[PATCH] vect: Keep scalar costs around longer

Richard Sandiford richard.sandiford@arm.com
Mon Nov 8 10:46:29 GMT 2021


The scalar costs for a loop are fleeting, with only the final
single_scalar_iteration_cost being kept for later comparison.
This patch replaces single_scalar_iteration_cost with the cost
structure, so that (with later patches) it's possible for targets
to examine other target-specific cost properties as well.  This will
be done by passing the scalar costs to hooks where appropriate;
targets shouldn't try to read the information directly from
loop_vec_infos.

Tested on aarch64-linux-gnu and x86_64-linux-gnu.  OK to install?

Richard


gcc/
	* tree-vectorizer.h (_loop_vec_info::scalar_costs): New member
	variable.
	(_loop_vec_info::single_scalar_iteration_cost): Delete.
	(LOOP_VINFO_SINGLE_SCALAR_ITERATION_COST): Delete.
	(vector_costs::total_cost): New function.
	* tree-vect-loop.c (_loop_vec_info::_loop_vec_info): Update
	after above changes.
	(_loop_vec_info::~_loop_vec_info): Delete scalar_costs.
	(vect_compute_single_scalar_iteration_cost): Store the costs
	in loop_vinfo->scalar_costs.
	(vect_estimate_min_profitable_iters): Get the scalar cost from
	loop_vinfo->scalar_costs.
---
 gcc/tree-vect-loop.c  | 17 ++++++-----------
 gcc/tree-vectorizer.h | 17 +++++++++++++----
 2 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index c9ee2e15e35..887275a5071 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -822,6 +822,7 @@ _loop_vec_info::_loop_vec_info (class loop *loop_in, vec_info_shared *shared)
     num_iters_unchanged (NULL_TREE),
     num_iters_assumptions (NULL_TREE),
     vector_costs (nullptr),
+    scalar_costs (nullptr),
     th (0),
     versioning_threshold (0),
     vectorization_factor (0),
@@ -839,7 +840,6 @@ _loop_vec_info::_loop_vec_info (class loop *loop_in, vec_info_shared *shared)
     ivexpr_map (NULL),
     scan_map (NULL),
     slp_unrolling_factor (1),
-    single_scalar_iteration_cost (0),
     inner_loop_cost_factor (param_vect_inner_loop_cost_factor),
     vectorizable (false),
     can_use_partial_vectors_p (param_vect_partial_vector_usage != 0),
@@ -931,6 +931,7 @@ _loop_vec_info::~_loop_vec_info ()
   delete ivexpr_map;
   delete scan_map;
   epilogue_vinfos.release ();
+  delete scalar_costs;
   delete vector_costs;
 
   /* When we release an epiloge vinfo that we do not intend to use
@@ -1292,20 +1293,15 @@ vect_compute_single_scalar_iteration_cost (loop_vec_info loop_vinfo)
     }
 
   /* Now accumulate cost.  */
-  vector_costs *target_cost_data = init_cost (loop_vinfo, true);
+  loop_vinfo->scalar_costs = init_cost (loop_vinfo, true);
   stmt_info_for_cost *si;
   int j;
   FOR_EACH_VEC_ELT (LOOP_VINFO_SCALAR_ITERATION_COST (loop_vinfo),
 		    j, si)
-    (void) add_stmt_cost (target_cost_data, si->count,
+    (void) add_stmt_cost (loop_vinfo->scalar_costs, si->count,
 			  si->kind, si->stmt_info, si->vectype,
 			  si->misalign, si->where);
-  unsigned prologue_cost = 0, body_cost = 0, epilogue_cost = 0;
-  finish_cost (target_cost_data, &prologue_cost, &body_cost,
-	       &epilogue_cost);
-  delete target_cost_data;
-  LOOP_VINFO_SINGLE_SCALAR_ITERATION_COST (loop_vinfo)
-    = prologue_cost + body_cost + epilogue_cost;
+  loop_vinfo->scalar_costs->finish_cost ();
 }
 
 
@@ -3868,8 +3864,7 @@ vect_estimate_min_profitable_iters (loop_vec_info loop_vinfo,
      TODO: Consider assigning different costs to different scalar
      statements.  */
 
-  scalar_single_iter_cost
-    = LOOP_VINFO_SINGLE_SCALAR_ITERATION_COST (loop_vinfo);
+  scalar_single_iter_cost = loop_vinfo->scalar_costs->total_cost ();
 
   /* Add additional cost for the peeled instructions in prologue and epilogue
      loop.  (For fully-masked loops there will be no peeling.)
diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index 0e3aad590e8..8dba3a34aa9 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -590,6 +590,9 @@ public:
   /* The cost of the vector code.  */
   class vector_costs *vector_costs;
 
+  /* The cost of the scalar code.  */
+  class vector_costs *scalar_costs;
+
   /* Threshold of number of iterations below which vectorization will not be
      performed. It is calculated from MIN_PROFITABLE_ITERS and
      param_min_vect_loop_bound.  */
@@ -721,9 +724,6 @@ public:
      applied to the loop, i.e., no unrolling is needed, this is 1.  */
   poly_uint64 slp_unrolling_factor;
 
-  /* Cost of a single scalar iteration.  */
-  int single_scalar_iteration_cost;
-
   /* The factor used to over weight those statements in an inner loop
      relative to the loop being vectorized.  */
   unsigned int inner_loop_cost_factor;
@@ -843,7 +843,6 @@ public:
 #define LOOP_VINFO_SCALAR_LOOP_SCALING(L)  (L)->scalar_loop_scaling
 #define LOOP_VINFO_HAS_MASK_STORE(L)       (L)->has_mask_store
 #define LOOP_VINFO_SCALAR_ITERATION_COST(L) (L)->scalar_cost_vec
-#define LOOP_VINFO_SINGLE_SCALAR_ITERATION_COST(L) (L)->single_scalar_iteration_cost
 #define LOOP_VINFO_ORIG_LOOP_INFO(L)       (L)->orig_loop_info
 #define LOOP_VINFO_SIMD_IF_COND(L)         (L)->simd_if_cond
 #define LOOP_VINFO_INNER_LOOP_COST_FACTOR(L) (L)->inner_loop_cost_factor
@@ -1438,6 +1437,7 @@ public:
   unsigned int body_cost () const;
   unsigned int epilogue_cost () const;
   unsigned int outside_cost () const;
+  unsigned int total_cost () const;
 
 protected:
   unsigned int record_stmt_cost (stmt_vec_info, vect_cost_model_location,
@@ -1508,6 +1508,15 @@ vector_costs::outside_cost () const
   return prologue_cost () + epilogue_cost ();
 }
 
+/* Return the cost of the prologue, body and epilogue code
+   (in abstract units).  */
+
+inline unsigned int
+vector_costs::total_cost () const
+{
+  return body_cost () + outside_cost ();
+}
+
 #define VECT_MAX_COST 1000
 
 /* The maximum number of intermediate steps required in multi-step type
-- 
2.25.1



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