flambda-backend: Backport/install camlatomic.h (#1980)

Author: TheNumbat

runtime4/caml/camlatomic.h

@@ -0,0 +1,85 @@
+/**************************************************************************/
+/*                                                                        */
+/*                                 OCaml                                  */
+/*                                                                        */
+/*      KC Sivaramakrishnan, Indian Institute of Technology, Madras       */
+/*                Stephen Dolan, University of Cambridge                  */
+/*                                                                        */
+/*   Copyright 2018 Indian Institute of Technology, Madras                */
+/*   Copyright 2018 University of Cambridge                               */
+/*                                                                        */
+/*   All rights reserved.  This file is distributed under the terms of    */
+/*   the GNU Lesser General Public License version 2.1, with the          */
+/*   special exception on linking described in the file LICENSE.          */
+/*                                                                        */
+/**************************************************************************/
+#ifndef CAML_ATOMIC_H
+#define CAML_ATOMIC_H
+
+#include "config.h"
+
+/* On platforms supporting C11 atomics, this file just includes <stdatomic.h>.
+
+   On other platforms, this file includes platform-specific stubs for
+   the subset of C11 atomics needed by the OCaml runtime
+ */
+
+#ifdef __cplusplus
+
+extern "C++" {
+#include <atomic>
+#define ATOMIC_UINTNAT_INIT(x) (x)
+typedef std::atomic<uintnat> atomic_uintnat;
+typedef std::atomic<intnat> atomic_intnat;
+using std::memory_order_relaxed;
+using std::memory_order_acquire;
+using std::memory_order_release;
+using std::memory_order_acq_rel;
+using std::memory_order_seq_cst;
+}
+
+#elif defined(HAS_STDATOMIC_H)
+
+#include <stdatomic.h>
+#define ATOMIC_UINTNAT_INIT(x) (x)
+typedef _Atomic uintnat atomic_uintnat;
+typedef _Atomic intnat atomic_intnat;
+
+#elif defined(__GNUC__)
+
+/* Support for versions of gcc which have built-in atomics but do not
+   expose stdatomic.h (e.g. gcc 4.8) */
+typedef enum memory_order {
+  memory_order_relaxed = __ATOMIC_RELAXED,
+  memory_order_acquire = __ATOMIC_ACQUIRE,
+  memory_order_release = __ATOMIC_RELEASE,
+  memory_order_acq_rel = __ATOMIC_ACQ_REL,
+  memory_order_seq_cst = __ATOMIC_SEQ_CST
+} memory_order;
+
+#define ATOMIC_UINTNAT_INIT(x) { (x) }
+typedef struct { uintnat repr; } atomic_uintnat;
+typedef struct { intnat repr; } atomic_intnat;
+
+#define atomic_load_explicit(x, m) __atomic_load_n(&(x)->repr, (m))
+#define atomic_load(x) atomic_load_explicit((x), memory_order_seq_cst)
+#define atomic_store_explicit(x, v, m) __atomic_store_n(&(x)->repr, (v), (m))
+#define atomic_store(x, v) atomic_store_explicit((x), (v), memory_order_seq_cst)
+#define atomic_compare_exchange_strong(x, oldv, newv) \
+  __atomic_compare_exchange_n( \
+    &(x)->repr, \
+    (oldv), (newv), 0, \
+    memory_order_seq_cst, memory_order_seq_cst)
+#define atomic_exchange(x, newv) \
+  __atomic_exchange_n(&(x)->repr, (newv), memory_order_seq_cst)
+#define atomic_fetch_add(x, n) \
+  __atomic_fetch_add(&(x)->repr, (n), memory_order_seq_cst)
+#define atomic_fetch_or(x, n) \
+  __atomic_fetch_or(&(x)->repr, (n), memory_order_seq_cst)
+#define atomic_thread_fence __atomic_thread_fence
+
+#else
+#error "C11 atomics are unavailable on this platform. See camlatomic.h"
+#endif
+
+#endif /* CAML_ATOMIC_H */

runtime4/caml/dune

@@ -47,6 +47,7 @@
     (backtrace_prim.h as caml/backtrace_prim.h)
     (bigarray.h as caml/bigarray.h)
     (callback.h as caml/callback.h)
+    (camlatomic.h as caml/camlatomic.h)
     (codefrag.h as caml/codefrag.h)
     (compact.h as caml/compact.h)
     (compare.h as caml/compare.h)

runtime4/caml/misc.h

@@ -29,6 +29,8 @@
 #include <stdlib.h>
 #include <stdarg.h>
 
+#include "camlatomic.h"
+
 /* Deprecation warnings */
 
 #if defined(__GNUC__) || defined(__clang__)

runtime4/caml/s.h.in

@@ -70,6 +70,8 @@
 
 #undef HAS_ISSETUGID
 
+#undef HAS_STDATOMIC_H
+
 /* 2. For the Unix library. */
 
 #undef HAS_SOCKETS