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-rw-r--r--lib/compiler/src/beam_block.erl53
1 files changed, 52 insertions, 1 deletions
diff --git a/lib/compiler/src/beam_block.erl b/lib/compiler/src/beam_block.erl
index af1bf8fd08..49e66b379b 100644
--- a/lib/compiler/src/beam_block.erl
+++ b/lib/compiler/src/beam_block.erl
@@ -183,7 +183,9 @@ opt_blocks([I|Is]) ->
opt_blocks([]) -> [].
opt_block(Is0) ->
- Is = find_fixpoint(fun opt/1, Is0),
+ Is = find_fixpoint(fun(Is) ->
+ opt_tuple_element(opt(Is))
+ end, Is0),
opt_alloc(Is).
find_fixpoint(OptFun, Is0) ->
@@ -315,6 +317,55 @@ opt_move_1(R, [{set,_,_,_}=I|Is], Acc) ->
opt_move_1(_, _, _) ->
not_possible.
+%% opt_tuple_element([Instruction]) -> [Instruction]
+%% If possible, move get_tuple_element instructions forward
+%% in the instruction stream to a move instruction, eliminating
+%% the move instruction. Example:
+%%
+%% get_tuple_element Tuple Pos Dst1
+%% ...
+%% move Dst1 Dst2
+%%
+%% This code may be possible to rewrite to:
+%%
+%% %%(Moved get_tuple_element instruction)
+%% ...
+%% get_tuple_element Tuple Pos Dst2
+%%
+
+opt_tuple_element([{set,[D],[S],{get_tuple_element,_}}=I|Is0]) ->
+ case opt_tuple_element_1(Is0, I, {S,D}, []) of
+ no ->
+ [I|opt_tuple_element(Is0)];
+ {yes,Is} ->
+ opt_tuple_element(Is)
+ end;
+opt_tuple_element([I|Is]) ->
+ [I|opt_tuple_element(Is)];
+opt_tuple_element([]) -> [].
+
+opt_tuple_element_1([{set,_,_,{alloc,_,_}}|_], _, _, _) ->
+ no;
+opt_tuple_element_1([{set,_,_,{'catch',_}}|_], _, _, _) ->
+ no;
+opt_tuple_element_1([{set,[D],[S],move}|Is0], I0, {_,S}, Acc) ->
+ case eliminate_use_of_from_reg(Is0, S, D, []) of
+ no ->
+ no;
+ {yes,Is} ->
+ {set,[S],Ss,Op} = I0,
+ I = {set,[D],Ss,Op},
+ {yes,reverse(Acc, [I|Is])}
+ end;
+opt_tuple_element_1([{set,Ds,Ss,_}=I|Is], MovedI, {S,D}=Regs, Acc) ->
+ case member(S, Ds) orelse member(D, Ss) of
+ true ->
+ no;
+ false ->
+ opt_tuple_element_1(Is, MovedI, Regs, [I|Acc])
+ end;
+opt_tuple_element_1(_, _, _, _) -> no.
+
%% Reverse the instructions, while checking that there are no
%% instructions that would interfere with using the new destination
%% register (D).