Re: [patch 4/4 v4] Allow loop prefetch code to speculatively prefetch non constant steps

[Christian Borntraeger <borntraeger at de dot ibm dot com>]

Am Donnerstag 20 Mai 2010, 15:36:31 schrieb Christian Borntraeger:
> Am Donnerstag 20 Mai 2010 00:25:48 schrieb H.J. Lu:
> > This caused:
> > 
> > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44203
> 
> H.J.,
> 
> Can you verify the following patch?

Patch was successfully tested by H.J. (see bugzilla)

OK, to apply?

Christian


> 2010-05-20  Christian Borntraeger  <borntraeger@de.ibm.com>
> 
>         PR 44203
>         * gcc/tree-ssa-loop-prefetch.c: Fix logic for step calculation to
>         match the original (and intended) behaviour before r159557.  This
>         changeset changed a=a+b*c to a=(a+b)*b which was obviously wrong
>         in two ways. 
> 
> Index: gcc/tree-ssa-loop-prefetch.c
> ===================================================================
> *** gcc/tree-ssa-loop-prefetch.c.orig
> --- gcc/tree-ssa-loop-prefetch.c
> *************** idx_analyze_ref (tree base, tree *index,
> *** 425,449 ****
>         ibase = build_int_cst (TREE_TYPE (ibase), 0);
>       }
>   
> -   if (*ar_data->step == NULL_TREE)
> -     *ar_data->step = step;
> -   else
> -     *ar_data->step = fold_build2 (PLUS_EXPR, sizetype,
> - 				  fold_convert (sizetype, *ar_data->step),
> - 				  fold_convert (sizetype, step));
>     if (TREE_CODE (base) == ARRAY_REF)
>       {
>         stepsize = array_ref_element_size (base);
>         if (!cst_and_fits_in_hwi (stepsize))
>   	return false;
>         imult = int_cst_value (stepsize);
> ! 
> !       *ar_data->step = fold_build2 (MULT_EXPR, sizetype,
> ! 				    fold_convert (sizetype, *ar_data->step),
> ! 				    fold_convert (sizetype, step));
>         idelta *= imult;
>       }
>   
>     *ar_data->delta += idelta;
>     *index = ibase;
>   
> --- 425,448 ----
>         ibase = build_int_cst (TREE_TYPE (ibase), 0);
>       }
>   
>     if (TREE_CODE (base) == ARRAY_REF)
>       {
>         stepsize = array_ref_element_size (base);
>         if (!cst_and_fits_in_hwi (stepsize))
>   	return false;
>         imult = int_cst_value (stepsize);
> !       step = fold_build2 (MULT_EXPR, sizetype,
> ! 			  fold_convert (sizetype, step),
> ! 			  fold_convert (sizetype, stepsize));
>         idelta *= imult;
>       }
>   
> +   if (*ar_data->step == NULL_TREE)
> +     *ar_data->step = step;
> +   else
> +     *ar_data->step = fold_build2 (PLUS_EXPR, sizetype,
> + 				  fold_convert (sizetype, *ar_data->step),
> + 				  fold_convert (sizetype, step));
>     *ar_data->delta += idelta;
>     *index = ibase;