[Bug tree-optimization/54717] [4.8 Regression] Runtime regression: polyhedron test "rnflow" degraded

[sergos.gnu at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54717

--- Comment #9 from Sergey Ostanevich <sergos.gnu at gmail dot com> 2012-10-08 08:55:25 UTC ---
Thanks for the reduced test, Dominique!

I see that vectorized did not manage to generate MIN after the change. Also, it
is looks pretty similar to what I posted at first: there was no prephitmp
created for the xxtrt_[]


> ival2_15 = _85 < prephitmp_266 ? ival2_10 : iva
> prephitmp_237 = MIN_EXPR <_85, prephitmp_266>;
-----------------------
< _86 = (integer(kind=8)) ival2_14;
< _87 = _86 + -1;
< _88 = *xxtrt_46(D)[_87];
< ival2_15 = _85 < _88 ? ival2_10 : ival2_14;

I suspect that one of the iterator you removed - possibly VEC_iterate - made
more traverse than that you created?

I also double check that for the reduced test MIN did not generated and not
appears in assembly. PMU measurements (Vtune) confirms that BBLOCKs missing min
contributes the difference in clocks.