64bit arithmetic op codes

[Christewart]

This BIP describes a soft fork to add 64-bit arithmetic op codes to bitcoin

Implementation: bitcoin/bitcoin#29221

[EthanHeilman]

Why not push the overflow amount and the result back on the stack?

Rather than $2^{64}-1 + 3 = \mbox{FALSE}$, do $2^{64}-1 + 3 = 2, 1$. Where $2 = 2^{64}-1 + 3 \mod 2^{64}$ is the result and 1 is the overflow.

This would simply doing 256-bit math from 64-bit stack elements and I don't see any downsides for 64-bit operations.

[Christewart]

Why not push the overflow amount and the result back on the stack?

Rather than 264−1+3=FALSE, do 264−1+3=2,1. Where 2=264−1+3mod264 is the result and 1 is the overflow.

This would simply doing 256-bit math from 64-bit stack elements and I don't see any downsides for 64-bit operations.

Sorry I don't understand this. Could you maybe give a more concrete example, perhaps on delvingbitcoin? We have a thread going here: https://delvingbitcoin.org/t/64-bit-arithmetic-soft-fork/397/25

[murchandamus]

I just did a light first pass. I noticed that this document may be missing a Rationale Section that describes design decisions, alternate approaches, and related work, and a Backwards Compatibility section.

You may want to add the "Post-History" header to the preamble to link to discussions of this proposal on the mailing list or forums.

[murchandamus]

Please refrain from issuing your own BIP numbers.

[murchandamus]

Maybe:

Suggested change

	Title: 64 bit arithmetic operations
	Title: 64-bit arithmetic operations