forked from OSchip/llvm-project
64 lines
1.7 KiB
C++
64 lines
1.7 KiB
C++
//===- ICF.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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//
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// Implements ICF (Identical COMDAT Folding)
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//
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//===----------------------------------------------------------------------===//
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#include "Chunks.h"
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#include <tuple>
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#include <unordered_set>
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#include <vector>
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namespace lld {
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namespace coff {
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namespace {
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struct Hasher {
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size_t operator()(const SectionChunk *C) const { return C->getHash(); }
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};
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struct Equals {
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bool operator()(const SectionChunk *A, const SectionChunk *B) const {
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return A->equals(B);
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}
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};
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} // anonymous namespace
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// Merge identical COMDAT sections.
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// Two sections are considered as identical when their section headers,
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// contents and relocations are all the same.
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void doICF(const std::vector<Chunk *> &Chunks) {
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std::unordered_set<SectionChunk *, Hasher, Equals> Set;
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bool Redo;
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do {
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Set.clear();
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Redo = false;
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for (Chunk *C : Chunks) {
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auto *SC = dyn_cast<SectionChunk>(C);
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if (!SC || !SC->isCOMDAT() || !SC->isLive())
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continue;
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auto P = Set.insert(SC);
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bool Inserted = P.second;
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if (Inserted)
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continue;
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SectionChunk *Existing = *P.first;
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SC->replaceWith(Existing);
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// By merging sections, two relocations that originally pointed to
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// different locations can now point to the same location.
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// So, repeat the process until a convegence is obtained.
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Redo = true;
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}
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} while (Redo);
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}
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} // namespace coff
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} // namespace lld
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