diff options
author | Kewen Lin <linkw@linux.ibm.com> | 2021-09-21 22:25:54 -0500 |
---|---|---|
committer | Kewen Lin <linkw@linux.ibm.com> | 2021-09-21 23:47:33 -0500 |
commit | 144c4984655e9c687dfdda6b1ac39afea8b2a037 (patch) | |
tree | 9ab6e1e1de670ebdb32745ef841a6a93374578f6 /gcc | |
parent | 72394d38d929c72cad6cf706a0e790b5934f2bf1 (diff) | |
download | gcc-144c4984655e9c687dfdda6b1ac39afea8b2a037.zip gcc-144c4984655e9c687dfdda6b1ac39afea8b2a037.tar.gz gcc-144c4984655e9c687dfdda6b1ac39afea8b2a037.tar.bz2 |
rs6000: Parameterize some const values for density test
This patch follows the discussion here[1], where Segher suggested
parameterizing those exact magic constants for density heuristics,
to make it easier to tweak if need.
The change here should be "No Functional Change". But I verified
it with SPEC2017 at option sets O2-vect and Ofast-unroll on Power8,
the result is neutral as expected.
[1]https://gcc.gnu.org/pipermail/gcc-patches/2021-September/579121.html
gcc/ChangeLog:
* config/rs6000/rs6000.opt (rs6000-density-pct-threshold,
rs6000-density-size-threshold, rs6000-density-penalty,
rs6000-density-load-pct-threshold,
rs6000-density-load-num-threshold): New parameter.
* config/rs6000/rs6000.c (rs6000_density_test): Adjust with
corresponding parameters.
Diffstat (limited to 'gcc')
-rw-r--r-- | gcc/config/rs6000/rs6000.c | 22 | ||||
-rw-r--r-- | gcc/config/rs6000/rs6000.opt | 38 |
2 files changed, 45 insertions, 15 deletions
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c index 060f51a..ad86072 100644 --- a/gcc/config/rs6000/rs6000.c +++ b/gcc/config/rs6000/rs6000.c @@ -5289,9 +5289,6 @@ struct rs6000_cost_data static void rs6000_density_test (rs6000_cost_data *data) { - const int DENSITY_PCT_THRESHOLD = 85; - const int DENSITY_SIZE_THRESHOLD = 70; - const int DENSITY_PENALTY = 10; struct loop *loop = data->loop_info; basic_block *bbs = get_loop_body (loop); int nbbs = loop->num_nodes; @@ -5327,26 +5324,21 @@ rs6000_density_test (rs6000_cost_data *data) free (bbs); density_pct = (vec_cost * 100) / (vec_cost + not_vec_cost); - if (density_pct > DENSITY_PCT_THRESHOLD - && vec_cost + not_vec_cost > DENSITY_SIZE_THRESHOLD) + if (density_pct > rs6000_density_pct_threshold + && vec_cost + not_vec_cost > rs6000_density_size_threshold) { - data->cost[vect_body] = vec_cost * (100 + DENSITY_PENALTY) / 100; + data->cost[vect_body] = vec_cost * (100 + rs6000_density_penalty) / 100; if (dump_enabled_p ()) dump_printf_loc (MSG_NOTE, vect_location, "density %d%%, cost %d exceeds threshold, penalizing " - "loop body cost by %d%%\n", density_pct, - vec_cost + not_vec_cost, DENSITY_PENALTY); + "loop body cost by %u%%\n", density_pct, + vec_cost + not_vec_cost, rs6000_density_penalty); } /* Check whether we need to penalize the body cost to account for excess strided or elementwise loads. */ if (data->extra_ctor_cost > 0) { - /* Threshold for load stmts percentage in all vectorized stmts. */ - const int DENSITY_LOAD_PCT_THRESHOLD = 45; - /* Threshold for total number of load stmts. */ - const int DENSITY_LOAD_NUM_THRESHOLD = 20; - gcc_assert (data->nloads <= data->nstmts); unsigned int load_pct = (data->nloads * 100) / data->nstmts; @@ -5360,8 +5352,8 @@ rs6000_density_test (rs6000_cost_data *data) the loads. One typical case is the innermost loop of the hotspot of SPEC2017 503.bwaves_r without loop interchange. */ - if (data->nloads > DENSITY_LOAD_NUM_THRESHOLD - && load_pct > DENSITY_LOAD_PCT_THRESHOLD) + if (data->nloads > (unsigned int) rs6000_density_load_num_threshold + && load_pct > (unsigned int) rs6000_density_load_pct_threshold) { data->cost[vect_body] += data->extra_ctor_cost; if (dump_enabled_p ()) diff --git a/gcc/config/rs6000/rs6000.opt b/gcc/config/rs6000/rs6000.opt index c1cb9ab..9d7878f 100644 --- a/gcc/config/rs6000/rs6000.opt +++ b/gcc/config/rs6000/rs6000.opt @@ -639,3 +639,41 @@ Enable instructions that guard against return-oriented programming attacks. mprivileged Target Var(rs6000_privileged) Init(0) Generate code that will run in privileged state. + +-param=rs6000-density-pct-threshold= +Target Undocumented Joined UInteger Var(rs6000_density_pct_threshold) Init(85) IntegerRange(0, 100) Param +When costing for loop vectorization, we probably need to penalize the loop body +cost if the existing cost model may not adequately reflect delays from +unavailable vector resources. We collect the cost for vectorized statements +and non-vectorized statements separately, check the proportion of vec_cost to +total cost of vec_cost and non vec_cost, and penalize only if the proportion +exceeds the threshold specified by this parameter. The default value is 85. + +-param=rs6000-density-size-threshold= +Target Undocumented Joined UInteger Var(rs6000_density_size_threshold) Init(70) IntegerRange(0, 1000) Param +Like parameter rs6000-density-pct-threshold, we also check the total sum of +vec_cost and non vec_cost, and penalize only if the sum exceeds the threshold +specified by this parameter. The default value is 70. + +-param=rs6000-density-penalty= +Target Undocumented Joined UInteger Var(rs6000_density_penalty) Init(10) IntegerRange(0, 1000) Param +When both heuristics with rs6000-density-pct-threshold and +rs6000-density-size-threshold are satisfied, we decide to penalize the loop +body cost by the value which is specified by this parameter. The default +value is 10. + +-param=rs6000-density-load-pct-threshold= +Target Undocumented Joined UInteger Var(rs6000_density_load_pct_threshold) Init(45) IntegerRange(0, 100) Param +When costing for loop vectorization, we probably need to penalize the loop body +cost by accounting for excess strided or elementwise loads. We collect the +numbers for general statements and load statements according to the information +for statements to be vectorized, check the proportion of load statements, and +penalize only if the proportion exceeds the threshold specified by this +parameter. The default value is 45. + +-param=rs6000-density-load-num-threshold= +Target Undocumented Joined UInteger Var(rs6000_density_load_num_threshold) Init(20) IntegerRange(0, 1000) Param +Like parameter rs6000-density-load-pct-threshold, we also check if the total +number of load statements exceeds the threshold specified by this parameter, +and penalize only if it's satisfied. The default value is 20. + |