[llvm] [ARM] Consider denormal mode in `ARMSubtarget` (PR #160456)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

Thanks for this. Can you pull in the change from this bit of code too? It can use this denormal feature now?
```
  // NEON f32 ops are non-IEEE 754 compliant. Darwin is ok with it by default.
  const FeatureBitset &Bits = getFeatureBits();
  if ((Bits[ARM::ProcA5] || Bits[ARM::ProcA8]) && // Where this matters
      (Options.UnsafeFPMath || isTargetDarwin()))
```
And maybe update the test, I think there are a few that this triggers on.

https://github.com/llvm/llvm-project/pull/160456