Three fixes:
1. When doing t[u0] +=1 if u0 is unbacked we could allocate a new unbacked symbol during the the indexing of t[u0] (when we fake trace setitem), namely because meta_select does allocate a new unbacked symbol for the storage offset when we do not know if u0>=0 or u0<0. but the output size/stride of setitem(), does not depend on that new symbol. it's self consumed in setitem so we shall ignore it.
2. Also when we trace through generalized_scatter the applications of the views could allocate unbacked symints
but those do not effect final output, we also shall ignore them.
3.Before accessing strides in lowering we shall materialize.
Address https://github.com/pytorch/pytorch/issues/114293 and https://github.com/pytorch/pytorch/issues/131911
Pull Request resolved: https://github.com/pytorch/pytorch/pull/164341
Approved by: https://github.com/bobrenjc93
c6a8db0b9a