[U-Boot] Query on CONFIG_SYS_THUMB_BUILD

Bill Pringlemeir
2014-11-20T16:34:45Z

> On Wed, 19 Nov 2014 13:34:34 -0500, Bill Pringlemeir
> <bpringlemeir@nbsps.com> wrote:

>>>>> In message <20141119074214.3d414ce6@lilith> Albert wrote:

>>>>>> For -mauto-it, it is not documented in the gas documentation
>>>>>> online or in my current as' --target-help. I'll dig this deeper
>>>>>> today, but barring any scream from me, the change above is fine
>>>>>> globally in U-Boot.

>>>> On 19 Nov 2014, wd at denx.de wrote:
>>
>>>>> Apparently this [1] is where it is coming from; no further
>>>>> documentation there, though.
>>>>
>>>>> [1] https://sourceware.org/ml/binutils/2009-05/msg00132.html
>>
>>> On Wed, 19 Nov 2014 11:31:05 -0500, Bill Pringlemeir
>>
>>>> I would think that if this worked they would make it automatic and
>>>> not an option. Probably this is only in certain binutils/as.

>>>> With 4.6.3 and 4.9.1 I do not have this option,

>> On 19 Nov 2014, albert.u.boot at aribaud.net wrote:

>>> Which option do you mean? -mimplicit-it or -mauto-it?

>> '-mauto-it' , which I think if it is working correctly would be
>> rolled into '-mimplicit-it' as it generates better code (for an
>> assembler :). I followed the thread above and the patch originator
>> says he needs to fix section issues and the 'command line options'
>> and he would follow up the proposed patch.

On 20 Nov 2014, albert.u.boot at aribaud.net wrote:

> I am getting lost, even when reading (quickly, I admit) the patch that
> adds it; I don't see what -mauto-it does exactly. Can you summarize
> and clarify the effects of -mimplicit-it (I guess I know this one but
> it's never a bad thing to get a second opinion), -mauto-it and their
> interaction?

I guess you know how the 'IT' works. The Ubuntu/Debian people give a
good explanation in a few paragraphs,

https://wiki.ubuntu.com/ARM/Thumb2PortingHowto#Conditional_Execution

My trying to explain this may have confused thing...

Here is Wolfgang's reference,

https://sourceware.org/ml/binutils/2009-05/msg00132.html

Here is a 2nd reference,

https://sourceware.org/ml/binutils/2009-06/msg00162.html

Originally Daniel Gutson used '-mauto-it' and then it was converted to
'-mimplicit-it'.

I am not sure if '-mauto-it' exists in the wild. I have never heard of
that option before seeing this email thread. Also my assembler says,

Assembler messages:
Error: unrecognized option -mauto-it

I have built with the most recent binutils, gcc4.9.1 using crosstool-ng.
Maybe only some non-mainline tools picked up this '-mauto-it' patch. I
don't think it hurts to support '-mauto-it', but an assembler test
should be done to see if it accepts the option.

hth,
Bill Pringlemeir.