[NFC][LICM] Minor improvements to debug output

[xiaoqing_wu]

Summary

Added a utility function in Value class to print block name and use block labels for unnamed blocks.
Changed LICM to call this function in its debug output.

[xiaoqing_wu]

Remve "\ No newline at end of file" at the end of the file.

[xiaoqing_wu]

Remove trailing space

[asbirlea]

This seems like a useful utility to add to BasicBlock itself if it doesn't exit? (e.g. getNonEmptyName or getNameOrAsOperand).

[xiaoqing_wu]

Created a utility function in Value class to print block name and use block labels for unnamed blocks. Thanks Alina for the suggestion.

[asbirlea]

Thanks!

llvm/include/llvm/IR/Value.h

public:
 
   /// Transfer the name from V to this value.
   ///
   /// After taking V's name, sets V's name to empty.
   ///
   /// \note It is an error to call V->takeName(V).
   void takeName(Value *V);
 
+#ifndef NDEBUG
+  std::string getNameOrAsOperand() const;
+#endif
+
   /// Change all uses of this to point to a new Value.
   ///
   /// Go through the uses list for this definition and make each use point to
   /// "V" instead of "this".  After this completes, 'this's use list is
   /// guaranteed to be empty.
   void replaceAllUsesWith(Value *V);
 
   /// Change non-metadata uses of this to point to a new Value.

llvm/lib/IR/Value.cpp

void Value::takeName(Value *V) {
   setValueName(V->getValueName());
   V->setValueName(nullptr);
   getValueName()->setValue(this);
 
   if (ST)
     ST->reinsertValue(this);
 }
 
+#ifndef NDEBUG
+std::string Value::getNameOrAsOperand() const {
+  if (!getName().empty())
+    return std::string(getName());
+
+  std::string BBName;
+  raw_string_ostream OS(BBName);
+  printAsOperand(OS, false);
+  return OS.str();
+}
+#endif
+
 void Value::assertModuleIsMaterializedImpl() const {
 #ifndef NDEBUG
   const GlobalValue *GV = dyn_cast<GlobalValue>(this);
   if (!GV)
     return;
   const Module *M = GV->getParent();
   if (!M)
     return;

llvm/lib/Transforms/Scalar/LICM.cpp

LegacyLICMPass(
       : LoopPass(ID), LICM(LicmMssaOptCap, LicmMssaNoAccForPromotionCap) {
     initializeLegacyLICMPassPass(*PassRegistry::getPassRegistry());
   }
 
   bool runOnLoop(Loop *L, LPPassManager &LPM) override {
     if (skipLoop(L))
       return false;
 
+    LLVM_DEBUG(dbgs() << "Perform LICM on Loop with header at block "
+                      << L->getHeader()->getNameOrAsOperand() << "\n");
+
     auto *SE = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
     MemorySSA *MSSA = EnableMSSALoopDependency
                           ? (&getAnalysis<MemorySSAWrapperPass>().getMSSA())
                           : nullptr;
     bool hasProfileData = L->getHeader()->getParent()->hasProfileData();
     BlockFrequencyInfo *BFI =
         hasProfileData ? &getAnalysis<LazyBlockFrequencyInfoPass>().getBFI()
                        : nullptr;
auto HasBBAsSuccessor =
           return BB != Pair.second && (Pair.first->getSuccessor(0) == BB ||
                                        Pair.first->getSuccessor(1) == BB);
         };
     auto It = llvm::find_if(HoistableBranches, HasBBAsSuccessor);
 
     // If not involved in a pending branch, hoist to preheader
     BasicBlock *InitialPreheader = CurLoop->getLoopPreheader();
     if (It == HoistableBranches.end()) {
-      LLVM_DEBUG(dbgs() << "LICM using " << InitialPreheader->getName()
-                        << " as hoist destination for " << BB->getName()
-                        << "\n");
+      LLVM_DEBUG(dbgs() << "LICM using "
+                        << InitialPreheader->getNameOrAsOperand()
+                        << " as hoist destination for "
+                        << BB->getNameOrAsOperand() << "\n");
       HoistDestinationMap[BB] = InitialPreheader;
       return InitialPreheader;
     }
     BranchInst *BI = It->first;
     assert(std::find_if(++It, HoistableBranches.end(), HasBBAsSuccessor) ==
                HoistableBranches.end() &&
            "BB is expected to be the target of at most one branch");
 
for (Instruction *I : reverse(HoistedInstructions)) {
             DT->getNode(I->getParent())->getIDom()->getBlock();
         if (!HoistPoint || !DT->dominates(HoistPoint->getParent(), Dominator)) {
           if (HoistPoint)
             assert(DT->dominates(Dominator, HoistPoint->getParent()) &&
                    "New hoist point expected to dominate old hoist point");
           HoistPoint = Dominator->getTerminator();
         }
         LLVM_DEBUG(dbgs() << "LICM rehoisting to "
-                          << HoistPoint->getParent()->getName()
+                          << HoistPoint->getParent()->getNameOrAsOperand()
                           << ": " << *I << "\n");
         moveInstructionBefore(*I, *HoistPoint, *SafetyInfo, MSSAU, SE);
         HoistPoint = I;
         Changed = true;
       }
     }
   }
   if (MSSAU && VerifyMemorySSA)

 
 /// When an instruction is found to only use loop invariant operands that
 /// is safe to hoist, this instruction is called to do the dirty work.
 ///
 static void hoist(Instruction &I, const DominatorTree *DT, const Loop *CurLoop,
                   BasicBlock *Dest, ICFLoopSafetyInfo *SafetyInfo,
                   MemorySSAUpdater *MSSAU, ScalarEvolution *SE,
                   OptimizationRemarkEmitter *ORE) {
-  LLVM_DEBUG(dbgs() << "LICM hoisting to " << Dest->getName() << ": " << I
-                    << "\n");
+  LLVM_DEBUG(dbgs() << "LICM hoisting to " << Dest->getNameOrAsOperand() << ": "
+                    << I << "\n");
   ORE->emit([&]() {
     return OptimizationRemark(DEBUG_TYPE, "Hoisted", &I) << "hoisting "
                                                          << ore::NV("Inst", &I);
   });
 
   // Metadata can be dependent on conditions we are hoisting above.
   // Conservatively strip all metadata on the instruction unless we were
   // guaranteed to execute I if we entered the loop, in which case the metadata