From f52f195ef8896810a3ba0ad66281728fd3040b8c Mon Sep 17 00:00:00 2001
From: Tobias Pfeiffer <pragtob@gmail.com>
Date: Thu, 16 Nov 2023 09:31:42 +0100
Subject: [PATCH] Basic exposure of jit_enabled? data in system

---
 lib/benchee/system.ex        | 14 +++++++++++++-
 test/benchee/system_test.exs | 17 ++++++++++++++++-
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/lib/benchee/system.ex b/lib/benchee/system.ex
index 9d015d0c..35f35e55 100644
--- a/lib/benchee/system.ex
+++ b/lib/benchee/system.ex
@@ -9,15 +9,18 @@ defmodule Benchee.System do
 
   alias Benchee.Conversion.Memory
   alias Benchee.Suite
+  alias Benchee.Utility.ErlangVersion
 
   @doc """
   Adds system information to the suite (currently elixir and erlang versions).
   """
   @spec system(Suite.t()) :: Suite.t()
   def system(suite = %Suite{}) do
+    erlang_version = erlang()
     system_info = %{
       elixir: elixir(),
-      erlang: erlang(),
+      erlang: erlang_version,
+      jit_enabled?: jit_enabled?(erlang_version),
       num_cores: num_cores(),
       os: os(),
       available_memory: available_memory(),
@@ -50,6 +53,15 @@ defmodule Benchee.System do
 
   defp elixir, do: System.version()
 
+  @first_jit_version "24.0.0"
+  defp jit_enabled?(erlang_version) do
+    if ErlangVersion.includes_fixes_from?(erlang_version, @first_jit_version) do
+      :erlang.system_info(:emu_flavor) == :jit
+    else
+      false
+    end
+  end
+
   defp num_cores do
     System.schedulers_online()
   end
diff --git a/test/benchee/system_test.exs b/test/benchee/system_test.exs
index e83f4d3b..0a0bb9a8 100644
--- a/test/benchee/system_test.exs
+++ b/test/benchee/system_test.exs
@@ -1,10 +1,12 @@
 defmodule Benchee.SystemTest do
   use ExUnit.Case, async: true
 
-  alias Benchee.Suite
   import ExUnit.CaptureIO
   import Benchee.System
 
+  alias Benchee.Suite
+  alias Benchee.Utility.ErlangVersion
+
   test ".system adds the content to a given suite" do
     system_info = system(%Suite{})
 
@@ -121,4 +123,17 @@ defmodule Benchee.SystemTest do
       assert warning =~ ~r/not.*check.*protocol.*consolidat/i
     end
   end
+
+  # It may be compiled in a way that it doesn't but in the CI and dev machines it should be fine
+  test ".jit_enabled? should say true for versions > 24.0.0" do
+    system_data = system(%Suite{}).system
+    jit_enabled? = system_data.jit_enabled?
+    erlang_version = system_data.erlang
+
+    if ErlangVersion.includes_fixes_from?(erlang_version, "24.0.0") do
+      assert jit_enabled?
+    else
+      refute jit_enabled?
+    end
+  end
 end