Before this patch when running HWASAN on x86_64 with with memory tagging support we got a bunch of false memory leak reports. The reason for that is that the heuristic used to detect if an 8 bytes could be a user pointer was not valid when memory tagging is used as the top byte could contain non-zero information.
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D155338
