Re: [PATCH] ppc: Add optimization to generate endian-swapping load opcodes

[Paul Cercueil]

Le ven., août 12 2022 at 09:40:30 -0300, Paulo César Pereira de 
Andrade <paulo.cesar.pereira.de.andrade@gmail.com> a écrit :
> Em sex., 12 de ago. de 2022 às 09:26, Paul Cercueil
> <paul@crapouillou.net> escreveu:
> >  [...]
> >
> >  >>  Actually that case would be fine. It's for the case where the 
> > LABEL
> >  >> is
> >  >>  between the ldr_ui and the bswapr_ui. I do check the previous
> >  >> opcode,
> >  >>  because that's where the jit_flag_patch seems to be.
> >  >
> >  >   I see. The logic is just checking if the previous node is a 
> > label
> >  > or an
> >  > epilog implicit patch.
> >
> >  Actually it looks like the detection code is broken. With the 
> > example
> >  code of my previous email, if I add a jit_label() between the
> >  jit_ldr_ui() and the jit_bswapr_ui(), it still converts to the LWBRX
> >  opcode and Lightning eventually fails an assert() in jit_address().
>
>   It should not fail if you use jit_indirect() instead of 
> jit_label(). Using
> jit_label() is subject to optimization, if there is no jump to it. The
> assertion is because the label is not used.

I used jit_address() though, is that not considered as using the label?

>   I will apply the patch, and possibly add a small further patch with
> a comment about moving it to another place if a backend specific
> optimization pass is implemented.

Great, thanks!

Cheers,
-Paul