1 //===-- llvm/CodeGen/DwarfFile.cpp - Dwarf Debug Framework ----------------===//
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 #include "DwarfFile.h"
11 #include "DwarfCompileUnit.h"
12 #include "DwarfDebug.h"
13 #include "DwarfUnit.h"
14 #include "llvm/ADT/STLExtras.h"
15 #include "llvm/IR/DataLayout.h"
16 #include "llvm/MC/MCStreamer.h"
17 #include "llvm/Support/LEB128.h"
18 #include "llvm/Target/TargetLoweringObjectFile.h"
19 
20 namespace llvm {
21 DwarfFile::DwarfFile(AsmPrinter *AP, StringRef Pref, BumpPtrAllocator &DA)
22     : Asm(AP), Abbrevs(AbbrevAllocator), StrPool(DA, *Asm, Pref) {}
23 
24 void DwarfFile::addUnit(std::unique_ptr<DwarfCompileUnit> U) {
25   CUs.push_back(std::move(U));
26 }
27 
28 // Emit the various dwarf units to the unit section USection with
29 // the abbreviations going into ASection.
30 void DwarfFile::emitUnits(bool UseOffsets) {
31   for (const auto &TheU : CUs)
32     emitUnit(TheU.get(), UseOffsets);
33 }
34 
35 void DwarfFile::emitUnit(DwarfUnit *TheU, bool UseOffsets) {
36   DIE &Die = TheU->getUnitDie();
37   MCSection *USection = TheU->getSection();
38   Asm->OutStreamer->SwitchSection(USection);
39 
40   TheU->emitHeader(UseOffsets);
41 
42   Asm->emitDwarfDIE(Die);
43 }
44 
45 // Compute the size and offset for each DIE.
46 void DwarfFile::computeSizeAndOffsets() {
47   // Offset from the first CU in the debug info section is 0 initially.
48   unsigned SecOffset = 0;
49 
50   // Iterate over each compile unit and set the size and offsets for each
51   // DIE within each compile unit. All offsets are CU relative.
52   for (const auto &TheU : CUs) {
53     TheU->setDebugSectionOffset(SecOffset);
54     SecOffset += computeSizeAndOffsetsForUnit(TheU.get());
55   }
56 }
57 
58 unsigned DwarfFile::computeSizeAndOffsetsForUnit(DwarfUnit *TheU) {
59   // CU-relative offset is reset to 0 here.
60   unsigned Offset = sizeof(int32_t) +      // Length of Unit Info
61                     TheU->getHeaderSize(); // Unit-specific headers
62 
63   // The return value here is CU-relative, after laying out
64   // all of the CU DIE.
65   return computeSizeAndOffset(TheU->getUnitDie(), Offset);
66 }
67 
68 // Compute the size and offset of a DIE. The offset is relative to start of the
69 // CU. It returns the offset after laying out the DIE.
70 unsigned DwarfFile::computeSizeAndOffset(DIE &Die, unsigned Offset) {
71   return Die.computeOffsetsAndAbbrevs(Asm, Abbrevs, Offset);
72 }
73 
74 void DwarfFile::emitAbbrevs(MCSection *Section) { Abbrevs.Emit(Asm, Section); }
75 
76 // Emit strings into a string section.
77 void DwarfFile::emitStrings(MCSection *StrSection, MCSection *OffsetSection) {
78   StrPool.emit(*Asm, StrSection, OffsetSection);
79 }
80 
81 bool DwarfFile::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
82   SmallVectorImpl<DbgVariable *> &Vars = ScopeVariables[LS];
83   const DILocalVariable *DV = Var->getVariable();
84   // Variables with positive arg numbers are parameters.
85   if (unsigned ArgNum = DV->getArg()) {
86     // Keep all parameters in order at the start of the variable list to ensure
87     // function types are correct (no out-of-order parameters)
88     //
89     // This could be improved by only doing it for optimized builds (unoptimized
90     // builds have the right order to begin with), searching from the back (this
91     // would catch the unoptimized case quickly), or doing a binary search
92     // rather than linear search.
93     auto I = Vars.begin();
94     while (I != Vars.end()) {
95       unsigned CurNum = (*I)->getVariable()->getArg();
96       // A local (non-parameter) variable has been found, insert immediately
97       // before it.
98       if (CurNum == 0)
99         break;
100       // A later indexed parameter has been found, insert immediately before it.
101       if (CurNum > ArgNum)
102         break;
103       if (CurNum == ArgNum) {
104         (*I)->addMMIEntry(*Var);
105         return false;
106       }
107       ++I;
108     }
109     Vars.insert(I, Var);
110     return true;
111   }
112 
113   Vars.push_back(Var);
114   return true;
115 }
116 }
117