libcilkrts/runtime/config/x86/os-fence.h

   1 /* os.h                  -*-C++-*-
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  49
  50 /* gcc before 4.4 does not implement __sync_synchronize properly */
  51 #if (__ICC >= 1110 && !(__MIC__ || __MIC2__))                      \
  52     || (!defined __ICC && __GNUC__ * 10 + __GNUC_MINOR__ > 43)
  53 #   define HAVE_SYNC_INTRINSICS 1
  54 #endif
  55
  56
  57 /*
  58  * void __cilkrts_fence(void)
  59  *
  60  * Executes an MFENCE instruction to serialize all load and store instructions
  61  * that were issued prior the MFENCE instruction. This serializing operation
  62  * guarantees that every load and store instruction that precedes the MFENCE
  63  * instruction is globally visible before any load or store instruction that
  64  * follows the MFENCE instruction. The MFENCE instruction is ordered with
  65  * respect to all load and store instructions, other MFENCE instructions, any
  66  * SFENCE and LFENCE instructions, and any serializing instructions (such as
  67  * the CPUID instruction).
  68  */
  69 #ifdef HAVE_SYNC_INTRINSICS
  70 #   define __cilkrts_fence() __sync_synchronize()
  71 #elif defined __ICC || defined __GNUC__
  72     /* mfence is a strict subset of lock add but takes longer on many
  73      * processors. */
  74 // #   define __cilkrts_fence() __asm__ volatile ("mfence")
  75     /* On MIC, fence seems to be completely unnecessary.
  76      * Just for simplicity of 1st implementation, it defaults to x86 */
  77 #   define __cilkrts_fence() __asm__ volatile ("lock addl $0,(%rsp)")
  78 // #elif defined _WIN32
  79 // #   pragma intrinsic(_ReadWriteBarrier)
  80 // #   define __cilkrts_fence() _ReadWriteBarrier()
  81 #else
  82 COMMON_SYSDEP void __cilkrts_fence(void); ///< MFENCE instruction
  83 #endif