RISC-V Bitmanip and Scalar Cryptographic extensions support

[edubart]

Context

The RISC-V Bitmanip extension provides new instructions that are able to perform complex bit manipulations using a single instruction. This could improve performance of cryptographic routines or really any application that performs bit manipulations compiled with the recent GCC 12.

Furthermore the RISC-V Scalar Cryptographic extension (that depends on a subset of Bitmanip), have specialized instructions that are able to accelerate AES, SHA256, SHA512, and other cryptographic routines inside the virtual machine. These instructions are being used already by the OpenSSL library and other crypto libraries.

If there is demand for faster cryptographic routines we could add support for these instructions in our emulator, however before even thinking on this, we should first solve #48 , because the amount of new instruction will put pressure in our current instruction decoder, which is already quite heavy under interpret.

Possible solutions

We should read the specs, and try to implement first a subset of instruction that makes sense for any demanding use case, while adding many tests.