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COFF: Use a bit in SymbolBody to track which symbols are written to the symbol table. 

Using a set here caused us to take about 1 second longer to write the symbol
table when linking chrome_child.dll. With this I consistently get better
performance on Windows with the new symbol table.

Before r289280 and with r289183 reverted (median of 5 runs): 17.65s
After this change: 17.33s

On Linux things look even better:

Before: 10.700480444s
After: 5.735681610s

Differential Revision: https://reviews.llvm.org/D27648

llvm-svn: 289408
This commit is contained in:
Peter Collingbourne 2016-12-11 22:15:20 +00:00
parent 831435cb14
commit 99111287fc
2 changed files with 9 additions and 3 deletions
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7
lld/COFF/Symbols.h
View File

@ -80,7 +80,7 @@ protected:
friend SymbolTable; friend SymbolTable;
explicit SymbolBody(Kind K, StringRef N = "") explicit SymbolBody(Kind K, StringRef N = "")
: SymbolKind(K), IsExternal(true), IsCOMDAT(false), : SymbolKind(K), IsExternal(true), IsCOMDAT(false),
IsReplaceable(false), Name(N) {} IsReplaceable(false), WrittenToSymtab(false), Name(N) {}
const unsigned SymbolKind : 8; const unsigned SymbolKind : 8;
unsigned IsExternal : 1; unsigned IsExternal : 1;
@ -91,6 +91,11 @@ protected:
// This bit is used by the \c DefinedBitcode subclass. // This bit is used by the \c DefinedBitcode subclass.
unsigned IsReplaceable : 1; unsigned IsReplaceable : 1;
public:
// This bit is used by Writer::createSymbolAndStringTable().
unsigned WrittenToSymtab : 1;
protected:
StringRef Name; StringRef Name;
}; };

5
lld/COFF/Writer.cpp
View File

@ -533,13 +533,14 @@ void Writer::createSymbolAndStringTable() {
Sec->setStringTableOff(addEntryToStringTable(Name)); Sec->setStringTableOff(addEntryToStringTable(Name));
} }
std::set<SymbolBody *> SeenSymbols;
for (lld::coff::ObjectFile *File : Symtab->ObjectFiles) for (lld::coff::ObjectFile *File : Symtab->ObjectFiles)
for (SymbolBody *B : File->getSymbols()) for (SymbolBody *B : File->getSymbols())
if (auto *D = dyn_cast<Defined>(B)) if (auto *D = dyn_cast<Defined>(B))
if (SeenSymbols.insert(D).second) if (!D->WrittenToSymtab) {
D->WrittenToSymtab = true;
if (Optional<coff_symbol16> Sym = createSymbol(D)) if (Optional<coff_symbol16> Sym = createSymbol(D))
OutputSymtab.push_back(*Sym); OutputSymtab.push_back(*Sym);
}
OutputSection *LastSection = OutputSections.back(); OutputSection *LastSection = OutputSections.back();
// We position the symbol table to be adjacent to the end of the last section. // We position the symbol table to be adjacent to the end of the last section.