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MachObjectWriter: optimize the string table for common suffices

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This is a follow-up to r207670 (ELF) and r218636 (COFF).

Differential Revision: http://reviews.llvm.org/D5622

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219126 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hans Wennborg
2014-10-06 17:05:19 +00:00
parent 3e3908e2c7
commit 7fcd5f8c89
28 changed files with 298 additions and 302 deletions
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lib/MC/MachObjectWriter.cpp
+24 -43
View File
@@ -525,15 +525,10 @@ void MachObjectWriter::BindIndirectSymbols(MCAssembler &Asm) {
}
/// ComputeSymbolTable - Compute the symbol table data
///
/// \param StringTable [out] - The string table data.
/// \param StringIndexMap [out] - Map from symbol names to offsets in the
/// string table.
void MachObjectWriter::
ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
std::vector<MachSymbolData> &LocalSymbolData,
std::vector<MachSymbolData> &ExternalSymbolData,
std::vector<MachSymbolData> &UndefinedSymbolData) {
void MachObjectWriter::ComputeSymbolTable(
MCAssembler &Asm, std::vector<MachSymbolData> &LocalSymbolData,
std::vector<MachSymbolData> &ExternalSymbolData,
std::vector<MachSymbolData> &UndefinedSymbolData) {
// Build section lookup table.
DenseMap<const MCSection*, uint8_t> SectionIndexMap;
unsigned Index = 1;
@@ -542,37 +537,34 @@ ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
SectionIndexMap[&it->getSection()] = Index;
assert(Index <= 256 && "Too many sections!");
// Index 0 is always the empty string.
StringMap<uint64_t> StringIndexMap;
StringTable += '\x00';
// Build the string table.
for (MCSymbolData &SD : Asm.symbols()) {
const MCSymbol &Symbol = SD.getSymbol();
if (!Asm.isSymbolLinkerVisible(Symbol))
continue;
// Build the symbol arrays and the string table, but only for non-local
// symbols.
StringTable.add(Symbol.getName());
}
StringTable.finalize(StringTableBuilder::MachO);
// Build the symbol arrays but only for non-local symbols.
//
// The particular order that we collect the symbols and create the string
// table, then sort the symbols is chosen to match 'as'. Even though it
// doesn't matter for correctness, this is important for letting us diff .o
// files.
// The particular order that we collect and then sort the symbols is chosen to
// match 'as'. Even though it doesn't matter for correctness, this is
// important for letting us diff .o files.
for (MCSymbolData &SD : Asm.symbols()) {
const MCSymbol &Symbol = SD.getSymbol();
// Ignore non-linker visible symbols.
if (!Asm.isSymbolLinkerVisible(SD.getSymbol()))
if (!Asm.isSymbolLinkerVisible(Symbol))
continue;
if (!SD.isExternal() && !Symbol.isUndefined())
continue;
uint64_t &Entry = StringIndexMap[Symbol.getName()];
if (!Entry) {
Entry = StringTable.size();
StringTable += Symbol.getName();
StringTable += '\x00';
}
MachSymbolData MSD;
MSD.SymbolData = &SD;
MSD.StringIndex = Entry;
MSD.StringIndex = StringTable.getOffset(Symbol.getName());
if (Symbol.isUndefined()) {
MSD.SectionIndex = 0;
@@ -592,22 +584,15 @@ ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
const MCSymbol &Symbol = SD.getSymbol();
// Ignore non-linker visible symbols.
if (!Asm.isSymbolLinkerVisible(SD.getSymbol()))
if (!Asm.isSymbolLinkerVisible(Symbol))
continue;
if (SD.isExternal() || Symbol.isUndefined())
continue;
uint64_t &Entry = StringIndexMap[Symbol.getName()];
if (!Entry) {
Entry = StringTable.size();
StringTable += Symbol.getName();
StringTable += '\x00';
}
MachSymbolData MSD;
MSD.SymbolData = &SD;
MSD.StringIndex = Entry;
MSD.StringIndex = StringTable.getOffset(Symbol.getName());
if (Symbol.isAbsolute()) {
MSD.SectionIndex = 0;
@@ -631,10 +616,6 @@ ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
ExternalSymbolData[i].SymbolData->setIndex(Index++);
for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
UndefinedSymbolData[i].SymbolData->setIndex(Index++);
// The string table is padded to a multiple of 4.
while (StringTable.size() % 4)
StringTable += '\x00';
}
void MachObjectWriter::computeSectionAddresses(const MCAssembler &Asm,
@@ -683,7 +664,7 @@ void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
markAbsoluteVariableSymbols(Asm, Layout);
// Compute symbol table information and bind symbol indices.
ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData,
ComputeSymbolTable(Asm, LocalSymbolData, ExternalSymbolData,
UndefinedSymbolData);
}
@@ -922,7 +903,7 @@ void MachObjectWriter::WriteObject(MCAssembler &Asm,
sizeof(MachO::nlist_64) :
sizeof(MachO::nlist));
WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
StringTableOffset, StringTable.size());
StringTableOffset, StringTable.data().size());
WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
FirstExternalSymbol, NumExternalSymbols,
@@ -1028,7 +1009,7 @@ void MachObjectWriter::WriteObject(MCAssembler &Asm,
WriteNlist(UndefinedSymbolData[i], Layout);
// Write the string table.
OS << StringTable.str();
OS << StringTable.data();
}
}