diff --git a/llvm/lib/Transforms/Scalar/LowerConstantIntrinsics.cpp b/llvm/lib/Transforms/Scalar/LowerConstantIntrinsics.cpp
--- a/llvm/lib/Transforms/Scalar/LowerConstantIntrinsics.cpp
+++ b/llvm/lib/Transforms/Scalar/LowerConstantIntrinsics.cpp
@@ -45,10 +45,18 @@
           "Number of 'objectsize' intrinsic calls handled");
 
 static Value *lowerIsConstantIntrinsic(IntrinsicInst *II) {
-  Value *Op = II->getOperand(0);
-
-  return isa<Constant>(Op) ? ConstantInt::getTrue(II->getType())
-                           : ConstantInt::getFalse(II->getType());
+  SmallVector<Value *> WorkList;
+  WorkList.push_back(II->getOperand(0));
+  while (WorkList.size()) {
+    Value *V = WorkList.back();
+    if (!isa<ConstantData>(V) || isa<UndefValue>(V))
+      return ConstantInt::getFalse(II->getType());
+    WorkList.pop_back();
+    if (auto *CA = dyn_cast<ConstantAggregate>(V))
+      for (Value *Op : CA->operands())
+        WorkList.push_back(Op);
+  }
+  return ConstantInt::getTrue(II->getType());
 }
 
 static bool replaceConditionalBranchesOnConstant(Instruction *II,
diff --git a/llvm/test/Transforms/LowerConstantIntrinsics/constant-intrinsics.ll b/llvm/test/Transforms/LowerConstantIntrinsics/constant-intrinsics.ll
--- a/llvm/test/Transforms/LowerConstantIntrinsics/constant-intrinsics.ll
+++ b/llvm/test/Transforms/LowerConstantIntrinsics/constant-intrinsics.ll
@@ -112,3 +112,26 @@
 
   ret i1 %res6
 }
+
+@real_mode_blob_end = external dso_local global [0 x i8], align 1
+define i1 @global_array() {
+; CHECK-LABEL: @global_array(
+; CHECK-NEXT: ret i1 false
+  %1 = call i1 @llvm.is.constant.i64(i64 ptrtoint ([0 x i8]* @real_mode_blob_end to i64))
+  ret i1 %1
+}
+
+define i1 @undef1() {
+; CHECK-LABEL: undef1(
+; CHECK-NEXT: ret i1 false
+  %1 = call i1 @llvm.is.constant.i64(i64 undef)
+  ret i1 %1
+}
+
+@undef_array = dso_local global [2 x i8] [i8 42, i8 undef]
+define i1 @undef2() {
+; CHECK-LABEL: undef2(
+; CHECK-NEXT: ret i1 false
+  %1 = call i1 @llvm.is.constant.i64(i64 ptrtoint ([2 x i8]* @undef_array to i64))
+  ret i1 %1
+}