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 "DwarfDebug.h"
16 #include "DwarfExpression.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/CodeGen/AsmPrinter.h"
19 #include "llvm/CodeGen/DIE.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineModuleInfo.h"
22 #include "llvm/IR/DataLayout.h"
23 #include "llvm/MC/MCAsmInfo.h"
24 #include "llvm/MC/MCRegisterInfo.h"
25 #include "llvm/MC/MCSection.h"
26 #include "llvm/MC/MCStreamer.h"
27 #include "llvm/MC/MCSymbol.h"
28 #include "llvm/MC/MachineLocation.h"
29 #include "llvm/Support/Dwarf.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Target/TargetLoweringObjectFile.h"
32 #include "llvm/Target/TargetMachine.h"
33 #include "llvm/Target/TargetSubtargetInfo.h"
34 using namespace llvm;
35 
36 #define DEBUG_TYPE "asm-printer"
37 
38 //===----------------------------------------------------------------------===//
39 // Dwarf Emission Helper Routines
40 //===----------------------------------------------------------------------===//
41 
42 /// EmitSLEB128 - emit the specified signed leb128 value.
43 void AsmPrinter::EmitSLEB128(int64_t Value, const char *Desc) const {
44   if (isVerbose() && Desc)
45     OutStreamer->AddComment(Desc);
46 
47   OutStreamer->EmitSLEB128IntValue(Value);
48 }
49 
50 /// EmitULEB128 - emit the specified unsigned leb128 value.
51 void AsmPrinter::EmitULEB128(uint64_t Value, const char *Desc,
52                              unsigned PadTo) const {
53   if (isVerbose() && Desc)
54     OutStreamer->AddComment(Desc);
55 
56   OutStreamer->EmitULEB128IntValue(Value, PadTo);
57 }
58 
59 static const char *DecodeDWARFEncoding(unsigned Encoding) {
60   switch (Encoding) {
61   case dwarf::DW_EH_PE_absptr:
62     return "absptr";
63   case dwarf::DW_EH_PE_omit:
64     return "omit";
65   case dwarf::DW_EH_PE_pcrel:
66     return "pcrel";
67   case dwarf::DW_EH_PE_udata4:
68     return "udata4";
69   case dwarf::DW_EH_PE_udata8:
70     return "udata8";
71   case dwarf::DW_EH_PE_sdata4:
72     return "sdata4";
73   case dwarf::DW_EH_PE_sdata8:
74     return "sdata8";
75   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
76     return "pcrel udata4";
77   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
78     return "pcrel sdata4";
79   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
80     return "pcrel udata8";
81   case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
82     return "pcrel sdata8";
83   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4
84       :
85     return "indirect pcrel udata4";
86   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
87       :
88     return "indirect pcrel sdata4";
89   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8
90       :
91     return "indirect pcrel udata8";
92   case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8
93       :
94     return "indirect pcrel sdata8";
95   }
96 
97   return "<unknown encoding>";
98 }
99 
100 /// EmitEncodingByte - Emit a .byte 42 directive that corresponds to an
101 /// encoding.  If verbose assembly output is enabled, we output comments
102 /// describing the encoding.  Desc is an optional string saying what the
103 /// encoding is specifying (e.g. "LSDA").
104 void AsmPrinter::EmitEncodingByte(unsigned Val, const char *Desc) const {
105   if (isVerbose()) {
106     if (Desc)
107       OutStreamer->AddComment(Twine(Desc) + " Encoding = " +
108                               Twine(DecodeDWARFEncoding(Val)));
109     else
110       OutStreamer->AddComment(Twine("Encoding = ") + DecodeDWARFEncoding(Val));
111   }
112 
113   OutStreamer->EmitIntValue(Val, 1);
114 }
115 
116 /// GetSizeOfEncodedValue - Return the size of the encoding in bytes.
117 unsigned AsmPrinter::GetSizeOfEncodedValue(unsigned Encoding) const {
118   if (Encoding == dwarf::DW_EH_PE_omit)
119     return 0;
120 
121   switch (Encoding & 0x07) {
122   default:
123     llvm_unreachable("Invalid encoded value.");
124   case dwarf::DW_EH_PE_absptr:
125     return MF->getDataLayout().getPointerSize();
126   case dwarf::DW_EH_PE_udata2:
127     return 2;
128   case dwarf::DW_EH_PE_udata4:
129     return 4;
130   case dwarf::DW_EH_PE_udata8:
131     return 8;
132   }
133 }
134 
135 void AsmPrinter::EmitTTypeReference(const GlobalValue *GV,
136                                     unsigned Encoding) const {
137   if (GV) {
138     const TargetLoweringObjectFile &TLOF = getObjFileLowering();
139 
140     const MCExpr *Exp =
141         TLOF.getTTypeGlobalReference(GV, Encoding, TM, MMI, *OutStreamer);
142     OutStreamer->EmitValue(Exp, GetSizeOfEncodedValue(Encoding));
143   } else
144     OutStreamer->EmitIntValue(0, GetSizeOfEncodedValue(Encoding));
145 }
146 
147 void AsmPrinter::emitDwarfSymbolReference(const MCSymbol *Label,
148                                           bool ForceOffset) const {
149   if (!ForceOffset) {
150     // On COFF targets, we have to emit the special .secrel32 directive.
151     if (MAI->needsDwarfSectionOffsetDirective()) {
152       OutStreamer->EmitCOFFSecRel32(Label);
153       return;
154     }
155 
156     // If the format uses relocations with dwarf, refer to the symbol directly.
157     if (MAI->doesDwarfUseRelocationsAcrossSections()) {
158       OutStreamer->EmitSymbolValue(Label, 4);
159       return;
160     }
161   }
162 
163   // Otherwise, emit it as a label difference from the start of the section.
164   EmitLabelDifference(Label, Label->getSection().getBeginSymbol(), 4);
165 }
166 
167 void AsmPrinter::emitDwarfStringOffset(DwarfStringPoolEntryRef S) const {
168   if (MAI->doesDwarfUseRelocationsAcrossSections()) {
169     emitDwarfSymbolReference(S.getSymbol());
170     return;
171   }
172 
173   // Just emit the offset directly; no need for symbol math.
174   EmitInt32(S.getOffset());
175 }
176 
177 /// EmitDwarfRegOp - Emit dwarf register operation.
178 void AsmPrinter::EmitDwarfRegOp(ByteStreamer &Streamer,
179                                 const MachineLocation &MLoc) const {
180   DebugLocDwarfExpression Expr(getDwarfDebug()->getDwarfVersion(), Streamer);
181   const MCRegisterInfo *MRI = MMI->getContext().getRegisterInfo();
182   int Reg = MRI->getDwarfRegNum(MLoc.getReg(), false);
183   if (Reg < 0) {
184     // We assume that pointers are always in an addressable register.
185     if (MLoc.isIndirect())
186       // FIXME: We have no reasonable way of handling errors in here. The
187       // caller might be in the middle of a dwarf expression. We should
188       // probably assert that Reg >= 0 once debug info generation is more
189       // mature.
190       return Expr.EmitOp(dwarf::DW_OP_nop,
191                          "nop (could not find a dwarf register number)");
192 
193     // Attempt to find a valid super- or sub-register.
194     if (!Expr.AddMachineRegPiece(*MF->getSubtarget().getRegisterInfo(),
195                                  MLoc.getReg()))
196       Expr.EmitOp(dwarf::DW_OP_nop,
197                   "nop (could not find a dwarf register number)");
198     return;
199   }
200 
201   if (MLoc.isIndirect())
202     Expr.AddRegIndirect(Reg, MLoc.getOffset());
203   else
204     Expr.AddReg(Reg);
205 }
206 
207 //===----------------------------------------------------------------------===//
208 // Dwarf Lowering Routines
209 //===----------------------------------------------------------------------===//
210 
211 void AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst) const {
212   switch (Inst.getOperation()) {
213   default:
214     llvm_unreachable("Unexpected instruction");
215   case MCCFIInstruction::OpDefCfaOffset:
216     OutStreamer->EmitCFIDefCfaOffset(Inst.getOffset());
217     break;
218   case MCCFIInstruction::OpAdjustCfaOffset:
219     OutStreamer->EmitCFIAdjustCfaOffset(Inst.getOffset());
220     break;
221   case MCCFIInstruction::OpDefCfa:
222     OutStreamer->EmitCFIDefCfa(Inst.getRegister(), Inst.getOffset());
223     break;
224   case MCCFIInstruction::OpDefCfaRegister:
225     OutStreamer->EmitCFIDefCfaRegister(Inst.getRegister());
226     break;
227   case MCCFIInstruction::OpOffset:
228     OutStreamer->EmitCFIOffset(Inst.getRegister(), Inst.getOffset());
229     break;
230   case MCCFIInstruction::OpRegister:
231     OutStreamer->EmitCFIRegister(Inst.getRegister(), Inst.getRegister2());
232     break;
233   case MCCFIInstruction::OpWindowSave:
234     OutStreamer->EmitCFIWindowSave();
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   }
246 }
247 
248 void AsmPrinter::emitDwarfDIE(const DIE &Die) const {
249   // Emit the code (index) for the abbreviation.
250   if (isVerbose())
251     OutStreamer->AddComment("Abbrev [" + Twine(Die.getAbbrevNumber()) + "] 0x" +
252                             Twine::utohexstr(Die.getOffset()) + ":0x" +
253                             Twine::utohexstr(Die.getSize()) + " " +
254                             dwarf::TagString(Die.getTag()));
255   EmitULEB128(Die.getAbbrevNumber());
256 
257   // Emit the DIE attribute values.
258   for (const auto &V : Die.values()) {
259     dwarf::Attribute Attr = V.getAttribute();
260     assert(V.getForm() && "Too many attributes for DIE (check abbreviation)");
261 
262     if (isVerbose()) {
263       OutStreamer->AddComment(dwarf::AttributeString(Attr));
264       if (Attr == dwarf::DW_AT_accessibility)
265         OutStreamer->AddComment(
266             dwarf::AccessibilityString(V.getDIEInteger().getValue()));
267     }
268 
269     // Emit an attribute using the defined form.
270     V.EmitValue(this);
271   }
272 
273   // Emit the DIE children if any.
274   if (Die.hasChildren()) {
275     for (auto &Child : Die.children())
276       emitDwarfDIE(Child);
277 
278     OutStreamer->AddComment("End Of Children Mark");
279     EmitInt8(0);
280   }
281 }
282 
283 void AsmPrinter::emitDwarfAbbrev(const DIEAbbrev &Abbrev) const {
284   // Emit the abbreviations code (base 1 index.)
285   EmitULEB128(Abbrev.getNumber(), "Abbreviation Code");
286 
287   // Emit the abbreviations data.
288   Abbrev.Emit(this);
289 }
290