On Tue, 5 Jul 2016, Jan Hubicka wrote:
> Hi,
> this patch makes ivopts to use iv_can_overflow_p on its candidates. This helps
> to determine if candidate wraps in case it is not directly originating from IV
> variable (i.e. it is derived IV or artificial one). For those we can not use
> type information because we do now know if they are going to be computed each
> iteration. We can still use the iv_can_overflow_p analysis.
>
> I also wrote code that propagates overflow flag from original IVs to derived
> ones and it does improve some of real world benchmarks. This patch alone seems
> quite benchmark neutral but I would like to proceed in smaller steps.
>
> Bootstrapped/regtested x86_64-linux, OK?
>
> Honza
> * tree-scalar-evolution.c (iv_can_overflow_p): Export.
> * tree-scalar-evolution.h (iv_can_overflow_p): Declare.
> * tree-ssa-loop-ivopts.c (alloc_iv): Use it.
>
> Index: tree-scalar-evolution.c
> ===================================================================
> --- tree-scalar-evolution.c (revision 238012)
> +++ tree-scalar-evolution.c (working copy)
> @@ -3317,7 +3317,7 @@ scev_reset (void)
> use this test even for derived IVs not computed every iteration or
> hypotetical IVs to be inserted into code. */
>
> -static bool
> +bool
> iv_can_overflow_p (struct loop *loop, tree type, tree base, tree step)
> {
> widest_int nit;
> Index: tree-scalar-evolution.h
> ===================================================================
> --- tree-scalar-evolution.h (revision 238005)
> +++ tree-scalar-evolution.h (working copy)
> @@ -38,6 +38,7 @@ extern unsigned int scev_const_prop (voi
> extern bool expression_expensive_p (tree);
> extern bool simple_iv (struct loop *, struct loop *, tree, struct affine_iv
> *,
> bool);
> +extern bool iv_can_overflow_p (struct loop *, tree, tree, tree);
> extern tree compute_overall_effect_of_inner_loop (struct loop *, tree);
>
> /* Returns the basic block preceding LOOP, or the CFG entry block when
> Index: tree-ssa-loop-ivopts.c
> ===================================================================
> --- tree-ssa-loop-ivopts.c (revision 238005)
> +++ tree-ssa-loop-ivopts.c (working copy)
> @@ -1181,6 +1182,9 @@ alloc_iv (struct ivopts_data *data, tree
> iv->biv_p = false;
> iv->nonlin_use = NULL;
> iv->ssa_name = NULL_TREE;
> + if (!no_overflow && !iv_can_overflow_p (data->current_loop, TREE_TYPE
> (base),
> + base, step))
please put the && to the next line.
Ok with that change.
Richard.
> + no_overflow = true;
> iv->no_overflow = no_overflow;
> iv->have_address_use = false;
>
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
