diff --git a/basis/compiler/cfg/def-use/def-use.factor b/basis/compiler/cfg/def-use/def-use.factor
index 825ff71b9b..54cff2ccaa 100644
--- a/basis/compiler/cfg/def-use/def-use.factor
+++ b/basis/compiler/cfg/def-use/def-use.factor
@@ -11,6 +11,10 @@ GENERIC: defs-vreg ( insn -- vreg/f )
 GENERIC: temp-vregs ( insn -- seq )
 GENERIC: uses-vregs ( insn -- seq )
 
+M: insn defs-vreg drop f ;
+M: insn temp-vregs drop { } ;
+M: insn uses-vregs drop { } ;
+
 M: ##phi uses-vregs inputs>> values ;
 
 <PRIVATE
@@ -24,19 +28,25 @@ M: ##phi uses-vregs inputs>> values ;
     } case ;
 
 : define-defs-vreg-method ( insn -- )
-    [ \ defs-vreg create-method ]
-    [ insn-def-slot [ name>> reader-word 1quotation ] [ [ drop f ] ] if* ] bi
-    define ;
+    dup insn-def-slot dup [
+        [ \ defs-vreg create-method ]
+        [ name>> reader-word 1quotation ] bi*
+        define
+    ] [ 2drop ] if ;
 
 : define-uses-vregs-method ( insn -- )
-    [ \ uses-vregs create-method ]
-    [ insn-use-slots [ name>> ] map slot-array-quot ] bi
-    define ;
+    dup insn-use-slots [ drop ] [
+        [ \ uses-vregs create-method ]
+        [ [ name>> ] map slot-array-quot ] bi*
+        define
+    ] if-empty ;
 
 : define-temp-vregs-method ( insn -- )
-    [ \ temp-vregs create-method ]
-    [ insn-temp-slots [ name>> ] map slot-array-quot ] bi
-    define ;
+    dup insn-temp-slots [ drop ] [
+        [ \ temp-vregs create-method ]
+        [ [ name>> ] map slot-array-quot ] bi*
+        define
+    ] if-empty ;
 
 PRIVATE>
 
diff --git a/basis/compiler/cfg/renaming/functor/functor.factor b/basis/compiler/cfg/renaming/functor/functor.factor
index 2af68e9175..261aab6c54 100644
--- a/basis/compiler/cfg/renaming/functor/functor.factor
+++ b/basis/compiler/cfg/renaming/functor/functor.factor
@@ -20,15 +20,19 @@ WHERE
 
 GENERIC: rename-insn-defs ( insn -- )
 
-insn-classes get [
+M: insn rename-insn-defs drop ;
+
+insn-classes get [ insn-def-slot ] filter [
     [ \ rename-insn-defs create-method-in ]
-    [ insn-def-slot dup [ name>> 1array ] when DEF-QUOT slot-change-quot ] bi
+    [ insn-def-slot name>> 1array DEF-QUOT slot-change-quot ] bi
     define
 ] each
 
 GENERIC: rename-insn-uses ( insn -- )
 
-insn-classes get { ##phi } diff [
+M: insn rename-insn-uses drop ;
+
+insn-classes get { ##phi } diff [ insn-use-slots empty? not ] filter [
     [ \ rename-insn-uses create-method-in ]
     [ insn-use-slots [ name>> ] map USE-QUOT slot-change-quot ] bi
     define
@@ -39,7 +43,9 @@ M: ##phi rename-insn-uses
 
 GENERIC: rename-insn-temps ( insn -- )
 
-insn-classes get [
+M: insn rename-insn-temps drop ;
+
+insn-classes get [ insn-temp-slots empty? not ] filter [
     [ \ rename-insn-temps create-method-in ]
     [ insn-temp-slots [ name>> ] map TEMP-QUOT slot-change-quot ] bi
     define
diff --git a/basis/compiler/cfg/representations/preferred/preferred.factor b/basis/compiler/cfg/representations/preferred/preferred.factor
index 1e07e56b35..726521cfe1 100644
--- a/basis/compiler/cfg/representations/preferred/preferred.factor
+++ b/basis/compiler/cfg/representations/preferred/preferred.factor
@@ -11,6 +11,10 @@ GENERIC: defs-vreg-rep ( insn -- rep/f )
 GENERIC: temp-vreg-reps ( insn -- reps )
 GENERIC: uses-vreg-reps ( insn -- reps )
 
+M: insn defs-vreg-rep drop f ;
+M: insn temp-vreg-reps drop { } ;
+M: insn uses-vreg-reps drop { } ;
+
 <PRIVATE
 
 : rep-getter-quot ( rep -- quot )
@@ -21,9 +25,11 @@ GENERIC: uses-vreg-reps ( insn -- reps )
     } case ;
 
 : define-defs-vreg-rep-method ( insn -- )
-    [ \ defs-vreg-rep create-method ]
-    [ insn-def-slot [ rep>> rep-getter-quot ] [ [ drop f ] ] if* ]
-    bi define ;
+    dup insn-def-slot dup [
+        [ \ defs-vreg-rep create-method ]
+        [ rep>> rep-getter-quot ]
+        bi* define
+    ] [ 2drop ] if ;
 
 : reps-getter-quot ( reps -- quot )
     dup [ rep>> { f scalar-rep } member-eq? not ] all? [
@@ -38,14 +44,18 @@ GENERIC: uses-vreg-reps ( insn -- reps )
     ] if ;
 
 : define-uses-vreg-reps-method ( insn -- )
-    [ \ uses-vreg-reps create-method ]
-    [ insn-use-slots reps-getter-quot ]
-    bi define ;
+    dup insn-use-slots [ drop ] [
+        [ \ uses-vreg-reps create-method ]
+        [ reps-getter-quot ]
+        bi* define
+    ] if-empty ;
 
 : define-temp-vreg-reps-method ( insn -- )
-    [ \ temp-vreg-reps create-method ]
-    [ insn-temp-slots reps-getter-quot ]
-    bi define ;
+    dup insn-temp-slots [ drop ] [
+        [ \ temp-vreg-reps create-method ]
+        [ reps-getter-quot ]
+        bi* define
+    ] if-empty ;
 
 PRIVATE>