s390/Kconfig: use builtin bswap
Depending on the gcc version we can use builtin_bswap instead of architecture functions. Doing so is better than the inline assembly version of load reverse for two reasons: - the sequence of load reversed, apply constant mask, save reversed can be optimized to load, apply reversed mask, save - builtins are slightly better to optimize e.g. gcc instruction scheduler cannot optimize grouping on inline assemblies. To enable set we have to ARCH_USE_BUILTIN_BSWAP. bloat-o-meter results: add/remove: 1/1 grow/shrink: 75/533 up/down: 1711/-9394 (-7683) Suggested-by: NDavid Woodhouse <David.Woodhouse@intel.com> Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com> Acked-by: NHeiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
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