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

[Paulo César Pereira de Andrade]

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.

> -Paul
>

  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.

Thanks,
Paulo