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Re: [google 4-7] adjust single target i-call heursitic (issue7059044)
- From: Xinliang David Li <davidxl at google dot com>
- To: Rong Xu <xur at google dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, reply at codereview dot appspotmail dot com
- Date: Fri, 4 Jan 2013 19:42:03 -0800
- Subject: Re: [google 4-7] adjust single target i-call heursitic (issue7059044)
- References: <20130105012853.78D2E101023@rong.mtv.corp.google.com>
Need to document the parameter in doc/invoke.texi.
Ok with that change.
David
On Fri, Jan 4, 2013 at 5:28 PM, Rong Xu <xur@google.com> wrote:
> Hi,
>
> This patch adjusts the single target indirect call promotion heuristics.
> (1) it uses bb counts (bb_all), instead of count "all" which only counts
> the targets with the same modules as the caller.
> (becaue __gcov_indirect_call_callee is file scope statics).
> Using overall bb counts makes more sense here.
> (2) use a prameter option to control the threshold.
> (3) change the default threshold from 75% to 67%.
>
> Tested with google internal benchmarks and gcc regression test.
>
> Thanks,
>
> -Rong
>
> 2013-01-04 Rong Xu <xur@google.com>
>
> * gcc/value-prof.c (gimple_ic_transform_single_targ):
> adjust the single_target i_call promotion heuristics.
> * gcc/params.def.h: Add new parameter options.
> Index: gcc/value-prof.c
> ===================================================================
> --- gcc/value-prof.c (revision 194916)
> +++ gcc/value-prof.c (working copy)
> @@ -1491,16 +1491,20 @@ gimple_ic_transform_single_targ (gimple stmt, hist
> gcov_type prob;
> gimple modify;
> struct cgraph_node *direct_call;
> + int perc_threshold, count_threshold;
>
> val = histogram->hvalue.counters [0];
> count = histogram->hvalue.counters [1];
> all = histogram->hvalue.counters [2];
> gimple_remove_histogram_value (cfun, stmt, histogram);
> + bb_all = gimple_bb (stmt)->count;
>
> - if (4 * count <= 3 * all)
> + perc_threshold = PARAM_VALUE (PARAM_SINGLE_ICALL_PROMOTE_PERCENT_THRESHOLD);
> + count_threshold = PARAM_VALUE (PARAM_SINGLE_ICALL_PROMOTE_COUNT_THRESHOLD);
> +
> + if (100 * count < bb_all * perc_threshold || count < count_threshold)
> return false;
>
> - bb_all = gimple_bb (stmt)->count;
> /* The order of CHECK_COUNTER calls is important -
> since check_counter can correct the third parameter
> and we want to make count <= all <= bb_all. */
> @@ -1508,6 +1512,7 @@ gimple_ic_transform_single_targ (gimple stmt, hist
> || check_counter (stmt, "ic", &count, &all, all))
> return false;
>
> + all = bb_all;
> if (all > 0)
> prob = (count * REG_BR_PROB_BASE + all / 2) / all;
> else
> Index: gcc/params.def
> ===================================================================
> --- gcc/params.def (revision 194916)
> +++ gcc/params.def (working copy)
> @@ -907,6 +907,7 @@ DEFPARAM (PARAM_LOOP_INVARIANT_MAX_BBS_IN_LOOP,
> /* Promote indirect call to conditional direct call only
> when the percentage of the target count over the total
> indirect call count is no smaller than the threshold. */
> +/* For multi-targ indirect_call. */
> DEFPARAM (PARAM_ICALL_PROMOTE_PERCENT_THRESHOLD,
> "icall-promote-target-percent-threshold",
> "percentage threshold for direct call promotion"
> @@ -919,6 +920,19 @@ DEFPARAM (PARAM_ICALL_PROMOTE_COUNT_THRESHOLD,
> " of a callee target",
> 1, 0, 0)
>
> +/* For single-targ indirect_call. */
> +DEFPARAM (PARAM_SINGLE_ICALL_PROMOTE_PERCENT_THRESHOLD,
> + "single_icall-promote-target-percent-threshold",
> + "percentage threshold for direct call promotion"
> + " of a callee target",
> + 67, 0, 100)
> +
> +DEFPARAM (PARAM_SINGLE_ICALL_PROMOTE_COUNT_THRESHOLD,
> + "single_icall-promote-target_count-threshold",
> + "call count threshold for direct call promotion"
> + " of a callee target",
> + 1, 0, 0)
> +
> /* 0: do not always inline icall target:
> other value: always inline icall target when call count
> exceeds this value.
>
> --
> This patch is available for review at http://codereview.appspot.com/7059044