lib: use stdatomic.h for memory barriers

C11 gives us APIs for fencing logic.  Use that instead of a
a long, per-architecture, hand curated list of definitions.

lib/Makefile.am

@@ -20,7 +20,6 @@ libutil_la_SOURCES = \
 	util/elfparser.h \
 	util/stackstash.c \
 	util/stackstash.h \
-	util/util.h \
 	$(NULL)
 libutil_la_CFLAGS = \
 	-I$(srcdir)/util \

lib/sp-callgraph-view.c

@@ -41,8 +41,6 @@
 #include "sp-callgraph-view.h"
 #include "sp-cell-renderer-percent.h"
 
-#include "util.h"
-
 typedef struct
 {
   SpCallgraphProfile  *profile;

lib/sp-perf-counter.c

@@ -42,6 +42,7 @@
 #include <errno.h>
 #include <gio/gio.h>
 #include <gio/gunixfdlist.h>
+#include <stdatomic.h>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
@@ -54,8 +55,6 @@
 
 #include "sp-perf-counter.h"
 
-#include "util.h"
-
 /*
  * Number of pages to map for the ring buffer.  We map one additional buffer
  * at the beginning for header information to communicate with perf.
@@ -227,7 +226,7 @@ sp_perf_counter_flush (SpPerfCounter     *self,
   tail = info->tail;
   head = info->map->data_head;
 
-  read_barrier ();
+  atomic_thread_fence (memory_order_acquire);
 
   if (head < tail)
     tail = head;

lib/util/binfile.c

@@ -37,7 +37,6 @@
 
 #include "binfile.h"
 #include "elfparser.h"
-#include "util.h"
 
 struct bin_file_t
 {

lib/util/util.h

@@ -1,44 +0,0 @@
-#ifndef SP_UTIL_H
-#define SP_UTIL_H
-
-#ifdef __i386__
-#define read_barrier()           asm volatile("lock; addl $0,0(%%esp)" ::: "memory")
-#endif
-
-#ifdef __x86_64__
-#define read_barrier()           asm volatile("lfence" ::: "memory")
-#endif
-
-#ifdef __powerpc__
-#define read_barrier()           asm volatile ("sync" ::: "memory")
-#endif
-
-#ifdef __s390__
-#define read_barrier()           asm volatile("bcr 15,0" ::: "memory")
-#endif
-
-#ifdef __sh__
-#if defined(__SH4A__) || defined(__SH5__)
-# define read_barrier()          asm volatile("synco" ::: "memory")
-#else
-# define read_barrier()          asm volatile("" ::: "memory")
-#endif
-#endif
-
-#ifdef __hppa__
-#define read_barrier()           asm volatile("" ::: "memory")
-#endif
-
-#ifdef __arm__
-#define read_barrier()           asm volatile("dsb" ::: "memory")
-#endif
-
-/*
- * Fallback to a full memory barrier if the architecture is not yet
- * supported with a lighter read barrier.
- */
-#ifndef read_barrier
-#define read_barrier()           __sync_synchronize()
-#endif
-
-#endif /* SP_UTIL_H */