From 9b0122b65bdcafbae2a3cfd3299903da0948acab Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 28 Nov 2017 07:28:25 +0100
Subject: Don't build a stacktrace if it's only passed to erlang:raise/3

Consider the following function:

    function({function,Name,Arity,CLabel,Is0}, Lc0) ->
      try
        %% Optimize the code for the function.
      catch
        Class:Error:Stack ->
          io:format("Function: ~w/~w\n", [Name,Arity]),
          erlang:raise(Class, Error, Stack)
      end.

The stacktrace is retrieved, but it is only used in the call
to erlang:raise/3. There is no need to build a stacktrace
in this function. We can avoid the building if we introduce
an instruction called raw_raise/3 that works exactly like
the erlang:raise/3 BIF except that its third argument must
be a raw stacktrace.
---
 lib/hipe/icode/hipe_beam_to_icode.erl | 6 ++++++
 lib/hipe/icode/hipe_icode_primops.erl | 5 +++++
 lib/hipe/icode/hipe_icode_range.erl   | 3 ++-
 3 files changed, 13 insertions(+), 1 deletion(-)

(limited to 'lib/hipe/icode')

diff --git a/lib/hipe/icode/hipe_beam_to_icode.erl b/lib/hipe/icode/hipe_beam_to_icode.erl
index 7ff9fd83eb..6e66ec057c 100644
--- a/lib/hipe/icode/hipe_beam_to_icode.erl
+++ b/lib/hipe/icode/hipe_beam_to_icode.erl
@@ -1164,6 +1164,12 @@ trans_fun([build_stacktrace|Instructions], Env) ->
   Vars = [mk_var({x,0})], %{x,0} is implict arg and dst
   [hipe_icode:mk_primop(Vars,build_stacktrace,Vars),
    trans_fun(Instructions, Env)];
+%%--- raw_raise ---
+trans_fun([raw_raise|Instructions], Env) ->
+  Vars = [mk_var({x,0}),mk_var({x,1}),mk_var({x,2})],
+  Dst = [mk_var({x,0})],
+  [hipe_icode:mk_primop(Dst,raw_raise,Vars) |
+   trans_fun(Instructions, Env)];
 %%--------------------------------------------------------------------
 %%--- ERROR HANDLING ---
 %%--------------------------------------------------------------------
diff --git a/lib/hipe/icode/hipe_icode_primops.erl b/lib/hipe/icode/hipe_icode_primops.erl
index 941516e8b1..a1f1128124 100644
--- a/lib/hipe/icode/hipe_icode_primops.erl
+++ b/lib/hipe/icode/hipe_icode_primops.erl
@@ -236,6 +236,7 @@ fails({hipe_bs_primop, {bs_append, _, _, _, _}}) -> true;
 fails({hipe_bs_primop, {bs_private_append, _, _}}) -> true;
 fails({hipe_bs_primop, bs_init_writable}) -> true;
 fails(build_stacktrace) -> false;
+fails(raw_raise) -> true;
 fails(#mkfun{}) -> false;
 fails(#unsafe_element{}) -> false;
 fails(#unsafe_update_element{}) -> false;
@@ -735,6 +736,8 @@ type(Primop, Args) ->
       erl_types:t_any();
     build_stacktrace ->
       erl_types:t_list();
+    raw_raise ->
+      erl_types:t_atom();
     {M, F, A} ->
       erl_bif_types:type(M, F, A, Args)
   end.
@@ -909,6 +912,8 @@ type(Primop) ->
 %%% Other
     build_stacktrace ->
       erl_types:t_any();
+    raw_raise ->
+      erl_types:t_any();
     #closure_element{} ->
       erl_types:t_any();
     redtest ->
diff --git a/lib/hipe/icode/hipe_icode_range.erl b/lib/hipe/icode/hipe_icode_range.erl
index cf74c1eb5b..34b18acccd 100644
--- a/lib/hipe/icode/hipe_icode_range.erl
+++ b/lib/hipe/icode/hipe_icode_range.erl
@@ -1187,7 +1187,8 @@ basic_type(unsafe_tl) -> not_int;
 basic_type(#element{}) -> not_analysed;
 basic_type(#unsafe_element{}) -> not_analysed;
 basic_type(#unsafe_update_element{}) -> not_analysed;
-basic_type(build_stacktrace) -> not_int.
+basic_type(build_stacktrace) -> not_int;
+basic_type(raw_raise) -> not_int.
 
 -spec analyse_bs_get_integer(integer(), integer(), boolean()) -> range_tuple().
 
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