diff --git a/llvm/include/llvm/Analysis/ValueLattice.h b/llvm/include/llvm/Analysis/ValueLattice.h
--- a/llvm/include/llvm/Analysis/ValueLattice.h
+++ b/llvm/include/llvm/Analysis/ValueLattice.h
@@ -75,7 +75,9 @@
     overdefined,
   };
 
-  ValueLatticeElementTy Tag;
+  ValueLatticeElementTy Tag : 6;
+  /// Number of times a constant range has been extended with widening enabled.
+  unsigned NumRangeExtensions : 8;
 
   /// The union either stores a pointer to a constant or a constant range,
   /// associated to the lattice element. We have to ensure that Range is
@@ -133,6 +135,7 @@
         new (&Range) ConstantRange(Other.Range);
       else
         Range = Other.Range;
+      NumRangeExtensions = Other.NumRangeExtensions;
       break;
     case constant:
     case notconstant:
@@ -287,7 +290,8 @@
   /// range or the object must be undef. The tag is set to
   /// constant_range_including_undef if either the existing value or the new
   /// range may include undef.
-  bool markConstantRange(ConstantRange NewR, bool MayIncludeUndef = false) {
+  bool markConstantRange(ConstantRange NewR, bool MayIncludeUndef = false,
+                         bool CheckWiden = false) {
     if (NewR.isFullSet())
       return markOverdefined();
 
@@ -304,6 +308,11 @@
       if (getConstantRange() == NewR)
         return Tag != OldTag;
 
+      // Simple form of widening. If a range is extended multiple times, go to
+      // overdefined.
+      if (CheckWiden && ++NumRangeExtensions == 1)
+        return markOverdefined();
+
       assert(NewR.contains(getConstantRange()) &&
              "Existing range must be a subset of NewR");
       Range = std::move(NewR);
@@ -314,6 +323,7 @@
     if (NewR.isEmptySet())
       return markOverdefined();
 
+    NumRangeExtensions = 0;
     Tag = NewTag;
     new (&Range) ConstantRange(std::move(NewR));
     return true;
@@ -321,7 +331,7 @@
 
   /// Updates this object to approximate both this object and RHS. Returns
   /// true if this object has been changed.
-  bool mergeIn(const ValueLatticeElement &RHS) {
+  bool mergeIn(const ValueLatticeElement &RHS, bool CheckWiden = false) {
     if (RHS.isUnknown() || isOverdefined())
       return false;
     if (RHS.isOverdefined()) {
@@ -337,7 +347,7 @@
         return markConstant(RHS.getConstant(), /*MayIncludeUndef=*/true);
       if (RHS.isConstantRange())
         return markConstantRange(RHS.getConstantRange(true),
-                                 /*MayIncludeUndef=*/true);
+                                 /*MayIncludeUndef=*/true, CheckWiden);
       return markOverdefined();
     }
 
@@ -380,7 +390,7 @@
     ConstantRange NewR = getConstantRange().unionWith(RHS.getConstantRange());
     return markConstantRange(
         std::move(NewR),
-        /*MayIncludeUndef=*/RHS.isConstantRangeIncludingUndef());
+        /*MayIncludeUndef=*/RHS.isConstantRangeIncludingUndef(), CheckWiden);
   }
 
   // Compares this symbolic value with Other using Pred and returns either
@@ -412,7 +422,9 @@
   }
 };
 
-raw_ostream &operator<<(raw_ostream &OS, const ValueLatticeElement &Val);
+static_assert(sizeof(ValueLatticeElement) <= 40,
+              "size of ValueLatticeElement changed unexpectedly");
 
+raw_ostream &operator<<(raw_ostream &OS, const ValueLatticeElement &Val);
 } // end namespace llvm
 #endif
diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp
--- a/llvm/lib/Transforms/Scalar/SCCP.cpp
+++ b/llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -401,15 +401,7 @@
 
   bool mergeInValue(ValueLatticeElement &IV, Value *V,
                     ValueLatticeElement MergeWithV, bool Widen = true) {
-    // Do a simple form of widening, to avoid extending a range repeatedly in a
-    // loop. If IV is a constant range, it means we already set it once. If
-    // MergeWithV would extend IV, mark V as overdefined.
-    if (Widen && IV.isConstantRange() && MergeWithV.isConstantRange() &&
-        !IV.getConstantRange().contains(MergeWithV.getConstantRange())) {
-      markOverdefined(IV, V);
-      return true;
-    }
-    if (IV.mergeIn(MergeWithV)) {
+    if (IV.mergeIn(MergeWithV, Widen)) {
       pushToWorkList(IV, V);
       LLVM_DEBUG(dbgs() << "Merged " << MergeWithV << " into " << *V << " : "
                         << IV << "\n");