COFF: Make ArchiveFile::getMember lock-free.
The previous code was not even safe with MSVC 2013 because the compiler
doesn't guarantee that static variables (in this case, a mutex) are
initialized in a thread-safe manner.
llvm-svn: 241481
diff --git a/lld/COFF/InputFiles.cpp b/lld/COFF/InputFiles.cpp
index 6bdfd4f..5d44c31 100644
--- a/lld/COFF/InputFiles.cpp
+++ b/lld/COFF/InputFiles.cpp
@@ -73,13 +73,18 @@
if (B->getName() != "__NULL_IMPORT_DESCRIPTOR")
LazySymbols.push_back(B);
}
+
+ // Seen is a map from member files to boolean values. Initially
+ // all members are mapped to false, which indicates all these files
+ // are not read yet.
+ for (const Archive::Child &Child : File->children())
+ Seen[Child.getBuffer().data()].clear();
return std::error_code();
}
// Returns a buffer pointing to a member file containing a given symbol.
// This function is thread-safe.
ErrorOr<MemoryBufferRef> ArchiveFile::getMember(const Archive::Symbol *Sym) {
- static std::mutex Mu;
auto ItOrErr = Sym->getMember();
if (auto EC = ItOrErr.getError())
return EC;
@@ -87,10 +92,7 @@
// Return an empty buffer if we have already returned the same buffer.
const char *StartAddr = It->getBuffer().data();
- Mu.lock();
- auto Pair = Seen.insert(StartAddr);
- Mu.unlock();
- if (!Pair.second)
+ if (Seen[StartAddr].test_and_set())
return MemoryBufferRef();
return It->getMemoryBufferRef();
}