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Re: Bug in ra-colorize.c:merge_moves?



So, number of webs reduced (number of conflicts will be definitely reduced) and possibility of graph colorization increased. I hope to colorize full graph in next colorization phase.

I'm agree that this method increased a count of allocator passes, but
this method must improve code quality.

Sure, but that's not the problem. The problem is the code quality increase isn't measurable.
I couldn't measure a significant difference in spec, or other benchmarks (like skidmarks, for instance), on x86 or powerpc.
No measurable difference in benchmarks + increased time in allocation = bad.
I wouldn't complain so much if it increased code quality some measurable amount, but if it does, i can't find it.


If code quality was our only measure, we could do ILP based optimal register allocation and spilling.

Denis.

PS: Especially for Daniel ! Look to ra-rewrite.c: actual_spill

-------------- fragment of ra-rewrite.c ----------------
actual_spill (spill_p)
     int spill_p ATTRIBUTE_UNUSED;
{
  int i;
  bitmap new_deaths;

/* If we have a webs colored by an_unusable_color (ie we think that they are
already in frame) we must put such webs to frame. */
if (/* !spill_p && */ subst_to_stack_p ())
#------^^^^^^^^^^^^^^^^ Just remove comments and you will have extra
# passes only at end of allocation process.
/* If you uncomment the SPILL_P usage then you will have a calls to
assign_stack_slots only at end of allocation process.
See to the caller of actual_spill. */
{
-------------------------------------------------------


Daniel. Try to remove comments around `!spill_p &&' and compare generated code
quality for both cases (commented and not commented `!spill_p &&').


I tried this once, actually, about a week ago, and it caused bootstrap failures.


--Dan



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