Compiler: fix toplevel with globaldeacode

Author: hhugo

CHANGES.md

@@ -5,6 +5,9 @@
 * Compiler: no longer rely on IIFE for scoping variable inside loops
 * Lib: add ellipse to canvasRenderingContext2D (@FayCarsons, #1555)
 
+## Bug fixes
+* Compiler: fix global dead code elimination in a toplevel context
+
 # 5.6.0 (2024-01-02) - Lille
 
 ## Features/Changes

compiler/lib/global_deadcode.ml

@@ -246,6 +246,15 @@ let liveness prog pure_funs (global_info : Global_flow.info) =
     | Stop | Branch _ | Poptrap _ | Pushtrap _ -> ()
   in
   Addr.Map.iter (fun _ block -> live_block block) prog.blocks;
+  Code.traverse
+    { Code.fold = Code.fold_children }
+    (fun pc () ->
+      match Addr.Map.find pc prog.blocks with
+      | { branch = Return x, _; _ } -> add_top x
+      | _ -> ())
+    prog.start
+    prog.blocks
+    ();
   live_vars
 
 (* Returns the set of variables given a table of variables. *)

compiler/tests-toplevel/test_toplevel.reference

@@ -1,4 +1,5 @@
 hello
+- : int = 2
 Line 4, characters 2-4:
 Error: Syntax error
 Line 5, characters 0-16: