Re: [PATCH, PR83327] Fix liveness analysis in lra for spilled-into hard regs

[Tom de Vries <Tom_deVries@mentor.com>]

On 01/08/2018 05:32 PM, Tom de Vries wrote:
> On 12/18/2017 05:57 PM, Vladimir Makarov wrote:
>>
>>
>> On 12/15/2017 06:25 AM, Tom de Vries wrote:
>>>
>>> Proposed Solution:
>>>
>>> The patch addresses the problem, by:
>>> - marking the hard regs that have been used in lra_spill in
>>>   hard_regs_spilled_into
>>> - using hard_regs_spilled_into in lra_create_live_ranges to
>>>   make sure those registers are marked in the conflict_hard_regs
>>>   of pseudos that overlap with the spill register usage
>>>
>>> [ I've also tried an approach where I didn't use 
>>> hard_regs_spilled_into, but tried to propagate all hard regs. I 
>>> figured out that I needed to mask out eliminable_regset.  Also I 
>>> needed to masked out lra_no_alloc_regs, but that could be due to 
>>> gcn-specific problems (pointers take 2 hard regs), I'm not yet sure. 
>>> Anyway, in the submitted patch I tried to avoid these problems and 
>>> went for the more minimal approach. ]
>>>
>> Tom, thank you for the detail explanation of the problem and solutions 
>> you considered.  It helped me a lot.  Your simple solution is adequate 
>> as the most transformations and allocation are done on the 1st LRA 
>> subpasses iteration.
>>> In order to get the patch accepted for trunk, I think we need:
>>> - bootstrap and reg-test on x86_64
>>> - build and reg-test on mips (the only primary platform that has the
>>>   spill_class hook enabled)
>>>
>>> Any comments?
>>
>> The patch looks ok to me.  You can commit it after successful testing 
>> on x86-64 and mips but I am sure there will be no problems with x86-64 
>> as it does not use spill_class currently (actually your patch might 
>> help to switch it on again for x86-64.  spill_class was quite useful 
>> for x86-64 performance on Intel processors).
>>
> 
> Hi Matthew,
> 
> there's an lra optimization that is currently enabled for MIPS, and not 
> for any other primary or secondary target.
> 
> This (already approved) patch fixes a bug in that optimization, and 
> needs to be tested on MIPS.
> 
> Unfortunately, the optimization is only enabled for MIPS16, and we don't 
> have a current setup to test this.
> 
> Could you help us out here and test this patch for MIPS16 on trunk?

Hi Matthew,

is this something you can help us out with?

Thanks,
- Tom