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 "llvm/ADT/Twine.h"
16 #include "llvm/BinaryFormat/Dwarf.h"
17 #include "llvm/CodeGen/AsmPrinter.h"
18 #include "llvm/CodeGen/DIE.h"
19 #include "llvm/CodeGen/MachineFunction.h"
20 #include "llvm/IR/DataLayout.h"
21 #include "llvm/MC/MCAsmInfo.h"
22 #include "llvm/MC/MCRegisterInfo.h"
23 #include "llvm/MC/MCSection.h"
24 #include "llvm/MC/MCStreamer.h"
25 #include "llvm/MC/MCSymbol.h"
26 #include "llvm/MC/MachineLocation.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Target/TargetLoweringObjectFile.h"
29 #include "llvm/Target/TargetMachine.h"
30 using namespace llvm;
31 
32 #define DEBUG_TYPE "asm-printer"
33 
34 //===----------------------------------------------------------------------===//
35 // Dwarf Emission Helper Routines
36 //===----------------------------------------------------------------------===//
37 
38 /// EmitSLEB128 - emit the specified signed leb128 value.
39 void AsmPrinter::EmitSLEB128(int64_t Value, const char *Desc) const {
40   if (isVerbose() && Desc)
41     OutStreamer->AddComment(Desc);
42 
43   OutStreamer->EmitSLEB128IntValue(Value);
44 }
45 
46 void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc) const {
47   if (isVerbose() && Desc)
48     OutStreamer->AddComment(Desc);
49 
50   OutStreamer->EmitULEB128IntValue(Value);
51 }
52 
53 /// Emit something like ".uleb128 Hi-Lo".
54 void AsmPrinter::EmitLabelDifferenceAsULEB128(const MCSymbol *Hi,
55                                               const MCSymbol *Lo) const {
56   OutStreamer->emitAbsoluteSymbolDiffAsULEB128(Hi, Lo);
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_uleb128:
68     return "uleb128";
69   case dwarf::DW_EH_PE_sleb128:
70     return "sleb128";
71   case dwarf::DW_EH_PE_udata4:
72     return "udata4";
73   case dwarf::DW_EH_PE_udata8:
74     return "udata8";
75   case dwarf::DW_EH_PE_sdata4:
76     return "sdata4";
77   case dwarf::DW_EH_PE_sdata8:
78     return "sdata8";
79   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
80     return "pcrel udata4";
81   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
82     return "pcrel sdata4";
83   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
84     return "pcrel udata8";
85   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
86     return "pcrel sdata8";
87   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4
88       :
89     return "indirect pcrel udata4";
90   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
91       :
92     return "indirect pcrel sdata4";
93   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8
94       :
95     return "indirect pcrel udata8";
96   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8
97       :
98     return "indirect pcrel sdata8";
99   }
100 
101   return "<unknown encoding>";
102 }
103 
104 /// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
105 /// encoding.  If verbose assembly output is enabled, we output comments
106 /// describing the encoding.  Desc is an optional string saying what the
107 /// encoding is specifying (e.g. "LSDA").
108 void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) const {
109   if (isVerbose()) {
110     if (Desc)
111       OutStreamer->AddComment(Twine(Desc) + " Encoding = " +
112                               Twine(DecodeDWARFEncoding(Val)));
113     else
114       OutStreamer->AddComment(Twine("Encoding = ") + DecodeDWARFEncoding(Val));
115   }
116 
117   OutStreamer->EmitIntValue(Val, 1);
118 }
119 
120 /// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
121 unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
122   if (Encoding == dwarf::DW_EH_PE_omit)
123     return 0;
124 
125   switch (Encoding & 0x07) {
126   default:
127     llvm_unreachable("Invalid encoded value.");
128   case dwarf::DW_EH_PE_absptr:
129     return MF->getDataLayout().getPointerSize();
130   case dwarf::DW_EH_PE_udata2:
131     return 2;
132   case dwarf::DW_EH_PE_udata4:
133     return 4;
134   case dwarf::DW_EH_PE_udata8:
135     return 8;
136   }
137 }
138 
139 void AsmPrinter::EmitTTypeReference(const GlobalValue *GV,
140                                     unsigned Encoding) const {
141   if (GV) {
142     const TargetLoweringObjectFile &TLOF = getObjFileLowering();
143 
144     const MCExpr *Exp =
145         TLOF.getTTypeGlobalReference(GV, Encoding, TM, MMI, *OutStreamer);
146     OutStreamer->EmitValue(Exp, GetSizeOfEncodedValue(Encoding));
147   } else
148     OutStreamer->EmitIntValue(0, GetSizeOfEncodedValue(Encoding));
149 }
150 
151 void AsmPrinter::emitDwarfSymbolReference(const MCSymbol *Label,
152                                           bool ForceOffset) const {
153   if (!ForceOffset) {
154     // On COFF targets, we have to emit the special .secrel32 directive.
155     if (MAI->needsDwarfSectionOffsetDirective()) {
156       OutStreamer->EmitCOFFSecRel32(Label, /*Offset=*/0);
157       return;
158     }
159 
160     // If the format uses relocations with dwarf, refer to the symbol directly.
161     if (MAI->doesDwarfUseRelocationsAcrossSections()) {
162       OutStreamer->EmitSymbolValue(Label, 4);
163       return;
164     }
165   }
166 
167   // Otherwise, emit it as a label difference from the start of the section.
168   EmitLabelDifference(Label, Label->getSection().getBeginSymbol(), 4);
169 }
170 
171 void AsmPrinter::emitDwarfStringOffset(DwarfStringPoolEntry S) const {
172   if (MAI->doesDwarfUseRelocationsAcrossSections()) {
173     assert(S.Symbol && "No symbol available");
174     emitDwarfSymbolReference(S.Symbol);
175     return;
176   }
177 
178   // Just emit the offset directly; no need for symbol math.
179   emitInt32(S.Offset);
180 }
181 
182 void AsmPrinter::EmitDwarfOffset(const MCSymbol *Label, uint64_t Offset) const {
183   EmitLabelPlusOffset(Label, Offset, MAI->getCodePointerSize());
184 }
185 
186 //===----------------------------------------------------------------------===//
187 // Dwarf Lowering Routines
188 //===----------------------------------------------------------------------===//
189 
190 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
191   switch (Inst.getOperation()) {
192   default:
193     llvm_unreachable("Unexpected instruction");
194   case MCCFIInstruction::OpDefCfaOffset:
195     OutStreamer->EmitCFIDefCfaOffset(Inst.getOffset());
196     break;
197   case MCCFIInstruction::OpAdjustCfaOffset:
198     OutStreamer->EmitCFIAdjustCfaOffset(Inst.getOffset());
199     break;
200   case MCCFIInstruction::OpDefCfa:
201     OutStreamer->EmitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
202     break;
203   case MCCFIInstruction::OpDefCfaRegister:
204     OutStreamer->EmitCFIDefCfaRegister(Inst.getRegister());
205     break;
206   case MCCFIInstruction::OpOffset:
207     OutStreamer->EmitCFIOffset(Inst.getRegister(), Inst.getOffset());
208     break;
209   case MCCFIInstruction::OpRegister:
210     OutStreamer->EmitCFIRegister(Inst.getRegister(), Inst.getRegister2());
211     break;
212   case MCCFIInstruction::OpWindowSave:
213     OutStreamer->EmitCFIWindowSave();
214     break;
215   case MCCFIInstruction::OpNegateRAState:
216     OutStreamer->EmitCFINegateRAState();
217     break;
218   case MCCFIInstruction::OpSameValue:
219     OutStreamer->EmitCFISameValue(Inst.getRegister());
220     break;
221   case MCCFIInstruction::OpGnuArgsSize:
222     OutStreamer->EmitCFIGnuArgsSize(Inst.getOffset());
223     break;
224   case MCCFIInstruction::OpEscape:
225     OutStreamer->EmitCFIEscape(Inst.getValues());
226     break;
227   case MCCFIInstruction::OpRestore:
228     OutStreamer->EmitCFIRestore(Inst.getRegister());
229     break;
230   }
231 }
232 
233 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
234   // Emit the code (index) for the abbreviation.
235   if (isVerbose())
236     OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
237                             Twine::utohexstr(Die.getOffset()) + ":0x" +
238                             Twine::utohexstr(Die.getSize()) + " " +
239                             dwarf::TagString(Die.getTag()));
240   EmitULEB128(Die.getAbbrevNumber());
241 
242   // Emit the DIE attribute values.
243   for (const auto &V : Die.values()) {
244     dwarf::Attribute Attr = V.getAttribute();
245     assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");
246 
247     if (isVerbose()) {
248       OutStreamer->AddComment(dwarf::AttributeString(Attr));
249       if (Attr == dwarf::DW_AT_accessibility)
250         OutStreamer->AddComment(
251             dwarf::AccessibilityString(V.getDIEInteger().getValue()));
252     }
253 
254     // Emit an attribute using the defined form.
255     V.EmitValue(this);
256   }
257 
258   // Emit the DIE children if any.
259   if (Die.hasChildren()) {
260     for (auto &Child : Die.children())
261       emitDwarfDIE(Child);
262 
263     OutStreamer->AddComment("End Of Children Mark");
264     emitInt8(0);
265   }
266 }
267 
268 void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
269   // Emit the abbreviations code (base 1 index.)
270   EmitULEB128(Abbrev.getNumber(), "Abbreviation Code");
271 
272   // Emit the abbreviations data.
273   Abbrev.Emit(this);
274 }
275