Collapse putobject, putobject, newarray

This collapses:

```
== disasm: #<ISeq:bar@bench.rb:3 (3,0)-(5,3)> (catch: FALSE)
0000 putobject                    "a"                                 (   4)[LiCa]
0002 putobject                    "b"
0004 putobject                    "c"
0006 putobject                    "d"
0008 putobject                    "e"
0010 putobject                    "f"
0012 putobject                    "g"
0014 putobject                    "h"
0016 putobject                    "i"
0018 putobject                    "j"
0020 putobject                    "k"
0022 newarray                     11
0024 leave                                                            (   5)[Re]
```

In to this:

```
== disasm: #<ISeq:bar@bench.rb:3 (3,0)-(5,3)> (catch: FALSE)
0000 duparray                     ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"](   4)[LiCa]
0002 leave                                                            (   5)[Re]
```

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66106 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

compile.c

@@ -2823,6 +2823,53 @@ iseq_peephole_optimize(rb_iseq_t *iseq, LINK_ELEMENT *list, const int do_tailcal
 	}
     }
 
+    /*
+     * putobject "foo"
+     * putobject "bar"
+     * newarray 2
+     *
+     * ==>
+     *
+     * duparray ["foo", "bar"]
+     */
+    if (IS_INSN_ID(iobj, newarray)) {
+	int len;
+
+	len = NUM2INT(OPERAND_AT(iobj, 0));
+
+	if (len > 0) {
+	    INSN *link;
+	    INSN *cur;
+	    int i;
+
+	    link = iobj;
+	    i = len;
+	    while(i > 0) {
+		link = (INSN *)get_prev_insn(link);
+		if (!IS_INSN_ID(link, putobject))
+		    break;
+
+		i--;
+	    }
+
+	    /* All previous instructions were `putobject` */
+	    if (i == 0) {
+		VALUE list = rb_ary_new_capa(len);
+		iseq_add_mark_object_compile_time(iseq, list);
+
+		while(i < len) {
+		    cur = link;
+		    rb_ary_push(list, OPERAND_AT(cur, 0));
+		    link = (INSN *)get_next_insn(link);
+		    ELEM_REMOVE(&cur->link);
+		    i++;
+		}
+		iobj->insn_id = BIN(duparray);
+		OPERAND_AT(iobj, 0) = list;
+	    }
+	}
+    }
+
     if (IS_INSN_ID(iobj, leave)) {
 	remove_unreachable_chunk(iseq, iobj->link.next);
     }