On 12/19/22 15:59, 钟居哲 wrote:
>> ISTM that if you want to run before sched2, then
you'd need to introduce dependencies between the vsetvl instrutions and
the vector instructions that utilize those settings?
Yes, I want to run before sched2 so that we could have the chance to do the
instruction scheduling before sched2. I already introduce dependencies in
vector instructions so that it won't produce any issues.
Ah good that you're adding the necessary dependencies. We'd been
talking a bit about this internally. The hope is that on an OOO machine
the vsetvl will be able to issue/execute relatively early, but on an
in-order machine the ability to schedule the vsetvl could become
significantly more important.
>> It'd probably be better to move this into rtl.cc with a prototype in
rtl.h rather than have duplicate definitions in gcse.c and the RISC-V
backend. I'm not even entirely sure why we really need it here.
Maybe we do that when GCC14 is open?
If we're just making a routine external that previously had static scope
then we can still do that IMHO. Such a change won't affect code
generation so it should be extremely safe. I'm happy to engage with
Richi and Jakub to get their sign-off on such a change.
Jeff
