Add internal support for the new __atomic gcc builtins

Signed-off-by: Angus Salkeld <asalkeld@redhat.com>

configure.ac

@@ -365,6 +365,30 @@ if test "x$gcc_has_builtin_sync_operations" = xyes; then
 			   [have builtin sync operations])
 fi
 
+# __atomic_XXX
+AC_MSG_CHECKING([whether GCC supports builtin atomic intrinsics])
+if test -z "$gcc_has_builtin_atomic_operations"; then
+	gcc_has_builtin_atomic_operations=no
+	if test x"$GCC" = xyes && test x$have_mingw != xyes; then
+		AC_TRY_LINK([],
+			    [int i;
+			     __atomic_load_n(&i, __ATOMIC_ACQUIRE);
+			     __atomic_exchange_n(&i, 0, __ATOMIC_RELEASE);
+			     ],
+			     [gcc_has_builtin_atomic_operations=yes],
+			     [gcc_has_builtin_atomic_operations=no])
+	fi
+fi
+AC_MSG_RESULT($gcc_has_builtin_atomic_operations)
+AM_CONDITIONAL(HAVE_GCC_BUILTINS_FOR_ATOMIC_OPERATIONS,
+	       [test "x$gcc_has_builtin_atomic_operations" = xyes])
+
+if test "x$gcc_has_builtin_atomic_operations" = xyes; then
+	AC_DEFINE_UNQUOTED(HAVE_GCC_BUILTINS_FOR_ATOMIC_OPERATIONS, 1,
+			   [have builtin atomic operations])
+fi
+
+
 AC_MSG_CHECKING([whether atomics need memory barrier])
 if test -n "$ac_cv_atomic_need_memory_barrier"; then
 	memory_barrier_needed=$ac_cv_atomic_need_memory_barrier
@@ -389,7 +413,7 @@ fi
 
 LINT_FLAGS="-syntax -weak -unrecog +posixlib +ignoresigns -fcnuse \
 	-badflag -D__gnuc_va_list=va_list -D__attribute\(x\)= \
-	-warnposix +matchanyintegral"
+	-warnposix +matchanyintegral -sysunrecog"
 
 # local options
 AC_ARG_ENABLE([ansi],

lib/atomic_int.h

@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2013 Red Hat, Inc.
+ *
+ * Author: Angus Salkeld <asalkeld@redhat.com>
+ *
+ * libqb is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * libqb is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with libqb.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef QB_ATOMIC_INT_H_DEFINED
+#define QB_ATOMIC_INT_H_DEFINED
+
+/*
+ * This adds some extra atomic functionality, building on the
+ * gcc atomic builtins.
+ */
+
+#include "os_base.h"
+#include <qb/qbdefs.h>
+#include <qb/qbatomic.h>
+
+/* This is a thin wrapper around the new gcc atomics.
+ */
+enum qb_atomic_model {
+	QB_ATOMIC_RELAXED,
+	QB_ATOMIC_CONSUME,
+	QB_ATOMIC_ACQUIRE,
+	QB_ATOMIC_RELEASE,
+	QB_ATOMIC_ACQ_REL,
+	QB_ATOMIC_SEQ_CST,
+};
+
+#ifdef HAVE_GCC_BUILTINS_FOR_ATOMIC_OPERATIONS
+static inline int
+qb_model_map(enum qb_atomic_model model)
+{
+	switch (model) {
+	case QB_ATOMIC_ACQUIRE:
+		return __ATOMIC_ACQUIRE;
+	case QB_ATOMIC_RELEASE:
+		return __ATOMIC_RELEASE;
+	case QB_ATOMIC_RELAXED:
+		return __ATOMIC_RELAXED;
+	case QB_ATOMIC_CONSUME:
+		return __ATOMIC_CONSUME;
+	case QB_ATOMIC_ACQ_REL:
+		return __ATOMIC_ACQ_REL;
+	case QB_ATOMIC_SEQ_CST:
+	default:
+		return __ATOMIC_SEQ_CST;
+	}
+}
+#endif /* HAVE_GCC_BUILTINS_FOR_ATOMIC_OPERATIONS */
+
+#ifdef QB_ATOMIC_OP_MEMORY_BARRIER_NEEDED
+
+#ifdef HAVE_GCC_BUILTINS_FOR_SYNC_OPERATIONS
+#define QB_ATOMIC_MEMORY_BARRIER __sync_synchronize ()
+#else
+#ifndef HAVE_GCC_BUILTINS_FOR_ATOMIC_OPERATIONS
+#warning you need memory barriers but do not have an implementation.
+#endif /* HAVE_GCC_BUILTINS_FOR_ATOMIC_OPERATIONS */
+#endif /* HAVE_GCC_BUILTINS_FOR_SYNC_OPERATIONS */
+
+#ifndef QB_ATOMIC_MEMORY_BARRIER
+#define QB_ATOMIC_MEMORY_BARRIER
+#endif /* QB_ATOMIC_MEMORY_BARRIER */
+
+#endif /* QB_ATOMIC_OP_MEMORY_BARRIER_NEEDED */
+
+/**
+ * Reads the value of the integer pointed to by atomic.
+ * Also acts as a memory barrier.
+ *
+ * @param atomic a pointer to an integer
+ * @param model the memory model to use.
+ *
+ * @return the value of atomic
+ */
+static inline int32_t
+qb_atomic_int_get_ex(volatile int32_t QB_GNUC_MAY_ALIAS * atomic,
+		     enum qb_atomic_model model)
+{
+#ifdef HAVE_GCC_BUILTINS_FOR_ATOMIC_OPERATIONS
+	return __atomic_load_n(atomic, qb_model_map(model));
+#else
+	return qb_atomic_int_get(atomic);
+#endif
+}
+
+
+/**
+ * Sets the value of the integer pointed to by atomic.
+ * Also acts as a memory barrier.
+ *
+ * @param atomic a pointer to an integer
+ * @param newval the new value
+ * @param model the memory model to use.
+ */
+static inline void
+qb_atomic_int_set_ex(volatile int32_t QB_GNUC_MAY_ALIAS * atomic,
+		     int32_t newval,
+		     enum qb_atomic_model model)
+{
+#ifdef HAVE_GCC_BUILTINS_FOR_ATOMIC_OPERATIONS
+	__atomic_store_n(atomic, newval, qb_model_map(model));
+#else
+/*
+ * If the model is acquire we need the barrier afterwards,
+ * and if its cst we need it before and after.
+ * Note: qb_atomic_int_set already has a memory barrier after
+ * the set.
+ */
+	if (model != QB_ATOMIC_RELAXED && model != QB_ATOMIC_CONSUME) {
+		QB_ATOMIC_MEMORY_BARRIER;
+	}
+	qb_atomic_int_set(atomic, newval);
+#endif
+}
+
+#endif /* QB_ATOMIC_INT_H_DEFINED */