Teach the compiler the 'no_dead' option

To facilitate debugging of compiler bugs, teach the compiler the
'no_dead' option. Since the beam_dead pass used to do the necessary
splitting of basic blocks to expose all labels, we must move that
splitting into a separate pass that is always run.

5 files changed, 93 insertions, 63 deletions

diff --git a/lib/compiler/src/Makefile b/lib/compiler/src/Makefile
index 1238d113e1..7a237608ad 100644
--- a/lib/compiler/src/Makefile
+++ b/lib/compiler/src/Makefile
@@ -59,6 +59,7 @@ MODULES =  \
 	beam_opcodes \
 	beam_peep \
 	beam_receive \
+	beam_split \
 	beam_trim \
 	beam_type \
 	beam_utils \
diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index 9f81a6ab43..5f12a98f09 100644
--- a/lib/compiler/src/beam_dead.erl
+++ b/lib/compiler/src/beam_dead.erl
@@ -131,10 +131,9 @@
 -import(lists, [mapfoldl/3,reverse/1]).
 
 module({Mod,Exp,Attr,Fs0,_}, _Opts) ->
-    Fs1 = [split_blocks(F) || F <- Fs0],
-    {Fs2,Lc1} = beam_clean:clean_labels(Fs1),
-    {Fs,Lc} = mapfoldl(fun function/2, Lc1, Fs2),
-    %%{Fs,Lc} = {Fs2,Lc1},
+    {Fs1,Lc1} = beam_clean:clean_labels(Fs0),
+    {Fs,Lc} = mapfoldl(fun function/2, Lc1, Fs1),
+    %%{Fs,Lc} = {Fs1,Lc1},
     {ok,{Mod,Exp,Attr,Fs,Lc}}.
 
 function({function,Name,Arity,CLabel,Is0}, Lc0) ->
@@ -160,64 +159,6 @@ function({function,Name,Arity,CLabel,Is0}, Lc0) ->
 	    erlang:raise(Class, Error, Stack)
     end.
 
-%% We must split the basic block when we encounter instructions with labels,
-%% such as catches and BIFs. All labels must be visible outside the blocks.
-
-split_blocks({function,Name,Arity,CLabel,Is0}) ->
-    Is = split_blocks(Is0, []),
-    {function,Name,Arity,CLabel,Is}.
-
-split_blocks([{block,Bl}|Is], Acc0) ->
-    Acc = split_block(Bl, [], Acc0),
-    split_blocks(Is, Acc);
-split_blocks([I|Is], Acc) ->
-    split_blocks(Is, [I|Acc]);
-split_blocks([], Acc) -> reverse(Acc).
-
-split_block([{set,[R],[_,_,_]=As,{bif,is_record,{f,Lbl}}}|Is], Bl, Acc) ->
-    %% is_record/3 must be translated by beam_clean; therefore,
-    %% it must be outside of any block.
-    split_block(Is, [], [{bif,is_record,{f,Lbl},As,R}|make_block(Bl, Acc)]);
-split_block([{set,[R],As,{bif,N,{f,Lbl}=Fail}}|Is], Bl, Acc) when Lbl =/= 0 ->
-    split_block(Is, [], [{bif,N,Fail,As,R}|make_block(Bl, Acc)]);
-split_block([{set,[R],As,{alloc,Live,{gc_bif,N,{f,Lbl}=Fail}}}|Is], Bl, Acc)
-  when Lbl =/= 0 ->
-    split_block(Is, [], [{gc_bif,N,Fail,Live,As,R}|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,[],[],{line,_}=Line}|Is], Bl, Acc) ->
-    split_block(Is, [], [Line|make_block(Bl, Acc)]);
-split_block([I|Is], Bl, Acc) ->
-    split_block(Is, [I|Bl], Acc);
-split_block([], Bl, Acc) -> make_block(Bl, Acc).
-
-make_block([], Acc) -> Acc;
-make_block([{set,[D],Ss,{bif,Op,Fail}}|Bl]=Bl0, Acc) ->
-    %% If the last instruction in the block is a comparison or boolean operator
-    %% (such as '=:='), move it out of the block to facilitate further
-    %% optimizations.
-    Arity = length(Ss),
-    case erl_internal:comp_op(Op, Arity) orelse
-	erl_internal:new_type_test(Op, Arity) orelse
-	erl_internal:bool_op(Op, Arity) of
-	false ->
-	    [{block,reverse(Bl0)}|Acc];
-	true ->
-	    I = {bif,Op,Fail,Ss,D},
-	    case Bl =:= [] of
-		true -> [I|Acc];
-		false -> [I,{block,reverse(Bl)}|Acc]
-	    end
-    end;
-make_block([{set,[Dst],[Src],move}|Bl], Acc) ->
-    %% Make optimization of {move,Src,Dst}, {jump,...} possible.
-    I = {move,Src,Dst},
-    case Bl =:= [] of
-	true -> [I|Acc];
-	false -> [I,{block,reverse(Bl)}|Acc]
-    end;
-make_block(Bl, Acc) -> [{block,reverse(Bl)}|Acc].
-
 %% 'move' instructions outside of blocks may thwart the jump optimizer.
 %% Move them back into the block.
 
diff --git a/lib/compiler/src/beam_split.erl b/lib/compiler/src/beam_split.erl
new file mode 100644
index 0000000000..cacaaebffe
--- /dev/null
+++ b/lib/compiler/src/beam_split.erl
@@ -0,0 +1,85 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2011. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+-module(beam_split).
+-export([module/2]).
+
+-import(lists, [reverse/1]).
+
+module({Mod,Exp,Attr,Fs0,Lc}, _Opts) ->
+    Fs = [split_blocks(F) || F <- Fs0],
+    {ok,{Mod,Exp,Attr,Fs,Lc}}.
+
+%% We must split the basic block when we encounter instructions with labels,
+%% such as catches and BIFs. All labels must be visible outside the blocks.
+
+split_blocks({function,Name,Arity,CLabel,Is0}) ->
+    Is = split_blocks(Is0, []),
+    {function,Name,Arity,CLabel,Is}.
+
+split_blocks([{block,Bl}|Is], Acc0) ->
+    Acc = split_block(Bl, [], Acc0),
+    split_blocks(Is, Acc);
+split_blocks([I|Is], Acc) ->
+    split_blocks(Is, [I|Acc]);
+split_blocks([], Acc) -> reverse(Acc).
+
+split_block([{set,[R],[_,_,_]=As,{bif,is_record,{f,Lbl}}}|Is], Bl, Acc) ->
+    %% is_record/3 must be translated by beam_clean; therefore,
+    %% it must be outside of any block.
+    split_block(Is, [], [{bif,is_record,{f,Lbl},As,R}|make_block(Bl, Acc)]);
+split_block([{set,[R],As,{bif,N,{f,Lbl}=Fail}}|Is], Bl, Acc) when Lbl =/= 0 ->
+    split_block(Is, [], [{bif,N,Fail,As,R}|make_block(Bl, Acc)]);
+split_block([{set,[R],As,{alloc,Live,{gc_bif,N,{f,Lbl}=Fail}}}|Is], Bl, Acc)
+  when Lbl =/= 0 ->
+    split_block(Is, [], [{gc_bif,N,Fail,Live,As,R}|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,[],[],{line,_}=Line}|Is], Bl, Acc) ->
+    split_block(Is, [], [Line|make_block(Bl, Acc)]);
+split_block([I|Is], Bl, Acc) ->
+    split_block(Is, [I|Bl], Acc);
+split_block([], Bl, Acc) -> make_block(Bl, Acc).
+
+make_block([], Acc) -> Acc;
+make_block([{set,[D],Ss,{bif,Op,Fail}}|Bl]=Bl0, Acc) ->
+    %% If the last instruction in the block is a comparison or boolean operator
+    %% (such as '=:='), move it out of the block to facilitate further
+    %% optimizations.
+    Arity = length(Ss),
+    case erl_internal:comp_op(Op, Arity) orelse
+	erl_internal:new_type_test(Op, Arity) orelse
+	erl_internal:bool_op(Op, Arity) of
+	false ->
+	    [{block,reverse(Bl0)}|Acc];
+	true ->
+	    I = {bif,Op,Fail,Ss,D},
+	    case Bl =:= [] of
+		true -> [I|Acc];
+		false -> [I,{block,reverse(Bl)}|Acc]
+	    end
+    end;
+make_block([{set,[Dst],[Src],move}|Bl], Acc) ->
+    %% Make optimization of {move,Src,Dst}, {jump,...} possible.
+    I = {move,Src,Dst},
+    case Bl =:= [] of
+	true -> [I|Acc];
+	false -> [I,{block,reverse(Bl)}|Acc]
+    end;
+make_block(Bl, Acc) -> [{block,reverse(Bl)}|Acc].
diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index 8815cfb26f..a17a10046e 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -633,7 +633,9 @@ asm_passes() ->
 	 {iff,dbool,{listing,"bool"}},
 	 {unless,no_topt,{pass,beam_type}},
 	 {iff,dtype,{listing,"type"}},
-	 {pass,beam_dead},	      %Must always run since it splits blocks.
+	 {pass,beam_split},
+	 {iff,dsplit,{listing,"split"}},
+	 {unless,no_dead,{pass,beam_dead}},
 	 {iff,ddead,{listing,"dead"}},
 	 {unless,no_jopt,{pass,beam_jump}},
 	 {iff,djmp,{listing,"jump"}},
diff --git a/lib/compiler/src/compiler.app.src b/lib/compiler/src/compiler.app.src
index 4ac879c9a4..efa25fe039 100644
--- a/lib/compiler/src/compiler.app.src
+++ b/lib/compiler/src/compiler.app.src
@@ -34,6 +34,7 @@
 	     beam_opcodes,
 	     beam_peep,
 	     beam_receive,
+	     beam_split,
 	     beam_trim,
 	     beam_type,
 	     beam_utils,