[Bug tree-optimization/89570] [9 Regression] ICE in prepare_cmp_insn, at optabs.c:4001

[rsandifo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89570

--- Comment #6 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> ---
I think there are two things here:

(1) checking earlier for whether an ifn is supported.

    I think we should get genmatch to do that itself rather than
    manually do it for each expansion.

(2) not splitting out the condition in a (vec_)cond_expr if it
    isn't supported as a stand-alone operation

It looks like (2) is the real fix and (1) is a compile-time
improvement that happens to make (2) latent in this case.

How is it possible for a condition to be supported only in
a VEC_COND_EXPR?  Isn't a stand-alone condition equivalent
to a VEC_COND_EXPR between {-1, ...} and {0, ...}?