diff --git a/basis/compiler/cfg/height/height.factor b/basis/compiler/cfg/height/height.factor
new file mode 100644
index 0000000000..d14cf4afb4
--- /dev/null
+++ b/basis/compiler/cfg/height/height.factor
@@ -0,0 +1,55 @@
+! Copyright (C) 2008 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+USING: accessors math namespaces sequences kernel fry
+compiler.cfg compiler.cfg.registers compiler.cfg.instructions
+compiler.cfg.instructions.syntax ;
+IN: compiler.cfg.height
+
+! Combine multiple stack height changes into one at the
+! start of the basic block.
+!
+! Alias analysis and value numbering assume this optimization
+! has been performed.
+
+SYMBOL: ds-height
+SYMBOL: rs-height
+
+GENERIC: compute-heights ( insn -- )
+
+M: ##inc-d compute-heights n>> ds-height [ + ] change ;
+M: ##inc-r compute-heights n>> rs-height [ + ] change ;
+M: insn compute-heights drop ;
+
+GENERIC: normalize-height* ( insn -- insn' )
+
+: normalize-inc-d/r ( insn stack -- insn' )
+    swap n>> '[ _ - ] change f ; inline
+
+M: ##inc-d normalize-height* ds-height normalize-inc-d/r ;
+M: ##inc-r normalize-height* rs-height normalize-inc-d/r ;
+
+GENERIC: loc-stack ( loc -- stack )
+
+M: ds-loc loc-stack drop ds-height ;
+M: rs-loc loc-stack drop rs-height ;
+
+GENERIC: <loc> ( n stack -- loc )
+
+M: ds-loc <loc> drop <ds-loc> ;
+M: rs-loc <loc> drop <rs-loc> ;
+
+: normalize-peek/replace ( insn -- insn' )
+    [ [ [ n>> ] [ loc-stack get ] bi + ] keep <loc> ] change-loc ; inline
+
+M: ##peek normalize-height* normalize-peek/replace ;
+M: ##replace normalize-height* normalize-peek/replace ;
+
+M: insn normalize-height* ;
+
+: normalize-height ( insns -- insns' )
+    0 ds-height set
+    0 rs-height set
+    [ [ compute-heights ] each ]
+    [ [ [ normalize-height* ] map sift ] with-scope ] bi
+    ds-height get dup zero? [ drop ] [ f \ ##inc-d boa prefix ] if
+    rs-height get dup zero? [ drop ] [ f \ ##inc-r boa prefix ] if ;