Improve performance of some Time methods

internal.h : add rb_numeric_quo() as internal API.
rational.c : rename numeric_quo() to rb_numeric_quo() as internal API.
time.c (quov): optimize by invoking rb_numeric_quo() to retrieve a value of
    Numeric#quo instead of method dispatching via rb_funcall().

    Time#subsec ->  7 % up
    Time#-      -> 26 % up
    Time#to_f   -> 30 % up
    Time#to_r   ->  7 % up

    [ruby-core:80915] [Bug #13519] [Fix GH-1601]

### Before
         Time#subsec      2.024M (± 8.7%) i/s -     10.062M in   5.009762s
              Time#-      5.049M (± 4.7%) i/s -     25.186M in   5.002379s
           Time#to_f      5.625M (± 4.2%) i/s -     28.066M in   5.000749s
           Time#to_r      1.880M (± 9.7%) i/s -      9.361M in   5.027527s

### After
         Time#subsec      2.155M (± 9.7%) i/s -     10.724M in   5.022579s
              Time#-      6.362M (± 2.0%) i/s -     31.824M in   5.004625s
           Time#to_f      7.287M (± 4.8%) i/s -     36.402M in   5.010983s
           Time#to_r      2.020M (± 9.4%) i/s -     10.059M in   5.021852s

### Test code
require 'benchmark/ips'

Benchmark.ips do |x|
  x.report "Time#subsec" do |t|
    time = Time.now
    t.times { time.subsec }
  end

  x.report "Time#-" do |t|
    time1 = Time.now
    time2 = Time.now
    t.times { time1 - time2 }
  end

  x.report "Time#to_f" do |t|
    time = Time.now
    t.times { time.to_f }
  end

  x.report "Time#to_r" do |t|
    time = Time.now
    t.times { time.to_r }
  end
end

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58921 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

internal.h

@@ -1540,6 +1540,7 @@ VALUE rb_rational_reciprocal(VALUE x);
 VALUE rb_cstr_to_rat(const char *, int);
 VALUE rb_rational_abs(VALUE self);
 VALUE rb_rational_cmp(VALUE self, VALUE other);
+VALUE rb_numeric_quo(VALUE x, VALUE y);
 
 /* re.c */
 VALUE rb_reg_compile(VALUE str, int options, const char *sourcefile, int sourceline);

rational.c

@@ -2015,8 +2015,8 @@ numeric_denominator(VALUE self)
  *  Returns the most exact division (rational for integers, float for floats).
  */
 
-static VALUE
-numeric_quo(VALUE x, VALUE y)
+VALUE
+rb_numeric_quo(VALUE x, VALUE y)
 {
     if (RB_FLOAT_TYPE_P(y)) {
         return rb_funcall(x, rb_intern("fdiv"), 1, y);
@@ -2736,7 +2736,7 @@ Init_Rational(void)
 
     rb_define_method(rb_cNumeric, "numerator", numeric_numerator, 0);
     rb_define_method(rb_cNumeric, "denominator", numeric_denominator, 0);
-    rb_define_method(rb_cNumeric, "quo", numeric_quo, 1);
+    rb_define_method(rb_cNumeric, "quo", rb_numeric_quo, 1);
 
     rb_define_method(rb_cInteger, "numerator", integer_numerator, 0);
     rb_define_method(rb_cInteger, "denominator", integer_denominator, 0);

time.c

@@ -144,7 +144,7 @@ quov(VALUE x, VALUE y)
             return LONG2FIX(c);
         }
     }
-    ret = rb_funcall(x, id_quo, 1, y);
+    ret = rb_numeric_quo(x, y);
     if (RB_TYPE_P(ret, T_RATIONAL) &&
         RRATIONAL(ret)->den == INT2FIX(1)) {
         ret = RRATIONAL(ret)->num;