[PATCH 1/2] S390: Optimize atomic macros.

[Stefan Liebler]

On 02/28/2017 08:33 AM, Torvald Riegel wrote:
> On Mon, 2017-02-27 at 12:36 +0100, Stefan Liebler wrote:
>> This patch activates c11 atomic builtins by defining
>> USE_ATOMIC_COMPILER_BUILTINS to 1.
>> Note:
>> E.g. in nptl/pthread_key_delete.c if compiled with GCCs 6 and before,
>> an extra stack-frame is generated and the old value is stored on stack
>> before cs instruction but it never loads this value from stack.
>> An unreleased GCC 7 omit those stack operations.
>>
>> E.g. in nptl/pthread_once.c the condition code of cs instruction is
>> evaluated by a sequence of ipm, sra, compare and jump instructions
>> instead of one conditional jump instruction.
>> This also occurs with an unreleased GCC 7.
>>
>> These shortcomings does not really hurt.  Nevertheless, the gcc guys are
>> investigating those ones and plan to fix them before GCC 7 release.
>>
>> The atomic_fetch_abc_def c11 builtins are now using load-and-abc
>> instructions on z196 zarch and higher cpus instead of a loop
>> with compare-and-swap instruction.
>>
>> Some of the non-c11 atomic macros from include/atomic.h are now
>> implemented with help of the c11 atomic builtins.
>> The other non-c11 atomic macros are using the macros defined here.
>>
>> Optimizations like using load-and-and for exchanging memory to zero
>> will be done by GCC in future.
>>
>> ChangeLog:
>>
>> 	* sysdeps/s390/atomic-machine.h
>> 	(USE_ATOMIC_COMPILER_BUILTINS): Define to 1.
>> 	(__arch_compare_and_exchange_val_8_acq,
>> 	__arch_compare_and_exchange_val_16_acq,
>> 	__arch_compare_and_exchange_val_32_acq,
>> 	__arch_compare_and_exchange_val_64_acq):
>> 	Delete macro.
>> 	(atomic_compare_and_exchange_val_acq,
>> 	atomic_compare_and_exchange_val_rel,
>> 	atomic_compare_and_exchange_bool_acq,
>> 	catomic_compare_and_exchange_bool_acq,
>> 	atomic_exchange_acq, atomic_exchange_rel,
>> 	atomic_exchange_and_add_acq,
>> 	atomic_exchange_and_add_rel,
>> 	catomic_exchange_and_add, atomic_or_val,
>> 	atomic_or, catomic_or, atomic_bit_test_set,
>> 	atomic_and_val, atomic_and, catomic_and):
>> 	Define macros with help of c11 atomic builtins.
>
> s/c11/C11/ throughout the patch.
> Besides that, this looks good to me.  Thanks.
>
Thanks for review.
I've changed c11 to C11 and committed this patch.
Bye.
Stefan