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

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

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?

Thanks,
- Tom