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-rw-r--r--lib/compiler/src/beam_trim.erl326
1 files changed, 247 insertions, 79 deletions
diff --git a/lib/compiler/src/beam_trim.erl b/lib/compiler/src/beam_trim.erl
index 4da0985085..acf3838da4 100644
--- a/lib/compiler/src/beam_trim.erl
+++ b/lib/compiler/src/beam_trim.erl
@@ -21,12 +21,11 @@
-module(beam_trim).
-export([module/2]).
--import(lists, [reverse/1,reverse/2,splitwith/2,sort/1]).
+-import(lists, [any/2,member/2,reverse/1,reverse/2,splitwith/2,sort/1]).
-record(st,
- {safe :: gb_sets:set(beam_asm:label()), %Safe labels.
- lbl :: beam_utils:code_index() %Code at each label.
- }).
+ {safe :: cerl_sets:set(beam_asm:label()) %Safe labels.
+ }).
-spec module(beam_utils:module_code(), [compile:option()]) ->
{'ok',beam_utils:module_code()}.
@@ -36,10 +35,15 @@ module({Mod,Exp,Attr,Fs0,Lc}, _Opts) ->
{ok,{Mod,Exp,Attr,Fs,Lc}}.
function({function,Name,Arity,CLabel,Is0}) ->
- %%ok = io:fwrite("~w: ~p\n", [?LINE,{Name,Arity}]),
- St = #st{safe=safe_labels(Is0, []),lbl=beam_utils:index_labels(Is0)},
- Is = trim(Is0, St, []),
- {function,Name,Arity,CLabel,Is}.
+ try
+ St = #st{safe=safe_labels(Is0, [])},
+ Is = trim(Is0, St, []),
+ {function,Name,Arity,CLabel,Is}
+ catch
+ Class:Error:Stack ->
+ io:fwrite("Function: ~w/~w\n", [Name,Arity]),
+ erlang:raise(Class, Error, Stack)
+ end.
trim([{kill,_}|_]=Is0, St, Acc) ->
{Kills0,Is1} = splitwith(fun({kill,_}) -> true;
@@ -47,14 +51,33 @@ trim([{kill,_}|_]=Is0, St, Acc) ->
end, Is0),
Kills = sort(Kills0),
try
- {FrameSize,Layout} = frame_layout(Is1, Kills, St),
- Configs = trim_instructions(Layout),
- try_remap(Configs, Is1, FrameSize)
- of
+ %% Find out the size and layout of the stack frame.
+ %% Example of a layout:
+ %%
+ %% [{kill,{y,0}},{dead,{y,1},{live,{y,2}},{kill,{y,3}}]
+ %%
+ %% That means that y0 and y3 are to be killed, that y1
+ %% has been killed previously, and that y2 is live.
+ {FrameSize,Layout} = frame_layout(Is1, Kills, St),
+
+ %% Calculate all recipes that are not worse in terms
+ %% of estimated execution time. The recipes are ordered
+ %% in descending order from how much they trim.
+ Recipes = trim_recipes(Layout),
+
+ %% Try the recipes in order. A recipe may not work out because
+ %% a register that was previously killed may be
+ %% resurrected. If that happens, the next recipe, which trims
+ %% less, will be tried.
+ try_remap(Recipes, Is1, FrameSize)
+ of
{Is,TrimInstr} ->
+ %% One of the recipes was applied.
trim(Is, St, reverse(TrimInstr)++Acc)
catch
not_possible ->
+ %% No recipe worked out. Use the original kill
+ %% instructions.
trim(Is1, St, reverse(Kills, Acc))
end;
trim([I|Is], St, Acc) ->
@@ -62,34 +85,42 @@ trim([I|Is], St, Acc) ->
trim([], _, Acc) ->
reverse(Acc).
-%% trim_instructions([{kill,R}|{live,R}|{dead,R}]) -> {[Instruction],MapFun}
-%% Figure out the sequence of moves and trim to use.
+%% trim_recipes([{kill,R}|{live,R}|{dead,R}]) -> [Recipe].
+%% Recipe = {Kills,NumberToTrim,Moves}
+%% Kills = [{kill,Y}]
+%% Moves = [{move,SrcY,DstY}]
+%%
+%% Calculate how to best trim the stack and kill the correct
+%% Y registers. Return a list of possible recipes. The best
+%% recipe (the one that trims the most) is first in the list.
+%% All of the recipes are no worse in estimated execution time
+%% than the original sequences of kill instructions.
-trim_instructions(Layout) ->
+trim_recipes(Layout) ->
Cost = length([I || {kill,_}=I <- Layout]),
- trim_instructions_1(Layout, 0, [], {Cost,[]}).
+ trim_recipes_1(Layout, 0, [], {Cost,[]}).
-trim_instructions_1([{kill,{y,Trim0}}|Ks], Trim0, Moves, Config0) ->
+trim_recipes_1([{kill,{y,Trim0}}|Ks], Trim0, Moves, Recipes0) ->
Trim = Trim0 + 1,
- Config = save_config(Ks, Trim, Moves, Config0),
- trim_instructions_1(Ks, Trim, Moves, Config);
-trim_instructions_1([{dead,{y,Trim0}}|Ks], Trim0, Moves, Config0) ->
+ Recipes = save_recipe(Ks, Trim, Moves, Recipes0),
+ trim_recipes_1(Ks, Trim, Moves, Recipes);
+trim_recipes_1([{dead,{y,Trim0}}|Ks], Trim0, Moves, Recipes0) ->
Trim = Trim0 + 1,
- Config = save_config(Ks, Trim, Moves, Config0),
- trim_instructions_1(Ks, Trim, Moves, Config);
-trim_instructions_1([{live,{y,Trim0}=Src}|Ks0], Trim0, Moves0, Config0) ->
+ Recipes = save_recipe(Ks, Trim, Moves, Recipes0),
+ trim_recipes_1(Ks, Trim, Moves, Recipes);
+trim_recipes_1([{live,{y,Trim0}=Src}|Ks0], Trim0, Moves0, Recipes0) ->
case take_last_dead(Ks0) of
none ->
- {_,ConfigList} = Config0,
- ConfigList;
+ {_,RecipesList} = Recipes0,
+ RecipesList;
{Dst,Ks} ->
Trim = Trim0 + 1,
Moves = [{move,Src,Dst}|Moves0],
- Config = save_config(Ks, Trim, Moves, Config0),
- trim_instructions_1(Ks, Trim, Moves, Config)
+ Recipes = save_recipe(Ks, Trim, Moves, Recipes0),
+ trim_recipes_1(Ks, Trim, Moves, Recipes)
end;
-trim_instructions_1([], _, _, {_,ConfigList}) ->
- ConfigList.
+trim_recipes_1([], _, _, {_,RecipesList}) ->
+ RecipesList.
take_last_dead(L) ->
take_last_dead_1(reverse(L)).
@@ -100,28 +131,48 @@ take_last_dead_1([{dead,Reg}|Is]) ->
{Reg,reverse(Is)};
take_last_dead_1(_) -> none.
-save_config(Ks, Trim, Moves, {MaxCost,Acc}=Config) ->
- case config_cost(Ks, Moves) of
- Cost when Cost =< MaxCost ->
- {MaxCost,[{Ks,Trim,Moves}|Acc]};
+save_recipe(Ks, Trim, Moves, {MaxCost,Acc}=Recipes) ->
+ case recipe_cost(Ks, Moves) of
+ Cost when Cost =< MaxCost ->
+ %% The price is right.
+ {MaxCost,[{Ks,Trim,Moves}|Acc]};
_Cost ->
- Config
+ %% Too expensive.
+ Recipes
end.
-config_cost(Ks, Moves) ->
+recipe_cost(Ks, Moves) ->
%% We estimate that a {move,{y,_},{y,_}} instruction is roughly twice as
%% expensive as a {kill,{y,_}} instruction. A {trim,_} instruction is
%% roughly as expensive as a {kill,{y,_}} instruction.
- config_cost_1(Ks, 1+2*length(Moves)).
+ recipe_cost_1(Ks, 1+2*length(Moves)).
-config_cost_1([{kill,_}|Ks], Cost) ->
- config_cost_1(Ks, Cost+1);
-config_cost_1([_|Ks], Cost) ->
- config_cost_1(Ks, Cost);
-config_cost_1([], Cost) -> Cost.
+recipe_cost_1([{kill,_}|Ks], Cost) ->
+ recipe_cost_1(Ks, Cost+1);
+recipe_cost_1([_|Ks], Cost) ->
+ recipe_cost_1(Ks, Cost);
+recipe_cost_1([], Cost) -> Cost.
-expand_config({Layout,Trim,Moves}, FrameSize) ->
+%% try_remap([Recipe], [Instruction], FrameSize) ->
+%% {[Instruction],[TrimInstruction]}.
+%% Try to renumber Y registers in the instruction stream. The
+%% first rececipe that works will be used.
+%%
+%% This function will issue a `not_possible` exception if none
+%% of the recipes were possible to apply.
+
+try_remap([R|Rs], Is, FrameSize) ->
+ {TrimInstr,Map} = expand_recipe(R, FrameSize),
+ try
+ {remap(Is, Map, []),TrimInstr}
+ catch
+ throw:not_possible ->
+ try_remap(Rs, Is, FrameSize)
+ end;
+try_remap([], _, _) -> throw(not_possible).
+
+expand_recipe({Layout,Trim,Moves}, FrameSize) ->
Kills = [Kill || {kill,_}=Kill <- Layout],
{Kills++reverse(Moves, [{trim,Trim,FrameSize-Trim}]),create_map(Trim, Moves)}.
@@ -132,16 +183,16 @@ create_map(Trim, []) ->
(Any) -> Any
end;
create_map(Trim, Moves) ->
- GbTree0 = [{Src,Dst-Trim} || {move,{y,Src},{y,Dst}} <- Moves],
- GbTree = gb_trees:from_orddict(sort(GbTree0)),
- IllegalTargets = gb_sets:from_list([Dst || {move,_,{y,Dst}} <- Moves]),
+ Map0 = [{Src,Dst-Trim} || {move,{y,Src},{y,Dst}} <- Moves],
+ Map = maps:from_list(Map0),
+ IllegalTargets = cerl_sets:from_list([Dst || {move,_,{y,Dst}} <- Moves]),
fun({y,Y0}) when Y0 < Trim ->
- case gb_trees:lookup(Y0, GbTree) of
- {value,Y} -> {y,Y};
- none -> throw(not_possible)
- end;
+ case Map of
+ #{Y0:=Y} -> {y,Y};
+ #{} -> throw(not_possible)
+ end;
({y,Y}) ->
- case gb_sets:is_element(Y, IllegalTargets) of
+ case cerl_sets:is_element(Y, IllegalTargets) of
true -> throw(not_possible);
false -> {y,Y-Trim}
end;
@@ -149,19 +200,17 @@ create_map(Trim, Moves) ->
(Any) -> Any
end.
-try_remap([C|Cs], Is, FrameSize) ->
- {TrimInstr,Map} = expand_config(C, FrameSize),
- try
- {remap(Is, Map, []),TrimInstr}
- catch
- throw:not_possible ->
- try_remap(Cs, Is, FrameSize)
- end;
-try_remap([], _, _) -> throw(not_possible).
-
+remap([{'%',_}=I|Is], Map, Acc) ->
+ remap(Is, Map, [I|Acc]);
remap([{block,Bl0}|Is], Map, Acc) ->
Bl = remap_block(Bl0, Map, []),
remap(Is, Map, [{block,Bl}|Acc]);
+remap([{bs_get_tail,Src,Dst,Live}|Is], Map, Acc) ->
+ I = {bs_get_tail,Map(Src),Map(Dst),Live},
+ remap(Is, Map, [I|Acc]);
+remap([{bs_set_position,Src1,Src2}|Is], Map, Acc) ->
+ I = {bs_set_position,Map(Src1),Map(Src2)},
+ remap(Is, Map, [I|Acc]);
remap([{call_fun,_}=I|Is], Map, Acc) ->
remap(Is, Map, [I|Acc]);
remap([{call,_,_}=I|Is], Map, Acc) ->
@@ -205,35 +254,68 @@ remap([return|_]=Is, _, Acc) ->
reverse(Acc, Is);
remap([{line,_}=I|Is], Map, Acc) ->
remap(Is, Map, [I|Acc]).
-
+
remap_block([{set,Ds0,Ss0,Info}|Is], Map, Acc) ->
Ds = [Map(D) || D <- Ds0],
Ss = [Map(S) || S <- Ss0],
remap_block(Is, Map, [{set,Ds,Ss,Info}|Acc]);
remap_block([], _, Acc) -> reverse(Acc).
-
-safe_labels([{label,L},{line,_},{badmatch,{Tag,_}}|Is], Acc) when Tag =/= y ->
- safe_labels(Is, [L|Acc]);
-safe_labels([{label,L},{line,_},{case_end,{Tag,_}}|Is], Acc) when Tag =/= y ->
- safe_labels(Is, [L|Acc]);
-safe_labels([{label,L},{line,_},if_end|Is], Acc) ->
- safe_labels(Is, [L|Acc]);
-safe_labels([{label,L},
- {block,[{set,[{x,0}],[{Tag,_}],move}]},
- {line,_},
- {call_ext,1,{extfunc,erlang,error,1}}|Is], Acc) when Tag =/= y ->
- safe_labels(Is, [L|Acc]);
+
+%% safe_labels([Instruction], Accumulator) -> gb_set()
+%% Build a gb_set of safe labels. The code at a safe
+%% label does not depend on the values in a specific
+%% Y register, only that all Y registers are initialized
+%% so that it safe to scan the stack when an exception
+%% is generated.
+%%
+%% In other words, code at a safe label will continue
+%% to work if Y registers have been renumbered and
+%% the size of the stack frame has changed.
+
+safe_labels([{label,L}|Is], Acc) ->
+ case is_safe_label(Is) of
+ true -> safe_labels(Is, [L|Acc]);
+ false -> safe_labels(Is, Acc)
+ end;
safe_labels([_|Is], Acc) ->
safe_labels(Is, Acc);
-safe_labels([], Acc) -> gb_sets:from_list(Acc).
+safe_labels([], Acc) -> cerl_sets:from_list(Acc).
+
+is_safe_label([{'%',_}|Is]) ->
+ is_safe_label(Is);
+is_safe_label([{line,_}|Is]) ->
+ is_safe_label(Is);
+is_safe_label([{badmatch,{Tag,_}}|_]) ->
+ Tag =/= y;
+is_safe_label([{case_end,{Tag,_}}|_]) ->
+ Tag =/= y;
+is_safe_label([{try_case_end,{Tag,_}}|_]) ->
+ Tag =/= y;
+is_safe_label([if_end|_]) ->
+ true;
+is_safe_label([{block,Bl}|Is]) ->
+ is_safe_label_block(Bl) andalso is_safe_label(Is);
+is_safe_label([{call_ext,_,{extfunc,M,F,A}}|_]) ->
+ erl_bifs:is_exit_bif(M, F, A);
+is_safe_label(_) -> false.
+
+is_safe_label_block([{set,Ds,Ss,_}|Is]) ->
+ IsYreg = fun({y,_}) -> true;
+ (_) -> false
+ end,
+ %% This instruction is safe if the instruction
+ %% neither reads or writes Y registers.
+ not (any(IsYreg, Ss) orelse any(IsYreg, Ds)) andalso
+ is_safe_label_block(Is);
+is_safe_label_block([]) -> true.
%% frame_layout([Instruction], [{kill,_}], St) ->
%% [{kill,Reg} | {live,Reg} | {dead,Reg}]
%% Figure out the layout of the stack frame.
-frame_layout(Is, Kills, #st{safe=Safe,lbl=D}) ->
+frame_layout(Is, Kills, #st{safe=Safe}) ->
N = frame_size(Is, Safe),
- IsKilled = fun(R) -> beam_utils:is_not_used(R, Is, D) end,
+ IsKilled = fun(R) -> is_not_used(R, Is) end,
{N,frame_layout_1(Kills, 0, N, IsKilled, [])}.
frame_layout_1([{kill,{y,Y}}=I|Ks], Y, N, IsKilled, Acc) ->
@@ -253,7 +335,14 @@ frame_layout_2(Is) -> reverse(Is).
%% frame_size([Instruction], SafeLabels) -> FrameSize
%% Find out the frame size by looking at the code that follows.
+%%
+%% Implicitly, also check that the instructions are a straight
+%% sequence of code that ends in a return. Any branches are
+%% to safe labels (i.e., the code at those labels don't depend
+%% on the contents of any Y register).
+frame_size([{'%',_}|Is], Safe) ->
+ frame_size(Is, Safe);
frame_size([{block,_}|Is], Safe) ->
frame_size(Is, Safe);
frame_size([{call_fun,_}|Is], Safe) ->
@@ -285,15 +374,94 @@ frame_size([{make_fun2,_,_,_,_}|Is], Safe) ->
frame_size(Is, Safe);
frame_size([{get_map_elements,{f,L},_,_}|Is], Safe) ->
frame_size_branch(L, Is, Safe);
-frame_size([{deallocate,N}|_], _) -> N;
+frame_size([{deallocate,N}|_], _) ->
+ N;
frame_size([{line,_}|Is], Safe) ->
frame_size(Is, Safe);
-frame_size([_|_], _) -> throw(not_possible).
+frame_size([{bs_set_position,_,_}|Is], Safe) ->
+ frame_size(Is, Safe);
+frame_size([{bs_get_tail,_,_,_}|Is], Safe) ->
+ frame_size(Is, Safe);
+frame_size(_, _) -> throw(not_possible).
frame_size_branch(0, Is, Safe) ->
frame_size(Is, Safe);
frame_size_branch(L, Is, Safe) ->
- case gb_sets:is_member(L, Safe) of
+ case cerl_sets:is_element(L, Safe) of
false -> throw(not_possible);
true -> frame_size(Is, Safe)
end.
+
+%% is_not_used(Y, [Instruction]) -> true|false.
+%% Test whether the value of Y is unused in the instruction sequence.
+%% Return true if the value of Y is not used, and false if it is used.
+%%
+%% This function handles the same instructions as frame_size/2. It
+%% assumes that any labels in the instructions are safe labels.
+
+is_not_used(Y, [{'%',_}|Is]) ->
+ is_not_used(Y, Is);
+is_not_used(Y, [{apply,_}|Is]) ->
+ is_not_used(Y, Is);
+is_not_used(Y, [{bif,_,{f,_},Ss,Dst}|Is]) ->
+ is_not_used_ss_dst(Y, Ss, Dst, Is);
+is_not_used(Y, [{block,Bl}|Is]) ->
+ case is_not_used_block(Y, Bl) of
+ used -> false;
+ killed -> true;
+ transparent -> is_not_used(Y, Is)
+ end;
+is_not_used(Y, [{bs_get_tail,Src,Dst,_}|Is]) ->
+ is_not_used_ss_dst(Y, [Src], Dst, Is);
+is_not_used(Y, [{bs_init,_,_,_,Ss,Dst}|Is]) ->
+ is_not_used_ss_dst(Y, Ss, Dst, Is);
+is_not_used(Y, [{bs_put,{f,_},_,Ss}|Is]) ->
+ not member(Y, Ss) andalso is_not_used(Y, Is);
+is_not_used(Y, [{bs_set_position,Src1,Src2}|Is]) ->
+ Y =/= Src1 andalso Y =/= Src2 andalso
+ is_not_used(Y, Is);
+is_not_used(Y, [{call,_,_}|Is]) ->
+ is_not_used(Y, Is);
+is_not_used(Y, [{call_ext,_,_}=I|Is]) ->
+ beam_jump:is_exit_instruction(I) orelse is_not_used(Y, Is);
+is_not_used(Y, [{call_fun,_}|Is]) ->
+ is_not_used(Y, Is);
+is_not_used(_Y, [{deallocate,_}|_]) ->
+ true;
+is_not_used(Y, [{gc_bif,_,{f,_},_Live,Ss,Dst}|Is]) ->
+ is_not_used_ss_dst(Y, Ss, Dst, Is);
+is_not_used(Y, [{get_map_elements,{f,_},S,{list,List}}|Is]) ->
+ {Ss,Ds} = beam_utils:split_even(List),
+ case member(Y, [S|Ss]) of
+ true ->
+ false;
+ false ->
+ member(Y, Ds) orelse is_not_used(Y, Is)
+ end;
+is_not_used(Y, [{kill,Yreg}|Is]) ->
+ Y =:= Yreg orelse is_not_used(Y, Is);
+is_not_used(Y, [{line,_}|Is]) ->
+ is_not_used(Y, Is);
+is_not_used(Y, [{make_fun2,_,_,_,_}|Is]) ->
+ is_not_used(Y, Is);
+is_not_used(Y, [{test,_,_,Ss}|Is]) ->
+ not member(Y, Ss) andalso is_not_used(Y, Is);
+is_not_used(Y, [{test,_Op,{f,_},_Live,Ss,Dst}|Is]) ->
+ is_not_used_ss_dst(Y, Ss, Dst, Is).
+
+is_not_used_block(Y, [{set,Ds,Ss,_}|Is]) ->
+ case member(Y, Ss) of
+ true ->
+ used;
+ false ->
+ case member(Y, Ds) of
+ true ->
+ killed;
+ false ->
+ is_not_used_block(Y, Is)
+ end
+ end;
+is_not_used_block(_Y, []) -> transparent.
+
+is_not_used_ss_dst(Y, Ss, Dst, Is) ->
+ not member(Y, Ss) andalso (Y =:= Dst orelse is_not_used(Y, Is)).
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-02 10:57:58 +0000