[llvm] r319679 - [SCEV] Use a "Discovered" set instead of a "Visited" set; NFC

[Sanjoy Das via llvm-commits]

Author: sanjoy
Date: Mon Dec  4 11:22:01 2017
New Revision: 319679

URL: http://llvm.org/viewvc/llvm-project?rev=319679&view=rev
Log:
[SCEV] Use a "Discovered" set instead of a "Visited" set; NFC

Suggested by Max Kazantsev in https://reviews.llvm.org/D39361

Modified:
    llvm/trunk/lib/Analysis/ScalarEvolution.cpp

Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=319679&r1=319678&r2=319679&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Mon Dec  4 11:22:01 2017
@@ -6414,11 +6414,9 @@ ScalarEvolution::getBackedgeTakenInfo(co
     SmallVector<Instruction *, 16> Worklist;
     PushLoopPHIs(L, Worklist);
 
-    SmallPtrSet<Instruction *, 8> Visited;
+    SmallPtrSet<Instruction *, 8> Discovered;
     while (!Worklist.empty()) {
       Instruction *I = Worklist.pop_back_val();
-      if (!Visited.insert(I).second)
-        continue;
 
       ValueExprMapType::iterator It =
         ValueExprMap.find_as(static_cast<Value *>(I));
@@ -6460,7 +6458,8 @@ ScalarEvolution::getBackedgeTakenInfo(co
       for (auto *U : I->users())
         if (auto *I = dyn_cast<Instruction>(U)) {
           auto *LoopForUser = LI.getLoopFor(I->getParent());
-          if (LoopForUser && L->contains(LoopForUser))
+          if (LoopForUser && L->contains(LoopForUser) &&
+              Discovered.insert(I).second)
             Worklist.push_back(I);
         }
     }