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).