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//===- 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);
}
}
}
}
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