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
@@ -1300,10 +1300,11 @@
 
     // If we reached here with a non-empty index file name, then the index
     // file was empty and we are not performing ThinLTO backend compilation
-    // (used in testing in a distributed build environment). Drop any the type
-    // test assume sequences inserted for whole program vtables so that
-    // codegen doesn't complain.
-    if (!CodeGenOpts.ThinLTOIndexFile.empty())
+    // (used in testing in a distributed build environment).
+    bool IsThinLTOPostLink = !CodeGenOpts.ThinLTOIndexFile.empty();
+    // If so drop any the type test assume sequences inserted for whole program
+    // vtables so that codegen doesn't complain.
+    if (IsThinLTOPostLink)
       PB.registerPipelineStartEPCallback(
           [](ModulePassManager &MPM, PassBuilder::OptimizationLevel Level) {
             MPM.addPass(LowerTypeTestsPass(/*ExportSummary=*/nullptr,
@@ -1327,7 +1328,10 @@
             FPM.addPass(BoundsCheckingPass());
           });
 
-    addSanitizers(TargetTriple, CodeGenOpts, LangOpts, PB);
+    // Don't add sanitizers if we are here from ThinLTO PostLink. That already
+    // done on PreLink stage.
+    if (!IsThinLTOPostLink)
+      addSanitizers(TargetTriple, CodeGenOpts, LangOpts, PB);
 
     if (Optional<GCOVOptions> Options = getGCOVOptions(CodeGenOpts, LangOpts))
       PB.registerPipelineStartEPCallback(
diff --git a/clang/test/Driver/asan.c b/clang/test/Driver/asan.c
--- a/clang/test/Driver/asan.c
+++ b/clang/test/Driver/asan.c
@@ -3,7 +3,7 @@
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=address %s -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-ASAN
 // RUN: %clang -O3 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=address %s -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-ASAN
 // RUN: %clang     -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=address %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-ASAN
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=address %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-ASAN
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=address %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-ASAN
 // RUN: %clang     -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=address %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-ASAN
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=address %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-ASAN
 
@@ -21,7 +21,7 @@
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=kernel-address %s -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-KASAN
 // RUN: %clang -O3 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=kernel-address %s -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-KASAN
 // RUN: %clang     -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=kernel-address %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-KASAN
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=kernel-address %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-KASAN
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=kernel-address %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-KASAN
 // RUN: %clang     -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=kernel-address %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-KASAN
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target i386-unknown-linux -fsanitize=kernel-address %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-KASAN
 
@@ -39,7 +39,7 @@
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=hwaddress %s -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-HWASAN
 // RUN: %clang -O3 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=hwaddress %s -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-HWASAN
 // RUN: %clang     -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=hwaddress %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-HWASAN
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=hwaddress %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-HWASAN
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=hwaddress %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-HWASAN
 // RUN: %clang     -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=hwaddress %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-HWASAN
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=hwaddress %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-HWASAN
 
@@ -57,7 +57,7 @@
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
 // RUN: %clang -O3 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
 // RUN: %clang     -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
 // RUN: %clang     -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
 
@@ -68,7 +68,7 @@
 // RUN: %clang     -fno-experimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
 // RUN: %clang -O2 -fno-experimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
 // RUN: %clang     -fno-experimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
-// FIX: %clang -O2 -fno-experimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
+// RUN: %clang -O2 -fno-experimental-new-pass-manager -target aarch64-unknown-linux -fsanitize=kernel-hwaddress %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefix=CHECK-KHWASAN
 // Verify that -fsanitize={address,hwaddres,kernel-address,kernel-hwaddress} invokes ASan, HWAsan, KASan or KHWASan instrumentation.
 
 int foo(int *a) { return *a; }
diff --git a/clang/test/Driver/dfsan.c b/clang/test/Driver/dfsan.c
--- a/clang/test/Driver/dfsan.c
+++ b/clang/test/Driver/dfsan.c
@@ -3,7 +3,7 @@
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=dataflow %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang -O3 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=dataflow %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=dataflow %s -S -emit-llvm -flto=thin -o - | FileCheck %s
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=dataflow %s -S -emit-llvm -flto=thin -o - | FileCheck %s
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=dataflow %s -S -emit-llvm -flto=thin -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=dataflow %s -S -emit-llvm -flto -o - | FileCheck %s
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=dataflow %s -S -emit-llvm -flto -o - | FileCheck %s
 
diff --git a/clang/test/Driver/msan.c b/clang/test/Driver/msan.c
--- a/clang/test/Driver/msan.c
+++ b/clang/test/Driver/msan.c
@@ -31,7 +31,7 @@
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang -O3 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK0
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK0
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s
 
@@ -40,7 +40,7 @@
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang -O3 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK0
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK0
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s
 
diff --git a/clang/test/Driver/sancov.c b/clang/test/Driver/sancov.c
--- a/clang/test/Driver/sancov.c
+++ b/clang/test/Driver/sancov.c
@@ -3,7 +3,7 @@
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize-coverage=trace-pc-guard %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang -O3 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize-coverage=trace-pc-guard %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize-coverage=trace-pc-guard %s -S -emit-llvm -flto=thin -o - | FileCheck %s
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize-coverage=trace-pc-guard %s -S -emit-llvm -flto=thin -o - | FileCheck %s
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize-coverage=trace-pc-guard %s -S -emit-llvm -flto=thin -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize-coverage=trace-pc-guard %s -S -emit-llvm -flto -o - | FileCheck %s
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize-coverage=trace-pc-guard %s -S -emit-llvm -flto -o - | FileCheck %s
 
diff --git a/clang/test/Driver/tsan.c b/clang/test/Driver/tsan.c
--- a/clang/test/Driver/tsan.c
+++ b/clang/test/Driver/tsan.c
@@ -19,7 +19,7 @@
 // RUN: %clang -O3 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=thread %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=thread %s -S -emit-llvm -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=thread %s -S -emit-llvm -flto=thin -o - | FileCheck %s
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=thread %s -S -emit-llvm -flto=thin -o - | FileCheck %s
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=thread %s -S -emit-llvm -flto=thin -o - | FileCheck %s
 // RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=thread %s -S -emit-llvm -flto -o - | FileCheck %s
 // RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=thread %s -S -emit-llvm -flto -o - | FileCheck %s
 
diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -1498,6 +1498,12 @@
   if (PGOOpt && PGOOpt->PseudoProbeForProfiling)
     MPM.addPass(PseudoProbeUpdatePass());
 
+  // Handle OptimizerLastEPCallbacks added by clang on PreLink. Actual
+  // optimization is going to be done in PostLink stage, but clang can't
+  // add callbacks there in case of in-process ThinLTO called by linker.
+  for (auto &C : OptimizerLastEPCallbacks)
+    C(MPM, Level);
+
   // Emit annotation remarks.
   addAnnotationRemarksPass(MPM);