diff --git a/sim/common/Make-common.in b/sim/common/Make-common.in
index 6ccf986103..dbcc0ebe16 100644
--- a/sim/common/Make-common.in
+++ b/sim/common/Make-common.in
@@ -739,6 +739,6 @@ cgen-desc: force
 	$(SHELL) $(srccom)/cgen.sh desc $(srcdir) \
 		$(CGEN) $(CGENDIR) "$(CGENFLAGS)" \
 		$(arch) "$(FLAGS)" $(cpu) "$(isa)" $(mach) "$(SUFFIX)" \
-		$(archfile) ignored
+		$(archfile) ignored $(opcfile)
 
 ## End COMMON_POST_CONFIG_FRAG
diff --git a/sim/common/cgen.sh b/sim/common/cgen.sh
index 172edcb7ca..8718835468 100644
--- a/sim/common/cgen.sh
+++ b/sim/common/cgen.sh
@@ -3,7 +3,7 @@
 #
 # Usage: /bin/sh cgen.sh {"arch"|"cpu"|"decode"|"defs"|"cpu-decode"} \
 #	srcdir cgen cgendir cgenflags \
-#	arch archflags cpu mach suffix archfile extrafiles
+#	arch archflags cpu mach suffix archfile extrafiles opcfile
 #
 # We store the generated files in the source directory until we decide to
 # ship a Scheme interpreter (or other implementation) with gdb/binutils.
@@ -26,9 +26,12 @@ shift ; mach=$9
 shift ; suffix=$9
 shift ; archfile=$9
 shift ; extrafiles=$9
+shift ; opcfile=$9
 
 rootdir=${srcdir}/../..
 
+test -z "${opcfile}" && opcfile=/dev/null
+
 if test -z "$isa" ; then
   isa=all
   prefix=$cpu
@@ -196,6 +199,7 @@ desc)
 	${cgen} -s ${cgendir}/cgen-opc.scm \
 		-s ${cgendir} \
 		${cgenflags} \
+		-OPC ${opcfile} \
 		-f "${archflags}" \
 		-m ${mach} \
 		-a ${archfile} \