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optimize beam_trim #10272

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d03275e
optimize beam_trim
Schultzer Oct 9, 2025
dbbb219
revert unnecessary changes and leverage gb_sets
Schultzer Oct 10, 2025
e66847c
revert changes and leverage is_equal for assertion
Schultzer Oct 18, 2025
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113 changes: 58 additions & 55 deletions lib/compiler/src/beam_trim.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -24,12 +24,12 @@
-moduledoc false.
-export([module/2]).

-import(lists, [any/2,reverse/1,reverse/2,seq/2,sort/1]).
-import(lists, [any/2,merge/1,reverse/1,reverse/2,seq/2,sort/1]).

-include("beam_asm.hrl").

-record(st,
{safe :: sets:set(beam_asm:label()), %Safe labels.
{safe :: gb_sets:set(beam_asm:label()), %Safe labels.
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Changing from sets to gb_sets is unnecessary since the only operation performed on this set is checking for membership (in is_safe_branch/2). Generally, checking for membership is faster for sets than for gb_sets.

fsz :: non_neg_integer()
}).

Expand All @@ -48,8 +48,8 @@ function({function,Name,Arity,CLabel,Is0}) ->
{function,Name,Arity,CLabel,Is}
catch
Class:Error:Stack ->
io:fwrite("Function: ~w/~w\n", [Name,Arity]),
erlang:raise(Class, Error, Stack)
io:fwrite("Function: ~w/~w\n", [Name,Arity]),
erlang:raise(Class, Error, Stack)
end.

trim([{init_yregs,_}=I|Is], none, St0) ->
Expand Down Expand Up @@ -116,7 +116,7 @@ is_not_recursive(_) -> false.
%% Y registers. Return the recipe that trims the most.

trim_recipe(Layout, IsNotRecursive, {Us,Ns}) ->
UsedRegs = ordsets:union(Us, Ns),
UsedRegs = gb_sets:union(Us, Ns),
Recipes = construct_recipes(Layout, 0, [], []),
NumOrigKills = length([I || {kill,_}=I <- Layout]),
IsTooExpensive = is_too_expensive_fun(IsNotRecursive),
Expand Down Expand Up @@ -199,15 +199,14 @@ is_too_expensive_fun(false) ->
end.

is_recipe_viable({_,Trim,Moves}, UsedRegs) ->
Moved = ordsets:from_list([Src || {move,Src,_} <- Moves]),
Illegal = ordsets:from_list([Dst || {move,_,Dst} <- Moves]),
Moved = gb_sets:from_list([Src || {move,Src,_} <- Moves]),
Illegal = gb_sets:from_list([Dst || {move,_,Dst} <- Moves]),
Eliminated = [{y,N} || N <- seq(0, Trim - 1)],
%% All eliminated registers that are also in the used set must be moved.
UsedEliminated = ordsets:intersection(Eliminated, UsedRegs),
case ordsets:is_subset(UsedEliminated, Moved) andalso
ordsets:is_disjoint(Illegal, UsedRegs) of
UsedEliminated = gb_sets:intersection(gb_sets:from_list(Eliminated), UsedRegs),
case gb_sets:is_subset(UsedEliminated, Moved) andalso gb_sets:is_disjoint(Illegal, UsedRegs) of
true ->
UsedEliminated = Moved, %Assertion.
true = gb_sets:is_equal(UsedEliminated, Moved), %Assertion.
true;
_ ->
false
Expand Down Expand Up @@ -365,7 +364,7 @@ safe_labels([{label,L}|Is], Acc) ->
end;
safe_labels([_|Is], Acc) ->
safe_labels(Is, Acc);
safe_labels([], Acc) -> sets:from_list(Acc).
safe_labels([], Acc) -> gb_sets:from_list(Acc).

is_safe_label([{'%',_}|Is]) ->
is_safe_label(Is);
Expand Down Expand Up @@ -405,12 +404,15 @@ is_safe_label_block([]) -> true.
%% Figure out the layout of the stack frame.

frame_layout(N, Killed, {U,_}) ->
Dead0 = [{y,R} || R <- seq(0, N - 1)],
Dead = ordsets:subtract(Dead0, ordsets:union(U, Killed)),
Is = [[{R,{live,R}} || R <- U],
AllRegisters = [{y,R} || R <- seq(0, N - 1)],
LiveOrKilledSet = gb_sets:union(U, gb_sets:from_list(Killed)),
DeadSet = gb_sets:subtract(gb_sets:from_list(AllRegisters), LiveOrKilledSet),
UsedRegs = gb_sets:to_list(U),
Dead = gb_sets:to_list(DeadSet),
Is = [[{R,{live,R}} || R <- UsedRegs],
[{R,{dead,R}} || R <- Dead],
[{R,{kill,R}} || R <- Killed]],
[I || {_,I} <:- lists:merge(Is)].
[I || {_,I} <:- merge(Is)].

%% usage([Instruction], SafeLabels) -> {FrameSize,[UsedYRegs]}
%% Find out the frame size and usage information by looking at the
Expand All @@ -435,8 +437,9 @@ usage_1([], Acc) ->
do_usage(Is0, #st{safe=Safe}) ->
case Is0 of
[return,{deallocate,N}|Is] ->
Regs = [],
case do_usage(Is, Safe, Regs, [], []) of
Regs = gb_sets:new(),
Ns = gb_sets:new(),
case do_usage(Is, Safe, Regs, Ns, []) of
none ->
none;
Us ->
Expand All @@ -458,30 +461,30 @@ do_usage([{block,Blk}|Is], Safe, Regs0, Ns0, Acc) ->
do_usage([{bs_create_bin,Fail,_,_,_,Dst,{list,Args}}|Is], Safe, Regs0, Ns0, Acc) ->
case is_safe_branch(Fail, Safe) of
true ->
Regs1 = ordsets:del_element(Dst, Regs0),
Regs = ordsets:union(Regs1, yregs(Args)),
Ns = ordsets:union(yregs([Dst]), Ns0),
Regs1 = gb_sets:del_element(Dst, Regs0),
Regs = gb_sets:union(Regs1, yregs(Args)),
Ns = gb_sets:union(yregs([Dst]), Ns0),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
false ->
none
end;
do_usage([{bs_get_tail,Src,Dst,_}|Is], Safe, Regs0, Ns0, Acc) ->
Regs1 = ordsets:del_element(Dst, Regs0),
Regs = ordsets:union(Regs1, yregs([Src])),
Ns = ordsets:union(yregs([Dst]), Ns0),
Regs1 = gb_sets:del_element(Dst, Regs0),
Regs = gb_sets:union(Regs1, yregs([Src])),
Ns = gb_sets:union(yregs([Dst]), Ns0),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{bs_set_position,Src1,Src2}|Is], Safe, Regs0, Ns, Acc) ->
Regs = ordsets:union(Regs0, yregs([Src1,Src2])),
Regs = gb_sets:union(Regs0, yregs([Src1,Src2])),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{bs_start_match4,Fail,_Live,Src,Dst}|Is], Safe, Regs0, Ns, Acc) ->
case (Fail =:= {atom,no_fail} orelse
Fail =:= {atom,resume} orelse
is_safe_branch(Fail, Safe)) of
true ->
Regs = ordsets:union(Regs0, yregs([Src,Dst])),
Regs = gb_sets:union(Regs0, yregs([Src,Dst])),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
false ->
Expand All @@ -497,15 +500,15 @@ do_usage([{call_fun,_}|Is], Safe, Regs, Ns, Acc) ->
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{call_fun2,_,_,Ss}|Is], Safe, Regs0, Ns, Acc) ->
Regs = ordsets:union(Regs0, yregs([Ss])),
Regs = gb_sets:union(Regs0, yregs([Ss])),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{bif,_,Fail,Ss,Dst}|Is], Safe, Regs0, Ns0, Acc) ->
case is_safe_branch(Fail, Safe) of
true ->
Regs1 = ordsets:del_element(Dst, Regs0),
Regs = ordsets:union(Regs1, yregs(Ss)),
Ns = ordsets:union(yregs([Dst]), Ns0),
Regs1 = gb_sets:del_element(Dst, Regs0),
Regs = gb_sets:union(Regs1, yregs(Ss)),
Ns = gb_sets:union(yregs([Dst]), Ns0),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
false ->
Expand All @@ -514,9 +517,9 @@ do_usage([{bif,_,Fail,Ss,Dst}|Is], Safe, Regs0, Ns0, Acc) ->
do_usage([{gc_bif,_,Fail,_,Ss,Dst}|Is], Safe, Regs0, Ns0, Acc) ->
case is_safe_branch(Fail, Safe) of
true ->
Regs1 = ordsets:del_element(Dst, Regs0),
Regs = ordsets:union(Regs1, yregs(Ss)),
Ns = ordsets:union(yregs([Dst]), Ns0),
Regs1 = gb_sets:del_element(Dst, Regs0),
Regs = gb_sets:union(Regs1, yregs(Ss)),
Ns = gb_sets:union(yregs([Dst]), Ns0),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
false ->
Expand All @@ -527,46 +530,46 @@ do_usage([{get_map_elements,Fail,S,{list,List}}|Is], Safe, Regs0, Ns0, Acc) ->
true ->
{Ss,Ds1} = beam_utils:split_even(List),
Ds = yregs(Ds1),
Regs1 = ordsets:subtract(Regs0, Ds),
Regs = ordsets:union(Regs1, yregs([S|Ss])),
Ns = ordsets:union(Ns0, Ds),
Regs1 = gb_sets:subtract(Regs0, Ds),
Regs = gb_sets:union(Regs1, yregs([S|Ss])),
Ns = gb_sets:union(Ns0, Ds),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
false ->
none
end;
do_usage([{init_yregs,{list,Ds}}|Is], Safe, Regs0, Ns0, Acc) ->
Regs = ordsets:subtract(Regs0, Ds),
Ns = ordsets:union(Ns0, Ds),
Regs = gb_sets:subtract(Regs0, yregs(Ds)),
Ns = gb_sets:union(Ns0, gb_sets:from_list(Ds)),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{make_fun3,_,_,_,Dst,{list,Ss}}|Is], Safe, Regs0, Ns0, Acc) ->
Regs1 = ordsets:del_element(Dst, Regs0),
Regs = ordsets:union(Regs1, yregs(Ss)),
Ns = ordsets:union(yregs([Dst]), Ns0),
Regs1 = gb_sets:del_element(Dst, Regs0),
Regs = gb_sets:union(Regs1, yregs(Ss)),
Ns = gb_sets:union(yregs([Dst]), Ns0),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{update_record,_,_,Src,Dst,{list,Ss}}|Is], Safe, Regs0, Ns0, Acc) ->
Regs1 = ordsets:del_element(Dst, Regs0),
Regs = ordsets:union(Regs1, yregs([Src|Ss])),
Ns = ordsets:union(yregs([Dst]), Ns0),
Regs1 = gb_sets:del_element(Dst, Regs0),
Regs = gb_sets:union(Regs1, yregs([Src|Ss])),
Ns = gb_sets:union(yregs([Dst]), Ns0),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{line,_}|Is], Safe, Regs, Ns, Acc) ->
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{recv_marker_clear,Src}|Is], Safe, Regs0, Ns, Acc) ->
Regs = ordsets:union(Regs0, yregs([Src])),
Regs = gb_sets:union(Regs0, yregs([Src])),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{recv_marker_reserve,Src}|Is], Safe, Regs0, Ns, Acc) ->
Regs = ordsets:union(Regs0, yregs([Src])),
Regs = gb_sets:union(Regs0, yregs([Src])),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
do_usage([{test,_,Fail,Ss}|Is], Safe, Regs0, Ns, Acc) ->
case is_safe_branch(Fail, Safe) of
true ->
Regs = ordsets:union(Regs0, yregs(Ss)),
Regs = gb_sets:union(Regs0, yregs(Ss)),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
false ->
Expand All @@ -575,9 +578,9 @@ do_usage([{test,_,Fail,Ss}|Is], Safe, Regs0, Ns, Acc) ->
do_usage([{test,_,Fail,_,Ss,Dst}|Is], Safe, Regs0, Ns0, Acc) ->
case is_safe_branch(Fail, Safe) of
true ->
Regs1 = ordsets:del_element(Dst, Regs0),
Regs = ordsets:union(Regs1, yregs(Ss)),
Ns = ordsets:union(yregs([Dst]), Ns0),
Regs1 = gb_sets:del_element(Dst, Regs0),
Regs = gb_sets:union(Regs1, yregs(Ss)),
Ns = gb_sets:union(yregs([Dst]), Ns0),
U = {Regs,Ns},
do_usage(Is, Safe, Regs, Ns, [U|Acc]);
false ->
Expand All @@ -590,19 +593,19 @@ do_usage([], _Safe, _Regs, _Ns, Acc) -> Acc.
do_usage_blk([{set,Ds0,Ss,_}|Is], Regs0, Ns0) ->
Ds = yregs(Ds0),
{Regs1,Ns1} = do_usage_blk(Is, Regs0, Ns0),
Regs2 = ordsets:subtract(Regs1, Ds),
Regs = ordsets:union(Regs2, yregs(Ss)),
Ns = ordsets:union(Ns1, Ds),
Regs2 = gb_sets:subtract(Regs1, Ds),
Regs = gb_sets:union(Regs2, yregs(Ss)),
Ns = gb_sets:union(Ns1, Ds),
{Regs,Ns};
do_usage_blk([], Regs, Ns) -> {Regs,Ns}.

is_safe_branch({f,0}, _Safe) ->
true;
is_safe_branch({f,L}, Safe) ->
sets:is_element(L, Safe).
gb_sets:is_element(L, Safe).

yregs(Rs) ->
ordsets:from_list(yregs_1(Rs)).
gb_sets:from_list(yregs_1(Rs)).

yregs_1([{y,_}=Y|Rs]) ->
[Y|yregs_1(Rs)];
Expand Down