compile.c: optimize useless branches

* compile.c (iseq_peephole_optimize): eliminate always/never
  branches after a literal object.  this sequence typically
  appears by defined? operator for a method call on a local
  variable.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52633 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 34 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index b5a13556d9..2075e954e1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Wed Nov 18 11:32:15 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* compile.c (iseq_peephole_optimize): eliminate always/never
+	  branches after a literal object.  this sequence typically
+	  appears by defined? operator for a method call on a local
+	  variable.
+
 Wed Nov 18 10:33:06 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* ext/socket/ancdata.c (bsock_recvmsg_internal): stretch the buffer size
diff --git a/compile.c b/compile.c
index f66f12e94b..ae900fbf31 100644
--- a/compile.c
+++ b/compile.c
@@ -2031,6 +2031,33 @@ iseq_peephole_optimize(rb_iseq_t *iseq, LINK_ELEMENT *list, const int do_tailcal
 		 */
 		replace_destination(iobj, nobj);
 	    }
+	    else if (pobj) {
+		int cond;
+		if (pobj->insn_id == BIN(putobject)) {
+		    cond = (iobj->insn_id == BIN(branchif) ?
+			    OPERAND_AT(pobj, 0) != Qfalse :
+			    iobj->insn_id == BIN(branchunless) ?
+			    OPERAND_AT(pobj, 0) == Qfalse :
+			    FALSE);
+		}
+		else if (pobj->insn_id == BIN(putstring)) {
+		    cond = iobj->insn_id == BIN(branchif);
+		}
+		else if (pobj->insn_id == BIN(putnil)) {
+		    cond = iobj->insn_id != BIN(branchif);
+		}
+		else break;
+		REMOVE_ELEM(&pobj->link);
+		if (cond) {
+		    iobj->insn_id = BIN(jump);
+		    goto again;
+		}
+		else {
+		    unref_destination(iobj);
+		    REMOVE_ELEM(&iobj->link);
+		}
+		break;
+	    }
 	    else break;
 	    nobj = (INSN *)get_destination_insn(nobj);
 	}