Re: [PATCH] x86: Use sse<>integer costs for vec_to_scalar/scalar_to_vec

[Richard Biener]

On Wed, Sep 9, 2026 at 11:42 AM Richard Biener
<richard.guent...@gmail.com> wrote:
>
> On Wed, Sep 9, 2026 at 9:07 AM H.J. Lu <hjl.to...@gmail.com> wrote:
> >
> > Use the sse_to_integer cost for vec_to_scalar and the integer_to_sse
> > cost for scalar_to_vec.
>
> As discussed in the PR this isn't correct.

We should instead try to make these gcc_unreachable () and handle them
upthread.  They should only get through add_stmt_cost, not directly.

> > PR target/127268
> > * config/i386/i386.cc (ix86_default_vector_cost): Use the
> > sse_to_integer cost for vec_to_scalar and the integer_to_sse
> > cost for scalar_to_vec.
> >
> > No regressions on Linux/x86-64.
> >
> > --
> > H.J.