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

[Torvald Riegel <triegel at redhat dot com>]

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.