[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, 101 insertions, 0 deletions

diff --git a/llvm/lib/Support/Windows/Threading.inc b/llvm/lib/Support/Windows/Threading.inc
new file mode 100644
index 00000000000..30086544ab2
--- /dev/null
+++ b/llvm/lib/Support/Windows/Threading.inc
@@ -0,0 +1,101 @@
+//===- Windows/Threading.inc - Win32 Threading Implementation - -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides the Win32 specific implementation of Threading functions.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/Twine.h"
+
+#include "Windows/WindowsSupport.h"
+#include <process.h>
+
+// Windows will at times define MemoryFence.
+#ifdef MemoryFence
+#undef MemoryFence
+#endif
+
+namespace {
+  struct ThreadInfo {
+    void(*func)(void*);
+    void *param;
+  };
+}
+
+static unsigned __stdcall ThreadCallback(void *param) {
+  struct ThreadInfo *info = reinterpret_cast<struct ThreadInfo *>(param);
+  info->func(info->param);
+
+  return 0;
+}
+
+void llvm::llvm_execute_on_thread(void(*Fn)(void*), void *UserData,
+  unsigned RequestedStackSize) {
+  struct ThreadInfo param = { Fn, UserData };
+
+  HANDLE hThread = (HANDLE)::_beginthreadex(NULL,
+    RequestedStackSize, ThreadCallback,
+    &param, 0, NULL);
+
+  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);
+  }
+}
+
+uint64_t llvm::get_threadid() {
+  return uint64_t(::GetCurrentThreadId());
+}
+
+void llvm::set_thread_name(const Twine &Name) {
+#if defined(_MSC_VER)
+  // Make sure the input is null terminated.
+  SmallString<64> Storage;
+  StringRef NameStr = Name.toNullTerminatedStringRef(Storage);
+  constexpr DWORD MS_VC_EXCEPTION = 0x406D1388;
+
+#pragma pack(push, 8)
+  struct THREADNAME_INFO {
+    DWORD dwType;     // Must be 0x1000.
+    LPCSTR szName;    // Pointer to thread name
+    DWORD dwThreadId; // Thread ID (-1 == current thread)
+    DWORD dwFlags;    // Reserved.  Do not use.
+  };
+#pragma pack(pop)
+
+  THREADNAME_INFO info;
+  info.dwType = 0x1000;
+  info.szName = NameStr.data();
+  info.dwThreadId = ::GetCurrentThreadId();
+  info.dwFlags = 0;
+
+  __try {
+    ::RaiseException(MS_VC_EXCEPTION, 0, sizeof(info) / sizeof(ULONG_PTR),
+      (ULONG_PTR *)&info);
+  }
+  __except (EXCEPTION_EXECUTE_HANDLER) {
+  }
+#endif
+}
+
+void llvm::get_thread_name(SmallVectorImpl<char> &Name) {
+  // "Name" is not an inherent property of a thread on Windows.  In fact, when
+  // you "set" the name, you are only firing a one-time message to a debugger
+  // which it interprets as a program setting its threads' name.  We may be
+  // able to get fancy by creating a TLS entry when someone calls
+  // set_thread_name so that subsequent calls to get_thread_name return this
+  // value.
+  Name.clear();
+}