[gcc r12-3103] Disable slp in loop vectorizer when cost model is very-cheap.

[gcc r12-3103] Disable slp in loop vectorizer when cost model is very-cheap.

[hongtao Liu]

https://gcc.gnu.org/g:819b7c3a339e3bdaf85cd55954c5536bd98aae09

commit r12-3103-g819b7c3a339e3bdaf85cd55954c5536bd98aae09
Author: liuhongt <hongtao.liu@intel.com>
Date:   Wed Aug 4 16:39:31 2021 +0800

    Disable slp in loop vectorizer when cost model is very-cheap.
    
    Performance impact for the commit with option:
    -march=x86-64 -O2 -ftree-vectorize -fvect-cost-model=very-cheap
    
    SPEC2017 fprate
    503.bwaves_r        BuildSame
    507.cactuBSSN_r         -0.04
    508.namd_r               0.14
    510.parest_r            -0.54
    511.povray_r             0.10
    519.lbm_r           BuildSame
    521.wrf_r                0.64
    526.blender_r           -0.32
    527.cam4_r               0.17
    538.imagick_r            0.09
    544.nab_r           BuildSame
    549.fotonik3d_r     BuildSame
    554.roms_r          BuildSame
    997.specrand_fr         -0.09
    Geometric mean:  0.02
    
    SPEC2017 intrate
    500.perlbench_r          0.26
    502.gcc_r                0.21
    505.mcf_r               -0.09
    520.omnetpp_r       BuildSame
    523.xalancbmk_r     BuildSame
    525.x264_r              -0.41
    531.deepsjeng_r     BuildSame
    541.leela_r              0.13
    548.exchange2_r     BuildSame
    557.xz_r            BuildSame
    999.specrand_ir     BuildSame
    Geometric mean:  0.02
    
    EEMBC: no regression, only improvement or build the same, the below is
    improved benchmarks.
    
    mp2decoddata1       7.59
    mp2decoddata2       31.80
    mp2decoddata3       12.15
    mp2decoddata4       11.16
    mp2decoddata5       11.19
    mp2decoddata1       7.06
    mp2decoddata2       24.12
    mp2decoddata3       10.83
    mp2decoddata4       10.04
    mp2decoddata5       10.07
    
    gcc/ChangeLog:
    
            PR tree-optimization/100089
            * tree-vectorizer.c (try_vectorize_loop_1): Disable slp in
            loop vectorizer when cost model is very-cheap.

Diff:
---
 gcc/tree-vectorizer.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/gcc/tree-vectorizer.c b/gcc/tree-vectorizer.c
index b9709a613d5..813f4683d1e 100644
--- a/gcc/tree-vectorizer.c
+++ b/gcc/tree-vectorizer.c
@@ -1033,7 +1033,10 @@ try_vectorize_loop_1 (hash_table<simduid_to_vf> *&simduid_to_vf_htab,
 	 only non-if-converted parts took part in BB vectorization.  */
       if (flag_tree_slp_vectorize != 0
 	  && loop_vectorized_call
-	  && ! loop->inner)
+	  && ! loop->inner
+	  /* This would purely be a workaround and should be removed
+	     once PR100089 is fixed.  */
+	  && flag_vect_cost_model != VECT_COST_MODEL_VERY_CHEAP)
 	{
 	  basic_block bb = loop->header;
 	  bool require_loop_vectorize = false;