5 files changed, 127 insertions, 1 deletions
diff --git a/lib/compiler/src/Makefile b/lib/compiler/src/Makefile
index 299b2892fc..ae4007c61c 100644
--- a/lib/compiler/src/Makefile
+++ b/lib/compiler/src/Makefile
@@ -62,6 +62,7 @@ MODULES =  \
 	beam_opcodes \
 	beam_peep \
 	beam_receive \
+	beam_reorder \
 	beam_split \
 	beam_trim \
 	beam_type \
diff --git a/lib/compiler/src/beam_reorder.erl b/lib/compiler/src/beam_reorder.erl
new file mode 100644
index 0000000000..3230e33dbd
--- /dev/null
+++ b/lib/compiler/src/beam_reorder.erl
@@ -0,0 +1,113 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1999-2013. 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.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+-module(beam_reorder).
+
+-export([module/2]).
+-import(lists, [member/2,reverse/1]).
+
+module({Mod,Exp,Attr,Fs0,Lc}, _Opt) ->
+    Fs = [function(F) || F <- Fs0],
+    {ok,{Mod,Exp,Attr,Fs,Lc}}.
+
+function({function,Name,Arity,CLabel,Is0}) ->
+    try
+	Is = reorder(Is0),
+	{function,Name,Arity,CLabel,Is}
+    catch
+	Class:Error ->
+	    Stack = erlang:get_stacktrace(),
+	    io:fwrite("Function: ~w/~w\n", [Name,Arity]),
+	    erlang:raise(Class, Error, Stack)
+    end.
+
+%% reorder(Instructions0) -> Instructions
+%%  Reorder instructions before the beam_block pass, because reordering
+%%  will be more cumbersome when the blocks are in place.
+%%
+%%  Execution of get_tuple_element instructions can be delayed until
+%%  they are actually needed. Consider the sequence:
+%%
+%%      get_tuple_element Tuple Pos Dst
+%%      test Test Fail Operands
+%%
+%%  If Dst is killed at label Fail (and not referenced in Operands),
+%%  we can can swap the instructions:
+%%
+%%      test Test Fail Operands
+%%      get_tuple_element Tuple Pos Dst
+%%
+%%  That can be beneficial in two ways: Firstly, if the branch is taken
+%%  we have avoided execution of the get_tuple_element instruction.
+%%  Secondly, even if the branch is not taken, subsequent optimization
+%%  (opt_blocks/1) may be able to change Dst to the final destination
+%%  register and eliminate a 'move' instruction.
+
+reorder(Is) ->
+    D = beam_utils:index_labels(Is),
+    reorder_1(Is, D, []).
+
+reorder_1([{label,L}=I|_], D, Acc) ->
+    Is = beam_utils:code_at(L, D),
+    reorder_1(Is, D, [I|Acc]);
+reorder_1([{test,is_nonempty_list,_,_}=I|Is], D, Acc) ->
+    %% The run-time system may combine the is_nonempty_list test with
+    %% the following get_list instruction.
+    reorder_1(Is, D, [I|Acc]);
+reorder_1([{test,_,_,_}=I,
+	   {select,_,_,_,_}=S|Is], D, Acc) ->
+    %% There is nothing to gain by inserting a get_tuple_element
+    %% instruction between the test instruction and the select
+    %% instruction.
+    reorder_1(Is, D, [S,I|Acc]);
+reorder_1([{test,_,{f,L},Ss}=I|Is0], D0,
+	  [{get_tuple_element,_,_,El}=G|Acc0]=Acc) ->
+    case member(El, Ss) of
+	true ->
+	    reorder_1(Is0, D0, [I|Acc]);
+	false ->
+	    case beam_utils:is_killed_at(El, L, D0) of
+		true ->
+		    Is = [I,G|Is0],
+		    reorder_1(Is, D0, Acc0);
+		false ->
+		    case beam_utils:is_killed(El, Is0, D0) of
+			true ->
+			    Code0 = beam_utils:code_at(L, D0),
+			    Code = [G|Code0],
+			    D = beam_utils:index_label(L, Code, D0),
+			    Is = [I|Is0],
+			    reorder_1(Is, D, Acc0);
+			false ->
+			    reorder_1(Is0, D0, [I|Acc])
+		    end
+	    end
+    end;
+reorder_1([{allocate_zero,N,Live}|Is], D,
+	  [{get_tuple_element,_,_,{x,X}}=G|Acc])
+  when X+1 =:= Live ->
+    %% Move allocation instruction upwards past get_tuple_element
+    %% instructions to give more opportunities for moving
+    %% get_tuple_element instructions.
+    I = {allocate_zero,N,X},
+    reorder_1([I,G|Is], D, Acc);
+reorder_1([I|Is], D, Acc) ->
+    reorder_1(Is, D, [I|Acc]);
+reorder_1([], _, Acc) -> reverse(Acc).
diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl
index fbcd5de1bb..68d6105cfa 100644
--- a/lib/compiler/src/beam_utils.erl
+++ b/lib/compiler/src/beam_utils.erl
@@ -484,6 +484,15 @@ check_liveness(R, [{get_map_elements,{f,Fail},S,{list,L}}|Is], St0) ->
 		    Other
 	    end
     end;
+check_liveness(R, [{test_heap,N,Live}|Is], St) ->
+    I = {block,[{set,[],[],{alloc,Live,{nozero,nostack,N,[]}}}]},
+    check_liveness(R, [I|Is], St);
+check_liveness(R, [{allocate_zero,N,Live}|Is], St) ->
+    I = {block,[{set,[],[],{alloc,Live,{zero,N,0,[]}}}]},
+    check_liveness(R, [I|Is], St);
+check_liveness(R, [{get_list,S,D1,D2}|Is], St) ->
+    I = {block,[{set,[D1,D2],[S],get_list}]},
+    check_liveness(R, [I|Is], St);
 check_liveness(_R, Is, St) when is_list(Is) ->
 %%     case Is of
 %% 	[I|_] ->
diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index cf79fdc9f9..605f5b8fd5 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -673,7 +673,9 @@ asm_passes() ->
       [{pass,beam_a},
        {iff,da,{listing,"a"}},
        {unless,no_postopt,
-	[{pass,beam_block},
+	[{unless,no_reorder,{pass,beam_reorder}},
+	 {iff,dre,{listing,"reorder"}},
+	 {pass,beam_block},
 	 {iff,dblk,{listing,"block"}},
 	 {unless,no_except,{pass,beam_except}},
 	 {iff,dexcept,{listing,"except"}},
diff --git a/lib/compiler/src/compiler.app.src b/lib/compiler/src/compiler.app.src
index afb85f4710..62ea9cee80 100644
--- a/lib/compiler/src/compiler.app.src
+++ b/lib/compiler/src/compiler.app.src
@@ -37,6 +37,7 @@
 	     beam_opcodes,
 	     beam_peep,
 	     beam_receive,
+	     beam_reorder,
 	     beam_split,
 	     beam_trim,
 	     beam_type,