Unlimited SWAP and DUP instructions

[axic]

No description provided.

[axic]

Alternatively to ease verification, the parameter to SWAPn / DUPn could be:

• force that a PUSH is present before them
• have an immediate value (2 bytes, to accommodate the value 1024) instead of a PUSH

[axic]

To clarify, the "immediate value" option would mean an encoding 0xb0 0xNN 0xNN for DUP and 0bx1 0xNN 0xNN for SWAP, just like how PUSH works.

[axic]

Sorry haven't seen the issue #174 which proposes the same.

[gcolvin]

I still think that if #615 is accepted this will be unnecessary.

[pirapira]

When a stack underflow exception is issued, what should happen to the contract execution? Would it be equivalent to REVERT with a certain output?

Does it ever happen that the stack depth is still at the limit after popping n?

[pirapira]

The cost can be smaller than 6 per operation. In fact the cost can be very close to 3. For example,

PUSH1 0
PUSH1 0
DUPn
DUPn
DUPn
DUPn
DUPn
DUPn
DUPn
...

[Arachnid]

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[axic]

Updated to satisfy draft requirements.

[MrChico]

It seems a lot easier to do stack analysis if the would be arguments inlined in the code, rather than taken off the stack. That would also play better with #615 .

[axic]

It seems a lot easier to do stack analysis if the would be arguments inlined in the code, rather than taken off the stack.

This option was also proposed, see #663 (comment) and #663 (comment).

Changed the EIP to explicitly list both options (in #2038).

[axic]

Added discussion URL: https://ethereum-magicians.org/t/eip-663-unlimited-swap-and-dup-instructions/3346