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Re: IRA for GCC 4.4
On Mon, 2008-04-28 at 18:07 -0400, Vladimir Makarov wrote:
> I am currently working on bit matrix compression. It is not implemented
> yet. I hope it will be ready in a week.
Ahh, ok. Well, hopefully the code I wrote on the trunk is useful for IRA.
If you have questions about it, let me know, or if you want me to look into
it on IRA, just point me to your current code that does this and I'll try
and take a look when I have some free cycles.
I'll note that the real key to eliminating the space from the bit matrix
isn't that we know two allocnos do not interfere, but rather that we know
we'll never test for whether they conflict or not. Since our definition
of conflict is "live at the definition of another", that simply translates
into, if they're never simultaneously live, then we'll never call any
bit matrix routines asking whether they conflict or not, so we don't
need to reserve space for any conflict info.
The fact that local allonocs from different blocks are never simultaneously
live was just a very easy and inexpensive property to measure. If your live
range info can easily and cheaply partition the allocnos into sets that are
and are not live simultaneously, then you should be able to see some further
reductions over what I'm seeing...which I think I've shown, can be considerable.
Peter