This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.
This is part of an effort to migrate from llvm::Optional to
std::optional:
https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716
This patch adds a utility class that will be used in subsequent patches
for parsing the function/callsite attributes and determining whether
changes to PSTATE.SM are needed, or whether a lazy-save mechanism is
required.
It also implements some of the restrictions on the SME attributes
in the IR Verifier pass.
More details about the SME attributes and design can be found
in D131562.
Reviewed By: david-arm, aemerson
Differential Revision: https://reviews.llvm.org/D131570
