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-rw-r--r--lib/compiler/src/beam_jump.erl156
1 files changed, 95 insertions, 61 deletions
diff --git a/lib/compiler/src/beam_jump.erl b/lib/compiler/src/beam_jump.erl
index 4365451356..22974da398 100644
--- a/lib/compiler/src/beam_jump.erl
+++ b/lib/compiler/src/beam_jump.erl
@@ -1,7 +1,7 @@
%%
%% %CopyrightBegin%
%%
-%% Copyright Ericsson AB 1999-2016. All Rights Reserved.
+%% Copyright Ericsson AB 1999-2018. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
@@ -71,9 +71,9 @@
%%%
%%% jump L2
%%% . . .
-%%% L1:
%%% L2: ...
%%%
+%%% and all preceding uses of L1 renamed to L2.
%%% If the jump is unreachable, it will be removed according to (1).
%%%
%%% (5) In
@@ -128,7 +128,7 @@
%%% on the program state.
%%%
--import(lists, [reverse/1,reverse/2,foldl/3]).
+-import(lists, [dropwhile/2,reverse/1,reverse/2,foldl/3]).
-type instruction() :: beam_utils:instruction().
@@ -275,14 +275,15 @@ extract_seq_1(_, _) -> no.
-record(st,
{
entry :: beam_asm:label(), %Entry label (must not be moved).
- mlbl :: #{beam_asm:label() := [beam_asm:label()]}, %Moved labels.
- labels :: cerl_sets:set() %Set of referenced labels.
+ replace :: #{beam_asm:label() := beam_asm:label()}, %Labels to replace.
+ labels :: cerl_sets:set(), %Set of referenced labels.
+ index :: beam_utils:code_index() | {lazy,[beam_utils:instruction()]} %Index built lazily only if needed
}).
opt(Is0, CLabel) ->
find_fixpoint(fun(Is) ->
Lbls = initial_labels(Is),
- St = #st{entry=CLabel,mlbl=#{},labels=Lbls},
+ St = #st{entry=CLabel,replace=#{},labels=Lbls,index={lazy,Is}},
opt(Is, [], St)
end, Is0).
@@ -292,7 +293,7 @@ find_fixpoint(OptFun, Is0) ->
Is -> find_fixpoint(OptFun, Is)
end.
-opt([{test,_,{f,L}=Lbl,_}=I|[{jump,{f,L}}|_]=Is], Acc, St) ->
+opt([{test,_,{f,L}=Lbl,_}=I|[{jump,{f,L}}|_]=Is], Acc0, St0) ->
%% We have
%% Test Label Ops
%% jump Label
@@ -301,10 +302,23 @@ opt([{test,_,{f,L}=Lbl,_}=I|[{jump,{f,L}}|_]=Is], Acc, St) ->
case beam_utils:is_pure_test(I) of
false ->
%% Test is not pure; we must keep it.
- opt(Is, [I|Acc], label_used(Lbl, St));
+ opt(Is, [I|Acc0], label_used(Lbl, St0));
true ->
%% The test is pure and its failure label is the same
%% as in the jump that follows -- thus it is not needed.
+ %% Check if any of the previous instructions could also be eliminated.
+ {Acc,St} = opt_useless_loads(Acc0, L, St0),
+ opt(Is, Acc, St)
+ end;
+opt([{test,_,{f,L}=Lbl,_}=I|[{label,L}|_]=Is], Acc0, St0) ->
+ %% Similar to the above, except we have a fall-through rather than jump
+ %% Test Label Ops
+ %% label Label
+ case beam_utils:is_pure_test(I) of
+ false ->
+ opt(Is, [I|Acc0], label_used(Lbl, St0));
+ true ->
+ {Acc,St} = opt_useless_loads(Acc0, L, St0),
opt(Is, Acc, St)
end;
opt([{test,Test0,{f,L}=Lbl,Ops}=I|[{jump,To}|Is]=Is0], Acc, St) ->
@@ -326,30 +340,16 @@ opt([{test,_,{f,_}=Lbl,_,_,_}=I|Is], Acc, St) ->
opt(Is, [I|Acc], label_used(Lbl, St));
opt([{select,_,_R,Fail,Vls}=I|Is], Acc, St) ->
skip_unreachable(Is, [I|Acc], label_used([Fail|Vls], St));
-opt([{label,Lbl}=I|Is], Acc, #st{mlbl=Mlbl}=St0) ->
- case maps:find(Lbl, Mlbl) of
- {ok,Lbls} ->
- %% Essential to remove the list of labels from the dictionary,
- %% since we will rescan the inserted labels. We MUST rescan.
- St = St0#st{mlbl=maps:remove(Lbl, Mlbl)},
- insert_labels([Lbl|Lbls], Is, Acc, St);
- error ->
- opt(Is, [I|Acc], St0)
- end;
+opt([{label,From}=I,{label,To}|Is], Acc, #st{replace=Replace}=St) ->
+ opt([I|Is], Acc, St#st{replace=Replace#{To => From}});
opt([{jump,{f,_}=X}|[{label,_},{jump,X}|_]=Is], Acc, St) ->
opt(Is, Acc, St);
opt([{jump,{f,Lbl}}|[{label,Lbl}|_]=Is], Acc, St) ->
opt(Is, Acc, St);
-opt([{jump,{f,L}=Lbl}=I|Is], Acc0, #st{mlbl=Mlbl0}=St0) ->
- %% All labels before this jump instruction should now be
- %% moved to the location of the jump's target.
- {Lbls,Acc} = collect_labels(Acc0, St0),
- St = case Lbls of
- [] -> St0;
- [_|_] ->
- Mlbl = maps_append_list(L, Lbls, Mlbl0),
- St0#st{mlbl=Mlbl}
- end,
+opt([{jump,{f,L}=Lbl}=I|Is], Acc0, St0) ->
+ %% Replace all labels before this jump instruction into the
+ %% location of the jump's target.
+ {Acc,St} = collect_labels(Acc0, L, St0),
skip_unreachable(Is, [I|Acc], label_used(Lbl, St));
%% Optimization: quickly handle some common instructions that don't
%% have any failure labels and where is_unreachable_after(I) =:= false.
@@ -369,36 +369,77 @@ opt([I|Is], Acc, #st{labels=Used0}=St0) ->
true -> skip_unreachable(Is, [I|Acc], St);
false -> opt(Is, [I|Acc], St)
end;
-opt([], Acc, #st{mlbl=Mlbl}) ->
- Code = reverse(Acc),
- insert_fc_labels(Code, Mlbl).
-
-insert_fc_labels([{label,L}=I|Is0], Mlbl) ->
- case maps:find(L, Mlbl) of
- error ->
- [I|insert_fc_labels(Is0, Mlbl)];
- {ok,Lbls} ->
- Is = [{label,Lb} || Lb <- Lbls] ++ Is0,
- [I|insert_fc_labels(Is, maps:remove(L, Mlbl))]
+opt([], Acc, #st{replace=Replace0}) when Replace0 =/= #{} ->
+ Replace = normalize_replace(maps:to_list(Replace0), Replace0, []),
+ beam_utils:replace_labels(Acc, [], Replace, fun(Old) -> Old end);
+opt([], Acc, #st{replace=Replace}) when Replace =:= #{} ->
+ reverse(Acc).
+
+normalize_replace([{From,To0}|Rest], Replace, Acc) ->
+ case Replace of
+ #{To0 := To} ->
+ normalize_replace([{From,To}|Rest], Replace, Acc);
+ _ ->
+ normalize_replace(Rest, Replace, [{From,To0}|Acc])
end;
-insert_fc_labels([_|_]=Is, _) -> Is.
-
-maps_append_list(K,Vs,M) ->
- case M of
- #{K:=Vs0} -> M#{K:=Vs0++Vs}; % same order as dict
- _ -> M#{K => Vs}
- end.
+normalize_replace([], _Replace, Acc) ->
+ maps:from_list(Acc).
+
+%% After eliminating a test, it might happen, that a register was only used
+%% in this test. Let's check if that was the case and if it was so, we can
+%% eliminate the load into the register completely.
+opt_useless_loads([{block,_}|_]=Is, L, #st{index={lazy,FIs}}=St) ->
+ opt_useless_loads(Is, L, St#st{index=beam_utils:index_labels(FIs)});
+opt_useless_loads([{block,Block0}|Is], L, #st{index=Index}=St) ->
+ case opt_useless_block_loads(Block0, L, Index) of
+ [] ->
+ opt_useless_loads(Is, L, St);
+ [_|_]=Block ->
+ {[{block,Block}|Is],St}
+ end;
+%% After eliminating the test and useless blocks, it might happen,
+%% that the previous test could also be eliminated.
+%% It might be that the label was already marked as used, even if ultimately,
+%% it never will be - we can't do much about it at that point, though
+opt_useless_loads([{test,_,{f,L},_}=I|Is], L, St) ->
+ case beam_utils:is_pure_test(I) of
+ false ->
+ {[I|Is],St};
+ true ->
+ opt_useless_loads(Is, L, St)
+ end;
+opt_useless_loads(Is, _L, St) ->
+ {Is,St}.
+
+opt_useless_block_loads([{set,[Dst],_,_}=I|Is0], L, Index) ->
+ BlockJump = [{block,Is0},{jump,{f,L}}],
+ case beam_utils:is_killed(Dst, BlockJump, Index) of
+ true ->
+ %% The register is killed and not used, we can remove the load.
+ %% Remove any `put` instructions in case we just
+ %% removed a `put_tuple` instruction.
+ Is = dropwhile(fun({set,_,_,put}) -> true;
+ (_) -> false
+ end, Is0),
+ opt_useless_block_loads(Is, L, Index);
+ false ->
+ [I|opt_useless_block_loads(Is0, L, Index)]
+ end;
+opt_useless_block_loads([I|Is], L, Index) ->
+ [I|opt_useless_block_loads(Is, L, Index)];
+opt_useless_block_loads([], _L, _Index) ->
+ [].
-collect_labels(Is, #st{entry=Entry}) ->
- collect_labels_1(Is, Entry, []).
+collect_labels(Is, Label, #st{entry=Entry,replace=Replace} = St) ->
+ collect_labels_1(Is, Label, Entry, Replace, St).
-collect_labels_1([{label,Entry}|_]=Is, Entry, Acc) ->
+collect_labels_1([{label,Entry}|_]=Is, _Label, Entry, Acc, St) ->
%% Never move the entry label.
- {Acc,Is};
-collect_labels_1([{label,L}|Is], Entry, Acc) ->
- collect_labels_1(Is, Entry, [L|Acc]);
-collect_labels_1(Is, _Entry, Acc) ->
- {Acc,Is}.
+ {Is,St#st{replace=Acc}};
+collect_labels_1([{label,L}|Is], Label, Entry, Acc, St) ->
+ collect_labels_1(Is, Label, Entry, Acc#{L => Label}, St);
+collect_labels_1(Is, _Label, _Entry, Acc, St) ->
+ {Is,St#st{replace=Acc}}.
%% label_defined(Is, Label) -> true | false.
%% Test whether the label Label is defined at the start of the instruction
@@ -418,13 +459,6 @@ invert_test(is_eq_exact) -> is_ne_exact;
invert_test(is_ne_exact) -> is_eq_exact;
invert_test(_) -> not_possible.
-insert_labels([L|Ls], Is, [{jump,{f,L}}|Acc], St) ->
- insert_labels(Ls, [{label,L}|Is], Acc, St);
-insert_labels([L|Ls], Is, Acc, St) ->
- insert_labels(Ls, [{label,L}|Is], Acc, St);
-insert_labels([], Is, Acc, St) ->
- opt(Is, Acc, St).
-
%% skip_unreachable([Instruction], St).
%% Remove all instructions (including definitions of labels
%% that have not been referenced yet) up to the next
generated by cgit v1.2.3 (git 2.25.1) at 2024-12-18 02:12:09 +0000