[SCEV] Move NoWrapFlags definition outside SCEV scope, use for SCEVUse. (#190199)
The patch moves out of SCEV's scope so they can be re-used for SCEVUse.
SCEVUse gets an additional getNoWrapFlags helper that returns the union
of the expressions SCEV flags and the use-specific flags.
SCEVExpander has been updated to use this new helper.
In order to avoid other changes, the original names are exposed via
constexpr in SCEV. Not sure if there's a nicer way. One alternative
would be to define the enum in struct, and have SCEV inherit from it.
The patch also clarifies that the SCEVUse flags encode NUW/NSW, and
hides getInt, setInt, etc to avoid potential mis-use.
PR: https://github.com/llvm/llvm-project/pull/190199