[llvm] [ARM] Stop gluing FP comparisons to FMSTAT (PR #116676)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

It looks like these instructions do not exist in ARM mode. At least when I fix the encoding issue, the resulting assembly file is not accepted by the assembler:
```
test.s:1:1: note: instruction requires: armv8.1m.main
vstr fpscr_nzcvqc, [sp, #4]
```

The encoding of this addressing mode is also broken, but I believe only in ARM mode.

NB
I'm not really familiar with ARM/Thumb modes, their cooperation, how they relate to processor models, which of them backward or forward compatible with which etc., so the above may be complete nonsense. I would love some help here.


https://github.com/llvm/llvm-project/pull/116676