Annotate outer AES functions with target_feature

This seems to fix the build failures we were experiencing here:

rust-lang/rust#112709

Author: tarcieri

aes/src/armv8.rs

@@ -223,7 +223,7 @@ macro_rules! define_aes_impl {
         impl From<&$name_enc> for $name_dec {
             fn from(enc: &$name_enc) -> $name_dec {
                 let mut round_keys = enc.round_keys;
-                inv_expanded_keys(&mut round_keys);
+                unsafe { inv_expanded_keys(&mut round_keys) };
                 Self { round_keys }
             }
         }

aes/src/armv8/expand.rs

@@ -41,9 +41,9 @@ pub(super) fn expand_key<const L: usize, const N: usize>(key: &[u8; L]) -> [uint
         let mut word = ek_words[i - 1];
 
         if i % nk == 0 {
-            word = sub_word(word).rotate_right(8) ^ ROUND_CONSTS[i / nk - 1];
+            word = unsafe { sub_word(word) }.rotate_right(8) ^ ROUND_CONSTS[i / nk - 1];
         } else if nk > 6 && i % nk == 4 {
-            word = sub_word(word)
+            word = unsafe { sub_word(word) };
         }
 
         ek_words[i] = ek_words[i - nk] ^ word;
@@ -56,8 +56,9 @@ pub(super) fn expand_key<const L: usize, const N: usize>(key: &[u8; L]) -> [uint
 ///
 /// This is the reverse of the encryption keys, with the Inverse Mix Columns
 /// operation applied to all but the first and last expanded key.
-#[inline]
-pub(super) fn inv_expanded_keys<const N: usize>(expanded_keys: &mut [uint8x16_t; N]) {
+#[target_feature(enable = "aes")]
+#[target_feature(enable = "neon")]
+pub(super) unsafe fn inv_expanded_keys<const N: usize>(expanded_keys: &mut [uint8x16_t; N]) {
     assert!(N == 11 || N == 13 || N == 15);
 
     for ek in expanded_keys.iter_mut().take(N - 1).skip(1) {
@@ -68,14 +69,13 @@ pub(super) fn inv_expanded_keys<const N: usize>(expanded_keys: &mut [uint8x16_t;
 }
 
 /// Sub bytes for a single AES word: used for key expansion.
-#[inline(always)]
-fn sub_word(input: u32) -> u32 {
-    unsafe {
-        let input = vreinterpretq_u8_u32(vdupq_n_u32(input));
+#[target_feature(enable = "aes")]
+#[target_feature(enable = "neon")]
+unsafe fn sub_word(input: u32) -> u32 {
+    let input = vreinterpretq_u8_u32(vdupq_n_u32(input));
 
-        // AES single round encryption (with a "round" key of all zeros)
-        let sub_input = vaeseq_u8(input, vdupq_n_u8(0));
+    // AES single round encryption (with a "round" key of all zeros)
+    let sub_input = vaeseq_u8(input, vdupq_n_u8(0));
 
-        vgetq_lane_u32(vreinterpretq_u32_u8(sub_input), 0)
-    }
+    vgetq_lane_u32(vreinterpretq_u32_u8(sub_input), 0)
 }

aes/src/armv8/test_expand.rs

@@ -113,7 +113,7 @@ fn aes128_key_expansion() {
 #[test]
 fn aes128_key_expansion_inv() {
     let mut ek = load_expanded_keys(AES128_EXP_KEYS);
-    inv_expanded_keys(&mut ek);
+    unsafe { inv_expanded_keys(&mut ek) };
     assert_eq!(store_expanded_keys(ek), AES128_EXP_INVKEYS);
 }