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- From: Joern Rennecke <joern dot rennecke at superh dot com>
- To: "David S. Miller" <davem at redhat dot com>
- Cc: shebs at apple dot com, dberlin at dberlin dot org, dhazeghi at pacbell dot net, neil at daikokuya dot demon dot co dot uk, ak at suse dot de, gcc at gcc dot gnu dot org
- Date: Wed, 22 May 2002 00:34:55 +0100
- Subject: Re: subreg_regno_offset
- Organization: SuperH UK Ltd.
- References: <3CEAAC32.A2D69FB0@superh.com> <email@example.com>
"David S. Miller" wrote:
> For example, note that when we are creating SUBREG expressions it
> would be easy to compute the register offset and store it in the
> SUBREG itself.
You can't always do that when creating a SUBREG expression, you have to
wait for it to be the SUBREG of a hard register. And since REGs are
shared, you'd have to go over all SUBREGs (how?) after each call to
alter_reg. Moreover, you'd still have to get the offset right in
the first place.
> Then SUBREG_REGNO_OFFSET and SUBREG_REGNO could be
> just as cheap as SUBREG_REG.
But at the expense of extra memory use.
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