tree e4a50c47b5520c119bc4bce0f8329057ad707858
parent ccc0e7dc708ce1bd2e1c4a2b6a180ae7459374de
author Christian Borntraeger <borntraeger@de.ibm.com> 1446077764 +0100
committer Martin Schwidefsky <schwidefsky@de.ibm.com> 1446558048 +0100

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: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>