[fuzz] Fix order of operands passed in to wasm-spec-interpreter

In bytecodealliance#4671, the meta-differential fuzz target was finding errors when
running certain Wasm modules (specifically `shr_s` in that case).
@conrad-watt diagnosed the issue as a missing reversal in the operands
passed to the spec interpreter. This change fixes bytecodealliance#4671 and adds an
additional unit test to keep it fixed.

crates/fuzzing/wasm-spec-interpreter/ocaml/interpret.ml

@@ -55,7 +55,7 @@ let extract_exported_func export = match export with
 (** Interpret the first exported function and return the result. Use provided
 parameters if they exist, otherwise use default (zeroed) values. *)
 let interpret_exn module_bytes opt_params =
-  let opt_params_ = Option.map (List.map convert_to_wasm) opt_params in
+  let opt_params_ = Option.map (List.rev_map convert_to_wasm) opt_params in
   let module_ = parse module_bytes in
   let m_isa = Ast_convert.convert_module (module_.it) in
   let fuel = Z.of_string "4611686018427387904" in

crates/fuzzing/wasm-spec-interpreter/src/with_library.rs

@@ -119,4 +119,15 @@ mod tests {
             ])]
         );
     }
+
+    // See issue https://github.com/bytecodealliance/wasmtime/issues/4671.
+    #[test]
+    fn order_of_params() {
+        let module = wat::parse_file("tests/shr_s.wat").unwrap();
+
+        let parameters = Some(vec![Value::I32(1795123818), Value::I32(-2147483648)]);
+        let results = interpret(&module, parameters.clone()).unwrap();
+
+        assert_eq!(results, vec![Value::I32(1795123818)]);
+    }
 }

crates/fuzzing/wasm-spec-interpreter/tests/shr_s.wat

@@ -0,0 +1,9 @@
+(module
+  (type (;0;) (func (param i32 i32) (result i32)))
+  (func (;0;) (type 0) (param i32 i32) (result i32)
+    local.get 0
+    local.get 1
+    i32.shr_s
+  )
+  (export "test" (func 0))
+)