compiler alias analysis: Alternate function traversal order

Sharing state information flows from callers to callees for function
arguments, and from callees to callers for results. Previously callers
were always analyzed before callees, but it turns out that the alias
analysis converges faster if the traversal order is alternated between
caller-callee and callee-caller.

lib/compiler/src/beam_ssa_alias.erl

@@ -354,7 +354,7 @@ aa_fixpoint(Funs, AAS=#aas{func_db=FuncDb}) ->
     Order = aa_order(Funs, FuncDb),
     ?DP("Traversal order:~n  ~s~n",
         [string:join([fn(F) || F <- Order], ",\n  ")]),
-    aa_fixpoint(Order, Order, AAS, 1).
+    aa_fixpoint(Order, reverse(Order), AAS, 1).
 
 aa_fixpoint([F|Fs], Order,
             AAS0=#aas{func_db=FuncDb,st_map=StMap,
@@ -388,7 +388,7 @@ aa_fixpoint([], Order, #aas{func_db=FuncDb,repeats=Repeats}=AAS, NoofIters) ->
             {StMap, FuncDb};
         NewOrder ->
             ?DP("**** Starting traversal ~p ****~n", [NoofIters + 1]),
-            aa_fixpoint(NewOrder, Order,
+            aa_fixpoint(NewOrder, reverse(Order),
                         AAS#aas{repeats=sets:new()}, NoofIters + 1)
     end.