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authorBjörn Gustavsson <[email protected]>2019-02-10 13:59:54 +0100
committerBjörn Gustavsson <[email protected]>2019-02-11 15:34:46 +0100
commit92c1920cb69fe7f3be202c6f77395c2cdbcb771e (patch)
tree292e7e6c62a1f4bb679c5b56359df56f6df77535 /lib/compiler
parentab5debc0869dbfa64e4afd4cd59404a56ce51d71 (diff)
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beam_jump: Improve elimination of redundant moves
Diffstat (limited to 'lib/compiler')
-rw-r--r--lib/compiler/src/beam_jump.erl43
1 files changed, 24 insertions, 19 deletions
diff --git a/lib/compiler/src/beam_jump.erl b/lib/compiler/src/beam_jump.erl
index 8b0e3e32f8..6f50bfdb9c 100644
--- a/lib/compiler/src/beam_jump.erl
+++ b/lib/compiler/src/beam_jump.erl
@@ -182,18 +182,20 @@ 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) ->
+eliminate_moves([{test,is_eq_exact,_,[Reg,Val]}=I,
+ {block,BlkIs0}|Is], D0, Acc) ->
+ D = update_unsafe_labels(I, D0),
+ RegVal = {Reg,Val},
+ BlkIs = eliminate_moves_blk(BlkIs0, RegVal),
+ eliminate_moves([{block,BlkIs}|Is], D, [I|Acc]);
+eliminate_moves([{label,Lbl},{block,BlkIs0}=Blk|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)
+ case {no_fallthrough(Acc0),D} of
+ {true,#{Lbl:={_,_}=RegVal}} ->
+ BlkIs = eliminate_moves_blk(BlkIs0, RegVal),
+ eliminate_moves([{block,BlkIs}|Is], D, Acc);
+ {_,_} ->
+ eliminate_moves([Blk|Is], D, Acc)
end;
eliminate_moves([{block,[]}|Is], D, Acc) ->
%% Empty blocks can prevent further jump optimizations.
@@ -203,17 +205,20 @@ eliminate_moves([I|Is], D0, Acc) ->
eliminate_moves(Is, D, [I|Acc]);
eliminate_moves([], _, Acc) -> reverse(Acc).
+eliminate_moves_blk([{set,[Dst],[_],move}|_]=Is, {_,Dst}) ->
+ Is;
+eliminate_moves_blk([{set,[Dst],[Lit],move}|Is], {Dst,Lit}) ->
+ %% Remove redundant 'move' instruction.
+ Is;
+eliminate_moves_blk([{set,[Dst],[_],move}|_]=Is, {Dst,_}) ->
+ Is;
+eliminate_moves_blk([{set,[_],[_],move}=I|Is], {_,_}=RegVal) ->
+ [I|eliminate_moves_blk(Is, RegVal)];
+eliminate_moves_blk(Is, _) -> Is.
+
no_fallthrough([I|_]) ->
is_unreachable_after(I).
-already_has_value(Lit, Lbl, Reg, D) ->
- case D of
- #{Lbl:={Reg,Lit}} ->
- true;
- #{} ->
- false
- end.
-
update_value_dict([Lit,{f,Lbl}|T], Reg, D0) ->
D = case D0 of
#{Lbl:=unsafe} -> D0;