[Support] Provide access to current thread name/thread id.

Applications often need the current thread id when making
system calls, and some operating systems provide the notion
of a thread name, which can be useful in enabling better
diagnostics when debugging or logging.

This patch adds an accessor for the thread id, and "best effort"
getters and setters for the thread name.  Since this is
non critical functionality, no error is returned to indicate
that a platform doesn't support thread names.

Differential Revision: https://reviews.llvm.org/D30526

llvm-svn: 296887

1 files changed, 29 insertions, 84 deletions

diff --git a/llvm/lib/Support/Threading.cpp b/llvm/lib/Support/Threading.cpp
index 760f9e2c388..a9ecf9b10bf 100644
--- a/llvm/lib/Support/Threading.cpp
+++ b/llvm/lib/Support/Threading.cpp
@@ -14,14 +14,21 @@
 
 #include "llvm/Support/Threading.h"
 #include "llvm/Config/config.h"
-#include "llvm/Support/Atomic.h"
 #include "llvm/Support/Host.h"
-#include "llvm/Support/Mutex.h"
 #include "llvm/Support/thread.h"
+
 #include <cassert>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
 
 using namespace llvm;
 
+//===----------------------------------------------------------------------===//
+//=== WARNING: Implementation here must contain only TRULY operating system
+//===          independent code.
+//===----------------------------------------------------------------------===//
+
 bool llvm::llvm_is_multithreaded() {
 #if LLVM_ENABLE_THREADS != 0
   return true;
@@ -30,100 +37,38 @@ bool llvm::llvm_is_multithreaded() {
 #endif
 }
 
-#if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
-#include <pthread.h>
-
-struct ThreadInfo {
-  void (*UserFn)(void *);
-  void *UserData;
-};
-static void *ExecuteOnThread_Dispatch(void *Arg) {
-  ThreadInfo *TI = reinterpret_cast<ThreadInfo*>(Arg);
-  TI->UserFn(TI->UserData);
-  return nullptr;
-}
-
-void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
+#if LLVM_ENABLE_THREADS == 0 ||                                                \
+    (!defined(LLVM_ON_WIN32) && !defined(HAVE_PTHREAD_H))
+// Support for non-Win32, non-pthread implementation.
+void llvm::llvm_execute_on_thread(void (*Fn)(void *), void *UserData,
                                   unsigned RequestedStackSize) {
-  ThreadInfo Info = { Fn, UserData };
-  pthread_attr_t Attr;
-  pthread_t Thread;
-
-  // Construct the attributes object.
-  if (::pthread_attr_init(&Attr) != 0)
-    return;
-
-  // Set the requested stack size, if given.
-  if (RequestedStackSize != 0) {
-    if (::pthread_attr_setstacksize(&Attr, RequestedStackSize) != 0)
-      goto error;
-  }
-
-  // Construct and execute the thread.
-  if (::pthread_create(&Thread, &Attr, ExecuteOnThread_Dispatch, &Info) != 0)
-    goto error;
-
-  // Wait for the thread and clean up.
-  ::pthread_join(Thread, nullptr);
-
- error:
-  ::pthread_attr_destroy(&Attr);
+  (void)RequestedStackSize;
+  Fn(UserData);
 }
-#elif LLVM_ENABLE_THREADS!=0 && defined(LLVM_ON_WIN32)
-#include "Windows/WindowsSupport.h"
-#include <process.h>
-
-// Windows will at times define MemoryFence.
-#ifdef MemoryFence
-#undef MemoryFence
-#endif
 
-struct ThreadInfo {
-  void (*func)(void*);
-  void *param;
-};
+unsigned llvm::heavyweight_hardware_concurrency() { return 1; }
 
-static unsigned __stdcall ThreadCallback(void *param) {
-  struct ThreadInfo *info = reinterpret_cast<struct ThreadInfo *>(param);
-  info->func(info->param);
+uint64_t llvm::get_threadid_np() { return 0; }
 
-  return 0;
-}
-
-void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
-                                  unsigned RequestedStackSize) {
-  struct ThreadInfo param = { Fn, UserData };
+void llvm::set_thread_name(const Twine &Name) {}
 
-  HANDLE hThread = (HANDLE)::_beginthreadex(NULL,
-                                            RequestedStackSize, ThreadCallback,
-                                            &param, 0, NULL);
+void llvm::get_thread_name(SmallVectorImpl<char> &Name) { Name.clear(); }
 
-  if (hThread) {
-    // We actually don't care whether the wait succeeds or fails, in
-    // the same way we don't care whether the pthread_join call succeeds
-    // or fails.  There's not much we could do if this were to fail. But
-    // on success, this call will wait until the thread finishes executing
-    // before returning.
-    (void)::WaitForSingleObject(hThread, INFINITE);
-    ::CloseHandle(hThread);
-  }
-}
 #else
-// Support for non-Win32, non-pthread implementation.
-void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
-                                  unsigned RequestedStackSize) {
-  (void) RequestedStackSize;
-  Fn(UserData);
-}
-
-#endif
 
 unsigned llvm::heavyweight_hardware_concurrency() {
-#if !LLVM_ENABLE_THREADS
-  return 1;
-#endif
   int NumPhysical = sys::getHostNumPhysicalCores();
   if (NumPhysical == -1)
     return thread::hardware_concurrency();
   return NumPhysical;
 }
+
+// Include the platform-specific parts of this class.
+#ifdef LLVM_ON_UNIX
+#include "Unix/Threading.inc"
+#endif
+#ifdef LLVM_ON_WIN32
+#include "Windows/Threading.inc"
+#endif
+
+#endif