Merge branch 'bjorn/compiler/opt/OTP-12951'

* bjorn/compiler/opt/OTP-12951:
  beam_validator: Don't allow x(1023) to be used
  v3_core: Improve code generation for guards
  Move rewriting of select_val to is_boolean from beam_peep to beam_dead
  Put 'try' in blocks to optimize allocation instructions
  Reorder instructions across try/catch
  Delay get_tuple_element instructions until they are needed
  Optimize get_tuple_element instructions by moving them forward
  beam_block: Improve the move optimizations
  beam_block: Clean up optimization of move optimizations
  beam_block: Eliminate redundant wasteful call to opt/1
  Teach the compiler the 'da' and 'dz' options

18 files changed, 343 insertions, 109 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_block.erl b/lib/compiler/src/beam_block.erl
index 2def3de7f3..4e179daa0e 100644
--- a/lib/compiler/src/beam_block.erl
+++ b/lib/compiler/src/beam_block.erl
@@ -24,7 +24,6 @@
 
 -export([module/2]).
 -import(lists, [mapfoldl/3,reverse/1,reverse/2,foldl/3,member/2]).
--define(MAXREG, 1024).
 
 module({Mod,Exp,Attr,Fs0,Lc0}, _Opt) ->
     {Fs,Lc} = mapfoldl(fun function/2, Lc0, Fs0),
@@ -149,7 +148,10 @@ collect({put_map,F,Op,S,D,R,{list,Puts}}) ->
 collect({get_map_elements,F,S,{list,Gets}}) ->
     {Ss,Ds} = beam_utils:split_even(Gets),
     {set,Ds,[S|Ss],{get_map_elements,F}};
-collect({'catch',R,L})       -> {set,[R],[],{'catch',L}};
+collect({'catch'=Op,R,L}) ->
+    {set,[R],[],{try_catch,Op,L}};
+collect({'try'=Op,R,L}) ->
+    {set,[R],[],{try_catch,Op,L}};
 collect(fclearerror)         -> {set,[],[],fclearerror};
 collect({fcheckerror,{f,0}}) -> {set,[],[],fcheckerror};
 collect({fmove,S,D})         -> {set,[D],[S],fmove};
@@ -183,7 +185,9 @@ 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) ->
@@ -287,66 +291,145 @@ opt_moves(Ds, Is) ->
 %%  If there is a {move,Dest,FinalDest} instruction
 %%  in the instruction stream, remove the move instruction
 %%  and let FinalDest be the destination.
-%%
-%%  For this optimization to be safe, we must be sure that
-%%  Dest will not be referenced in any other by other instructions
-%%  in the rest of the instruction stream. Not even the indirect
-%%  reference by an instruction that may allocate (such as
-%%  test_heap/2 or a GC Bif) is allowed.
 
 opt_move(Dest, Is) ->
-    opt_move_1(Dest, Is, ?MAXREG, []).
-
-opt_move_1(R, [{set,_,_,{alloc,Live,_}}|_]=Is, SafeRegs, Acc) when Live < SafeRegs ->
-    %% Downgrade number of safe regs and rescan the instruction, as it most probably
-    %% is a gc_bif instruction.
-    opt_move_1(R, Is, Live, Acc);
-opt_move_1(R, [{set,[{x,X}=D],[R],move}|Is], SafeRegs, Acc) ->
-    case X < SafeRegs andalso beam_utils:is_killed_block(R, Is) of
-	true -> opt_move_2(D, Acc, Is);
-	false -> not_possible
+    opt_move_1(Dest, Is, []).
+
+opt_move_1(R, [{set,[D],[R],move}|Is0], Acc) ->
+    %% Provided that the source register is killed by instructions
+    %% that follow, the optimization is safe.
+    case eliminate_use_of_from_reg(Is0, R, D, []) of
+	{yes,Is} -> opt_move_rev(D, Acc, Is);
+	no -> not_possible
     end;
-opt_move_1(R, [{set,[D],[R],move}|Is], _SafeRegs, Acc) ->
-    case beam_utils:is_killed_block(R, Is) of
-	true -> opt_move_2(D, Acc, Is);
-	false -> not_possible
+opt_move_1({x,_}, [{set,_,_,{alloc,_,_}}|_], _) ->
+    %% The optimization is not possible. If the X register is not
+    %% killed by allocation, the optimization would not be safe.
+    %% If the X register is killed, it means that there cannot
+    %% follow a 'move' instruction with this X register as the
+    %% source.
+    not_possible;
+opt_move_1(R, [{set,_,_,_}=I|Is], Acc) ->
+    %% If the source register is either killed or used by this
+    %% instruction, the optimimization is not possible.
+    case is_killed_or_used(R, I) of
+	true -> not_possible;
+	false -> opt_move_1(R, Is, [I|Acc])
     end;
-opt_move_1(R, [I|Is], SafeRegs, Acc) ->
-    case is_transparent(R, I) of
-	false -> not_possible;
-	true -> opt_move_1(R, Is, SafeRegs, [I|Acc])
-    end.
+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,_,_,{try_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 chosen.
+%% Reverse the instructions, while checking that there are no
+%% instructions that would interfere with using the new destination
+%% register (D).
 
-opt_move_2(D, [I|Is], Acc) ->
-    case is_transparent(D, I) of
-	false -> not_possible;
-	true -> opt_move_2(D, Is, [I|Acc])
+opt_move_rev(D, [I|Is], Acc) ->
+    case is_killed_or_used(D, I) of
+	true -> not_possible;
+	false -> opt_move_rev(D, Is, [I|Acc])
+    end;
+opt_move_rev(D, [], Acc) -> {D,Acc}.
+
+%% is_killed_or_used(Register, {set,_,_,_}) -> bool()
+%%  Test whether the register is used by the instruction.
+
+is_killed_or_used(R, {set,Ss,Ds,_}) ->
+    member(R, Ds) orelse member(R, Ss).
+
+%% eliminate_use_of_from_reg([Instruction], FromRegister, ToRegister, Acc) ->
+%%       {yes,Is} | no
+%%  Eliminate any use of FromRegister in the instruction sequence
+%%  by replacing uses of FromRegister with ToRegister. If FromRegister
+%%  is referenced by an allocation instruction, return 'no' to indicate
+%%  that FromRegister is still used and that the optimization is not
+%%  possible.
+
+eliminate_use_of_from_reg([{set,_,_,{alloc,Live,_}}|_]=Is0, {x,X}, _, Acc) ->
+    if
+	X < Live ->
+	    no;
+	true ->
+	    {yes,reverse(Acc, Is0)}
     end;
-opt_move_2(D, [], Acc) -> {D,Acc}.
-
-%% is_transparent(Register, Instruction) -> true | false
-%%  Returns true if Instruction does not in any way references Register
-%%  (even indirectly by an allocation instruction).
-%%  Returns false if Instruction does reference Register, or we are
-%%  not sure.
-
-is_transparent({x,X}, {set,_,_,{alloc,Live,_}}) when X < Live ->
-    false;
-is_transparent(R, {set,Ds,Ss,_Op}) ->
-    case member(R, Ds) of
-	true -> false;
-	false -> not member(R, Ss)
+eliminate_use_of_from_reg([{set,Ds,Ss0,Op}=I0|Is], From, To, Acc) ->
+    I = case member(From, Ss0) of
+	    true ->
+		Ss = [case S of
+			  From -> To;
+			  _ -> S
+		      end || S <- Ss0],
+		{set,Ds,Ss,Op};
+	    false ->
+		I0
+	end,
+    case member(From, Ds) of
+	true ->
+	    {yes,reverse(Acc, [I|Is])};
+	false ->
+	    eliminate_use_of_from_reg(Is, From, To, [I|Acc])
     end;
-is_transparent(_, _) -> false.
+eliminate_use_of_from_reg([I]=Is, From, _To, Acc) ->
+    case beam_utils:is_killed_block(From, [I]) of
+	true ->
+	    {yes,reverse(Acc, Is)};
+	false ->
+	    no
+    end.
 
 %% opt_alloc(Instructions) -> Instructions'
 %%  Optimises all allocate instructions.
 
 opt_alloc([{set,[],[],{alloc,R,{_,Ns,Nh,[]}}}|Is]) ->
-    [{set,[],[],opt_alloc(Is, Ns, Nh, R)}|opt(Is)];
+    [{set,[],[],opt_alloc(Is, Ns, Nh, R)}|Is];
 opt_alloc([I|Is]) -> [I|opt_alloc(Is)];
 opt_alloc([]) -> [].
 	
diff --git a/lib/compiler/src/beam_bool.erl b/lib/compiler/src/beam_bool.erl
index 14b6381230..c9e103eae9 100644
--- a/lib/compiler/src/beam_bool.erl
+++ b/lib/compiler/src/beam_bool.erl
@@ -25,8 +25,6 @@
 
 -import(lists, [reverse/1,reverse/2,foldl/3,mapfoldl/3,map/2]).
 
--define(MAXREG, 1024).
-
 -record(st,
 	{next,					%Next label number.
 	 ll					%Live regs at labels.
diff --git a/lib/compiler/src/beam_clean.erl b/lib/compiler/src/beam_clean.erl
index 919ee3ee7d..7d66985791 100644
--- a/lib/compiler/src/beam_clean.erl
+++ b/lib/compiler/src/beam_clean.erl
@@ -141,7 +141,7 @@ renumber_labels([{bif,is_record,{f,_},
     renumber_labels(Is, Acc, St);
 renumber_labels([{test,is_record,{f,_}=Fail,
 		  [Term,{atom,Tag}=TagAtom,{integer,Arity}]}|Is0], Acc, St) ->
-    Tmp = {x,1023},
+    Tmp = {x,1022},
     Is = case is_record_tuple(Term, Tag, Arity) of
 	     yes ->
 		 Is0;
diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index ead88b57e9..0cb5040177 100644
--- a/lib/compiler/src/beam_dead.erl
+++ b/lib/compiler/src/beam_dead.erl
@@ -242,8 +242,15 @@ backward([{select,select_val,Reg,{f,Fail0},List0}|Is], D, Acc) ->
     List = shortcut_select_list(List0, Reg, D, []),
     Fail1 = shortcut_label(Fail0, D),
     Fail = shortcut_bs_test(Fail1, Is, D),
-    Sel = {select,select_val,Reg,{f,Fail},List},
-    backward(Is, D, [Sel|Acc]);
+    case List of
+	[{atom,B1},F,{atom,B2},F] when B1 =:= not B2 ->
+	    Test = {test,is_boolean,{f,Fail},[Reg]},
+	    Jump = {jump,F},
+	    backward([Jump,Test|Is], D, Acc);
+	[_|_] ->
+	    Sel = {select,select_val,Reg,{f,Fail},List},
+	    backward(Is, D, [Sel|Acc])
+    end;
 backward([{jump,{f,To0}},{move,Src,Reg}=Move|Is], D, Acc) ->
     To = shortcut_select_label(To0, Reg, Src, D),
     Jump = {jump,{f,To}},
@@ -295,7 +302,18 @@ backward([{test,Op,{f,To0},Ops0}|Is], D, Acc) ->
 	    is_eq_exact -> combine_eqs(To, Ops0, D, Acc);
 	    _ -> {test,Op,{f,To},Ops0}
 	end,
-    backward(Is, D, [I|Acc]);
+    case {I,Acc} of
+	{{test,is_atom,Fail,Ops0},[{test,is_boolean,Fail,Ops0}|_]} ->
+	    %% An is_atom test before an is_boolean test (with the
+	    %% same failure label) is redundant.
+	    backward(Is, D, Acc);
+	{{test,_,_,_},_} ->
+	    %% Still a test instruction. Done.
+	    backward(Is, D, [I|Acc]);
+	{_,_} ->
+	    %% Rewritten to a select_val. Rescan.
+	    backward([I|Is], D, Acc)
+    end;
 backward([{test,Op,{f,To0},Live,Ops0,Dst}|Is], D, Acc) ->
     To1 = shortcut_bs_test(To0, Is, D),
     To2 = shortcut_label(To1, D),
diff --git a/lib/compiler/src/beam_jump.erl b/lib/compiler/src/beam_jump.erl
index 5e58e0f6ac..3b6eb19fe8 100644
--- a/lib/compiler/src/beam_jump.erl
+++ b/lib/compiler/src/beam_jump.erl
@@ -495,7 +495,7 @@ is_label_used_in_block({set,_,_,Info}, Lbl) ->
         {alloc,_,{gc_bif,_,{f,F}}} -> F =:= Lbl;
         {alloc,_,{put_map,_,{f,F}}} -> F =:= Lbl;
         {get_map_elements,{f,F}} -> F =:= Lbl;
-        {'catch',{f,F}} -> F =:= Lbl;
+        {try_catch,_,{f,F}} -> F =:= Lbl;
         {alloc,_,_} -> false;
         {put_tuple,_} -> false;
         {get_tuple_element,_} -> false;
diff --git a/lib/compiler/src/beam_peep.erl b/lib/compiler/src/beam_peep.erl
index 17fd2e502a..75be86b83f 100644
--- a/lib/compiler/src/beam_peep.erl
+++ b/lib/compiler/src/beam_peep.erl
@@ -65,18 +65,6 @@ function({function,Name,Arity,CLabel,Is0}) ->
 %%      InEncoding =:= latin1, OutEncoding =:= unicode; 
 %%      InEncoding =:= latin1, OutEncoding =:= utf8 ->
 %%
-%% (2) A select_val/4 instruction that only verifies that
-%%     its argument is either 'true' or 'false' can be
-%%     be replaced with an is_boolean/2 instruction. That is:
-%%
-%%          select_val Reg Fail   [ true Next false Next ]
-%%        Next: ...
-%%         
-%%     can be rewritten to
-%%
-%%          is_boolean Fail Reg
-%%        Next: ...
-%%
 
 peep(Is) ->
     peep(Is, gb_sets:empty(), []).
@@ -95,12 +83,6 @@ peep([{gc_bif,_,_,_,_,Dst}=I|Is], SeenTests0, Acc) ->
     %% Kill all remembered tests that depend on the destination register.
     SeenTests = kill_seen(Dst, SeenTests0),
     peep(Is, SeenTests, [I|Acc]);
-peep([{test,is_boolean,{f,Fail},Ops}|_]=Is, SeenTests,
-     [{test,is_atom,{f,Fail},Ops}|Acc]) ->
-    %% The previous is_atom/2 test (with the same failure label) is redundant.
-    %% (If is_boolean(Src) is true, is_atom(Src) is also true, so it is
-    %% OK to still remember that we have seen is_atom/1.)
-    peep(Is, SeenTests, Acc);
 peep([{test,Op,_,Ops}=I|Is], SeenTests0, Acc) ->
     case beam_utils:is_pure_test(I) of
 	false ->
@@ -121,16 +103,6 @@ peep([{test,Op,_,Ops}=I|Is], SeenTests0, Acc) ->
 		    peep(Is, SeenTests, [I|Acc])
 	    end
     end;
-peep([{select,select_val,Src,Fail,
-       [{atom,false},{f,L},{atom,true},{f,L}]}|
-      [{label,L}|_]=Is], SeenTests, Acc) ->
-    I = {test,is_boolean,Fail,[Src]},
-    peep([I|Is], SeenTests, Acc);
-peep([{select,select_val,Src,Fail,
-       [{atom,true},{f,L},{atom,false},{f,L}]}|
-      [{label,L}|_]=Is], SeenTests, Acc) ->
-    I = {test,is_boolean,Fail,[Src]},
-    peep([I|Is], SeenTests, Acc);
 peep([I|Is], _, Acc) ->
     %% An unknown instruction. Throw away all information we
     %% have collected about test instructions.
diff --git a/lib/compiler/src/beam_reorder.erl b/lib/compiler/src/beam_reorder.erl
new file mode 100644
index 0000000000..70adca6b04
--- /dev/null
+++ b/lib/compiler/src/beam_reorder.erl
@@ -0,0 +1,134 @@
+%%
+%% %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([{Op,_,_}=TryCatch|[I|Is]=Is0], D, Acc)
+  when Op =:= 'catch'; Op =:= 'try' ->
+    %% Don't allow 'try' or 'catch' instructions to split blocks if
+    %% it can be avoided.
+    case is_safe(I) of
+	false ->
+	    reorder_1(Is0, D, [TryCatch|Acc]);
+	true ->
+	    reorder_1([TryCatch|Is], D, [I|Acc])
+    end;
+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).
+
+%% is_safe(Instruction) -> true|false
+%%  Test whether an instruction is safe (cannot cause an exception).
+
+is_safe({kill,_}) -> true;
+is_safe({move,_,_}) -> true;
+is_safe({put,_}) -> true;
+is_safe({put_list,_,_,_}) -> true;
+is_safe({put_tuple,_,_}) -> true;
+is_safe({test_heap,_,_}) -> true;
+is_safe(_) -> false.
diff --git a/lib/compiler/src/beam_split.erl b/lib/compiler/src/beam_split.erl
index 3be9311080..bb1c0e23a9 100644
--- a/lib/compiler/src/beam_split.erl
+++ b/lib/compiler/src/beam_split.erl
@@ -57,8 +57,8 @@ split_block([{set,[D],[S|Puts],{alloc,R,{put_map,Op,{f,Lbl}=Fail}}}|Is],
 split_block([{set,Ds,[S|Ss],{get_map_elements,Fail}}|Is], Bl, Acc) ->
     Gets = beam_utils:join_even(Ss,Ds),
     split_block(Is, [], [{get_map_elements,Fail,S,{list,Gets}}|make_block(Bl, Acc)]);
-split_block([{set,[R],[],{'catch',L}}|Is], Bl, Acc) ->
-    split_block(Is, [], [{'catch',R,L}|make_block(Bl, Acc)]);
+split_block([{set,[R],[],{try_catch,Op,L}}|Is], Bl, Acc) ->
+    split_block(Is, [], [{Op,R,L}|make_block(Bl, Acc)]);
 split_block([{set,[],[],{line,_}=Line}|Is], Bl, Acc) ->
     split_block(Is, [], [Line|make_block(Bl, Acc)]);
 split_block([I|Is], Bl, Acc) ->
diff --git a/lib/compiler/src/beam_type.erl b/lib/compiler/src/beam_type.erl
index 5298589f83..40d67d1670 100644
--- a/lib/compiler/src/beam_type.erl
+++ b/lib/compiler/src/beam_type.erl
@@ -92,7 +92,7 @@ simplify_basic_1([{set,[D],[TupleReg],{get_tuple_element,0}}=I|Is0], Ts0, Acc) -
 	    Ts = update(I, Ts0),
 	    simplify_basic_1(Is0, Ts, [I|Acc])
     end;
-simplify_basic_1([{set,_,_,{'catch',_}}=I|Is], _Ts, Acc) ->
+simplify_basic_1([{set,_,_,{try_catch,_,_}}=I|Is], _Ts, Acc) ->
     simplify_basic_1(Is, tdb_new(), [I|Acc]);
 simplify_basic_1([{test,is_tuple,_,[R]}=I|Is], Ts, Acc) ->
     case tdb_find(R, Ts) of
@@ -199,7 +199,7 @@ simplify_float_1([{set,[D0],[A0,B0],{alloc,_,{gc_bif,Op0,{f,0}}}}=I|Is]=Is0,
 	    Ts = tdb_update([{D0,float}], Ts0),
 	    simplify_float_1(Is, Ts, Rs, Acc)
     end;
-simplify_float_1([{set,_,_,{'catch',_}}=I|Is]=Is0, _Ts, Rs0, Acc0) ->
+simplify_float_1([{set,_,_,{try_catch,_,_}}=I|Is]=Is0, _Ts, Rs0, Acc0) ->
     Acc = flush_all(Rs0, Is0, Acc0),
     simplify_float_1(Is, tdb_new(), Rs0, [I|Acc]);
 simplify_float_1([{set,_,_,{line,_}}=I|Is], Ts, Rs, 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/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index 942d69a756..ab5fedf3bf 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -31,8 +31,6 @@
 
 -import(lists, [reverse/1,foldl/3,foreach/2,dropwhile/2]).
 
--define(MAXREG, 1024).
-
 %%-define(DEBUG, 1).
 -ifdef(DEBUG).
 -define(DBG_FORMAT(F, D), (io:format((F), (D)))).
@@ -970,9 +968,9 @@ get_fls(#vst{current=#st{fls=Fls}}) when is_atom(Fls) -> Fls.
 
 init_fregs() -> 0.
 
-set_freg({fr,Fr}, #vst{current=#st{f=Fregs0}=St}=Vst)
+set_freg({fr,Fr}=Freg, #vst{current=#st{f=Fregs0}=St}=Vst)
   when is_integer(Fr), 0 =< Fr ->
-    limit_check(Fr),
+    check_limit(Freg),
     Bit = 1 bsl Fr,
     if
 	Fregs0 band Bit =:= 0 ->
@@ -985,9 +983,10 @@ set_freg(Fr, _) -> error({bad_target,Fr}).
 assert_freg_set({fr,Fr}=Freg, #vst{current=#st{f=Fregs}})
   when is_integer(Fr), 0 =< Fr ->
     if
-	Fregs band (1 bsl Fr) =/= 0 ->
-	    limit_check(Fr);
-	true -> error({uninitialized_reg,Freg})
+	(Fregs bsr Fr) band 1 =:= 0 ->
+	    error({uninitialized_reg,Freg});
+	true ->
+	    ok
     end;
 assert_freg_set(Fr, _) -> error({bad_source,Fr}).
 
@@ -1066,16 +1065,16 @@ set_type(Type, {x,_}=Reg, Vst) -> set_type_reg(Type, Reg, Vst);
 set_type(Type, {y,_}=Reg, Vst) -> set_type_y(Type, Reg, Vst);
 set_type(_, _, #vst{}=Vst) -> Vst.
 
-set_type_reg(Type, {x,X}, #vst{current=#st{x=Xs}=St}=Vst) 
+set_type_reg(Type, {x,X}=Reg, #vst{current=#st{x=Xs}=St}=Vst)
   when is_integer(X), 0 =< X ->
-    limit_check(X),
+    check_limit(Reg),
     Vst#vst{current=St#st{x=gb_trees:enter(X, Type, Xs)}};
 set_type_reg(Type, Reg, Vst) ->
     set_type_y(Type, Reg, Vst).
 
 set_type_y(Type, {y,Y}=Reg, #vst{current=#st{y=Ys0}=St}=Vst)
   when is_integer(Y), 0 =< Y ->
-    limit_check(Y),
+    check_limit(Reg),
     Ys = case gb_trees:lookup(Y, Ys0) of
 	     none ->
 		 error({invalid_store,Reg,Type});
@@ -1591,9 +1590,15 @@ return_type_math(pow, 2) -> {float,[]};
 return_type_math(pi, 0) -> {float,[]};
 return_type_math(F, A) when is_atom(F), is_integer(A), A >= 0 -> term.
 
-limit_check(Num) when is_integer(Num), Num >= ?MAXREG ->
-    error(limit);
-limit_check(_) -> ok.
+check_limit({x,X}) when is_integer(X), X < 1023 ->
+    %% Note: x(1023) is reserved for use by the BEAM loader.
+    ok;
+check_limit({y,Y}) when is_integer(Y), Y < 1024 ->
+    ok;
+check_limit({fr,Fr}) when is_integer(Fr), Fr < 1024 ->
+    ok;
+check_limit(_) ->
+    error(limit).
 
 min(A, B) when is_integer(A), is_integer(B), A < B -> A;
 min(A, B) when is_integer(A), is_integer(B) -> B.
diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index e0a29fe9b1..605f5b8fd5 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -671,8 +671,11 @@ asm_passes() ->
     %% Assembly level optimisations.
     [{delay,
       [{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"}},
@@ -703,6 +706,7 @@ asm_passes() ->
        {iff,no_postopt,[{pass,beam_clean}]},
 
        {pass,beam_z},
+       {iff,dz,{listing,"z"}},
        {iff,dopt,{listing,"optimize"}},
        {iff,'S',{listing,"S"}},
        {iff,'to_asm',{done,"S"}}]},
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,
diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 0941ad5dd5..7c229210a0 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -469,7 +469,8 @@ unforce_tree([#iset{var=#c_var{name=V},arg=Arg0}|Es], D0) ->
     unforce_tree(Es, D);
 unforce_tree([#icall{}=Call], D) ->
     unforce_tree_subst(Call, D);
-unforce_tree([Top], _) -> Top.
+unforce_tree([#c_var{name=V}], D) ->
+    gb_trees:get(V, D).
 
 unforce_tree_subst(#icall{module=#c_literal{val=erlang},
 			  name=#c_literal{val='=:='},
diff --git a/lib/compiler/test/beam_validator_SUITE.erl b/lib/compiler/test/beam_validator_SUITE.erl
index 69391b15eb..d6deb4a730 100644
--- a/lib/compiler/test/beam_validator_SUITE.erl
+++ b/lib/compiler/test/beam_validator_SUITE.erl
@@ -107,13 +107,13 @@ xrange(Config) when is_list(Config) ->
 	  {{bif,'+',{f,0},[{x,-1},{x,1}],{x,0}},4,
 	   {uninitialized_reg,{x,-1}}}},
 	 {{t,sum_2,2},
-	  {{bif,'+',{f,0},[{x,0},{x,1024}],{x,0}},4,
-	   {uninitialized_reg,{x,1024}}}},
+	  {{bif,'+',{f,0},[{x,0},{x,1023}],{x,0}},4,
+	   {uninitialized_reg,{x,1023}}}},
 	 {{t,sum_3,2},
 	  {{bif,'+',{f,0},[{x,0},{x,1}],{x,-1}},4,
 	   {invalid_store,{x,-1},number}}},
 	 {{t,sum_4,2},
-	  {{bif,'+',{f,0},[{x,0},{x,1}],{x,1024}},4,limit}}] = Errors,
+	  {{bif,'+',{f,0},[{x,0},{x,1}],{x,1023}},4,limit}}] = Errors,
     ok.
 
 yrange(Config) when is_list(Config) ->
diff --git a/lib/compiler/test/beam_validator_SUITE_data/xrange.S b/lib/compiler/test/beam_validator_SUITE_data/xrange.S
index c6f20288f7..a76408dde3 100644
--- a/lib/compiler/test/beam_validator_SUITE_data/xrange.S
+++ b/lib/compiler/test/beam_validator_SUITE_data/xrange.S
@@ -20,7 +20,7 @@
   {label,3}.
     {func_info,{atom,t},{atom,sum_2},2}.
   {label,4}.
-    {bif,'+',{f,0},[{x,0},{x,1024}],{x,0}}.
+    {bif,'+',{f,0},[{x,0},{x,1023}],{x,0}}.
     {'%live',1}.
     return.
 
@@ -38,7 +38,7 @@
   {label,7}.
     {func_info,{atom,t},{atom,sum_4},2}.
   {label,8}.
-    {bif,'+',{f,0},[{x,0},{x,1}],{x,1024}}.
+    {bif,'+',{f,0},[{x,0},{x,1}],{x,1023}}.
     {'%live',1}.
     return.
 
diff --git a/lib/compiler/test/misc_SUITE.erl b/lib/compiler/test/misc_SUITE.erl
index 8606935504..3582e055c8 100644
--- a/lib/compiler/test/misc_SUITE.erl
+++ b/lib/compiler/test/misc_SUITE.erl
@@ -192,6 +192,14 @@ silly_coverage(Config) when is_list(Config) ->
 		     {label,2}|non_proper_list]}],99},
     expect_error(fun() -> beam_a:module(BeamAInput, []) end),
 
+    %% beam_reorder
+    BlockInput = {?MODULE,[{foo,0}],[],
+		  [{function,foo,0,2,
+		    [{label,1},
+		     {func_info,{atom,?MODULE},{atom,foo},0},
+		     {label,2}|non_proper_list]}],99},
+    expect_error(fun() -> beam_reorder:module(BlockInput, []) end),
+
     %% beam_block
     BlockInput = {?MODULE,[{foo,0}],[],
 		  [{function,foo,0,2,