Index: llvm/trunk/lib/LTO/LTO.cpp
===================================================================
--- llvm/trunk/lib/LTO/LTO.cpp
+++ llvm/trunk/lib/LTO/LTO.cpp
@@ -665,6 +665,15 @@
         auto GUID = GlobalValue::getGUID(GlobalValue::getGlobalIdentifier(
             Sym.getIRName(), GlobalValue::ExternalLinkage, ""));
         ThinLTO.PrevailingModuleForGUID[GUID] = BM.getModuleIdentifier();
+
+        // For linker redefined symbols (via --wrap or --defsym) we want to
+        // switch the linkage to `weak` to prevent IPOs from happening.
+        // Find the summary in the module for this very GV and record the new
+        // linkage so that we can switch it when we import the GV.
+        if (Res.LinkerRedefined)
+          if (auto S = ThinLTO.CombinedIndex.findSummaryInModule(
+                  GUID, BM.getModuleIdentifier()))
+            S->setLinkage(GlobalValue::WeakAnyLinkage);
       }
     }
   }
Index: llvm/trunk/lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- llvm/trunk/lib/Transforms/IPO/FunctionImport.cpp
+++ llvm/trunk/lib/Transforms/IPO/FunctionImport.cpp
@@ -537,8 +537,6 @@
   };
 
   auto updateLinkage = [&](GlobalValue &GV) {
-    if (!GlobalValue::isWeakForLinker(GV.getLinkage()))
-      return;
     // See if the global summary analysis computed a new resolved linkage.
     const auto &GS = DefinedGlobals.find(GV.getGUID());
     if (GS == DefinedGlobals.end())
@@ -546,6 +544,16 @@
     auto NewLinkage = GS->second->linkage();
     if (NewLinkage == GV.getLinkage())
       return;
+
+    // Switch the linkage to weakany if asked for, e.g. we do this for
+    // linker redefined symbols (via --wrap or --defsym).
+    if (NewLinkage == GlobalValue::WeakAnyLinkage) {
+      GV.setLinkage(NewLinkage);
+      return;
+    }
+
+    if (!GlobalValue::isWeakForLinker(GV.getLinkage()))
+      return;
     // Check for a non-prevailing def that has interposable linkage
     // (e.g. non-odr weak or linkonce). In that case we can't simply
     // convert to available_externally, since it would lose the
Index: llvm/trunk/test/LTO/Resolution/X86/linker-redef-thin.ll
===================================================================
--- llvm/trunk/test/LTO/Resolution/X86/linker-redef-thin.ll
+++ llvm/trunk/test/LTO/Resolution/X86/linker-redef-thin.ll
@@ -0,0 +1,16 @@
+; RUN: opt -module-summary %s -o %t.o
+; RUN: llvm-lto2 run -o %t1.o %t.o -r %t.o,patatino,pr
+; RUN: llvm-readobj -t %t1.o.0 | FileCheck %s
+
+; CHECK: Name: patatino
+; CHECK-NEXT: Value:
+; CHECK-NEXT: Size:
+; CHECK-NEXT: Binding: Weak
+; CHECK-NEXT: Type: Function
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @patatino() {
+  ret void
+}