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Re: A blast from the past
- From: law at redhat dot com
- To: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- Cc: gcc at gcc dot gnu dot org
- Date: Fri, 11 Jan 2002 10:11:23 -0700
- Subject: Re: A blast from the past
- Reply-to: law at redhat dot com
> Thu Apr 4 07:34:17 1991 Richard Kenner (kenner at
vlsi1.ultra.nyu.edu)
>
> Wow! That's over a decade ago.
Yup. Long long ago.
> Obviously I can't remember for sure, but my *guess* is that I felt
> canonicalization would move the SUBREG operand to OP0. Unless that's
wrong,
> I think the only way OP1 could be a SUBREG is if both it and OP0 were.
> I don't know why this code didn't try to handle that case.
>
> Sorry, it's just too long ago to know more.
OK. So it seems to me that with the way swap_commutative_operands_p works
these days that we prefer to put the subreg into OP1, in fact the only time
I can see that it would be in OP0 would be if they are both SUBREGs.
With that in mind, I'd like to put in a set of parallel simplifications
which operand on OP1.
This will expose a latent bug in the combiner, but I want it exposed so that
we'll fix it :-)
jeff