Index: llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
===================================================================
--- llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -445,6 +445,13 @@
 
   void rebuildGlobal(VTableBits &B);
 
+  // Apply the summary resolution for Slot to all virtual calls in SlotInfo.
+  void importResolution(VTableSlot Slot, VTableSlotInfo &SlotInfo);
+
+  // If we were able to eliminate all unsafe uses for a type checked load,
+  // eliminate the associated type tests by replacing them with true.
+  void removeRedundantTypeTests();
+
   bool run();
 
   // Lower the module using the action and summary passed as command line
@@ -1103,6 +1110,34 @@
   }
 }
 
+void DevirtModule::importResolution(VTableSlot Slot, VTableSlotInfo &SlotInfo) {
+  const WholeProgramDevirtResolution &Res =
+      Summary->getTypeIdSummary(cast<MDString>(Slot.TypeID)->getString())
+          .WPDRes[Slot.ByteOffset];
+
+  if (Res.TheKind == WholeProgramDevirtResolution::SingleImpl) {
+    // The type of the function in the declaration is irrelevant because every
+    // call site will cast it to the correct type.
+    auto *SingleImpl = M.getOrInsertFunction(
+        Res.SingleImplName, Type::getVoidTy(M.getContext()), nullptr);
+
+    // This is the import phase so we should not be exporting anything.
+    bool IsExported = false;
+    applySingleImplDevirt(SlotInfo, SingleImpl, IsExported);
+    assert(!IsExported);
+  }
+}
+
+void DevirtModule::removeRedundantTypeTests() {
+  auto True = ConstantInt::getTrue(M.getContext());
+  for (auto &&U : NumUnsafeUsesForTypeTest) {
+    if (U.second == 0) {
+      U.first->replaceAllUsesWith(True);
+      U.first->eraseFromParent();
+    }
+  }
+}
+
 bool DevirtModule::run() {
   Function *TypeTestFunc =
       M.getFunction(Intrinsic::getName(Intrinsic::type_test));
@@ -1125,6 +1160,17 @@
   if (TypeCheckedLoadFunc)
     scanTypeCheckedLoadUsers(TypeCheckedLoadFunc);
 
+  if (Action == PassSummaryAction::Import) {
+    for (auto &S : CallSlots)
+      importResolution(S.first, S.second);
+
+    removeRedundantTypeTests();
+
+    // The rest of the code is only necessary when exporting or during regular
+    // LTO, so we are done.
+    return true;
+  }
+
   // Rebuild type metadata into a map for easy lookup.
   std::vector<VTableBits> Bits;
   DenseMap<Metadata *, std::set<TypeMemberInfo>> TypeIdMap;
@@ -1223,17 +1269,7 @@
     }
   }
 
-  // If we were able to eliminate all unsafe uses for a type checked load,
-  // eliminate the type test by replacing it with true.
-  if (TypeCheckedLoadFunc) {
-    auto True = ConstantInt::getTrue(M.getContext());
-    for (auto &&U : NumUnsafeUsesForTypeTest) {
-      if (U.second == 0) {
-        U.first->replaceAllUsesWith(True);
-        U.first->eraseFromParent();
-      }
-    }
-  }
+  removeRedundantTypeTests();
 
   // Rebuild each global we touched as part of virtual constant propagation to
   // include the before and after bytes.
Index: llvm/test/Transforms/WholeProgramDevirt/Inputs/import-single-impl.yaml
===================================================================
--- /dev/null
+++ llvm/test/Transforms/WholeProgramDevirt/Inputs/import-single-impl.yaml
@@ -0,0 +1,13 @@
+---
+TypeIdMap:
+  typeid1:
+    WPDRes:
+      0:
+        Kind: SingleImpl
+        SingleImplName: singleimpl1
+  typeid2:
+    WPDRes:
+      8:
+        Kind: SingleImpl
+        SingleImplName: singleimpl2
+...
Index: llvm/test/Transforms/WholeProgramDevirt/import.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/WholeProgramDevirt/import.ll
@@ -0,0 +1,49 @@
+; RUN: opt -S -wholeprogramdevirt -wholeprogramdevirt-summary-action=import -wholeprogramdevirt-read-summary=%S/Inputs/import-single-impl.yaml < %s | FileCheck --check-prefixes=CHECK,SINGLE-IMPL %s
+
+target datalayout = "e-p:64:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK: define i32 @call1
+define i32 @call1(i8* %obj) {
+  %vtableptr = bitcast i8* %obj to [3 x i8*]**
+  %vtable = load [3 x i8*]*, [3 x i8*]** %vtableptr
+  %vtablei8 = bitcast [3 x i8*]* %vtable to i8*
+  %p = call i1 @llvm.type.test(i8* %vtablei8, metadata !"typeid1")
+  call void @llvm.assume(i1 %p)
+  %fptrptr = getelementptr [3 x i8*], [3 x i8*]* %vtable, i32 0, i32 0
+  %fptr = load i8*, i8** %fptrptr
+  %fptr_casted = bitcast i8* %fptr to i32 (i8*, i32)*
+  ; SINGLE-IMPL: call i32 bitcast (void ()* @singleimpl1 to i32 (i8*, i32)*)
+  %result = call i32 %fptr_casted(i8* %obj, i32 1)
+  ret i32 %result
+}
+
+; CHECK: define i1 @call2
+define i1 @call2(i8* %obj) {
+  %vtableptr = bitcast i8* %obj to [1 x i8*]**
+  %vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
+  %vtablei8 = bitcast [1 x i8*]* %vtable to i8*
+  %pair = call {i8*, i1} @llvm.type.checked.load(i8* %vtablei8, i32 8, metadata !"typeid2")
+  %fptr = extractvalue {i8*, i1} %pair, 0
+  %p = extractvalue {i8*, i1} %pair, 1
+  ; SINGLE-IMPL: br i1 true,
+  br i1 %p, label %cont, label %trap
+
+cont:
+  %fptr_casted = bitcast i8* %fptr to i1 (i8*, i32)*
+  ; SINGLE-IMPL: call i1 bitcast (void ()* @singleimpl2 to i1 (i8*, i32)*)
+  %result = call i1 %fptr_casted(i8* %obj, i32 undef)
+  ret i1 %result
+
+trap:
+  call void @llvm.trap()
+  unreachable
+}
+
+; SINGLE-IMPL-DAG: declare void @singleimpl1()
+; SINGLE-IMPL-DAG: declare void @singleimpl2()
+
+declare void @llvm.assume(i1)
+declare void @llvm.trap()
+declare {i8*, i1} @llvm.type.checked.load(i8*, i32, metadata)
+declare i1 @llvm.type.test(i8*, metadata)