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.

2 files changed, 26 insertions, 0 deletions

diff --git a/erts/emulator/beam/instrs.tab b/erts/emulator/beam/instrs.tab
index b92152238e..f19027b1ec 100644
--- a/erts/emulator/beam/instrs.tab
+++ b/erts/emulator/beam/instrs.tab
@@ -936,3 +936,28 @@ build_stacktrace() {
     x(0) = build_stacktrace(c_p, x(0));
     SWAPIN;
 }
+
+raw_raise() {
+    Eterm class = x(0);
+    Eterm value = x(1);
+    Eterm stacktrace = x(2);
+
+    if (class == am_error) {
+        c_p->freason = EXC_ERROR & ~EXF_SAVETRACE;
+        c_p->fvalue = value;
+        c_p->ftrace = stacktrace;
+        goto find_func_info;
+    } else if (class == am_exit) {
+        c_p->freason = EXC_EXIT & ~EXF_SAVETRACE;
+        c_p->fvalue = value;
+        c_p->ftrace = stacktrace;
+        goto find_func_info;
+    } else if (class == am_throw) {
+        c_p->freason = EXC_THROWN & ~EXF_SAVETRACE;
+        c_p->fvalue = value;
+        c_p->ftrace = stacktrace;
+        goto find_func_info;
+    } else {
+        x(0) = am_badarg;
+    }
+}
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index fd1b3b9c74..1f4a8eadb0 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -1584,3 +1584,4 @@ i_recv_set
 #
 
 build_stacktrace
+raw_raise