On Mon, 10 Sep 2012, William J. Schmidt wrote:
> Here's the revised patch with a param. Bootstrapped and tested in the
> same manner. Ok for trunk?
Ok.
Thanks,
Richard.
> Thanks,
> Bill
>
>
> 2012-08-10 Bill Schmidt <wschm...@linux.vnet.ibm.com>
>
> * doc/invoke.texi (max-slsr-cand-scan): New description.
> * gimple-ssa-strength-reduction.c (find_basis_for_candidate): Limit
> the time spent searching for a basis.
> * params.def (PARAM_MAX_SLSR_CANDIDATE_SCAN): New param.
>
>
> Index: gcc/doc/invoke.texi
> ===================================================================
> --- gcc/doc/invoke.texi (revision 191135)
> +++ gcc/doc/invoke.texi (working copy)
> @@ -9407,6 +9407,11 @@ having a regular register file and accurate regist
> See @file{haifa-sched.c} in the GCC sources for more details.
>
> The default choice depends on the target.
> +
> +@item max-slsr-cand-scan
> +Set the maximum number of existing candidates that will be considered when
> +seeking a basis for a new straight-line strength reduction candidate.
> +
> @end table
> @end table
>
> Index: gcc/gimple-ssa-strength-reduction.c
> ===================================================================
> --- gcc/gimple-ssa-strength-reduction.c (revision 191135)
> +++ gcc/gimple-ssa-strength-reduction.c (working copy)
> @@ -54,6 +54,7 @@ along with GCC; see the file COPYING3. If not see
> #include "domwalk.h"
> #include "pointer-set.h"
> #include "expmed.h"
> +#include "params.h"
>
> /* Information about a strength reduction candidate. Each statement
> in the candidate table represents an expression of one of the
> @@ -353,10 +354,14 @@ find_basis_for_candidate (slsr_cand_t c)
> cand_chain_t chain;
> slsr_cand_t basis = NULL;
>
> + // Limit potential of N^2 behavior for long candidate chains.
> + int iters = 0;
> + int max_iters = PARAM_VALUE (PARAM_MAX_SLSR_CANDIDATE_SCAN);
> +
> mapping_key.base_expr = c->base_expr;
> chain = (cand_chain_t) htab_find (base_cand_map, &mapping_key);
>
> - for (; chain; chain = chain->next)
> + for (; chain && iters < max_iters; chain = chain->next, ++iters)
> {
> slsr_cand_t one_basis = chain->cand;
>
> Index: gcc/params.def
> ===================================================================
> --- gcc/params.def (revision 191135)
> +++ gcc/params.def (working copy)
> @@ -973,6 +973,13 @@ DEFPARAM (PARAM_SCHED_PRESSURE_ALGORITHM,
> "Which -fsched-pressure algorithm to apply",
> 1, 1, 2)
>
> +/* Maximum length of candidate scans in straight-line strength reduction. */
> +DEFPARAM (PARAM_MAX_SLSR_CANDIDATE_SCAN,
> + "max-slsr-cand-scan",
> + "Maximum length of candidate scans for straight-line "
> + "strength reduction",
> + 50, 1, 999999)
> +
> /*
> Local variables:
> mode:c
>
>
>
--
Richard Biener <rguent...@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imend
