[CodeGen] Use std::nullopt instead of None (NFC)

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

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
index 66f0eb83e57c..b46fc43e3497 100644
--- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -98,7 +98,7 @@ static Optional<DestSourcePair> isCopyInstr(const MachineInstr &MI,
     return Optional<DestSourcePair>(
         DestSourcePair{MI.getOperand(0), MI.getOperand(1)});
 
-  return None;
+  return std::nullopt;
 }
 
 class CopyTracker {