From fe1ffb912d8af97c84363e113646d2cb65a862c9 Mon Sep 17 00:00:00 2001 From: Chandler Carruth Date: Sat, 4 Jun 2016 19:57:55 +0000 Subject: [LPM] Reinstate r271781 which reinstated r271652 to replace the CALL_ONCE_... macro in the legacy pass manager with the new llvm::call_once facility. Nothing changed sicne the last attempt in r271781 which I reverted in r271788. At least one of the failures I saw was spurious, and I want to make sure the other failures are real before I work around them -- they appeared to only effect ppc64le and ppc64be. Original commit message of r271781: ---- [LPM] Reinstate r271652 to replace the CALL_ONCE_... macro in the legacy pass manager with the new llvm::call_once facility. This reverts commit r271657 and re-applies r271652 with a fix to actually work with arguments. In the original version, we just ended up directly calling std::call_once via ADL because of the std::once_flag argument. The llvm::call_once never worked with arguments. Now, llvm::call_once is a variadic template that perfectly forwards everything. As a part of this it had to move to the header and we use a generic functor rather than an explict function pointer. It would be nice to use std::invoke here but we don't have it yet. That means pointer to members won't work here, but that seems a tolerable compromise. I've also tested this by forcing the fallback path, so hopefully it sticks this time. ---- Original commit message of r271652: ---- [LPM] Replace the CALL_ONCE_... macro in the legacy pass manager with the new llvm::call_once facility. This facility matches the standard APIs and when the platform supports it actually directly uses the standard provided functionality. This is both more efficient on some platforms and much more TSan friendly. The only remaining user of the cas_flag and home-rolled atomics is the fallback implementation of call_once. I have a patch that removes them entirely, but it needs a Windows patch to land first. This alone substantially cleans up the macros for the legacy pass manager, and should subsume some of the work Mehdi was doing to clear the path for TSan testing of ThinLTO, a really important step to have reliable upstream testing of ThinLTO in all forms. ---- llvm-svn: 271800 --- llvm/lib/Support/Threading.cpp | 27 --------------------------- 1 file changed, 27 deletions(-) (limited to 'llvm/lib/Support/Threading.cpp') diff --git a/llvm/lib/Support/Threading.cpp b/llvm/lib/Support/Threading.cpp index de2ff6b4fae..e8f5622d0e5 100644 --- a/llvm/lib/Support/Threading.cpp +++ b/llvm/lib/Support/Threading.cpp @@ -116,30 +116,3 @@ void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData, } #endif - -void llvm::call_once(once_flag &flag, void (*fptr)(void)) { -#if LLVM_THREADING_USE_STD_CALL_ONCE - std::call_once(flag, fptr); -#else - // For other platforms we use a generic (if brittle) version based on our - // atomics. - sys::cas_flag old_val = sys::CompareAndSwap(&flag, Wait, Uninitialized); - if (old_val == Uninitialized) { - fptr(); - sys::MemoryFence(); - TsanIgnoreWritesBegin(); - TsanHappensBefore(&flag); - flag = Done; - TsanIgnoreWritesEnd(); - } else { - // Wait until any thread doing the call has finished. - sys::cas_flag tmp = flag; - sys::MemoryFence(); - while (tmp != Done) { - tmp = flag; - sys::MemoryFence(); - } - } - TsanHappensAfter(&flag); -#endif -} -- cgit v1.2.3