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c579a5b1d9
DWARF sections are typically live and not COMDAT, so they would be treated as GC roots. Enabling DWARF would essentially keep all code with debug info alive, preventing any section GC. Fixes PR45273 Reviewed By: mstorsjo, MaskRay Differential Revision: https://reviews.llvm.org/D76935
76 lines
2.3 KiB
C++
76 lines
2.3 KiB
C++
//===- 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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