Jeff,
thanks again for suggestions.
As I understand it (perhaps wrongly), actual splitting only occurs
after combine pass (by split1 pass).
The combine, does, match one of my patterns (lshift:SI
(zero_extend:QI....), 8/16/24). The other splitters (zero_extend) are
"matched" initially - since they are standard insn.
I dont think this matters, if neither is split until split1 - (or does
combine perform a split that is hidden from the dump files?)
If your description is correct, you may have answered the question -
combine is before split1 so there are no further optimisation perfromed
on any split - since simplfy-rtx is never called.
I could use expand - but I know that will cause a world of hurt by
missing optimisations at the "word" level. So new psuedos seems my
only way forward (at the target level)
Which optimiser/pass would benefit from handling subregs better?
best regards
Andy
-----Original Message-----
From: Jeff Law <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Cc: gcc@gcc.gnu.org
Sent: Tue, 19 Feb 2008 2:47 pm
Subject: Re: Redundant logical operations left after early splitting
[EMAIL PROTECTED] wrote:
The RTL for IOR Rx,0 does use subregs (since I use
simplify_gen_subreg > in splitter.)
> Perhaps I should generate new pseudo QI registers instead before
reload?
It's been a long time, but yes, you could look into creating new
registers if you're early into in the optimization pipeline. Your
alternative is to extend the optimizers to better handle subregs
better.
The latter is far more general and would probably help in numerous
situations and is definitely worth a looksie to see if it can be
done easily.
> Is there any particular function or pass that should be dealing
with IOR > rx,0 - that I could trace thru and figure out why it does
not like it > (or never gets there)?
I would be looking in combine and simplify-rtx (which is called by
combine). If your splitter triggers after combine, then I'm not
immediately sure where to look -- I'm not offhand aware of a pass
after combine which would call into simplify-rtx to perform this
optimization.
jeff
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