1 //===-- AsmPrinterDwarf.cpp - AsmPrinter Dwarf Support --------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the Dwarf emissions parts of AsmPrinter.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "ByteStreamer.h"
14 #include "llvm/ADT/Twine.h"
15 #include "llvm/BinaryFormat/Dwarf.h"
16 #include "llvm/CodeGen/AsmPrinter.h"
17 #include "llvm/CodeGen/DIE.h"
18 #include "llvm/CodeGen/MachineFunction.h"
19 #include "llvm/IR/DataLayout.h"
20 #include "llvm/MC/MCAsmInfo.h"
21 #include "llvm/MC/MCRegisterInfo.h"
22 #include "llvm/MC/MCSection.h"
23 #include "llvm/MC/MCStreamer.h"
24 #include "llvm/MC/MCSymbol.h"
25 #include "llvm/MC/MachineLocation.h"
26 #include "llvm/Support/ErrorHandling.h"
27 #include "llvm/Target/TargetLoweringObjectFile.h"
28 #include "llvm/Target/TargetMachine.h"
29 using namespace llvm;
30 
31 #define DEBUG_TYPE "asm-printer"
32 
33 //===----------------------------------------------------------------------===//
34 // Dwarf Emission Helper Routines
35 //===----------------------------------------------------------------------===//
36 
37 /// EmitSLEB128 - emit the specified signed leb128 value.
38 void AsmPrinter::EmitSLEB128(int64_t Value, const char *Desc) const {
39   if (isVerbose() && Desc)
40     OutStreamer->AddComment(Desc);
41 
42   OutStreamer->EmitSLEB128IntValue(Value);
43 }
44 
45 void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc, unsigned PadTo) const {
46   if (isVerbose() && Desc)
47     OutStreamer->AddComment(Desc);
48 
49   OutStreamer->EmitULEB128IntValue(Value, PadTo);
50 }
51 
52 /// Emit something like ".uleb128 Hi-Lo".
53 void AsmPrinter::EmitLabelDifferenceAsULEB128(const MCSymbol *Hi,
54                                               const MCSymbol *Lo) const {
55   OutStreamer->emitAbsoluteSymbolDiffAsULEB128(Hi, Lo);
56 }
57 
58 static const char *DecodeDWARFEncoding(unsigned Encoding) {
59   switch (Encoding) {
60   case dwarf::DW_EH_PE_absptr:
61     return "absptr";
62   case dwarf::DW_EH_PE_omit:
63     return "omit";
64   case dwarf::DW_EH_PE_pcrel:
65     return "pcrel";
66   case dwarf::DW_EH_PE_uleb128:
67     return "uleb128";
68   case dwarf::DW_EH_PE_sleb128:
69     return "sleb128";
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 void AsmPrinter::EmitDwarfOffset(const MCSymbol *Label, uint64_t Offset) const {
182   EmitLabelPlusOffset(Label, Offset, MAI->getCodePointerSize());
183 }
184 
185 //===----------------------------------------------------------------------===//
186 // Dwarf Lowering Routines
187 //===----------------------------------------------------------------------===//
188 
189 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
190   switch (Inst.getOperation()) {
191   default:
192     llvm_unreachable("Unexpected instruction");
193   case MCCFIInstruction::OpDefCfaOffset:
194     OutStreamer->EmitCFIDefCfaOffset(Inst.getOffset());
195     break;
196   case MCCFIInstruction::OpAdjustCfaOffset:
197     OutStreamer->EmitCFIAdjustCfaOffset(Inst.getOffset());
198     break;
199   case MCCFIInstruction::OpDefCfa:
200     OutStreamer->EmitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
201     break;
202   case MCCFIInstruction::OpDefCfaRegister:
203     OutStreamer->EmitCFIDefCfaRegister(Inst.getRegister());
204     break;
205   case MCCFIInstruction::OpOffset:
206     OutStreamer->EmitCFIOffset(Inst.getRegister(), Inst.getOffset());
207     break;
208   case MCCFIInstruction::OpRegister:
209     OutStreamer->EmitCFIRegister(Inst.getRegister(), Inst.getRegister2());
210     break;
211   case MCCFIInstruction::OpWindowSave:
212     OutStreamer->EmitCFIWindowSave();
213     break;
214   case MCCFIInstruction::OpNegateRAState:
215     OutStreamer->EmitCFINegateRAState();
216     break;
217   case MCCFIInstruction::OpSameValue:
218     OutStreamer->EmitCFISameValue(Inst.getRegister());
219     break;
220   case MCCFIInstruction::OpGnuArgsSize:
221     OutStreamer->EmitCFIGnuArgsSize(Inst.getOffset());
222     break;
223   case MCCFIInstruction::OpEscape:
224     OutStreamer->EmitCFIEscape(Inst.getValues());
225     break;
226   case MCCFIInstruction::OpRestore:
227     OutStreamer->EmitCFIRestore(Inst.getRegister());
228     break;
229   }
230 }
231 
232 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
233   // Emit the code (index) for the abbreviation.
234   if (isVerbose())
235     OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
236                             Twine::utohexstr(Die.getOffset()) + ":0x" +
237                             Twine::utohexstr(Die.getSize()) + " " +
238                             dwarf::TagString(Die.getTag()));
239   EmitULEB128(Die.getAbbrevNumber());
240 
241   // Emit the DIE attribute values.
242   for (const auto &V : Die.values()) {
243     dwarf::Attribute Attr = V.getAttribute();
244     assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");
245 
246     if (isVerbose()) {
247       OutStreamer->AddComment(dwarf::AttributeString(Attr));
248       if (Attr == dwarf::DW_AT_accessibility)
249         OutStreamer->AddComment(
250             dwarf::AccessibilityString(V.getDIEInteger().getValue()));
251     }
252 
253     // Emit an attribute using the defined form.
254     V.EmitValue(this);
255   }
256 
257   // Emit the DIE children if any.
258   if (Die.hasChildren()) {
259     for (auto &Child : Die.children())
260       emitDwarfDIE(Child);
261 
262     OutStreamer->AddComment("End Of Children Mark");
263     emitInt8(0);
264   }
265 }
266 
267 void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
268   // Emit the abbreviations code (base 1 index.)
269   EmitULEB128(Abbrev.getNumber(), "Abbreviation Code");
270 
271   // Emit the abbreviations data.
272   Abbrev.Emit(this);
273 }
274