On Fri, May 10, 2024 at 12:19:35PM +0200, Richard Biener wrote:
> On Fri, May 10, 2024 at 11:06 AM Segher Boessenkool
> <seg...@kernel.crashing.org> wrote:
> > *All* code using a cost will have to be inspected and possibly adjusted
> > if you decide to use a different value for "unknown" than what we have
> > had for ages. All other cost functions interacting with this one, too.
>
> Btw, looking around pattern_cost is the only API documenting this special
> value and the function after it using this function, insn_cost does the same
> but
>
> int
> insn_cost (rtx_insn *insn, bool speed)
> {
> if (targetm.insn_cost)
> return targetm.insn_cost (insn, speed);
>
> and the target hook doesn't document this special value. set_src_cost
> doesn't either, btw (that just uses rtx_cost). So I don't think how
> pattern_cost handles the set_src_cost result is warranted. There's
> simply no way to detect whether set_src_cost returns an actual
> value - on the contrary, it always does.
I introduced insn_cost. I didn't think about documenting that 0 means
unknown, precisely because that is so pervasive!
Segher
