0de16fafa5
This is part of an effort to migrate from llvm::Optional to std::optional. This patch touches DialectConversion, and modifies existing conversions and tests appropriately. See also: https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716 Signed-off-by: Ramkumar Ramachandra <r@artagnon.com> Differential Revision: https://reviews.llvm.org/D140303