Code cleanups following up on #65576.

This makes a few code cleanups to follow up on the review comments in
#65576.

src/librustc_codegen_ssa/base.rs

@@ -406,6 +406,8 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(cx: &'
         rust_main_def_id: DefId,
         use_start_lang_item: bool,
     ) {
+        // The entry function is either `int main(void)` or `int main(int argc, char **argv)`,
+        // depending on whether the target needs `argc` and `argv` to be passed in.
         let llfty = if cx.sess().target.target.options.main_needs_argc_argv {
             cx.type_func(&[cx.type_int(), cx.type_ptr_to(cx.type_i8p())], cx.type_int())
         } else {
@@ -440,19 +442,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(cx: &'
 
         bx.insert_reference_to_gdb_debug_scripts_section_global();
 
-        let (arg_argc, arg_argv) = if cx.sess().target.target.options.main_needs_argc_argv {
-            // Params from native main() used as args for rust start function
-            let param_argc = bx.get_param(0);
-            let param_argv = bx.get_param(1);
-            let arg_argc = bx.intcast(param_argc, cx.type_isize(), true);
-            let arg_argv = param_argv;
-            (arg_argc, arg_argv)
-        } else {
-            // The Rust start function doesn't need argc and argv, so just pass zeros.
-            let arg_argc = bx.const_int(cx.type_int(), 0);
-            let arg_argv = bx.const_null(cx.type_ptr_to(cx.type_i8p()));
-            (arg_argc, arg_argv)
-        };
+        let (arg_argc, arg_argv) = get_argc_argv(cx, &mut bx);
 
         let (start_fn, args) = if use_start_lang_item {
             let start_def_id = cx.tcx().require_lang_item(StartFnLangItem, None);
@@ -477,6 +467,27 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(cx: &'
     }
 }
 
+/// Obtain the `argc` and `argv` values to pass to the rust start function.
+fn get_argc_argv<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
+    cx: &'a Bx::CodegenCx,
+    bx: &mut Bx
+) -> (Bx::Value, Bx::Value)
+{
+    if cx.sess().target.target.options.main_needs_argc_argv {
+        // Params from native `main()` used as args for rust start function
+        let param_argc = bx.get_param(0);
+        let param_argv = bx.get_param(1);
+        let arg_argc = bx.intcast(param_argc, cx.type_isize(), true);
+        let arg_argv = param_argv;
+        (arg_argc, arg_argv)
+    } else {
+        // The Rust start function doesn't need `argc` and `argv`, so just pass zeros.
+        let arg_argc = bx.const_int(cx.type_int(), 0);
+        let arg_argv = bx.const_null(cx.type_ptr_to(cx.type_i8p()));
+        (arg_argc, arg_argv)
+    }
+}
+
 pub const CODEGEN_WORKER_ID: usize = ::std::usize::MAX;
 
 pub fn codegen_crate<B: ExtraBackendMethods>(