[Bug tree-optimization/77848] Gimple if-conversion results in redundant comparisons

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77848

--- Comment #14 from rguenther at suse dot de <rguenther at suse dot de> ---
On November 5, 2016 4:31:54 PM GMT+01:00, "wschmidt at gcc dot gnu.org"
<gcc-bugzilla@gcc.gnu.org> wrote:
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77848
>
>--- Comment #13 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
>SPEC cpu2006 on powerpc64le-unknown-linux-gnu with the simple patch:
>
>Geomean, integer:  +0.2%
>Geomean, float:    +0.5%
>Geomean, overall:  +0.4%
>
>Notable improvements:
>  454.calculix:    +3.7%
>  453.povray:      +3.4%
>  458.sjeng:       +1.4%
>  429.mcf:         +1.2%
>  445.gobmk:       +1.2%
>  471.omnetpp:     +1.2%
>
>Notable degradations:
>  403.gcc:         -1.8%
>
>Other results in noise (+/- 1.0%)
>
>Thus, not too bad for a simple patch, though we don't like seeing
>403.gcc
>degrade.

Analyzing would be useful, I suspect missed RTL if-conversion opportunities.

>I've made some progress on the outer loop vectorization issue, but
>haven't
>completely solved it yet.  I'll try to have something to look at there
>in the
>next couple of days.

I'd try detecting the outer loop vect CFG shape the vectorizer handles in
if-combersion and then simply version the outer loop...  Of course needs
handling of the VECTORIZED conditional on an outer loop in the vectorizer.