On Mon, 12 Mar 2018, Aaron Sawdey wrote:
> Looking at CPU2017 results for different reassociation widths, things
> have shifted since I last looked at this with CPU2006 in early gcc7
> timeframe. Best thing to do seems to be to set reassociation width to 1
> for all integer modes, which is what the attached patch does.
>
> I also tried setting width to 1 for float modes PLUS_EXPR as this patch
> did for aarch64 but this does not seem to be helpful for power8.
> https://gcc.gnu.org/ml/gcc-patches/2018-02/msg01271.html
>
>
> Results below are % performance improvement on power8 comparing trunk
> with the attached patch vs trunk with --param tree-reassoc-width=1 to
> disable parallel reassociation for everything (first column of results)
> and trunk unmodified (second column of results).
>
> CPU2017 component vs width=1 vs trunk
> 500.perlbench_r -0.36% -0.15%
> 502.gcc_r 0.06% 0.04%
> 505.mcf_r 0.32% 0.24%
> 520.omnetpp_r 0.57% -0.95%
> 523.xalancbmk_r 1.45% 1.04%
> 525.x264_r -0.05% 0.09%
> 531.deepsjeng_r 0.04% 0.09%
> 541.leela_r 0.10% 0.72%
> 548.exchange2_r 0.08% 0.73%
> 557.xz_r 0.09% 2.12%
> CPU2017 int geo mean 0.23% 0.40%
> 503.bwaves_r 0.00% 0.01%
> 507.cactuBSSN_r 0.05% -0.02%
> 508.namd_r 0.00% 0.00%
> 510.parest_r -0.01% 0.20%
> 511.povray_r 0.03% -0.24%
> 519.lbm_r -0.04% -0.16%
> 521.wrf_r -0.01% -0.56%
> 526.blender_r -0.82% -0.47%
> 527.cam4_r -0.18% 0.06%
> 538.imagick_r -0.02% 0.01%
> 544.nab_r 0.00% 0.23%
> 549.fotonik3d_r 0.24% 0.54%
> 554.roms_r -0.05% 0.03%
> CPU2017 fp geo mean -0.06% -0.03%
>
> Bottom line is net improvement for CPU2017 int compared with either
> current trunk, or disabling parallel reassociation. For CPU2017 fp,
> very small overall degradation.
>
> Currently doing regstrap on ppc64le, ok for trunk if results look good?
Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c (revision 258101)
+++ gcc/config/rs6000/rs6000.c (working copy)
@@ -10006,7 +10006,7 @@
if (VECTOR_MODE_P (mode))
return 4;
if (INTEGRAL_MODE_P (mode))
- return opc == MULT_EXPR ? 4 : 6;
+ return 1;
if (FLOAT_MODE_P (mode))
return 4;
break;
so the original widths were very large (IMHO), did you try reducing
width to, say, 2? In your numbers I see mostly noise but
2% regression for 557.xz_r and 1% for 523.xalancbmk_r. Maybe
POWER machines give very stable performance measurement results
but from my experience on x86_64 anything < 1% is just noise...
Richard.
> Thanks!
> Aaron
>
> 2018-03-12 Aaron Sawdey <acsaw...@linux.vnet.ibm.com>
>
> PR target/84743
> * config/rs6000/rs6000.c (rs6000_reassociation_width): Disable parallel
> reassociation for int modes.
>
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
