This is required to bring CaptureTracking in line with the new
semantics from D154051, as gep inbounds p, 0 is now always non-poison.
There are many ways in which the inbounds special case could be
preserved: If the index is known non-zero, or there is an inbounds
chain down to an identified object, etc. However, I have opted to
drop the special case entirely, as it appears to be low value:
In cases where we can determine such things (e.g. the affected test
cases) we would end up removing the compare via isGEPKnownNonNull()
logic anyway.
Differential Revision: https://reviews.llvm.org/D154054
f3d0613d85