[llvm] [TableGen][RISCV] Generate pre/post-RA statistics for macro fusions (PR #209394)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

> I think splitting statistics by pre-ra and post-ra is good, I hadn't thought of that.
> 
> I don't think we want two different compile-time controls of statistics. I'm not sure we even want one, but I understand the need. There is already `LLVM_ENABLE_STATS` which will swap out the Statistic implementation for one that no-ops (in a fully inlinable way). If we're going to keep one of them, let's not push users into making TableGen changes, because those have broad effects across the entire LLVM compile, rather than in just one `.cpp` file change.

I removed both `ENABLE_STATISTIC` and `bit GenerateStatistic`. And I added you as the co-author since it is more like your implementation now. :-)

https://github.com/llvm/llvm-project/pull/209394