[FFmpeg-devel] [PATCH] Revert "lavu/atomic: add support for the new memory model aware gcc built-ins"

[James Almer]

On 3/7/2017 3:47 AM, wm4 wrote:
> On Tue,  7 Mar 2017 00:29:53 -0300
> James Almer <jamrial at gmail.com> wrote:
> 
>> This reverts commit faa9d2982969c999ab0e443a226eff116f7f8e4b.
>>
>> This change became superfluous when support for C11 atomics was introduced.
>> Reverting it will make the removal of this implementation in an upcoming
>> merge conflict free.
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>  configure              |  4 +---
>>  libavutil/atomic_gcc.h | 17 -----------------
>>  2 files changed, 1 insertion(+), 20 deletions(-)
>>
>> diff --git a/configure b/configure
>> index 0199fec5c0..6350942ef9 100755
>> --- a/configure
>> +++ b/configure
>> @@ -1821,7 +1821,6 @@ ARCH_FEATURES="
>>  
>>  BUILTIN_LIST="
>>      atomic_cas_ptr
>> -    atomic_compare_exchange
>>      machine_rw_barrier
>>      MemoryBarrier
>>      mm_empty
>> @@ -2322,7 +2321,7 @@ symver_if_any="symver_asm_label symver_gnu_asm"
>>  valgrind_backtrace_deps="!optimizations valgrind_valgrind_h"
>>  
>>  # threading support
>> -atomics_gcc_if_any="sync_val_compare_and_swap atomic_compare_exchange"
>> +atomics_gcc_if="sync_val_compare_and_swap"
>>  atomics_suncc_if="atomic_cas_ptr machine_rw_barrier"
>>  atomics_win32_if="MemoryBarrier"
>>  atomics_native_if_any="$ATOMICS_LIST"
>> @@ -5533,7 +5532,6 @@ if ! disabled network; then
>>  fi
>>  
>>  check_builtin atomic_cas_ptr atomic.h "void **ptr; void *oldval, *newval; atomic_cas_ptr(ptr, oldval, newval)"
>> -check_builtin atomic_compare_exchange "" "int *ptr, *oldval; int newval; __atomic_compare_exchange_n(ptr, oldval, newval, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)"
>>  check_builtin machine_rw_barrier mbarrier.h "__machine_rw_barrier()"
>>  check_builtin MemoryBarrier windows.h "MemoryBarrier()"
>>  check_builtin sarestart signal.h "SA_RESTART"
>> diff --git a/libavutil/atomic_gcc.h b/libavutil/atomic_gcc.h
>> index 5f9fc49ba0..2bb43c3cea 100644
>> --- a/libavutil/atomic_gcc.h
>> +++ b/libavutil/atomic_gcc.h
>> @@ -28,40 +28,27 @@
>>  #define avpriv_atomic_int_get atomic_int_get_gcc
>>  static inline int atomic_int_get_gcc(volatile int *ptr)
>>  {
>> -#if HAVE_ATOMIC_COMPARE_EXCHANGE
>> -    return __atomic_load_n(ptr, __ATOMIC_SEQ_CST);
>> -#else
>>      __sync_synchronize();
>>      return *ptr;
>> -#endif
>>  }
>>  
>>  #define avpriv_atomic_int_set atomic_int_set_gcc
>>  static inline void atomic_int_set_gcc(volatile int *ptr, int val)
>>  {
>> -#if HAVE_ATOMIC_COMPARE_EXCHANGE
>> -    __atomic_store_n(ptr, val, __ATOMIC_SEQ_CST);
>> -#else
>>      *ptr = val;
>>      __sync_synchronize();
>> -#endif
>>  }
>>  
>>  #define avpriv_atomic_int_add_and_fetch atomic_int_add_and_fetch_gcc
>>  static inline int atomic_int_add_and_fetch_gcc(volatile int *ptr, int inc)
>>  {
>> -#if HAVE_ATOMIC_COMPARE_EXCHANGE
>> -    return __atomic_add_fetch(ptr, inc, __ATOMIC_SEQ_CST);
>> -#else
>>      return __sync_add_and_fetch(ptr, inc);
>> -#endif
>>  }
>>  
>>  #define avpriv_atomic_ptr_cas atomic_ptr_cas_gcc
>>  static inline void *atomic_ptr_cas_gcc(void * volatile *ptr,
>>                                         void *oldval, void *newval)
>>  {
>> -#if HAVE_SYNC_VAL_COMPARE_AND_SWAP
>>  #ifdef __ARMCC_VERSION
>>      // armcc will throw an error if ptr is not an integer type
>>      volatile uintptr_t *tmp = (volatile uintptr_t*)ptr;
>> @@ -69,10 +56,6 @@ static inline void *atomic_ptr_cas_gcc(void * volatile *ptr,
>>  #else
>>      return __sync_val_compare_and_swap(ptr, oldval, newval);
>>  #endif
>> -#else
>> -    __atomic_compare_exchange_n(ptr, &oldval, newval, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
>> -    return oldval;
>> -#endif
>>  }
>>  
>>  #endif /* AVUTIL_ATOMIC_GCC_H */
> 
> Sounds like a good thing.

Pushed.