nobu	2018-08-23 16:22:27 +0900 (Thu, 23 Aug 2018)

  New Revision: 64516

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=64516

  Log:
    compile.c: drop unused string
    
    * compile.c (iseq_peephole_optimize): drop unused dynamic string
      literal, without concatenation.

  Modified files:
    trunk/compile.c
Index: compile.c
===================================================================
--- compile.c	(revision 64515)
+++ compile.c	(revision 64516)
@@ -2942,6 +2942,15 @@ iseq_peephole_optimize(rb_iseq_t *iseq, https://github.com/ruby/ruby/blob/trunk/compile.c#L2942
 	    else if (previ == BIN(newarray) && iseq_pop_newarray(iseq, (INSN*)prev)) {
 		ELEM_REMOVE(&iobj->link);
 	    }
+	    else if (previ == BIN(concatstrings)) {
+		if (OPERAND_AT(prev, 0) == INT2FIX(1)) {
+		    ELEM_REMOVE(prev);
+		}
+		else {
+		    ELEM_REMOVE(&iobj->link);
+		    INSN_OF(prev) = BIN(adjuststack);
+		}
+	    }
 	}
     }
 

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