[PATCH] Compute and print statistics about match.pd generated code

[Richard Biener <rguenther at suse dot de>]

This calculates size estimates for the decision (sub-)trees and dumps
info to stderr.  My dev tree says:

build/genmatch --gimple /space/rguenther/tramp3d/trunk/gcc/match.pd \
    > tmp-gimple-match.c
GIMPLE decision tree has 696 leafs, maximum depth 10 and a total number of 
2786 nodes
build/genmatch --generic /space/rguenther/tramp3d/trunk/gcc/match.pd \
    > tmp-generic-match.c
GENERIC decision tree has 696 leafs, maximum depth 10 and a total number 
of 2786 nodes

the idea is to play with the simple idea of splitting the simplify
functions into equally sized pieces with a toplevel

 switch (code)
 {
 case PLUS_EXPR:
 case MINUS_EXPR:
   return do_part1 ();
 case ...

this should be relatively straight-forward and eventually helps
compile-time enough while we work on reducing the amount of
generated code (that hit some obstackles I have to think about
some more).  Eventually we can split this into multiple files
as well.

Bootstrapping on x86_64-unknown-linux-gnu.

Richard.

2015-07-24  Richard Biener  <rguenther@suse.de>

	* genmatch.c (struct dt_node): Add statistic fields.
	(dt_node::analyze): New method.
	(decision_tree::gen_gimple): Call analyze on the root node
	and print statistics to stderr.
	(decision_tree::gen_generic): Likewise.

Index: gcc/genmatch.c
===================================================================
--- gcc/genmatch.c	(revision 226140)
+++ gcc/genmatch.c	(working copy)
@@ -1212,6 +1225,11 @@ struct dt_node
   unsigned level;
   vec<dt_node *> kids;
 
+  /* Statistics.  */
+  unsigned num_leafs;
+  unsigned total_size;
+  unsigned max_level;
+
   dt_node (enum dt_type type_): type (type_), level (0), kids (vNULL) {}
 
   dt_node *append_node (dt_node *);
@@ -1226,6 +1244,8 @@ struct dt_node
   void gen_kids_1 (FILE *, int, bool,
 		   vec<dt_operand *>, vec<dt_operand *>, vec<dt_operand *>,
 		   vec<dt_operand *>, vec<dt_operand *>, vec<dt_node *>);
+
+  void analyze ();
 };
 
 /* Generic decision tree node used for DT_OPERAND and DT_MATCH.  */
@@ -1428,6 +1448,30 @@ dt_node::append_simplify (simplify *s, u
   return append_node (n);
 }
 
+/* Analyze the node and its children.  */
+
+void
+dt_node::analyze ()
+{
+  num_leafs = 0;
+  total_size = 1;
+  max_level = level;
+
+  if (type == DT_SIMPLIFY)
+    {
+      num_leafs = 1;
+      return;
+    }
+
+  for (unsigned i = 0; i < kids.length (); ++i)
+    {
+      kids[i]->analyze ();
+      num_leafs += kids[i]->num_leafs;
+      total_size += kids[i]->total_size;
+      max_level = MAX (max_level, kids[i]->max_level);
+    }
+}
+
 /* Insert O into the decision tree and return the decision tree node found
    or created.  */
 
@@ -2895,6 +2956,12 @@ dt_simplify::gen (FILE *f, int indent, b
 void
 decision_tree::gen_gimple (FILE *f)
 {
+  root->analyze ();
+
+  fprintf (stderr, "GIMPLE decision tree has %u leafs, maximum depth %u and "
+	   "a total number of %u nodes\n", root->num_leafs, root->max_level,
+	   root->total_size);
+
   for (unsigned n = 1; n <= 3; ++n)
     {
       fprintf (f, "\nstatic bool\n"
@@ -2941,6 +3008,12 @@ decision_tree::gen_gimple (FILE *f)
 void
 decision_tree::gen_generic (FILE *f)
 {
+  root->analyze ();
+
+  fprintf (stderr, "GENERIC decision tree has %u leafs, maximum depth %u and "
+	   "a total number of %u nodes\n", root->num_leafs, root->max_level,
+	   root->total_size);
+
   for (unsigned n = 1; n <= 3; ++n)
     {
       fprintf (f, "\ntree\n"