Re: Why Thumb-2 only allows very limited access to the PC?

[Carrot Wei <carrot at google dot com>]

Could anybody help to review the small patch
http://gcc.gnu.org/ml/gcc-patches/2010-01/msg00531.html

thanks
Guozhi

On Sat, Jan 9, 2010 at 7:25 PM, Carrot Wei <carrot@google.com> wrote:
> OK, I filed a bug to trace it.
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42671
>
> thanks
> Guozhi
>
> On Thu, Jan 7, 2010 at 6:23 PM, Richard Earnshaw <rearnsha@arm.com> wrote:
>>
>> On Wed, 2010-01-06 at 18:26 +0000, Paul Brook wrote:
>>> On Wednesday 06 January 2010, Carrot Wei wrote:
>>> > So thumb2 can also use the instructions similar to thumb1, right? It
>>> > potentially has better performance and smaller code size.
>>>
>>> Technically yes, however in ARMv7 the relevant instruction (add.n <reg>, pc)
>>> is deprecated.
>>
>> Where'd you get that idea?
>>
>> Annex D of the ARM ARM says that the 16-bit instructions that add SP and
>> PC together (writing either SP or PC) are deprecated, but there's
>> nothing else using PC that's mentioned there other than trying to move
>> PC into SP or vice-versa. ?All the deprecated instructions in this area
>> are pretty meaningless in real life anyway.
>>
>> R.
>>
>>
>