[NFC][AArch64] Split out backend features
This patch splits backend features currently
hidden behind architecture versions.
For example, currently the only way to activate
complex numbers extension is targeting an v8.3
architecture, where after the patch this extension
can be added separately.
This refactoring is required by the new command lines proposal:
Reviewers: DavidSpickett, olista01, t.p.northover
Subscribers: kristof.beyls, bryanpkc, javed.absar, pbarrio
Differential revision: https://reviews.llvm.org/D54633
It was reverted in rL348249 due a build bot failure in one of the
The problem seems to be that FileCheck behaves
different in windows and linux. This new patch
splits the test file in multiple,
and does more exact pattern matching attempting
to circumvent the issue.