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Re: PPro conditional move problem
- To: hjl at lucon dot org
- Subject: Re: PPro conditional move problem
- From: john at feith dot com (John Wehle)
- Date: Fri, 5 Jun 1998 12:47:27 -0400
- Cc: law at cygnus dot com, egcs-patches at cygnus dot com
> It is kind of braindead. Anyway, I think we can change all non-FP CC
> setting insns to
>
> [(parallel [(set (cc0)
> ..............
> (clobber (match_scratch:HI 1 ""))])]
>
>
> [(set (cc0)
> ......
> (clobber (match_scratch:HI 3 "=a"))]
Isn't this going to impact code generation by requiring a scratch
register for all non-FP CC insns? What about the comparisons which
will not become part of a conditional move?
Actually, as a side note I would like to see some FP CC insns which
don't require a scratch register. I believe that this can be done
in the case of TARGET_CMOVE && !TARGET_IEEE.
> Is this reasonable? If yes, I will try to implement it this weekend.
Is sounds possible. However the conditional move patterns are an
optimization, if the overhead of using them becomes too high then
it's not worth using them. You want to make sure that code not
involving a conditional move isn't impacted by your changes.
-- John
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