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/BinaryFormat/Dwarf.h"
19 #include "llvm/CodeGen/AsmPrinter.h"
20 #include "llvm/CodeGen/DIE.h"
21 #include "llvm/CodeGen/MachineFunction.h"
22 #include "llvm/CodeGen/MachineModuleInfo.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/MC/MCAsmInfo.h"
25 #include "llvm/MC/MCRegisterInfo.h"
26 #include "llvm/MC/MCSection.h"
27 #include "llvm/MC/MCStreamer.h"
28 #include "llvm/MC/MCSymbol.h"
29 #include "llvm/MC/MachineLocation.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"
34 using 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.
43 void 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 unsigned leb128 value.
51 void 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 static const char *DecodeDWARFEncoding(unsigned Encoding) {
60   switch (Encoding) {
61   case dwarf::DW_EH_PE_absptr:
62     return "absptr";
63   case dwarf::DW_EH_PE_omit:
64     return "omit";
65   case dwarf::DW_EH_PE_pcrel:
66     return "pcrel";
67   case dwarf::DW_EH_PE_udata4:
68     return "udata4";
69   case dwarf::DW_EH_PE_udata8:
70     return "udata8";
71   case dwarf::DW_EH_PE_sdata4:
72     return "sdata4";
73   case dwarf::DW_EH_PE_sdata8:
74     return "sdata8";
75   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
76     return "pcrel udata4";
77   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
78     return "pcrel sdata4";
79   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
80     return "pcrel udata8";
81   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
82     return "pcrel sdata8";
83   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4
84       :
85     return "indirect pcrel udata4";
86   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
87       :
88     return "indirect pcrel sdata4";
89   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8
90       :
91     return "indirect pcrel udata8";
92   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8
93       :
94     return "indirect pcrel sdata8";
95   }
96 
97   return "<unknown encoding>";
98 }
99 
100 /// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
101 /// encoding.  If verbose assembly output is enabled, we output comments
102 /// describing the encoding.  Desc is an optional string saying what the
103 /// encoding is specifying (e.g. "LSDA").
104 void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) const {
105   if (isVerbose()) {
106     if (Desc)
107       OutStreamer->AddComment(Twine(Desc) + " Encoding = " +
108                               Twine(DecodeDWARFEncoding(Val)));
109     else
110       OutStreamer->AddComment(Twine("Encoding = ") + DecodeDWARFEncoding(Val));
111   }
112 
113   OutStreamer->EmitIntValue(Val, 1);
114 }
115 
116 /// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
117 unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
118   if (Encoding == dwarf::DW_EH_PE_omit)
119     return 0;
120 
121   switch (Encoding & 0x07) {
122   default:
123     llvm_unreachable("Invalid encoded value.");
124   case dwarf::DW_EH_PE_absptr:
125     return MF->getDataLayout().getPointerSize();
126   case dwarf::DW_EH_PE_udata2:
127     return 2;
128   case dwarf::DW_EH_PE_udata4:
129     return 4;
130   case dwarf::DW_EH_PE_udata8:
131     return 8;
132   }
133 }
134 
135 void AsmPrinter::EmitTTypeReference(const GlobalValue *GV,
136                                     unsigned Encoding) const {
137   if (GV) {
138     const TargetLoweringObjectFile &TLOF = getObjFileLowering();
139 
140     const MCExpr *Exp =
141         TLOF.getTTypeGlobalReference(GV, Encoding, TM, MMI, *OutStreamer);
142     OutStreamer->EmitValue(Exp, GetSizeOfEncodedValue(Encoding));
143   } else
144     OutStreamer->EmitIntValue(0, GetSizeOfEncodedValue(Encoding));
145 }
146 
147 void AsmPrinter::emitDwarfSymbolReference(const MCSymbol *Label,
148                                           bool ForceOffset) const {
149   if (!ForceOffset) {
150     // On COFF targets, we have to emit the special .secrel32 directive.
151     if (MAI->needsDwarfSectionOffsetDirective()) {
152       OutStreamer->EmitCOFFSecRel32(Label, /*Offset=*/0);
153       return;
154     }
155 
156     // If the format uses relocations with dwarf, refer to the symbol directly.
157     if (MAI->doesDwarfUseRelocationsAcrossSections()) {
158       OutStreamer->EmitSymbolValue(Label, 4);
159       return;
160     }
161   }
162 
163   // Otherwise, emit it as a label difference from the start of the section.
164   EmitLabelDifference(Label, Label->getSection().getBeginSymbol(), 4);
165 }
166 
167 void AsmPrinter::emitDwarfStringOffset(DwarfStringPoolEntryRef S) const {
168   if (MAI->doesDwarfUseRelocationsAcrossSections()) {
169     emitDwarfSymbolReference(S.getSymbol());
170     return;
171   }
172 
173   // Just emit the offset directly; no need for symbol math.
174   EmitInt32(S.getOffset());
175 }
176 
177 //===----------------------------------------------------------------------===//
178 // Dwarf Lowering Routines
179 //===----------------------------------------------------------------------===//
180 
181 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
182   switch (Inst.getOperation()) {
183   default:
184     llvm_unreachable("Unexpected instruction");
185   case MCCFIInstruction::OpDefCfaOffset:
186     OutStreamer->EmitCFIDefCfaOffset(Inst.getOffset());
187     break;
188   case MCCFIInstruction::OpAdjustCfaOffset:
189     OutStreamer->EmitCFIAdjustCfaOffset(Inst.getOffset());
190     break;
191   case MCCFIInstruction::OpDefCfa:
192     OutStreamer->EmitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
193     break;
194   case MCCFIInstruction::OpDefCfaRegister:
195     OutStreamer->EmitCFIDefCfaRegister(Inst.getRegister());
196     break;
197   case MCCFIInstruction::OpOffset:
198     OutStreamer->EmitCFIOffset(Inst.getRegister(), Inst.getOffset());
199     break;
200   case MCCFIInstruction::OpRegister:
201     OutStreamer->EmitCFIRegister(Inst.getRegister(), Inst.getRegister2());
202     break;
203   case MCCFIInstruction::OpWindowSave:
204     OutStreamer->EmitCFIWindowSave();
205     break;
206   case MCCFIInstruction::OpSameValue:
207     OutStreamer->EmitCFISameValue(Inst.getRegister());
208     break;
209   case MCCFIInstruction::OpGnuArgsSize:
210     OutStreamer->EmitCFIGnuArgsSize(Inst.getOffset());
211     break;
212   case MCCFIInstruction::OpEscape:
213     OutStreamer->EmitCFIEscape(Inst.getValues());
214     break;
215   }
216 }
217 
218 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
219   // Emit the code (index) for the abbreviation.
220   if (isVerbose())
221     OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
222                             Twine::utohexstr(Die.getOffset()) + ":0x" +
223                             Twine::utohexstr(Die.getSize()) + " " +
224                             dwarf::TagString(Die.getTag()));
225   EmitULEB128(Die.getAbbrevNumber());
226 
227   // Emit the DIE attribute values.
228   for (const auto &V : Die.values()) {
229     dwarf::Attribute Attr = V.getAttribute();
230     assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");
231 
232     if (isVerbose()) {
233       OutStreamer->AddComment(dwarf::AttributeString(Attr));
234       if (Attr == dwarf::DW_AT_accessibility)
235         OutStreamer->AddComment(
236             dwarf::AccessibilityString(V.getDIEInteger().getValue()));
237     }
238 
239     // Emit an attribute using the defined form.
240     V.EmitValue(this);
241   }
242 
243   // Emit the DIE children if any.
244   if (Die.hasChildren()) {
245     for (auto &Child : Die.children())
246       emitDwarfDIE(Child);
247 
248     OutStreamer->AddComment("End Of Children Mark");
249     EmitInt8(0);
250   }
251 }
252 
253 void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
254   // Emit the abbreviations code (base 1 index.)
255   EmitULEB128(Abbrev.getNumber(), "Abbreviation Code");
256 
257   // Emit the abbreviations data.
258   Abbrev.Emit(this);
259 }
260