[NFC] Cleanup: Replace BB->InstList.splice() with BB->splice()

[vporpo]

Summary

This helps funnel ilist splice() calls into BasicBlock::splice().

llvm/lib/IR/BasicBlock.cpp

BasicBlock *BasicBlock::splitBasicBlock(iterator I, const Twine &BBName,
 
   BasicBlock *New = BasicBlock::Create(getContext(), BBName, getParent(),
                                        this->getNextNode());
 
   // Save DebugLoc of split point before invalidating iterator.
   DebugLoc Loc = I->getDebugLoc();
   // Move all of the specified instructions from the original basic block into
   // the new basic block.
-  New->getInstList().splice(New->end(), this->getInstList(), I, end());
+  New->splice(New->end(), this, I, end());
 
   // Add a branch instruction to the newly formed basic block.
   BranchInst *BI = BranchInst::Create(New, this);
   BI->setDebugLoc(Loc);
 
   // Now we must loop through all of the successors of the New block (which
   // _were_ the successors of the 'this' block), and update any PHI nodes in
   // successors.  If there were PHI nodes in the successors, then they need to
BasicBlock *BasicBlock::splitBasicBlockBefore(iterator I, const Twine &BBName) {
   assert((!isa<PHINode>(*I) || getSinglePredecessor()) &&
          "cannot split on multi incoming phis");
 
   BasicBlock *New = BasicBlock::Create(getContext(), BBName, getParent(), this);
   // Save DebugLoc of split point before invalidating iterator.
   DebugLoc Loc = I->getDebugLoc();
   // Move all of the specified instructions from the original basic block into
   // the new basic block.
-  New->getInstList().splice(New->end(), this->getInstList(), begin(), I);
+  New->splice(New->end(), this, begin(), I);
 
   // Loop through all of the predecessors of the 'this' block (which will be the
   // predecessors of the New block), replace the specified successor 'this'
   // block to point at the New block and update any PHI nodes in 'this' block.
   // If there were PHI nodes in 'this' block, the PHI nodes are updated
   // to reflect that the incoming branches will be from the New block and not
   // from predecessors of the 'this' block.
   // Save predecessors to separate vector before modifying them.