[clang] [clang] [ARM] Explicitly enable NEON for Windows/Darwin targets (PR #122095)

[Martin Storsjö via cfe-commits]

mstorsjo wrote:

> > In practice, when compiling C for Windows/ARMv7, NEON actually still is available, but not when compiling assembly files.
> 
> So the "bug" if we're going to call it that, is that C code can produce Neon but assembly files compiled in the same way cannot use Neon instructions?
> 
> Or has it always worked for C and assembly, and this only changes how the Neon feature is communicated?

With upstream Clang, both C and assembly files can use Neon, for both Windows/armv7 and iOS/armv7 targets. With the Debian/Ubuntu patched Clang, Neon only works in C, for Windows/armv7, but not in assembly and not for iOS/armv7 in either form.

https://github.com/llvm/llvm-project/pull/122095