This adds named ASI tag constants (such as #ASI_P and #ASI_P_L) for memory accesses. This patch adds 64-bit/V9 tag names, given that currently the majority of SPARC software targets that arch. Support for 32-bit/V8 tag names will be added in a future patch. Reviewed By: barannikov88 Differential Revision: https://reviews.llvm.org/D157235