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authorBjörn Gustavsson <[email protected]>2018-11-01 07:24:46 +0100
committerBjörn Gustavsson <[email protected]>2018-11-06 10:16:53 +0100
commit181cfc4ef9d120c1188c8f28f306d7b0f106a80b (patch)
treeee32f06f0de0f51b750b93587a12076219815b02 /lib/compiler
parente7b3dcde36969be9442e05b18919ecb5b61bf6a4 (diff)
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beam_jump: Stop using beam_utils:is_killed/3
Prior to this commit, the optimizations using beam_utils:is_killed/3 were only executed a few times in the entire compiler test suite.
Diffstat (limited to 'lib/compiler')
-rw-r--r--lib/compiler/src/beam_jump.erl58
1 files changed, 5 insertions, 53 deletions
diff --git a/lib/compiler/src/beam_jump.erl b/lib/compiler/src/beam_jump.erl
index 40a2211325..d3a618d211 100644
--- a/lib/compiler/src/beam_jump.erl
+++ b/lib/compiler/src/beam_jump.erl
@@ -128,7 +128,7 @@
%%% on the program state.
%%%
--import(lists, [dropwhile/2,foldl/3,mapfoldl/3,reverse/1,reverse/2]).
+-import(lists, [foldl/3,mapfoldl/3,reverse/1,reverse/2]).
-type instruction() :: beam_utils:instruction().
@@ -410,7 +410,7 @@ find_fixpoint(OptFun, Is0) ->
Is -> find_fixpoint(OptFun, Is)
end.
-opt([{test,_,{f,L}=Lbl,_}=I|[{jump,{f,L}}|_]=Is], Acc0, St0) ->
+opt([{test,_,{f,L}=Lbl,_}=I|[{jump,{f,L}}|_]=Is], Acc, St) ->
%% We have
%% Test Label Ops
%% jump Label
@@ -419,23 +419,20 @@ opt([{test,_,{f,L}=Lbl,_}=I|[{jump,{f,L}}|_]=Is], Acc0, St0) ->
case beam_utils:is_pure_test(I) of
false ->
%% Test is not pure; we must keep it.
- opt(Is, [I|Acc0], label_used(Lbl, St0));
+ opt(Is, [I|Acc], label_used(Lbl, St));
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) ->
+opt([{test,_,{f,L}=Lbl,_}=I|[{label,L}|_]=Is], Acc, St) ->
%% 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));
+ opt(Is, [I|Acc], label_used(Lbl, St));
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) ->
@@ -502,51 +499,6 @@ normalize_replace([{From,To0}|Rest], Replace, Acc) ->
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, Label, #st{entry=Entry,replace=Replace} = St) ->
collect_labels_1(Is, Label, Entry, Replace, St).