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llvm-mirror/include/llvm/MC/StringTableBuilder.h
Rui Ueyama 6fe9b6d987 Make StringTableBuilder to cache hash values.
This change seems to speed up LLD a bit if it has a lot of mergeable
sections. The number is below. It's not too bad for a small patch.

Time to link Clang (debug build):

w/o patch 6.3696 seconds
w/patch   6.2746 seconds (-1.5%)

Differential Revision: http://reviews.llvm.org/D19933

llvm-svn: 268698
2016-05-06 00:51:58 +00:00

76 lines
2.0 KiB
C++

//===-- StringTableBuilder.h - String table building utility ------*- C++ -*-=//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_MC_STRINGTABLEBUILDER_H
#define LLVM_MC_STRINGTABLEBUILDER_H
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/DenseMap.h"
#include <cassert>
namespace llvm {
/// \brief Utility for building string tables with deduplicated suffixes.
class StringTableBuilder {
public:
enum Kind { ELF, WinCOFF, MachO, RAW };
private:
SmallString<256> StringTable;
DenseMap<CachedHash<StringRef>, size_t> StringIndexMap;
size_t Size = 0;
Kind K;
unsigned Alignment;
void finalizeStringTable(bool Optimize);
public:
StringTableBuilder(Kind K, unsigned Alignment = 1);
/// \brief Add a string to the builder. Returns the position of S in the
/// table. The position will be changed if finalize is used.
/// Can only be used before the table is finalized.
size_t add(StringRef S);
/// \brief Analyze the strings and build the final table. No more strings can
/// be added after this point.
void finalize();
/// Finalize the string table without reording it. In this mode, offsets
/// returned by add will still be valid.
void finalizeInOrder();
/// \brief Retrieve the string table data. Can only be used after the table
/// is finalized.
StringRef data() const {
assert(isFinalized());
return StringTable;
}
/// \brief Get the offest of a string in the string table. Can only be used
/// after the table is finalized.
size_t getOffset(StringRef S) const;
const DenseMap<CachedHash<StringRef>, size_t> &getMap() const {
return StringIndexMap;
}
size_t getSize() const { return Size; }
void clear();
private:
bool isFinalized() const {
return !StringTable.empty();
}
};
} // end llvm namespace
#endif