aboutsummaryrefslogtreecommitdiffstats
path: root/lib/compiler/src/beam_jump.erl
diff options
context:
space:
mode:
Diffstat (limited to 'lib/compiler/src/beam_jump.erl')
-rw-r--r--lib/compiler/src/beam_jump.erl306
1 files changed, 222 insertions, 84 deletions
diff --git a/lib/compiler/src/beam_jump.erl b/lib/compiler/src/beam_jump.erl
index 9eee56d604..fbff4cfd79 100644
--- a/lib/compiler/src/beam_jump.erl
+++ b/lib/compiler/src/beam_jump.erl
@@ -22,7 +22,7 @@
-module(beam_jump).
-export([module/2,
- is_unreachable_after/1,is_exit_instruction/1,
+ is_exit_instruction/1,
remove_unused_labels/1]).
%%% The following optimisations are done:
@@ -128,27 +128,123 @@
%%% on the program state.
%%%
--import(lists, [reverse/1,reverse/2,foldl/3]).
+-import(lists, [foldl/3,mapfoldl/3,reverse/1,reverse/2]).
-type instruction() :: beam_utils:instruction().
-spec module(beam_utils:module_code(), [compile:option()]) ->
{'ok',beam_utils:module_code()}.
-module({Mod,Exp,Attr,Fs0,Lc}, _Opt) ->
- Fs = [function(F) || F <- Fs0],
+module({Mod,Exp,Attr,Fs0,Lc0}, _Opt) ->
+ {Fs,Lc} = mapfoldl(fun function/2, Lc0, Fs0),
{ok,{Mod,Exp,Attr,Fs,Lc}}.
%% function(Function) -> Function'
%% Optimize jumps and branches.
%%
%% NOTE: This function assumes that there are no labels inside blocks.
-function({function,Name,Arity,CLabel,Asm0}) ->
- Asm1 = share(Asm0),
- Asm2 = move(Asm1),
- Asm3 = opt(Asm2, CLabel),
- Asm = remove_unused_labels(Asm3),
- {function,Name,Arity,CLabel,Asm}.
+function({function,Name,Arity,CLabel,Asm0}, Lc0) ->
+ Asm1 = eliminate_moves(Asm0),
+ {Asm2,Lc} = insert_labels(Asm1, Lc0, []),
+ Asm3 = share(Asm2),
+ Asm4 = move(Asm3),
+ Asm5 = opt(Asm4, CLabel),
+ Asm = remove_unused_labels(Asm5),
+ {{function,Name,Arity,CLabel,Asm},Lc}.
+
+%%%
+%%% Scan instructions in execution order and remove redundant 'move'
+%%% instructions. 'move' instructions are redundant if we know that
+%%% the register already contains the value being assigned, as in the
+%%% following code:
+%%%
+%%% select_val Register FailLabel [... Literal => L1...]
+%%% .
+%%% .
+%%% .
+%%% L1: move Literal Register
+%%%
+
+eliminate_moves(Is) ->
+ eliminate_moves(Is, #{}, []).
+
+eliminate_moves([{select,select_val,Reg,_,List}=I|Is], D0, Acc) ->
+ D = update_value_dict(List, Reg, D0),
+ eliminate_moves(Is, D, [I|Acc]);
+eliminate_moves([{label,Lbl},{block,[{set,[Dst],[Lit],move}|BlkIs]}=Blk0|Is],
+ D, Acc0) ->
+ Acc = [{label,Lbl}|Acc0],
+ case already_has_value(Lit, Lbl, Dst, D) andalso
+ no_fallthrough(Acc0) of
+ true ->
+ %% Remove redundant 'move' instruction.
+ Blk = {block,BlkIs},
+ eliminate_moves([Blk|Is], D, Acc);
+ false ->
+ %% Keep 'move' instruction.
+ eliminate_moves([Blk0|Is], D, Acc)
+ end;
+eliminate_moves([{block,[]}|Is], D, Acc) ->
+ %% Empty blocks can prevent further jump optimizations.
+ eliminate_moves(Is, D, Acc);
+eliminate_moves([I|Is], D0, Acc) ->
+ D = update_unsafe_labels(I, D0),
+ eliminate_moves(Is, D, [I|Acc]);
+eliminate_moves([], _, Acc) -> reverse(Acc).
+
+no_fallthrough([I|_]) ->
+ is_unreachable_after(I).
+
+already_has_value(Lit, Lbl, Reg, D) ->
+ Key = {Lbl,Reg},
+ case D of
+ #{Lbl:=unsafe} ->
+ false;
+ #{Key:=Lit} ->
+ true;
+ #{} ->
+ false
+ end.
+
+update_value_dict([Lit,{f,Lbl}|T], Reg, D0) ->
+ Key = {Lbl,Reg},
+ D = case D0 of
+ #{Key := inconsistent} -> D0;
+ #{Key := _} -> D0#{Key := inconsistent};
+ _ -> D0#{Key => Lit}
+ end,
+ update_value_dict(T, Reg, D);
+update_value_dict([], _, D) -> D.
+
+update_unsafe_labels(I, D) ->
+ Ls = instr_labels(I),
+ update_unsafe_labels_1(Ls, D).
+
+update_unsafe_labels_1([L|Ls], D) ->
+ update_unsafe_labels_1(Ls, D#{L=>unsafe});
+update_unsafe_labels_1([], D) -> D.
+
+%%%
+%%% It seems to be useful to insert extra labels after certain
+%%% test instructions. This used to be done by beam_dead.
+%%%
+
+insert_labels([{test,Op,_,_}=I|Is], Lc, Acc) ->
+ Useful = case Op of
+ is_lt -> true;
+ is_ge -> true;
+ is_eq_exact -> true;
+ is_ne_exact -> true;
+ _ -> false
+ end,
+ case Useful of
+ false -> insert_labels(Is, Lc, [I|Acc]);
+ true -> insert_labels(Is, Lc+1, [{label,Lc},I|Acc])
+ end;
+insert_labels([I|Is], Lc, Acc) ->
+ insert_labels(Is, Lc, [I|Acc]);
+insert_labels([], Lc, Acc) ->
+ {reverse(Acc),Lc}.
%%%
%%% (1) We try to share the code for identical code segments by replacing all
@@ -156,41 +252,51 @@ function({function,Name,Arity,CLabel,Asm0}) ->
%%%
share(Is0) ->
- %% We will get more sharing if we never fall through to a label.
- Is = eliminate_fallthroughs(Is0, []),
- share_1(Is, #{}, [], []).
+ Is1 = eliminate_fallthroughs(Is0, []),
+ Is2 = find_fixpoint(fun(Is) ->
+ share_1(Is, #{}, #{}, [], [])
+ end, Is1),
+ reverse(Is2).
-share_1([{label,L}=Lbl|Is], Dict0, [_|_]=Seq, Acc) ->
+share_1([{label,L}=Lbl|Is], Dict0, Lbls0, [_|_]=Seq, Acc) ->
case maps:find(Seq, Dict0) of
- error ->
- Dict = maps:put(Seq, L, Dict0),
- share_1(Is, Dict, [], [Lbl|Seq ++ Acc]);
- {ok,Label} ->
- share_1(Is, Dict0, [], [Lbl,{jump,{f,Label}}|Acc])
+ error ->
+ Dict = maps:put(Seq, L, Dict0),
+ share_1(Is, Dict, Lbls0, [], [[Lbl|Seq]|Acc]);
+ {ok,Label} ->
+ Lbls = maps:put(L, Label, Lbls0),
+ share_1(Is, Dict0, Lbls, [], [[Lbl,{jump,{f,Label}}]|Acc])
end;
-share_1([{func_info,_,_,_}=I|Is], _, [], Acc) ->
- reverse(Is, [I|Acc]);
-share_1([{'catch',_,_}=I|Is], Dict0, Seq, Acc) ->
- Dict = clean_non_sharable(Dict0),
- share_1(Is, Dict, [I|Seq], Acc);
-share_1([{'try',_,_}=I|Is], Dict0, Seq, Acc) ->
- Dict = clean_non_sharable(Dict0),
- share_1(Is, Dict, [I|Seq], Acc);
-share_1([{try_case,_}=I|Is], Dict0, Seq, Acc) ->
- Dict = clean_non_sharable(Dict0),
- share_1(Is, Dict, [I|Seq], Acc);
-share_1([{catch_end,_}=I|Is], Dict0, Seq, Acc) ->
- Dict = clean_non_sharable(Dict0),
- share_1(Is, Dict, [I|Seq], Acc);
-share_1([I|Is], Dict, Seq, Acc) ->
+share_1([{func_info,_,_,_}|_]=Is0, _, Lbls, [], Acc0) when Lbls =/= #{} ->
+ lists:foldl(fun(Is, Acc) ->
+ beam_utils:replace_labels(Is, Acc, Lbls, fun(Old) -> Old end)
+ end, Is0, Acc0);
+share_1([{func_info,_,_,_}|_]=Is, _, Lbls, [], Acc) when Lbls =:= #{} ->
+ lists:foldl(fun lists:reverse/2, Is, Acc);
+share_1([{'catch',_,_}=I|Is], Dict0, Lbls0, Seq, Acc) ->
+ {Dict,Lbls} = clean_non_sharable(Dict0, Lbls0),
+ share_1(Is, Dict, Lbls, [I|Seq], Acc);
+share_1([{'try',_,_}=I|Is], Dict0, Lbls0, Seq, Acc) ->
+ {Dict,Lbls} = clean_non_sharable(Dict0, Lbls0),
+ share_1(Is, Dict, Lbls, [I|Seq], Acc);
+share_1([{try_case,_}=I|Is], Dict0, Lbls0, Seq, Acc) ->
+ {Dict,Lbls} = clean_non_sharable(Dict0, Lbls0),
+ share_1(Is, Dict, Lbls, [I|Seq], Acc);
+share_1([{catch_end,_}=I|Is], Dict0, Lbls0, Seq, Acc) ->
+ {Dict,Lbls} = clean_non_sharable(Dict0, Lbls0),
+ share_1(Is, Dict, Lbls, [I|Seq], Acc);
+share_1([{jump,{f,To}}=I,{label,L}=Lbl|Is], Dict0, Lbls0, _Seq, Acc) ->
+ Lbls = maps:put(L, To, Lbls0),
+ share_1(Is, Dict0, Lbls, [], [[Lbl,I]|Acc]);
+share_1([I|Is], Dict, Lbls, Seq, Acc) ->
case is_unreachable_after(I) of
false ->
- share_1(Is, Dict, [I|Seq], Acc);
+ share_1(Is, Dict, Lbls, [I|Seq], Acc);
true ->
- share_1(Is, Dict, [I], Acc)
+ share_1(Is, Dict, Lbls, [I], Acc)
end.
-clean_non_sharable(Dict) ->
+clean_non_sharable(Dict0, Lbls0) ->
%% We are passing in or out of a 'catch' or 'try' block. Remove
%% sequences that should not be shared over the boundaries of the
%% block. Since the end of the sequence must match, the only
@@ -198,7 +304,17 @@ clean_non_sharable(Dict) ->
%% the 'catch'/'try' block is a sequence that ends with an
%% instruction that causes an exception. Any sequence that causes
%% an exception must contain a line/1 instruction.
- maps:filter(fun(K, _V) -> sharable_with_try(K) end, Dict).
+ Dict1 = maps:to_list(Dict0),
+ Lbls1 = maps:to_list(Lbls0),
+ {Dict2,Lbls2} = foldl(fun({K, V}, {Dict,Lbls}) ->
+ case sharable_with_try(K) of
+ true ->
+ {[{K,V}|Dict],lists:keydelete(V, 2, Lbls)};
+ false ->
+ {Dict,Lbls}
+ end
+ end, {[],Lbls1}, Dict1),
+ {maps:from_list(Dict2),maps:from_list(Lbls2)}.
sharable_with_try([{line,_}|_]) ->
%% This sequence may cause an exception and may potentially
@@ -251,8 +367,6 @@ extract_seq([{line,_}=Line|Is], Acc) ->
extract_seq(Is, [Line|Acc]);
extract_seq([{block,_}=Bl|Is], Acc) ->
extract_seq_1(Is, [Bl|Acc]);
-extract_seq([{bs_context_to_binary,_}=I|Is], Acc) ->
- extract_seq_1(Is, [I|Acc]);
extract_seq([{label,_}|_]=Is, Acc) ->
extract_seq_1(Is, Acc);
extract_seq(_, _) -> no.
@@ -551,52 +665,76 @@ drop_upto_label([{label,_}|_]=Is) -> Is;
drop_upto_label([_|Is]) -> drop_upto_label(Is);
drop_upto_label([]) -> [].
-%% ulbl(Instruction, UsedGbSet) -> UsedGbSet'
-%% Update the gb_set UsedGbSet with any function-local labels
+%% ulbl(Instruction, UsedCerlSet) -> UsedCerlSet'
+%% Update the cerl_set UsedCerlSet with any function-local labels
%% (i.e. not with labels in call instructions) referenced by
%% the instruction Instruction.
%%
%% NOTE: This function does NOT look for labels inside blocks.
-ulbl({test,_,Fail,_}, Used) ->
- mark_used(Fail, Used);
-ulbl({test,_,Fail,_,_,_}, Used) ->
- mark_used(Fail, Used);
-ulbl({select,_,_,Fail,Vls}, Used) ->
- mark_used_list(Vls, mark_used(Fail, Used));
-ulbl({'try',_,Lbl}, Used) ->
- mark_used(Lbl, Used);
-ulbl({'catch',_,Lbl}, Used) ->
- mark_used(Lbl, Used);
-ulbl({jump,Lbl}, Used) ->
- mark_used(Lbl, Used);
-ulbl({loop_rec,Lbl,_}, Used) ->
- mark_used(Lbl, Used);
-ulbl({loop_rec_end,Lbl}, Used) ->
- mark_used(Lbl, Used);
-ulbl({wait,Lbl}, Used) ->
- mark_used(Lbl, Used);
-ulbl({wait_timeout,Lbl,_To}, Used) ->
- mark_used(Lbl, Used);
-ulbl({bif,_Name,Lbl,_As,_R}, Used) ->
- mark_used(Lbl, Used);
-ulbl({gc_bif,_Name,Lbl,_Live,_As,_R}, Used) ->
- mark_used(Lbl, Used);
-ulbl({bs_init,Lbl,_,_,_,_}, Used) ->
- mark_used(Lbl, Used);
-ulbl({bs_put,Lbl,_,_}, Used) ->
- mark_used(Lbl, Used);
-ulbl({put_map,Lbl,_Op,_Src,_Dst,_Live,_List}, Used) ->
- mark_used(Lbl, Used);
-ulbl({get_map_elements,Lbl,_Src,_List}, Used) ->
- mark_used(Lbl, Used);
-ulbl(_, Used) -> Used.
-
-mark_used({f,0}, Used) -> Used;
-mark_used({f,L}, Used) -> cerl_sets:add_element(L, Used).
-
-mark_used_list([{f,L}|T], Used) ->
- mark_used_list(T, cerl_sets:add_element(L, Used));
-mark_used_list([_|T], Used) ->
- mark_used_list(T, Used);
-mark_used_list([], Used) -> Used.
+ulbl(I, Used) ->
+ case instr_labels(I) of
+ [] ->
+ Used;
+ [Lbl] ->
+ cerl_sets:add_element(Lbl, Used);
+ [_|_]=L ->
+ ulbl_list(L, Used)
+ end.
+
+ulbl_list([L|Ls], Used) ->
+ ulbl_list(Ls, cerl_sets:add_element(L, Used));
+ulbl_list([], Used) -> Used.
+
+-spec instr_labels(Instruction) -> Labels when
+ Instruction :: instruction(),
+ Labels :: [beam_asm:label()].
+
+instr_labels({test,_,Fail,_}) ->
+ do_instr_labels(Fail);
+instr_labels({test,_,Fail,_,_,_}) ->
+ do_instr_labels(Fail);
+instr_labels({select,_,_,Fail,Vls}) ->
+ do_instr_labels_list(Vls, do_instr_labels(Fail));
+instr_labels({'try',_,Lbl}) ->
+ do_instr_labels(Lbl);
+instr_labels({'catch',_,Lbl}) ->
+ do_instr_labels(Lbl);
+instr_labels({jump,Lbl}) ->
+ do_instr_labels(Lbl);
+instr_labels({loop_rec,Lbl,_}) ->
+ do_instr_labels(Lbl);
+instr_labels({loop_rec_end,Lbl}) ->
+ do_instr_labels(Lbl);
+instr_labels({wait,Lbl}) ->
+ do_instr_labels(Lbl);
+instr_labels({wait_timeout,Lbl,_To}) ->
+ do_instr_labels(Lbl);
+instr_labels({bif,_Name,Lbl,_As,_R}) ->
+ do_instr_labels(Lbl);
+instr_labels({gc_bif,_Name,Lbl,_Live,_As,_R}) ->
+ do_instr_labels(Lbl);
+instr_labels({bs_init,Lbl,_,_,_,_}) ->
+ do_instr_labels(Lbl);
+instr_labels({bs_put,Lbl,_,_}) ->
+ do_instr_labels(Lbl);
+instr_labels({put_map,Lbl,_Op,_Src,_Dst,_Live,_List}) ->
+ do_instr_labels(Lbl);
+instr_labels({get_map_elements,Lbl,_Src,_List}) ->
+ do_instr_labels(Lbl);
+instr_labels({recv_mark,Lbl}) ->
+ do_instr_labels(Lbl);
+instr_labels({recv_set,Lbl}) ->
+ do_instr_labels(Lbl);
+instr_labels({fcheckerror,Lbl}) ->
+ do_instr_labels(Lbl);
+instr_labels(_) -> [].
+
+do_instr_labels({f,0}) -> [];
+do_instr_labels({f,F}) -> [F].
+
+do_instr_labels_list([{f,F}|T], Acc) ->
+ do_instr_labels_list(T, [F|Acc]);
+do_instr_labels_list([_|T], Acc) ->
+ do_instr_labels_list(T, Acc);
+do_instr_labels_list([], Acc) -> Acc.
generated by cgit v1.2.3 (git 2.25.1) at 2024-12-24 20:18:13 +0000