[clang] [llvm] [ARM] enable FENV_ACCESS pragma support for hard-float targets (PR #137101)

[Erik Enikeev via llvm-commits]

Varnike wrote:

> Can we add a new register for just those bits, like FPSCR_NZCV. FPSCR_RM would alias with FPSCR but not FPSCR_NZCV.

Thanks for the comment! I took this approach and it seems that everything works with it.

I managed to split the patch into 4 parts that can be tested independently:

- #160696

- #160698

- #160699

- commit 06f4aea from this pr which enables strict fp support by setting HasStrictFP = true. It can only be applied after the previous patches have been committed. Would it be preferable to leave this as a single commit in the current PR, or to move it into a separate new one?

However, this split leaves three tests, added by analogy with AArch64, that I haven’t yet included in any patch. One of them ([strict-fp-ops.ll](https://github.com/llvm/llvm-project/blob/700169d93e593001731d7e2b92a60c09e161f520/llvm/test/CodeGen/ARM/strict-fp-ops.ll)) depends on both patches, which I still wanted to keep separate for review convenience. The other two ([strict-fp-int-promote.ll](https://github.com/llvm/llvm-project/blob/700169d93e593001731d7e2b92a60c09e161f520/llvm/test/CodeGen/ARM/strict-fp-int-promote.ll), [strictfp_f16_abi_promote.ll](https://github.com/llvm/llvm-project/blob/700169d93e593001731d7e2b92a60c09e161f520/llvm/test/CodeGen/ARM/strictfp_f16_abi_promote.ll)) are already supported correctly without my changes. Perhaps it would be better to add them after the other patches have been committed to LLVM? If this approach is not appropriate and the tests should be included in the patches above, please let me know and I will update them.

https://github.com/llvm/llvm-project/pull/137101