Re: Re: [PATCH 1/2] [RISC-V] disable shrink-wrap-separate if zcmp enabled.

["Fei Gao" <gaofei@eswincomputing.com>]

On 2023-05-08 17:20  Kito Cheng <kito.cheng@gmail.com> wrote:
>
>-msave-restore is a different story; it's only enabled when the user
>requests, but `-march` describes the capability of the target
>architecture, not specify the preference of performance or size, which
>should be determined by -O1~-O3/-Ofast or -Os/-Oz.
> 

I see and fully agree. 
I'll find a better way to resolve the conflict, 
My current idea is to diasble zcmp when shrink-wrap-separate is actually active. 

Thanks Kito and Andrew Pinski for your patience.

BR, 
Fei
>On Mon, May 8, 2023 at 4:54 PM Fei Gao <gaofei@eswincomputing.com> wrote:
>>
>> On 2023-05-08 16:05  Kito Cheng <kito.cheng@gmail.com> wrote:
>> >
>> >> > diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
>> >> > index 45a63cab9c9..629e5e45cac 100644
>> >> > --- a/gcc/config/riscv/riscv.cc
>> >> > +++ b/gcc/config/riscv/riscv.cc
>> >> > @@ -5729,7 +5729,8 @@ riscv_get_separate_components (void)
>> >> >
>> >> >    if (riscv_use_save_libcall (&cfun->machine->frame)
>> >> >        || cfun->machine->interrupt_handler_p
>> >> > -      || !cfun->machine->frame.gp_sp_offset.is_constant ())
>> >> > +      || !cfun->machine->frame.gp_sp_offset.is_constant ()
>> >> > +      || TARGET_ZCMP)
>> >> >      return components;
>> >>
>> >> I think this is a bad idea. I have a use case where we use the C
>> >> extensions but still compile for -O2 because we want the code to be
>> >> fast as possible but still having the savings of the C extensions.
>> >
>> >Yeah, agree, so I would prefer to drop this from the patch series.
>>
>> Zcmp is a little different here than C.
>> C extension is done fully in AS.  So  we have the code to be
>> fast as possible but still having the savings of the C extensions.
>>
>> Zcmp and shrink-wrap-separate are both done in prologue/epilogue pass
>> and you can only have one switch active to direct sregs save and restore.
>> In my understanding, zcmp push and pop insns seem to
>> be mutually exclusive in functionality to shrink-wrap-separate.
>> It's not expected to see zcmp insns at the begining/end of prologue/epilogue,
>> and also repeated store/load sregs in separate blocks.
>>
>> Same for save and restore, and i guess that's why we have
>> riscv_use_save_libcall (&cfun->machine->frame) check here.
>>
>> BR,
>> Fei
>>
>> >
>> >> Thanks,
>> >> Andrew Pinski