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Re: [PATCH] rebuild frequency after vrp
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: Jeff Law <law at redhat dot com>
- Cc: Jan Hubicka <hubicka at ucw dot cz>, Dehao Chen <dehao at google dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Richard Biener <richard dot guenther at gmail dot com>, Jakub Jelinek <jakub at redhat dot com>, mjambor at suse dot cz
- Date: Mon, 2 Jun 2014 22:27:01 +0200
- Subject: Re: [PATCH] rebuild frequency after vrp
- Authentication-results: sourceware.org; auth=none
- References: <CAO2gOZWFOuG2O0RLkkT5+tZOpDg+-=pBQk--88X+A-qObgDayw at mail dot gmail dot com> <20140602161326 dot GC16816 at kam dot mff dot cuni dot cz> <CAO2gOZV8WH5_u4_pxCApahgB2F9f=g=6PYb9u0Ppcw1GMLU82Q at mail dot gmail dot com> <538CAA25 dot 1010309 at redhat dot com> <20140602180722 dot GD16816 at kam dot mff dot cuni dot cz> <538CBECC dot 5030902 at redhat dot com>
> On 06/02/14 12:07, Jan Hubicka wrote:
> >It is one of reasions why I think it would be cool to do jump threading in
> >early opts, too, at least in a lightweidt form.
> Conceptually it's pretty easy to do during the into-ssa step. Not
> sure it it'd catch the cases you care about though.
Yep, it may be an option, too. I always had in mind Muchnick style cheap
DOM pass run during into-SSA or as very first cleanup to get rid of unnecesary
code quickly and cheaply. Our DOM is bit different beast though :).
Very basic jump threading may fit here - never really tought about that.
You probably know better than me how many of threading oppurtunities are
"obvious" and how many are the difficult ones solved by VRP&DOM. My gut feeling
is that doing the obvious ones may be good enough. But I do not know.