[U-Boot] [PATCH v2] arm: Switch to -mno-unaligned-access when supported by the compiler

Albert ARIBAUD
2014-02-10T09:24:47Z

Hi Tom,

On Tue, 4 Feb 2014 12:05:33 -0500, Tom Rini <trini@ti.com> wrote:

> When we tell the compiler to optimize for ARMv7 it assumes a default of
> unaligned accesses being supported at the hardware level and can make
> use of this to perform what it deems as an optimization in any case,
> including allowing for data to become unaligned. We explicitly disallow
> this hardware feature so we must tell the compiler.
>
> Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
> Cc: Mans Rullgard <mans@mansr.com>
> Signed-off-by: Tom Rini <trini@ti.com>

NAK -- the discrepancy between the compiler being told to allow native
unaligned accesses while at the same time telling the hardware to trap
them is conscious and voluntary. It was chosen to help detect unaligned
accesses which are rarely necessary and can be explicitly performed by
software on a case by case basis.

If and when a specific file requires unaligned access which cannot be
made by some other mean than enabling -mno-unaligned-access, then this
file should have it added, not the whole of U-Boot.

Amicalement,
--
Albert.