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/CodeGen/TargetLoweringObjectFile.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/MC/MCAsmInfo.h"
23 #include "llvm/MC/MCRegisterInfo.h"
24 #include "llvm/MC/MCSection.h"
25 #include "llvm/MC/MCStreamer.h"
26 #include "llvm/MC/MCSymbol.h"
27 #include "llvm/MC/MachineLocation.h"
28 #include "llvm/Support/ErrorHandling.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 /// EmitULEB128 - emit the specified unsigned leb128 value.
47 void AsmPrinter::EmitPaddedULEB128(uint64_t Value, unsigned PadTo,
48                                    const char *Desc) const {
49   if (isVerbose() && Desc)
50     OutStreamer->AddComment(Desc);
51 
52   OutStreamer->EmitPaddedULEB128IntValue(Value, PadTo);
53 }
54 
55 void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc) const {
56   if (isVerbose() && Desc)
57     OutStreamer->AddComment(Desc);
58 
59   OutStreamer->EmitULEB128IntValue(Value);
60 }
61 
62 static const char *DecodeDWARFEncoding(unsigned Encoding) {
63   switch (Encoding) {
64   case dwarf::DW_EH_PE_absptr:
65     return "absptr";
66   case dwarf::DW_EH_PE_omit:
67     return "omit";
68   case dwarf::DW_EH_PE_pcrel:
69     return "pcrel";
70   case dwarf::DW_EH_PE_udata4:
71     return "udata4";
72   case dwarf::DW_EH_PE_udata8:
73     return "udata8";
74   case dwarf::DW_EH_PE_sdata4:
75     return "sdata4";
76   case dwarf::DW_EH_PE_sdata8:
77     return "sdata8";
78   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
79     return "pcrel udata4";
80   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
81     return "pcrel sdata4";
82   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
83     return "pcrel udata8";
84   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
85     return "pcrel sdata8";
86   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4
87       :
88     return "indirect pcrel udata4";
89   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
90       :
91     return "indirect pcrel sdata4";
92   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8
93       :
94     return "indirect pcrel udata8";
95   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8
96       :
97     return "indirect pcrel sdata8";
98   }
99 
100   return "<unknown encoding>";
101 }
102 
103 /// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
104 /// encoding.  If verbose assembly output is enabled, we output comments
105 /// describing the encoding.  Desc is an optional string saying what the
106 /// encoding is specifying (e.g. "LSDA").
107 void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) const {
108   if (isVerbose()) {
109     if (Desc)
110       OutStreamer->AddComment(Twine(Desc) + " Encoding = " +
111                               Twine(DecodeDWARFEncoding(Val)));
112     else
113       OutStreamer->AddComment(Twine("Encoding = ") + DecodeDWARFEncoding(Val));
114   }
115 
116   OutStreamer->EmitIntValue(Val, 1);
117 }
118 
119 /// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
120 unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
121   if (Encoding == dwarf::DW_EH_PE_omit)
122     return 0;
123 
124   switch (Encoding & 0x07) {
125   default:
126     llvm_unreachable("Invalid encoded value.");
127   case dwarf::DW_EH_PE_absptr:
128     return MF->getDataLayout().getPointerSize();
129   case dwarf::DW_EH_PE_udata2:
130     return 2;
131   case dwarf::DW_EH_PE_udata4:
132     return 4;
133   case dwarf::DW_EH_PE_udata8:
134     return 8;
135   }
136 }
137 
138 void AsmPrinter::EmitTTypeReference(const GlobalValue *GV,
139                                     unsigned Encoding) const {
140   if (GV) {
141     const TargetLoweringObjectFile &TLOF = getObjFileLowering();
142 
143     const MCExpr *Exp =
144         TLOF.getTTypeGlobalReference(GV, Encoding, TM, MMI, *OutStreamer);
145     OutStreamer->EmitValue(Exp, GetSizeOfEncodedValue(Encoding));
146   } else
147     OutStreamer->EmitIntValue(0, GetSizeOfEncodedValue(Encoding));
148 }
149 
150 void AsmPrinter::emitDwarfSymbolReference(const MCSymbol *Label,
151                                           bool ForceOffset) const {
152   if (!ForceOffset) {
153     // On COFF targets, we have to emit the special .secrel32 directive.
154     if (MAI->needsDwarfSectionOffsetDirective()) {
155       OutStreamer->EmitCOFFSecRel32(Label, /*Offset=*/0);
156       return;
157     }
158 
159     // If the format uses relocations with dwarf, refer to the symbol directly.
160     if (MAI->doesDwarfUseRelocationsAcrossSections()) {
161       OutStreamer->EmitSymbolValue(Label, 4);
162       return;
163     }
164   }
165 
166   // Otherwise, emit it as a label difference from the start of the section.
167   EmitLabelDifference(Label, Label->getSection().getBeginSymbol(), 4);
168 }
169 
170 void AsmPrinter::emitDwarfStringOffset(DwarfStringPoolEntry S) const {
171   if (MAI->doesDwarfUseRelocationsAcrossSections()) {
172     assert(S.Symbol && "No symbol available");
173     emitDwarfSymbolReference(S.Symbol);
174     return;
175   }
176 
177   // Just emit the offset directly; no need for symbol math.
178   EmitInt32(S.Offset);
179 }
180 
181 //===----------------------------------------------------------------------===//
182 // Dwarf Lowering Routines
183 //===----------------------------------------------------------------------===//
184 
185 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
186   switch (Inst.getOperation()) {
187   default:
188     llvm_unreachable("Unexpected instruction");
189   case MCCFIInstruction::OpDefCfaOffset:
190     OutStreamer->EmitCFIDefCfaOffset(Inst.getOffset());
191     break;
192   case MCCFIInstruction::OpAdjustCfaOffset:
193     OutStreamer->EmitCFIAdjustCfaOffset(Inst.getOffset());
194     break;
195   case MCCFIInstruction::OpDefCfa:
196     OutStreamer->EmitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
197     break;
198   case MCCFIInstruction::OpDefCfaRegister:
199     OutStreamer->EmitCFIDefCfaRegister(Inst.getRegister());
200     break;
201   case MCCFIInstruction::OpOffset:
202     OutStreamer->EmitCFIOffset(Inst.getRegister(), Inst.getOffset());
203     break;
204   case MCCFIInstruction::OpRegister:
205     OutStreamer->EmitCFIRegister(Inst.getRegister(), Inst.getRegister2());
206     break;
207   case MCCFIInstruction::OpWindowSave:
208     OutStreamer->EmitCFIWindowSave();
209     break;
210   case MCCFIInstruction::OpSameValue:
211     OutStreamer->EmitCFISameValue(Inst.getRegister());
212     break;
213   case MCCFIInstruction::OpGnuArgsSize:
214     OutStreamer->EmitCFIGnuArgsSize(Inst.getOffset());
215     break;
216   case MCCFIInstruction::OpEscape:
217     OutStreamer->EmitCFIEscape(Inst.getValues());
218     break;
219   case MCCFIInstruction::OpRestore:
220     OutStreamer->EmitCFIRestore(Inst.getRegister());
221     break;
222   }
223 }
224 
225 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
226   // Emit the code (index) for the abbreviation.
227   if (isVerbose())
228     OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
229                             Twine::utohexstr(Die.getOffset()) + ":0x" +
230                             Twine::utohexstr(Die.getSize()) + " " +
231                             dwarf::TagString(Die.getTag()));
232   EmitULEB128(Die.getAbbrevNumber());
233 
234   // Emit the DIE attribute values.
235   for (const auto &V : Die.values()) {
236     dwarf::Attribute Attr = V.getAttribute();
237     assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");
238 
239     if (isVerbose()) {
240       OutStreamer->AddComment(dwarf::AttributeString(Attr));
241       if (Attr == dwarf::DW_AT_accessibility)
242         OutStreamer->AddComment(
243             dwarf::AccessibilityString(V.getDIEInteger().getValue()));
244     }
245 
246     // Emit an attribute using the defined form.
247     V.EmitValue(this);
248   }
249 
250   // Emit the DIE children if any.
251   if (Die.hasChildren()) {
252     for (auto &Child : Die.children())
253       emitDwarfDIE(Child);
254 
255     OutStreamer->AddComment("End Of Children Mark");
256     EmitInt8(0);
257   }
258 }
259 
260 void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
261   // Emit the abbreviations code (base 1 index.)
262   EmitULEB128(Abbrev.getNumber(), "Abbreviation Code");
263 
264   // Emit the abbreviations data.
265   Abbrev.Emit(this);
266 }
267