Re: [patch, ARM] Fix PR42017, LR not used in leaf functions

[Chung-Lin Tang <cltang at codesourcery dot com>]

On 2011/5/20 äå 07:41, Ramana Radhakrishnan wrote:
> On 17/05/11 14:10, Chung-Lin Tang wrote:
>> On 2011/5/13 04:26 PM, Richard Sandiford wrote:
>>> Richard Sandiford<richard.sandiford@linaro.org>  writes:
>>>> Chung-Lin Tang<cltang@codesourcery.com>  writes:
>>>>> My fix here simply adds 'reload_completed' as an additional condition
>>>>> for EPILOGUE_USES to return true for LR_REGNUM. I think this should be
>>>>> valid, as correct LR save/restoring is handled by the
>>>>> epilogue/prologue
>>>>> code; it should be safe for IRA to treat it as a normal call-used
>>>>> register.
>>>>
>>>> FWIW, epilogue_completed might be a more accurate choice.
>>>
>>> I still stand by this, although I realise no other target does it.
>>
>> Did a re-test of the patch just to be sure, as expected the test results
>> were also clear. Attached is the updated patch.
> 
> Can you specify what you tested with this patch ?

Native bootstrap success, plus C/C++ and libstdc++ tests. IIRC I also
saw one or two FAIL->PASS in the results too (forgot specific testcases)

> 
> So, it's interesting to note that the use of this was changed in 2007 by
> zadeck as a part of the df merge.
> 
> I can't find the patch trail beyond this on the lists.
> 
> http://gcc.gnu.org/viewvc/branches/dataflow-branch/gcc/config/arm/arm.h?r1=120281&r2=121501
> 
> 
> It might be better to understand why this was done in the first place
> for the ARM port as part of the Dataflow bring up and why folks wanted
> to make this unconditional.

Oh dear, more archeology...

Thanks,
Chung-Lin