xref: /freebsd/contrib/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinterDwarf.cpp (revision 06e20d1babecec1f45ffda513f55a8db5f1c0f56)
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   // TODO: Support DWARF64
185   emitLabelPlusOffset(Label, Offset, 4);
186 }
187 
188 void AsmPrinter::emitCallSiteOffset(const MCSymbol *Hi, const MCSymbol *Lo,
189                                     unsigned Encoding) const {
190   // The least significant 3 bits specify the width of the encoding
191   if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
192     emitLabelDifferenceAsULEB128(Hi, Lo);
193   else
194     emitLabelDifference(Hi, Lo, GetSizeOfEncodedValue(Encoding));
195 }
196 
197 void AsmPrinter::emitCallSiteValue(uint64_t Value, unsigned Encoding) const {
198   // The least significant 3 bits specify the width of the encoding
199   if ((Encoding & 0x7) == dwarf::DW_EH_PE_uleb128)
200     emitULEB128(Value);
201   else
202     OutStreamer->emitIntValue(Value, GetSizeOfEncodedValue(Encoding));
203 }
204 
205 //===----------------------------------------------------------------------===//
206 // Dwarf Lowering Routines
207 //===----------------------------------------------------------------------===//
208 
209 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
210   switch (Inst.getOperation()) {
211   default:
212     llvm_unreachable("Unexpected instruction");
213   case MCCFIInstruction::OpDefCfaOffset:
214     OutStreamer->emitCFIDefCfaOffset(Inst.getOffset());
215     break;
216   case MCCFIInstruction::OpAdjustCfaOffset:
217     OutStreamer->emitCFIAdjustCfaOffset(Inst.getOffset());
218     break;
219   case MCCFIInstruction::OpDefCfa:
220     OutStreamer->emitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
221     break;
222   case MCCFIInstruction::OpDefCfaRegister:
223     OutStreamer->emitCFIDefCfaRegister(Inst.getRegister());
224     break;
225   case MCCFIInstruction::OpOffset:
226     OutStreamer->emitCFIOffset(Inst.getRegister(), Inst.getOffset());
227     break;
228   case MCCFIInstruction::OpRegister:
229     OutStreamer->emitCFIRegister(Inst.getRegister(), Inst.getRegister2());
230     break;
231   case MCCFIInstruction::OpWindowSave:
232     OutStreamer->emitCFIWindowSave();
233     break;
234   case MCCFIInstruction::OpNegateRAState:
235     OutStreamer->emitCFINegateRAState();
236     break;
237   case MCCFIInstruction::OpSameValue:
238     OutStreamer->emitCFISameValue(Inst.getRegister());
239     break;
240   case MCCFIInstruction::OpGnuArgsSize:
241     OutStreamer->emitCFIGnuArgsSize(Inst.getOffset());
242     break;
243   case MCCFIInstruction::OpEscape:
244     OutStreamer->emitCFIEscape(Inst.getValues());
245     break;
246   case MCCFIInstruction::OpRestore:
247     OutStreamer->emitCFIRestore(Inst.getRegister());
248     break;
249   case MCCFIInstruction::OpUndefined:
250     OutStreamer->emitCFIUndefined(Inst.getRegister());
251     break;
252   }
253 }
254 
255 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
256   // Emit the code (index) for the abbreviation.
257   if (isVerbose())
258     OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
259                             Twine::utohexstr(Die.getOffset()) + ":0x" +
260                             Twine::utohexstr(Die.getSize()) + " " +
261                             dwarf::TagString(Die.getTag()));
262   emitULEB128(Die.getAbbrevNumber());
263 
264   // Emit the DIE attribute values.
265   for (const auto &V : Die.values()) {
266     dwarf::Attribute Attr = V.getAttribute();
267     assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");
268 
269     if (isVerbose()) {
270       OutStreamer->AddComment(dwarf::AttributeString(Attr));
271       if (Attr == dwarf::DW_AT_accessibility)
272         OutStreamer->AddComment(
273             dwarf::AccessibilityString(V.getDIEInteger().getValue()));
274     }
275 
276     // Emit an attribute using the defined form.
277     V.emitValue(this);
278   }
279 
280   // Emit the DIE children if any.
281   if (Die.hasChildren()) {
282     for (auto &Child : Die.children())
283       emitDwarfDIE(Child);
284 
285     OutStreamer->AddComment("End Of Children Mark");
286     emitInt8(0);
287   }
288 }
289 
290 void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
291   // Emit the abbreviations code (base 1 index.)
292   emitULEB128(Abbrev.getNumber(), "Abbreviation Code");
293 
294   // Emit the abbreviations data.
295   Abbrev.Emit(this);
296 }
297