diff --git a/basis/compiler/cfg/value-numbering/conditions/conditions.factor b/basis/compiler/cfg/value-numbering/conditions/conditions.factor
deleted file mode 100644
index 5ef1c4fbc9..0000000000
--- a/basis/compiler/cfg/value-numbering/conditions/conditions.factor
+++ /dev/null
@@ -1,48 +0,0 @@
-! Copyright (C) 2008 Slava Pestov.
-! See http://factorcode.org/license.txt for BSD license.
-USING: kernel sequences layouts accessors combinators
-compiler.cfg.instructions
-compiler.cfg.value-numbering.graph
-compiler.cfg.value-numbering.expressions
-compiler.cfg.value-numbering.liveness
-compiler.cfg.value-numbering ;
-IN: compiler.cfg.value-numbering.conditions
-
-! The CFG builder produces naive code for the following code
-! sequence:
-!
-! fixnum< [ ... ] [ ... ] if
-!
-! The fixnum< comparison generates a boolean, which is then
-! tested against f.
-!
-! Using value numbering, we optimize the comparison of a boolean
-! against f where the boolean is the result of comparison.
-
-: ##branch-t? ( insn -- ? )
-    [ cc>> cc/= eq? ] [ src2>> \ f tag-number eq? ] bi and ; inline
-
-: of-boolean? ( insn -- expr/f ? )
-    src1>> vreg>expr dup compare-expr? ; inline
-
-: eliminate-boolean ( insn -- expr/f )
-    dup ##branch-t? [
-        of-boolean? [ drop f ] unless
-    ] [ drop f ] if ; inline
-
-M: ##compare-imm-branch number-values
-    dup eliminate-boolean [
-        [ in1>> live-vn ] [ in2>> live-vn ] bi
-    ] [ call-next-method ] ?if ;
- 
-: >compare-expr< [ in1>> vn>vreg ] [ in2>> vn>vreg ] [ cc>> ] tri ; inline
-: >compare-imm-expr< [ in1>> vn>vreg ] [ in2>> vn>constant ] [ cc>> ] tri ; inline
-
-M: ##compare-imm-branch eliminate
-    dup eliminate-boolean [
-        dup op>> {
-            { \ ##compare [ >compare-expr< f \ ##compare-branch boa ] }
-            { \ ##compare-imm [ >compare-imm-expr< f \ ##compare-imm-branch boa ] }
-            { \ ##compare-float [ >compare-expr< f \ ##compare-float-branch boa ] }
-        } case
-    ] [ call-next-method ] ?if ;
diff --git a/basis/compiler/cfg/value-numbering/constant-fold/constant-fold.factor b/basis/compiler/cfg/value-numbering/constant-fold/constant-fold.factor
deleted file mode 100644
index ed09bd7cec..0000000000
--- a/basis/compiler/cfg/value-numbering/constant-fold/constant-fold.factor
+++ /dev/null
@@ -1,18 +0,0 @@
-! Copyright (C) 2008 Slava Pestov.
-! See http://factorcode.org/license.txt for BSD license.
-USING: accessors kernel
-compiler.cfg.value-numbering.graph
-compiler.cfg.value-numbering.expressions ;
-IN: compiler.cfg.value-numbering.constant-fold
-
-GENERIC: constant-fold ( insn -- insn' )
-
-M: vop constant-fold ;
-
-: expr>insn ( out constant-expr -- constant-op )
-    [ value>> ] [ op>> ] bi new swap >>value swap >>out ;
-
-M: pure-op constant-fold
-    dup out>>
-    dup vreg>expr
-    dup constant-expr? [ expr>insn nip ] [ 2drop ] if ;
diff --git a/basis/compiler/cfg/value-numbering/liveness/liveness.factor b/basis/compiler/cfg/value-numbering/liveness/liveness.factor
deleted file mode 100644
index 2dd2e56968..0000000000
--- a/basis/compiler/cfg/value-numbering/liveness/liveness.factor
+++ /dev/null
@@ -1,39 +0,0 @@
-! Copyright (C) 2008 Slava Pestov.
-! See http://factorcode.org/license.txt for BSD license.
-USING: namespaces kernel assocs sets accessors
-compiler.cfg.instructions
-compiler.cfg.instructions.syntax
-compiler.cfg.value-numbering.graph
-compiler.cfg.value-numbering.expressions ;
-IN: compiler.cfg.value-numbering.liveness
-
-! A set of VNs which are (transitively) used by effect-ops. This
-! is precisely the set of VNs whose value is needed outside of
-! the basic block.
-SYMBOL: live-vns
-
-GENERIC: live-expr ( expr -- )
-
-: live-vn ( vn -- )
-    #! Mark a VN and all VNs used in its computation as live.
-    dup live-vns get key? [ drop ] [
-        [ live-vns get conjoin ] [ vn>expr live-expr ] bi
-    ] if ;
-
-: live-vreg ( vreg -- ) vreg>vn live-vn ;
-
-M: expr live-expr drop ;
-M: unary-expr live-expr in>> live-vn ;
-M: binary-expr live-expr [ in1>> live-vn ] [ in2>> live-vn ] bi ;
-
-: live? ( vreg -- ? )
-    dup vreg>vn tuck vn>vreg =
-    [ live-vns get key? ] [ drop f ] if ;
-
-: init-liveness ( -- )
-    H{ } clone live-vns set ;
-
-GENERIC: eliminate ( insn -- insn' )
-
-M: ##flushable eliminate dup dst>> live? [ drop f ] unless ;
-M: insn eliminate ;
diff --git a/basis/compiler/cfg/value-numbering/propagate/propagate.factor b/basis/compiler/cfg/value-numbering/propagate/propagate.factor
index 5142c3c776..c1d6ea562f 100644
--- a/basis/compiler/cfg/value-numbering/propagate/propagate.factor
+++ b/basis/compiler/cfg/value-numbering/propagate/propagate.factor
@@ -60,5 +60,3 @@ M: ##dispatch propagate
     [ resolve ] change-src ;
 
 M: insn propagate ;
-
-M: f propagate ;
diff --git a/basis/compiler/cfg/value-numbering/rewrite/rewrite.factor b/basis/compiler/cfg/value-numbering/rewrite/rewrite.factor
new file mode 100644
index 0000000000..a5fcc58365
--- /dev/null
+++ b/basis/compiler/cfg/value-numbering/rewrite/rewrite.factor
@@ -0,0 +1,55 @@
+! Copyright (C) 2008 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+USING: kernel sequences layouts accessors combinators namespaces
+math
+compiler.cfg.instructions
+compiler.cfg.instructions.syntax
+compiler.cfg.value-numbering.graph
+compiler.cfg.value-numbering.expressions ;
+IN: compiler.cfg.value-numbering.rewrite
+
+GENERIC: rewrite ( insn -- insn' )
+
+: ##branch-t? ( insn -- ? )
+    [ cc>> cc/= eq? ] [ src2>> \ f tag-number eq? ] bi and ; inline
+
+: rewrite-boolean-comparison? ( insn -- ? )
+    dup ##branch-t? [
+        src1>> vreg>expr compare-expr?
+    ] [ drop f ] if ; inline
+ 
+: >compare-expr< ( expr -- in1 in2 cc )
+    [ in1>> vn>vreg ] [ in2>> vn>vreg ] [ cc>> ] tri ; inline
+
+: >compare-imm-expr< ( expr -- in1 in2 cc )
+    [ in1>> vn>vreg ] [ in2>> vn>constant ] [ cc>> ] tri ; inline
+
+: rewrite-boolean-comparison ( expr -- insn )
+    src1>> vreg>expr dup op>> {
+        { \ ##compare [ >compare-expr< f \ ##compare-branch boa ] }
+        { \ ##compare-imm [ >compare-imm-expr< f \ ##compare-imm-branch boa ] }
+        { \ ##compare-float [ >compare-expr< f \ ##compare-float-branch boa ] }
+    } case ;
+
+: tag-fixnum-expr? ( expr -- ? )
+    dup op>> \ ##shl-imm eq?
+    [ in2>> vn>expr value>> tag-bits get = ] [ drop f ] if ;
+
+: rewrite-tagged-comparison? ( insn -- ? )
+    #! Are we comparing two tagged fixnums? Then untag them.
+    [ src1>> vreg>expr tag-fixnum-expr? ]
+    [ src2>> tag-mask get bitand 0 = ]
+    bi and ; inline
+
+: rewrite-tagged-comparison ( insn -- insn' )
+    [ src1>> vreg>expr in1>> vn>vreg ]
+    [ src2>> tag-bits get neg shift ]
+    [ cc>> ]
+    tri
+    f \ ##compare-imm-branch boa ;
+
+M: ##compare-imm-branch rewrite
+    dup rewrite-boolean-comparison? [ rewrite-boolean-comparison ] when
+    dup rewrite-tagged-comparison? [ rewrite-tagged-comparison ] when ;
+
+M: insn rewrite ;
diff --git a/basis/compiler/cfg/value-numbering/simplify/simplify.factor b/basis/compiler/cfg/value-numbering/simplify/simplify.factor
index 4c3589d710..e51b0d211f 100644
--- a/basis/compiler/cfg/value-numbering/simplify/simplify.factor
+++ b/basis/compiler/cfg/value-numbering/simplify/simplify.factor
@@ -10,13 +10,6 @@ IN: compiler.cfg.value-numbering.simplify
 ! Return value of f means we didn't simplify.
 GENERIC: simplify* ( expr -- vn/expr/f )
 
-: simplify-not ( in -- vn/expr/f )
-    {
-        { [ dup constant-expr? ] [ value>> bitnot <constant> ] }
-        { [ dup op>> \ ##not = ] [ in>> ] }
-        [ drop f ]
-    } cond ;
-
 : simplify-box-float ( in -- vn/expr/f )
     dup op>> \ ##unbox-float = [ in>> ] [ drop f ] if ;
 
@@ -29,127 +22,11 @@ M: unary-expr simplify*
     [ in>> vn>expr ] [ op>> ] bi {
         { \ ##copy [ ] }
         { \ ##copy-float [ ] }
-        { \ ##not [ simplify-not ] }
         { \ ##box-float [ simplify-box-float ] }
         { \ ##unbox-float [ simplify-unbox-float ] }
         [ 2drop f ]
     } case ;
 
-! : expr-zero? ( expr -- ? ) T{ constant-expr f f 0 } = ; inline
-! 
-! : expr-one? ( expr -- ? ) T{ constant-expr f f 1 } = ; inline
-! 
-! : expr-neg-one? ( expr -- ? ) T{ constant-expr f f -1 } = ; inline
-! 
-! : identity ( in1 in2 val -- expr ) 2nip <constant> ; inline
-! 
-! : constant-fold? ( in1 in2 -- ? )
-!     [ constant-expr? ] both? ;
-! 
-! : constant-fold ( in1 in2 quot -- expr )
-!     2over constant-fold? [
-!         [ [ value>> ] bi@ ] dip call <constant>
-!     ] [ 3drop f ] if ; inline
-! 
-! : simplify-add ( in1 in2 -- vn/expr/f )
-!     {
-!         { [ over expr-zero? ] [ nip ] }
-!         { [ dup expr-zero? ] [ drop ] }
-!         [ [ + ] constant-fold ]
-!     } cond ;
-! 
-! : simplify-mul ( in1 in2 -- vn/expr/f )
-!     {
-!         { [ over expr-one? ] [ nip ] }
-!         { [ dup expr-one? ] [ drop ] }
-!         [ [ * ] constant-fold ]
-!     } cond ;
-! 
-! : simplify-and ( in1 in2 -- vn/expr/f )
-!     {
-!         { [ dup expr-zero? ] [ 0 identity ] }
-!         { [ dup expr-neg-one? ] [ drop ] }
-!         { [ 2dup = ] [ drop ] }
-!         [ [ bitand ] constant-fold ]
-!     } cond ;
-! 
-! : simplify-or ( in1 in2 -- vn/expr/f )
-!     {
-!         { [ dup expr-zero? ] [ drop ] }
-!         { [ dup expr-neg-one? ] [ -1 identity ] }
-!         { [ 2dup = ] [ drop ] }
-!         [ [ bitor ] constant-fold ]
-!     } cond ;
-! 
-! : simplify-xor ( in1 in2 -- vn/expr/f )
-!     {
-!         { [ dup expr-zero? ] [ drop ] }
-!         [ [ bitxor ] constant-fold ]
-!     } cond ;
-! 
-! : commutative-operands ( expr -- in1 in2 )
-!     [ in1>> vn>expr ] [ in2>> vn>expr ] bi
-!     over constant-expr? [ swap ] when ;
-! 
-! M: commutative-expr simplify*
-!     [ commutative-operands ] [ op>> ] bi {
-!         { ##add [ simplify-add ] }
-!         { ##mul [ simplify-mul ] }
-!         { ##and [ simplify-and ] }
-!         { ##or [ simplify-or ] }
-!         { ##xor [ simplify-xor ] }
-!         [ 3drop f ]
-!     } case ;
-! 
-! : simplify-sub ( in1 in2 -- vn/expr/f )
-!     {
-!         { [ dup expr-zero? ] [ drop ] }
-!         { [ 2dup = ] [ 0 identity ] }
-!         [ [ - ] constant-fold ]
-!     } cond ;
-! 
-! : simplify-shl ( in1 in2 -- vn/expr/f )
-!     {
-!         { [ dup expr-zero? ] [ drop ] }
-!         { [ over expr-zero? ] [ drop ] }
-!         [ [ shift ] constant-fold ]
-!     } cond ;
-! 
-! : unsigned ( n -- n' )
-!     cell-bits 2^ 1- bitand ;
-! 
-! : useless-shift? ( in1 in2 -- ? )
-!     over op>> ##shl = [ [ in2>> ] [ expr>vn ] bi* = ] [ 2drop f ] if ;
-! 
-! : simplify-shr ( in1 in2 -- vn/expr/f )
-!     {
-!         { [ dup expr-zero? ] [ drop ] }
-!         { [ over expr-zero? ] [ drop ] }
-!         { [ 2dup useless-shift? ] [ drop in1>> ] }
-!         [ [ neg shift unsigned ] constant-fold ]
-!     } cond ;
-! 
-! : simplify-sar ( in1 in2 -- vn/expr/f )
-!     {
-!         { [ dup expr-zero? ] [ drop ] }
-!         { [ over expr-zero? ] [ drop ] }
-!         { [ 2dup useless-shift? ] [ drop in1>> ] }
-!         [ [ neg shift ] constant-fold ]
-!     } cond ;
-! 
-! : simplify-compare ( in1 in2 -- vn/expr/f )
-!     = [ +eq+ %cconst constant ] [ f ] if ;
-! 
-! M: binary-expr simplify*
-!     [ in1>> vn>expr ] [ in2>> vn>expr ] [ op>> ] tri {
-!         { ##sub [ simplify-isub ] }
-!         { ##shl [ simplify-shl ] }
-!         { ##shr [ simplify-shr ] }
-!         { ##sar [ simplify-sar ] }
-!         { ##compare [ simplify-compare ] }
-!         [ 3drop f ]
-!     } case ;
-
 M: expr simplify* drop f ;
 
 : simplify ( expr -- vn )
@@ -158,3 +35,8 @@ M: expr simplify* drop f ;
         { [ dup expr? ] [ expr>vn nip ] }
         { [ dup integer? ] [ nip ] }
     } cond ;
+
+GENERIC: number-values ( insn -- )
+
+M: ##flushable number-values [ >expr simplify ] [ dst>> ] bi set-vn ;
+M: insn number-values drop ;
diff --git a/basis/compiler/cfg/value-numbering/value-numbering-tests.factor b/basis/compiler/cfg/value-numbering/value-numbering-tests.factor
index 81121f3fe9..c8a1d7884c 100644
--- a/basis/compiler/cfg/value-numbering/value-numbering-tests.factor
+++ b/basis/compiler/cfg/value-numbering/value-numbering-tests.factor
@@ -4,6 +4,7 @@ compiler.cfg.registers cpu.architecture tools.test kernel ;
 [
     {
         T{ ##peek f V int-regs 45 D 1 }
+        T{ ##copy f V int-regs 48 V int-regs 45 }
         T{ ##compare-imm-branch f V int-regs 45 7 cc/= }
     }
 ] [
@@ -16,6 +17,7 @@ compiler.cfg.registers cpu.architecture tools.test kernel ;
 
 [
     {
+        T{ ##load-immediate f V int-regs 2 8 }
         T{ ##peek f V int-regs 3 D 0 }
         T{ ##slot-imm f V int-regs 4 V int-regs 3 1 3 }
         T{ ##replace f V int-regs 4 D 0 }
diff --git a/basis/compiler/cfg/value-numbering/value-numbering.factor b/basis/compiler/cfg/value-numbering/value-numbering.factor
index b411efef3a..d17b2a7e1f 100644
--- a/basis/compiler/cfg/value-numbering/value-numbering.factor
+++ b/basis/compiler/cfg/value-numbering/value-numbering.factor
@@ -2,33 +2,14 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: namespaces assocs biassocs classes kernel math accessors
 sorting sets sequences
-compiler.cfg.def-use
-compiler.cfg.instructions
-compiler.cfg.instructions.syntax
 compiler.cfg.value-numbering.graph
 compiler.cfg.value-numbering.expressions
-compiler.cfg.value-numbering.liveness
 compiler.cfg.value-numbering.propagate
-compiler.cfg.value-numbering.simplify ;
+compiler.cfg.value-numbering.simplify
+compiler.cfg.value-numbering.rewrite ;
 IN: compiler.cfg.value-numbering
 
-: insn>vn ( insn -- vn ) >expr simplify ; inline
-
-GENERIC: number-values ( insn -- )
-
-M: ##flushable number-values
-    dup ##pure? [ dup call-next-method ] unless
-    [ insn>vn ] [ dst>> ] bi set-vn ;
-
-M: insn number-values uses-vregs [ live-vreg ] each ;
-
-: init-value-numbering ( -- )
+: value-numbering ( insns -- insns' )
     init-value-graph
     init-expressions
-    init-liveness ;
-
-: value-numbering ( insns -- insns' )
-    init-value-numbering
-    [ [ number-values ] each ]
-    [ [ eliminate propagate ] map sift ]
-    bi ;
+    [ [ number-values ] [ rewrite propagate ] bi ] map ;