2 files changed, 18 insertions, 10 deletions
diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index d1e57e101b..490617a0c8 100644
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -450,8 +450,10 @@ void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
   }
 
   // Add a new IVUsers entry for the newly-created integer PHI.
-  if (IU)
-    IU->AddUsersIfInteresting(NewPHI);
+  if (IU) {
+    SmallPtrSet<Loop*, 16> SimplifiedLoopNests;
+    IU->AddUsersIfInteresting(NewPHI, SimplifiedLoopNests);
+  }
 
   Changed = true;
 }
@@ -1967,8 +1969,11 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
   // loop exit test instruction.
   if (IU && NewICmp) {
     ICmpInst *NewICmpInst = dyn_cast<ICmpInst>(NewICmp);
-    if (NewICmpInst)
-      IU->AddUsersIfInteresting(cast<Instruction>(NewICmpInst->getOperand(0)));
+    if (NewICmpInst) {
+      SmallPtrSet<Loop*, 16> SimplifiedLoopNests;
+      IU->AddUsersIfInteresting(cast<Instruction>(NewICmpInst->getOperand(0)),
+                                SimplifiedLoopNests);
+    }
   }
   // Clean up dead instructions.
   Changed |= DeleteDeadPHIs(L->getHeader());
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 6768860caa..82d918eeef 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -4534,22 +4534,25 @@ LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
   if (!L->isLoopSimplifyForm())
     return;
 
+  // If there's no interesting work to be done, bail early.
+  if (IU.empty()) return;
+
+#ifndef NDEBUG
   // All dominating loops must have preheaders, or SCEVExpander may not be able
   // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
   //
-  // FIXME: This is a little absurd. I think LoopSimplify should be taught
-  // to create a preheader under any circumstance.
+  // IVUsers analysis should only create users that are dominated by simple loop
+  // headers. Since this loop should dominate all of its users, its user list
+  // should be empty if this loop itself is not within a simple loop nest.
   for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
        Rung; Rung = Rung->getIDom()) {
     BasicBlock *BB = Rung->getBlock();
     const Loop *DomLoop = LI.getLoopFor(BB);
     if (DomLoop && DomLoop->getHeader() == BB) {
-      if (!DomLoop->getLoopPreheader())
-        return;
+      assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
     }
   }
-  // If there's no interesting work to be done, bail early.
-  if (IU.empty()) return;
+#endif // DEBUG
 
   DEBUG(dbgs() << "\nLSR on loop ";
         WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);