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

Måns Rullgård
2014-02-10T16:21:53Z

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

> Hi M?ns,
>
> On Mon, 10 Feb 2014 15:14:49 +0000, M?ns Rullg?rd <mans@mansr.com>
> wrote:
>
>> Albert ARIBAUD <albert.u.boot@aribaud.net> writes:
>>
>> > Hi Tom,
>> >
>> > On Mon, 10 Feb 2014 08:21:39 -0500, Tom Rini <trini@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@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.
>> >>
>> >> 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.
>
> I can hardly have "refused to read" a message which I *answered*, laid
> out how I thought the issue should be solved... and got no answer after
> this.

In your reply, you called the important parts of my explanation
irrelevant. That's more or less the same thing.

--
M?ns Rullg?rd
mans at mansr.com