diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -7347,12 +7347,34 @@
     // Keep constructing SCEVs' for phis recursively for now.
     return nullptr;
 
-  case Instruction::Select:
+  case Instruction::Select: {
+    // Check if U is a select that can be simplified to a SCEVUnknown.
+    auto CanSimplifyToUnknown = [this, U]() {
+      if (U->getType()->isIntegerTy(1) || isa<ConstantInt>(U->getOperand(0)))
+        return false;
+
+      auto *ICI = dyn_cast<ICmpInst>(U->getOperand(0));
+      if (!ICI)
+        return false;
+      Value *LHS = ICI->getOperand(0);
+      Value *RHS = ICI->getOperand(1);
+      if (ICI->getPredicate() == CmpInst::ICMP_EQ ||
+          ICI->getPredicate() == CmpInst::ICMP_NE) {
+        if (!(isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()))
+          return true;
+      } else if (getTypeSizeInBits(LHS->getType()) >
+                 getTypeSizeInBits(U->getType()))
+        return true;
+      return false;
+    };
+    if (CanSimplifyToUnknown())
+      return getUnknown(U);
+
     for (Value *Inc : U->operands())
       Ops.push_back(Inc);
     return nullptr;
     break;
-
+  }
   case Instruction::Call:
   case Instruction::Invoke:
     if (Value *RV = cast<CallBase>(U)->getReturnedArgOperand()) {