[GISelValueTracking] Add test case for G_PTRTOINT
While we can only reason about the index/address, the G_PTRTOINT
operations returns all representation bits, so we can't assume the
remaining ones are all zeroes. This behaviour was clarified as part of
the discussion in https://discourse.llvm.org/t/clarifiying-the-semantics-of-ptrtoint/83987/54.
The LangRef semantics of ptrtoint being a full representation bitcast
were documented in https://github.com/llvm/llvm-project/pull/139349.
Prior to 77c8d214131e951e3d3a07b45a7436f54988d6f3 we were incorrectly
assuming known zeroes beyond the index size even if the input was
completely unknown. This commit adds a test case for G_PTRTOINT which
was omitted from that change.
See https://github.com/llvm/llvm-project/issues/139598
Reviewed By: arsenm
Pull Request: https://github.com/llvm/llvm-project/pull/139608
