[compiler-rt] [compiler-rt][ARM] Optimized single precision FP add/sub (PR #179929)

[Simon Tatham via llvm-commits]

statham-arm wrote:

Hi @compnerd, this is the last of my long stack of optimized FP implementations, ready for review!

Unlike all the previous ones (which is why I left it until last), this patch introduces an optimized assembler implementation of a function that already had one. (Thumb1 only; there was not already an optimized assembler Thumb2 faddsub.) I've kept the old version, and it's still selected if the new optimized-implementations flag is turned off. But the patch looks a bit weird because the old file used to live at a pathname that is now one of the new files. Sorry about that.

https://github.com/llvm/llvm-project/pull/179929