1 //===-- ListRecordBuilder.cpp ---------------------------------------------===//
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 "llvm/ADT/SmallString.h"
11 #include "llvm/DebugInfo/CodeView/ListRecordBuilder.h"
12 #include "llvm/DebugInfo/CodeView/TypeTableBuilder.h"
13
14 using namespace llvm;
15 using namespace codeview;
16
ListRecordBuilder(TypeRecordKind Kind)17 ListRecordBuilder::ListRecordBuilder(TypeRecordKind Kind)
18 : Kind(Kind), Builder(Kind) {}
19
writeListContinuation(const ListContinuationRecord & R)20 void ListRecordBuilder::writeListContinuation(const ListContinuationRecord &R) {
21 TypeRecordBuilder &Builder = getBuilder();
22
23 assert(getLastContinuationSize() < 65535 - 8 && "continuation won't fit");
24
25 Builder.writeTypeRecordKind(TypeRecordKind::ListContinuation);
26 Builder.writeUInt16(0);
27 Builder.writeTypeIndex(R.getContinuationIndex());
28
29 // End the current segment manually so that nothing comes after the
30 // continuation.
31 ContinuationOffsets.push_back(Builder.size());
32 SubrecordStart = Builder.size();
33 }
34
finishSubRecord()35 void ListRecordBuilder::finishSubRecord() {
36 // The type table inserts a 16 bit size field before each list, so factor that
37 // into our alignment padding.
38 uint32_t Remainder =
39 (Builder.size() + 2 * (ContinuationOffsets.size() + 1)) % 4;
40 if (Remainder != 0) {
41 for (int32_t PaddingBytesLeft = 4 - Remainder; PaddingBytesLeft > 0;
42 --PaddingBytesLeft) {
43 Builder.writeUInt8(LF_PAD0 + PaddingBytesLeft);
44 }
45 }
46
47 // Check if this subrecord makes the current segment not fit in 64K minus the
48 // space for a continuation record (8 bytes). If the segment does not fit,
49 // back up and insert a continuation record, sliding the current subrecord
50 // down.
51 if (getLastContinuationSize() > 65535 - 8) {
52 assert(SubrecordStart != 0 && "can't slide from the start!");
53 SmallString<128> SubrecordCopy(
54 Builder.str().slice(SubrecordStart, Builder.size()));
55 assert(SubrecordCopy.size() < 65530 && "subrecord is too large to slide!");
56 Builder.truncate(SubrecordStart);
57
58 // Write a placeholder continuation record.
59 Builder.writeTypeRecordKind(TypeRecordKind::ListContinuation);
60 Builder.writeUInt16(0);
61 Builder.writeUInt32(0);
62 ContinuationOffsets.push_back(Builder.size());
63 assert(Builder.size() == SubrecordStart + 8 && "wrong continuation size");
64 assert(getLastContinuationSize() < 65535 && "segment too big");
65
66 // Start a new list record of the appropriate kind, and copy the previous
67 // subrecord into place.
68 Builder.writeTypeRecordKind(Kind);
69 Builder.writeBytes(SubrecordCopy);
70 }
71
72 SubrecordStart = Builder.size();
73 }
74
writeListRecord(TypeTableBuilder & Table)75 TypeIndex ListRecordBuilder::writeListRecord(TypeTableBuilder &Table) {
76 // Get the continuation segments as a reversed vector of StringRefs for
77 // convenience.
78 SmallVector<StringRef, 1> Segments;
79 StringRef Data = str();
80 size_t LastEnd = 0;
81 for (size_t SegEnd : ContinuationOffsets) {
82 Segments.push_back(Data.slice(LastEnd, SegEnd));
83 LastEnd = SegEnd;
84 }
85 Segments.push_back(Data.slice(LastEnd, Builder.size()));
86
87 // Pop the last record off and emit it directly.
88 StringRef LastRec = Segments.pop_back_val();
89 TypeIndex ContinuationIndex = Table.writeRecord(LastRec);
90
91 // Emit each record with a continuation in reverse order, so that each one
92 // references the previous record.
93 for (StringRef Rec : reverse(Segments)) {
94 assert(*reinterpret_cast<const ulittle16_t *>(Rec.data()) ==
95 unsigned(Kind));
96 ulittle32_t *ContinuationPtr =
97 reinterpret_cast<ulittle32_t *>(const_cast<char *>(Rec.end())) - 1;
98 *ContinuationPtr = ContinuationIndex.getIndex();
99 ContinuationIndex = Table.writeRecord(Rec);
100 }
101 return ContinuationIndex;
102 }
103