Compilation flag to add runtime checks for opcode assumptions

[michaeljklein]

Problem

Some ACIR opcodes have built-in assumptions about their inputs/outputs, e.g.

• Whether a point is on the curve and/or at infinity
• An input/output being within a range (if integral) or of a specific size (if array-like)
• Public key(s) are valid(?)

These assumptions are expected to be checked at some point throughout compilation, but

1. They're exclusively runtime checks
2. They're checked at different locations and/or passes
3. They could be checked earlier in compilation and then invalidated later, e.g. by an SSA pass

Happy Case

Add a compilation flag to generate runtime code to check such assumptions, perhaps --pedantic or --pedantic-gen

• This flag would only be used for testing, since it would be expected to have a negative impact on performance (and should be redundant)
• This would be especially useful for fuzzing, where otherwise assumptions can be broken silently

Workaround

Yes

Workaround Description

A partial workaround is to manually trace the dependencies of a piece of user code to their ACVM opcodes and add such runtime checks, however:

• This only works for individual and specific pieces of user code
• It would be challenging to keep up to date, especially without feature flags

Additional Context

No response

Project Impact

Nice-to-have

Blocker Context

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response

[Rumata888]

This would be really nice to protect us from shooting ourselves in the foot. If we implement fuzzing for noir programs, it would also have a benefit as an extended bug oracle. Would be great