[MemorySSA] Properly handle liveOnEntry in the walker printer

llvm/lib/Analysis/MemorySSA.cpp

 #else
 bool llvm::VerifyMemorySSA = false;
 #endif
 
 static cl::opt<bool, true>
     VerifyMemorySSAX("verify-memoryssa", cl::location(VerifyMemorySSA),
                      cl::Hidden, cl::desc("Enable verification of MemorySSA."));
 
+const static char LiveOnEntryStr[] = "liveOnEntry";
+
 namespace {
 
 /// An assembly annotator class to print Memory SSA information in
 /// comments.
 class MemorySSAAnnotatedWriter : public AssemblyAnnotationWriter {
   const MemorySSA *MSSA;
 
 public:
public:
   MemorySSAWalkerAnnotatedWriter(MemorySSA *M)
       : MSSA(M), Walker(M->getWalker()) {}
 
   void emitInstructionAnnot(const Instruction *I,
                             formatted_raw_ostream &OS) override {
     if (MemoryAccess *MA = MSSA->getMemoryAccess(I)) {
       MemoryAccess *Clobber = Walker->getClobberingMemoryAccess(MA);
       OS << "; " << *MA;
-      if (Clobber)
-        OS << " - clobbered by " << *Clobber;
+      if (Clobber) {
+        OS << " - clobbered by ";
+        if (MSSA->isLiveOnEntryDef(Clobber))
+          OS << LiveOnEntryStr;
+        else
+          OS << *Clobber;
+      }
       OS << "\n";
     }
   }
 };
 
 } // namespace
 
 namespace {
if (UseBB != Dominator->getBlock())
       return DT->dominates(Dominator->getBlock(), UseBB);
     // If the UseBB and the DefBB are the same, compare locally.
     return locallyDominates(Dominator, cast<MemoryAccess>(Dominatee));
   }
   // If it's not a PHI node use, the normal dominates can already handle it.
   return dominates(Dominator, cast<MemoryAccess>(Dominatee.getUser()));
 }
 
-const static char LiveOnEntryStr[] = "liveOnEntry";
-
 void MemoryAccess::print(raw_ostream &OS) const {
   switch (getValueID()) {
   case MemoryPhiVal: return static_cast<const MemoryPhi *>(this)->print(OS);
   case MemoryDefVal: return static_cast<const MemoryDef *>(this)->print(OS);
   case MemoryUseVal: return static_cast<const MemoryUse *>(this)->print(OS);
   }
   llvm_unreachable("invalid value id");
 }

llvm/test/Analysis/MemorySSA/print-walker.ll

 ; RUN: opt -passes='print<memoryssa-walker>' -disable-output < %s 2>&1 | FileCheck %s
 
 ; CHECK: define void @test
-; CHECK: 1 = MemoryDef(liveOnEntry)->liveOnEntry - clobbered by 0 = MemoryDef(liveOnEntry)
+; CHECK: 1 = MemoryDef(liveOnEntry)->liveOnEntry - clobbered by liveOnEntry
 ; CHECK: store i8 42, i8* %a1
-; CHECK: 2 = MemoryDef(1)->liveOnEntry - clobbered by 0 = MemoryDef(liveOnEntry)
+; CHECK: 2 = MemoryDef(1)->liveOnEntry - clobbered by liveOnEntry
 ; CHECK: store i8 42, i8* %a2
 ; CHECK: MemoryUse(1) MustAlias - clobbered by 1 = MemoryDef(liveOnEntry)->liveOnEntry
 ; CHECK: %l1 = load i8, i8* %a1
 ; CHECK: MemoryUse(2) MustAlias - clobbered by 2 = MemoryDef(1)->liveOnEntry
 ; CHECK: %l2 = load i8, i8* %a2
-; CHECK: 3 = MemoryDef(2)->liveOnEntry - clobbered by 0 = MemoryDef(liveOnEntry)
+; CHECK: 3 = MemoryDef(2)->liveOnEntry - clobbered by liveOnEntry
 ; CHECK: store i8 42, i8* %p
 ; CHECK: 4 = MemoryDef(3)->3 MustAlias - clobbered by 3 = MemoryDef(2)->liveOnEntry
 ; CHECK: store i8 42, i8* %p
 ; CHECK: MemoryUse(4) MustAlias - clobbered by 4 = MemoryDef(3)->3 MustAlias
 ; CHECK: %p1 = load i8, i8* %p
 ; CHECK: MemoryUse(4) MustAlias - clobbered by 4 = MemoryDef(3)->3 MustAlias
 ; CHECK: %p2 = load i8, i8* %p