aarch64: Detect scalar extending loads

If the scalar code does an integer load followed by an integer
extension, we've tended to cost that as two separate operations,
even though the extension is probably going to be free in practice.
This patch treats the extension as having zero cost, like we already
do for extending SVE loads.

Like with previous patches, this one only becomes active if
a CPU selects use_new_vector_costs.  It should therefore have
a very low impact on other CPUs.

gcc/
	* config/aarch64/aarch64.c (aarch64_detect_scalar_stmt_subtype):
	New function.
	(aarch64_add_stmt_cost): Call it.

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 63750e3..e2d92f0 100644 (file)
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -14493,6 +14493,23 @@ aarch64_sve_in_loop_reduction_latency (vec_info *vinfo,
 }
 
 /* STMT_COST is the cost calculated by aarch64_builtin_vectorization_cost
+   for STMT_INFO, which has cost kind KIND.  If this is a scalar operation,
+   try to subdivide the target-independent categorization provided by KIND
+   to get a more accurate cost.  */
+static unsigned int
+aarch64_detect_scalar_stmt_subtype (vec_info *vinfo, vect_cost_for_stmt kind,
+                                   stmt_vec_info stmt_info,
+                                   unsigned int stmt_cost)
+{
+  /* Detect an extension of a loaded value.  In general, we'll be able to fuse
+     the extension with the load.  */
+  if (kind == scalar_stmt && aarch64_extending_load_p (vinfo, stmt_info))
+    return 0;
+
+  return stmt_cost;
+}
+
+/* STMT_COST is the cost calculated by aarch64_builtin_vectorization_cost
    for the vectorized form of STMT_INFO, which has cost kind KIND and which
    when vectorized would operate on vector type VECTYPE.  Try to subdivide
    the target-independent categorization provided by KIND to get a more
@@ -14702,10 +14719,16 @@ aarch64_add_stmt_cost (class vec_info *vinfo, void *data, int count,
 
       /* Try to get a more accurate cost by looking at STMT_INFO instead
         of just looking at KIND.  */
-      if (stmt_info && vectype && aarch64_use_new_vector_costs_p ())
-       stmt_cost = aarch64_detect_vector_stmt_subtype (vinfo, kind,
-                                                       stmt_info, vectype,
-                                                       where, stmt_cost);
+      if (stmt_info && aarch64_use_new_vector_costs_p ())
+       {
+         stmt_cost = aarch64_detect_scalar_stmt_subtype
+           (vinfo, kind, stmt_info, stmt_cost);
+
+         if (vectype && costs->vec_flags)
+           stmt_cost = aarch64_detect_vector_stmt_subtype (vinfo, kind,
+                                                           stmt_info, vectype,
+                                                           where, stmt_cost);
+       }
 
       /* Do any SVE-specific adjustments to the cost.  */
       if (stmt_info && vectype && aarch64_sve_mode_p (TYPE_MODE (vectype)))