diff --git a/basis/compiler/compiler.factor b/basis/compiler/compiler.factor
index e58cf0c834..161b6a4896 100755
--- a/basis/compiler/compiler.factor
+++ b/basis/compiler/compiler.factor
@@ -12,6 +12,8 @@ compiler.errors compiler.units compiler.utilities
 compiler.tree.builder
 compiler.tree.optimizer
 
+compiler.crossref
+
 compiler.cfg
 compiler.cfg.builder
 compiler.cfg.optimizer
@@ -193,6 +195,14 @@ M: optimizing-compiler recompile ( words -- alist )
     ] with-scope
     "--- compile done" compiler-message ;
 
+M: optimizing-compiler to-recompile ( -- words )
+    changed-definitions get compiled-usages
+    changed-generics get compiled-generic-usages
+    append assoc-combine keys ;
+
+M: optimizing-compiler process-forgotten-words
+    [ delete-compiled-xref ] each ;
+
 : with-optimizer ( quot -- )
     [ optimizing-compiler compiler-impl ] dip with-variable ; inline
 
diff --git a/basis/compiler/crossref/authors.txt b/basis/compiler/crossref/authors.txt
new file mode 100644
index 0000000000..1901f27a24
--- /dev/null
+++ b/basis/compiler/crossref/authors.txt
@@ -0,0 +1 @@
+Slava Pestov
diff --git a/basis/compiler/crossref/crossref.factor b/basis/compiler/crossref/crossref.factor
new file mode 100644
index 0000000000..f3b65ce151
--- /dev/null
+++ b/basis/compiler/crossref/crossref.factor
@@ -0,0 +1,67 @@
+! Copyright (C) 2009 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+USING: assocs classes.algebra compiler.units definitions graphs
+grouping kernel namespaces sequences words stack-checker.state ;
+IN: compiler.crossref
+
+SYMBOL: compiled-crossref
+
+compiled-crossref [ H{ } clone ] initialize
+
+SYMBOL: compiled-generic-crossref
+
+compiled-generic-crossref [ H{ } clone ] initialize
+
+: compiled-usage ( word -- assoc )
+    compiled-crossref get at ;
+
+: (compiled-usages) ( word -- assoc )
+    #! If the word is not flushable anymore, we have to recompile
+    #! all words which flushable away a call (presumably when the
+    #! word was still flushable). If the word is flushable, we
+    #! don't have to recompile words that folded this away.
+    [ compiled-usage ]
+    [ "flushable" word-prop inlined-dependency flushed-dependency ? ] bi
+    [ dependency>= nip ] curry assoc-filter ;
+
+: compiled-usages ( seq -- assocs )
+    [ drop word? ] assoc-filter
+    [ [ drop (compiled-usages) ] { } assoc>map ] keep suffix ;
+
+: compiled-generic-usage ( word -- assoc )
+    compiled-generic-crossref get at ;
+
+: (compiled-generic-usages) ( generic class -- assoc )
+    [ compiled-generic-usage ] dip
+    [
+        2dup [ valid-class? ] both?
+        [ classes-intersect? ] [ 2drop f ] if nip
+    ] curry assoc-filter ;
+
+: compiled-generic-usages ( assoc -- assocs )
+    [ (compiled-generic-usages) ] { } assoc>map ;
+
+: (compiled-xref) ( word dependencies word-prop variable -- )
+    [ [ concat ] dip set-word-prop ] [ get add-vertex* ] bi-curry* 2bi ;
+
+: compiled-xref ( word dependencies generic-dependencies -- )
+    [ [ drop crossref? ] { } assoc-filter-as ] bi@
+    [ "compiled-uses" compiled-crossref (compiled-xref) ]
+    [ "compiled-generic-uses" compiled-generic-crossref (compiled-xref) ]
+    bi-curry* bi ;
+
+: (compiled-unxref) ( word word-prop variable -- )
+    [ [ [ dupd word-prop 2 <groups> ] dip get remove-vertex* ] 2curry ]
+    [ drop [ remove-word-prop ] curry ]
+    2bi bi ;
+
+: compiled-unxref ( word -- )
+    [ "compiled-uses" compiled-crossref (compiled-unxref) ]
+    [ "compiled-generic-uses" compiled-generic-crossref (compiled-unxref) ]
+    bi ;
+
+: delete-compiled-xref ( word -- )
+    [ compiled-unxref ]
+    [ compiled-crossref get delete-at ]
+    [ compiled-generic-crossref get delete-at ]
+    tri ;
diff --git a/basis/compiler/tests/redefine3.factor b/basis/compiler/tests/redefine3.factor
index 67added49d..913111b8ea 100644
--- a/basis/compiler/tests/redefine3.factor
+++ b/basis/compiler/tests/redefine3.factor
@@ -1,6 +1,6 @@
 USING: accessors compiler compiler.units tools.test math parser
 kernel sequences sequences.private classes.mixin generic
-definitions arrays words assocs eval ;
+definitions arrays words assocs eval grouping ;
 IN: compiler.tests.redefine3
 
 GENERIC: sheeple ( obj -- x )
@@ -13,20 +13,23 @@ M: empty-mixin sheeple drop "wake up" ; inline
 
 : sheeple-test ( -- string ) { } sheeple ;
 
+: compiled-use? ( key word -- ? )
+    "compiled-uses" word-prop 2 <groups> key? ;
+
 [ "sheeple" ] [ sheeple-test ] unit-test
 [ t ] [ \ sheeple-test optimized? ] unit-test
-[ t ] [ object \ sheeple method \ sheeple-test "compiled-uses" word-prop key? ] unit-test
-[ f ] [ empty-mixin \ sheeple method \ sheeple-test "compiled-uses" word-prop key? ] unit-test
+[ t ] [ object \ sheeple method \ sheeple-test compiled-use? ] unit-test
+[ f ] [ empty-mixin \ sheeple method \ sheeple-test compiled-use? ] unit-test
 
 [ ] [ "IN: compiler.tests.redefine3 USE: arrays INSTANCE: array empty-mixin" eval( -- ) ] unit-test
 
 [ "wake up" ] [ sheeple-test ] unit-test
-[ f ] [ object \ sheeple method \ sheeple-test "compiled-uses" word-prop key? ] unit-test
-[ t ] [ empty-mixin \ sheeple method \ sheeple-test "compiled-uses" word-prop key? ] unit-test
+[ f ] [ object \ sheeple method \ sheeple-test compiled-use? ] unit-test
+[ t ] [ empty-mixin \ sheeple method \ sheeple-test compiled-use? ] unit-test
 
 [ ] [ [ array empty-mixin remove-mixin-instance ] with-compilation-unit ] unit-test
 
 [ "sheeple" ] [ sheeple-test ] unit-test
 [ t ] [ \ sheeple-test optimized? ] unit-test
-[ t ] [ object \ sheeple method \ sheeple-test "compiled-uses" word-prop key? ] unit-test
-[ f ] [ empty-mixin \ sheeple method \ sheeple-test "compiled-uses" word-prop key? ] unit-test
+[ t ] [ object \ sheeple method \ sheeple-test compiled-use? ] unit-test
+[ f ] [ empty-mixin \ sheeple method \ sheeple-test compiled-use? ] unit-test
diff --git a/basis/fry/fry.factor b/basis/fry/fry.factor
index 60c76b726f..931397e933 100644
--- a/basis/fry/fry.factor
+++ b/basis/fry/fry.factor
@@ -38,12 +38,15 @@ INSTANCE: fried-callable fried
         [ [ \ 3curry suffix! ] dip 3 - (ncurry) ]
     } case ;
 
+: wrap-non-callable ( obj -- quot )
+    dup callable? [ ] [ [ call ] curry ] if ; inline
+
 : [ncurry] ( n -- quot )
     [ V{ } clone ] dip (ncurry) >quotation ;
 
 : [ndip] ( quot n -- quot' )
     {
-        { 0 [ ] }
+        { 0 [ wrap-non-callable ] }
         { 1 [ \ dip  [ ] 2sequence ] }
         { 2 [ \ 2dip [ ] 2sequence ] }
         { 3 [ \ 3dip [ ] 2sequence ] }
diff --git a/basis/io/files/info/windows/windows.factor b/basis/io/files/info/windows/windows.factor
index 6bd3f77ffa..9f0e4534e9 100755
--- a/basis/io/files/info/windows/windows.factor
+++ b/basis/io/files/info/windows/windows.factor
@@ -177,7 +177,7 @@ M: winnt file-system-info ( path -- file-system-info )
     handle buf buf-length FindNextVolume :> ret
     ret 0 = [
         GetLastError ERROR_NO_MORE_FILES =
-        [ drop f ] [ win32-error-string throw ] if
+        [ f ] [ win32-error-string throw ] if
     ] [
         buf utf16n alien>string
     ] if ;
diff --git a/basis/locals/locals-tests.factor b/basis/locals/locals-tests.factor
index 581ed5de33..7aa8032cdd 100644
--- a/basis/locals/locals-tests.factor
+++ b/basis/locals/locals-tests.factor
@@ -389,7 +389,7 @@ M:: integer lambda-method-forget-test ( a -- b ) a ;
     eval( -- ) call
 ] [ error>> >r/r>-in-fry-error? ] must-fail-with
     
-:: (funny-macro-test) ( obj quot -- ? ) obj { quot } 1&& ; inline
+:: (funny-macro-test) ( obj quot -- ? ) obj { [ quot call ] } 1&& ; inline
 : funny-macro-test ( n -- ? ) [ odd? ] (funny-macro-test) ;
 
 \ funny-macro-test def>> must-infer
diff --git a/basis/stack-checker/state/state-tests.factor b/basis/stack-checker/state/state-tests.factor
index a4dea993c0..4ecb39e592 100644
--- a/basis/stack-checker/state/state-tests.factor
+++ b/basis/stack-checker/state/state-tests.factor
@@ -28,3 +28,11 @@ SYMBOL: b
         b inlined-dependency depends-on
     ] computing-dependencies
 ] unit-test
+
+[ flushed-dependency ] [ f flushed-dependency strongest-dependency ] unit-test
+[ flushed-dependency ] [ flushed-dependency f strongest-dependency ] unit-test
+[ inlined-dependency ] [ flushed-dependency inlined-dependency strongest-dependency ] unit-test
+[ inlined-dependency ] [ called-dependency inlined-dependency strongest-dependency ] unit-test
+[ flushed-dependency ] [ called-dependency flushed-dependency strongest-dependency ] unit-test
+[ called-dependency ] [ called-dependency f strongest-dependency ] unit-test
+
diff --git a/basis/stack-checker/state/state.factor b/basis/stack-checker/state/state.factor
index a76d302a7e..bd9c57efbc 100644
--- a/basis/stack-checker/state/state.factor
+++ b/basis/stack-checker/state/state.factor
@@ -48,6 +48,18 @@ SYMBOL: literals
 ! Words that the current quotation depends on
 SYMBOL: dependencies
 
+SYMBOLS: inlined-dependency flushed-dependency called-dependency ;
+
+: index>= ( obj1 obj2 seq -- ? )
+    [ index ] curry bi@ >= ;
+
+: dependency>= ( how1 how2 -- ? )
+    { called-dependency flushed-dependency inlined-dependency }
+    index>= ;
+
+: strongest-dependency ( how1 how2 -- how )
+    [ called-dependency or ] bi@ [ dependency>= ] most ;
+
 : depends-on ( word how -- )
     over primitive? [ 2drop ] [
         dependencies get dup [
diff --git a/basis/tools/deploy/shaker/shaker.factor b/basis/tools/deploy/shaker/shaker.factor
index e42f478de6..856b99fd98 100755
--- a/basis/tools/deploy/shaker/shaker.factor
+++ b/basis/tools/deploy/shaker/shaker.factor
@@ -9,6 +9,7 @@ compiler.units definitions generic generic.standard
 generic.single tools.deploy.config combinators classes
 classes.builtin slots.private grouping command-line ;
 QUALIFIED: bootstrap.stage2
+QUALIFIED: compiler.crossref
 QUALIFIED: compiler.errors
 QUALIFIED: continuations
 QUALIFIED: definitions
@@ -340,8 +341,8 @@ IN: tools.deploy.shaker
                 implementors-map
                 update-map
                 main-vocab-hook
-                compiled-crossref
-                compiled-generic-crossref
+                compiler.crossref:compiled-crossref
+                compiler.crossref:compiled-generic-crossref
                 compiler-impl
                 compiler.errors:compiler-errors
                 lexer-factory
diff --git a/basis/tools/profiler/profiler.factor b/basis/tools/profiler/profiler.factor
index 626fdab826..8279a90514 100644
--- a/basis/tools/profiler/profiler.factor
+++ b/basis/tools/profiler/profiler.factor
@@ -1,9 +1,10 @@
 ! Copyright (C) 2007, 2008 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: accessors words sequences math prettyprint kernel arrays io
-io.styles namespaces assocs kernel.private strings combinators
-sorting math.parser vocabs definitions tools.profiler.private
-tools.crossref continuations generic compiler.units sets classes fry ;
+USING: accessors words sequences math prettyprint kernel arrays
+io io.styles namespaces assocs kernel.private strings
+combinators sorting math.parser vocabs definitions
+tools.profiler.private tools.crossref continuations generic
+compiler.units compiler.crossref sets classes fry ;
 IN: tools.profiler
 
 : profile ( quot -- )
diff --git a/core/compiler/units/units-tests.factor b/core/compiler/units/units-tests.factor
index 8dce12f411..c827d370d5 100644
--- a/core/compiler/units/units-tests.factor
+++ b/core/compiler/units/units-tests.factor
@@ -5,13 +5,6 @@ IN: compiler.units.tests
 [ [ [ ] define-temp ] with-compilation-unit ] must-infer
 [ [ [ ] define-temp ] with-nested-compilation-unit ] must-infer
 
-[ flushed-dependency ] [ f flushed-dependency strongest-dependency ] unit-test
-[ flushed-dependency ] [ flushed-dependency f strongest-dependency ] unit-test
-[ inlined-dependency ] [ flushed-dependency inlined-dependency strongest-dependency ] unit-test
-[ inlined-dependency ] [ called-dependency inlined-dependency strongest-dependency ] unit-test
-[ flushed-dependency ] [ called-dependency flushed-dependency strongest-dependency ] unit-test
-[ called-dependency ] [ called-dependency f strongest-dependency ] unit-test
-
 ! Non-optimizing compiler bugs
 [ 1 1 ] [
     "A" "B" <word> [ [ [ 1 ] dip ] 2array 1array modify-code-heap ] keep
diff --git a/core/compiler/units/units.factor b/core/compiler/units/units.factor
index 8b6625d014..eb7cc7b5d2 100644
--- a/core/compiler/units/units.factor
+++ b/core/compiler/units/units.factor
@@ -40,8 +40,19 @@ SYMBOL: compiler-impl
 
 HOOK: recompile compiler-impl ( words -- alist )
 
+HOOK: to-recompile compiler-impl ( -- words )
+
+HOOK: process-forgotten-words compiler-impl ( words -- )
+
 ! Non-optimizing compiler
-M: f recompile [ dup def>> ] { } map>assoc ;
+M: f recompile
+    [ dup def>> ] { } map>assoc ;
+
+M: f to-recompile
+    changed-definitions get [ drop word? ] assoc-filter
+    changed-generics get assoc-union keys ;
+
+M: f process-forgotten-words drop ;
 
 : without-optimizer ( quot -- )
     [ f compiler-impl ] dip with-variable ; inline
@@ -50,8 +61,12 @@ M: f recompile [ dup def>> ] { } map>assoc ;
 ! during stage1 bootstrap, it would just waste time.
 SINGLETON: dummy-compiler
 
+M: dummy-compiler to-recompile f ;
+
 M: dummy-compiler recompile drop { } ;
 
+M: dummy-compiler process-forgotten-words drop ;
+
 : <definitions> ( -- pair ) { H{ } H{ } } [ clone ] map ;
 
 SYMBOL: definition-observers
@@ -89,59 +104,9 @@ GENERIC: definitions-changed ( assoc obj -- )
 
 : compile ( words -- ) recompile modify-code-heap ;
 
-: index>= ( obj1 obj2 seq -- ? )
-    [ index ] curry bi@ >= ;
-
-: dependency>= ( how1 how2 -- ? )
-    { called-dependency flushed-dependency inlined-dependency }
-    index>= ;
-
-: strongest-dependency ( how1 how2 -- how )
-    [ called-dependency or ] bi@ [ dependency>= ] most ;
-
-: weakest-dependency ( how1 how2 -- how )
-    [ inlined-dependency or ] bi@ [ dependency>= not ] most ;
-
-: compiled-usage ( word -- assoc )
-    compiled-crossref get at ;
-
-: (compiled-usages) ( word -- assoc )
-    #! If the word is not flushable anymore, we have to recompile
-    #! all words which flushable away a call (presumably when the
-    #! word was still flushable). If the word is flushable, we
-    #! don't have to recompile words that folded this away.
-    [ compiled-usage ]
-    [ "flushable" word-prop inlined-dependency flushed-dependency ? ] bi
-    [ dependency>= nip ] curry assoc-filter ;
-
-: compiled-usages ( assoc -- assocs )
-    [ drop word? ] assoc-filter
-    [ [ drop (compiled-usages) ] { } assoc>map ] keep suffix ;
-
-: compiled-generic-usage ( word -- assoc )
-    compiled-generic-crossref get at ;
-
-: (compiled-generic-usages) ( generic class -- assoc )
-    [ compiled-generic-usage ] dip
-    [
-        2dup [ valid-class? ] both?
-        [ classes-intersect? ] [ 2drop f ] if nip
-    ] curry assoc-filter ;
-
-: compiled-generic-usages ( assoc -- assocs )
-    [ (compiled-generic-usages) ] { } assoc>map ;
-
-: words-only ( assoc -- assoc' )
-    [ drop word? ] assoc-filter ;
-
-: to-recompile ( -- seq )
-    changed-definitions get compiled-usages
-    changed-generics get compiled-generic-usages
-    append assoc-combine keys ;
-
 : process-forgotten-definitions ( -- )
     forgotten-definitions get keys
-    [ [ word? ] filter [ delete-compiled-xref ] each ]
+    [ [ word? ] filter process-forgotten-words ]
     [ [ delete-definition-errors ] each ]
     bi ;
 
diff --git a/core/definitions/definitions.factor b/core/definitions/definitions.factor
index e2fb4b8161..d815b9609d 100644
--- a/core/definitions/definitions.factor
+++ b/core/definitions/definitions.factor
@@ -7,15 +7,13 @@ MIXIN: definition
 
 ERROR: no-compilation-unit definition ;
 
-SYMBOLS: inlined-dependency flushed-dependency called-dependency ;
-
 : set-in-unit ( value key assoc -- )
     [ set-at ] [ no-compilation-unit ] if* ;
 
 SYMBOL: changed-definitions
 
 : changed-definition ( defspec -- )
-    inlined-dependency swap changed-definitions get set-in-unit ;
+    dup changed-definitions get set-in-unit ;
 
 SYMBOL: changed-effects
 
diff --git a/core/generic/generic-tests.factor b/core/generic/generic-tests.factor
index f5c2018e60..5a98173a89 100755
--- a/core/generic/generic-tests.factor
+++ b/core/generic/generic-tests.factor
@@ -3,7 +3,8 @@ classes.tuple classes.union compiler.units continuations
 definitions eval generic generic.math generic.standard
 hashtables io io.streams.string kernel layouts math math.order
 namespaces parser prettyprint quotations sequences sorting
-strings tools.test vectors words generic.single ;
+strings tools.test vectors words generic.single
+compiler.crossref ;
 IN: generic.tests
 
 GENERIC: foobar ( x -- y )
diff --git a/core/vocabs/loader/loader-docs.factor b/core/vocabs/loader/loader-docs.factor
index 352ccdebd4..02a604ac32 100644
--- a/core/vocabs/loader/loader-docs.factor
+++ b/core/vocabs/loader/loader-docs.factor
@@ -102,7 +102,7 @@ HELP: load-docs
 
 HELP: reload
 { $values { "name" "a vocabulary name" } }
-{ $description "Loads it's source code and documentation." }
+{ $description "Reloads the source code and documentation for a vocabulary." }
 { $errors "Throws a " { $link no-vocab } " error if the vocabulary does not exist on disk." } ;
 
 HELP: require
diff --git a/core/words/words-tests.factor b/core/words/words-tests.factor
index b9d6e80630..fec9c14830 100755
--- a/core/words/words-tests.factor
+++ b/core/words/words-tests.factor
@@ -1,7 +1,7 @@
 USING: arrays generic assocs kernel math namespaces
 sequences tools.test words definitions parser quotations
 vocabs continuations classes.tuple compiler.units
-io.streams.string accessors eval words.symbol ;
+io.streams.string accessors eval words.symbol grouping ;
 IN: words.tests
 
 [ 4 ] [
@@ -121,7 +121,7 @@ DEFER: x
 [ { } ]
 [
     all-words [
-        "compiled-uses" word-prop
+        "compiled-uses" word-prop 2 <groups>
         keys [ "forgotten" word-prop ] filter
     ] map harvest
 ] unit-test
diff --git a/core/words/words.factor b/core/words/words.factor
index 45e014f6be..d2fe7d2625 100755
--- a/core/words/words.factor
+++ b/core/words/words.factor
@@ -64,41 +64,6 @@ GENERIC: crossref? ( word -- ? )
 M: word crossref?
     dup "forgotten" word-prop [ drop f ] [ vocabulary>> >boolean ] if ;
 
-SYMBOL: compiled-crossref
-
-compiled-crossref [ H{ } clone ] initialize
-
-SYMBOL: compiled-generic-crossref
-
-compiled-generic-crossref [ H{ } clone ] initialize
-
-: (compiled-xref) ( word dependencies word-prop variable -- )
-    [ [ set-word-prop ] curry ]
-    [ [ get add-vertex* ] curry ]
-    bi* 2bi ;
-
-: compiled-xref ( word dependencies generic-dependencies -- )
-    [ [ drop crossref? ] { } assoc-filter-as f like ] bi@
-    [ "compiled-uses" compiled-crossref (compiled-xref) ]
-    [ "compiled-generic-uses" compiled-generic-crossref (compiled-xref) ]
-    bi-curry* bi ;
-
-: (compiled-unxref) ( word word-prop variable -- )
-    [ [ [ dupd word-prop ] dip get remove-vertex* ] 2curry ]
-    [ drop [ remove-word-prop ] curry ]
-    2bi bi ;
-
-: compiled-unxref ( word -- )
-    [ "compiled-uses" compiled-crossref (compiled-unxref) ]
-    [ "compiled-generic-uses" compiled-generic-crossref (compiled-unxref) ]
-    bi ;
-
-: delete-compiled-xref ( word -- )
-    [ compiled-unxref ]
-    [ compiled-crossref get delete-at ]
-    [ compiled-generic-crossref get delete-at ]
-    tri ;
-
 : inline? ( word -- ? ) "inline" word-prop ; inline
 
 GENERIC: subwords ( word -- seq )
diff --git a/extra/vocabs/git/authors.txt b/extra/vocabs/git/authors.txt
new file mode 100644
index 0000000000..f13c9c1e77
--- /dev/null
+++ b/extra/vocabs/git/authors.txt
@@ -0,0 +1 @@
+Joe Groff
diff --git a/extra/vocabs/git/git.factor b/extra/vocabs/git/git.factor
new file mode 100644
index 0000000000..eb945b57c7
--- /dev/null
+++ b/extra/vocabs/git/git.factor
@@ -0,0 +1,28 @@
+! (c)2009 Joe Groff bsd license
+USING: fry io io.directories io.encodings.ascii
+io.encodings.utf8 io.launcher io.pathnames kernel lexer
+namespaces parser sequences splitting vocabs vocabs.loader ;
+IN: vocabs.git
+
+<PRIVATE
+: git-object-id ( filename rev -- id/f )
+    [ [ parent-directory ] [ file-name ] bi ] dip swap '[
+        { "git" "ls-tree" } _ suffix _ suffix ascii [
+            readln
+            [ " " split1 nip " " split1 nip "\t" split1 drop ]
+            [ f ] if*
+        ] with-process-reader
+    ] with-directory ;
+
+: with-git-object-stream ( id quot -- )
+    [ { "git" "cat-file" "-p" } swap suffix utf8 ] dip with-process-reader ; inline
+PRIVATE>
+
+ERROR: git-revision-not-found path ;
+
+: use-vocab-rev ( vocab-name rev -- )
+    [ create-vocab vocab-source-path dup ] dip git-object-id 
+    [ [ input-stream get swap parse-stream call( -- ) ] with-git-object-stream ]
+    [ git-revision-not-found ] if* ;
+
+SYNTAX: USE-REV: scan scan use-vocab-rev ;
diff --git a/vm/bitwise_hacks.hpp b/vm/bitwise_hacks.hpp
index 03a6ea5ad0..6cd2a5b694 100644
--- a/vm/bitwise_hacks.hpp
+++ b/vm/bitwise_hacks.hpp
@@ -1,7 +1,29 @@
 namespace factor
 {
 
-/* These algorithms were snarfed from various places. I did not come up with them myself */
+inline cell log2(cell x)
+{
+	cell n;
+#if defined(FACTOR_X86) || defined(FACTOR_AMD64)
+	asm ("bsr %1, %0;":"=r"(n):"r"(x));
+#elif defined(FACTOR_PPC)
+	asm ("cntlzw %1, %0;":"=r"(n):"r"(x));
+	n = (31 - n);
+#else
+	#error Unsupported CPU
+#endif
+	return n;
+}
+
+inline cell rightmost_clear_bit(cell x)
+{
+	return log2(~x & (x + 1));
+}
+
+inline cell rightmost_set_bit(cell x)
+{
+	return log2(x & -x);
+}
 
 inline cell popcount(cell x)
 {
@@ -24,39 +46,7 @@ inline cell popcount(cell x)
 	x = (x       +  (x >> 4)) & k4 ; // put count of each 8 bits into those 8 bits
 	x = (x * kf) >> ks; // returns 8 most significant bits of x + (x<<8) + (x<<16) + (x<<24) + ...
 
-	return (cell)x;
-}
-
-inline cell log2(cell x)
-{
-#if defined(FACTOR_X86)
-	cell n;
-	asm ("bsr %1, %0;":"=r"(n):"r"(x));
-#elif defined(FACTOR_AMD64)
-	cell n;
-	asm ("bsr %1, %0;":"=r"(n):"r"(x));
-#else
-	cell n = 0;
-#ifdef FACTOR_64
-	if (x >= (cell)1 << 32) { x >>= 32; n += 32; }
-#endif
-	if (x >= (cell)1 << 16) { x >>= 16; n += 16; }
-	if (x >= (cell)1 <<  8) { x >>=  8; n +=  8; }
-	if (x >= (cell)1 <<  4) { x >>=  4; n +=  4; }
-	if (x >= (cell)1 <<  2) { x >>=  2; n +=  2; }
-	if (x >= (cell)1 <<  1) {           n +=  1; }
-#endif
-	return n;
-}
-
-inline cell rightmost_clear_bit(cell x)
-{
-	return log2(~x & (x + 1));
-}
-
-inline cell rightmost_set_bit(cell x)
-{
-	return log2(x & -x);
+	return x;
 }
 
 }
diff --git a/vm/contexts.cpp b/vm/contexts.cpp
index 16b882f2cc..f5fac1119e 100644
--- a/vm/contexts.cpp
+++ b/vm/contexts.cpp
@@ -3,6 +3,20 @@
 namespace factor
 {
 
+context::context(cell ds_size, cell rs_size) :
+	callstack_top(NULL),
+	callstack_bottom(NULL),
+	datastack(0),
+	retainstack(0),
+	datastack_save(0),
+	retainstack_save(0),
+	magic_frame(NULL),
+	datastack_region(new segment(ds_size,false)),
+	retainstack_region(new segment(rs_size,false)),
+	catchstack_save(0),
+	current_callback_save(0),
+	next(NULL) {}
+
 void factor_vm::reset_datastack()
 {
 	ds = ds_bot - sizeof(cell);
@@ -42,11 +56,7 @@ context *factor_vm::alloc_context()
 		unused_contexts = unused_contexts->next;
 	}
 	else
-	{
-		new_context = new context;
-		new_context->datastack_region = new segment(ds_size,false);
-		new_context->retainstack_region = new segment(rs_size,false);
-	}
+		new_context = new context(ds_size,rs_size);
 
 	return new_context;
 }
diff --git a/vm/contexts.hpp b/vm/contexts.hpp
index aa6f9ec8ce..ddbae5de78 100644
--- a/vm/contexts.hpp
+++ b/vm/contexts.hpp
@@ -46,6 +46,8 @@ struct context {
 	cell current_callback_save;
 
 	context *next;
+
+	context(cell ds_size, cell rs_size);
 };
 
 #define ds_bot (ctx->datastack_region->start)
diff --git a/vm/full_collector.cpp b/vm/full_collector.cpp
index 07c410218c..4edb23cf73 100644
--- a/vm/full_collector.cpp
+++ b/vm/full_collector.cpp
@@ -126,7 +126,7 @@ void factor_vm::collect_full(bool trace_contexts_p)
 {
 	collect_mark_impl(trace_contexts_p);
 	collect_sweep_impl();
-	if(data->tenured->largest_free_block() <= data->nursery->size + data->aging->size)
+	if(data->low_memory_p())
 		collect_compact_impl(trace_contexts_p);
 	else
 		update_code_heap_words_and_literals();