[Bug target/63679] [5.0 Regression][AArch64] Failure to constant fold.

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63679

--- Comment #18 from rguenther at suse dot de <rguenther at suse dot de> ---
On Mon, 24 Nov 2014, belagod at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63679
> 
> --- Comment #17 from Tejas Belagod <belagod at gcc dot gnu.org> ---
> > -
> >  	    /* Do a block move either if the size is so small as to make
> >  	       each individual move a sub-unit move on average, or if it
> > -	       is so large as to make individual moves inefficient.  */
> > +	       is so large as to make individual moves inefficient.  Reuse
> > +	       the same costs logic as we use in the SRA passes.  */
> > +            unsigned max_scalarization_size
> > +	      = optimize_function_for_size_p (cfun)
> > +	        ? PARAM_VALUE (PARAM_SRA_MAX_SCALARIZATION_SIZE_SIZE)
> > +		: PARAM_VALUE (PARAM_SRA_MAX_SCALARIZATION_SIZE_SPEED);
> > +
> >  	    if (size > 0
> >  		&& num_nonzero_elements > 1
> >  		&& (size < num_nonzero_elements
> > -		    || !can_move_by_pieces (size, align)))
> > +		    || size > max_scalarization_size))
> >  	      {
> >  		if (notify_temp_creation)
> >  		  return GS_ERROR;
> 
> I think both move_by_pieces and SRA can co-exist here:
> 
> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
> index 8e3dd83..be51ce7 100644
> --- a/gcc/gimplify.c
> +++ b/gcc/gimplify.c
> @@ -70,6 +70,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "omp-low.h"
>  #include "gimple-low.h"
>  #include "cilk.h"
> +#include "params.h"
> 
>  #include "langhooks-def.h"    /* FIXME: for lhd_set_decl_assembler_name */
>  #include "tree-pass.h"        /* FIXME: only for PROP_gimple_any */
> @@ -3895,7 +3896,6 @@ gimplify_init_constructor (tree *expr_p, gimple_seq
> *pre_p, gimple_seq *post_p,
>                        DECL_ATTRIBUTES (current_function_decl))))
>        {
>          HOST_WIDE_INT size = int_size_in_bytes (type);
>         unsigned int align;
> 
>          /* ??? We can still get unbounded array types, at least
>             from the C++ front end.  This seems wrong, but attempt
> @@ -3907,20 +3907,19 @@ gimplify_init_constructor (tree *expr_p, gimple_seq
> *pre_p, gimple_seq *post_p,
>            TREE_TYPE (ctor) = type = TREE_TYPE (object);
>            }
> 
>         /* Find the maximum alignment we can assume for the object.  */
>         /* ??? Make use of DECL_OFFSET_ALIGN.  */
>         if (DECL_P (object))
>           align = DECL_ALIGN (object);
>         else
>           align = TYPE_ALIGN (type);
> 
>          /* Do a block move either if the size is so small as to make
>             each individual move a sub-unit move on average, or if it
> -           is so large as to make individual moves inefficient.  */
> +           is so large as to make individual moves inefficient.  Reuse
> +           the same costs logic as we use in the SRA passes.  */
> +            unsigned max_scalarization_size
> +          = optimize_function_for_size_p (cfun)
> +            ? PARAM_VALUE (PARAM_SRA_MAX_SCALARIZATION_SIZE_SIZE)
> +        : PARAM_VALUE (PARAM_SRA_MAX_SCALARIZATION_SIZE_SPEED);
> +
>          if (size > 0
>          && num_nonzero_elements > 1
>          && (size < num_nonzero_elements
> +            || size > max_scalarization_size
>             || !can_move_by_pieces (size, align))
>            {
>          if (notify_temp_creation)
>            return GS_ERROR;
> 
> If it isn't profitable to do an SRA, we can fall-back to the backend hook to
> move it by pieces. This way, I think we'll have move opportunity for
> optimization.

But that wouldn't fix the AARCH64 case as the backend says "no" here
anyway?