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Re: find_mem_givs SMALL_REGISTER_CLASSES patch
- To: toon at moene dot indiv dot nluug dot nl
- Subject: Re: find_mem_givs SMALL_REGISTER_CLASSES patch
- From: john at feith dot com (John Wehle)
- Date: Sun, 28 Jun 1998 15:39:25 -0400
- Cc: egcs-patches at cygnus dot com
> With all the negatives in the above sentences I had to look at the
> code to understand what you meant :-), but I think you are right.
I'll have to try and be more positive in the future. :-)
> The Politically Correct Theory is that this should be handled by
> Richard Henderson's combine-givs patch, but it might be that it
> doesn't in its full generality (because ix86 address expressions can
> be quite complicated).
egcs-19980621 with find_mem_givs patch: 105
egcs-19980621 with loop mark 10 patch: 103
> The reason that your patch works is not so
> much because it's the Right Thing on machines with
> SMALL_REGISTER_CLASSES but rather that complicated address
> expressions in ix86 instructions are essentially free.
I'm incline to believe that not recording a giv which is a valid
address * is * the Right Thing to do on a register poor machine if
the other option is to spill registers. Now if my other option
is to record the giv and * not * spill (important) registers than
that sounds like a better Right Thing.
Long turn Richard Henderson's patch is probably a more powerful
change. It certainly would have saved me some time if I had
remembered it. Thank you (and Richard) for reminding me. :-)
-- John
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