On Thu, 2016-15-09 at 09:03:21 UTC, Nicholas Piggin wrote:
> The mflr r10 instruction was left over saving of lr when the code used
> lr to branch to system_call_entry from the exception handler. That was
> changed by 6a404806d to use the count register. The value is never used
> now, so mflr can be removed, and r10 can be used for storage rather than
> spilling to the SPR scratch register.
> The scratch register spill causes a long pipeline stall due to the SPR
> read after write. This change brings getppid syscall cost from 406 to
> 376 cycles on POWER8. getppid for non-relocatable case is 371 cycles.
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
> Acked-by: Balbir Singh <bsinghar...@gmail.com>
Applied to powerpc next, thanks.