On Wed, 8 Jun 2016, Jan Hubicka wrote:
> Hi,
> I think 20 insns to copy for loop header is way too much. The constant came
> from jump.c that was operating with quite different IL and compiler.
> This patch adds --param for it so we can fine tune it for new millenia.
>
> Bootstrapped/regtested x86_64-linux, OK?
Ok.
Thanks
Richard.
> Honza
>
> * invoke.texi (max-loop-headers-insns): Document.
> * params.def (PARAM_MAX_LOOP_HEADER_INSNS): New.
> * tree-ssa-loop-ch.c (should_duplicate_loop_header_p): Update comment.
> (ch_base::copy_headers): Use PARAM_MAX_LOOP_HEADER_INSNS.
>
> Index: doc/invoke.texi
> ===================================================================
> --- doc/invoke.texi (revision 237184)
> +++ doc/invoke.texi (working copy)
> @@ -9066,6 +9066,9 @@ The maximum number of insns of an unswit
> @item max-unswitch-level
> The maximum number of branches unswitched in a single loop.
>
> +@item max-loop-headers-insns
> +The maximum number of insns in loop header duplicated by copy loop headers
> pass.
> +
> @item lim-expensive
> The minimum cost of an expensive expression in the loop invariant motion.
>
> Index: params.def
> ===================================================================
> --- params.def (revision 237184)
> +++ params.def (working copy)
> @@ -344,6 +344,13 @@ DEFPARAM(PARAM_MAX_UNSWITCH_LEVEL,
> "The maximum number of unswitchings in a single loop.",
> 3, 0, 0)
>
> +/* The maximum number of insns in loop header duplicated by copy loop headers
> + pass. */
> +DEFPARAM(PARAM_MAX_LOOP_HEADER_INSNS,
> + "max-loop-header-insns",
> + "The maximum number of insns in loop header duplicated by copy loop
> headers pass.",
> + 20, 0, 0)
> +
> /* The maximum number of iterations of a loop the brute force algorithm
> for analysis of # of iterations of the loop tries to evaluate. */
> DEFPARAM(PARAM_MAX_ITERATIONS_TO_TRACK,
> Index: tree-ssa-loop-ch.c
> ===================================================================
> --- tree-ssa-loop-ch.c (revision 237184)
> +++ tree-ssa-loop-ch.c (working copy)
> @@ -33,6 +33,7 @@ along with GCC; see the file COPYING3.
> #include "tree-inline.h"
> #include "tree-ssa-scopedtables.h"
> #include "tree-ssa-threadedge.h"
> +#include "params.h"
>
> /* Duplicates headers of loops if they are small enough, so that the
> statements
> in the loop body are always executed when the loop is entered. This
> @@ -106,8 +107,7 @@ should_duplicate_loop_header_p (basic_bl
> return false;
> }
>
> - /* Approximately copy the conditions that used to be used in jump.c --
> - at most 20 insns and no calls. */
> + /* Count number of instructions and punt on calls. */
> for (bsi = gsi_start_bb (header); !gsi_end_p (bsi); gsi_next (&bsi))
> {
> last = gsi_stmt (bsi);
> @@ -290,8 +290,8 @@ ch_base::copy_headers (function *fun)
>
> FOR_EACH_LOOP (loop, 0)
> {
> - /* Copy at most 20 insns. */
> - int limit = 20;
> + int ninsns = PARAM_VALUE (PARAM_MAX_LOOP_HEADER_INSNS);
> + int limit = ninsns;
> if (dump_file && (dump_flags & TDF_DETAILS))
> fprintf (dump_file,
> "Analyzing loop %i\n", loop->num);
> @@ -333,7 +333,8 @@ ch_base::copy_headers (function *fun)
> fprintf (dump_file,
> "Duplicating header of the loop %d up to edge %d->%d,"
> " %i insns.\n",
> - loop->num, exit->src->index, exit->dest->index, 20 - limit);
> + loop->num, exit->src->index, exit->dest->index,
> + ninsns - limit);
>
> /* Ensure that the header will have just the latch as a predecessor
> inside the loop. */
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
