diff --git a/basis/compiler/cfg/linear-scan/assignment/assignment.factor b/basis/compiler/cfg/linear-scan/assignment/assignment.factor
index c0f90e5932..98deca9472 100644
--- a/basis/compiler/cfg/linear-scan/assignment/assignment.factor
+++ b/basis/compiler/cfg/linear-scan/assignment/assignment.factor
@@ -19,7 +19,7 @@ IN: compiler.cfg.linear-scan.assignment
 SYMBOL: pending-intervals
 
 : add-active ( live-interval -- )
-    pending-intervals get push ;
+    dup end>> pending-intervals get heap-push ;
 
 ! Minheap of live intervals which still need a register allocation
 SYMBOL: unhandled-intervals
@@ -37,7 +37,7 @@ SYMBOL: register-live-ins
 SYMBOL: register-live-outs
 
 : init-assignment ( live-intervals -- )
-    V{ } clone pending-intervals set
+    <min-heap> pending-intervals set
     <min-heap> unhandled-intervals set
     H{ } clone register-live-ins set
     H{ } clone register-live-outs set
@@ -61,12 +61,17 @@ SYMBOL: register-live-outs
         register->register
     ] [ drop ] if ;
 
+: (expire-old-intervals) ( n heap -- )
+    dup heap-empty? [ 2drop ] [
+        2dup heap-peek nip <= [ 2drop ] [
+            dup heap-pop drop [ handle-spill ] [ handle-copy ] bi
+            (expire-old-intervals)
+        ] if
+    ] if ;
+
 : expire-old-intervals ( n -- )
     [
-        [ pending-intervals get ] dip '[
-            dup end>> _ <
-            [ [ handle-spill ] [ handle-copy ] bi f ] [ drop t ] if
-        ] filter-here
+        pending-intervals get (expire-old-intervals)
     ] { } make mapping-instructions % ;
 
 : insert-reload ( live-interval -- )
@@ -111,14 +116,12 @@ ERROR: overlapping-registers intervals ;
     dup [ reg>> ] map all-unique? [ drop ] [ overlapping-registers ] if ;
 
 : active-intervals ( n -- intervals )
-    pending-intervals get [ covers? ] with filter
+    pending-intervals get heap-values [ covers? ] with filter
     check-assignment? get [ dup check-assignment ] when ;
 
 M: vreg-insn assign-registers-in-insn
-    dup [ all-vregs ] [ insn#>> active-intervals ] bi
-    '[ _ [ vreg>> = ] with find nip ] map
-    register-mapping
-    >>regs drop ;
+    dup [ all-vregs ] [ insn#>> active-intervals register-mapping ] bi
+    extract-keys >>regs drop ;
 
 M: ##gc assign-registers-in-insn
     ! This works because ##gc is always the first instruction
diff --git a/basis/compiler/cfg/linear-scan/live-intervals/live-intervals.factor b/basis/compiler/cfg/linear-scan/live-intervals/live-intervals.factor
index d2fa661136..68a780d42a 100644
--- a/basis/compiler/cfg/linear-scan/live-intervals/live-intervals.factor
+++ b/basis/compiler/cfg/linear-scan/live-intervals/live-intervals.factor
@@ -1,7 +1,7 @@
 ! Copyright (C) 2008, 2009 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: namespaces kernel assocs accessors sequences math math.order fry
-combinators compiler.cfg.instructions compiler.cfg.registers
+combinators binary-search compiler.cfg.instructions compiler.cfg.registers
 compiler.cfg.def-use compiler.cfg.liveness compiler.cfg ;
 IN: compiler.cfg.linear-scan.live-intervals
 
@@ -16,16 +16,21 @@ split-before split-after split-next
 start end ranges uses
 copy-from ;
 
-: covers? ( insn# live-interval -- ? )
-    ranges>> [ [ from>> ] [ to>> ] bi between? ] with any? ;
+GENERIC: covers? ( insn# obj -- ? )
 
-: child-interval-at ( insn# interval -- interval' )
-    dup split-after>> [
-        2dup split-after>> start>> <
-        [ split-before>> ] [ split-after>> ] if
-        child-interval-at
-    ] [ nip ] if ;
+M: f covers? 2drop f ;
 
+M: live-range covers? [ from>> ] [ to>> ] bi between? ;
+
+M: live-interval covers? ( insn# live-interval -- ? )
+    ranges>>
+    dup length 4 <= [
+        [ covers? ] with any?
+    ] [
+        [ drop ] [ [ from>> <=> ] with search nip ] 2bi
+        covers?
+    ] if ;
+        
 ERROR: dead-value-error vreg ;
 
 : shorten-range ( n live-interval -- )