[BasicBlockUtils] Add optional BBName argument, in line with BB:splitBasicBlock

[asbirlea]

lgtm with a nit: clang-format (some lines seem longer than 80)

[fhahn]

In D67521#1668482, @asbirlea wrote:

lgtm with a nit: clang-format (some lines seem longer than 80)

Done just before committing, thanks!

llvm/trunk/include/llvm/Transforms/Utils/BasicBlockUtils.h

BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To,
                       MemorySSAUpdater *MSSAU = nullptr);
 
 /// Split the specified block at the specified instruction - everything before
 /// SplitPt stays in Old and everything starting with SplitPt moves to a new
 /// block. The two blocks are joined by an unconditional branch and the loop
 /// info is updated.
 BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt,
                        DominatorTree *DT = nullptr, LoopInfo *LI = nullptr,
-                       MemorySSAUpdater *MSSAU = nullptr);
+                       MemorySSAUpdater *MSSAU = nullptr,
+                       const Twine &BBName = "");
 
 /// This method introduces at least one new basic block into the function and
 /// moves some of the predecessors of BB to be predecessors of the new block.
 /// The new predecessors are indicated by the Preds array. The new block is
 /// given a suffix of 'Suffix'. Returns new basic block to which predecessors
 /// from Preds are now pointing.
 ///
 /// If BB is a landingpad block then additional basicblock might be introduced.

llvm/trunk/lib/Transforms/Utils/BasicBlockUtils.cpp

if (TI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(TI))
         if (SplitCriticalEdge(TI, i, Options))
           ++NumBroken;
   }
   return NumBroken;
 }
 
 BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt,
                              DominatorTree *DT, LoopInfo *LI,
-                             MemorySSAUpdater *MSSAU) {
+                             MemorySSAUpdater *MSSAU, const Twine &BBName) {
   BasicBlock::iterator SplitIt = SplitPt->getIterator();
   while (isa<PHINode>(SplitIt) || SplitIt->isEHPad())
     ++SplitIt;
-  BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
+  std::string Name = BBName.str();
+  BasicBlock *New = Old->splitBasicBlock(
+      SplitIt, Name.empty() ? Old->getName() + ".split" : Name);
 
   // The new block lives in whichever loop the old one did. This preserves
   // LCSSA as well, because we force the split point to be after any PHI nodes.
   if (LI)
     if (Loop *L = LI->getLoopFor(Old))
       L->addBasicBlockToLoop(New, *LI);
 
   if (DT)

llvm/trunk/lib/Transforms/Utils/LoopVersioning.cpp

void LoopVersioning::versionLoop(
 
   // Rename the block to make the IR more readable.
   RuntimeCheckBB->setName(VersionedLoop->getHeader()->getName() +
                           ".lver.check");
 
   // Create empty preheader for the loop (and after cloning for the
   // non-versioned loop).
   BasicBlock *PH =
-      SplitBlock(RuntimeCheckBB, RuntimeCheckBB->getTerminator(), DT, LI);
-  PH->setName(VersionedLoop->getHeader()->getName() + ".ph");
+      SplitBlock(RuntimeCheckBB, RuntimeCheckBB->getTerminator(), DT, LI,
+                 nullptr, VersionedLoop->getHeader()->getName() + ".ph");
 
   // Clone the loop including the preheader.
   //
   // FIXME: This does not currently preserve SimplifyLoop because the exit
   // block is a join between the two loops.
   SmallVector<BasicBlock *, 8> NonVersionedLoopBlocks;
   NonVersionedLoop =
       cloneLoopWithPreheader(PH, RuntimeCheckBB, VersionedLoop, VMap,