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Re: mark_operand_necessary in tree-ssa-dce.c
- From: Andrew MacLeod <amacleod at redhat dot com>
- To: Daniel Berlin <dberlin at dberlin dot org>
- Cc: gcc mailing list <gcc at gcc dot gnu dot org>, gcc-patches <gcc-patches at gcc dot gnu dot org>, bje at redhat dot com
- Date: Fri, 28 Jan 2005 15:59:38 -0500
- Subject: Re: mark_operand_necessary in tree-ssa-dce.c
- References: <Pine.LNX.email@example.com>
On Wed, 2005-01-26 at 15:08, Daniel Berlin wrote:
> Can someone (ben, i think you wrote this code) please explain to me why we
> require a processed sbitmap in this function?
many fingers have touched and changed the meaning of some of these
functions. I've lost track myself :-)
> ISTM that if we are here, we are going to always mark the statement as
> necessary. And if it was already marked as necessary, we return before we
> put it on the worklist again anyway.
this code looks different than I remember. It look sto me like the
processed bitmap now reflects the necessary attribute as well.
especially from the comment its implied too:
/* Vector indicating an SSA name has already been processed and marked
as necessary. */
static sbitmap processed;
> My thinking goes like this:
> Anyone disagree?
> If not, i'll bootstrap and regtest a patch to remove it
Giving it a try seems worthwhile. It appears to be the only place its
set, so it seems to be the same thing.