Re: [PATCH 15/21]middle-end: [RFC] conditionally support forcing final edge for debugging

[Richard Sandiford <richard.sandiford@arm.com>]

Tamar Christina <tamar.christina@arm.com> writes:
> Hi All,
>
> What do people think about having the ability to force only the latch connected
> exit as the exit as a param? I.e. what's in the patch but as a param.
>
> I found this useful when debugging large example failures as it tells me where
> I should be looking.  No hard requirement but just figured I'd ask if we should.

If it's useful for that, then perhaps it would be worth making it a
DEBUG_COUNTER instead of a --param, for easy bisection.

Thanks,
Richard

>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> 	* tree-vect-loop.cc (vec_init_loop_exit_info): Allow forcing of exit.
>
> --- inline copy of patch -- 
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index 27ab6abfa854f14f8a4cf3d9fcb1ac1c203a4198..d6b35372623e94e02965510ab557cb568c302ebe 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -964,6 +964,7 @@ vec_init_loop_exit_info (class loop *loop)
>    if (exits.length () == 1)
>      return exits[0];
>  
> +#if 0
>    /* If we have multiple exits we only support counting IV at the moment.  Analyze
>       all exits and return one */
>    class tree_niter_desc niter_desc;
> @@ -982,6 +983,16 @@ vec_init_loop_exit_info (class loop *loop)
>      }
>  
>    return candidate;
> +#else
> +  basic_block bb = ip_normal_pos (loop);
> +  if (!bb)
> +    return NULL;
> +
> +  edge exit = EDGE_SUCC (bb, 0);
> +  if (exit->dest == loop->latch)
> +    return EDGE_SUCC (bb, 1);
> +  return exit;
> +#endif
>  }
>  
>  /* Function bb_in_loop_p