string.c: fix non-embedded string

* string.c (rb_str_resurrect): fix resurrection of short enough to
  be embedded but not embedded string.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52073 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Wed Oct  7 20:43:14 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (rb_str_resurrect): fix resurrection of short enough to
+	  be embedded but not embedded string.
+
 Wed Oct 07 20:17:29 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* gc.c (newobj_of): divide fast path and slow path

benchmark/bm_vm2_string_literal.rb

@@ -0,0 +1,5 @@
+i = 0
+while i<6_000_000 # benchmark loop 2
+  i += 1
+  x = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+end

string.c

@@ -1250,27 +1250,36 @@ rb_str_dup(VALUE str)
 VALUE
 rb_str_resurrect(VALUE str)
 {
+    enum {embed_size = RSTRING_EMBED_LEN_MAX + 1};
+    const VALUE flag_mask =
+	RSTRING_NOEMBED | RSTRING_EMBED_LEN_MASK |
+	ENC_CODERANGE_MASK | ENCODING_MASK |
+	FL_TAINT | FL_FREEZE
+	;
+    VALUE flags = FL_TEST_RAW(str, flag_mask);
     VALUE dup;
-    VALUE flags = FL_TEST_RAW(str,
-			      RSTRING_NOEMBED |
-			      RSTRING_EMBED_LEN_MASK |
-			      ENC_CODERANGE_MASK |
-			      ENCODING_MASK |
-			      FL_TAINT | FL_FREEZE);
 
     if (RUBY_DTRACE_STRING_CREATE_ENABLED()) {
 	RUBY_DTRACE_STRING_CREATE(RSTRING_LEN(str),
 				  rb_sourcefile(), rb_sourceline());
     }
     dup = str_alloc(rb_cString);
-    MEMCPY(RSTRING(dup)->as.ary, RSTRING(str)->as.ary, VALUE, 3);
+    MEMCPY(RSTRING(dup)->as.ary, RSTRING(str)->as.ary,
+	   char, embed_size);
     if (flags & STR_NOEMBED) {
 	if (UNLIKELY(!(flags & FL_FREEZE))) {
 	    str = str_new_frozen(rb_cString, str);
 	    FL_SET_RAW(str, flags & FL_TAINT);
+	    flags = FL_TEST_RAW(str, flag_mask);
+	}
+	if (flags & STR_NOEMBED) {
+	    RB_OBJ_WRITE(dup, &RSTRING(dup)->as.heap.aux.shared, str);
+	    flags |= STR_SHARED;
+	}
+	else {
+	    MEMCPY(RSTRING(dup)->as.ary, RSTRING(str)->as.ary,
+		   char, embed_size);
 	}
-	RB_OBJ_WRITE(dup, &RSTRING(dup)->as.heap.aux.shared, str);
-	flags |= STR_SHARED;
     }
     FL_SET_RAW(dup, flags & ~FL_FREEZE);
     return dup;