[clang] [llvm] [ARM] Armv8-R does not require fp64 or neon. (PR #88287)

[David Green via cfe-commits]

davemgreen wrote:

> which change? Specifying -mcpu=cortex-r52 will behave the same way as before. The original manual for the R52 provided for a no-neon sp-only variant, and they exist in the wild, and this lets "architecture-generic" builds automatically support both.

I just meant the break in functionality for existing users of -march=armv8r, and the drop in performance from less R52 tuning features/scheduling and the lack of Neon. I believe this is more correct, but users in the past could still get the same results by specifying `-march=armv8r -mfpu=fpv5-sp-d16`. I'm hoping someone else can come along and have an opinion on it one way or another.

https://github.com/llvm/llvm-project/pull/88287