[Bug target/71279] [6/7 Regression] ICE on trunk gcc with knl target

[ienkovich at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71279

--- Comment #3 from Ilya Enkovich <ienkovich at gcc dot gnu.org> ---
This looks similar to PR70251 but this time transformation is performed in
folding.  Here is a description of applied transformation:

/* Convert A ? 0 : 1 to !A.  This prefers the use of NOT_EXPR     
   over COND_EXPR in cases such as floating point comparisons.  */

This doesn't work for boolean vectors with scalar mode.  So we should disable
transformation for vec_cond_expr or at least for boolean vectors with scalar
mode.