forked from OSchip/llvm-project
75 lines
2.1 KiB
C++
75 lines
2.1 KiB
C++
//===- MarkLive.cpp -------------------------------------------------------===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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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.
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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)
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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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