Re: [RFC] Enable tune-thumb.inc for all armv5t and armv6t machines

[Paul Sokolovsky <pmiscml@gmail.com>]

Hello Koen,

Thursday, December 21, 2006, 7:24:54 PM, you wrote:

> Hi,

> Today I seperated the thumb bits from
> conf/machine/include/ipx4xx.conf into
> conf/machine/include/. I'd like to enable for all >=v5t machines, but I'm unsure about
> using positive or negative logic.

  What about armv4t?

> * positive logic: might break for (soft)fpa distros that don't disable it, no problem for
> EABI distros
> * negative logic: no difference to status quo, but having negative logic in tune-* files
> feels a bit wrong.

  It's very nice to see ("real") thumb support being added to OE in
general! But I guess, it's too bold a step to switch to it be the
default. There're usual risk management issues (who knows what bugs
CPUs/software have regarding thumb), plus, thumb has known drawback of
reduced performance.

  In ideal case, thumb usage would be set per-package, with most
of libraries being normal code, and most apps - thumb (and in this
case thumb can be indeed the default).


> If you need numbers:
> http://ewi546.ewi.utwente.nl/tmp/thumb/comparison.txt (package:
> <thumb size> <regular size> (<unit>))

  Using ipk sizes is of course pretty heuristical ;-). IMHO, those
sizes are not too much convincing at all, but I'm sure raw exe sizes
are better, and striving for that ideal case is worthy task ;-)

> what do you all think?

> regards,

> Koen


-- 
Best regards,
 Paul                            mailto:pmiscml@gmail.com