Re: [PATCH 1/8] rs6000: More factoring of overload processing

[Segher Boessenkool <segher@kernel.crashing.org>]

On Fri, Jan 28, 2022 at 11:50:19AM -0600, Bill Schmidt wrote:
> This patch continues the refactoring started with r12-6014.

ab3f5b71dc6e

> +     and the generic code will issue the appropriate error message.  Skip
> +     this test for functions where we don't fully describe all the possible
> +     overload signatures in rs6000-overload.def (because they aren't relevant
> +     to the expansion here).  If we don't, we get confusing error messages.  */
> +  if (fcode != RS6000_OVLD_VEC_PROMOTE
> +      && fcode != RS6000_OVLD_VEC_SPLATS
> +      && fcode != RS6000_OVLD_VEC_EXTRACT
> +      && fcode != RS6000_OVLD_VEC_INSERT
> +      && fcode != RS6000_OVLD_VEC_STEP
> +      && (!VOID_TYPE_P (TREE_VALUE (fnargs)) || n < nargs))
>      return NULL;

Can you expand a bit on this, give an example for example?  It is very
hard to understand this code, the way it depends on code following many
lines later.

> +    default:
> +      ;

Don't.

I like this better than a BS break statement, but it is just as stupid.

If you need this, you don't want a switch statement, but some number of
if statements.  You cannot use a switch as a shorthand for this because
we have a silly warning and -Werror for this use.

You probably get easier to understand code that way, too, you can get
rid of the above (just do some early returns), etc.


Segher