diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -1063,63 +1063,80 @@
                           const LangOptions &LangOpts, PassBuilder &PB) {
   PB.registerOptimizerLastEPCallback([&](ModulePassManager &MPM,
                                          PassBuilder::OptimizationLevel Level) {
-    if (CodeGenOpts.SanitizeCoverageType ||
-        CodeGenOpts.SanitizeCoverageIndirectCalls ||
-        CodeGenOpts.SanitizeCoverageTraceCmp) {
-      auto SancovOpts = getSancovOptsFromCGOpts(CodeGenOpts);
-      MPM.addPass(ModuleSanitizerCoveragePass(
-          SancovOpts, CodeGenOpts.SanitizeCoverageAllowlistFiles,
-          CodeGenOpts.SanitizeCoverageBlocklistFiles));
-    }
-
-    auto MSanPass = [&](SanitizerMask Mask, bool CompileKernel) {
-      if (LangOpts.Sanitize.has(Mask)) {
-        int TrackOrigins = CodeGenOpts.SanitizeMemoryTrackOrigins;
-        bool Recover = CodeGenOpts.SanitizeRecover.has(Mask);
-
-        MPM.addPass(
-            MemorySanitizerPass({TrackOrigins, Recover, CompileKernel}));
-        MPM.addPass(createModuleToFunctionPassAdaptor(
-            MemorySanitizerPass({TrackOrigins, Recover, CompileKernel})));
-      }
-    };
-    MSanPass(SanitizerKind::Memory, false);
-    MSanPass(SanitizerKind::KernelMemory, true);
-
-    if (LangOpts.Sanitize.has(SanitizerKind::Thread)) {
-      MPM.addPass(ThreadSanitizerPass());
-      MPM.addPass(createModuleToFunctionPassAdaptor(ThreadSanitizerPass()));
-    }
-
-    auto ASanPass = [&](SanitizerMask Mask, bool CompileKernel) {
-      if (LangOpts.Sanitize.has(Mask)) {
-        bool Recover = CodeGenOpts.SanitizeRecover.has(Mask);
-        bool UseAfterScope = CodeGenOpts.SanitizeAddressUseAfterScope;
-        bool ModuleUseAfterScope = asanUseGlobalsGC(TargetTriple, CodeGenOpts);
-        bool UseOdrIndicator = CodeGenOpts.SanitizeAddressUseOdrIndicator;
-        MPM.addPass(RequireAnalysisPass<ASanGlobalsMetadataAnalysis, Module>());
-        MPM.addPass(ModuleAddressSanitizerPass(
-            CompileKernel, Recover, ModuleUseAfterScope, UseOdrIndicator));
-        MPM.addPass(createModuleToFunctionPassAdaptor(
-            AddressSanitizerPass(CompileKernel, Recover, UseAfterScope)));
-      }
-    };
-    ASanPass(SanitizerKind::Address, false);
-    ASanPass(SanitizerKind::KernelAddress, true);
+    PB.registerOptimizerLastEPCallback(
+        [&](ModulePassManager &MPM, PassBuilder::OptimizationLevel Level) {
+          if (CodeGenOpts.OptimizationLevel == 0) {
+            if (!CodeGenOpts.ThinLTOIndexFile.empty())
+              llvm::report_fatal_error(
+                  "Unexpected optimizer in non-optimized ThinLTO PostLink");
+          } else {
+            if (CodeGenOpts.PrepareForThinLTO)
+              llvm::report_fatal_error(
+                  "Unexpected optimizer in optimized ThinLTO PreLink");
+          }
+
+          if (CodeGenOpts.SanitizeCoverageType ||
+              CodeGenOpts.SanitizeCoverageIndirectCalls ||
+              CodeGenOpts.SanitizeCoverageTraceCmp) {
+            auto SancovOpts = getSancovOptsFromCGOpts(CodeGenOpts);
+            MPM.addPass(ModuleSanitizerCoveragePass(
+                SancovOpts, CodeGenOpts.SanitizeCoverageAllowlistFiles,
+                CodeGenOpts.SanitizeCoverageBlocklistFiles));
+          }
+
+          auto MSanPass = [&](SanitizerMask Mask, bool CompileKernel) {
+            if (LangOpts.Sanitize.has(Mask)) {
+              int TrackOrigins = CodeGenOpts.SanitizeMemoryTrackOrigins;
+              bool Recover = CodeGenOpts.SanitizeRecover.has(Mask);
 
-    auto HWASanPass = [&](SanitizerMask Mask, bool CompileKernel) {
-      if (LangOpts.Sanitize.has(Mask)) {
-        bool Recover = CodeGenOpts.SanitizeRecover.has(Mask);
-        MPM.addPass(HWAddressSanitizerPass(CompileKernel, Recover));
-      }
-    };
-    HWASanPass(SanitizerKind::HWAddress, false);
-    HWASanPass(SanitizerKind::KernelHWAddress, true);
-
-    if (LangOpts.Sanitize.has(SanitizerKind::DataFlow)) {
-      MPM.addPass(DataFlowSanitizerPass(LangOpts.SanitizerBlacklistFiles));
-    }
-  });
+              MPM.addPass(
+                  MemorySanitizerPass({TrackOrigins, Recover, CompileKernel}));
+              MPM.addPass(createModuleToFunctionPassAdaptor(
+                  MemorySanitizerPass({TrackOrigins, Recover, CompileKernel})));
+            }
+          };
+          MSanPass(SanitizerKind::Memory, false);
+          MSanPass(SanitizerKind::KernelMemory, true);
+
+          if (LangOpts.Sanitize.has(SanitizerKind::Thread)) {
+            MPM.addPass(ThreadSanitizerPass());
+            MPM.addPass(
+                createModuleToFunctionPassAdaptor(ThreadSanitizerPass()));
+          }
+
+          auto ASanPass = [&](SanitizerMask Mask, bool CompileKernel) {
+            if (LangOpts.Sanitize.has(Mask)) {
+              bool Recover = CodeGenOpts.SanitizeRecover.has(Mask);
+              bool UseAfterScope = CodeGenOpts.SanitizeAddressUseAfterScope;
+              bool ModuleUseAfterScope =
+                  asanUseGlobalsGC(TargetTriple, CodeGenOpts);
+              bool UseOdrIndicator = CodeGenOpts.SanitizeAddressUseOdrIndicator;
+              MPM.addPass(
+                  RequireAnalysisPass<ASanGlobalsMetadataAnalysis, Module>());
+              MPM.addPass(ModuleAddressSanitizerPass(CompileKernel, Recover,
+                                                     ModuleUseAfterScope,
+                                                     UseOdrIndicator));
+              MPM.addPass(createModuleToFunctionPassAdaptor(
+                  AddressSanitizerPass(CompileKernel, Recover, UseAfterScope)));
+            }
+          };
+          ASanPass(SanitizerKind::Address, false);
+          ASanPass(SanitizerKind::KernelAddress, true);
+
+          auto HWASanPass = [&](SanitizerMask Mask, bool CompileKernel) {
+            if (LangOpts.Sanitize.has(Mask)) {
+              bool Recover = CodeGenOpts.SanitizeRecover.has(Mask);
+              MPM.addPass(HWAddressSanitizerPass(CompileKernel, Recover));
+            }
+          };
+          HWASanPass(SanitizerKind::HWAddress, false);
+          HWASanPass(SanitizerKind::KernelHWAddress, true);
+
+          if (LangOpts.Sanitize.has(SanitizerKind::DataFlow)) {
+            MPM.addPass(
+                DataFlowSanitizerPass(LangOpts.SanitizerBlacklistFiles));
+          }
+        });
 }
 
 /// A clean version of `EmitAssembly` that uses the new pass manager.
@@ -1313,7 +1330,12 @@
             FPM.addPass(BoundsCheckingPass());
           });
 
-    addSanitizers(TargetTriple, CodeGenOpts, LangOpts, PB);
+    if (CodeGenOpts.OptimizationLevel != 0 ||
+        CodeGenOpts.ThinLTOIndexFile.empty()) {
+      // This is testing distributed ThinLTO PostLink. O0 called optimized in
+      // PreLink.
+      addSanitizers(TargetTriple, CodeGenOpts, LangOpts, PB);
+    }
 
     if (Optional<GCOVOptions> Options = getGCOVOptions(CodeGenOpts, LangOpts))
       PB.registerPipelineStartEPCallback(
@@ -1522,6 +1544,10 @@
     Conf.CGFileType = getCodeGenFileType(Action);
     break;
   }
+  Triple TargetTriple(M->getTargetTriple());
+  Conf.OptimizerLastPassBuilderHook = [&](PassBuilder &PB) {
+    addSanitizers(TargetTriple, CGOpts, LOpts, PB);
+  };
   if (Error E =
           thinBackend(Conf, -1, AddStream, *M, *CombinedIndex, ImportList,
                       ModuleToDefinedGVSummaries[M->getModuleIdentifier()],
diff --git a/llvm/include/llvm/LTO/Config.h b/llvm/include/llvm/LTO/Config.h
--- a/llvm/include/llvm/LTO/Config.h
+++ b/llvm/include/llvm/LTO/Config.h
@@ -48,7 +48,9 @@
   TargetOptions Options;
   std::vector<std::string> MAttrs;
   std::vector<std::string> PassPlugins;
-  /// For adding passes that run right before codegen.
+  /// For adding passes that run by optimizer.
+  std::function<void(PassBuilder &)> OptimizerLastPassBuilderHook;
+  /// For adding passes that run right before codegen (NewPM only).
   std::function<void(legacy::PassManager &)> PreCodeGenPassesHook;
   Optional<Reloc::Model> RelocModel = Reloc::PIC_;
   Optional<CodeModel::Model> CodeModel = None;
diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -253,6 +253,9 @@
   PB.registerLoopAnalyses(LAM);
   PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
 
+  if (Conf.OptimizerLastPassBuilderHook)
+    Conf.OptimizerLastPassBuilderHook(PB);
+
   ModulePassManager MPM(Conf.DebugPassManager);
 
   if (!Conf.DisableVerify)