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76 lines
2.3 KiB
76 lines
2.3 KiB
//===- MarkLive.cpp -------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "Chunks.h"
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#include "Symbols.h"
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#include "lld/Common/Timer.h"
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#include "llvm/ADT/STLExtras.h"
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#include <vector>
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namespace lld {
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namespace coff {
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static Timer gctimer("GC", Timer::root());
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// Set live bit on for each reachable chunk. Unmarked (unreachable)
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// COMDAT chunks will be ignored by Writer, so they will be excluded
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// from the final output.
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void markLive(ArrayRef<Chunk *> chunks) {
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ScopedTimer t(gctimer);
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// We build up a worklist of sections which have been marked as live. We only
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// push into the worklist when we discover an unmarked section, and we mark
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// as we push, so sections never appear twice in the list.
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SmallVector<SectionChunk *, 256> worklist;
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// COMDAT section chunks are dead by default. Add non-COMDAT chunks. Do not
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// traverse DWARF sections. They are live, but they should not keep other
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// sections alive.
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for (Chunk *c : chunks)
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if (auto *sc = dyn_cast<SectionChunk>(c))
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if (sc->live && !sc->isDWARF())
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worklist.push_back(sc);
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auto enqueue = [&](SectionChunk *c) {
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if (c->live)
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return;
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c->live = true;
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worklist.push_back(c);
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};
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auto addSym = [&](Symbol *b) {
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if (auto *sym = dyn_cast<DefinedRegular>(b))
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enqueue(sym->getChunk());
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else if (auto *sym = dyn_cast<DefinedImportData>(b))
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sym->file->live = true;
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else if (auto *sym = dyn_cast<DefinedImportThunk>(b))
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sym->wrappedSym->file->live = sym->wrappedSym->file->thunkLive = true;
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};
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// Add GC root chunks.
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for (Symbol *b : config->gcroot)
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addSym(b);
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while (!worklist.empty()) {
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SectionChunk *sc = worklist.pop_back_val();
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assert(sc->live && "We mark as live when pushing onto the worklist!");
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// Mark all symbols listed in the relocation table for this section.
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for (Symbol *b : sc->symbols())
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if (b)
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addSym(b);
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// Mark associative sections if any.
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for (SectionChunk &c : sc->children())
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enqueue(&c);
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}
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}
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}
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}
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