From 02b6630303396fb7d9e61688a1480c64271f065e Mon Sep 17 00:00:00 2001
From: Chris Casinghino <ccasinghino@janestreet.com>
Date: Mon, 27 May 2024 13:49:41 +0800
Subject: [PATCH] Add test case for the begin_region / end_region stuff

---
 .../validate/test-validate/test-mls/generated-rules.inc  | 8 ++++++++
 .../validate/test-validate/test-mls/region_elim.ml       | 9 +++++++++
 .../validate/test-validate/test-mls/region_elim.mli      | 1 +
 3 files changed, 18 insertions(+)
 create mode 100644 middle_end/flambda2/validate/test-validate/test-mls/region_elim.ml
 create mode 100644 middle_end/flambda2/validate/test-validate/test-mls/region_elim.mli

diff --git a/middle_end/flambda2/validate/test-validate/test-mls/generated-rules.inc b/middle_end/flambda2/validate/test-validate/test-mls/generated-rules.inc
index 7392ec76a1b..86f4583baa6 100644
--- a/middle_end/flambda2/validate/test-validate/test-mls/generated-rules.inc
+++ b/middle_end/flambda2/validate/test-validate/test-mls/generated-rules.inc
@@ -42,3 +42,11 @@
   (action
    (progn
    (run %{bin:ocamlopt.opt} -c -validate cse.mli cse.ml))))
+
+(rule
+  (alias runtest)
+  (enabled_if (= %{context_name} "main"))
+  (deps region_elim.ml region_elim.mli)
+  (action
+   (progn
+   (run %{bin:ocamlopt.opt} -c -validate region_elim.mli region_elim.ml))))
diff --git a/middle_end/flambda2/validate/test-validate/test-mls/region_elim.ml b/middle_end/flambda2/validate/test-validate/test-mls/region_elim.ml
new file mode 100644
index 00000000000..2ac8ecad537
--- /dev/null
+++ b/middle_end/flambda2/validate/test-validate/test-mls/region_elim.ml
@@ -0,0 +1,9 @@
+(* This gets compiled to a program with a begin_region / end_region pair creating a region
+   that is never allocated in. We had to add a special case for this, as does flambda2.
+   See [Normalize.remove_corresponding_end_region] and its interactions with the
+   [Can_delete_if_unused] case of [step_let] (which fires for [Begin_region] *)
+
+let trim () =
+  let _ = ref 0 in
+  ()
+
diff --git a/middle_end/flambda2/validate/test-validate/test-mls/region_elim.mli b/middle_end/flambda2/validate/test-validate/test-mls/region_elim.mli
new file mode 100644
index 00000000000..0a1c6682419
--- /dev/null
+++ b/middle_end/flambda2/validate/test-validate/test-mls/region_elim.mli
@@ -0,0 +1 @@
+val trim : unit -> unit