compiler.cfg.linear-scan.ranges: merge adjacent ranges when adding them

this way, the number of live interval ranges you have to deal with is
much smaller

basis/compiler/cfg/linear-scan/ranges/ranges-docs.factor

@@ -1,6 +1,10 @@
-USING: arrays help.markup help.syntax math ;
+USING: arrays help.markup help.syntax math sequences ;
 IN: compiler.cfg.linear-scan.ranges
 
+HELP: add-range
+{ $values { "from" integer } { "to" integer } { "ranges" sequence } }
+{ $description "Adds the given range to the 'ranges' sequence, or extends the last range of it if it is possible." } ;
+
 HELP: intersect-range
 { $values
   { "range1" pair }

basis/compiler/cfg/linear-scan/ranges/ranges-tests.factor

@@ -9,27 +9,19 @@ IN: compiler.cfg.linear-scan.ranges.tests
     10 20 V{ } [ add-new-range ] keep
 ] unit-test
 
-! extend-ranges
+! extend-last?
-{
-    V{ { 7 25 } }
-} [
-    7 25 V{ { 10 20 } } [ extend-ranges ] keep
-] unit-test
-
-! extend-ranges?
 { f } [
-    10 { } extend-ranges?
+    10 { } extend-last?
 ] unit-test
 
 ! add-range
 {
+    V{ { 3 10 } }
     V{ { 5 12 } }
     V{ { 5 12 } }
-    V{ { 10 12 } { 5 9 } }
 } [
-    8 12 V{ { 5 10 } } [ add-range ] keep
+    3 9 V{ { 5 10 } } [ add-range ] keep
     5 10 V{ { 10 12 } } [ add-range ] keep
-
     5 9 V{ { 10 12 } } [ add-range ] keep
 ] unit-test
 

basis/compiler/cfg/linear-scan/ranges/ranges.factor

@@ -11,17 +11,16 @@ IN: compiler.cfg.linear-scan.ranges
     swap first2 pick 1 + [ swap 2array ] 2bi@  ;
 
 ! Range sequence utilities
-: extend-ranges? ( n ranges -- ? )
-    [ drop f ] [ last first >= ] if-empty ;
-
-: extend-ranges ( from to ranges -- )
-    [ last first2 rot [ min ] [ max ] 2bi* 2array ] keep set-last ;
-
 : add-new-range ( from to ranges -- )
     [ 2array ] dip push ;
 
+: extend-last? ( to ranges -- ? )
+    [ drop f ] [ last first 1 - >= ] if-empty ;
+
 : add-range ( from to ranges -- )
-    2dup extend-ranges? [ extend-ranges ] [ add-new-range ] if ;
+    2dup extend-last? [
+        [ nip last second 2array ] keep set-last
+    ] [ add-new-range ] if ;
 
 : ranges-cover? ( n ranges -- ? )
     [ first2 between? ] with any? ;