[clang] [llvm] [Hexagon] Add XQFloat code generation and post-RA QFP handling (PR #198902)

[Santanu Das via cfe-commits]

https://github.com/quic-santdas commented:

For each of the modes in xqfgenerator pass (lossy, ieee,etc.) opcodes of the latest ISA need to be added too. This pass was targetting v79 after which a few new qf opcodes were added.

Some classes like the one triggered by EnablePostRAXqfCompliance in postRA pass (a verifier if there are some incorrect/missing transformations. It is not necessary for the functionality, but acts more like a debugger) and EnableConversionsRemoval in XQFgenerator (removal of extra conversions) can probably be removed from the scope of the patch. The latter is also not turned on by default.

https://github.com/llvm/llvm-project/pull/198902