[clangd] Don't try pthread, just use thread_local. Reverts r323949.

The pthread solution here breaks standalone builds, which don't have the
relevant cmake magic for feature-detection.

The original reason for trying pthread was fear of libgcc without
support for thread_local (e.g. on the clang-x86_64-linux-selfhost-modules bot).
However the earliest supported GCC is 4.8, and this has __cxa_thread_atexit.

This will probably break that bot, it's not running a supported GCC and needs
to be upgraded. I'll try to find out how to do this.

llvm-svn: 324351

diff --git a/clang-tools-extra/clangd/Context.cpp b/clang-tools-extra/clangd/Context.cpp
index 23006778f5501d225a4ccc73d47e53d67097ff6b..7ecaced52c4823385080e156cac876734d621c33 100644 (file)
--- a/clang-tools-extra/clangd/Context.cpp
+++ b/clang-tools-extra/clangd/Context.cpp
@@ -8,49 +8,8 @@
 //===---------------------------------------------------------------------===//
 
 #include "Context.h"
-#include "llvm/Config/config.h"
 #include <cassert>
 
-// The thread-local Context is scoped in a function to avoid init-order issues.
-// It's created by currentContext() when first needed.
-
-#ifdef HAVE_PTHREAD_GETSPECIFIC
-// We'd love to use thread_local everywhere.
-// It requires support from the runtime: __cxa_thread_atexit.
-// Rather than detect this, we use the pthread API where available.
-#include <pthread.h>
-#include <cstring>
-static clang::clangd::Context &currentContext() {
-  using clang::clangd::Context;
-  static pthread_key_t CtxKey;
-
-  // Once (across threads), set up pthread TLS for Context, and its destructor.
-  static int Dummy = [] { // Create key only once, for all threads.
-    if (auto Err = pthread_key_create(&CtxKey, /*destructor=*/+[](void *Ctx) {
-          delete reinterpret_cast<Context *>(Ctx);
-        }))
-      llvm_unreachable(strerror(Err));
-    return 0;
-  }();
-  (void)Dummy;
-
-  // Now grab the current context from TLS, and create it if it doesn't exist.
-  void *Ctx = pthread_getspecific(CtxKey);
-  if (!Ctx) {
-    Ctx = new Context();
-    if (auto Err = pthread_setspecific(CtxKey, Ctx))
-      llvm_unreachable(strerror(Err));
-  }
-  return *reinterpret_cast<Context *>(Ctx);
-}
-#else
-// Only supported platform without pthread is windows, and thread_local works.
-static clang::clangd::Context &currentContext() {
-  static thread_local auto C = clang::clangd::Context::empty();
-  return C;
-}
-#endif
-
 namespace clang {
 namespace clangd {
 
@@ -61,6 +20,11 @@ Context::Context(std::shared_ptr<const Data> DataPtr)
 
 Context Context::clone() const { return Context(DataPtr); }
 
+static Context &currentContext() {
+  static thread_local auto C = Context::empty();
+  return C;
+}
+
 const Context &Context::current() { return currentContext(); }
 
 Context Context::swapCurrent(Context Replacement) {