[beast: 14/16] SFI: provide BSE_CACHE_LINE_ALIGNMENT and BSE_?FENCE directives

[Tim Janik <timj src gnome org>]

commit 44da0ebf1b8d133b24051eac6b7be0f99af74307
Author: Tim Janik <timj gnu org>
Date:   Mon Sep 18 23:11:20 2017 +0200

    SFI: provide BSE_CACHE_LINE_ALIGNMENT and BSE_?FENCE directives
    
    Signed-off-by: Tim Janik <timj gnu org>

 sfi/platform.hh |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)
---
diff --git a/sfi/platform.hh b/sfi/platform.hh
index 4910d50..e2087ff 100644
--- a/sfi/platform.hh
+++ b/sfi/platform.hh
@@ -68,6 +68,21 @@ StringVector       pretty_backtrace_symbols (void **pointers, const int nptrs);
       const String __s_ = ::Bse::pretty_backtrace (__p_, ::Bse::backtrace_pointers (__p_, sizeof (__p_) / 
sizeof (__p_[0])), \
                                                    __FILE__, __LINE__, __func__); __s_; })
 
+// == Memory Barriers ==
+#define  BSE_CACHE_LINE_ALIGNMENT       64      // generally enough on x86, see getconf 
LEVEL1_DCACHE_LINESIZE
+#if defined __x86_64__ || defined __amd64__
+#define  BSE_MFENCE __sync_synchronize()
+#define  BSE_SFENCE __asm__ __volatile__ ("sfence" ::: "memory")
+#define  BSE_LFENCE __asm__ __volatile__ ("lfence" ::: "memory")
+#else // !x86/64
+#define  BSE_SFENCE __sync_synchronize() ///< Store Fence - prevent processor (and compiler) from reordering 
stores (write barrier).
+#define  BSE_LFENCE __sync_synchronize() ///< Load Fence  - prevent processor (and compiler) from reordering 
loads (read barrier).
+/// Memory Fence - prevent processor (and compiler) from reordering loads/stores (read/write barrier), see 
also std::atomic_thread_fence().
+#define  BSE_MFENCE __sync_synchronize()
+#endif
+/// Compiler Fence, prevent compiler from reordering non-volatile loads/stores, see also 
std::atomic_signal_fence().
+#define  BSE_CFENCE __asm__ __volatile__ ("" ::: "memory")
+
 // == Implementation Details ==
 #if (defined __i386__ || defined __x86_64__)
 inline void breakpoint() { __asm__ __volatile__ ("int $03"); }