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/MCDwarf.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,
47                              unsigned PadTo) const {
48   if (isVerbose() && Desc)
49     OutStreamer->AddComment(Desc);
50 
51   OutStreamer->emitULEB128IntValue(Value, PadTo);
52 }
53 
54 /// Emit something like ".uleb128 Hi-Lo".
55 void AsmPrinter::emitLabelDifferenceAsULEB128(const MCSymbol *Hi,
56                                               const MCSymbol *Lo) const {
57   OutStreamer->emitAbsoluteSymbolDiffAsULEB128(Hi, Lo);
58 }
59 
60 static const char *DecodeDWARFEncoding(unsigned Encoding) {
61   switch (Encoding) {
62   case dwarf::DW_EH_PE_absptr:
63     return "absptr";
64   case dwarf::DW_EH_PE_omit:
65     return "omit";
66   case dwarf::DW_EH_PE_pcrel:
67     return "pcrel";
68   case dwarf::DW_EH_PE_uleb128:
69     return "uleb128";
70   case dwarf::DW_EH_PE_sleb128:
71     return "sleb128";
72   case dwarf::DW_EH_PE_udata4:
73     return "udata4";
74   case dwarf::DW_EH_PE_udata8:
75     return "udata8";
76   case dwarf::DW_EH_PE_sdata4:
77     return "sdata4";
78   case dwarf::DW_EH_PE_sdata8:
79     return "sdata8";
80   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
81     return "pcrel udata4";
82   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
83     return "pcrel sdata4";
84   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
85     return "pcrel udata8";
86   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
87     return "pcrel sdata8";
88   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4
89       :
90     return "indirect pcrel udata4";
91   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
92       :
93     return "indirect pcrel sdata4";
94   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8
95       :
96     return "indirect pcrel udata8";
97   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8
98       :
99     return "indirect pcrel sdata8";
100   }
101 
102   return "<unknown encoding>";
103 }
104 
105 /// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
106 /// encoding.  If verbose assembly output is enabled, we output comments
107 /// describing the encoding.  Desc is an optional string saying what the
108 /// encoding is specifying (e.g. "LSDA").
109 void AsmPrinter::emitEncodingByte(unsigned Val, const char *Desc) const {
110   if (isVerbose()) {
111     if (Desc)
112       OutStreamer->AddComment(Twine(Desc) + " Encoding = " +
113                               Twine(DecodeDWARFEncoding(Val)));
114     else
115       OutStreamer->AddComment(Twine("Encoding = ") + DecodeDWARFEncoding(Val));
116   }
117 
118   OutStreamer->emitIntValue(Val, 1);
119 }
120 
121 /// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
122 unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
123   if (Encoding == dwarf::DW_EH_PE_omit)
124     return 0;
125 
126   switch (Encoding & 0x07) {
127   default:
128     llvm_unreachable("Invalid encoded value.");
129   case dwarf::DW_EH_PE_absptr:
130     return MF->getDataLayout().getPointerSize();
131   case dwarf::DW_EH_PE_udata2:
132     return 2;
133   case dwarf::DW_EH_PE_udata4:
134     return 4;
135   case dwarf::DW_EH_PE_udata8:
136     return 8;
137   }
138 }
139 
140 void AsmPrinter::emitTTypeReference(const GlobalValue *GV,
141                                     unsigned Encoding) const {
142   if (GV) {
143     const TargetLoweringObjectFile &TLOF = getObjFileLowering();
144 
145     const MCExpr *Exp =
146         TLOF.getTTypeGlobalReference(GV, Encoding, TM, MMI, *OutStreamer);
147     OutStreamer->emitValue(Exp, GetSizeOfEncodedValue(Encoding));
148   } else
149     OutStreamer->emitIntValue(0, GetSizeOfEncodedValue(Encoding));
150 }
151 
152 void AsmPrinter::emitDwarfSymbolReference(const MCSymbol *Label,
153                                           bool ForceOffset) const {
154   if (!ForceOffset) {
155     // On COFF targets, we have to emit the special .secrel32 directive.
156     if (MAI->needsDwarfSectionOffsetDirective()) {
157       OutStreamer->EmitCOFFSecRel32(Label, /*Offset=*/0);
158       return;
159     }
160 
161     // If the format uses relocations with dwarf, refer to the symbol directly.
162     if (MAI->doesDwarfUseRelocationsAcrossSections()) {
163       OutStreamer->emitSymbolValue(Label, 4);
164       return;
165     }
166   }
167 
168   // Otherwise, emit it as a label difference from the start of the section.
169   emitLabelDifference(Label, Label->getSection().getBeginSymbol(), 4);
170 }
171 
172 void AsmPrinter::emitDwarfStringOffset(DwarfStringPoolEntry S) const {
173   if (MAI->doesDwarfUseRelocationsAcrossSections()) {
174     assert(S.Symbol && "No symbol available");
175     emitDwarfSymbolReference(S.Symbol);
176     return;
177   }
178 
179   // Just emit the offset directly; no need for symbol math.
180   emitInt32(S.Offset);
181 }
182 
183 void AsmPrinter::emitDwarfOffset(const MCSymbol *Label, uint64_t Offset) const {
184   emitLabelPlusOffset(Label, Offset, MAI->getCodePointerSize());
185 }
186 
187 void AsmPrinter::emitCallSiteOffset(const MCSymbol *Hi, const MCSymbol *Lo,
188                                     unsigned Encoding) const {
189   // The least significant 3 bits specify the width of the encoding
190   if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
191     emitLabelDifferenceAsULEB128(Hi, Lo);
192   else
193     emitLabelDifference(Hi, Lo, GetSizeOfEncodedValue(Encoding));
194 }
195 
196 void AsmPrinter::emitCallSiteValue(uint64_t Value, unsigned Encoding) const {
197   // The least significant 3 bits specify the width of the encoding
198   if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
199     emitULEB128(Value);
200   else
201     OutStreamer->emitIntValue(Value, GetSizeOfEncodedValue(Encoding));
202 }
203 
204 //===----------------------------------------------------------------------===//
205 // Dwarf Lowering Routines
206 //===----------------------------------------------------------------------===//
207 
208 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
209   switch (Inst.getOperation()) {
210   default:
211     llvm_unreachable("Unexpected instruction");
212   case MCCFIInstruction::OpDefCfaOffset:
213     OutStreamer->emitCFIDefCfaOffset(Inst.getOffset());
214     break;
215   case MCCFIInstruction::OpAdjustCfaOffset:
216     OutStreamer->emitCFIAdjustCfaOffset(Inst.getOffset());
217     break;
218   case MCCFIInstruction::OpDefCfa:
219     OutStreamer->emitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
220     break;
221   case MCCFIInstruction::OpDefCfaRegister:
222     OutStreamer->emitCFIDefCfaRegister(Inst.getRegister());
223     break;
224   case MCCFIInstruction::OpOffset:
225     OutStreamer->emitCFIOffset(Inst.getRegister(), Inst.getOffset());
226     break;
227   case MCCFIInstruction::OpRegister:
228     OutStreamer->emitCFIRegister(Inst.getRegister(), Inst.getRegister2());
229     break;
230   case MCCFIInstruction::OpWindowSave:
231     OutStreamer->emitCFIWindowSave();
232     break;
233   case MCCFIInstruction::OpNegateRAState:
234     OutStreamer->emitCFINegateRAState();
235     break;
236   case MCCFIInstruction::OpSameValue:
237     OutStreamer->emitCFISameValue(Inst.getRegister());
238     break;
239   case MCCFIInstruction::OpGnuArgsSize:
240     OutStreamer->emitCFIGnuArgsSize(Inst.getOffset());
241     break;
242   case MCCFIInstruction::OpEscape:
243     OutStreamer->emitCFIEscape(Inst.getValues());
244     break;
245   case MCCFIInstruction::OpRestore:
246     OutStreamer->emitCFIRestore(Inst.getRegister());
247     break;
248   case MCCFIInstruction::OpUndefined:
249     OutStreamer->emitCFIUndefined(Inst.getRegister());
250     break;
251   }
252 }
253 
254 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
255   // Emit the code (index) for the abbreviation.
256   if (isVerbose())
257     OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
258                             Twine::utohexstr(Die.getOffset()) + ":0x" +
259                             Twine::utohexstr(Die.getSize()) + " " +
260                             dwarf::TagString(Die.getTag()));
261   emitULEB128(Die.getAbbrevNumber());
262 
263   // Emit the DIE attribute values.
264   for (const auto &V : Die.values()) {
265     dwarf::Attribute Attr = V.getAttribute();
266     assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");
267 
268     if (isVerbose()) {
269       OutStreamer->AddComment(dwarf::AttributeString(Attr));
270       if (Attr == dwarf::DW_AT_accessibility)
271         OutStreamer->AddComment(
272             dwarf::AccessibilityString(V.getDIEInteger().getValue()));
273     }
274 
275     // Emit an attribute using the defined form.
276     V.emitValue(this);
277   }
278 
279   // Emit the DIE children if any.
280   if (Die.hasChildren()) {
281     for (auto &Child : Die.children())
282       emitDwarfDIE(Child);
283 
284     OutStreamer->AddComment("End Of Children Mark");
285     emitInt8(0);
286   }
287 }
288 
289 void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
290   // Emit the abbreviations code (base 1 index.)
291   emitULEB128(Abbrev.getNumber(), "Abbreviation Code");
292 
293   // Emit the abbreviations data.
294   Abbrev.Emit(this);
295 }
296