diff --git a/unfinished/compiler/tree/debugger/debugger-tests.factor b/unfinished/compiler/tree/debugger/debugger-tests.factor
new file mode 100644
index 0000000000..e6a4385c3e
--- /dev/null
+++ b/unfinished/compiler/tree/debugger/debugger-tests.factor
@@ -0,0 +1,6 @@
+IN: compiler.tree.debugger.tests
+USING: compiler.tree.debugger tools.test ;
+
+\ optimized-quot. must-infer
+\ optimized-word. must-infer
+\ optimizer-report. must-infer
diff --git a/unfinished/compiler/tree/debugger/debugger.factor b/unfinished/compiler/tree/debugger/debugger.factor
new file mode 100644
index 0000000000..804d6ea240
--- /dev/null
+++ b/unfinished/compiler/tree/debugger/debugger.factor
@@ -0,0 +1,141 @@
+! Copyright (C) 2006, 2008 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+USING: kernel assocs fry match accessors namespaces effects
+sequences sequences.private quotations generic macros arrays
+prettyprint prettyprint.backend prettyprint.sections math words
+combinators io sorting
+compiler.tree
+compiler.tree.builder
+compiler.tree.optimizer
+compiler.tree.combinators
+compiler.tree.propagation.info ;
+IN: compiler.tree.debugger
+
+! A simple tool for turning tree IR into quotations and
+! printing reports, for debugging purposes.
+
+GENERIC: node>quot ( node -- )
+
+MACRO: match-choose ( alist -- )
+    [ '[ , ] ] assoc-map '[ , match-cond ] ;
+
+MATCH-VARS: ?a ?b ?c ;
+
+: pretty-shuffle ( in out -- word/f )
+    2array {
+        { { { ?a } { ?a } } [ ] }
+        { { { ?a ?b } { ?a ?b } } [ ] }
+        { { { ?a ?b ?c } { ?a ?b ?c } } [ ] }
+        { { { ?a } { } } [ drop ] }
+        { { { ?a ?b } { } } [ 2drop ] }
+        { { { ?a ?b ?c } { } } [ 3drop ] }
+        { { { ?a } { ?a ?a } } [ dup ] }
+        { { { ?a ?b } { ?a ?b ?a ?b } } [ 2dup ] }
+        { { { ?a ?b ?c } { ?a ?b ?c ?a ?b ?c } } [ 3dup ] }
+        { { { ?a ?b } { ?a ?b ?a } } [ over ] }
+        { { { ?b ?a } { ?a ?b } } [ swap ] }
+        { { { ?a ?b } { ?b ?a ?b } } [ tuck ] }
+        { { { ?a ?b ?c } { ?a ?b ?c ?a } } [ pick ] }
+        { { { ?a ?b ?c } { ?c ?a ?b } } [ -rot ] }
+        { { { ?a ?b ?c } { ?b ?c ?a } } [ rot ] }
+        { { { ?a ?b } { ?b } } [ nip ] }
+        { { { ?a ?b ?c } { ?c } } [ 2nip ] }
+        { _ f }
+    } match-choose ;
+
+TUPLE: shuffle effect ;
+
+M: shuffle pprint* effect>> effect>string text ;
+
+: shuffle-inputs/outputs ( node -- in out )
+    [ in-d>> ] [ out-d>> ] [ mapping>> ] tri
+    [ at ] curry map ;
+
+M: #shuffle node>quot
+    shuffle-inputs/outputs 2dup pretty-shuffle dup
+    [ 2nip % ] [ drop <effect> shuffle boa , ] if ;
+
+: pushed-literals ( node -- seq )
+    dup out-d>> [ node-value-info literal>> literalize ] with map ;
+
+M: #push node>quot pushed-literals % ;
+
+M: #call node>quot word>> , ;
+
+M: #call-recursive node>quot label>> id>> , ;
+
+DEFER: nodes>quot
+
+DEFER: label
+
+M: #recursive node>quot
+    [ label>> id>> literalize , ]
+    [ child>> nodes>quot , \ label , ]
+    bi ;
+
+M: #if node>quot
+    children>> [ nodes>quot ] map % \ if , ;
+
+M: #dispatch node>quot
+    children>> [ nodes>quot ] map , \ dispatch , ;
+
+M: #>r node>quot in-d>> length \ >r <repetition> % ;
+
+M: #r> node>quot out-d>> length \ r> <repetition> % ;
+
+M: node node>quot drop ;
+
+: nodes>quot ( node -- quot )
+    [ [ node>quot ] each ] [ ] make ;
+
+: optimized-quot. ( quot -- )
+    dup word? [ specialized-def ] when
+    build-tree optimize-tree nodes>quot . ;
+
+SYMBOL: words-called
+SYMBOL: generics-called
+SYMBOL: methods-called
+SYMBOL: intrinsics-called
+SYMBOL: node-count
+
+: make-report ( word/quot -- assoc )
+    [
+        dup word? [ build-tree-from-word nip ] [ build-tree ] if
+        optimize-tree
+
+        H{ } clone words-called set
+        H{ } clone generics-called set
+        H{ } clone methods-called set
+        H{ } clone intrinsics-called set
+
+        0 swap [
+            >r 1+ r>
+            dup #call? [
+                word>> {
+                    { [ dup "intrinsics" word-prop over "if-intrinsics" word-prop or ] [ intrinsics-called ] }
+                    { [ dup generic? ] [ generics-called ] }
+                    { [ dup method-body? ] [ methods-called ] }
+                    [ words-called ]
+                } cond 1 -rot get at+
+            ] [ drop ] if
+        ] each-node
+        node-count set
+    ] H{ } make-assoc ;
+
+: report. ( report -- )
+    [
+        "==== Total number of IR nodes:" print
+        node-count get .
+
+        {
+            { generics-called "==== Generic word calls:" }
+            { words-called "==== Ordinary word calls:" }
+            { methods-called "==== Non-inlined method calls:" }
+            { intrinsics-called "==== Open-coded intrinsic calls:" }
+        } [
+            nl print get keys natural-sort stack.
+        ] assoc-each
+    ] bind ;
+
+: optimizer-report. ( word -- )
+    make-report report. ;
diff --git a/unfinished/compiler/tree/loop/inversion/inversion.factor b/unfinished/compiler/tree/loop/inversion/inversion.factor
new file mode 100644
index 0000000000..719fc4ad70
--- /dev/null
+++ b/unfinished/compiler/tree/loop/inversion/inversion.factor
@@ -0,0 +1,5 @@
+! Copyright (C) 2008 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+IN: compiler.tree.loop.inversion
+
+: invert-loops ( nodes -- nodes' ) ;
diff --git a/unfinished/compiler/tree/optimizer/optimizer-tests.factor b/unfinished/compiler/tree/optimizer/optimizer-tests.factor
new file mode 100644
index 0000000000..1075e441e7
--- /dev/null
+++ b/unfinished/compiler/tree/optimizer/optimizer-tests.factor
@@ -0,0 +1,4 @@
+USING: compiler.tree.optimizer tools.test ;
+IN: compiler.tree.optimizer.tests
+
+\ optimize-tree must-infer
diff --git a/unfinished/compiler/tree/optimizer/optimizer.factor b/unfinished/compiler/tree/optimizer/optimizer.factor
index 24df9b5af3..2d2a376bc0 100644
--- a/unfinished/compiler/tree/optimizer/optimizer.factor
+++ b/unfinished/compiler/tree/optimizer/optimizer.factor
@@ -9,6 +9,7 @@ compiler.tree.def-use
 compiler.tree.dead-code
 compiler.tree.strength-reduction
 compiler.tree.loop.detection
+compiler.tree.loop.inversion
 compiler.tree.branch-fusion ;
 IN: compiler.tree.optimizer