nobu	2015-11-11 18:38:20 +0900 (Wed, 11 Nov 2015)

  New Revision: 52538

  http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=52538

  Log:
    compile.c: comments for r52517 [ci skip]

  Modified files:
    trunk/compile.c
Index: compile.c
===================================================================
--- compile.c	(revision 52537)
+++ compile.c	(revision 52538)
@@ -2001,11 +2001,19 @@ iseq_peephole_optimize(rb_iseq_t *iseq, https://github.com/ruby/ruby/blob/trunk/compile.c#L2001
     }
 
     if (iobj->insn_id == BIN(pop)) {
+	/*
+	 *  putself / putnil / putobject obj / putstring "..."
+	 *  pop
+	 * =>
+	 *  # do nothing
+	 */
 	LINK_ELEMENT *prev = iobj->link.prev;
 	if (prev->type == ISEQ_ELEMENT_INSN) {
 	    enum ruby_vminsn_type previ = ((INSN *)prev)->insn_id;
 	    if (previ == BIN(putobject) || previ == BIN(putnil) ||
 		previ == BIN(putself) || previ == BIN(putstring)) {
+		/* just push operand or static value and pop soon, no
+		 * side effects */
 		REMOVE_ELEM(prev);
 		REMOVE_ELEM(&iobj->link);
 	    }

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