[PATCH 3/3] powerpc: bpf: implement in-register swap for 64-bit endian operations
Benjamin Herrenschmidt
benh at au1.ibm.com
Mon Jan 16 02:00:58 AEDT 2017
On Fri, 2017-01-13 at 23:22 +0530, 'Naveen N. Rao' wrote:
> > That rather depends on whether the processor has a store to load forwarder
> > that will satisfy the read from the store buffer.
> > I don't know about ppc, but at least some x86 will do that.
>
> Interesting - good to know that.
>
> However, I don't think powerpc does that and in-register swap is likely
> faster regardless. Note also that gcc prefers this form at higher
> optimization levels.
Of course powerpc has a load-store forwarder these days, however, I
wouldn't be surprised if the in-register form was still faster on some
implementations, but this needs to be tested.
Ideally, you'd want to try to "optimize" load+swap or swap+store
though.
Cheers,
Ben.
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