MC CFG: Split MCBasicBlocks to mirror atom splitting.

When an MCTextAtom is split, all MCBasicBlocks backed by it are
automatically split, with a fallthrough between both blocks, and
the successors moved to the second block.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188881 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCAtom.cpp

@@ -106,5 +106,6 @@ MCTextAtom *MCTextAtom::split(uint64_t SplitPt) {
 
   std::copy(I, Insts.end(), std::back_inserter(RightAtom->Insts));
   Insts.erase(I, Insts.end());
+  Parent->splitBasicBlocksForAtom(this, RightAtom);
   return RightAtom;
 }