::EmitDwarfRegOp(ByteStreamer &Streamer,
185                                const MachineLocation &MLoc) const {
186  DebugLocDwarfExpression Expr(*MF->getSubtarget().getRegisterInfo(),
187                               getDwarfDebug()->getDwarfVersion(), Streamer);
188  const MCRegisterInfo *MRI = MMI->getContext().getRegisterInfo();
189  int Reg = MRI->getDwarfRegNum(MLoc.getReg(), false);
190  if (Reg < 0) {
191    // We assume that pointers are always in an addressable register.
192    if (MLoc.isIndirect())
193      // FIXME: We have no reasonable way of handling errors in here. The
194      // caller might be in the middle of a dwarf expression. We should
195      // probably assert that Reg >= 0 once debug info generation is more
196      // mature.
197      return Expr.EmitOp(dwarf::DW_OP_nop,
198                         "nop (could not find a dwarf register number)");
199
200    // Attempt to find a valid super- or sub-register.
201    if (!Expr.AddMachineRegPiece(MLoc.getReg()))
202      Expr.EmitOp(dwarf::DW_OP_nop,
203                  "nop (could not find a dwarf register number)");
204    return;
205  }
206
207  if (MLoc.isIndirect())
208    Expr.AddRegIndirect(Reg, MLoc.getOffset());
209  else
210    Expr.AddReg(Reg);
211}
212
213//===----------------------------------------------------------------------===//
214// Dwarf Lowering Routines
215//===----------------------------------------------------------------------===//
216
217void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
218  switch (Inst.getOperation()) {
219  default:
220    llvm_unreachable("Unexpected instruction");
221  case MCCFIInstruction::OpDefCfaOffset:
222    OutStreamer.EmitCFIDefCfaOffset(Inst.getOffset());
223    break;
224  case MCCFIInstruction::OpDefCfa:
225    OutStreamer.EmitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
226    break;
227  case MCCFIInstruction::OpDefCfaRegister:
228    OutStreamer.EmitCFIDefCfaRegister(Inst.getRegister());
229    break;
230  case MCCFIInstruction::OpOffset:
231    OutStreamer.EmitCFIOffset(Inst.getRegister(), Inst.getOffset());
232    break;
233  case MCCFIInstruction::OpRegister:
234    OutStreamer.EmitCFIRegister(Inst.getRegister(), Inst.getRegister2());
235    break;
236  case MCCFIInstruction::OpWindowSave:
237    OutStreamer.EmitCFIWindowSave();
238    break;
239  case MCCFIInstruction::OpSameValue:
240    OutStreamer.EmitCFISameValue(Inst.getRegister());
241    break;
242  }
243}
244
245void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
246  // Get the abbreviation for this DIE.
247  const DIEAbbrev &Abbrev = Die.getAbbrev();
248
249  // Emit the code (index) for the abbreviation.
250  if (isVerbose())
251    OutStreamer.AddComment("Abbrev [" + Twine(Abbrev.getNumber()) +
252                           "] 0x" + Twine::utohexstr(Die.getOffset()) +
253                           ":0x" + Twine::utohexstr(Die.getSize()) + " " +
254                           dwarf::TagString(Abbrev.getTag()));
255  EmitULEB128(Abbrev.getNumber());
256
257  const SmallVectorImpl<DIEValue *> &Values = Die.getValues();
258  const SmallVectorImpl<DIEAbbrevData> &AbbrevData = Abbrev.getData();
259
260  // Emit the DIE attribute values.
261  for (unsigned i = 0, N = Values.size(); i < N; ++i) {
262    dwarf::Attribute Attr = AbbrevData[i].getAttribute();
263    dwarf::Form Form = AbbrevData[i].getForm();
264    assert(Form && "Too many attributes for DIE (check abbreviation)");
265
266    if (isVerbose()) {
267      OutStreamer.AddComment(dwarf::AttributeString(Attr));
268      if (Attr == dwarf::DW_AT_accessibility)
269        OutStreamer.AddComment(dwarf::AccessibilityString(
270            cast<DIEInteger>(Values[i])->getValue()));
271    }
272
273    // Emit an attribute using the defined form.
274    Values[i]->EmitValue(this, Form);
275  }
276
277  // Emit the DIE children if any.
278  if (Abbrev.hasChildren()) {
279    for (auto &Child : Die.getChildren())
280      emitDwarfDIE(*Child);
281
282    OutStreamer.AddComment("End Of Children Mark");
283    EmitInt8(0);
284  }
285}
286
287void
288AsmPrinter::emitDwarfAbbrevs(const std::vector<DIEAbbrev *>& Abbrevs) const {
289  // For each abbrevation.
290  for (const DIEAbbrev *Abbrev : Abbrevs) {
291    // Emit the abbrevations code (base 1 index.)
292    EmitULEB128(Abbrev->getNumber(), "Abbreviation Code");
293
294    // Emit the abbreviations data.
295    Abbrev->Emit(this);
296  }
297
298  // Mark end of abbreviations.
299  EmitULEB128(0, "EOM(3)");
300}
301