[gcc r12-705] rs6000: Guard density_test only for vector version

[gcc r12-705] rs6000: Guard density_test only for vector version

[Kewen Lin]

https://gcc.gnu.org/g:1866182f6cf338880c68225d9de571b787b6abcd

commit r12-705-g1866182f6cf338880c68225d9de571b787b6abcd
Author: Kewen Lin <linkw@linux.ibm.com>
Date:   Mon May 10 23:01:15 2021 -0500

    rs6000: Guard density_test only for vector version
    
    This patch teaches rs6000_density_test to only care about the vector
    version cost calculation and early return when calculating the single
    scalar iteration cost.
    
    Bootstrapped/regtested on powerpc64le-linux-gnu P9.
    
    gcc/ChangeLog:
    
            * config/rs6000/rs6000.c (struct rs6000_cost_data): New member
            costing_for_scalar.
            (rs6000_density_test): Early return if costing_for_scalar is true.
            (rs6000_init_cost): Init costing_for_scalar of rs6000_cost_data.

Diff:
---
 gcc/config/rs6000/rs6000.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 1ef5149ad2e..d1b76f6ec41 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -5238,6 +5238,8 @@ typedef struct _rs6000_cost_data
   /* For each vectorized loop, this var holds TRUE iff a non-memory vector
      instruction is needed by the vectorization.  */
   bool vect_nonmem;
+  /* Indicates this is costing for the scalar version of a loop or block.  */
+  bool costing_for_scalar;
 } rs6000_cost_data;
 
 /* Test for likely overcommitment of vector hardware resources.  If a
@@ -5259,6 +5261,12 @@ rs6000_density_test (rs6000_cost_data *data)
   int vec_cost = data->cost[vect_body], not_vec_cost = 0;
   int i, density_pct;
 
+  /* This density test only cares about the cost of vector version of the
+     loop, so immediately return if we are passed costing for the scalar
+     version (namely computing single scalar iteration cost).  */
+  if (data->costing_for_scalar)
+    return;
+
   for (i = 0; i < nbbs; i++)
     {
       basic_block bb = bbs[i];
@@ -5296,7 +5304,7 @@ rs6000_density_test (rs6000_cost_data *data)
 /* Implement targetm.vectorize.init_cost.  */
 
 static void *
-rs6000_init_cost (struct loop *loop_info, bool)
+rs6000_init_cost (struct loop *loop_info, bool costing_for_scalar)
 {
   rs6000_cost_data *data = XNEW (struct _rs6000_cost_data);
   data->loop_info = loop_info;
@@ -5304,6 +5312,7 @@ rs6000_init_cost (struct loop *loop_info, bool)
   data->cost[vect_body]     = 0;
   data->cost[vect_epilogue] = 0;
   data->vect_nonmem = false;
+  data->costing_for_scalar = costing_for_scalar;
   return data;
 }