> On Jan 5, 2021, at 8:54 AM, Senthil Kumar Selvaraj via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>
>
> Senthil Kumar Selvaraj writes:
>
>> Georg-Johann Lay writes:
>>
>> ...
>>>
>>> 2) We just saw 100reds of insns being dublicated, basically the whole
>>> machine description except for the few insns that leave cc alone.
>>> Isn't is possible to use define subst for the bulk of the insns and
>>> get a neat code that's better to grasp and to maintain?
>>> After all it's just appending a clobber of reg_cc, and in the current
>>> proposal almost 50% of the backend is just redundent repetitions of
>>> previous insns.
>
> I could not find a way to get define_subst to do define_insn_and_split -
> other targets using the same approach (pdp11, h8300) have the
> duplication as well.
I ran into the same issue, I tried as well for the obvious reason. I'm pretty
sure someone told me (a) that doesn't work, and (b) the reason is xyzzy. But I
no long remember what the reason is, or even if I was told one.
The impression I have is that define_subst isn't a macro facility, even though
it looks a bit like one, and that may be why it can't do what you want to do
here.
paul
