compile.c: massign optimization

* compile.c (compile_massign): optimization for special case,
  assignments by aset or attrset.
  http://kokizzu.blogspot.jp/2015/02/c-java-hhvm-ruby-nodejsrhinojscspidermo.html
  http://www.atdot.net/~ko1/diary/201502.html#d16

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49614 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,10 @@
+Mon Feb 16 20:58:49 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* compile.c (compile_massign): optimization for special case,
+	  assignments by aset or attrset.
+	  http://kokizzu.blogspot.jp/2015/02/c-java-hhvm-ruby-nodejsrhinojscspidermo.html
+	  http://www.atdot.net/~ko1/diary/201502.html#d16
+
 Sun Feb 15 10:41:23 2015  Sho Hashimoto  <sho-h@ruby-lang.org>
 
 	* doc/standard_library.rdoc: [DOC] delete removed libraries.

compile.c

@@ -2782,6 +2782,7 @@ compile_massign(rb_iseq_t *iseq, LINK_ANCHOR *ret, NODE *node, int poped)
 
     if (!poped || splatn || !compile_massign_opt(iseq, ret, rhsn, lhsn)) {
 	int llen = 0;
+	int expand = 1;
 	DECL_ANCHOR(lhsseq);
 
 	INIT_ANCHOR(lhsseq);
@@ -2797,9 +2798,30 @@ compile_massign(rb_iseq_t *iseq, LINK_ANCHOR *ret, NODE *node, int poped)
 	if (!poped) {
 	    ADD_INSN(ret, nd_line(node), dup);
 	}
-
-	ADD_INSN2(ret, nd_line(node), expandarray,
-		  INT2FIX(llen), INT2FIX(lhs_splat));
+	else if (!lhs_splat) {
+	    INSN *last = (INSN*)ret->last;
+	    if (last->link.type == ISEQ_ELEMENT_INSN &&
+		last->insn_id == BIN(newarray) &&
+		last->operand_size == 1 &&
+		OPERAND_AT(last, 0) == INT2FIX(llen)) {
+		/* special case: assign to aset or attrset */
+		if (llen == 2) {
+		    POP_ELEMENT(ret);
+		    ADD_INSN(ret, nd_line(node), swap);
+		    expand = 0;
+		}
+#if 0
+		else if (llen > 2) {
+		    last->insn_id = BIN(reverse);
+		    expand = 0;
+		}
+#endif
+	    }
+	}
+	if (expand) {
+	    ADD_INSN2(ret, nd_line(node), expandarray,
+		      INT2FIX(llen), INT2FIX(lhs_splat));
+	}
 	ADD_SEQ(ret, lhsseq);
 
 	if (lhs_splat) {