1 #include "DwarfCompileUnit.h"
2 
3 #include "llvm/CodeGen/MachineFunction.h"
4 #include "llvm/IR/DataLayout.h"
5 #include "llvm/IR/GlobalValue.h"
6 #include "llvm/IR/GlobalVariable.h"
7 #include "llvm/IR/Instruction.h"
8 #include "llvm/MC/MCAsmInfo.h"
9 #include "llvm/MC/MCStreamer.h"
10 #include "llvm/Target/TargetLoweringObjectFile.h"
11 #include "llvm/Target/TargetMachine.h"
12 #include "llvm/Target/TargetSubtargetInfo.h"
13 #include "llvm/Target/TargetRegisterInfo.h"
14 
15 namespace llvm {
16 
17 DwarfCompileUnit::DwarfCompileUnit(unsigned UID, DICompileUnit Node,
18                                    AsmPrinter *A, DwarfDebug *DW,
19                                    DwarfFile *DWU)
20     : DwarfUnit(UID, dwarf::DW_TAG_compile_unit, Node, A, DW, DWU) {
21   insertDIE(Node, &getUnitDie());
22 }
23 
24 /// addLabelAddress - Add a dwarf label attribute data and value using
25 /// DW_FORM_addr or DW_FORM_GNU_addr_index.
26 ///
27 void DwarfCompileUnit::addLabelAddress(DIE &Die, dwarf::Attribute Attribute,
28                                        const MCSymbol *Label) {
29 
30   // Don't use the address pool in non-fission or in the skeleton unit itself.
31   // FIXME: Once GDB supports this, it's probably worthwhile using the address
32   // pool from the skeleton - maybe even in non-fission (possibly fewer
33   // relocations by sharing them in the pool, but we have other ideas about how
34   // to reduce the number of relocations as well/instead).
35   if (!DD->useSplitDwarf() || !Skeleton)
36     return addLocalLabelAddress(Die, Attribute, Label);
37 
38   if (Label)
39     DD->addArangeLabel(SymbolCU(this, Label));
40 
41   unsigned idx = DD->getAddressPool().getIndex(Label);
42   DIEValue *Value = new (DIEValueAllocator) DIEInteger(idx);
43   Die.addValue(Attribute, dwarf::DW_FORM_GNU_addr_index, Value);
44 }
45 
46 void DwarfCompileUnit::addLocalLabelAddress(DIE &Die,
47                                             dwarf::Attribute Attribute,
48                                             const MCSymbol *Label) {
49   if (Label)
50     DD->addArangeLabel(SymbolCU(this, Label));
51 
52   Die.addValue(Attribute, dwarf::DW_FORM_addr,
53                Label ? (DIEValue *)new (DIEValueAllocator) DIELabel(Label)
54                      : new (DIEValueAllocator) DIEInteger(0));
55 }
56 
57 unsigned DwarfCompileUnit::getOrCreateSourceID(StringRef FileName,
58                                                StringRef DirName) {
59   // If we print assembly, we can't separate .file entries according to
60   // compile units. Thus all files will belong to the default compile unit.
61 
62   // FIXME: add a better feature test than hasRawTextSupport. Even better,
63   // extend .file to support this.
64   return Asm->OutStreamer.EmitDwarfFileDirective(
65       0, DirName, FileName,
66       Asm->OutStreamer.hasRawTextSupport() ? 0 : getUniqueID());
67 }
68 
69 // Return const expression if value is a GEP to access merged global
70 // constant. e.g.
71 // i8* getelementptr ({ i8, i8, i8, i8 }* @_MergedGlobals, i32 0, i32 0)
72 static const ConstantExpr *getMergedGlobalExpr(const Value *V) {
73   const ConstantExpr *CE = dyn_cast_or_null<ConstantExpr>(V);
74   if (!CE || CE->getNumOperands() != 3 ||
75       CE->getOpcode() != Instruction::GetElementPtr)
76     return nullptr;
77 
78   // First operand points to a global struct.
79   Value *Ptr = CE->getOperand(0);
80   if (!isa<GlobalValue>(Ptr) ||
81       !isa<StructType>(cast<PointerType>(Ptr->getType())->getElementType()))
82     return nullptr;
83 
84   // Second operand is zero.
85   const ConstantInt *CI = dyn_cast_or_null<ConstantInt>(CE->getOperand(1));
86   if (!CI || !CI->isZero())
87     return nullptr;
88 
89   // Third operand is offset.
90   if (!isa<ConstantInt>(CE->getOperand(2)))
91     return nullptr;
92 
93   return CE;
94 }
95 
96 /// getOrCreateGlobalVariableDIE - get or create global variable DIE.
97 DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(DIGlobalVariable GV) {
98   // Check for pre-existence.
99   if (DIE *Die = getDIE(GV))
100     return Die;
101 
102   assert(GV.isGlobalVariable());
103 
104   DIScope GVContext = GV.getContext();
105   DIType GTy = DD->resolve(GV.getType());
106 
107   // If this is a static data member definition, some attributes belong
108   // to the declaration DIE.
109   DIE *VariableDIE = nullptr;
110   bool IsStaticMember = false;
111   DIDerivedType SDMDecl = GV.getStaticDataMemberDeclaration();
112   if (SDMDecl.Verify()) {
113     assert(SDMDecl.isStaticMember() && "Expected static member decl");
114     // We need the declaration DIE that is in the static member's class.
115     VariableDIE = getOrCreateStaticMemberDIE(SDMDecl);
116     IsStaticMember = true;
117   }
118 
119   // If this is not a static data member definition, create the variable
120   // DIE and add the initial set of attributes to it.
121   if (!VariableDIE) {
122     // Construct the context before querying for the existence of the DIE in
123     // case such construction creates the DIE.
124     DIE *ContextDIE = getOrCreateContextDIE(GVContext);
125 
126     // Add to map.
127     VariableDIE = &createAndAddDIE(GV.getTag(), *ContextDIE, GV);
128 
129     // Add name and type.
130     addString(*VariableDIE, dwarf::DW_AT_name, GV.getDisplayName());
131     addType(*VariableDIE, GTy);
132 
133     // Add scoping info.
134     if (!GV.isLocalToUnit())
135       addFlag(*VariableDIE, dwarf::DW_AT_external);
136 
137     // Add line number info.
138     addSourceLine(*VariableDIE, GV);
139   }
140 
141   // Add location.
142   bool addToAccelTable = false;
143   DIE *VariableSpecDIE = nullptr;
144   bool isGlobalVariable = GV.getGlobal() != nullptr;
145   if (isGlobalVariable) {
146     addToAccelTable = true;
147     DIELoc *Loc = new (DIEValueAllocator) DIELoc();
148     const MCSymbol *Sym = Asm->getSymbol(GV.getGlobal());
149     if (GV.getGlobal()->isThreadLocal()) {
150       // FIXME: Make this work with -gsplit-dwarf.
151       unsigned PointerSize = Asm->getDataLayout().getPointerSize();
152       assert((PointerSize == 4 || PointerSize == 8) &&
153              "Add support for other sizes if necessary");
154       // Based on GCC's support for TLS:
155       if (!DD->useSplitDwarf()) {
156         // 1) Start with a constNu of the appropriate pointer size
157         addUInt(*Loc, dwarf::DW_FORM_data1,
158                 PointerSize == 4 ? dwarf::DW_OP_const4u : dwarf::DW_OP_const8u);
159         // 2) containing the (relocated) offset of the TLS variable
160         //    within the module's TLS block.
161         addExpr(*Loc, dwarf::DW_FORM_udata,
162                 Asm->getObjFileLowering().getDebugThreadLocalSymbol(Sym));
163       } else {
164         addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_GNU_const_index);
165         addUInt(*Loc, dwarf::DW_FORM_udata,
166                 DD->getAddressPool().getIndex(Sym, /* TLS */ true));
167       }
168       // 3) followed by a custom OP to make the debugger do a TLS lookup.
169       addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_GNU_push_tls_address);
170     } else {
171       DD->addArangeLabel(SymbolCU(this, Sym));
172       addOpAddress(*Loc, Sym);
173     }
174     // A static member's declaration is already flagged as such.
175     if (!SDMDecl.Verify() && !GV.isDefinition())
176       addFlag(*VariableDIE, dwarf::DW_AT_declaration);
177     // Do not create specification DIE if context is either compile unit
178     // or a subprogram.
179     if (GVContext && GV.isDefinition() && !GVContext.isCompileUnit() &&
180         !GVContext.isFile() && !DD->isSubprogramContext(GVContext)) {
181       // Create specification DIE.
182       VariableSpecDIE = &createAndAddDIE(dwarf::DW_TAG_variable, UnitDie);
183       addDIEEntry(*VariableSpecDIE, dwarf::DW_AT_specification, *VariableDIE);
184       addBlock(*VariableSpecDIE, dwarf::DW_AT_location, Loc);
185       // A static member's declaration is already flagged as such.
186       if (!SDMDecl.Verify())
187         addFlag(*VariableDIE, dwarf::DW_AT_declaration);
188     } else {
189       addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
190     }
191     // Add the linkage name.
192     StringRef LinkageName = GV.getLinkageName();
193     if (!LinkageName.empty())
194       // From DWARF4: DIEs to which DW_AT_linkage_name may apply include:
195       // TAG_common_block, TAG_constant, TAG_entry_point, TAG_subprogram and
196       // TAG_variable.
197       addString(IsStaticMember && VariableSpecDIE ? *VariableSpecDIE
198                                                   : *VariableDIE,
199                 DD->getDwarfVersion() >= 4 ? dwarf::DW_AT_linkage_name
200                                            : dwarf::DW_AT_MIPS_linkage_name,
201                 GlobalValue::getRealLinkageName(LinkageName));
202   } else if (const ConstantInt *CI =
203                  dyn_cast_or_null<ConstantInt>(GV.getConstant())) {
204     // AT_const_value was added when the static member was created. To avoid
205     // emitting AT_const_value multiple times, we only add AT_const_value when
206     // it is not a static member.
207     if (!IsStaticMember)
208       addConstantValue(*VariableDIE, CI, GTy);
209   } else if (const ConstantExpr *CE = getMergedGlobalExpr(GV.getConstant())) {
210     addToAccelTable = true;
211     // GV is a merged global.
212     DIELoc *Loc = new (DIEValueAllocator) DIELoc();
213     Value *Ptr = CE->getOperand(0);
214     MCSymbol *Sym = Asm->getSymbol(cast<GlobalValue>(Ptr));
215     DD->addArangeLabel(SymbolCU(this, Sym));
216     addOpAddress(*Loc, Sym);
217     addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_constu);
218     SmallVector<Value *, 3> Idx(CE->op_begin() + 1, CE->op_end());
219     addUInt(*Loc, dwarf::DW_FORM_udata,
220             Asm->getDataLayout().getIndexedOffset(Ptr->getType(), Idx));
221     addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_plus);
222     addBlock(*VariableDIE, dwarf::DW_AT_location, Loc);
223   }
224 
225   DIE *ResultDIE = VariableSpecDIE ? VariableSpecDIE : VariableDIE;
226 
227   if (addToAccelTable) {
228     DD->addAccelName(GV.getName(), *ResultDIE);
229 
230     // If the linkage name is different than the name, go ahead and output
231     // that as well into the name table.
232     if (GV.getLinkageName() != "" && GV.getName() != GV.getLinkageName())
233       DD->addAccelName(GV.getLinkageName(), *ResultDIE);
234   }
235 
236   addGlobalName(GV.getName(), *ResultDIE, GV.getContext());
237   return ResultDIE;
238 }
239 
240 void DwarfCompileUnit::addRange(RangeSpan Range) {
241   bool SameAsPrevCU = this == DD->getPrevCU();
242   DD->setPrevCU(this);
243   // If we have no current ranges just add the range and return, otherwise,
244   // check the current section and CU against the previous section and CU we
245   // emitted into and the subprogram was contained within. If these are the
246   // same then extend our current range, otherwise add this as a new range.
247   if (CURanges.empty() || !SameAsPrevCU ||
248       (&CURanges.back().getEnd()->getSection() !=
249        &Range.getEnd()->getSection())) {
250     CURanges.push_back(Range);
251     return;
252   }
253 
254   CURanges.back().setEnd(Range.getEnd());
255 }
256 
257 void DwarfCompileUnit::initStmtList(MCSymbol *DwarfLineSectionSym) {
258   // Define start line table label for each Compile Unit.
259   MCSymbol *LineTableStartSym =
260       Asm->OutStreamer.getDwarfLineTableSymbol(getUniqueID());
261 
262   stmtListIndex = UnitDie.getValues().size();
263 
264   // DW_AT_stmt_list is a offset of line number information for this
265   // compile unit in debug_line section. For split dwarf this is
266   // left in the skeleton CU and so not included.
267   // The line table entries are not always emitted in assembly, so it
268   // is not okay to use line_table_start here.
269   if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
270     addSectionLabel(UnitDie, dwarf::DW_AT_stmt_list, LineTableStartSym);
271   else
272     addSectionDelta(UnitDie, dwarf::DW_AT_stmt_list, LineTableStartSym,
273                     DwarfLineSectionSym);
274 }
275 
276 void DwarfCompileUnit::applyStmtList(DIE &D) {
277   D.addValue(dwarf::DW_AT_stmt_list,
278              UnitDie.getAbbrev().getData()[stmtListIndex].getForm(),
279              UnitDie.getValues()[stmtListIndex]);
280 }
281 
282 void DwarfCompileUnit::attachLowHighPC(DIE &D, const MCSymbol *Begin,
283                                        const MCSymbol *End) {
284   assert(Begin && "Begin label should not be null!");
285   assert(End && "End label should not be null!");
286   assert(Begin->isDefined() && "Invalid starting label");
287   assert(End->isDefined() && "Invalid end label");
288 
289   addLabelAddress(D, dwarf::DW_AT_low_pc, Begin);
290   if (DD->getDwarfVersion() < 4)
291     addLabelAddress(D, dwarf::DW_AT_high_pc, End);
292   else
293     addLabelDelta(D, dwarf::DW_AT_high_pc, End, Begin);
294 }
295 
296 // Find DIE for the given subprogram and attach appropriate DW_AT_low_pc
297 // and DW_AT_high_pc attributes. If there are global variables in this
298 // scope then create and insert DIEs for these variables.
299 DIE &DwarfCompileUnit::updateSubprogramScopeDIE(DISubprogram SP) {
300   DIE *SPDie = getOrCreateSubprogramDIE(SP);
301 
302   attachLowHighPC(*SPDie, DD->getFunctionBeginSym(), DD->getFunctionEndSym());
303   if (!DD->getCurrentFunction()->getTarget().Options.DisableFramePointerElim(
304           *DD->getCurrentFunction()))
305     addFlag(*SPDie, dwarf::DW_AT_APPLE_omit_frame_ptr);
306 
307   // Only include DW_AT_frame_base in full debug info
308   if (getCUNode().getEmissionKind() != DIBuilder::LineTablesOnly) {
309     const TargetRegisterInfo *RI =
310         Asm->TM.getSubtargetImpl()->getRegisterInfo();
311     MachineLocation Location(RI->getFrameRegister(*Asm->MF));
312     addAddress(*SPDie, dwarf::DW_AT_frame_base, Location);
313   }
314 
315   // Add name to the name table, we do this here because we're guaranteed
316   // to have concrete versions of our DW_TAG_subprogram nodes.
317   DD->addSubprogramNames(SP, *SPDie);
318 
319   return *SPDie;
320 }
321 
322 } // end llvm namespace
323