Merge pull request #132 from aeternity/fate-compiler-optimizations

Fate compiler optimizations

src/aeso_fcode_to_fate.erl

@@ -114,13 +114,16 @@
      Op =:= 'CREATOR'              orelse
      false)).
 
--record(env, { contract, vars = [], locals = [], tailpos = true }).
+-record(env, { contract, vars = [], locals = [], current_function, tailpos = true }).
 
 %% -- Debugging --------------------------------------------------------------
 
-debug(Tag, Options, Fmt, Args) ->
+is_debug(Tag, Options) ->
     Tags = proplists:get_value(debug, Options, []),
-    case Tags == all orelse lists:member(Tag, Tags) of
+    Tags == all orelse lists:member(Tag, Tags).
+
+debug(Tag, Options, Fmt, Args) ->
+    case is_debug(Tag, Options) of
         true  -> io:format(Fmt, Args);
         false -> ok
     end.
@@ -154,10 +157,10 @@ functions_to_scode(ContractName, Functions, Options) ->
                     attrs  := Attrs,
                     return := Type}} <- maps:to_list(Functions)]).
 
-function_to_scode(ContractName, Functions, _Name, Attrs0, Args, Body, ResType, _Options) ->
+function_to_scode(ContractName, Functions, Name, Attrs0, Args, Body, ResType, _Options) ->
     {ArgTypes, ResType1} = typesig_to_scode(Args, ResType),
     Attrs = Attrs0 -- [stateful], %% Only track private and payable from here.
-    SCode = to_scode(init_env(ContractName, Functions, Args), Body),
+    SCode = to_scode(init_env(ContractName, Functions, Name, Args), Body),
     {Attrs, {ArgTypes, ResType1}, SCode}.
 
 -define(tvars, '$tvars').
@@ -199,10 +202,11 @@ type_to_scode({tvar, X}) ->
 
 %% -- Environment functions --
 
-init_env(ContractName, FunNames, Args) ->
+init_env(ContractName, FunNames, Name, Args) ->
     #env{ vars      = [ {X, {arg, I}} || {I, {X, _}} <- with_ixs(Args) ],
           contract  = ContractName,
           locals    = FunNames,
+          current_function = Name,
           tailpos   = true }.
 
 next_var(#env{ vars = Vars }) ->
@@ -305,6 +309,24 @@ to_scode(Env, {'let', X, Expr, Body}) ->
       aeb_fate_ops:store({var, I}, {stack, 0}),
       to_scode(Env1, Body) ];
 
+to_scode(Env = #env{ current_function = Fun, tailpos = true }, {def, Fun, Args}) ->
+    %% Tail-call to current function, f(e0..en). Compile to
+    %%      [ let xi = ei ]
+    %%      [ STORE argi xi ]
+    %%      jump 0
+    {Vars, Code, _Env} =
+        lists:foldl(fun(Arg, {Is, Acc, Env1}) ->
+                        {I, Env2} = bind_local("_", Env1),
+                        ArgCode   = to_scode(notail(Env2), Arg),
+                        Acc1 = [Acc, ArgCode,
+                                aeb_fate_ops:store({var, I}, ?a)],
+                        {[I | Is], Acc1, Env2}
+                    end, {[], [], Env}, Args),
+    [ Code,
+      [ aeb_fate_ops:store({arg, I}, {var, J})
+        || {I, J} <- lists:zip(lists:seq(0, length(Vars) - 1),
+                               lists:reverse(Vars)) ],
+      loop ];
 to_scode(Env, {def, Fun, Args}) ->
     FName = make_function_id(Fun),
     Lbl   = aeb_fate_data:make_string(FName),
@@ -662,12 +684,15 @@ pp_ann(Ind, [{i, #{ live_in := In, live_out := Out }, I} | Code]) ->
     Fmt = fun([]) -> "()";
              (Xs) -> string:join([lists:concat(["var", N]) || {var, N} <- Xs], " ")
           end,
-    Op  = [Ind, aeb_fate_pp:format_op(I, #{})],
+    Op  = [Ind, pp_op(I)],
     Ann = [["   % ", Fmt(In), " -> ", Fmt(Out)] || In ++ Out /= []],
     [io_lib:format("~-40s~s\n", [Op, Ann]),
      pp_ann(Ind, Code)];
 pp_ann(_, []) -> [].
 
+pp_op(loop) -> "LOOP";
+pp_op(I)    ->
+    aeb_fate_pp:format_op(I, #{}).
 
 pp_arg(?i(I))    -> io_lib:format("~w", [I]);
 pp_arg({arg, N}) -> io_lib:format("arg~p", [N]);
@@ -734,6 +759,7 @@ attributes(I) ->
     Pure   = fun(W, R) -> Attr(W, R, true) end,
     Impure = fun(W, R) -> Attr(W, R, false) end,
     case I of
+        loop                                  -> Impure(pc, []);
         'RETURN'                              -> Impure(pc, []);
         {'RETURNR', A}                        -> Impure(pc, A);
         {'CALL', _}                           -> Impure(?a, []);
@@ -936,15 +962,29 @@ simpl_s({switch, Arg, Type, Alts, Def}, Options) ->
     {switch, Arg, Type, [simplify(A, Options) || A <- Alts], simplify(Def, Options)};
 simpl_s(I, _) -> I.
 
-simpl_top(I, Code, Options) ->
+%% Safe-guard against loops in the rewriting. Shouldn't happen so throw an
-    apply_rules(rules(), I, Code, Options).
+%% error if we run out.
+-define(SIMPL_FUEL, 5000).
 
-apply_rules(Rules, I, Code, Options) ->
+simpl_top(I, Code, Options) ->
-    Cons = fun(X, Xs) -> simpl_top(X, Xs, Options) end,
+    simpl_top(?SIMPL_FUEL, I, Code, Options).
+
+simpl_top(0, I, Code, _Options) ->
+    error({out_of_fuel, I, Code});
+simpl_top(Fuel, I, Code, Options) ->
+    apply_rules(Fuel, rules(), I, Code, Options).
+
+apply_rules(Fuel, Rules, I, Code, Options) ->
+    Cons = fun(X, Xs) -> simpl_top(Fuel - 1, X, Xs, Options) end,
     case apply_rules_once(Rules, I, Code) of
         false -> [I | Code];
         {RName, New, Rest} ->
-            debug(opt_rules, Options, "  Applied ~p:\n~s  ==>\n~s\n", [RName, pp_ann("    ", [I | Code]), pp_ann("    ", New ++ Rest)]),
+            case is_debug(opt_rules, Options) of
+                true ->
+                    {OldCode, NewCode} = drop_common_suffix([I | Code], New ++ Rest),
+                    debug(opt_rules, Options, "  Applied ~p:\n~s  ==>\n~s\n", [RName, pp_ann("    ", OldCode), pp_ann("    ", NewCode)]);
+                false -> ok
+            end,
             lists:foldr(Cons, Rest, New)
     end.
 
@@ -968,6 +1008,7 @@ merge_rules() ->
 rules() ->
     merge_rules() ++
     [?RULE(r_swap_push),
+     ?RULE(r_swap_pop),
      ?RULE(r_swap_write),
      ?RULE(r_constant_propagation),
      ?RULE(r_prune_impossible_branches),
@@ -1005,12 +1046,13 @@ inline_push(Ann1, Arg, Stack, [{i, Ann2, I} = AI | Code], Acc) ->
                     {As0, As1} = split_stack_arg(Stack, As),
                     Acc1 = [{i, merge_ann(Ann1, Ann2), from_op_view(Op, R, As0 ++ [Arg] ++ As1)} | Acc],
                     {lists:reverse(Acc1), Code};
-                false ->
+                false when Arg /= R ->
                     {AI1, {i, Ann1b, _}} = swap_instrs({i, Ann1, {'STORE', ?a, Arg}}, AI),
-                    inline_push(Ann1b, Arg, Stack + Produces - Consumes, Code, [AI1 | Acc])
+                    inline_push(Ann1b, Arg, Stack + Produces - Consumes, Code, [AI1 | Acc]);
-            end;
                 false -> false
             end;
+        _ -> false
+    end;
 inline_push(_, _, _, _, _) -> false.
 
 split_stack_arg(N, As) -> split_stack_arg(N, As, []).
@@ -1021,16 +1063,42 @@ split_stack_arg(N, [A | As], Acc) ->
             true    -> N end,
     split_stack_arg(N1, As, [A | Acc]).
 
-%% Move PUSH A past non-stack instructions.
+%% Move PUSHes past non-stack instructions.
-r_swap_push(Push = {i, _, {'STORE', ?a, _}}, [I | Code]) ->
+r_swap_push(Push = {i, _, PushI}, [I | Code]) ->
+    case op_view(PushI) of
+        {_, ?a, _} ->
             case independent(Push, I) of
                 true ->
                     {I1, Push1} = swap_instrs(Push, I),
                     {[I1, Push1], Code};
                 false -> false
             end;
+        _ -> false
+    end;
 r_swap_push(_, _) -> false.
 
+%% Move non-stack instruction past POPs.
+r_swap_pop(IA = {i, _, I}, [JA = {i, _, J} | Code]) ->
+    case independent(IA, JA) of
+        true ->
+            case {op_view(I), op_view(J)} of
+                {false, _} -> false;
+                {_, false} -> false;
+                {{_, IR, IAs}, {_, RJ, JAs}} ->
+                    NonStackI = not lists:member(?a, [IR | IAs]),
+                    %% RJ /= ?a to not conflict with r_swap_push
+                    PopJ      = RJ /= ?a andalso lists:member(?a, JAs),
+                    case NonStackI andalso PopJ of
+                        false -> false;
+                        true  ->
+                            {JA1, IA1} = swap_instrs(IA, JA),
+                            {[JA1, IA1], Code}
+                    end
+            end;
+        false -> false
+    end;
+r_swap_pop(_, _) -> false.
+
 %% Match up writes to variables with instructions further down.
 r_swap_write(I = {i, _, _}, [J | Code]) ->
     case {var_writes(I), independent(I, J)} of
@@ -1166,6 +1234,8 @@ r_float_switch_body(I = {i, _, _}, [switch_body | Code]) ->
 r_float_switch_body(_, _) -> false.
 
 %% Inline stores
+r_inline_store({i, _, {'STORE', R, R}}, Code) ->
+    {[], Code};
 r_inline_store(I = {i, _, {'STORE', R = {var, _}, A}}, Code) ->
     %% Not when A is var unless updating the annotations properly.
     Inline = case A of
@@ -1259,7 +1329,11 @@ unannotate({i, _Ann, I}) -> [I].
 
 %% Desugar and specialize
 desugar({'ADD', ?a, ?i(1), ?a}) -> [aeb_fate_ops:inc()];
+desugar({'ADD', A,  ?i(1), A})  -> [aeb_fate_ops:inc(A)];
+desugar({'ADD', ?a, ?a, ?i(1)}) -> [aeb_fate_ops:inc()];
+desugar({'ADD', A,  A,  ?i(1)}) -> [aeb_fate_ops:inc(A)];
 desugar({'SUB', ?a, ?a, ?i(1)}) -> [aeb_fate_ops:dec()];
+desugar({'SUB', A, A, ?i(1)})   -> [aeb_fate_ops:dec(A)];
 desugar({'STORE', ?a, A})       -> [aeb_fate_ops:push(A)];
 desugar({switch, Arg, Type, Alts, Def}) ->
     [{switch, Arg, Type, [desugar(A) || A <- Alts], desugar(Def)}];
@@ -1460,7 +1534,8 @@ split_calls(Ref, [], Acc, Blocks) ->
 split_calls(Ref, [I | Code], Acc, Blocks) when element(1, I) == 'CALL';
                                                element(1, I) == 'CALL_R';
                                                element(1, I) == 'CALL_GR';
-                                               element(1, I) == 'jumpif' ->
+                                               element(1, I) == 'jumpif';
+                                               I == loop ->
     split_calls(make_ref(), Code, [], [{Ref, lists:reverse([I | Acc])} | Blocks]);
 split_calls(Ref, [{'ABORT', _} = I | _Code], Acc, Blocks) ->
     lists:reverse([{Ref, lists:reverse([I | Acc])} | Blocks]);
@@ -1473,6 +1548,7 @@ split_calls(Ref, [I | Code], Acc, Blocks) ->
 
 set_labels(Labels, {Ref, Code}) when is_reference(Ref) ->
     {maps:get(Ref, Labels), [ set_labels(Labels, I) || I <- Code ]};
+set_labels(_Labels, loop)              -> aeb_fate_ops:jump(0);
 set_labels(Labels, {jump, Ref})        -> aeb_fate_ops:jump(maps:get(Ref, Labels));
 set_labels(Labels, {jumpif, Arg, Ref}) -> aeb_fate_ops:jumpif(Arg, maps:get(Ref, Labels));
 set_labels(Labels, {switch, Arg, Refs}) ->
@@ -1488,3 +1564,11 @@ set_labels(_, I) -> I.
 with_ixs(Xs) ->
     lists:zip(lists:seq(0, length(Xs) - 1), Xs).
 
+drop_common_suffix(Xs, Ys) ->
+    drop_common_suffix_r(lists:reverse(Xs), lists:reverse(Ys)).
+
+drop_common_suffix_r([X | Xs], [X | Ys]) ->
+    drop_common_suffix_r(Xs, Ys);
+drop_common_suffix_r(Xs, Ys) ->
+    {lists:reverse(Xs), lists:reverse(Ys)}.
+