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

[Matthew Fortune <Matthew.Fortune@mips.com>]

Tom de Vries <Tom_deVries@mentor.com> writes:
> 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?

Hi Tom,

I've just commented on the bug report that I've set of some builds to try
and give some assurance. It is far from comprehensive but it is as good as
the normal testing I do for MIPS16.

Thanks,
Matthew