From 59cd80e6c6e36c26a880e86f6cde9f71808b256c Mon Sep 17 00:00:00 2001
From: Chih-hung Hsieh <chh@google.com>
Date: Fri, 5 Dec 2014 17:42:41 -0800
Subject: [PATCH] Add a C11 atomics-based implementation of atomic.h API.

---
 configure.ac                                  | 21 ++++++++++++++
 include/jemalloc/internal/atomic.h            | 28 +++++++++++++++++++
 .../jemalloc/internal/jemalloc_internal.h.in  |  4 +++
 .../internal/jemalloc_internal_defs.h.in      |  3 ++
 4 files changed, 56 insertions(+)

diff --git a/configure.ac b/configure.ac
index 5c51f27f..8b1e55e4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1199,6 +1199,27 @@ elif test "x${force_tls}" = "x1" ; then
   AC_MSG_ERROR([Failed to configure TLS, which is mandatory for correct function])
 fi
 
+dnl ============================================================================
+dnl Check for C11 atomics.
+
+JE_COMPILABLE([C11 atomics], [
+#include <stdint.h>
+#if (__STDC_VERSION__ >= 201112L) && !defined(__STDC_NO_ATOMICS__)
+#include <stdatomic.h>
+#else
+#error Atomics not available
+#endif
+], [
+    uint64_t *p = (uint64_t *)0;
+    uint64_t x = 1;
+    volatile atomic_uint_least64_t *a = (volatile atomic_uint_least64_t *)p;
+    uint64_t r = atomic_fetch_add(a, x) + x;
+    return (r == 0);
+], [je_cv_c11atomics])
+if test "x${je_cv_c11atomics}" = "xyes" ; then
+  AC_DEFINE([JEMALLOC_C11ATOMICS])
+fi
+
 dnl ============================================================================
 dnl Check for atomic(9) operations as provided on FreeBSD.
 
diff --git a/include/jemalloc/internal/atomic.h b/include/jemalloc/internal/atomic.h
index 8b743b88..23ac93ff 100644
--- a/include/jemalloc/internal/atomic.h
+++ b/include/jemalloc/internal/atomic.h
@@ -72,6 +72,20 @@ atomic_sub_uint64(uint64_t *p, uint64_t x)
 
 	return (InterlockedExchangeAdd64(p, -((int64_t)x)) - x);
 }
+#  elif (defined(JEMALLOC_C11ATOMICS))
+JEMALLOC_INLINE uint64_t
+atomic_add_uint64(uint64_t *p, uint64_t x)
+{
+	volatile atomic_uint_least64_t *a = (volatile atomic_uint_least64_t *)p;
+	return (atomic_fetch_add(a, x) + x);
+}
+
+JEMALLOC_INLINE uint64_t
+atomic_sub_uint64(uint64_t *p, uint64_t x)
+{
+	volatile atomic_uint_least64_t *a = (volatile atomic_uint_least64_t *)p;
+	return (atomic_fetch_sub(a, x) - x);
+}
 #  elif (defined(JEMALLOC_OSATOMIC))
 JEMALLOC_INLINE uint64_t
 atomic_add_uint64(uint64_t *p, uint64_t x)
@@ -187,6 +201,20 @@ atomic_sub_uint32(uint32_t *p, uint32_t x)
 
 	return (InterlockedExchangeAdd(p, -((int32_t)x)) - x);
 }
+#  elif (defined(JEMALLOC_C11ATOMICS))
+JEMALLOC_INLINE uint32_t
+atomic_add_uint32(uint32_t *p, uint32_t x)
+{
+	volatile atomic_uint_least32_t *a = (volatile atomic_uint_least32_t *)p;
+	return (atomic_fetch_add(a, x) + x);
+}
+
+JEMALLOC_INLINE uint32_t
+atomic_sub_uint32(uint32_t *p, uint32_t x)
+{
+	volatile atomic_uint_least32_t *a = (volatile atomic_uint_least32_t *)p;
+	return (atomic_fetch_sub(a, x) - x);
+}
 #elif (defined(JEMALLOC_OSATOMIC))
 JEMALLOC_INLINE uint32_t
 atomic_add_uint32(uint32_t *p, uint32_t x)
diff --git a/include/jemalloc/internal/jemalloc_internal.h.in b/include/jemalloc/internal/jemalloc_internal.h.in
index 6f13093f..bf10617e 100644
--- a/include/jemalloc/internal/jemalloc_internal.h.in
+++ b/include/jemalloc/internal/jemalloc_internal.h.in
@@ -127,6 +127,10 @@ static const bool config_ivsalloc =
 #endif
     ;
 
+#ifdef JEMALLOC_C11ATOMICS
+#include <stdatomic.h>
+#endif
+
 #ifdef JEMALLOC_ATOMIC9
 #include <machine/atomic.h>
 #endif
diff --git a/include/jemalloc/internal/jemalloc_internal_defs.h.in b/include/jemalloc/internal/jemalloc_internal_defs.h.in
index dccbb1ed..2923e83f 100644
--- a/include/jemalloc/internal/jemalloc_internal_defs.h.in
+++ b/include/jemalloc/internal/jemalloc_internal_defs.h.in
@@ -22,6 +22,9 @@
  */
 #undef CPU_SPINWAIT
 
+/* Defined if C11 atomics are available. */
+#undef JEMALLOC_C11ATOMICS
+
 /* Defined if the equivalent of FreeBSD's atomic(9) functions are available. */
 #undef JEMALLOC_ATOMIC9