From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joern Rennecke <amylaar@cygnus.co.uk>
To: law@cygnus.com
Cc: amylaar@cygnus.co.uk, wilson@cygnus.com, egcs@cygnus.com
Subject: Re: patch for update_flow_info REG_WAS_0
Date: Fri, 13 Feb 1998 02:16:00 -0000
Message-id: <199802131014.KAA10625@phal.cygnus.co.uk>
References: <25382.887357891@hurl.cygnus.com>
X-SW-Source: 1998-02/msg00598.html

> One might argue that the note should have been removed when the
> insn was deleted.  Can you look into that?

I first looked at the REG_WAS_0 description in rtl.texi.  It appears that
is a known fact that the insn might be deleted.  So I presume that that's
OK, and we have to deal with it.

@findex REG_WAS_0
@item REG_WAS_0
The single output of this insn contained zero before this insn.
@var{op} is the insn that set it to zero.  You can rely on this note if
it is present and @var{op} has not been deleted or turned into a @code{note};
its absence implies nothing.
@end table

These notes describe linkages between insns.  They occur in pairs: one
insn has one of a pair of notes that points to a second insn, which has
the inverse note pointing back to the first insn.