[Bug rtl-optimization/40209] ICE in iv_analyze_def caused by stale REG_UNUSED note

nvachhar at google dot com gcc-bugzilla@gcc.gnu.org
Fri Jul 24 15:39:00 GMT 2009

------- Comment #5 from nvachhar at google dot com  2009-07-24 15:39 -------
Subject: Re:  ICE in iv_analyze_def caused by 
        stale REG_UNUSED note

loop-iv does need notes, albeit indirectly through the single_set
function.  single_set looks at the REG_UNUSED note, and if all but one
set have that note on it, then it asserts that a parallel set is a
single set.  I do agree that this problem is pervasive through gcc.
Any pass that uses single_set is implicitly a user of reg ntoes.

On Thu, Jul 23, 2009 at 11:27 PM, steven at gcc dot gnu dot
org<gcc-bugzilla@gcc.gnu.org> wrote:
> ------- Comment #4 from steven at gcc dot gnu dot org  2009-07-24 06:27 -------
> A hint, please, about why the patch of comment #2 would be the correct fix.  As
> far as I can tell, loop-iv doesn't need the notes and shouldn't have to clean
> up other passes' mess. This patch also introduces a pass ordering restriction
> that shouldn't be there. And at the very least, if this bug gets papered over
> like this, then there should be a comment in loop-iv that the problem is only
> added to fix bugs elsewhere...
> --
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40209
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