Wasm AST: add br_on_null

Author: vouillon

compiler/lib-wasm/code_generation.ml

@@ -453,6 +453,7 @@ let rec is_smi e =
   | RefNull _
   | Br_on_cast _
   | Br_on_cast_fail _
+  | Br_on_null _ -> false
   | Try _ -> false
   | BinOp ((F32 _ | F64 _), _, _) | RefTest _ | RefEq _ -> true
   | IfExpr (_, _, ift, iff) -> is_smi ift && is_smi iff

compiler/lib-wasm/gc_target.ml

@@ -527,6 +527,7 @@ module Value = struct
     | Call_ref _
     | Br_on_cast _
     | Br_on_cast_fail _
+    | Br_on_null _
     | Try _ -> false
     | IfExpr (_, e1, e2, e3) -> effect_free e1 && effect_free e2 && effect_free e3
     | ArrayNewFixed (_, l) | StructNew (_, l) -> List.for_all ~f:effect_free l

compiler/lib-wasm/initialize_locals.ml

@@ -46,7 +46,8 @@ let rec scan_expression ctx e =
   | RefCast (_, e')
   | RefTest (_, e')
   | Br_on_cast (_, _, _, e')
-  | Br_on_cast_fail (_, _, _, e') -> scan_expression ctx e'
+  | Br_on_cast_fail (_, _, _, e')
+  | Br_on_null (_, e') -> scan_expression ctx e'
   | BinOp (_, e', e'')
   | ArrayNew (_, e', e'')
   | ArrayNewData (_, _, e', e'')

compiler/lib-wasm/wasm_ast.ml

@@ -164,6 +164,7 @@ type expression =
   | RefNull of heap_type
   | Br_on_cast of int * ref_type * ref_type * expression
   | Br_on_cast_fail of int * ref_type * ref_type * expression
+  | Br_on_null of int * expression
   | IfExpr of value_type * expression * expression * expression
   | Try of func_type * instruction list * (var * int * value_type) list
 

compiler/lib-wasm/wasm_output.ml

@@ -638,6 +638,11 @@ end = struct
         output_uint ch i;
         output_heaptype st.type_names ch typ1.typ;
         output_heaptype st.type_names ch typ2.typ
+    | Br_on_null (i, e') ->
+        Feature.require gc;
+        output_expression st ch e';
+        output_byte ch 0xD5;
+        output_uint ch i
     | IfExpr (typ, e1, e2, e3) ->
         output_expression st ch e1;
         output_byte ch 0x04;
@@ -871,7 +876,8 @@ end = struct
     | RefCast (_, e')
     | RefTest (_, e')
     | Br_on_cast (_, _, _, e')
-    | Br_on_cast_fail (_, _, _, e') -> expr_function_references e' set
+    | Br_on_cast_fail (_, _, _, e')
+    | Br_on_null (_, e') -> expr_function_references e' set
     | BinOp (_, e', e'')
     | ArrayNew (_, e', e'')
     | ArrayNewData (_, _, e', e'')

compiler/lib-wasm/wat_output.ml

@@ -436,6 +436,8 @@ let expression_or_instructions ctx st in_function =
             :: ref_type st ty'
             :: expression e)
         ]
+    | Br_on_null (i, e) ->
+        [ List (Atom "br_on_null" :: Atom (string_of_int i) :: expression e) ]
     | IfExpr (ty, cond, ift, iff) ->
         [ List
             ((Atom "if" :: block_type st { params = []; result = [ ty ] })