Emit PUSH0 as junk in evm code transform, if available. #14133
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axic
reviewed
Apr 17, 2023
| if (m_assembly.evmVersion().hasPush0()) | ||
| m_assembly.appendConstant(0); | ||
| else | ||
| m_assembly.appendInstruction(evmasm::Instruction::CODESIZE); |
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I wonder if PC would have been nicer, given that is never used, and such is easier to detect at runtime (in case of a bug).
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Well, maybe, I won't change it here, though, in any case :-).
ekpyron
commented
Apr 17, 2023
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| if (m_assembly.evmVersion().hasPush0()) | ||
| m_assembly.appendConstant(0); | ||
| else | ||
| m_assembly.appendInstruction(evmasm::Instruction::CODESIZE); |
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As the comment says: we can push anything here - the reason why we used CODESIZE was that it's only 1 byte and 2 gas (whereas a PUSH1 0 was 2 bytes and 3 gas) - if we have PUSH0 (which is also 1 byte and 2 gas), that's definitely the nicer choice.
axic
reviewed
Apr 17, 2023
I'd have said this falls under the entry of #14107 |
ekpyron
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Added an explicit changelog entry now in any case. |
axic
approved these changes
Apr 17, 2023
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Part of #14073
Changes the code transform towards producing a less-weird
PUSH0instead ofCODESIZE- this doesn't make much of a difference other than aesthetics (codesizeoccurring in these cases was a bit weird).