This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH] shrink-wrap: Once more PRs 67778, 68634, and now 68909
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Bernd Schmidt <bschmidt at redhat dot com>
- Cc: gcc-patches at gcc dot gnu dot org, jakub at redhat dot com
- Date: Sun, 20 Dec 2015 10:27:33 -0600
- Subject: Re: [PATCH] shrink-wrap: Once more PRs 67778, 68634, and now 68909
- Authentication-results: sourceware.org; auth=none
- References: <caa43fac2ad48df0eb694edebb60847a29a5763a dot 1450385490 dot git dot segher at kernel dot crashing dot org> <56735F29 dot 7090807 at redhat dot com>
On Fri, Dec 18, 2015 at 02:19:37AM +0100, Bernd Schmidt wrote:
> On 12/17/2015 10:07 PM, Segher Boessenkool wrote:
> >It turns out v4 wasn't quite complete anyway; so here "v5".
> >
> >If a candidate PRE cannot get the prologue because a block BB is
> >reachable from it, but PRE does not dominate BB, we try again with the
> >dominators of PRE. That "try again" needs to again consider BB though,
> >we aren't done with it.
> >
> >This fixes this problem. Tested on the 68909 testcase, and bootstrapped
> >and regression checked on powerpc64-linux. Is this okay for trunk?
>
> This code is getting really quite confusing,
Yes :-( I don't think stage 3 is the time to completely rewrite it though.
> and at the least I think we
> need more documentation of what exactly vec is supposed to contain at
> the entry to the inner while loop here.
Same as in the other loop: vec is a stack of blocks that still need to
be looked at. I can duplicate the comment if you want?
> I'm also beginning to think we should disable this part of the code for
> gcc-6.
That would be a regression (from GCC 5); but I understand your worry.
How about we disable it if any further problems show up?
Segher