[U-Boot] [PATCH] disk:efi: avoid unaligned access on efi partition
Albert ARIBAUD
albert.u.boot at aribaud.net
Tue Oct 15 19:07:49 CEST 2013
Hi Måns,
On Tue, 15 Oct 2013 17:29:24 +0100, Måns Rullgård <mans at mansr.com>
wrote:
> Albert ARIBAUD <albert.u.boot at aribaud.net> writes:
>
> > Hi Måns,
> >
> > On Tue, 15 Oct 2013 16:23:44 +0100, Måns Rullgård <mans at mansr.com>
> > wrote:
> >
> >> On the compiler side, gcc traditionally did not issue unaligned
> >> load/store instructions on ARM.
> >
> > Please be specific: gcc did not emit *native* unaligned accesses.
>
> Please explain what you mean by "native unaligned access".
By this I mean an unaligned access performed with a single transfer,
initiated by a single processor instruction, as opposed to an
unaligned access performed with a series of smaller, aligned,
transfers (and possibly additional operations) initiated by a sequence
of processor instructions (emulated, if you will).
Prior to 4.7, gcc did emit unaligned accesses if instructed to at the
source code level; they were however emulated. From 4.7 onward, it was
possible to choose whether unaligned transfers should be performed
native or emulated, the default being native for ARMv6+, and emulated
for the rest.
Amicalement,
--
Albert.
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