[llvm] [X86] added computeKnownBits for X86ISD::GF2P8AFFINEQB (PR #194197)

[Kartik Ohlan via llvm-commits]

Ko496-glitch wrote:

> I'm not sure if its worth trying to do this for a non-constant Matrix operands tbh - I'd expect we should just use getTargetConstantBitsFromNode() and use that with the Input operand's known bits.

so do you suggest adding a break statement when matrix is runtime variable ? also shouldn't this be covered in test cases ? 

https://github.com/llvm/llvm-project/pull/194197