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 #include <cstdint>
31 using namespace llvm;
32 
33 #define DEBUG_TYPE "asm-printer"
34 
35 //===----------------------------------------------------------------------===//
36 // Dwarf Emission Helper Routines
37 //===----------------------------------------------------------------------===//
38 
39 /// EmitSLEB128 - emit the specified signed leb128 value.
40 void AsmPrinter::emitSLEB128(int64_t Value, const char *Desc) const {
41   if (isVerbose() && Desc)
42     OutStreamer->AddComment(Desc);
43 
44   OutStreamer->emitSLEB128IntValue(Value);
45 }
46 
47 void AsmPrinter::emitULEB128(uint64_t Value, const char *Desc,
48                              unsigned PadTo) const {
49   if (isVerbose() && Desc)
50     OutStreamer->AddComment(Desc);
51 
52   OutStreamer->emitULEB128IntValue(Value, PadTo);
53 }
54 
55 /// Emit something like ".uleb128 Hi-Lo".
56 void AsmPrinter::emitLabelDifferenceAsULEB128(const MCSymbol *Hi,
57                                               const MCSymbol *Lo) const {
58   OutStreamer->emitAbsoluteSymbolDiffAsULEB128(Hi, Lo);
59 }
60 
61 static const char *DecodeDWARFEncoding(unsigned Encoding) {
62   switch (Encoding) {
63   case dwarf::DW_EH_PE_absptr:
64     return "absptr";
65   case dwarf::DW_EH_PE_omit:
66     return "omit";
67   case dwarf::DW_EH_PE_pcrel:
68     return "pcrel";
69   case dwarf::DW_EH_PE_uleb128:
70     return "uleb128";
71   case dwarf::DW_EH_PE_sleb128:
72     return "sleb128";
73   case dwarf::DW_EH_PE_udata4:
74     return "udata4";
75   case dwarf::DW_EH_PE_udata8:
76     return "udata8";
77   case dwarf::DW_EH_PE_sdata4:
78     return "sdata4";
79   case dwarf::DW_EH_PE_sdata8:
80     return "sdata8";
81   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
82     return "pcrel udata4";
83   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
84     return "pcrel sdata4";
85   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
86     return "pcrel udata8";
87   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
88     return "pcrel sdata8";
89   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4
90       :
91     return "indirect pcrel udata4";
92   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
93       :
94     return "indirect pcrel sdata4";
95   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8
96       :
97     return "indirect pcrel udata8";
98   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8
99       :
100     return "indirect pcrel sdata8";
101   }
102 
103   return "<unknown encoding>";
104 }
105 
106 /// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
107 /// encoding.  If verbose assembly output is enabled, we output comments
108 /// describing the encoding.  Desc is an optional string saying what the
109 /// encoding is specifying (e.g. "LSDA").
110 void AsmPrinter::emitEncodingByte(unsigned Val, const char *Desc) const {
111   if (isVerbose()) {
112     if (Desc)
113       OutStreamer->AddComment(Twine(Desc) + " Encoding = " +
114                               Twine(DecodeDWARFEncoding(Val)));
115     else
116       OutStreamer->AddComment(Twine("Encoding = ") + DecodeDWARFEncoding(Val));
117   }
118 
119   OutStreamer->emitIntValue(Val, 1);
120 }
121 
122 /// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
123 unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
124   if (Encoding == dwarf::DW_EH_PE_omit)
125     return 0;
126 
127   switch (Encoding & 0x07) {
128   default:
129     llvm_unreachable("Invalid encoded value.");
130   case dwarf::DW_EH_PE_absptr:
131     return MF->getDataLayout().getPointerSize();
132   case dwarf::DW_EH_PE_udata2:
133     return 2;
134   case dwarf::DW_EH_PE_udata4:
135     return 4;
136   case dwarf::DW_EH_PE_udata8:
137     return 8;
138   }
139 }
140 
141 void AsmPrinter::emitTTypeReference(const GlobalValue *GV,
142                                     unsigned Encoding) const {
143   if (GV) {
144     const TargetLoweringObjectFile &TLOF = getObjFileLowering();
145 
146     const MCExpr *Exp =
147         TLOF.getTTypeGlobalReference(GV, Encoding, TM, MMI, *OutStreamer);
148     OutStreamer->emitValue(Exp, GetSizeOfEncodedValue(Encoding));
149   } else
150     OutStreamer->emitIntValue(0, GetSizeOfEncodedValue(Encoding));
151 }
152 
153 void AsmPrinter::emitDwarfSymbolReference(const MCSymbol *Label,
154                                           bool ForceOffset) const {
155   if (!ForceOffset) {
156     // On COFF targets, we have to emit the special .secrel32 directive.
157     if (MAI->needsDwarfSectionOffsetDirective()) {
158       assert(!isDwarf64() &&
159              "emitting DWARF64 is not implemented for COFF targets");
160       OutStreamer->EmitCOFFSecRel32(Label, /*Offset=*/0);
161       return;
162     }
163 
164     // If the format uses relocations with dwarf, refer to the symbol directly.
165     if (MAI->doesDwarfUseRelocationsAcrossSections()) {
166       OutStreamer->emitSymbolValue(Label, getDwarfOffsetByteSize());
167       return;
168     }
169   }
170 
171   // Otherwise, emit it as a label difference from the start of the section.
172   emitLabelDifference(Label, Label->getSection().getBeginSymbol(),
173                       getDwarfOffsetByteSize());
174 }
175 
176 void AsmPrinter::emitDwarfStringOffset(DwarfStringPoolEntry S) const {
177   if (MAI->doesDwarfUseRelocationsAcrossSections()) {
178     assert(S.Symbol && "No symbol available");
179     emitDwarfSymbolReference(S.Symbol);
180     return;
181   }
182 
183   // Just emit the offset directly; no need for symbol math.
184   OutStreamer->emitIntValue(S.Offset, getDwarfOffsetByteSize());
185 }
186 
187 void AsmPrinter::emitDwarfOffset(const MCSymbol *Label, uint64_t Offset) const {
188   emitLabelPlusOffset(Label, Offset, getDwarfOffsetByteSize());
189 }
190 
191 void AsmPrinter::emitDwarfLengthOrOffset(uint64_t Value) const {
192   assert(isDwarf64() || Value <= UINT32_MAX);
193   OutStreamer->emitIntValue(Value, getDwarfOffsetByteSize());
194 }
195 
196 void AsmPrinter::maybeEmitDwarf64Mark() const {
197   if (!isDwarf64())
198     return;
199   OutStreamer->AddComment("DWARF64 Mark");
200   OutStreamer->emitInt32(dwarf::DW_LENGTH_DWARF64);
201 }
202 
203 void AsmPrinter::emitDwarfUnitLength(uint64_t Length,
204                                      const Twine &Comment) const {
205   assert(isDwarf64() || Length <= dwarf::DW_LENGTH_lo_reserved);
206   maybeEmitDwarf64Mark();
207   OutStreamer->AddComment(Comment);
208   OutStreamer->emitIntValue(Length, getDwarfOffsetByteSize());
209 }
210 
211 void AsmPrinter::emitDwarfUnitLength(const MCSymbol *Hi, const MCSymbol *Lo,
212                                      const Twine &Comment) const {
213   maybeEmitDwarf64Mark();
214   OutStreamer->AddComment(Comment);
215   OutStreamer->emitAbsoluteSymbolDiff(Hi, Lo, getDwarfOffsetByteSize());
216 }
217 
218 void AsmPrinter::emitCallSiteOffset(const MCSymbol *Hi, const MCSymbol *Lo,
219                                     unsigned Encoding) const {
220   // The least significant 3 bits specify the width of the encoding
221   if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
222     emitLabelDifferenceAsULEB128(Hi, Lo);
223   else
224     emitLabelDifference(Hi, Lo, GetSizeOfEncodedValue(Encoding));
225 }
226 
227 void AsmPrinter::emitCallSiteValue(uint64_t Value, unsigned Encoding) const {
228   // The least significant 3 bits specify the width of the encoding
229   if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
230     emitULEB128(Value);
231   else
232     OutStreamer->emitIntValue(Value, GetSizeOfEncodedValue(Encoding));
233 }
234 
235 //===----------------------------------------------------------------------===//
236 // Dwarf Lowering Routines
237 //===----------------------------------------------------------------------===//
238 
239 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
240   switch (Inst.getOperation()) {
241   default:
242     llvm_unreachable("Unexpected instruction");
243   case MCCFIInstruction::OpDefCfaOffset:
244     OutStreamer->emitCFIDefCfaOffset(Inst.getOffset());
245     break;
246   case MCCFIInstruction::OpAdjustCfaOffset:
247     OutStreamer->emitCFIAdjustCfaOffset(Inst.getOffset());
248     break;
249   case MCCFIInstruction::OpDefCfa:
250     OutStreamer->emitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
251     break;
252   case MCCFIInstruction::OpDefCfaRegister:
253     OutStreamer->emitCFIDefCfaRegister(Inst.getRegister());
254     break;
255   case MCCFIInstruction::OpOffset:
256     OutStreamer->emitCFIOffset(Inst.getRegister(), Inst.getOffset());
257     break;
258   case MCCFIInstruction::OpRegister:
259     OutStreamer->emitCFIRegister(Inst.getRegister(), Inst.getRegister2());
260     break;
261   case MCCFIInstruction::OpWindowSave:
262     OutStreamer->emitCFIWindowSave();
263     break;
264   case MCCFIInstruction::OpNegateRAState:
265     OutStreamer->emitCFINegateRAState();
266     break;
267   case MCCFIInstruction::OpSameValue:
268     OutStreamer->emitCFISameValue(Inst.getRegister());
269     break;
270   case MCCFIInstruction::OpGnuArgsSize:
271     OutStreamer->emitCFIGnuArgsSize(Inst.getOffset());
272     break;
273   case MCCFIInstruction::OpEscape:
274     OutStreamer->AddComment(Inst.getComment());
275     OutStreamer->emitCFIEscape(Inst.getValues());
276     break;
277   case MCCFIInstruction::OpRestore:
278     OutStreamer->emitCFIRestore(Inst.getRegister());
279     break;
280   case MCCFIInstruction::OpUndefined:
281     OutStreamer->emitCFIUndefined(Inst.getRegister());
282     break;
283   }
284 }
285 
286 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
287   // Emit the code (index) for the abbreviation.
288   if (isVerbose())
289     OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
290                             Twine::utohexstr(Die.getOffset()) + ":0x" +
291                             Twine::utohexstr(Die.getSize()) + " " +
292                             dwarf::TagString(Die.getTag()));
293   emitULEB128(Die.getAbbrevNumber());
294 
295   // Emit the DIE attribute values.
296   for (const auto &V : Die.values()) {
297     dwarf::Attribute Attr = V.getAttribute();
298     assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");
299 
300     if (isVerbose()) {
301       OutStreamer->AddComment(dwarf::AttributeString(Attr));
302       if (Attr == dwarf::DW_AT_accessibility)
303         OutStreamer->AddComment(
304             dwarf::AccessibilityString(V.getDIEInteger().getValue()));
305     }
306 
307     // Emit an attribute using the defined form.
308     V.emitValue(this);
309   }
310 
311   // Emit the DIE children if any.
312   if (Die.hasChildren()) {
313     for (auto &Child : Die.children())
314       emitDwarfDIE(Child);
315 
316     OutStreamer->AddComment("End Of Children Mark");
317     emitInt8(0);
318   }
319 }
320 
321 void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
322   // Emit the abbreviations code (base 1 index.)
323   emitULEB128(Abbrev.getNumber(), "Abbreviation Code");
324 
325   // Emit the abbreviations data.
326   Abbrev.Emit(this);
327 }
328