Hi, Gentle ping this:
https://gcc.gnu.org/pipermail/gcc-patches/2021-May/571258.html BR, Kewen on 2021/5/26 上午10:59, Kewen.Lin via Gcc-patches wrote: > Hi, > > This is the updated version of patch to deal with the bwaves_r > degradation due to vector construction fed by strided loads. > > As Richi's comments [1], this follows the similar idea to over > price the vector construction fed by VMAT_ELEMENTWISE or > VMAT_STRIDED_SLP. Instead of adding the extra cost on vector > construction costing immediately, it firstly records how many > loads and vectorized statements in the given loop, later in > rs6000_density_test (called by finish_cost) it computes the > load density ratio against all vectorized stmts, and check > with the corresponding thresholds DENSITY_LOAD_NUM_THRESHOLD > and DENSITY_LOAD_PCT_THRESHOLD, do the actual extra pricing > if both thresholds are exceeded. > > Note that this new load density heuristic check is based on > some fields in target cost which are updated as needed when > scanning each add_stmt_cost entry, it's independent of the > current function rs6000_density_test which requires to scan > non_vect stmts. Since it's checking the load stmts count > vs. all vectorized stmts, it's kind of density, so I put > it in function rs6000_density_test. With the same reason to > keep it independent, I didn't put it as an else arm of the > current existing density threshold check hunk or before this > hunk. > > In the investigation of -1.04% degradation from 526.blender_r > on Power8, I noticed that the extra penalized cost 320 on one > single vector construction with type V16QI is much exaggerated, > which makes the final body cost unreliable, so this patch adds > one maximum bound for the extra penalized cost for each vector > construction statement. > > Bootstrapped/regtested on powerpc64le-linux-gnu P9. > > Full SPEC2017 performance evaluation on Power8/Power9 with > option combinations: > * -O2 -ftree-vectorize {,-fvect-cost-model=very-cheap} {,-ffast-math} > * {-O3, -Ofast} {,-funroll-loops} > > bwaves_r degradations on P8/P9 have been fixed, nothing else > remarkable was observed. > > Is it ok for trunk? > > [1] https://gcc.gnu.org/pipermail/gcc-patches/2021-May/570076.html > > BR, > Kewen > ----- > gcc/ChangeLog: > > * config/rs6000/rs6000.c (struct rs6000_cost_data): New members > nstmts, nloads and extra_ctor_cost. > (rs6000_density_test): Add load density related heuristics and the > checks, do extra costing on vector construction statements if need. > (rs6000_init_cost): Init new members. > (rs6000_update_target_cost_per_stmt): New function. > (rs6000_add_stmt_cost): Factor vect_nonmem hunk out to function > rs6000_update_target_cost_per_stmt and call it. >