Add more core stubs to minicore

`f32`, `f64` and `asm!` macro.

Author: jieyouxu

tests/auxiliary/minicore.rs

@@ -6,14 +6,16 @@
 //!
 //! - `minicore` is **only** intended for `core` items, and the stubs should match the actual `core`
 //!   items.
+//! - Avoid adding new features and things that are only available for a subset of targets, e.g.
+//!   `#[feature(asm_experimental_arch)]`.
 //!
 //! # References
 //!
 //! This is partially adapted from `rustc_codegen_cranelift`:
 //! <https://github.com/rust-lang/rust/blob/c0b5cc9003f6464c11ae1c0662c6a7e06f6f5cab/compiler/rustc_codegen_cranelift/example/mini_core.rs>.
 // ignore-tidy-linelength
 
-#![feature(no_core, lang_items, rustc_attrs)]
+#![feature(no_core, lang_items, rustc_attrs, decl_macro)]
 #![allow(unused, improper_ctypes_definitions, internal_features)]
 #![no_std]
 #![no_core]
@@ -37,7 +39,9 @@ impl<T: ?Sized> LegacyReceiver for &mut T {}
 #[lang = "copy"]
 pub trait Copy: Sized {}
 
-impl_marker_trait!(Copy => [ bool, char, isize, usize, i8, i16, i32, i64, u8, u16, u32, u64 ]);
+impl_marker_trait!(
+    Copy => [ bool, char, isize, usize, i8, i16, i32, i64, u8, u16, u32, u64, f32, f64 ]
+);
 impl<'a, T: ?Sized> Copy for &'a T {}
 impl<T: ?Sized> Copy for *const T {}
 impl<T: ?Sized> Copy for *mut T {}