[U-Boot] [PATCH] arm: use common instructions applicable to armv7m & other arm archs
Albert ARIBAUD
albert.u.boot at aribaud.net
Fri Jan 29 18:15:46 CET 2016
Hello Vikas,
On Mon, 18 Jan 2016 18:52:57 -0800, Vikas Manocha
<vikas.manocha at st.com> wrote:
> BIC instruction to clear the SP is not allowed in armv7m & is deprecated
> in ARMv6T2 & above. This patch cleans the code by using instructions allowed
> for armv7m as well as other Arm archs.
I am not against this patch, which has merits on its own; but the
commit message above raises a couple of questions.
1. It seems to imply that in the current arch/arm/lib/crt0.S, BIC is
incorrectly being used on sp. However, it is *not*; it is used on r3,
precisely because it cannot be used directly on sp, as the comment
before the bic instruction clearly states. Why does the commit
message raise this non-issue?
2. I could not find any information on BIC being deprecated in
Architecture Reference Manuals of either ArmV7 (section "Deprecated
Features in ARMv7-M", or ARMv6-M (section "Deprecated and Obsolete
Features"). Where does this information come from?
Amicalement,
--
Albert.
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