diff --git a/basis/compiler/cfg/def-use/authors.txt b/basis/compiler/cfg/def-use/authors.txt
new file mode 100644
index 0000000000..a44f8d7f8d
--- /dev/null
+++ b/basis/compiler/cfg/def-use/authors.txt
@@ -0,0 +1,2 @@
+Slava Pestov
+Daniel Ehrenberg
diff --git a/basis/compiler/cfg/def-use/def-use-tests.factor b/basis/compiler/cfg/def-use/def-use-tests.factor
new file mode 100644
index 0000000000..1153d9ea81
--- /dev/null
+++ b/basis/compiler/cfg/def-use/def-use-tests.factor
@@ -0,0 +1,37 @@
+! Copyright (C) 2009 Daniel Ehrenberg.
+! See http://factorcode.org/license.txt for BSD license.
+USING: kernel tools.test accessors vectors sequences namespaces
+arrays
+cpu.architecture
+compiler.cfg.def-use
+compiler.cfg
+compiler.cfg.debugger
+compiler.cfg.instructions
+compiler.cfg.registers ;
+
+V{
+    T{ ##peek f V int-regs 0 D 0 }
+    T{ ##peek f V int-regs 1 D 0 }
+    T{ ##peek f V int-regs 2 D 0 }
+} 1 test-bb
+V{
+    T{ ##replace f V int-regs 2 D 0 }
+} 2 test-bb
+1 get 2 get 1vector >>successors drop
+V{
+    T{ ##replace f V int-regs 0 D 0 }
+} 3 test-bb
+2 get 3 get 1vector >>successors drop
+V{ } 4 test-bb
+V{ } 5 test-bb
+3 get 4 get 5 get V{ } 2sequence >>successors drop
+V int-regs 2
+    2 get V int-regs 0 2array
+    3 get V int-regs 1 2array
+2array \ ##phi new-insn 1vector
+6 test-bb
+4 get 6 get 1vector >>successors drop
+5 get 6 get 1vector >>successors drop
+
+cfg new 1 get >>entry 0 set
+[ ] [ 0 get compute-def-use ] unit-test
diff --git a/basis/compiler/cfg/def-use/def-use.factor b/basis/compiler/cfg/def-use/def-use.factor
index 1c9ac90f78..8e8fbf3a2d 100644
--- a/basis/compiler/cfg/def-use/def-use.factor
+++ b/basis/compiler/cfg/def-use/def-use.factor
@@ -1,7 +1,7 @@
-! Copyright (C) 2008, 2009 Slava Pestov.
+! Copyright (C) 2008, 2009 Slava Pestov, Daniel Ehrenberg.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors arrays kernel assocs sequences namespaces fry
-sets compiler.cfg.rpo compiler.cfg.instructions ;
+sets compiler.cfg.rpo compiler.cfg.instructions locals ;
 IN: compiler.cfg.def-use
 
 GENERIC: defs-vreg ( insn -- vreg/f )
@@ -80,18 +80,18 @@ SYMBOLS: defs insns uses ;
         ] each-basic-block
     ] keep insns set ;
 
-: compute-uses ( cfg -- )
-    H{ } clone [
-        '[
-            dup instructions>> [
-                uses-vregs [
-                    _ conjoin-at
-                ] with each
-            ] with each
-        ] each-basic-block
-    ] keep
-    [ keys ] assoc-map
-    uses set ;
+:: compute-uses ( cfg -- )
+    ! Here, a phi node uses its argument in the block that it comes from.
+    H{ } clone :> use
+    cfg [| block |
+        block instructions>> [
+            dup ##phi?
+            [ inputs>> [ use conjoin-at ] assoc-each ]
+            [ uses-vregs [ block swap use conjoin-at ] each ]
+            if
+        ] each
+    ] each-basic-block
+    use [ keys ] assoc-map uses set ;
 
 : compute-def-use ( cfg -- )
-    [ compute-defs ] [ compute-uses ] [ compute-insns ] tri ;
\ No newline at end of file
+    [ compute-defs ] [ compute-uses ] [ compute-insns ] tri ;
diff --git a/basis/compiler/cfg/ssa/destruction/destruction.factor b/basis/compiler/cfg/ssa/destruction/destruction.factor
index b251578bc8..535dc6db86 100644
--- a/basis/compiler/cfg/ssa/destruction/destruction.factor
+++ b/basis/compiler/cfg/ssa/destruction/destruction.factor
@@ -8,7 +8,7 @@ compiler.cfg.def-use
 compiler.cfg.renaming
 compiler.cfg.dominance
 compiler.cfg.instructions
-compiler.cfg.liveness.ssa
+compiler.cfg.ssa.liveness
 compiler.cfg.ssa.cssa
 compiler.cfg.ssa.interference
 compiler.cfg.ssa.interference.live-ranges
@@ -97,11 +97,11 @@ M: insn prepare-insn drop ;
 : destruct-ssa ( cfg -- cfg' )
     dup cfg-has-phis? [
         dup construct-cssa
-        compute-ssa-live-sets
+        dup precompute-liveness
         dup compute-defs
         dup compute-dominance
         dup compute-live-ranges
         dup prepare-coalescing
         process-copies
         dup perform-renaming
-    ] when ;
\ No newline at end of file
+    ] when ;
diff --git a/basis/compiler/cfg/ssa/interference/interference-tests.factor b/basis/compiler/cfg/ssa/interference/interference-tests.factor
index f8876755d9..9075d3b010 100644
--- a/basis/compiler/cfg/ssa/interference/interference-tests.factor
+++ b/basis/compiler/cfg/ssa/interference/interference-tests.factor
@@ -1,6 +1,6 @@
 USING: accessors compiler.cfg compiler.cfg.debugger
 compiler.cfg.def-use compiler.cfg.dominance
-compiler.cfg.instructions compiler.cfg.liveness.ssa
+compiler.cfg.instructions compiler.cfg.ssa.liveness
 compiler.cfg.registers compiler.cfg.predecessors
 compiler.cfg.ssa.interference
 compiler.cfg.ssa.interference.live-ranges cpu.architecture
@@ -9,8 +9,8 @@ IN: compiler.cfg.ssa.interference.tests
 
 : test-interference ( -- )
     cfg new 0 get >>entry
-    compute-ssa-live-sets
     compute-predecessors
+    dup precompute-liveness
     dup compute-defs
     dup compute-dominance
     compute-live-ranges ;
@@ -49,4 +49,4 @@ V{
 [ t ] [ V int-regs 3 V int-regs 5 vregs-interfere? ] unit-test
 [ t ] [ V int-regs 5 V int-regs 3 vregs-interfere? ] unit-test
 [ f ] [ V int-regs 3 V int-regs 6 vregs-interfere? ] unit-test
-[ f ] [ V int-regs 6 V int-regs 3 vregs-interfere? ] unit-test
\ No newline at end of file
+[ f ] [ V int-regs 6 V int-regs 3 vregs-interfere? ] unit-test
diff --git a/basis/compiler/cfg/ssa/interference/live-ranges/live-ranges.factor b/basis/compiler/cfg/ssa/interference/live-ranges/live-ranges.factor
index 151af8bea4..c29b69cf36 100644
--- a/basis/compiler/cfg/ssa/interference/live-ranges/live-ranges.factor
+++ b/basis/compiler/cfg/ssa/interference/live-ranges/live-ranges.factor
@@ -2,7 +2,7 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors assocs fry kernel namespaces sequences math
 arrays compiler.cfg.def-use compiler.cfg.instructions
-compiler.cfg.liveness.ssa compiler.cfg.rpo ;
+compiler.cfg.ssa.liveness compiler.cfg.rpo ;
 IN: compiler.cfg.ssa.interference.live-ranges
 
 ! Live ranges for interference testing
diff --git a/basis/compiler/cfg/ssa/liveness/liveness.factor b/basis/compiler/cfg/ssa/liveness/liveness.factor
index 8788bc72f5..f2a195eb24 100644
--- a/basis/compiler/cfg/ssa/liveness/liveness.factor
+++ b/basis/compiler/cfg/ssa/liveness/liveness.factor
@@ -97,31 +97,15 @@ SYMBOL: phi-outs
     H{ } T_q-sets set
     [ next-T_q drop ] each-basic-block ;
 
-:: compute-phi-uses ( cfg -- )
-    ! Here, a phi node uses its argument in the block that it comes from.
-    H{ } clone :> use
-    cfg [| block |
-        block instructions>> [
-            dup ##phi?
-            [ inputs>> [ use conjoin-at ] assoc-each ]
-            [ uses-vregs [ block swap use conjoin-at ] each ]
-            if
-        ] each
-    ] each-basic-block
-    use [ keys ] assoc-map uses set ;
-
 PRIVATE>
 
 : precompute-liveness ( cfg -- )
-    ! The first three of these depend only on the graph
-    ! structure of the CFG, and don't need to be recomputed
-    ! if that doesn't change
+    ! Maybe dominance and def-use should be called before this, separately
     {
+        [ compute-dominance ]
+        [ compute-def-use ]
         [ compute-R_q ]
         [ compute-T_q ]
-        [ compute-dominance ]
-        [ compute-defs ]
-        [ compute-phi-uses ]
     } cleave ;
 
 <PRIVATE