compiler.cfg.dominance: add pre order and max pre order numbers; use them to implement dominates? check

basis/compiler/cfg/dominance/dominance-tests.factor

@@ -6,7 +6,8 @@ compiler.cfg.predecessors ;
 : test-dominance ( -- )
     cfg new 0 get >>entry
     compute-predecessors
-    compute-dominance ;
+    dup compute-dominance
+    compute-dfs ;
 
 ! Example with no back edges
 V{ } 0 test-bb
@@ -38,6 +39,12 @@ V{ } 5 test-bb
 [ { } ] [ 0 get dom-frontier ] unit-test
 [ { } ] [ 4 get dom-frontier ] unit-test
 
+[ t ] [ 0 get 3 get dominates? ] unit-test
+[ f ] [ 3 get 4 get dominates? ] unit-test
+[ f ] [ 1 get 4 get dominates? ] unit-test
+[ t ] [ 4 get 5 get dominates? ] unit-test
+[ f ] [ 1 get 5 get dominates? ] unit-test
+
 ! Example from the paper
 V{ } 0 test-bb
 V{ } 1 test-bb

basis/compiler/cfg/dominance/dominance.factor

@@ -113,3 +113,29 @@ PRIVATE>
         work-list get [ iterated-dom-frontier-step ] slurp-deque
         visited get keys
     ] with-scope ;
+
+<PRIVATE
+
+SYMBOLS: preorder maxpreorder ;
+
+: pre-of ( bb -- n ) [ preorder get at ] [ -1/0. ] if* ;
+
+: maxpre-of ( bb -- n ) [ maxpreorder get at ] [ 1/0. ] if* ;
+
+: (compute-dfs) ( n bb -- n )
+    [ 1 + ] dip
+    [ dupd preorder get set-at ]
+    [ dom-children [ (compute-dfs) ] each ]
+    [ dupd maxpreorder get set-at ]
+    tri ;
+
+PRIVATE>
+
+: compute-dfs ( cfg -- )
+    H{ } clone preorder set
+    H{ } clone maxpreorder set
+    [ 0 ] dip entry>> (compute-dfs) drop ;
+
+: dominates? ( bb1 bb2 -- ? )
+    ! Requires DFS to be computed
+    swap [ pre-of ] [ [ pre-of ] [ maxpre-of ] bi ] bi* between? ;