Add EIP: SLOT precompile

EIPS/eip-slot-precompile.md

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+---
+eip:
+title: SLOT precompile
+description: Precompile to get the current slot
+author: Marc Harvey-Hill (@Marchhill)
+discussions-to: 
+status: Draft
+type: Standards Track
+category: Core
+created: 2024-12-06
+---
+
+## Abstract
+
+This EIP proposes to add a new precompile that returns the corresponding slot for the current block.
+
+## Motivation
+
+It is currently possible to calculate the slot number from the block timestamp. However, this requires hardcoding the chain slot length into a smart contract. This would require the contract code to be changed in the event of a future change to slot length. A better approach is for the slot number to be calculated by the execution layer and exposed in a precompile.
+
+### Encrypted Mempools
+
+This precompile aims to improve support for encrypted mempools. In order to be secure, the validity of encrypted mempool transactions should be tied to the inclusion of all transactions by a proposer in the correct slot. This rule can be enforced by a smart contract using this precompile.
+
+## Specification
+
+If `block.number >= TBD` a new precompiled contract `SLOT` shall be created at address `TBD`.
+
+`SLOT` returns as output the current slot number as an 8 byte ulong in big endian encoding.
+
+### Gas Cost
+
+The gas cost for `SLOT` is a fixed fee of `2`
+
+## Rationale
+
+### Gas Price
+
+The precompile is priced to match similar opcodes in the `W_base` set.
+
+### Precompile
+
+Making the feature a precompile rather than an opcode gives L2s flexibility to decide whether to implement it.
+
+## Backwards Compatibility
+
+No backward compatibility issues found.
+
+## Test Cases
+
+N/A
+
+## Security Considerations
+
+<!-- TODO -->
+Needs discussion.
+
+## Copyright
+
+Copyright and related rights waived via [CC0](../LICENSE.md).