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

[Måns Rullgård]

Albert ARIBAUD <albert.u.boot at aribaud.net> writes:

> Hi Tom,
>
> On Mon, 10 Feb 2014 08:21:39 -0500, Tom Rini <trini at ti.com> wrote:
>
>> On Mon, Feb 10, 2014 at 10:24:47AM +0100, Albert ARIBAUD wrote:
>> > Hi Tom,
>> > 
>> > On Tue,  4 Feb 2014 12:05:33 -0500, Tom Rini <trini at 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 at aribaud.net>
>> > > Cc: Mans Rullgard <mans at mansr.com>
>> > > Signed-off-by: Tom Rini <trini at 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.
>> 
>> Right, I recall the discussion, and we chose wrong.
>
> I am quite prepared to discuss whether we chose wrong or right, and
> to change my mind when the conditions are right, but I'll need more than
> such a short and simple statement. :)

I already gave you a detailed explanation some months ago.  You refused
to read it.

-- 
Måns Rullgård
mans at mansr.com