File 1671-compiler-Start-all-potential-nif-functions... of Package erlang

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File 1671-compiler-Start-all-potential-nif-functions-with-a-ni.patch of Package erlang (Revision db1acd30fa2136b2cf32ed954074cb8e)

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From 724da95cd04d2bc1d6cb89d1988b58b2096d59cd Mon Sep 17 00:00:00 2001
From: Frej Drejhammar <frej.drejhammar@gmail.com>
Date: Fri, 29 Jul 2022 12:06:09 +0200
Subject: [PATCH] compiler: Start all potential nif functions with a nif_start
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Since OTP 25 the `nifs` attribute can be used to declare which
functions are nifs. When the `nifs` attribute is present, the runtime
system will ensure that only functions listed in the attribute are
replaced by a native implementation when `erlang:load_nif/2` is
called. Functions listed in the `nifs` attribute are flagged by
emitting a `nif_start` operation as the first instruction in the
function.

Due to backwards compatibility, the `nifs` attribute is not required,
so when a module containing a call to `erlang:load_nif/2` is
encountered, the compiler is forced to conservatively assume that in
such a module, all functions are potential nifs. Currently most of the
more powerful compiler optimizations (beam_ssa_opt.erl) are completely
disabled when a module contains a call to `erlang:load_nif/2`. It has
been suggested by Björn Gustavsson and Sverker Eriksson that switching
to a more fine-grained approach where only functions that are
potential nifs are excluded from, or treated as external functions,
during optimization would be an improvement.

This patch extends the v3_core-pass to make all functions start with a
`nif_start` instruction when the `nifs` attribute isn't present in the
module but a call to `erlang:load_nif/2` is. With this change, later
compiler passes can safely assume that a function not starting with a
`nif_start` instruction is not a nif regardless of the presence of a
call to `erlang:load_nif/2` in the module.
---
 lib/compiler/src/v3_core.erl              | 60 ++++++++++++++++++-----
 lib/compiler/test/core_SUITE.erl          | 54 +++++++++++++++++++-
 lib/compiler/test/core_SUITE_data/nif.erl | 17 +++++++
 3 files changed, 118 insertions(+), 13 deletions(-)
 create mode 100644 lib/compiler/test/core_SUITE_data/nif.erl

diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 34959a5834..16b3ac340f 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -160,7 +160,8 @@
 	       opts=[]     :: [compile:option()], %Options.
                dialyzer=false :: boolean(),     %Help dialyzer or not.
 	       ws=[]    :: [warning()],		%Warnings.
-               file=[{file,""}]			%File.
+               file=[{file,""}],                %File.
+               load_nif=false :: boolean()      %true if calls erlang:load_nif/2
 	      }).
 
 %% XXX: The following type declarations do not belong in this module
@@ -171,12 +172,16 @@
 
 -record(imodule, {name = [],
 		  exports = ordsets:new(),
-                  nifs = sets:new([{version, 2}]),
+                  nifs = none ::
+                    'none' | sets:set(), % Is a set if the attribute is
+                                         % present in the module.
 		  attrs = [],
 		  defs = [],
 		  file = [],
 		  opts = [],
-		  ws = []}).
+		  ws = [],
+                  load_nif=false :: boolean() %true if calls erlang:load_nif/2
+                 }).
 
 -spec module([form()], [compile:option()]) ->
         {'ok',cerl:c_module(),[warning()]}.
@@ -186,19 +191,28 @@ module(Forms0, Opts) ->
     Module = foldl(fun (F, Acc) ->
 			   form(F, Acc, Opts)
 		   end, #imodule{}, Forms),
-    #imodule{name=Mod,exports=Exp0,attrs=As0,defs=Kfs0,ws=Ws} = Module,
+    #imodule{name=Mod,exports=Exp0,attrs=As0,
+             defs=Kfs0,ws=Ws,load_nif=LoadNif,nifs=Nifs} = Module,
     Exp = case member(export_all, Opts) of
 	      true -> defined_functions(Forms);
 	      false -> Exp0
 	  end,
     Cexp = [#c_var{name=FA} || {_,_}=FA <- Exp],
+    Kfs1 = reverse(Kfs0),
+    Kfs = if LoadNif and (Nifs =:= none) ->
+                  insert_nif_start(Kfs1);
+             true ->
+                  Kfs1
+          end,
     As = reverse(As0),
-    Kfs = reverse(Kfs0),
+
     {ok,#c_module{name=#c_literal{val=Mod},exports=Cexp,attrs=As,defs=Kfs},Ws}.
 
-form({function,_,_,_,_}=F0, #imodule{defs=Defs}=Module, Opts) ->
-    {F,Ws} = function(F0, Module, Opts),
-    Module#imodule{defs=[F|Defs],ws=Ws};
+form({function,_,_,_,_}=F0,
+     #imodule{defs=Defs,load_nif=LoadNif0}=Module,
+     Opts) ->
+    {F,Ws,LoadNif} = function(F0, Module, Opts),
+    Module#imodule{defs=[F|Defs],ws=Ws,load_nif=LoadNif or LoadNif0};
 form({attribute,_,module,Mod}, Module, _Opts) ->
     true = is_atom(Mod),
     Module#imodule{name=Mod};
@@ -211,7 +225,13 @@ form({attribute,_,export,Es}, #imodule{exports=Exp0}=Module, _Opts) ->
     Exp = ordsets:union(ordsets:from_list(Es), Exp0),
     Module#imodule{exports=Exp};
 form({attribute,_,nifs,Ns}, #imodule{nifs=Nifs0}=Module, _Opts) ->
-    Nifs = sets:union(sets:from_list(Ns, [{version,2}]), Nifs0),
+    Nifs1 = case Nifs0 of
+                none ->
+                    sets:new([{version, 2}]);
+                _ ->
+                    Nifs0
+            end,
+    Nifs = sets:union(sets:from_list(Ns, [{version,2}]), Nifs1),
     Module#imodule{nifs=Nifs};
 form({attribute,_,_,_}=F, #imodule{attrs=As}=Module, _Opts) ->
     Module#imodule{attrs=[attribute(F)|As]};
@@ -249,9 +269,9 @@ function({function,_,Name,Arity,Cs0}, Module, Opts)
         %% ok = function_dump(Name, Arity, "ubody:~n~p~n",[B1]),
         {B2,St3} = cbody(B1, Nifs, St2),
         %% ok = function_dump(Name, Arity, "cbody:~n~p~n",[B2]),
-        {B3,#core{ws=Ws}} = lbody(B2, St3),
+        {B3,#core{ws=Ws,load_nif=LoadNif}} = lbody(B2, St3),
         %% ok = function_dump(Name, Arity, "lbody:~n~p~n",[B3]),
-        {{#c_var{name={Name,Arity}},B3},Ws}
+        {{#c_var{name={Name,Arity}},B3},Ws,LoadNif}
     catch
         Class:Error:Stack ->
 	    io:fwrite("Function: ~w/~w\n", [Name,Arity]),
@@ -860,6 +880,9 @@ expr({call,L,{remote,_,M0,F0},As0}, St0) ->
                             name=#c_literal{val=match_fail},
                             args=[Tuple]},
             {Fail,Aps,St1};
+        {#c_literal{val=erlang},#c_literal{val=load_nif},[_,_]} ->
+            {#icall{anno=#a{anno=Anno},module=M1,name=F1,args=As1},
+             Aps,St1#core{load_nif=true}};
         {_,_,_} ->
             {#icall{anno=#a{anno=Anno},module=M1,name=F1,args=As1},Aps,St1}
     end;
@@ -3031,6 +3054,9 @@ ren_is_subst(_V, []) -> no.
 %% from case/receive.  In subblocks/clauses the AfterVars of the block
 %% are just the exported variables.
 
+cbody(B0, none, St0) ->
+    {B1,_,_,St1} = cexpr(B0, [], St0),
+    {B1,St1};
 cbody(B0, Nifs, St0) ->
     {B1,_,_,St1} = cexpr(B0, [], St0),
     B2 = case sets:is_element(St1#core.function,Nifs) of
@@ -3879,6 +3905,18 @@ is_simple(_) -> false.
 
 is_simple_list(Es) -> lists:all(fun is_simple/1, Es).
 
+insert_nif_start([VF={V,F=#c_fun{body=Body}}|Funs]) ->
+    case Body of
+        #c_seq{arg=#c_primop{name=#c_literal{val=nif_start}}} ->
+            [VF|insert_nif_start(Funs)];
+        #c_case{} ->
+            NifStart = #c_primop{name=#c_literal{val=nif_start},args=[]},
+            [{V,F#c_fun{body=#c_seq{arg=NifStart,body=Body}}}
+            |insert_nif_start(Funs)]
+    end;
+insert_nif_start([]) ->
+    [].
+
 %%%
 %%% Handling of warnings.
 %%%
diff --git a/lib/compiler/test/core_SUITE.erl b/lib/compiler/test/core_SUITE.erl
index a17ad9c6ad..6bc7b1442d 100644
--- a/lib/compiler/test/core_SUITE.erl
+++ b/lib/compiler/test/core_SUITE.erl
@@ -31,7 +31,7 @@
 	 cover_v3_kernel_4/1,cover_v3_kernel_5/1,
          non_variable_apply/1,name_capture/1,fun_letrec_effect/1,
          get_map_element/1,receive_tests/1,
-         core_lint/1]).
+         core_lint/1,nif/1,no_nif/1,no_load_nif/1]).
 
 -include_lib("common_test/include/ct.hrl").
 
@@ -61,7 +61,7 @@ groups() ->
        cover_v3_kernel_4,cover_v3_kernel_5,
        non_variable_apply,name_capture,fun_letrec_effect,
        get_map_element,receive_tests,
-       core_lint
+       core_lint,nif,no_nif,no_load_nif
       ]}].
 
 
@@ -170,3 +170,53 @@ core_lint_function(Exports, Attributes, Body) ->
                          (_) -> true
                       end, Errors),
     error = compile:forms(Mod, [from_core,clint0,report]).
+
+nif(Conf) ->
+    %% Check that only the function in the nif attribute starts with nif_start
+    Funs =
+	nif_compile_to_cerl(Conf, [{d,'WITH_ATTRIBUTE'},{d,'WITH_LOAD_NIF'}]),
+    false = nif_first_instruction_is_nif_start(init, 1, Funs),
+    true = nif_first_instruction_is_nif_start(start, 1, Funs),
+    false = nif_first_instruction_is_nif_start(module_info, 0, Funs),
+    false = nif_first_instruction_is_nif_start(module_info, 1, Funs),
+    ok.
+
+no_nif(Conf) ->
+    %% Check that all functions start with nif_start
+    Funs = nif_compile_to_cerl(Conf, [{d,'WITH_LOAD_NIF'}]),
+    true = nif_first_instruction_is_nif_start(init, 1, Funs),
+    true = nif_first_instruction_is_nif_start(start, 1, Funs),
+    true = nif_first_instruction_is_nif_start(module_info, 0, Funs),
+    true = nif_first_instruction_is_nif_start(module_info, 1, Funs),
+    ok.
+
+no_load_nif(Conf) ->
+    %% Check that no functions start with nif_start
+    Funs = nif_compile_to_cerl(Conf, []),
+    false = nif_first_instruction_is_nif_start(init, 1, Funs),
+    false = nif_first_instruction_is_nif_start(start, 1, Funs),
+    false = nif_first_instruction_is_nif_start(module_info, 0, Funs),
+    false = nif_first_instruction_is_nif_start(module_info, 1, Funs),
+    ok.
+
+nif_compile_to_cerl(Conf, Flags) ->
+    Src = filename:join(proplists:get_value(data_dir, Conf), "nif.erl"),
+    {ok, _, F} = compile:file(Src, [to_core, binary, deterministic]++Flags),
+    Defs = cerl:module_defs(F),
+    [ {cerl:var_name(V),cerl:fun_body(Def)} || {V,Def} <- Defs].
+
+nif_first_instruction_is_nif_start(F, A, [{{F,A},Body}|_]) ->
+    try
+	Primop = cerl:seq_arg(Body),
+	Name = cerl:primop_name(Primop),
+	0 = cerl:primop_arity(Primop),
+	nif_start = cerl:atom_val(Name),
+	true
+    catch
+	error:_ ->
+	    false
+    end;
+nif_first_instruction_is_nif_start(F, A, [_|Rest]) ->
+    nif_first_instruction_is_nif_start(F, A, Rest);
+nif_first_instruction_is_nif_start(_, _, []) ->
+    not_found.
diff --git a/lib/compiler/test/core_SUITE_data/nif.erl b/lib/compiler/test/core_SUITE_data/nif.erl
new file mode 100644
index 0000000000..873e20252b
--- /dev/null
+++ b/lib/compiler/test/core_SUITE_data/nif.erl
@@ -0,0 +1,17 @@
+-module(nif).
+
+-export([init/1, start/1]).
+
+-ifdef(WITH_ATTRIBUTE).
+-nifs([start/1]).
+-endif.
+
+-ifdef(WITH_LOAD_NIF).
+init(File) ->
+    ok = erlang:load_nif(File, 0).
+-else.
+init(_File) ->
+    ok.
+-endif.
+
+start(_) -> erlang:nif_error(not_loaded).
-- 
2.35.3

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