This patch replaces uses of StringRef::{starts,ends}with with
StringRef::{starts,ends}_with for consistency with
std::{string,string_view}::{starts,ends}_with in C++20.
I'm planning to deprecate and eventually remove
StringRef::{starts,ends}with.
Add a new pass and conversions to emulate wide integer operations over memrefs.
The emulation is implemented on top of the existing pass to emulate wide integer arith ops.
Improve naming in the arith pass to avoid potential name clashes.
Reviewed By: antiagainst
Differential Revision: https://reviews.llvm.org/D135722
