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Re: update address taken: don't drop clobbers
- From: Jeff Law <law at redhat dot com>
- To: Richard Biener <richard dot guenther at gmail dot com>, Marc Glisse <marc dot glisse at inria dot fr>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 16 Oct 2014 11:58:25 -0600
- Subject: Re: update address taken: don't drop clobbers
- Authentication-results: sourceware.org; auth=none
- References: <alpine dot DEB dot 2 dot 02 dot 1406282350110 dot 31815 at stedding dot saclay dot inria dot fr> <CAFiYyc0fRhV09A3C2WT8yQ1ndp9dcyWntCVSPHzhwHb3tgNZLg at mail dot gmail dot com> <alpine dot DEB dot 2 dot 11 dot 1407271853200 dot 22972 at stedding dot saclay dot inria dot fr> <alpine dot DEB dot 2 dot 11 dot 1409071654310 dot 5483 at laptop-mg dot saclay dot inria dot fr> <alpine dot DEB dot 2 dot 11 dot 1410151621380 dot 8286 at stedding dot saclay dot inria dot fr> <543E9BED dot 4070905 at redhat dot com> <CAFiYyc27PjA1A_DZnfWGzU2y10Lp3rEoZs1m7hknq1eJDOqK_Q at mail dot gmail dot com> <alpine dot DEB dot 2 dot 11 dot 1410161321450 dot 27920 at stedding dot saclay dot inria dot fr> <543FFFD8 dot 4090406 at redhat dot com> <6255313F-DDD4-4DA6-B07E-832B251E167F at gmail dot com>
On 10/16/14 11:52, Richard Biener wrote:
I'd walk the SSA_NAMEs at the end checking for zero uses. I'm
curious how often that will trigger :-)
Most often for the initial into SSA I guess. After that only for the
cases we rename a variable which does not happen often. SRA and
update-address-taken cone to my mind.
That'd be my guess too. Jump threading probably creates them as well
since we don't try to find any of the code that becomes dead in the
duplicates after we remove the conditional. Which means after DOM and VRP.
I don't suppose we have a map of newly created names handy anywhere :-)
BTW, I dislike having multiple DCE implementations...
Similarly. The proposal above was just to determine if we should
schedule DCE or not.
jeff