diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1737,7 +1737,12 @@
     }
     break;
   case Instruction::ShuffleVector: {
-    auto *Shuf = cast<ShuffleVectorInst>(I);
+    auto *Shuf = dyn_cast<ShuffleVectorInst>(I);
+    // FIXME: Do we need to handle ConstantExpr involving shufflevectors?
+    if (!Shuf) {
+      Known.resetAll();
+      return;
+    }
     // For undef elements, we don't know anything about the common state of
     // the shuffle result.
     APInt DemandedLHS, DemandedRHS;
@@ -1763,10 +1768,9 @@
     break;
   }
   case Instruction::InsertElement: {
-    auto *IEI = cast<InsertElementInst>(I);
-    Value *Vec = IEI->getOperand(0);
-    Value *Elt = IEI->getOperand(1);
-    auto *CIdx = dyn_cast<ConstantInt>(IEI->getOperand(2));
+    const Value *Vec = I->getOperand(0);
+    const Value *Elt = I->getOperand(1);
+    auto *CIdx = dyn_cast<ConstantInt>(I->getOperand(2));
     // Early out if the index is non-constant or out-of-range.
     unsigned NumElts = DemandedElts.getBitWidth();
     if (!CIdx || CIdx->getValue().uge(NumElts)) {
@@ -1796,9 +1800,8 @@
   case Instruction::ExtractElement: {
     // Look through extract element. If the index is non-constant or
     // out-of-range demand all elements, otherwise just the extracted element.
-    auto* EEI = cast<ExtractElementInst>(I);
-    const Value* Vec = EEI->getVectorOperand();
-    const Value* Idx = EEI->getIndexOperand();
+    const Value *Vec = I->getOperand(0);
+    const Value *Idx = I->getOperand(1);
     auto *CIdx = dyn_cast<ConstantInt>(Idx);
     unsigned NumElts = Vec->getType()->getVectorNumElements();
     APInt DemandedVecElts = APInt::getAllOnesValue(NumElts);
diff --git a/llvm/test/Analysis/ValueTracking/known-bits-from-operator-constexpr.ll b/llvm/test/Analysis/ValueTracking/known-bits-from-operator-constexpr.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Analysis/ValueTracking/known-bits-from-operator-constexpr.ll
@@ -0,0 +1,15 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instsimplify -S | FileCheck %s
+
+; Reproducer for a crash in computeKnownBitsFromOperator due to blindly
+; casting from llvm::Operator to ExtractElementInst. That does not work
+; if the Operator is a ConstantExpr.
+@g = global [21 x i32] zeroinitializer
+define i32 @test1(i32 %a) {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:    [[T:%.*]] = sub i32 [[A:%.*]], extractelement (<4 x i32> ptrtoint (<4 x i32*> getelementptr inbounds ([21 x i32], [21 x i32]* @g, <4 x i32> zeroinitializer, <4 x i32> <i32 1, i32 2, i32 3, i32 17>) to <4 x i32>), i32 3)
+; CHECK-NEXT:    ret i32 [[T]]
+;
+  %t = sub i32 %a, extractelement (<4 x i32> ptrtoint (<4 x i32 *> getelementptr inbounds ([21 x i32], [21 x i32] * @g, <4 x i32> zeroinitializer, <4 x i32> <i32 1, i32 2, i32 3, i32 17>) to <4 x i32>), i32 3)
+  ret i32 %t
+}