On Wed, 31 Oct 2012, Jan Hubicka wrote:
> Hi,
> this patch changes finite_loop_p to use max_loop_iterations. Long time ago I
> made
> finite_loop_p as rip-off from the max_loop_iterations skipping parts that are
> not
> exactly related to the number of iteration estimates. It went out of date
> since then
> completelly missing the bounds derived from overflows and array bounds that
> are quite
> useful.
>
> So I guess these days it is better to simply implement it using
> max_loop_iterations,
> we do not save that much of effort and we can store the result.
>
> Bootstrapped/regtested x86_64, OK?
>
> Honza
>
> * tree-ssa-loop-niter.c (finite_loop_p): Reorg to use
> max_loop_iterations.
> Index: tree-ssa-loop-niter.c
> ===================================================================
> --- tree-ssa-loop-niter.c (revision 192991)
> +++ tree-ssa-loop-niter.c (working copy)
> @@ -1993,11 +1990,7 @@ find_loop_niter (struct loop *loop, edge
> bool
> finite_loop_p (struct loop *loop)
> {
> - unsigned i;
> - VEC (edge, heap) *exits;
> - edge ex;
> - struct tree_niter_desc desc;
> - bool finite = false;
> + double_int nit;
> int flags;
>
> if (flag_unsafe_loop_optimizations)
> @@ -2011,26 +2004,22 @@ finite_loop_p (struct loop *loop)
> return true;
> }
>
> - exits = get_loop_exit_edges (loop);
> - FOR_EACH_VEC_ELT (edge, exits, i, ex)
> + if (loop->any_upper_bound)
> {
> - if (!just_once_each_iteration_p (loop, ex->src))
> - continue;
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + fprintf (dump_file, "Found loop %i to be finite: upper bound is
> recorded.\n",
> + loop->num);
> + return true;
> + }
This looks redundant with ...
> - if (number_of_iterations_exit (loop, ex, &desc, false))
> - {
> - if (dump_file && (dump_flags & TDF_DETAILS))
> - {
> - fprintf (dump_file, "Found loop %i to be finite: iterating ",
> loop->num);
> - print_generic_expr (dump_file, desc.niter, TDF_SLIM);
> - fprintf (dump_file, " times\n");
> - }
> - finite = true;
> - break;
> - }
> + if (max_loop_iterations (loop, &nit))
> + {
... this. If you want to short-circuit max_loop_iterations ()
then why not
if (loop->any_upper_bound
|| max_loop_iterations (loop, &nit))
{
...
? The different dumping seems not a good reason to obfuscate it.
Richard.
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + fprintf (dump_file, "Found loop %i to be finite: upper bound found.\n",
> + loop->num);
> + return true;
> }
> - VEC_free (edge, heap, exits);
> - return finite;
> + return false;
> }
>
> /*
