Introduce a put_tuple2 instruction

Sometimes when building a tuple, there is no way to avoid an
extra `move` instruction. Consider this code:

    make_tuple(A) -> {ok,A}.

The corresponding BEAM code looks like this:

    {test_heap,3,1}.
    {put_tuple,2,{x,1}}.
    {put,{atom,ok}}.
    {put,{x,0}}.
    {move,{x,1},{x,0}}.
    return.

To avoid overwriting the source register `{x,0}`, a `move`
instruction is necessary.

The problem doesn't exist when building a list:

    %% build_list(A) -> [A].
    {test_heap,2,1}.
    {put_list,{x,0},nil,{x,0}}.
    return.

Introduce a new `put_tuple2` instruction that builds a tuple in a
single instruction, so that the `move` instruction can be eliminated:

    %% make_tuple(A) -> {ok,A}.
    {test_heap,3,1}.
    {put_tuple2,{x,0},{list,[{atom,ok},{x,0}]}}.
    return.

Note that the BEAM loader already combines `put_tuple` and `put`
instructions into an internal instruction similar to `put_tuple2`.
Therefore the introduction of the new instruction will not speed up
execution of tuple building itself, but it will be less work for
the loader to load the new instruction.

10 files changed, 61 insertions, 26 deletions

diff --git a/lib/compiler/src/beam_block.erl b/lib/compiler/src/beam_block.erl
index c928fc7187..0ed2a03a81 100644
--- a/lib/compiler/src/beam_block.erl
+++ b/lib/compiler/src/beam_block.erl
@@ -89,6 +89,7 @@ collect({move,S,D})          -> {set,[D],[S],move};
 collect({put_list,S1,S2,D})  -> {set,[D],[S1,S2],put_list};
 collect({put_tuple,A,D})     -> {set,[D],[],{put_tuple,A}};
 collect({put,S})             -> {set,[],[S],put};
+collect({put_tuple2,D,{list,Els}}) -> {set,[D],Els,put_tuple2};
 collect({get_tuple_element,S,I,D}) -> {set,[D],[S],{get_tuple_element,I}};
 collect({set_tuple_element,S,D,I}) -> {set,[],[S,D],{set_tuple_element,I}};
 collect({get_hd,S,D})  ->       {set,[D],[S],get_hd};
diff --git a/lib/compiler/src/beam_disasm.erl b/lib/compiler/src/beam_disasm.erl
index 6cee9acae4..d0be39f520 100644
--- a/lib/compiler/src/beam_disasm.erl
+++ b/lib/compiler/src/beam_disasm.erl
@@ -373,6 +373,8 @@ disasm_instr(B, Bs, Atoms, Literals) ->
 	    disasm_map_inst(get_map_elements, Arity, Bs, Atoms, Literals);
 	has_map_fields ->
 	    disasm_map_inst(has_map_fields, Arity, Bs, Atoms, Literals);
+	put_tuple2 ->
+	    disasm_put_tuple2(Bs, Atoms, Literals);
 	_ ->
 	    try decode_n_args(Arity, Bs, Atoms, Literals) of
 		{Args, RestBs} ->
@@ -413,6 +415,14 @@ disasm_map_inst(Inst, Arity, Bs0, Atoms, Literals) ->
     {List, RestBs} = decode_n_args(Len, Bs2, Atoms, Literals),
     {{Inst, Args ++ [{Z,U,List}]}, RestBs}.
 
+disasm_put_tuple2(Bs, Atoms, Literals) ->
+    {X, Bs1} = decode_arg(Bs, Atoms, Literals),
+    {Z, Bs2} = decode_arg(Bs1, Atoms, Literals),
+    {U, Bs3} = decode_arg(Bs2, Atoms, Literals),
+    {u, Len} = U,
+    {List, RestBs} = decode_n_args(Len, Bs3, Atoms, Literals),
+    {{put_tuple2, [X,{Z,U,List}]}, RestBs}.
+
 %%-----------------------------------------------------------------------
 %% decode_arg([Byte]) -> {Arg, [Byte]}
 %%
@@ -1096,6 +1106,13 @@ resolve_inst({get_tl,[Src,Dst]},_,_,_) ->
     {get_tl,Src,Dst};
 
 %%
+%% OTP 22.
+%%
+resolve_inst({put_tuple2,[Dst,{{z,1},{u,_},List0}]},_,_,_) ->
+    List = resolve_args(List0),
+    {put_tuple2,Dst,{list,List}};
+
+%%
 %% Catches instructions that are not yet handled.
 %%
 resolve_inst(X,_,_,_) -> ?exit({resolve_inst,X}).
diff --git a/lib/compiler/src/beam_except.erl b/lib/compiler/src/beam_except.erl
index 366ec6cd44..98831d87a7 100644
--- a/lib/compiler/src/beam_except.erl
+++ b/lib/compiler/src/beam_except.erl
@@ -113,14 +113,7 @@ dig_out_block([{set,[{x,0}],[{atom,if_clause}],move}]) ->
     {yes,if_end,[]};
 dig_out_block([{set,[{x,0}],[{literal,{Exc,Value}}],move}|Is]) ->
     translate_exception(Exc, {literal,Value}, Is, 0);
-dig_out_block([{set,[{x,0}],[Tuple],move},
-	       {set,[],[Value],put},
-	       {set,[],[{atom,Exc}],put},
-	       {set,[Tuple],[],{put_tuple,2}}|Is]) ->
-    translate_exception(Exc, Value, Is, 3);
-dig_out_block([{set,[],[Value],put},
-	       {set,[],[{atom,Exc}],put},
-	       {set,[{x,0}],[],{put_tuple,2}}|Is]) ->
+dig_out_block([{set,[{x,0}],[{atom,Exc},Value],put_tuple2}|Is]) ->
     translate_exception(Exc, Value, Is, 3);
 dig_out_block(_) -> no.
 
diff --git a/lib/compiler/src/beam_flatten.erl b/lib/compiler/src/beam_flatten.erl
index 9a1c5a1021..973d16a1bc 100644
--- a/lib/compiler/src/beam_flatten.erl
+++ b/lib/compiler/src/beam_flatten.erl
@@ -65,6 +65,7 @@ norm({set,[D],[S],move})          -> {move,S,D};
 norm({set,[D],[S],fmove})         -> {fmove,S,D};
 norm({set,[D],[S],fconv})         -> {fconv,S,D};
 norm({set,[D],[S1,S2],put_list})  -> {put_list,S1,S2,D};
+norm({set,[D],Els,put_tuple2})    -> {put_tuple2,D,{list,Els}};
 norm({set,[D],[],{put_tuple,A}})  -> {put_tuple,A,D};
 norm({set,[],[S],put})            -> {put,S};
 norm({set,[D],[S],{get_tuple_element,I}}) -> {get_tuple_element,S,I,D};
diff --git a/lib/compiler/src/beam_ssa_codegen.erl b/lib/compiler/src/beam_ssa_codegen.erl
index 357352269c..006c41c0e0 100644
--- a/lib/compiler/src/beam_ssa_codegen.erl
+++ b/lib/compiler/src/beam_ssa_codegen.erl
@@ -286,6 +286,8 @@ classify_heap_need(put_list, _) ->
     {put,2};
 classify_heap_need(put_tuple_arity, [#b_literal{val=Words}]) ->
     {put,Words+1};
+classify_heap_need(put_tuple, Elements) ->
+    {put,length(Elements)+1};
 classify_heap_need({bif,Name}, Args) ->
     case is_gc_bif(Name, Args) of
         false -> neutral;
@@ -1360,6 +1362,8 @@ cg_instr(get_tuple_element=Op, [Src,{integer,N}], Dst) ->
     [{Op,Src,N,Dst}];
 cg_instr(put_list=Op, [Hd,Tl], Dst) ->
     [{Op,Hd,Tl,Dst}];
+cg_instr(put_tuple, Elements, Dst) ->
+    [{put_tuple2,Dst,{list,Elements}}];
 cg_instr(put_tuple_arity, [{integer,Arity}], Dst) ->
     [{put_tuple,Arity,Dst}];
 cg_instr(put_tuple_elements, Elements, _Dst) ->
diff --git a/lib/compiler/src/beam_ssa_pre_codegen.erl b/lib/compiler/src/beam_ssa_pre_codegen.erl
index bbc3739eb5..54aa2efaf6 100644
--- a/lib/compiler/src/beam_ssa_pre_codegen.erl
+++ b/lib/compiler/src/beam_ssa_pre_codegen.erl
@@ -79,8 +79,9 @@
                     {'ok',beam_ssa:b_module()}.
 
 module(#b_module{body=Fs0}=Module, Opts) ->
+    FixTuples = proplists:get_bool(no_put_tuple2, Opts),
     ExtraAnnos = proplists:get_bool(dprecg, Opts),
-    Ps = passes(ExtraAnnos),
+    Ps = passes(FixTuples, ExtraAnnos),
     Fs = functions(Fs0, Ps),
     {ok,Module#b_module{body=Fs}}.
 
@@ -113,13 +114,16 @@ functions([], _Ps) -> [].
             }).
 -define(PASS(N), {N,fun N/1}).
 
-passes(ExtraAnnos) ->
+passes(FixTuples, ExtraAnnos) ->
     Ps = [?PASS(assert_no_critical_edges),
 
           %% Preliminaries.
           ?PASS(fix_bs),
           ?PASS(sanitize),
-          ?PASS(fix_tuples),
+          case FixTuples of
+              false -> ignore;
+              true -> ?PASS(fix_tuples)
+          end,
           ?PASS(place_frames),
           ?PASS(fix_receives),
 
@@ -151,10 +155,7 @@ passes(ExtraAnnos) ->
           ?PASS(fix_aliased_regs),
           ?PASS(frame_size),
           ?PASS(turn_yregs)],
-    case ExtraAnnos of
-        false -> [P || P <- Ps, P =/= ignore];
-        true -> Ps
-    end.
+    [P || P <- Ps, P =/= ignore].
 
 function(#b_function{anno=Anno,args=Args,bs=Blocks0,cnt=Count0}=F0, Ps) ->
     try
@@ -693,9 +694,11 @@ prune_phi(#b_set{args=Args0}=Phi, Reachable) ->
 %%%
 
 %% fix_tuples(St0) -> St.
-%%  We must split tuple creation into two instruction to mirror the
-%%  the way tuples are created in BEAM.  Each put_tuple instruction is
-%%  split into put_tuple_arity followed by put_tuple_elements.
+%%  If compatibility with a previous version of Erlang has been
+%%  requested, tuple creation must be split into two instruction to
+%%  mirror the the way tuples are created in BEAM prior to OTP 22.
+%%  Each put_tuple instruction is split into put_tuple_arity followed
+%%  by put_tuple_elements.
 
 fix_tuples(#st{ssa=Blocks0,cnt=Count0}=St) ->
     F = fun (#b_set{op=put_tuple,args=Args}=Put, C0) ->
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index b44771d8a9..953aced66e 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -349,6 +349,12 @@ valfun_1({put_list,A,B,Dst}, Vst0) ->
     assert_term(B, Vst0),
     Vst = eat_heap(2, Vst0),
     set_type_reg(cons, Dst, Vst);
+valfun_1({put_tuple2,Dst,{list,Elements}}, Vst0) ->
+    _ = [assert_term(El, Vst0) || El <- Elements],
+    Size = length(Elements),
+    Vst = eat_heap(Size+1, Vst0),
+    Type = {tuple,Size},
+    set_type_reg(Type, Dst, Vst);
 valfun_1({put_tuple,Sz,Dst}, Vst0) when is_integer(Sz) ->
     Vst1 = eat_heap(1, Vst0),
     Vst = set_type_reg(tuple_in_progress, Dst, Vst1),
diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index 3a835cfb2f..0a7f723c64 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -259,13 +259,13 @@ expand_opt(r19, Os) ->
 expand_opt(r20, Os) ->
     expand_opt_before_21(Os);
 expand_opt(r21, Os) ->
-    Os;
+    [no_put_tuple2|Os];
 expand_opt({debug_info_key,_}=O, Os) ->
     [encrypt_debug_info,O|Os];
 expand_opt(O, Os) -> [O|Os].
 
 expand_opt_before_21(Os) ->
-    [no_get_hd_tl,no_ssa_opt_record,no_utf8_atoms|Os].
+    [no_put_tuple2,no_get_hd_tl,no_ssa_opt_record,no_utf8_atoms|Os].
 
 %% format_error(ErrorDescriptor) -> string()
 
diff --git a/lib/compiler/src/genop.tab b/lib/compiler/src/genop.tab
index f35ae09fe7..8e34e3e291 100755
--- a/lib/compiler/src/genop.tab
+++ b/lib/compiler/src/genop.tab
@@ -573,3 +573,8 @@ BEAM_FORMAT_NUMBER=0
 ## @doc  Get the tail (or cdr) part of a list (a cons cell) from Source and
 ##       put it into the register Tail.
 163: get_tl/2
+
+## @spec put_tuple2  Destination Elements
+## @doc  Build a tuple with the elements in the list Elements and put it
+##       put into register Destination.
+164: put_tuple2/2
diff --git a/lib/compiler/test/compile_SUITE.erl b/lib/compiler/test/compile_SUITE.erl
index 85f0b7dc46..8d8fc23027 100644
--- a/lib/compiler/test/compile_SUITE.erl
+++ b/lib/compiler/test/compile_SUITE.erl
@@ -1476,18 +1476,22 @@ bc_options(Config) ->
     101 = highest_opcode(DataDir, small_float, [no_get_hd_tl,no_line_info]),
 
     103 = highest_opcode(DataDir, big,
-                         [no_get_hd_tl,no_ssa_opt_record,
+                         [no_put_tuple2,
+                          no_get_hd_tl,no_ssa_opt_record,
                           no_line_info,no_stack_trimming]),
 
     125 = highest_opcode(DataDir, small_float,
                          [no_get_hd_tl,no_line_info,no_ssa_opt_float]),
 
     132 = highest_opcode(DataDir, small,
-                         [no_get_hd_tl,no_ssa_opt_record,no_ssa_opt_float,no_line_info]),
+                         [no_put_tuple2,no_get_hd_tl,no_ssa_opt_record,
+                          no_ssa_opt_float,no_line_info]),
 
-    136 = highest_opcode(DataDir, big, [no_get_hd_tl,no_ssa_opt_record,no_line_info]),
+    136 = highest_opcode(DataDir, big, [no_put_tuple2,no_get_hd_tl,
+                                        no_ssa_opt_record,no_line_info]),
 
-    153 = highest_opcode(DataDir, big, [no_get_hd_tl,no_ssa_opt_record]),
+    153 = highest_opcode(DataDir, big, [no_put_tuple2,no_get_hd_tl,
+                                        no_ssa_opt_record]),
     153 = highest_opcode(DataDir, big, [r16]),
     153 = highest_opcode(DataDir, big, [r17]),
     153 = highest_opcode(DataDir, big, [r18]),
@@ -1499,9 +1503,10 @@ bc_options(Config) ->
     158 = highest_opcode(DataDir, small_maps, [r18]),
     158 = highest_opcode(DataDir, small_maps, [r19]),
     158 = highest_opcode(DataDir, small_maps, [r20]),
-    158 = highest_opcode(DataDir, small_maps, []),
+    158 = highest_opcode(DataDir, small_maps, [r21]),
 
-    163 = highest_opcode(DataDir, big, []),
+    164 = highest_opcode(DataDir, small_maps, []),
+    164 = highest_opcode(DataDir, big, []),
 
     ok.