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/SmallVector.h"
15 #include "llvm/CodeGen/AsmPrinter.h"
16 #include "llvm/CodeGen/DIE.h"
17 #include "llvm/IR/DebugInfoMetadata.h"
18 #include "llvm/MC/MCStreamer.h"
19 #include <algorithm>
20 #include <cstdint>
21 
22 using namespace llvm;
23 
24 DwarfFile::DwarfFile(AsmPrinter *AP, StringRef Pref, BumpPtrAllocator &DA)
25     : Asm(AP), Abbrevs(AbbrevAllocator), StrPool(DA, *Asm, Pref) {}
26 
27 void DwarfFile::addUnit(std::unique_ptr<DwarfCompileUnit> U) {
28   CUs.push_back(std::move(U));
29 }
30 
31 // Emit the various dwarf units to the unit section USection with
32 // the abbreviations going into ASection.
33 void DwarfFile::emitUnits(bool UseOffsets) {
34   for (const auto &TheU : CUs)
35     emitUnit(TheU.get(), UseOffsets);
36 }
37 
38 void DwarfFile::emitUnit(DwarfUnit *TheU, bool UseOffsets) {
39   DIE &Die = TheU->getUnitDie();
40   MCSection *USection = TheU->getSection();
41   Asm->OutStreamer->SwitchSection(USection);
42 
43   TheU->emitHeader(UseOffsets);
44 
45   Asm->emitDwarfDIE(Die);
46 }
47 
48 // Compute the size and offset for each DIE.
49 void DwarfFile::computeSizeAndOffsets() {
50   // Offset from the first CU in the debug info section is 0 initially.
51   unsigned SecOffset = 0;
52 
53   // Iterate over each compile unit and set the size and offsets for each
54   // DIE within each compile unit. All offsets are CU relative.
55   for (const auto &TheU : CUs) {
56     TheU->setDebugSectionOffset(SecOffset);
57     SecOffset += computeSizeAndOffsetsForUnit(TheU.get());
58   }
59 }
60 
61 unsigned DwarfFile::computeSizeAndOffsetsForUnit(DwarfUnit *TheU) {
62   // CU-relative offset is reset to 0 here.
63   unsigned Offset = sizeof(int32_t) +      // Length of Unit Info
64                     TheU->getHeaderSize(); // Unit-specific headers
65 
66   // The return value here is CU-relative, after laying out
67   // all of the CU DIE.
68   return computeSizeAndOffset(TheU->getUnitDie(), Offset);
69 }
70 
71 // Compute the size and offset of a DIE. The offset is relative to start of the
72 // CU. It returns the offset after laying out the DIE.
73 unsigned DwarfFile::computeSizeAndOffset(DIE &Die, unsigned Offset) {
74   return Die.computeOffsetsAndAbbrevs(Asm, Abbrevs, Offset);
75 }
76 
77 void DwarfFile::emitAbbrevs(MCSection *Section) { Abbrevs.Emit(Asm, Section); }
78 
79 // Emit strings into a string section.
80 void DwarfFile::emitStrings(MCSection *StrSection, MCSection *OffsetSection) {
81   StrPool.emit(*Asm, StrSection, OffsetSection);
82 }
83 
84 bool DwarfFile::addScopeVariable(LexicalScope *LS, DbgVariable *Var) {
85   SmallVectorImpl<DbgVariable *> &Vars = ScopeVariables[LS];
86   const DILocalVariable *DV = Var->getVariable();
87   // Variables with positive arg numbers are parameters.
88   if (unsigned ArgNum = DV->getArg()) {
89     // Keep all parameters in order at the start of the variable list to ensure
90     // function types are correct (no out-of-order parameters)
91     //
92     // This could be improved by only doing it for optimized builds (unoptimized
93     // builds have the right order to begin with), searching from the back (this
94     // would catch the unoptimized case quickly), or doing a binary search
95     // rather than linear search.
96     auto I = Vars.begin();
97     while (I != Vars.end()) {
98       unsigned CurNum = (*I)->getVariable()->getArg();
99       // A local (non-parameter) variable has been found, insert immediately
100       // before it.
101       if (CurNum == 0)
102         break;
103       // A later indexed parameter has been found, insert immediately before it.
104       if (CurNum > ArgNum)
105         break;
106       if (CurNum == ArgNum) {
107         (*I)->addMMIEntry(*Var);
108         return false;
109       }
110       ++I;
111     }
112     Vars.insert(I, Var);
113     return true;
114   }
115 
116   Vars.push_back(Var);
117   return true;
118 }
119