[llvm] [PowerPC] Add intrinsics and tests for basic Dense Math enablement instructions (PR #129913)

[via llvm-commits]

RolandF77 wrote:

> Does it make sense to rename these instructions based on the latest RFC in this patch, since it adds the intrinsic for them, or should we do that in a separate patch, as it would require updating more places?

It should be done in a separate patch. Yes, there would be updates required to other places. But also no this patch does not introduce an intrinsic for dmxxextfdmr512. That instruction just appears in a test case, where it was introduced indirectly by using a store.

https://github.com/llvm/llvm-project/pull/129913