[Instruction] Add missing implementation for moveAfter(InstListType::iterator) (#143093)

Commit 8e70273 introduced a declaration
for `Instruction::moveAfter(InstListType::iterator)`. However, its
implementation is missing. This PR adds it.

Author: kammt

llvm/lib/IR/Instruction.cpp

@@ -191,15 +191,22 @@ void Instruction::moveBeforePreserving(BasicBlock::iterator MovePos) {
 
 void Instruction::moveAfter(Instruction *MovePos) {
   auto NextIt = std::next(MovePos->getIterator());
-  // We want this instruction to be moved to before NextIt in the instruction
+  // We want this instruction to be moved to after NextIt in the instruction
   // list, but before NextIt's debug value range.
   NextIt.setHeadBit(true);
   moveBeforeImpl(*MovePos->getParent(), NextIt, false);
 }
 
+void Instruction::moveAfter(InstListType::iterator MovePos) {
+  // We want this instruction to be moved to after NextIt in the instruction
+  // list, but before NextIt's debug value range.
+  MovePos.setHeadBit(true);
+  moveBeforeImpl(*MovePos->getParent(), MovePos, false);
+}
+
 void Instruction::moveAfterPreserving(Instruction *MovePos) {
   auto NextIt = std::next(MovePos->getIterator());
-  // We want this instruction and its debug range to be moved to before NextIt
+  // We want this instruction and its debug range to be moved to after NextIt
   // in the instruction list, but before NextIt's debug value range.
   NextIt.setHeadBit(true);
   moveBeforeImpl(*MovePos->getParent(), NextIt, true);