Getting "adding a plonk constraint with qM set but xa or xb == 0 (wire 0)" . Should I be worried?

[Scratch-net]

I was testing the new version of my circuit and this message popped up. Is this smth I should debug and fix?
This happened when I called api.Xor() which I do a lot in my code
Log is as follows:

=== RUN   TestCipher/bn254/plonk
21:43:51 INF compiling circuit
21:43:51 INF parsed circuit inputs nbPublic=1056 nbSecret=352
21:43:51 WRN adding a plonk constraint with qM set but xa or xb == 0 (wire 0)
21:43:51 INF building constraint builder nbConstraints=45351

[ivokub]

I was testing the new version of my circuit and this message popped up. Is this smth I should debug and fix? This happened when I called api.Xor() which I do a lot in my code Log is as follows:

=== RUN   TestCipher/bn254/plonk
21:43:51 INF compiling circuit
21:43:51 INF parsed circuit inputs nbPublic=1056 nbSecret=352
21:43:51 WRN adding a plonk constraint with qM set but xa or xb == 0 (wire 0)
21:43:51 INF building constraint builder nbConstraints=45351

Hi, you shouldn't be concerned about the warning, gnark is currently being overly sceptical.

The issue is that in some cases we can deduce that some variable is 0 a la:

...
y := api.Sub(x, x)
z := api.Mul(w, y)
...

where y is always 0 and thus also z is always zero. This warning indicates that in the call to api.Mul we have an input which is always 0 and can be optimized out.

Currently we have taken a conservative approach in gnark and do not automatically omit such constraints, so it is left up to the user.

[Scratch-net]

Ok cool, thanks