Feat: keccak256

[0xurb]

Quick resolve for KECCAK256 implementation related to #4

cargo run is passed correctly, but not too sure about this implementation

cc: @leonardoalt

[leonardoalt]

what does this do?

[0xurb]

• lateout - 256 bytes of keccak hash goes to 4 registers, it's like out("a0"), out("a1") ... etc. but marked "late" to tell that it only writes to the register after all inputs are read.

• nostack - tells the compiler this asm block doesn't use the stack.

• preserves_flags - means that asm! block does not modify the flags register

Saw nostack in other RISC-V adapters code, e.g this, but it is not necessary I think. Don't have any experience with asm!.

[leonardoalt]

yea I feel like the options are not needed here. I think we should remove it if it works without

[leonardoalt]

Sick! Please undraft

[leonardoalt]

Can be extracted into a function

[leonardoalt]

Let's start using EVM opcodes as syscall ids here

[0xurb]

@leonardoalt let's do on both PRs (for log also) with opcodes and then in a new PR/commit the rest

[leonardoalt]

It would also be good to replace the hardcoded ids here by the actual syscall names (in the match arms)

[0xurb]

Yes thanked about that too
Done it on Odyssey's draft

[0xurb]

@leonardoalt let's merge both syscalls with ids as regarded opcodes and then make a PR with this improvements:

• replace first five syscalls ids with a regarded opcodes
• replace the hardcoded ids(opcodes) on
  

  r55/r55/src/exec.rs

  Lines 154 to 155 in 587a485

  	let t0: u64 = emu.cpu.xregs.read(5);
  	match t0 {

  
  by the actual syscall names (from Syscall enum) with unhandled syscall opcode exception before matching (use Syscall ::try_from(opcode).unwrap_or_else(||...) instead of _ => {} match arm)
• extract

  r55/r55/src/exec.rs

  Lines 160 to 167 in 587a485

  	let data_bytes = if ret_size != 0 {
  	emu.cpu
  	.bus
  	.get_dram_slice(ret_offset..(ret_offset + ret_size))
  	.unwrap()
  	} else {
  	&mut []
  	};

  into a function

[leonardoalt]

@0xurb ok sounds good, if you could just remove the asm options and see if it works without, we could remove & merge

[0xurb]

@leonardoalt done, cargo r works for me