aes: compilation errors on cg_clif due to lack of intrinsics support

[tarcieri]

See:

• Unimplemented intrinsic core_arch::x86::aes::_mm_aesdec_si128 rust-lang/rustc_codegen_cranelift#1409
• Unimplemented llvm intrinsics aesimc aesdec aesdeclast (used by aes and ring) rust-lang/rustc_codegen_cranelift#1410

Cranelift doesn't support these intrinsics yet, so compilation fails it inserts traps instead of using the intrinsics.

I've suggested cfg(aes_force_soft) as a workaround, but it would be nice if this just worked, and even better if hardware acceleration worked.

One option would be to use inline assembly, which would also provide an avenue to address #385.

[tarcieri]

cc @bjorn3

[newpavlov]

It's clearly a Cranelift issue and I don't think we should do anything to address it.

[AppleSheeple]

Cranelift doesn't support these intrinsics yet, so compilation fails.

For the sake of accuracy, missing intrinsics trigger warnings about traps used instead of unimplemented intrinsics. Compilation does not fail!

[tarcieri]

Looks like this will be addressed by rust-lang/rustc_codegen_cranelift#1425

Going to go ahead and close this.