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From: kenner@vlsi1.ultra.nyu.edu (Richard Kenner)
Message-Id: <10201281935.AA25716@vlsi1.ultra.nyu.edu>
To: law@redhat.com
Subject: Re: paradoxical subreg problem
Cc: gcc@gcc.gnu.org
X-SW-Source: 2002-01/txt/msg01820.txt.bz2

    Don't assume you can break it into two expressions.  Consider the
    expression as it stands (and as combine creates it).

Sure, but I'm trying to define what it means by comparison with
two expressions.

    So with your assertions in mind are these two expresions equivalent?

    (and:SI (subreg:SI (mem:QI) 0) (const_int 255))

    (subreg:SI (mem:QI X) 0)

I'd be inclined to say "yes".