Add feature to use optimized intrinsics

The Rust core library provides unoptimized string copying routines,
which are much slower than the optimized assembly versions provided by
ARM. So wire this up as a cargo feature, and enable it by default.

Cargo.toml

@@ -14,6 +14,11 @@ spinning_top = "0.2.5"
 once_cell = { version = "1.18.0", default-features = false, features = ["alloc"]  }
 efiloader = "0.0.1"
 aarch64-paging = "0.5.0"
+aarch64-intrinsics = { version = "1.0.0", optional = true }
+
+[features]
+default = ["use_optimized_intrinsics"]
+use_optimized_intrinsics = ["dep:aarch64-intrinsics"]
 
 [profile.dev]
 panic = "abort"

src/main.rs

@@ -33,6 +33,9 @@ use log::{debug, error, info};
 extern crate alloc;
 use alloc::vec::Vec;
 
+#[cfg(feature = "use_optimized_intrinsics")]
+extern crate aarch64_intrinsics;
+
 use aarch64_paging::paging::Attributes;
 
 use efiloader::*;