Imported Upstream version 5.18.0.179

Former-commit-id: 67aa10e65b237e1c4537630979ee99ebe1374215

external/llvm/lib/Support/Atomic.cpp

@@ -0,0 +1,60 @@
+//===-- Atomic.cpp - Atomic Operations --------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements atomic operations.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Atomic.h"
+#include "llvm/Config/llvm-config.h"
+
+using namespace llvm;
+
+#if defined(_MSC_VER)
+#include <intrin.h>
+
+// We must include windows.h after intrin.h.
+#include <windows.h>
+#undef MemoryFence
+#endif
+
+#if defined(__GNUC__) || (defined(__IBMCPP__) && __IBMCPP__ >= 1210)
+#define GNU_ATOMICS
+#endif
+
+void sys::MemoryFence() {
+#if LLVM_HAS_ATOMICS == 0
+  return;
+#else
+#  if defined(GNU_ATOMICS)
+  __sync_synchronize();
+#  elif defined(_MSC_VER)
+  MemoryBarrier();
+#  else
+# error No memory fence implementation for your platform!
+#  endif
+#endif
+}
+
+sys::cas_flag sys::CompareAndSwap(volatile sys::cas_flag* ptr,
+                                  sys::cas_flag new_value,
+                                  sys::cas_flag old_value) {
+#if LLVM_HAS_ATOMICS == 0
+  sys::cas_flag result = *ptr;
+  if (result == old_value)
+    *ptr = new_value;
+  return result;
+#elif defined(GNU_ATOMICS)
+  return __sync_val_compare_and_swap(ptr, old_value, new_value);
+#elif defined(_MSC_VER)
+  return InterlockedCompareExchange(ptr, new_value, old_value);
+#else
+#  error No compare-and-swap implementation for your platform!
+#endif
+}