Index: llvm/lib/IR/Globals.cpp
===================================================================
--- llvm/lib/IR/Globals.cpp
+++ llvm/lib/IR/Globals.cpp
@@ -590,7 +590,7 @@
 
 const Function *GlobalIFunc::getResolverFunction() const {
   DenseSet<const GlobalAlias *> Aliases;
-  return dyn_cast<Function>(
+  return dyn_cast_or_null<Function>(
       findBaseObject(getResolver(), Aliases, [](const GlobalValue &) {}));
 }
 
Index: llvm/test/Assembler/ifunc-unhandled-constantexpr.ll
===================================================================
--- /dev/null
+++ llvm/test/Assembler/ifunc-unhandled-constantexpr.ll
@@ -0,0 +1,12 @@
+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+
+; Make sure nothing asserts on an unhandled constantexpr for the
+; resolver.
+
+; CHECK: IFunc must have a Function resolver
+; CHECK-NEXT: ptr @ifunc_shl
+@ifunc_shl = ifunc void (), ptr inttoptr (i64 shl (i64 ptrtoint (ptr @resolver to i64), i64 4) to ptr)
+
+define ptr @resolver() {
+  ret ptr null
+}