* signal.c (rb_atomic_t): GCC (of at least recent versions)

  has  ubiquitos  support  for  atomic  operations.   On  that
  compiler a C  program can isse a memory  barrier using these
  dedicated  instructions.  According to  the GCC  manual they
  cargo culted  this feature form  the Itanium ABI  so chances
  are that  other compilers  could also support  this feature.
  But so far GCC is the  only compiler that I know to have it.
  Also note that this works on non-Itanium machines.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29589 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 22 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index a0cf409a37..bc193350e4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+Mon Oct 25 16:38:07 2010  URABE Shyouhei  <shyouhei@ruby-lang.org>
+
+	* signal.c  (rb_atomic_t): GCC (of  at least  recent versions)
+	  has  ubiquitos  support  for  atomic  operations.   On  that
+	  compiler a C  program can isse a memory  barrier using these
+	  dedicated  instructions.  According to  the GCC  manual they
+	  cargo culted  this feature form  the Itanium ABI  so chances
+	  are that  other compilers  could also support  this feature.
+	  But so far GCC is the  only compiler that I know to have it.
+	  Also note that this works on non-Itanium machines.
+
 Mon Oct 25 06:21:35 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* vsnprintf.c (BSD_vfprintf): prec digits fractal part should be
diff --git a/signal.c b/signal.c
index 4906e9162a..e2d9d84e4d 100644
--- a/signal.c
+++ b/signal.c
@@ -25,6 +25,17 @@ typedef LONG rb_atomic_t;
 # define ATOMIC_INC(var) InterlockedIncrement(&(var))
 # define ATOMIC_DEC(var) InterlockedDecrement(&(var))
 
+#elsif __GNUC__ >= 4
+/* @shyouhei hack to support atomic operations in case of gcc. Gcc
+ * has its own pseudo-insns to support them.  See info, or
+ * http://gcc.gnu.org/onlinedocs/gcc/Atomic-Builtins.html */
+
+typedef unsigned char rb_atomic_t; /* Anything OK */
+# define ATOMIC_TEST(var) __sync_lock_test_and_set(&(var), 0)
+# define ATOMIC_SET(var, val)  __sync_lock_test_and_set(&(var), (val))
+# define ATOMIC_INC(var) __sync_fetch_and_add(&(var), 1)
+# define ATOMIC_DEC(var) __sync_fetch_and_sub(&(var), 1)
+
 #else
 typedef int rb_atomic_t;