llvm/lld/wasm/MarkLive.cpp

//===- 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
//
//===----------------------------------------------------------------------===//
//
// This file implements --gc-sections, which is a feature to remove unused
// chunks from the output. Unused chunks are those that are not reachable from
// known root symbols or chunks. This feature is implemented as a mark-sweep
// garbage collector.
//
// Here's how it works. Each InputChunk has a "Live" bit. The bit is off by
// default. Starting with the GC-roots, visit all reachable chunks and set their
// Live bits. The Writer will then ignore chunks whose Live bits are off, so
// that such chunk are not appear in the output.
//
//===----------------------------------------------------------------------===//

#include "MarkLive.h"
#include "Config.h"
#include "InputChunks.h"
#include "InputElement.h"
#include "SymbolTable.h"
#include "Symbols.h"

#define DEBUG_TYPE …

usingnamespacellvm;
usingnamespacellvm::wasm;

namespace lld::wasm {

namespace {

class MarkLive { … };

} // namespace

void MarkLive::enqueue(Symbol *sym) { … }

void MarkLive::enqueue(InputChunk *chunk) { … }

// The ctor functions are all referenced by the synthetic callCtors
// function.  However, this function does not contain relocations so we
// have to manually mark the ctors as live.
void MarkLive::enqueueInitFunctions(const ObjFile *obj) { … }

// Mark segments flagged by segment-level no-strip. Segment-level no-strip is
// usually used to retain segments without having symbol table entry.
void MarkLive::enqueueRetainedSegments(const ObjFile *file) { … }

void MarkLive::run() { … }

void MarkLive::mark() { … }

void markLive() { … }

bool MarkLive::isCallCtorsLive() { … }

} // namespace lld::wasm