Re: [065/nnn] poly_int: vect_nunits_for_cost

[Jeff Law]

On 10/23/2017 11:27 AM, Richard Sandiford wrote:
> This patch adds a function for getting the number of elements in
> a vector for cost purposes, which is always constant.  It makes
> it possible for a later patch to change GET_MODE_NUNITS and
> TYPE_VECTOR_SUBPARTS to a poly_int.
> 
> 
> 2017-10-23  Richard Sandiford  
>   Alan Hayward  
>   David Sherwood  
> 
> gcc/
>   * tree-vectorizer.h (vect_nunits_for_cost): New function.
>   * tree-vect-loop.c (vect_model_reduction_cost): Use it.
>   * tree-vect-slp.c (vect_analyze_slp_cost_1): Likewise.
>   (vect_analyze_slp_cost): Likewise.
>   * tree-vect-stmts.c (vect_model_store_cost): Likewise.
>   (vect_model_load_cost): Likewise.
OK.
jeff

[065/nnn] poly_int: vect_nunits_for_cost

[Richard Sandiford]

This patch adds a function for getting the number of elements in
a vector for cost purposes, which is always constant.  It makes
it possible for a later patch to change GET_MODE_NUNITS and
TYPE_VECTOR_SUBPARTS to a poly_int.


2017-10-23  Richard Sandiford  
Alan Hayward  
David Sherwood  

gcc/
* tree-vectorizer.h (vect_nunits_for_cost): New function.
* tree-vect-loop.c (vect_model_reduction_cost): Use it.
* tree-vect-slp.c (vect_analyze_slp_cost_1): Likewise.
(vect_analyze_slp_cost): Likewise.
* tree-vect-stmts.c (vect_model_store_cost): Likewise.
(vect_model_load_cost): Likewise.

Index: gcc/tree-vectorizer.h
===
--- gcc/tree-vectorizer.h   2017-10-23 17:22:26.575499779 +0100
+++ gcc/tree-vectorizer.h   2017-10-23 17:22:28.837953732 +0100
@@ -1154,6 +1154,16 @@ vect_vf_for_cost (loop_vec_info loop_vin
   return estimated_poly_value (LOOP_VINFO_VECT_FACTOR (loop_vinfo));
 }
 
+/* Estimate the number of elements in VEC_TYPE for costing purposes.
+   Pick a reasonable estimate if the exact number isn't known at
+   compile time.  */
+
+static inline unsigned int
+vect_nunits_for_cost (tree vec_type)
+{
+  return estimated_poly_value (TYPE_VECTOR_SUBPARTS (vec_type));
+}
+
 /* Return the size of the value accessed by unvectorized data reference DR.
This is only valid once STMT_VINFO_VECTYPE has been calculated for the
associated gimple statement, since that guarantees that DR accesses
Index: gcc/tree-vect-loop.c
===
--- gcc/tree-vect-loop.c2017-10-23 17:22:26.573499378 +0100
+++ gcc/tree-vect-loop.c2017-10-23 17:22:28.835953330 +0100
@@ -3844,13 +3844,15 @@ vect_model_reduction_cost (stmt_vec_info
}
   else if (STMT_VINFO_VEC_REDUCTION_TYPE (stmt_info) == COND_REDUCTION)
{
- unsigned nunits = TYPE_VECTOR_SUBPARTS (vectype);
+ unsigned estimated_nunits = vect_nunits_for_cost (vectype);
  /* Extraction of scalar elements.  */
- epilogue_cost += add_stmt_cost (target_cost_data, 2 * nunits,
+ epilogue_cost += add_stmt_cost (target_cost_data,
+ 2 * estimated_nunits,
  vec_to_scalar, stmt_info, 0,
  vect_epilogue);
  /* Scalar max reductions via COND_EXPR / MAX_EXPR.  */
- epilogue_cost += add_stmt_cost (target_cost_data, 2 * nunits - 3,
+ epilogue_cost += add_stmt_cost (target_cost_data,
+ 2 * estimated_nunits - 3,
  scalar_stmt, stmt_info, 0,
  vect_epilogue);
}
Index: gcc/tree-vect-slp.c
===
--- gcc/tree-vect-slp.c 2017-10-23 17:22:27.793744215 +0100
+++ gcc/tree-vect-slp.c 2017-10-23 17:22:28.836953531 +0100
@@ -1718,8 +1718,8 @@ vect_analyze_slp_cost_1 (slp_instance in
_perms);
  record_stmt_cost (body_cost_vec, n_perms, vec_perm,
stmt_info, 0, vect_body);
- unsigned nunits
-   = TYPE_VECTOR_SUBPARTS (STMT_VINFO_VECTYPE (stmt_info));
+ unsigned assumed_nunits
+   = vect_nunits_for_cost (STMT_VINFO_VECTYPE (stmt_info));
  /* And adjust the number of loads performed.  This handles
 redundancies as well as loads that are later dead.  */
  auto_sbitmap perm (GROUP_SIZE (stmt_info));
@@ -1730,7 +1730,7 @@ vect_analyze_slp_cost_1 (slp_instance in
  bool load_seen = false;
  for (i = 0; i < GROUP_SIZE (stmt_info); ++i)
{
- if (i % nunits == 0)
+ if (i % assumed_nunits == 0)
{
  if (load_seen)
ncopies_for_cost++;
@@ -1743,7 +1743,7 @@ vect_analyze_slp_cost_1 (slp_instance in
ncopies_for_cost++;
  gcc_assert (ncopies_for_cost
  <= (GROUP_SIZE (stmt_info) - GROUP_GAP (stmt_info)
- + nunits - 1) / nunits);
+ + assumed_nunits - 1) / assumed_nunits);
  poly_uint64 uf = SLP_INSTANCE_UNROLLING_FACTOR (instance);
  ncopies_for_cost *= estimated_poly_value (uf);
}
@@ -1856,9 +1856,9 @@ vect_analyze_slp_cost (slp_instance inst
 assumed_vf = vect_vf_for_cost (STMT_VINFO_LOOP_VINFO (stmt_info));
   else
 assumed_vf = 1;
-  unsigned nunits = TYPE_VECTOR_SUBPARTS (STMT_VINFO_VECTYPE (stmt_info));
   /* For reductions look at a reduction operand in case the reduction
  operation