From: Orvid King <blah38621@gmail.com>
Date: Wed, 29 Jul 2015 18:36:32 +0000 (-0700)
Subject: Added asm_volatile_memory
X-Git-Tag: v0.53.0~34
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=d6a6bb23e459154202c2d32d50f5ac2d1e887e56;p=folly.git

Added asm_volatile_memory

Summary: This adds `asm_volatile_memory`, which goes along with the same style used by `asm_volatile_pause`.
This also switches the two places in `RWSpinLock.h` that were using inline assembly for this to use the new functions instead.
Closes #260

Reviewed By: @yfeldblum

Differential Revision: D2283541

Pulled By: @sgolemon
---

diff --git a/folly/Portability.h b/folly/Portability.h
index bce4dd1f..252362a5 100644
--- a/folly/Portability.h
+++ b/folly/Portability.h
@@ -339,6 +339,14 @@ inline size_t malloc_usable_size(void* ptr) {
 
 namespace folly {
 
+inline void asm_volatile_memory() {
+#if defined(__clang__) || defined(__GNUC__)
+  asm volatile("" : : : "memory");
+#elif defined(_MSC_VER)
+  ::_ReadWriteBarrier();
+#endif
+}
+
 inline void asm_volatile_pause() {
 #if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
   ::_mm_pause();
diff --git a/folly/RWSpinLock.h b/folly/RWSpinLock.h
index 359343f8..8e191d82 100644
--- a/folly/RWSpinLock.h
+++ b/folly/RWSpinLock.h
@@ -525,13 +525,13 @@ class RWTicketSpinLockT : boost::noncopyable {
  private: // Some x64-specific utilities for atomic access to ticket.
   template<class T> static T load_acquire(T* addr) {
     T t = *addr; // acquire barrier
-    asm volatile("" : : : "memory");
+    asm_volatile_memory();
     return t;
   }
 
   template<class T>
   static void store_release(T* addr, T v) {
-    asm volatile("" : : : "memory");
+    asm_volatile_memory();
     *addr = v; // release barrier
   }