Improve Hash#merge performance

* hash.c (rb_hash_merge): use rb_hash_dup() instead of rb_obj_dup() to duplicate
    Hash object. rb_hash_dup() is faster duplicating function for Hash object
    which got rid of Hash#initialize_dup method calling.

    Hash#merge will be faster around 60%.
    [ruby-dev:50026] [Bug #13343] [Fix GH-1533]

### Before
                 user     system      total        real
Hash#merge   0.160000   0.020000   0.180000 (  0.182357)

### After
                 user     system      total        real
Hash#merge   0.110000   0.010000   0.120000 (  0.114404)

### Test code
require 'benchmark'

Benchmark.bmbm do |x|
  hash1 = {}
  100.times { |i| hash1[i.to_s] = i }
  hash2 = {}
  100.times { |i| hash2[(i*2).to_s] = i*2 }

  x.report "Hash#merge" do
    10000.times do
      hash1.merge(hash2)
    end
  end
end

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58811 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 1 deletions

diff --git a/hash.c b/hash.c
index 60c491f14e..d616e8e90e 100644
--- a/hash.c
+++ b/hash.c
@@ -2496,7 +2496,7 @@ rb_hash_update_by(VALUE hash1, VALUE hash2, rb_hash_update_func *func)
 static VALUE
 rb_hash_merge(VALUE hash1, VALUE hash2)
 {
-    return rb_hash_update(rb_obj_dup(hash1), hash2);
+    return rb_hash_update(rb_hash_dup(hash1), hash2);
 }
 
 static int