Improve performance of implicit type conversion

To convert the object implicitly, it has had two parts in convert_type() which are
  1. lookink up the method's id
  2. calling the method

Seems that strncmp() and strcmp() in convert_type() are slightly heavy to look up
the method's id for type conversion.

This patch will add and use internal APIs (rb_convert_type_with_id, rb_check_convert_type_with_id)
to call the method without looking up the method's id when convert the object.

Array#flatten -> 19 % up
Array#+       ->  3 % up

[ruby-dev:50024] [Bug #13341] [Fix GH-1537]

### Before
       Array#flatten    104.119k (± 1.1%) i/s -    525.690k in   5.049517s
             Array#+      1.993M (± 1.8%) i/s -     10.010M in   5.024258s

### After
       Array#flatten    124.005k (± 1.0%) i/s -    624.240k in   5.034477s
             Array#+      2.058M (± 4.8%) i/s -     10.302M in   5.019328s

### Test Code
require 'benchmark/ips'

class Foo
  def to_ary
    [1,2,3]
  end
end

Benchmark.ips do |x|

  ary = []
  100.times { |i| ary << i }
  array = [ary]

  x.report "Array#flatten" do |i|
    i.times { array.flatten }
  end

  x.report "Array#+" do |i|
    obj = Foo.new
    i.times { array + obj }
  end

end

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58978 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 2 insertions, 1 deletions

diff --git a/rational.c b/rational.c
index bd32399e79..ce95facda0 100644
--- a/rational.c
+++ b/rational.c
@@ -6,6 +6,7 @@
 */
 
 #include "internal.h"
+#include "id.h"
 #include <math.h>
 #include <float.h>
 
@@ -2610,7 +2611,7 @@ nurat_s_convert(int argc, VALUE *argv, VALUE klass)
 
     if (argc == 1) {
 	if (!(k_numeric_p(a1) && k_integer_p(a1)))
-	    return rb_convert_type(a1, T_RATIONAL, "Rational", "to_r");
+	    return rb_convert_type_with_id(a1, T_RATIONAL, "Rational", idTo_r);
     }
     else {
 	if ((k_numeric_p(a1) && k_numeric_p(a2)) &&