FIP: Add Support for EIP-7939 (CLZ Opcode) in the FEVM #1230
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snissn
requested review from
TippyFlitsUK,
anorth,
dannyob,
jennijuju,
jsoares,
lanzafame,
momack2 and
rvagg
as code owners
Member
lanzafame
approved these changes
Feb 4, 2026
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|
My approval assumes the edits @rvagg has put forward. |
jsoares
approved these changes
Feb 11, 2026
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Abstract
This PR proposes implementing Ethereum’s EIP-7939 in the FEVM by introducing a new opcode,
CLZ(0x1e). The opcode pops one 256-bit stack wordxand pushes the number of leading zero bits inx(0–256). Ifx == 0, it pushes256. This change improves Ethereum compatibility (EIP-7939 is activated on Ethereum mainnet in the Fusaka upgrade) and enables cheaper and simpler implementations of common bit-operations in FEVM smart contracts.Discussion
Implementation
Notes
FIPS/fip-draft_eip-7939-clz.md(no number assigned; README row usesXXXX).