diff --git a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
--- a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -1099,6 +1099,10 @@
       if (VTP.VTableOffset != P.AddressPointOffset + ByteOffset)
         continue;
 
+      assert((VTP.FuncVI) && "FuncVI must not be nullptr");
+      if (mustBeUnreachableFunction(VTP.FuncVI))
+        continue;
+
       TargetsForSlot.push_back(VTP.FuncVI);
     }
   }
diff --git a/llvm/test/ThinLTO/X86/Inputs/devirt_hybrid_after_filtering_unreachable_lib.ll b/llvm/test/ThinLTO/X86/Inputs/devirt_after_filtering_unreachable_lib.ll
rename from llvm/test/ThinLTO/X86/Inputs/devirt_hybrid_after_filtering_unreachable_lib.ll
rename to llvm/test/ThinLTO/X86/Inputs/devirt_after_filtering_unreachable_lib.ll
diff --git a/llvm/test/ThinLTO/X86/devirt_hybrid_after_filtering_unreachable.ll b/llvm/test/ThinLTO/X86/devirt_after_filtering_unreachable.ll
rename from llvm/test/ThinLTO/X86/devirt_hybrid_after_filtering_unreachable.ll
rename to llvm/test/ThinLTO/X86/devirt_after_filtering_unreachable.ll
--- a/llvm/test/ThinLTO/X86/devirt_hybrid_after_filtering_unreachable.ll
+++ b/llvm/test/ThinLTO/X86/devirt_after_filtering_unreachable.ll
@@ -1,9 +1,9 @@
-; Test that unreachable functions are ignored by WPD in hybrid LTO.
+; Test that unreachable functions are ignored by WPD in hybrid LTO, and thin LTO.
 ; In this test case, the unreachable function is the virtual deleting destructor of an abstract class.
 
 ; Generate split module with summary for hybrid Regular LTO WPD
 ; RUN: opt -thinlto-bc -thinlto-split-lto-unit %s -o %t-main.bc
-; RUN: opt -thinlto-bc -thinlto-split-lto-unit %p/Inputs/devirt_hybrid_after_filtering_unreachable_lib.ll -o %t-foo.bc
+; RUN: opt -thinlto-bc -thinlto-split-lto-unit %p/Inputs/devirt_after_filtering_unreachable_lib.ll -o %t-foo.bc
 ; Tests that devirtualization happens.
 ; RUN: llvm-lto2 run -save-temps %t-main.bc %t-foo.bc -pass-remarks=. -o %t \
 ; RUN:   -whole-program-visibility \
@@ -56,6 +56,80 @@
  
 ; REMARK-COUNT-1: single-impl: devirtualized a call to _ZN7DerivedD0Ev
 
+; Generate unsplit module with summary for ThinLTO index-based WPD.
+; RUN: opt -thinlto-bc -o %t3.o %s
+; RUN: opt -thinlto-bc -o %t4.o %p/Inputs/devirt_after_filtering_unreachable_lib.ll
+
+; Check that EnableSplitLTOUnit is off, and check the content of summary information.
+; RUN: llvm-dis -o - %t3.o | FileCheck %s --check-prefix=NOENABLESPLITFLAG
+; NOENABLESPLITFLAG-DAG: !{i32 1, !"EnableSplitLTOUnit", i32 0}
+; NOENABLESPLITFLAG-DAG: [[BaseD0:\^[0-9]+]] = gv: (name: "_ZN4BaseD0Ev"
+; NOENABLESPLITFLAG-DAG: [[BaseD2:\^[0-9]+]] = gv: (name: "_ZN4BaseD2Ev"
+; NOENABLESPLITFLAG-DAG: [[BaseTI:\^[0-9]+]] = gv: (name: "_ZTI4Base"
+; NOENABLESPLITFLAG-DAG: [[PureVirtual:\^[0-9]+]] = gv: (name: "__cxa_pure_virtual"
+; NOENABLESPLITFLAG-DAG: [[Base:\^[0-9]+]] = gv: (name: "_ZTV4Base", {{.*}} vTableFuncs: ((virtFunc: [[BaseD2]], offset: 16), (virtFunc: [[BaseD0]], offset: 24)), refs: ([[BaseTI]], [[BaseD2]], [[BaseD0]], [[PureVirtual]])
+; NOENABLESPLITFLAG-DAG: typeidCompatibleVTable: (name: "_ZTS4Base", summary: ((offset: 16, [[Base]])))
+; NOENABLESPLITFLAG-DAG: typeidCompatibleVTable: (name: "_ZTSM4BaseFvvE.virtual", summary: ((offset: 32, [[Base]])))
+
+; Check that EnableSplitLTOUnit is off, and check the content of summary information.
+; RUN: llvm-dis -o - %t4.o | FileCheck %s --check-prefix=LIBNOENABLESPLITFLAG
+; LIBNOENABLESPLITFLAG-DAG: !{i32 1, !"EnableSplitLTOUnit", i32 0}
+; LIBNOENABLESPLITFLAG-DAG: [[DerivedD0:\^[0-9]+]] = gv: (name: "_ZN7DerivedD0Ev"
+; LIBNOENABLESPLITFLAG-DAG: [[BaseD0:\^[0-9]+]] = gv: (name: "_ZN4BaseD0Ev"
+; LIBNOENABLESPLITFLAG-DAG: [[DerivedTI:\^[0-9]+]] = gv: (name: "_ZTI7Derived"
+; LIBNOENABLESPLITFLAG-DAG: [[DerivedD2:\^[0-9]+]] = gv: (name: "_ZN7DerivedD2Ev"
+; LIBNOENABLESPLITFLAG-DAG: [[DerivedX:\^[0-9]+]] = gv: (name: "_ZN7Derived1xEv"
+; LIBNOENABLESPLITFLAG-DAG: [[BaseTI:\^[0-9]+]] = gv: (name: "_ZTI4Base"
+; LIBNOENABLESPLITFLAG-DAG: [[PureVirtual:\^[0-9]+]] = gv: (name: "__cxa_pure_virtual"
+; LIBNOENABLESPLITFLAG-DAG: [[BaseD2:\^[0-9]+]] = gv: (name: "_ZN4BaseD2Ev"
+; LIBNOENABLESPLITFLAG-DAG: [[Base:\^[0-9]+]] = gv: (name: "_ZTV4Base", {{.*}} vTableFuncs: ((virtFunc: [[BaseD2]], offset: 16), (virtFunc: [[BaseD0]], offset: 24)), refs: ([[BaseTI]], [[BaseD2]], [[BaseD0]], [[PureVirtual]])
+; LIBNOENABLESPLITFLAG-DAG: [[Derived:\^[0-9]+]] = gv: (name: "_ZTV7Derived", {{.*}} vTableFuncs: ((virtFunc: [[DerivedD2]], offset: 16), (virtFunc: [[DerivedD0]], offset: 24), (virtFunc: [[DerivedX]], offset: 32)), refs: ([[DerivedTI]], [[DerivedX]], [[DerivedD2]], [[DerivedD0]])
+; LIBNOENABLESPLITFLAG-DAG: typeidCompatibleVTable: (name: "_ZTS4Base", summary: ((offset: 16, [[Derived]]), (offset: 16, [[Base]])))
+; LIBNOENABLESPLITFLAG-DAG: typeidCompatibleVTable: (name: "_ZTS7Derived", summary: ((offset: 16, [[Derived]])))
+; LIBNOENABLESPLITFLAG-DAG: typeidCompatibleVTable: (name: "_ZTSM4BaseFvvE.virtual", summary: ((offset: 32, [[Derived]]), (offset: 32, [[Base]])))
+; LIBNOENABLESPLITFLAG-DAG: typeidCompatibleVTable: (name: "_ZTSM7DerivedFvvE.virtual", summary: ((offset: 32, [[Derived]])))
+
+; Index based WPD
+; RUN: llvm-lto2 run %t4.o %t3.o -save-temps -pass-remarks=. \
+; RUN:   -whole-program-visibility \
+; RUN:   -wholeprogramdevirt-print-index-based \
+; RUN:   -o %t5 \
+; RUN:   -r=%t4.o,_ZN7Derived1xEv,pl \
+; RUN:   -r=%t4.o,printf, \
+; RUN:   -r=%t4.o,_Z3fooP4Base,pl \
+; RUN:   -r=%t4.o,_ZN7DerivedD2Ev,pl \
+; RUN:   -r=%t4.o,_ZN7DerivedD0Ev,pl \
+; RUN:   -r=%t4.o,_ZN4BaseD2Ev,pl \
+; RUN:   -r=%t4.o,_ZN4BaseD0Ev,pl \
+; RUN:   -r=%t4.o,__cxa_pure_virtual, \
+; RUN:   -r=%t4.o,_ZdlPv, \
+; RUN:   -r=%t4.o,_ZTV7Derived,pl \
+; RUN:   -r=%t4.o,_ZTVN10__cxxabiv120__si_class_type_infoE, \
+; RUN:   -r=%t4.o,_ZTS7Derived,pl \
+; RUN:   -r=%t4.o,_ZTVN10__cxxabiv117__class_type_infoE, \
+; RUN:   -r=%t4.o,_ZTS4Base,pl \
+; RUN:   -r=%t4.o,_ZTI4Base,pl \
+; RUN:   -r=%t4.o,_ZTI7Derived,pl \
+; RUN:   -r=%t4.o,_ZTV4Base,pl \
+; RUN:   -r=%t3.o,main,plx \
+; RUN:   -r=%t3.o,_Znwm, \
+; RUN:   -r=%t3.o,_ZN7DerivedC2Ev,pl \
+; RUN:   -r=%t3.o,_Z3fooP4Base, \
+; RUN:   -r=%t3.o,_ZN4BaseC2Ev,pl \
+; RUN:   -r=%t3.o,_ZN4BaseD2Ev, \
+; RUN:   -r=%t3.o,_ZN4BaseD0Ev, \
+; RUN:   -r=%t3.o,__cxa_pure_virtual, \
+; RUN:   -r=%t3.o,printf, \
+; RUN:   -r=%t3.o,_ZTV7Derived, \
+; RUN:   -r=%t3.o,_ZTV4Base, \
+; RUN:   -r=%t3.o,_ZTVN10__cxxabiv117__class_type_infoE, \
+; RUN:   -r=%t3.o,_ZTS4Base, \
+; RUN:   -r=%t3.o,_ZTI4Base, 2>&1 | FileCheck %s --check-prefix=PRINT --check-prefix=THINREMARK
+
+; PRINT-DAG: Devirtualized call to {{.*}} (_ZN7DerivedD0Ev)
+; THINREMARK: single-impl: devirtualized a call to _ZN7DerivedD0Ev
+; THINREMARK: single-impl: devirtualized a call to _ZN7DerivedD0Ev
+
 ; ModuleID = 'tmp.cc'
 source_filename = "tmp.cc"
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"