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
@@ -76,6 +76,7 @@
 #include "llvm/Transforms/Instrumentation/ThreadSanitizer.h"
 #include "llvm/Transforms/ObjCARC.h"
 #include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Scalar/EarlyCSE.h"
 #include "llvm/Transforms/Scalar/GVN.h"
 #include "llvm/Transforms/Scalar/LowerMatrixIntrinsics.h"
 #include "llvm/Transforms/Utils.h"
@@ -1079,8 +1080,22 @@
 
         MPM.addPass(
             MemorySanitizerPass({TrackOrigins, Recover, CompileKernel}));
-        MPM.addPass(createModuleToFunctionPassAdaptor(
-            MemorySanitizerPass({TrackOrigins, Recover, CompileKernel})));
+        FunctionPassManager FPM(CodeGenOpts.DebugPassManager);
+        FPM.addPass(
+            MemorySanitizerPass({TrackOrigins, Recover, CompileKernel}));
+        if (Level != PassBuilder::OptimizationLevel::O0) {
+          // MemorySanitizer inserts complex instrumentation that mostly
+          // follows the logic of the original code, but operates on
+          // "shadow" values. It can benefit from re-running some
+          // general purpose optimization passes.
+          FPM.addPass(EarlyCSEPass());
+          // TODO: Consider add more passes like in
+          // addGeneralOptsForMemorySanitizer. EarlyCSEPass makes visible
+          // difference on size. It's not clear if the rest is still
+          // usefull. InstCombinePass breakes
+          // compiler-rt/test/msan/select_origin.cpp.
+        }
+        MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
       }
     };
     MSanPass(SanitizerKind::Memory, false);
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
@@ -1,49 +1,51 @@
 // REQUIRES: x86-registered-target
 
-// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O1 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O3 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK
+// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O1 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang -O3 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK,O1
 
-// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O1 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O3 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK
+// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O1 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang -O3 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang     -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O2 -fno-experimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK,O1
 
-// RUN: %clang -target mips64-linux-gnu -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -target mips64el-unknown-linux-gnu -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -target powerpc64-unknown-linux-gnu -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -target powerpc64le-unknown-linux-gnu -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
+// RUN: %clang -target mips64-linux-gnu -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -target mips64el-unknown-linux-gnu -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -target powerpc64-unknown-linux-gnu -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -target powerpc64le-unknown-linux-gnu -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O0
 
 // Verify that -fsanitize=memory and -fsanitize=kernel-memory invoke MSan/KMSAN instrumentation.
 
 // Also check that this works with the new pass manager with and without
 // optimization
-// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O1 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O3 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK
+// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O1 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang -O3 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK,O0
+// FIX: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK,O1
 
-// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O1 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O3 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK
-// 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=CHECK
-// FIX: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK
-// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK
+// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O1 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang -O3 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory  %s -S -emit-llvm -o - | FileCheck %s --check-prefixes=CHECK,O1
+// 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=CHECK,O0
+// FIX: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto=thin -o - | FileCheck %s --check-prefixes=CHECK,O1
+// RUN: %clang     -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK,O0
+// RUN: %clang -O2 -fexperimental-new-pass-manager -target x86_64-unknown-linux -fsanitize=kernel-memory %s -S -emit-llvm -flto -o - | FileCheck %s --check-prefixes=CHECK,O1
 
 int foo(int *a) { return *a; }
+// O0: = alloca
+// O1-NOT: = alloca
 // CHECK: @__msan_