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Re: patch to implement thread coloring in IRA


On Wed, Nov 13, 2013 at 6:56 PM, Vladimir Makarov wrote:
>   The following patch improves coloring.  The order of pushing allocnos on
> the coloring stack from a bunch of colorable allocnos was always important
> for generated code performance.  LRA has a mechanism of allocating pseudos
> by threads.  Thread in LRA is a set of non-conflicting pseudos connected by
> moves (or by future reload insns).  Allocating pseudos by threads in LRA
> permits to improve code by increasing chance of removing the move insns.
>
>   So the same mechanism can be used for IRA.  The patch implements it.  The
> difference is only that LRA forms thread statically before allocation
> sub-pass.  That is because the basic allocation are already done in IRA.
> The statically thread forming works well for IRA too.  But even better
> results can be got by dynamically forming threads.  It means that we are
> forming threads during allocation and includes only colorable allocnos.
>
>   The results of using threads in IRA is pretty good.  The average code size
> (text segment) of SPEC2000 is improved (by >0.1% for x86 SPECFP2000 and >
> 0.3% for x86-64 SPECFP2000). The biggest code performance improvement (> 1%)
> is obtained on x86-64 SPECFP2000.  Performance tools report that additional
> code takes only about 0.05% additionally executed insns.


Nice!

Can you please also update the leading comment in ira.c? It seems
worth mentioning this approach under the "Coloring" bullet
(ira.c:176).
(Not sure if that whole comment block is otherwise up to date??)

Ciao!
Steven


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