Fix unsafe bit syntax matching optimization

As part of sys_core_fold, variables involved in bit syntax
matching would be annotated when it would be safe for a later
pass to do the delayed sub-binary creation optimization.

An implicit assumption regarding the annotation was that the
code must not be further optimized. That assumption was broken
in 05130e48555891, which introduced a fixpoint iteration
(applying the optimizations until there were no more changes).
That means that a variable could be annotated as safe for
reusing the match context in one iteration, but a later iteration
could rewrite the code in a way that would make the optimization
unsafe.

One way to fix this would be to clear all reuse_for_context
annotations before each iteration. But that would be wasteful.

Instead I chose to fix the problem by moving out the annotation
code to a separate pass (sys_core_bsm) that is run later after
all major optimizations of Core Erlang has been done.

9 files changed, 389 insertions, 297 deletions

diff --git a/lib/compiler/src/Makefile b/lib/compiler/src/Makefile
index 59b80ade5d..f06b8b9ec3 100644
--- a/lib/compiler/src/Makefile
+++ b/lib/compiler/src/Makefile
@@ -83,6 +83,7 @@ MODULES =  \
 	core_scan \
 	erl_bifs \
 	rec_env \
+	sys_core_bsm \
 	sys_core_dsetel \
 	sys_core_fold \
 	sys_core_fold_lists \
diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index c6e61d543e..d05b8a9530 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -718,8 +718,10 @@ core_passes() ->
      | kernel_passes()].
 
 kernel_passes() ->
-    %% Destructive setelement/3 optimization and core lint.
-    [{pass,sys_core_dsetel},
+    %% Optimizations that must be done after all other optimizations.
+    [{pass,sys_core_bsm},
+     {iff,dcbsm,{listing,"core_bsm"}},
+     {pass,sys_core_dsetel},
      {iff,dsetel,{listing,"dsetel"}},
 
      {iff,clint,?pass(core_lint_module)},
@@ -1919,6 +1921,7 @@ pre_load() ->
 	 erl_lint,
 	 erl_parse,
 	 erl_scan,
+	 sys_core_bsm,
 	 sys_core_dsetel,
 	 sys_core_fold,
 	 v3_codegen,
diff --git a/lib/compiler/src/compiler.app.src b/lib/compiler/src/compiler.app.src
index 3961b2af86..d4b4d4da04 100644
--- a/lib/compiler/src/compiler.app.src
+++ b/lib/compiler/src/compiler.app.src
@@ -58,6 +58,7 @@
 	     core_lib,
 	     erl_bifs,
 	     rec_env,
+	     sys_core_bsm,
 	     sys_core_dsetel,
 	     sys_core_fold,
 	     sys_core_fold_lists,
diff --git a/lib/compiler/src/sys_core_bsm.erl b/lib/compiler/src/sys_core_bsm.erl
new file mode 100644
index 0000000000..3e04cc33df
--- /dev/null
+++ b/lib/compiler/src/sys_core_bsm.erl
@@ -0,0 +1,355 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2017. 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%
+%%
+%% Purpose : Optimize bit syntax matching.
+
+
+-module(sys_core_bsm).
+-export([module/2,format_error/1]).
+
+-include("core_parse.hrl").
+-import(lists, [member/2,nth/2,reverse/1,usort/1]).
+
+-spec module(cerl:c_module(), [compile:option()]) -> {'ok', cerl:c_module()}.
+
+module(#c_module{defs=Ds0}=Mod, Opts) ->
+    {Ds,Ws0} = function(Ds0, [], []),
+    case member(bin_opt_info, Opts) of
+        false ->
+            {ok,Mod#c_module{defs=Ds}};
+        true ->
+            Ws1 = [make_warning(Where, What) || {Where,What} <- Ws0],
+            Ws = usort(Ws1),
+            {ok,Mod#c_module{defs=Ds},Ws}
+    end.
+
+function([{#c_var{name={F,Arity}}=Name,B0}|Fs], FsAcc, Ws0) ->
+    try cerl_trees:mapfold(fun bsm_an/2, Ws0, B0) of
+        {B,Ws} ->
+            function(Fs, [{Name,B}|FsAcc], Ws)
+    catch
+	Class:Error ->
+	    Stack = erlang:get_stacktrace(),
+	    io:fwrite("Function: ~w/~w\n", [F,Arity]),
+	    erlang:raise(Class, Error, Stack)
+    end;
+function([], Fs, Ws) ->
+    {reverse(Fs),Ws}.
+
+-type error() :: atom().
+-spec format_error(error()) -> nonempty_string().
+
+format_error(bin_opt_alias) ->
+    "INFO: the '=' operator will prevent delayed sub binary optimization";
+format_error(bin_partition) ->
+    "INFO: matching non-variables after a previous clause matching a variable "
+	"will prevent delayed sub binary optimization";
+format_error(bin_left_var_used_in_guard) ->
+    "INFO: a variable to the left of the binary pattern is used in a guard; "
+	"will prevent delayed sub binary optimization";
+format_error(bin_argument_order) ->
+    "INFO: matching anything else but a plain variable to the left of "
+	"binary pattern will prevent delayed sub binary optimization; "
+	"SUGGEST changing argument order";
+format_error(bin_var_used) ->
+    "INFO: using a matched out sub binary will prevent "
+	"delayed sub binary optimization";
+format_error(orig_bin_var_used_in_guard) ->
+    "INFO: using the original binary variable in a guard will prevent "
+	"delayed sub binary optimization";
+format_error(bin_var_used_in_guard) ->
+    "INFO: using a matched out sub binary in a guard will prevent "
+	"delayed sub binary optimization".
+
+
+%%%
+%%% Annotate bit syntax matching to faciliate optimization in further passes.
+%%%
+
+bsm_an(Core0, Ws0) ->
+    case bsm_an(Core0) of
+        {ok,Core} ->
+            {Core,Ws0};
+        {ok,Core,W} ->
+            {Core,[W|Ws0]}
+    end.
+
+bsm_an(#c_case{arg=#c_var{}=V}=Case) ->
+    bsm_an_1([V], Case);
+bsm_an(#c_case{arg=#c_values{es=Es}}=Case) ->
+    bsm_an_1(Es, Case);
+bsm_an(Other) ->
+    {ok,Other}.
+
+bsm_an_1(Vs, #c_case{clauses=Cs}=Case) ->
+    case bsm_leftmost(Cs) of
+	none -> {ok,Case};
+	Pos -> bsm_an_2(Vs, Cs, Case, Pos)
+    end.
+
+bsm_an_2(Vs, Cs, Case, Pos) ->
+    case bsm_nonempty(Cs, Pos) of
+	true -> bsm_an_3(Vs, Cs, Case, Pos);
+	false -> {ok,Case}
+    end.
+
+bsm_an_3(Vs, Cs, Case, Pos) ->
+    try
+	bsm_ensure_no_partition(Cs, Pos),
+	{ok,bsm_do_an(Vs, Pos, Cs, Case)}
+    catch
+	throw:{problem,Where,What} ->
+	    {ok,Case,{Where,What}}
+    end.
+
+bsm_do_an(Vs0, Pos, Cs0, Case) ->
+    case nth(Pos, Vs0) of
+	#c_var{name=Vname}=V0 ->
+	    Cs = bsm_do_an_var(Vname, Pos, Cs0, []),
+	    V = bsm_annotate_for_reuse(V0),
+	    Bef = lists:sublist(Vs0, Pos-1),
+	    Aft = lists:nthtail(Pos, Vs0),
+	    case Bef ++ [V|Aft] of
+		[_] ->
+		    Case#c_case{arg=V,clauses=Cs};
+		Vs ->
+		    Case#c_case{arg=#c_values{es=Vs},clauses=Cs}
+	    end;
+	_ ->
+	    Case
+    end.
+
+bsm_do_an_var(V, S, [#c_clause{pats=Ps,guard=G,body=B0}=C0|Cs], Acc) ->
+    case nth(S, Ps) of
+	#c_var{name=VarName} ->
+	    case core_lib:is_var_used(V, G) of
+		true -> bsm_problem(C0, orig_bin_var_used_in_guard);
+		false -> ok
+	    end,
+	    case core_lib:is_var_used(VarName, G) of
+		true -> bsm_problem(C0, bin_var_used_in_guard);
+		false -> ok
+	    end,
+	    B1 = bsm_maybe_ctx_to_binary(VarName, B0),
+	    B = bsm_maybe_ctx_to_binary(V, B1),
+	    C = C0#c_clause{body=B},
+	    bsm_do_an_var(V, S, Cs, [C|Acc]);
+	#c_alias{}=P ->
+	    case bsm_could_match_binary(P) of
+		false ->
+		    bsm_do_an_var(V, S, Cs, [C0|Acc]);
+		true ->
+		    bsm_problem(C0, bin_opt_alias)
+	    end;
+	P ->
+	    case bsm_could_match_binary(P) andalso bsm_is_var_used(V, G, B0) of
+		false ->
+		    bsm_do_an_var(V, S, Cs, [C0|Acc]);
+		true ->
+		    bsm_problem(C0, bin_var_used)
+	    end
+    end;
+bsm_do_an_var(_, _, [], Acc) -> reverse(Acc).
+
+bsm_annotate_for_reuse(#c_var{anno=Anno}=Var) ->
+    Var#c_var{anno=[reuse_for_context|Anno]}.
+
+bsm_is_var_used(V, G, B) ->
+    core_lib:is_var_used(V, G) orelse core_lib:is_var_used(V, B).
+
+bsm_maybe_ctx_to_binary(V, B) ->
+    case core_lib:is_var_used(V, B) andalso not previous_ctx_to_binary(V, B) of
+	false ->
+	    B;
+	true ->
+	    #c_seq{arg=#c_primop{name=#c_literal{val=bs_context_to_binary},
+				 args=[#c_var{name=V}]},
+		   body=B}
+    end.
+
+previous_ctx_to_binary(V, Core) ->
+    case Core of
+	#c_seq{arg=#c_primop{name=#c_literal{val=bs_context_to_binary},
+			     args=[#c_var{name=V}]}} ->
+	    true;
+	_ ->
+	    false
+    end.
+
+%% bsm_leftmost(Cs) -> none | ArgumentNumber
+%%  Find the leftmost argument that does binary matching. Return
+%%  the number of the argument (1-N).
+
+bsm_leftmost(Cs) ->
+    bsm_leftmost_1(Cs, none).
+
+bsm_leftmost_1([#c_clause{pats=Ps}|Cs], Pos) ->
+    bsm_leftmost_2(Ps, Cs, 1, Pos);
+bsm_leftmost_1([], Pos) -> Pos.
+
+bsm_leftmost_2(_, Cs, Pos, Pos) ->
+    bsm_leftmost_1(Cs, Pos);
+bsm_leftmost_2([#c_binary{}|_], Cs, N, _) ->
+    bsm_leftmost_1(Cs, N);
+bsm_leftmost_2([_|Ps], Cs, N, Pos) ->
+    bsm_leftmost_2(Ps, Cs, N+1, Pos);
+bsm_leftmost_2([], Cs, _, Pos) ->
+    bsm_leftmost_1(Cs, Pos).
+
+%% bsm_nonempty(Cs, Pos) -> true|false
+%%  Check if at least one of the clauses matches a non-empty
+%%  binary in the given argument position.
+%%
+bsm_nonempty([#c_clause{pats=Ps}|Cs], Pos) ->
+    case nth(Pos, Ps) of
+	#c_binary{segments=[_|_]} ->
+	    true;
+	_ ->
+	    bsm_nonempty(Cs, Pos)
+    end;
+bsm_nonempty([], _ ) -> false.
+
+%% bsm_ensure_no_partition(Cs, Pos) -> ok     (exception if problem)
+%%  We must make sure that matching is not partitioned between
+%%  variables like this:
+%%             foo(<<...>>) -> ...
+%%             foo(<Variable>) when ... -> ...
+%%             foo(<Any non-variable pattern>) ->
+%%  If there is such partition, we are not allowed to reuse the binary variable
+%%  for the match context.
+%%
+%%  Also, arguments to the left of the argument that is matched
+%%  against a binary, are only allowed to be simple variables, not
+%%  used in guards. The reason is that we must know that the binary is
+%%  only matched in one place (i.e. there must be only one bs_start_match2
+%%  instruction emitted).
+
+bsm_ensure_no_partition(Cs, Pos) ->
+    bsm_ensure_no_partition_1(Cs, Pos, before).
+
+%% Loop through each clause.
+bsm_ensure_no_partition_1([#c_clause{pats=Ps,guard=G}|Cs], Pos, State0) ->
+    State = bsm_ensure_no_partition_2(Ps, Pos, G, simple_vars, State0),
+    case State of
+	'after' ->
+	    bsm_ensure_no_partition_after(Cs, Pos);
+	_ ->
+	    ok
+    end,
+    bsm_ensure_no_partition_1(Cs, Pos, State);
+bsm_ensure_no_partition_1([], _, _) -> ok.
+
+%% Loop through each pattern for this clause.
+bsm_ensure_no_partition_2([#c_binary{}=Where|_], 1, _, Vstate, State) ->
+    case State of
+	before when Vstate =:= simple_vars -> within;
+	before -> bsm_problem(Where, Vstate);
+	within when Vstate =:= simple_vars -> within;
+	within -> bsm_problem(Where, Vstate)
+    end;
+bsm_ensure_no_partition_2([#c_alias{}=Alias|_], 1, N, Vstate, State) ->
+    %% Retrieve the real pattern that the alias refers to and check that.
+    P = bsm_real_pattern(Alias),
+    bsm_ensure_no_partition_2([P], 1, N, Vstate, State);
+bsm_ensure_no_partition_2([_|_], 1, _, _Vstate, before=State) ->
+    %% No binary matching yet - therefore no partition.
+    State;
+bsm_ensure_no_partition_2([P|_], 1, _, Vstate, State) ->
+    case bsm_could_match_binary(P) of
+	false ->
+	    %% If clauses can be freely arranged (Vstate =:= simple_vars),
+	    %% a clause that cannot match a binary will not partition the clause.
+	    %% Example:
+	    %%
+	    %% a(Var, <<>>) -> ...
+	    %% a(Var, []) -> ...
+	    %% a(Var, <<B>>) -> ...
+	    %%
+	    %% But if the clauses can't be freely rearranged, as in
+	    %%
+	    %% b(Var, <<X>>) -> ...
+	    %% b(1, 2) -> ...
+	    %%
+	    %% we do have a problem.
+	    %%
+	    case Vstate of
+		simple_vars -> State;
+		_ -> bsm_problem(P, Vstate)
+	    end;
+	true ->
+	    %% The pattern P *may* match a binary, so we must update the state.
+	    %% (P must be a variable.)
+	    case State of
+		within -> 'after';
+		'after' -> 'after'
+	    end
+    end;
+bsm_ensure_no_partition_2([#c_var{name=V}|Ps], N, G, Vstate, S) ->
+    case core_lib:is_var_used(V, G) of
+	false ->
+	    bsm_ensure_no_partition_2(Ps, N-1, G, Vstate, S);
+	true ->
+	    bsm_ensure_no_partition_2(Ps, N-1, G, bin_left_var_used_in_guard, S)
+    end;
+bsm_ensure_no_partition_2([_|Ps], N, G, _, S) ->
+    bsm_ensure_no_partition_2(Ps, N-1, G, bin_argument_order, S).
+
+bsm_ensure_no_partition_after([#c_clause{pats=Ps}=C|Cs], Pos) ->
+    case nth(Pos, Ps) of
+	#c_var{} ->
+	    bsm_ensure_no_partition_after(Cs, Pos);
+	_ ->
+	    bsm_problem(C, bin_partition)
+    end;
+bsm_ensure_no_partition_after([], _) -> ok.
+
+bsm_could_match_binary(#c_alias{pat=P}) -> bsm_could_match_binary(P);
+bsm_could_match_binary(#c_cons{}) -> false;
+bsm_could_match_binary(#c_tuple{}) -> false;
+bsm_could_match_binary(#c_literal{val=Lit}) -> is_bitstring(Lit);
+bsm_could_match_binary(_) -> true.
+
+bsm_real_pattern(#c_alias{pat=P}) -> bsm_real_pattern(P);
+bsm_real_pattern(P) -> P.
+
+bsm_problem(Where, What) ->
+    throw({problem,Where,What}).
+
+make_warning(Core, Term) ->
+    case should_suppress_warning(Core) of
+	true ->
+	    ok;
+	false ->
+            Anno = cerl:get_ann(Core),
+            Line = get_line(Anno),
+            File = get_file(Anno),
+            {File,[{Line,?MODULE,Term}]}
+    end.
+
+should_suppress_warning(Core) ->
+    Ann = cerl:get_ann(Core),
+    member(compiler_generated, Ann).
+
+get_line([Line|_]) when is_integer(Line) -> Line;
+get_line([_|T]) -> get_line(T);
+get_line([]) -> none.
+
+get_file([{file,File}|_]) -> File;
+get_file([_|T]) -> get_file(T);
+get_file([]) -> "no_file". % should not happen
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 3673a339f6..cbf6e256f7 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -71,7 +71,7 @@
 -export([module/2,format_error/1]).
 
 -import(lists, [map/2,foldl/3,foldr/3,mapfoldl/3,all/2,any/2,
-		reverse/1,reverse/2,member/2,nth/2,flatten/1,
+		reverse/1,reverse/2,member/2,flatten/1,
 		unzip/1,keyfind/3]).
 
 -import(cerl, [ann_c_cons/3,ann_c_map/3,ann_c_tuple/2]).
@@ -107,7 +107,6 @@
 	{'ok', cerl:c_module(), [_]}.
 
 module(#c_module{defs=Ds0}=Mod, Opts) ->
-    put(bin_opt_info, member(bin_opt_info, Opts)),
     put(no_inline_list_funcs, not member(inline_list_funcs, Opts)),
     case get(new_var_num) of
 	undefined -> put(new_var_num, 0);
@@ -116,7 +115,6 @@ module(#c_module{defs=Ds0}=Mod, Opts) ->
     init_warnings(),
     Ds1 = [function_1(D) || D <- Ds0],
     erase(no_inline_list_funcs),
-    erase(bin_opt_info),
     {ok,Mod#c_module{defs=Ds1},get_warnings()}.
 
 function_1({#c_var{name={F,Arity}}=Name,B0}) ->
@@ -383,10 +381,8 @@ expr(#c_case{}=Case0, Ctxt, Sub) ->
 	    warn_no_clause_match(Case1, Case),
 	    Expr = eval_case(Case, Sub),
             case move_case_into_arg(Case, Sub) of
-                impossible ->
-                    bsm_an(Expr);
-                Other ->
-		    Other
+                impossible -> Expr;
+                Other -> Other
             end;
 	Other ->
 	    expr(Other, Ctxt, Sub)
@@ -2943,15 +2939,8 @@ update_types(Expr, Pat, #sub{t=Tdb0}=Sub) ->
     Tdb = update_types_1(Expr, Pat, Tdb0),
     Sub#sub{t=Tdb}.
 
-update_types_1(#c_var{name=V,anno=Anno}, Pat, Types) ->
-    case member(reuse_for_context, Anno) of
-	true ->
-	    %% If a variable has been marked for reuse of binary context,
-	    %% optimizations based on type information are unsafe.
-	    kill_types(V, Types);
-	false ->
-	    update_types_2(V, Pat, Types)
-    end;
+update_types_1(#c_var{name=V}, Pat, Types) ->
+    update_types_2(V, Pat, Types);
 update_types_1(_, _, Types) -> Types.
 
 update_types_2(V, [#c_tuple{}=P], Types) ->
@@ -2994,253 +2983,6 @@ copy_type(_, _, Tdb) -> Tdb.
 
 void() -> #c_literal{val=ok}.
 
-%%%
-%%% Annotate bit syntax matching to faciliate optimization in further passes.
-%%%
-
-bsm_an(#c_case{arg=#c_var{}=V}=Case) ->
-    bsm_an_1([V], Case);
-bsm_an(#c_case{arg=#c_values{es=Es}}=Case) ->
-    bsm_an_1(Es, Case);
-bsm_an(Other) -> Other.
-
-bsm_an_1(Vs, #c_case{clauses=Cs}=Case) ->
-    case bsm_leftmost(Cs) of
-	none -> Case;
-	Pos -> bsm_an_2(Vs, Cs, Case, Pos)
-    end.
-
-bsm_an_2(Vs, Cs, Case, Pos) ->
-    case bsm_nonempty(Cs, Pos) of
-	true -> bsm_an_3(Vs, Cs, Case, Pos);
-	false -> Case
-    end.
-
-bsm_an_3(Vs, Cs, Case, Pos) ->
-    try
-	bsm_ensure_no_partition(Cs, Pos),
-	bsm_do_an(Vs, Pos, Cs, Case)
-    catch
-	throw:{problem,Where,What} ->
-	    add_bin_opt_info(Where, What),
-	    Case
-    end.
-
-bsm_do_an(Vs0, Pos, Cs0, Case) ->
-    case nth(Pos, Vs0) of
-	#c_var{name=Vname}=V0 ->
-	    Cs = bsm_do_an_var(Vname, Pos, Cs0, []),
-	    V = bsm_annotate_for_reuse(V0),
-	    Bef = lists:sublist(Vs0, Pos-1),
-	    Aft = lists:nthtail(Pos, Vs0),
-	    case Bef ++ [V|Aft] of
-		[_] ->
-		    Case#c_case{arg=V,clauses=Cs};
-		Vs ->
-		    Case#c_case{arg=#c_values{es=Vs},clauses=Cs}
-	    end;
-	_ ->
-	    Case
-    end.
-
-bsm_do_an_var(V, S, [#c_clause{pats=Ps,guard=G,body=B0}=C0|Cs], Acc) ->
-    case nth(S, Ps) of
-	#c_var{name=VarName} ->
-	    case core_lib:is_var_used(V, G) of
-		true -> bsm_problem(C0, orig_bin_var_used_in_guard);
-		false -> ok
-	    end,
-	    case core_lib:is_var_used(VarName, G) of
-		true -> bsm_problem(C0, bin_var_used_in_guard);
-		false -> ok
-	    end,
-	    B1 = bsm_maybe_ctx_to_binary(VarName, B0),
-	    B = bsm_maybe_ctx_to_binary(V, B1),
-	    C = C0#c_clause{body=B},
-	    bsm_do_an_var(V, S, Cs, [C|Acc]);
-	#c_alias{}=P ->
-	    case bsm_could_match_binary(P) of
-		false ->
-		    bsm_do_an_var(V, S, Cs, [C0|Acc]);
-		true ->
-		    bsm_problem(C0, bin_opt_alias)
-	    end;
-	P ->
-	    case bsm_could_match_binary(P) andalso bsm_is_var_used(V, G, B0) of
-		false ->
-		    bsm_do_an_var(V, S, Cs, [C0|Acc]);
-		true ->
-		    bsm_problem(C0, bin_var_used)
-	    end
-    end;
-bsm_do_an_var(_, _, [], Acc) -> reverse(Acc).
-
-bsm_annotate_for_reuse(#c_var{anno=Anno}=Var) ->
-    case member(reuse_for_context, Anno) of
-	false -> Var#c_var{anno=[reuse_for_context|Anno]};
-	true -> Var
-    end.
-
-bsm_is_var_used(V, G, B) ->
-    core_lib:is_var_used(V, G) orelse core_lib:is_var_used(V, B).
-
-bsm_maybe_ctx_to_binary(V, B) ->
-    case core_lib:is_var_used(V, B) andalso not previous_ctx_to_binary(V, B) of
-	false ->
-	    B;
-	true ->
-	    #c_seq{arg=#c_primop{name=#c_literal{val=bs_context_to_binary},
-				 args=[#c_var{name=V}]},
-		   body=B}
-    end.
-
-previous_ctx_to_binary(V, Core) ->
-    case Core of
-	#c_seq{arg=#c_primop{name=#c_literal{val=bs_context_to_binary},
-			     args=[#c_var{name=V}]}} ->
-	    true;
-	_ ->
-	    false
-    end.
-
-%% bsm_leftmost(Cs) -> none | ArgumentNumber
-%%  Find the leftmost argument that does binary matching. Return
-%%  the number of the argument (1-N).
-
-bsm_leftmost(Cs) ->
-    bsm_leftmost_1(Cs, none).
-
-bsm_leftmost_1([#c_clause{pats=Ps}|Cs], Pos) ->
-    bsm_leftmost_2(Ps, Cs, 1, Pos);
-bsm_leftmost_1([], Pos) -> Pos.
-
-bsm_leftmost_2(_, Cs, Pos, Pos) ->
-    bsm_leftmost_1(Cs, Pos);
-bsm_leftmost_2([#c_binary{}|_], Cs, N, _) ->
-    bsm_leftmost_1(Cs, N);
-bsm_leftmost_2([_|Ps], Cs, N, Pos) ->
-    bsm_leftmost_2(Ps, Cs, N+1, Pos);
-bsm_leftmost_2([], Cs, _, Pos) ->
-    bsm_leftmost_1(Cs, Pos).
-
-%% bsm_nonempty(Cs, Pos) -> true|false
-%%  Check if at least one of the clauses matches a non-empty
-%%  binary in the given argument position.
-%%
-bsm_nonempty([#c_clause{pats=Ps}|Cs], Pos) ->
-    case nth(Pos, Ps) of
-	#c_binary{segments=[_|_]} ->
-	    true;
-	_ ->
-	    bsm_nonempty(Cs, Pos)
-    end;
-bsm_nonempty([], _ ) -> false.
-
-%% bsm_ensure_no_partition(Cs, Pos) -> ok     (exception if problem)
-%%  We must make sure that matching is not partitioned between
-%%  variables like this:
-%%             foo(<<...>>) -> ...
-%%             foo(<Variable>) when ... -> ...
-%%             foo(<Any non-variable pattern>) ->
-%%  If there is such partition, we are not allowed to reuse the binary variable
-%%  for the match context.
-%%
-%%  Also, arguments to the left of the argument that is matched
-%%  against a binary, are only allowed to be simple variables, not
-%%  used in guards. The reason is that we must know that the binary is
-%%  only matched in one place (i.e. there must be only one bs_start_match2
-%%  instruction emitted).
-
-bsm_ensure_no_partition(Cs, Pos) ->
-    bsm_ensure_no_partition_1(Cs, Pos, before).
-
-%% Loop through each clause.
-bsm_ensure_no_partition_1([#c_clause{pats=Ps,guard=G}|Cs], Pos, State0) ->
-    State = bsm_ensure_no_partition_2(Ps, Pos, G, simple_vars, State0),
-    case State of
-	'after' ->
-	    bsm_ensure_no_partition_after(Cs, Pos);
-	_ ->
-	    ok
-    end,
-    bsm_ensure_no_partition_1(Cs, Pos, State);
-bsm_ensure_no_partition_1([], _, _) -> ok.
-
-%% Loop through each pattern for this clause.
-bsm_ensure_no_partition_2([#c_binary{}=Where|_], 1, _, Vstate, State) ->
-    case State of
-	before when Vstate =:= simple_vars -> within;
-	before -> bsm_problem(Where, Vstate);
-	within when Vstate =:= simple_vars -> within;
-	within -> bsm_problem(Where, Vstate)
-    end;
-bsm_ensure_no_partition_2([#c_alias{}=Alias|_], 1, N, Vstate, State) ->
-    %% Retrieve the real pattern that the alias refers to and check that.
-    P = bsm_real_pattern(Alias),
-    bsm_ensure_no_partition_2([P], 1, N, Vstate, State);
-bsm_ensure_no_partition_2([_|_], 1, _, _Vstate, before=State) ->
-    %% No binary matching yet - therefore no partition.
-    State;
-bsm_ensure_no_partition_2([P|_], 1, _, Vstate, State) ->
-    case bsm_could_match_binary(P) of
-	false ->
-	    %% If clauses can be freely arranged (Vstate =:= simple_vars),
-	    %% a clause that cannot match a binary will not partition the clause.
-	    %% Example:
-	    %%
-	    %% a(Var, <<>>) -> ...
-	    %% a(Var, []) -> ...
-	    %% a(Var, <<B>>) -> ...
-	    %%
-	    %% But if the clauses can't be freely rearranged, as in
-	    %%
-	    %% b(Var, <<X>>) -> ...
-	    %% b(1, 2) -> ...
-	    %%
-	    %% we do have a problem.
-	    %%
-	    case Vstate of
-		simple_vars -> State;
-		_ -> bsm_problem(P, Vstate)
-	    end;
-	true ->
-	    %% The pattern P *may* match a binary, so we must update the state.
-	    %% (P must be a variable.)
-	    case State of
-		within -> 'after';
-		'after' -> 'after'
-	    end
-    end;
-bsm_ensure_no_partition_2([#c_var{name=V}|Ps], N, G, Vstate, S) ->
-    case core_lib:is_var_used(V, G) of
-	false ->
-	    bsm_ensure_no_partition_2(Ps, N-1, G, Vstate, S);
-	true ->
-	    bsm_ensure_no_partition_2(Ps, N-1, G, bin_left_var_used_in_guard, S)
-    end;
-bsm_ensure_no_partition_2([_|Ps], N, G, _, S) ->
-    bsm_ensure_no_partition_2(Ps, N-1, G, bin_argument_order, S).
-
-bsm_ensure_no_partition_after([#c_clause{pats=Ps}=C|Cs], Pos) ->
-    case nth(Pos, Ps) of
-	#c_var{} ->
-	    bsm_ensure_no_partition_after(Cs, Pos);
-	_ ->
-	    bsm_problem(C, bin_partition)
-    end;
-bsm_ensure_no_partition_after([], _) -> ok.
-
-bsm_could_match_binary(#c_alias{pat=P}) -> bsm_could_match_binary(P);
-bsm_could_match_binary(#c_cons{}) -> false;
-bsm_could_match_binary(#c_tuple{}) -> false;
-bsm_could_match_binary(#c_literal{val=Lit}) -> is_bitstring(Lit);
-bsm_could_match_binary(_) -> true.
-
-bsm_real_pattern(#c_alias{pat=P}) -> bsm_real_pattern(P);
-bsm_real_pattern(P) -> P.
-
-bsm_problem(Where, What) ->
-    throw({problem,Where,What}).
 
 %%%
 %%% Handling of warnings.
@@ -3249,12 +2991,6 @@ bsm_problem(Where, What) ->
 init_warnings() ->
     put({?MODULE,warnings}, []).
 
-add_bin_opt_info(Core, Term) ->
-    case get(bin_opt_info) of
-	true -> add_warning(Core, Term);
-	false -> ok
-    end.
-
 add_warning(Core, Term) ->
     case should_suppress_warning(Core) of
 	true ->
@@ -3376,28 +3112,7 @@ format_error(result_ignored) ->
 format_error(invalid_call) ->
     "invalid function call";
 format_error(useless_building) ->
-    "a term is constructed, but never used";
-format_error(bin_opt_alias) ->
-    "INFO: the '=' operator will prevent delayed sub binary optimization";
-format_error(bin_partition) ->
-    "INFO: matching non-variables after a previous clause matching a variable "
-	"will prevent delayed sub binary optimization";
-format_error(bin_left_var_used_in_guard) ->
-    "INFO: a variable to the left of the binary pattern is used in a guard; "
-	"will prevent delayed sub binary optimization";
-format_error(bin_argument_order) ->
-    "INFO: matching anything else but a plain variable to the left of "
-	"binary pattern will prevent delayed sub binary optimization; "
-	"SUGGEST changing argument order";
-format_error(bin_var_used) ->
-    "INFO: using a matched out sub binary will prevent "
-	"delayed sub binary optimization";
-format_error(orig_bin_var_used_in_guard) ->
-    "INFO: using the original binary variable in a guard will prevent "
-	"delayed sub binary optimization";
-format_error(bin_var_used_in_guard) ->
-    "INFO: using a matched out sub binary in a guard will prevent "
-	"delayed sub binary optimization".
+    "a term is constructed, but never used".
 
 -ifdef(DEBUG).
 %% In order for simplify_let/2 to work correctly, the list of
diff --git a/lib/compiler/test/bs_match_SUITE.erl b/lib/compiler/test/bs_match_SUITE.erl
index 89f851ac3b..106d8eb45a 100644
--- a/lib/compiler/test/bs_match_SUITE.erl
+++ b/lib/compiler/test/bs_match_SUITE.erl
@@ -39,7 +39,7 @@
 	 match_string_opt/1,select_on_integer/1,
 	 map_and_binary/1,unsafe_branch_caching/1,
 	 bad_literals/1,good_literals/1,constant_propagation/1,
-	 parse_xml/1]).
+	 parse_xml/1,get_payload/1]).
 
 -export([coverage_id/1,coverage_external_ignore/2]).
 
@@ -70,7 +70,8 @@ groups() ->
        no_partition,calling_a_binary,binary_in_map,
        match_string_opt,select_on_integer,
        map_and_binary,unsafe_branch_caching,
-       bad_literals,good_literals,constant_propagation,parse_xml]}].
+       bad_literals,good_literals,constant_propagation,parse_xml,
+       get_payload]}].
 
 
 init_per_suite(Config) ->
@@ -1508,6 +1509,20 @@ do_parse_xml(<<"<?xml"/utf8,Rest/binary>> = Bytes) ->
 is_next_char_whitespace(<<C/utf8,_/binary>>) ->
     C =:= $\s.
 
+-record(ext_header,
+        {this_hdr = 17,
+         ext_hdr_opts}).
+
+get_payload(Config) ->
+    <<3445:48>> = do_get_payload(#ext_header{ext_hdr_opts = <<3445:48>>}),
+    {'EXIT',_} = (catch do_get_payload(#ext_header{})),
+    ok.
+
+do_get_payload(ExtHdr) ->
+    _ = ExtHdr#ext_header.this_hdr,
+    ExtHdrOptions = ExtHdr#ext_header.ext_hdr_opts,
+    <<_:13,_:35>> = ExtHdr#ext_header.ext_hdr_opts,
+    ExtHdrOptions.
 
 check(F, R) ->
     R = F().
diff --git a/lib/compiler/test/compile_SUITE.erl b/lib/compiler/test/compile_SUITE.erl
index 4e2753ba5f..f647a4030d 100644
--- a/lib/compiler/test/compile_SUITE.erl
+++ b/lib/compiler/test/compile_SUITE.erl
@@ -371,6 +371,7 @@ do_file_listings(DataDir, PrivDir, [File|Files]) ->
     do_listing(Simple, TargetDir, dinline, ".inline"),
     do_listing(Simple, TargetDir, dcore, ".core"),
     do_listing(Simple, TargetDir, dcopt, ".copt"),
+    do_listing(Simple, TargetDir, dcbsm, ".core_bsm"),
     do_listing(Simple, TargetDir, dsetel, ".dsetel"),
     do_listing(Simple, TargetDir, dkern, ".kernel"),
     do_listing(Simple, TargetDir, dlife, ".life"),
diff --git a/lib/compiler/test/misc_SUITE.erl b/lib/compiler/test/misc_SUITE.erl
index 01b064cc10..4bd884d86b 100644
--- a/lib/compiler/test/misc_SUITE.erl
+++ b/lib/compiler/test/misc_SUITE.erl
@@ -161,11 +161,12 @@ md5_1(Beam) ->
 %% Cover some code that handles internal errors.
 
 silly_coverage(Config) when is_list(Config) ->
-    %% sys_core_fold, sys_core_setel, v3_kernel
+    %% sys_core_fold, sys_core_bsm, sys_core_setel, v3_kernel
     BadCoreErlang = {c_module,[],
 		     name,[],[],
 		     [{{c_var,[],{foo,2}},seriously_bad_body}]},
     expect_error(fun() -> sys_core_fold:module(BadCoreErlang, []) end),
+    expect_error(fun() -> sys_core_bsm:module(BadCoreErlang, []) end),
     expect_error(fun() -> sys_core_dsetel:module(BadCoreErlang, []) end),
     expect_error(fun() -> v3_kernel:module(BadCoreErlang, []) end),
 
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index 7c27750556..77e4234c70 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -529,7 +529,7 @@ bin_opt_info(Config) when is_list(Config) ->
 	    Code,
 	    [bin_opt_info],
 	    {warnings,
-	     [{4,sys_core_fold,orig_bin_var_used_in_guard},
+	     [{4,sys_core_bsm,orig_bin_var_used_in_guard},
 	      {5,beam_bsm,{no_bin_opt,{{t1,1},no_suitable_bs_start_match}}},
 	      {9,beam_bsm,{no_bin_opt,
 			   {binary_used_in,{extfunc,erlang,split_binary,2}}}} ]}}],