Revert "[InstCombine] Drop debug loc in TryToSinkInstruction (reland)"

This reverts commit 9649c20. See
discussion on the llvm-commits thread: if it's OK to preserve the
location when sinking a call, it's probably OK to always preserve the
location.

Author: vedantk

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -3356,12 +3356,6 @@ static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
   I->moveBefore(&*InsertPos);
   ++NumSunkInst;
 
-  // Drop the debug loc of non-inlinable instructions. This prevents
-  // single-stepping from going backwards. See HowToUpdateDebugInfo.rst for
-  // the full rationale.
-  if (!isa<CallBase>(I))
-    I->setDebugLoc(DebugLoc());
-
   // Also sink all related debug uses from the source basic block. Otherwise we
   // get debug use before the def. Attempt to salvage debug uses first, to
   // maximise the range variables have location for. If we cannot salvage, then