feat(revm): revert EIP-2935 BLOCKHASH opcode changes

[shekhirin]

As per ethereum/EIPs#8577

Change explanation: #1450 (comment)

[github-actions]

Valgrind Results:

==3762== Cachegrind, a cache and branch-prediction profiler
==3762== Copyright (C) 2002-2017, and GNU GPL'd, by Nicholas Nethercote et al.
==3762== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==3762== Command: target/release/snailtracer
==3762== 
--3762-- warning: L3 cache found, using its data for the LL simulation.
Running snailtracer example!
elapsed: 1.827643523s
==3762== 
==3762== I   refs:      429,371,833
==3762== I1  misses:          3,118
==3762== LLi misses:          2,801
==3762== I1  miss rate:        0.00%
==3762== LLi miss rate:        0.00%
==3762== 
==3762== D   refs:      206,205,188  (133,650,687 rd   + 72,554,501 wr)
==3762== D1  misses:        344,946  (    204,870 rd   +    140,076 wr)
==3762== LLd misses:        137,605  (      4,255 rd   +    133,350 wr)
==3762== D1  miss rate:         0.2% (        0.2%     +        0.2%  )
==3762== LLd miss rate:         0.1% (        0.0%     +        0.2%  )
==3762== 
==3762== LL refs:           348,064  (    207,988 rd   +    140,076 wr)
==3762== LL misses:         140,406  (      7,056 rd   +    133,350 wr)
==3762== LL miss rate:          0.0% (        0.0%     +        0.2%  )

[DaniPopes]

only this PRAGUE branch should be removed, the rest is still valid (diff == 0, diff <= HISTORY...)

[shekhirin]

are you sure? from the EIP:

The BLOCKHASH opcode semantics remains the same as before.

revm/crates/revm/src/context.rs

Lines 108 to 113 in eed27d9

	fn block_hash(&mut self, number: U256) -> Option<B256> {
	self.evm
	.block_hash(number)
	.map_err(|e| self.evm.error = Err(e))
	.ok()
	}

[DaniPopes]

Yes, this is the before:

revm/crates/interpreter/src/instructions/host.rs

Lines 106 to 123 in 688c36c

	pub fn blockhash<H: Host + ?Sized>(interpreter: &mut Interpreter, host: &mut H) {
	gas!(interpreter, gas::BLOCKHASH);
	pop_top!(interpreter, number);
	if let Some(diff) = host.env().block.number.checked_sub(*number) {
	let diff = as_usize_saturated!(diff);
	// blockhash should push zero if number is same as current block number.
	if diff <= BLOCK_HASH_HISTORY && diff != 0 {
	let Some(hash) = host.block_hash(*number) else {
	interpreter.instruction_result = InstructionResult::FatalExternalError;
	return;
	};
	*number = U256::from_be_bytes(hash.0);
	return;
	}
	}
	*number = U256::ZERO;
	}

This implementation was moved from the blockhash instruction to the host implementation in #1427, and was refactored in #1430

[shekhirin]

oh, my bad, fixing

[rakita]

Logic can stay inside EvmContext, previously it was inside instruction.

This is old logic before EIP-2935:

revm/crates/interpreter/src/instructions/host.rs

Lines 127 to 139 in 1640b8f

	if let Some(diff) = host.env().block.number.checked_sub(*number) {
	let diff = as_usize_saturated!(diff);
	// blockhash should push zero if number is same as current block number.
	if diff <= BLOCK_HASH_HISTORY && diff != 0 {
	let Some(hash) = host.block_hash(*number) else {
	interpreter.instruction_result = InstructionResult::FatalExternalError;
	return;
	};
	*number = U256::from_be_bytes(hash.0);
	return;
	}
	}
	*number = U256::ZERO;

[rakita]

lgtm, clippy pending