This reverts commit 2501ae58e3bb9a70d279a56d7b3a0ed70a8a852c.

Reverted due to various buildbot failures.

PR #66334 tried to renumber slot indexes before register allocation, but
the numbering was still affected by list entries for instructions which
had been erased. Fix this to make the register allocator's live range
length heuristics even less dependent on the history of how instructions
have been added to and removed from SlotIndexes's maps.

Reviewed By: zixuan-wu

Differential Revision: https://reviews.llvm.org/D154768

These tests will be optimzied with BTSTI16/BTSTI32
in the future.

Reviewed By: zixuan-wu

Differential Revision: https://reviews.llvm.org/D154767

Reviewed By: zixuan-wu

Differential Revision: https://reviews.llvm.org/D154409

Reviewed By: zixuan-wu

Differential Revision: https://reviews.llvm.org/D154408

Normally, generic processor does not have any SubtargetFeature. And it
can just generate most basic instructions which have no Predicates to
guard.

But it needs to enbale predicate for the btsti16 instruction as one of the most basic instructions.
Or the generic processor can't finish codegen process. So Add FeatureBTST16 SubtargetFeature to generic ProcessorModel.

- Test cases for arch only has 16-bit instruction such as ck801/ck802 need
compile with -mattr=+btst16
- Fix the GPR copy instruction with MOV16 for 16-bit only arch.

In generic cpu model, there are only low 16 registers and little 32-bit instruction. CK801 is the cpu
family with least basic features like generic model.

Add test run and check for generic cpu model in original test case to cover basic LLVM IR functionality.