message: Remove pointer_type field
  Easier to just get this directly from `module.isa()` each time.
diff: @@ -177,7 +177,6 @@ struct Translator<M: Module> {
  module: M,
  context: cranelift_codegen::Context,
  funcs: HashMap<String, cranelift_module::FuncId>,
  - pointer_type: ir::Type,
  }
  /// Declare all our runtime functions in a CLIF module.
  @@ -222,7 +221,6 @@ impl Translator<ObjectModule> {
  fn new(target: Option<String>, opt_level: &str) -> Self {
  // Make an object module.
  let isa = get_isa(target, true, opt_level);
  - let pointer_type = isa.pointer_type();
  let mut module =
  ObjectModule::new(ObjectBuilder::new(isa, "foo", default_libcall_names()).unwrap());
  @@ -231,7 +229,6 @@ impl Translator<ObjectModule> {
  module,
  context: cranelift_codegen::Context::new(),
  funcs: HashMap::new(),
  - pointer_type,
  }
  }
  @@ -248,14 +245,12 @@ impl Translator<JITModule> {
  // Cranelift JIT scaffolding.
  let builder = JITBuilder::new(cranelift_module::default_libcall_names()).unwrap();
  let mut module = JITModule::new(builder);
  - let pointer_type = module.isa().pointer_type();
  Self {
  rt_funcs: declare_rt(&mut module),
  context: module.make_context(),
  module,
  funcs: HashMap::new(),
  - pointer_type,
  }
  }
  @@ -593,12 +588,13 @@ impl<M: Module> Translator<M> {
  /// Generate a proper `main` function that calls the Bril `main` function.
  fn add_main(&mut self, args: &[bril::Argument], dump: bool) {
  // Declare `main` with argc/argv parameters.
  + let pointer_type = self.module.isa().pointer_type();
  let sig = ir::Signature {
  params: vec![
  - ir::AbiParam::new(self.pointer_type),
  - ir::AbiParam::new(self.pointer_type),
  + ir::AbiParam::new(pointer_type),
  + ir::AbiParam::new(pointer_type),
  ],
  - returns: vec![ir::AbiParam::new(self.pointer_type)],
  + returns: vec![ir::AbiParam::new(pointer_type)],
  call_conv: self.module.isa().default_call_conv(),
  };
  let main_id = self
  @@ -618,7 +614,7 @@ impl<M: Module> Translator<M> {
  .declare_function(
  rt_setup_func.name(),
  cranelift_module::Linkage::Import,
  - &rt_setup_func.sig(self.pointer_type, call_conv),
  + &rt_setup_func.sig(pointer_type, call_conv),
  )
  .unwrap();
  self
  @@ -657,7 +653,7 @@ impl<M: Module> Translator<M> {
  builder.ins().call(real_main_ref, &arg_vals);
  // Return 0 from `main`.
  - let zero = builder.ins().iconst(self.pointer_type, 0);
  + let zero = builder.ins().iconst(self.module.isa().pointer_type(), 0);
  builder.ins().return_(&[zero]);
  builder.finalize();
  