From fb3139ad9e812779e9ad24238b53bbffc6b7d8ba Mon Sep 17 00:00:00 2001 From: Chandler Carruth Date: Thu, 29 Jan 2015 01:23:04 +0000 Subject: [PATCH] [LPM] Clean up the use of TLS in pretty stack trace and disable it entirely when threads are not enabled. This should allow anyone who needs to bootstrap or cope with a host loader without TLS support to limp along without threading support. There is still some bug in the PPC TLS stuff that is not worked around. I'm getting access to a machine to reproduce and debug this further. There is some chance that I'll have to add a terrible workaround for PPC. There is also some problem with iOS, but I have no ability to really evaluate what the issue is there. I'm leaving it to folks maintaining that platform to suggest a path forward -- personally I don't see any useful path forward that supports threading in LLVM but does so without support for *very basic* TLS. Note that we don't need more than some pointers, and we don't need constructors, destructors, or any of the other fanciness which remains widely unimplemented. llvm-svn: 227411 --- llvm/include/llvm/Support/Compiler.h | 35 +++++++++++++++++++++++++++++++++++ llvm/lib/Support/PrettyStackTrace.cpp | 22 ++-------------------- 2 files changed, 37 insertions(+), 20 deletions(-) diff --git a/llvm/include/llvm/Support/Compiler.h b/llvm/include/llvm/Support/Compiler.h index d008fec..1f230c2 100644 --- a/llvm/include/llvm/Support/Compiler.h +++ b/llvm/include/llvm/Support/Compiler.h @@ -373,4 +373,39 @@ #define LLVM_DUMP_METHOD LLVM_ATTRIBUTE_NOINLINE #endif +/// \macro LLVM_THREAD_LOCAL +/// \brief A thread-local storage specifier which can be used with globals, +/// extern globals, and static globals. +/// +/// This is essentially an extremely restricted analog to C++11's thread_local +/// support, and uses that when available. However, it falls back on +/// platform-specific or vendor-provided extensions when necessary. These +/// extensions don't support many of the C++11 thread_local's features. You +/// should only use this for PODs that you can statically initialize to +/// some constant value. In almost all circumstances this is most appropriate +/// for use with a pointer, integer, or small aggregation of pointers and +/// integers. +#if LLVM_ENABLE_THREADS +#if __has_feature(cxx_thread_local) +#define LLVM_THREAD_LOCAL thread_local +#elif defined(_MSC_VER) +// MSVC supports this with a __declspec. +#define LLVM_THREAD_LOCAL __declspec(thread) +#elif defined(__clang__) && defined(__powerpc64__) +// Clang, GCC, and all compatible compilers tend to use __thread. But we need +// to work aronud a bug in the combination of Clang's compilation of +// local-dynamic TLS and the ppc64 linker relocations which we do by forcing to +// global-dynamic (called in most documents "general dynamic"). +// FIXME: Make this conditional on the Clang version once this is fixed in +// top-of-tree. +#define LLVM_THREAD_LOCAL __thread __attribute__((tls_model("global-dynamic"))) +#elif +#define LLVM_THREAD_LOCAL __thread +#endif +#else // !LLVM_ENABLE_THREADS +// If threading is disabled entirely, this compiles to nothing and you get +// a normal global variable. +#define LLVM_THREAD_LOCAL +#endif + #endif diff --git a/llvm/lib/Support/PrettyStackTrace.cpp b/llvm/lib/Support/PrettyStackTrace.cpp index ed576d5..bf7b150 100644 --- a/llvm/lib/Support/PrettyStackTrace.cpp +++ b/llvm/lib/Support/PrettyStackTrace.cpp @@ -16,6 +16,7 @@ #include "llvm-c/Core.h" #include "llvm/ADT/SmallString.h" #include "llvm/Config/config.h" // Get autoconf configuration settings +#include "llvm/Support/Compiler.h" #include "llvm/Support/Signals.h" #include "llvm/Support/Watchdog.h" #include "llvm/Support/raw_ostream.h" @@ -29,26 +30,7 @@ using namespace llvm; // We need a thread local pointer to manage the stack of our stack trace // objects, but we *really* cannot tolerate destructors running and do not want // to pay any overhead of synchronizing. As a consequence, we use a raw -// thread-local variable. Some day, we should be able to use a limited subset -// of C++11's thread_local, but compilers aren't up for it today. -// FIXME: This should be moved to a Compiler.h abstraction. -#ifdef _MSC_VER -// MSVC supports this with a __declspec. -#define LLVM_THREAD_LOCAL __declspec(thread) -#else -// Clang, GCC, and all compatible compilers tend to use __thread. But we need -// to work aronud a bug in the combination of Clang's compilation of -// local-dynamic TLS and the ppc64 linker relocations which we do by forcing to -// global-dynamic (called in most documents "general dynamic"). -// FIXME: Make this conditional on the Clang version once this is fixed in -// top-of-tree. -#if defined(__clang__) && defined(__powerpc64__) -#define LLVM_THREAD_LOCAL __thread __attribute__((tls_model("global-dynamic"))) -#else -#define LLVM_THREAD_LOCAL __thread -#endif -#endif - +// thread-local variable. static LLVM_THREAD_LOCAL const PrettyStackTraceEntry *PrettyStackTraceHead = nullptr; -- 2.7.4