Implement our own future and use that for FileArchive::preload().
std::promise and std::future in old version of libstdc++ are buggy.
I think that's the reason why LLD tests were flaky on Ubuntu 13
buildbots until we disabled file preloading.
In this patch, I implemented very simple future and used that in
FileArchive. Compared to std::promise and std::future, it lacks
many features, but should serve our purpose.
http://reviews.llvm.org/D8025
llvm-svn: 231153
diff --git a/lld/lib/Core/Resolver.cpp b/lld/lib/Core/Resolver.cpp
index 7153279..4e5ea01 100644
--- a/lld/lib/Core/Resolver.cpp
+++ b/lld/lib/Core/Resolver.cpp
@@ -31,9 +31,12 @@
bool undefAdded = false;
for (const DefinedAtom *atom : file.defined())
doDefinedAtom(*atom);
- for (const UndefinedAtom *atom : file.undefined())
- if (doUndefinedAtom(*atom))
+ for (const UndefinedAtom *atom : file.undefined()) {
+ if (doUndefinedAtom(*atom)) {
undefAdded = true;
+ maybePreloadArchiveMember(atom->name());
+ }
+ }
for (const SharedLibraryAtom *atom : file.sharedLibrary())
doSharedLibraryAtom(*atom);
for (const AbsoluteAtom *atom : file.absolute())
@@ -230,6 +233,17 @@
doDefinedAtom(*newAtom);
}
+// Instantiate an archive file member if there's a file containing a
+// defined symbol for a given symbol name. Instantiation is done in a
+// different worker thread and has no visible side effect.
+void Resolver::maybePreloadArchiveMember(StringRef sym) {
+ auto it = _archiveMap.find(sym);
+ if (it == _archiveMap.end())
+ return;
+ ArchiveLibraryFile *archive = it->second;
+ archive->preload(_ctx.getTaskGroup(), sym);
+}
+
// Returns true if at least one of N previous files has created an
// undefined symbol.
bool Resolver::undefinesAdded(int begin, int end) {
diff --git a/lld/lib/ReaderWriter/FileArchive.cpp b/lld/lib/ReaderWriter/FileArchive.cpp
index 0acb3a8..247bf30 100644
--- a/lld/lib/ReaderWriter/FileArchive.cpp
+++ b/lld/lib/ReaderWriter/FileArchive.cpp
@@ -10,6 +10,7 @@
#include "lld/Core/ArchiveLibraryFile.h"
#include "lld/Core/LLVM.h"
#include "lld/Core/LinkingContext.h"
+#include "lld/Core/Parallel.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Object/Archive.h"
@@ -17,7 +18,6 @@
#include "llvm/Support/Debug.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/MemoryBuffer.h"
-#include <future>
#include <memory>
#include <mutex>
#include <set>
@@ -63,8 +63,9 @@
std::lock_guard<std::mutex> lock(_mutex);
auto it = _preloaded.find(memberStart);
if (it != _preloaded.end()) {
- std::future<const File *> &future = it->second;
- return future.get();
+ std::unique_ptr<Future<const File *>> &p = it->second;
+ Future<const File *> *future = p.get();
+ return future->get();
}
}
@@ -93,17 +94,13 @@
return;
// Instantiate the member
- auto *promise = new std::promise<const File *>;
- _preloaded[memberStart] = promise->get_future();
- _promises.push_back(std::unique_ptr<std::promise<const File *>>(promise));
+ auto *future = new Future<const File *>();
+ _preloaded[memberStart] = std::unique_ptr<Future<const File *>>(future);
group.spawn([=] {
std::unique_ptr<File> result;
- if (instantiateMember(ci, result)) {
- promise->set_value(nullptr);
- return;
- }
- promise->set_value(result.release());
+ std::error_code ec = instantiateMember(ci, result);
+ future->set(ec ? nullptr : result.release());
});
}
@@ -269,8 +266,7 @@
atom_collection_vector<AbsoluteAtom> _absoluteAtoms;
bool _logLoading;
mutable std::vector<std::unique_ptr<MemoryBuffer>> _memberBuffers;
- mutable std::map<const char *, std::future<const File *>> _preloaded;
- mutable std::vector<std::unique_ptr<std::promise<const File *>>> _promises;
+ mutable std::map<const char *, std::unique_ptr<Future<const File *>>> _preloaded;
mutable std::mutex _mutex;
};