* array.c: Improve performance of Array#shift. use shared instead of

  MEMMOVE if with arguments. Patch by @ksss [fix GH-537]
* test/ruby/test_array.rb: ditto.
* benchmark/bm_array_shift.rb: Added benchmark of GH-537 issue.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49114 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

4 files changed, 38 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index d6e9d901af..f4fd304ace 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sat Jan  3 11:27:46 2015  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
+
+	* array.c: Improve performance of Array#shift. use shared instead of
+	  MEMMOVE if with arguments. Patch by @ksss [fix GH-537]
+	* test/ruby/test_array.rb: ditto.
+	* benchmark/bm_array_shift.rb: Added benchmark of GH-537 issue.
+
 Sat Jan  3 10:38:52 2015  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
 
 	* lib/net/http.rb: More descriptive error message when net/http fails
diff --git a/array.c b/array.c
index 6babe97ef9..08958aeb65 100644
--- a/array.c
+++ b/array.c
@@ -1066,14 +1066,21 @@ rb_ary_shift_m(int argc, VALUE *argv, VALUE ary)
     n = RARRAY_LEN(result);
     if (ARY_SHARED_P(ary)) {
 	if (ARY_SHARED_OCCUPIED(ARY_SHARED(ary))) {
+	  setup_occupied_shared:
 	    ary_mem_clear(ary, 0, n);
 	}
         ARY_INCREASE_PTR(ary, n);
     }
     else {
-	RARRAY_PTR_USE(ary, ptr, {
-	    MEMMOVE(ptr, ptr + n, VALUE, RARRAY_LEN(ary)-n);
-	}); /* WB: no new reference */
+	if (RARRAY_LEN(ary) < ARY_DEFAULT_SIZE) {
+	    RARRAY_PTR_USE(ary, ptr, {
+		MEMMOVE(ptr, ptr+n, VALUE, RARRAY_LEN(ary)-n);
+	    }); /* WB: no new reference */
+	}
+	else {
+	    ary_make_shared(ary);
+	    goto setup_occupied_shared;
+	}
     }
     ARY_INCREASE_LEN(ary, -n);
 
diff --git a/benchmark/bm_array_shift.rb b/benchmark/bm_array_shift.rb
new file mode 100644
index 0000000000..798bb9e3f4
--- /dev/null
+++ b/benchmark/bm_array_shift.rb
@@ -0,0 +1,14 @@
+require 'benchmark'
+
+Benchmark.bm do |x|
+  [10_000,1_000_000,100_000_000].each do |n|
+    ary = Array.new(n,0)
+    GC.start
+    x.report("#{n}:shift"){ ary.shift }
+    (0..4).each do |i|
+      ary = Array.new(n,0)
+      GC.start
+      x.report("#{n}:shift(#{i})"){ ary.shift(i) }
+    end
+  end
+end
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index 0a4b1379f1..04e66cce11 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -1904,6 +1904,8 @@ class TestArray < Test::Unit::TestCase
     a[3] = 3
     a.shift(2)
     assert_equal([2, 3], a)
+
+    assert_equal([1,1,1], ([1] * 100).shift(3))
   end
 
   def test_unshift_error
@@ -2356,6 +2358,11 @@ class TestArray < Test::Unit::TestCase
     b.replace(a)
     assert_equal((1..10).to_a, a.shift(10))
     assert_equal((11..100).to_a, a)
+
+    a = (1..30).to_a
+    assert_equal((1..3).to_a, a.shift(3))
+    # occupied
+    assert_equal((4..6).to_a, a.shift(3))
   end
 
   def test_replace_shared_ary