OTP-8659 Add ethread support for gcc atomics

Support for using gcc's built-in functions for atomic memory access has
been added. This functionallity will be used if available and no other
native atomic implementation in ERTS is available.

1 files changed, 164 insertions, 0 deletions

diff --git a/erts/include/internal/gcc/ethr_atomic.h b/erts/include/internal/gcc/ethr_atomic.h
new file mode 100644
index 0000000000..775030c8d5
--- /dev/null
+++ b/erts/include/internal/gcc/ethr_atomic.h
@@ -0,0 +1,164 @@
+/*
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 2010. All Rights Reserved.
+ *
+ * The contents of this file are subject to the Erlang Public License,
+ * Version 1.1, (the "License"); you may not use this file except in
+ * compliance with the License. You should have received a copy of the
+ * Erlang Public License along with this software. If not, it can be
+ * retrieved online at http://www.erlang.org/.
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * %CopyrightEnd%
+ */
+
+/*
+ * Description: Native atomics ethread support using gcc's builtins
+ * Author: Rickard Green
+ */
+
+#ifndef ETHR_GCC_ATOMIC_H__
+#define ETHR_GCC_ATOMIC_H__
+
+#if !defined(ETHR_HAVE_NATIVE_ATOMICS) && defined(ETHR_HAVE_GCC_ATOMIC_OPS)
+#define ETHR_HAVE_NATIVE_ATOMICS 1
+
+#define ETHR_IMMED_ATOMIC_SET_GET_SAFE__ 0
+/* Enable immediate read/write on platforms where we know it is safe */
+#if defined(__i386__) || defined(__x86_64__) || defined(__sparc__) \
+    || defined(__powerpc__) || defined(__ppc__)
+#  undef ETHR_IMMED_ATOMIC_SET_GET_SAFE__
+#  define ETHR_IMMED_ATOMIC_SET_GET_SAFE__ 1
+#endif
+
+typedef struct {
+    volatile long counter;
+} ethr_native_atomic_t;
+
+
+/*
+ * According to the documentation this is what we want:
+ *   #define ETHR_MEMORY_BARRIER __sync_synchronize()
+ * However, __sync_synchronize() is known to erroneously be
+ * a noop on at least some platforms with some gcc versions.
+ * This has suposedly been fixed in some gcc version, but we
+ * don't know from which version. Therefore, we use the
+ * workaround implemented below on all gcc versions.
+ */
+#define ETHR_MEMORY_BARRIER \
+do { \
+    volatile long x___ = 0; \
+    (void) __sync_val_compare_and_swap(&x___, (long) 0, (long) 1); \
+} while (0)
+
+#if defined(ETHR_TRY_INLINE_FUNCS) || defined(ETHR_AUX_IMPL__)
+
+static ETHR_INLINE void
+ethr_native_atomic_set(ethr_native_atomic_t *var, long value)
+{
+#if ETHR_IMMED_ATOMIC_SET_GET_SAFE__
+    var->counter = value;
+#else
+    /*
+     * Unfortunately no __sync_store() or similar exist in the gcc atomic
+     * op interface. We therefore have to simulate it this way...
+     */
+    long act = 0, exp;
+    do {
+	exp = act;
+	act = __sync_val_compare_and_swap(&var->counter, exp, value);
+    } while (act != exp);
+#endif
+}
+
+#define ethr_native_atomic_init ethr_native_atomic_set
+
+static ETHR_INLINE long
+ethr_native_atomic_read(ethr_native_atomic_t *var)
+{
+#if ETHR_IMMED_ATOMIC_SET_GET_SAFE__
+    return var->counter;
+#else
+    /*
+     * Unfortunately no __sync_fetch() or similar exist in the gcc atomic
+     * op interface. We therefore have to simulate it this way...
+     */
+    return __sync_add_and_fetch(&var->counter, (long) 0);
+#endif
+}
+
+static ETHR_INLINE void
+ethr_native_atomic_add(ethr_native_atomic_t *var, long incr)
+{
+    (void) __sync_add_and_fetch(&var->counter, incr);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_add_return(ethr_native_atomic_t *var, long incr)
+{
+    return __sync_add_and_fetch(&var->counter, incr);
+}
+
+static ETHR_INLINE void
+ethr_native_atomic_inc(ethr_native_atomic_t *var)
+{
+    (void) __sync_add_and_fetch(&var->counter, (long) 1);
+}
+
+static ETHR_INLINE void
+ethr_native_atomic_dec(ethr_native_atomic_t *var)
+{
+    (void) __sync_sub_and_fetch(&var->counter, (long) 1);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_inc_return(ethr_native_atomic_t *var)
+{
+    return __sync_add_and_fetch(&var->counter, (long) 1);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_dec_return(ethr_native_atomic_t *var)
+{
+    return __sync_sub_and_fetch(&var->counter, (long) 1);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_and_retold(ethr_native_atomic_t *var, long mask)
+{
+    return __sync_fetch_and_and(&var->counter, mask);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_or_retold(ethr_native_atomic_t *var, long mask)
+{
+    return (long) __sync_fetch_and_or(&var->counter, mask);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_cmpxchg(ethr_native_atomic_t *var, long new, long old)
+{
+    return __sync_val_compare_and_swap(&var->counter, old, new);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_xchg(ethr_native_atomic_t *var, long new)
+{
+    long exp, act = 0;
+    do {
+	exp = act;
+	act = __sync_val_compare_and_swap(&var->counter, exp, new);
+    } while (act != exp);
+    return act;
+}
+
+#endif
+
+#endif
+
+#endif