compile.c: fix performance of strconcat

* compile.c (compile_dstr_fragments): fix performance by omitting
  the first empty string only for keeping literal encoding if
  other literals are too.  [ruby-core:70930] [Bug #11556]
* string.c (rb_str_append_literal): append but keep encoding non
  US-ASCII.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51970 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 1 deletions

diff --git a/insns.def b/insns.def
index 7eb322120b..a923d3a4d6 100644
--- a/insns.def
+++ b/insns.def
@@ -370,7 +370,7 @@ concatstrings
     val = rb_str_resurrect(TOPN(i));
     while (i-- > 0) {
 	const VALUE v = TOPN(i);
-	rb_str_append(val, v);
+	rb_str_append_literal(val, v);
     }
     POPN(num);
 }