1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
| //===- MarkLive.cpp -------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "Chunks.h"
#include "Symbols.h"
#include "lld/Common/Timer.h"
#include "llvm/ADT/STLExtras.h"
#include <vector>
namespace lld {
namespace coff {
static Timer gctimer("GC", Timer::root());
// Set live bit on for each reachable chunk. Unmarked (unreachable)
// COMDAT chunks will be ignored by Writer, so they will be excluded
// from the final output.
void markLive(ArrayRef<Chunk *> chunks) {
ScopedTimer t(gctimer);
// We build up a worklist of sections which have been marked as live. We only
// push into the worklist when we discover an unmarked section, and we mark
// as we push, so sections never appear twice in the list.
SmallVector<SectionChunk *, 256> worklist;
// COMDAT section chunks are dead by default. Add non-COMDAT chunks.
for (Chunk *c : chunks)
if (auto *sc = dyn_cast<SectionChunk>(c))
if (sc->live)
worklist.push_back(sc);
auto enqueue = [&](SectionChunk *c) {
if (c->live)
return;
c->live = true;
worklist.push_back(c);
};
auto addSym = [&](Symbol *b) {
if (auto *sym = dyn_cast<DefinedRegular>(b))
enqueue(sym->getChunk());
else if (auto *sym = dyn_cast<DefinedImportData>(b))
sym->file->live = true;
else if (auto *sym = dyn_cast<DefinedImportThunk>(b))
sym->wrappedSym->file->live = sym->wrappedSym->file->thunkLive = true;
};
// Add GC root chunks.
for (Symbol *b : config->gcroot)
addSym(b);
while (!worklist.empty()) {
SectionChunk *sc = worklist.pop_back_val();
assert(sc->live && "We mark as live when pushing onto the worklist!");
// Mark all symbols listed in the relocation table for this section.
for (Symbol *b : sc->symbols())
if (b)
addSym(b);
// Mark associative sections if any.
for (SectionChunk &c : sc->children())
enqueue(&c);
}
}
}
}
|