aes/src/soft/fixslice64.rs appears to have been copied over with the contents of aes/src/soft/fixslice32.rs in commit https://github.com/RustCrypto/block-ciphers/commit/61cd5de91ba2cccd698e6a75d14eaa344d83cd0b.
aes/src/soft/fixslice64.rs appears to have been copied over with the contents of aes/src/soft/fixslice32.rs in commit 61cd5de.