Re: [stage1][PATCH] Lower VEC_COND_EXPR into internal functions.

[Richard Sandiford <richard.sandiford@arm.com>]

Martin Liška <mliska@suse.cz> writes:
> Hi.
>
> There's a new patch that adds normal internal functions for the 4
> VCOND* functions.
>
> The patch that survives bootstrap and regression
> tests on x86_64-linux-gnu and ppc64le-linux-gnu.

I think this has the same problem as the previous one.  What I meant
in yesterday's message is that:

  expand_insn (icode, 6, ops);

is simply not valid when icode is allowed to FAIL.  That's true in
any context, not just internal functions.  If icode does FAIL,
the expand_insn call will ICE:

  if (!maybe_expand_insn (icode, nops, ops))
    gcc_unreachable ();

When using optabs you either:

(a) declare that the md patterns aren't allowed to FAIL.  expand_insn
    is for this case.

(b) allow the md patterns to FAIL and provide a fallback when they do.
    maybe_expand_insn is for this case.

So if we keep IFN_VCOND, we need to use maybe_expand_insn and find some
way of implementing the IFN_VCOND when the pattern FAILs.

Thanks,
Richard