diff --git a/compiler-rt/test/tsan/blacklist2.cpp b/compiler-rt/test/tsan/blacklist2.cpp
--- a/compiler-rt/test/tsan/blacklist2.cpp
+++ b/compiler-rt/test/tsan/blacklist2.cpp
@@ -3,7 +3,7 @@
 // RUN: echo "fun:*Blacklisted_Thread2*" > %t.blacklist
 // RUN: echo "fun:*CallTouchGlobal*" >> %t.blacklist
 
-// RUN: %clangxx_tsan %s -fsanitize-blacklist=%t.blacklist -o %t
+// RUN: %clangxx_tsan -O1 %s -fsanitize-blacklist=%t.blacklist -o %t
 // RUN: %deflake %run %t 2>&1 | FileCheck %s
 #include "test.h"
 
@@ -18,13 +18,13 @@
   return NULL;
 }
 
-void TouchGlobal() {
+void TouchGlobal() __attribute__((noinline)) {
   // CHECK: Previous write of size 4
   // CHECK: #0 TouchGlobal{{.*}}blacklist2.cpp:[[@LINE+1]]
   Global--;
 }
 
-void CallTouchGlobal() {
+void CallTouchGlobal() __attribute__((noinline)) {
   // CHECK: #1 CallTouchGlobal{{.*}}blacklist2.cpp:[[@LINE+1]]
   TouchGlobal();
 }
diff --git a/compiler-rt/test/tsan/free_race.c b/compiler-rt/test/tsan/free_race.c
--- a/compiler-rt/test/tsan/free_race.c
+++ b/compiler-rt/test/tsan/free_race.c
@@ -1,4 +1,4 @@
-// RUN: %clang_tsan %s -o %t
+// RUN: %clang_tsan -O1 %s -o %t
 // RUN: %deflake %run %t | FileCheck %s --check-prefix=CHECK-NOZUPP
 // RUN: %env_tsan_opts=suppressions='%s.supp':print_suppressions=1 %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-SUPP
 
@@ -15,7 +15,7 @@
   return NULL;
 }
 
-void *Thread2(void *x) {
+void *Thread2(void *x) __attribute__((noinline)) {
   barrier_wait(&barrier);
   pthread_mutex_lock(&mtx);
   mem[0] = 42;
diff --git a/compiler-rt/test/tsan/longjmp3.cpp b/compiler-rt/test/tsan/longjmp3.cpp
--- a/compiler-rt/test/tsan/longjmp3.cpp
+++ b/compiler-rt/test/tsan/longjmp3.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_tsan %s -o %t && %deflake %run %t 2>&1 | FileCheck %s
+// RUN: %clang_tsan -O1 %s -o %t && %deflake %run %t 2>&1 | FileCheck %s
 
 #include <pthread.h>
 #include <stdio.h>
@@ -17,14 +17,14 @@
   x++;
 }
 
-void badguy() {
+void badguy() __attribute__((noinline)) {
   pthread_mutex_t mtx;
   pthread_mutex_init(&mtx, 0);
   pthread_mutex_lock(&mtx);
   pthread_mutex_destroy(&mtx);
 }
 
-void mymain() {
+void mymain() __attribute__((noinline)) {
   jmp_buf env;
   if (setjmp(env) == 42) {
     badguy();
diff --git a/compiler-rt/test/tsan/longjmp4.cpp b/compiler-rt/test/tsan/longjmp4.cpp
--- a/compiler-rt/test/tsan/longjmp4.cpp
+++ b/compiler-rt/test/tsan/longjmp4.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_tsan %s -o %t && %deflake %run %t 2>&1 | FileCheck %s
+// RUN: %clang_tsan -O1 %s -o %t && %deflake %run %t 2>&1 | FileCheck %s
 
 #include <pthread.h>
 #include <stdio.h>
@@ -20,14 +20,14 @@
   x++;
 }
 
-void badguy() {
+void badguy() __attribute__((noinline)) {
   pthread_mutex_t mtx;
   pthread_mutex_init(&mtx, 0);
   pthread_mutex_lock(&mtx);
   pthread_mutex_destroy(&mtx);
 }
 
-void mymain() {
+void mymain() __attribute__((noinline)) {
   jmp_buf env;
   if (setjmp(env) == 42) {
     badguy();
diff --git a/compiler-rt/test/tsan/race_on_heap.cpp b/compiler-rt/test/tsan/race_on_heap.cpp
--- a/compiler-rt/test/tsan/race_on_heap.cpp
+++ b/compiler-rt/test/tsan/race_on_heap.cpp
@@ -1,4 +1,4 @@
-// RUN: %clangxx_tsan %s -o %t && %deflake %run %t | FileCheck %s
+// RUN: %clangxx_tsan -O1 %s -o %t && %deflake %run %t | FileCheck %s
 #include <pthread.h>
 #include <stdlib.h>
 #include <stdio.h>
@@ -14,7 +14,7 @@
   return 0;
 }
 
-void *alloc() {
+void *alloc() __attribute__((noinline)) {
   return malloc(99);
 }
 
diff --git a/compiler-rt/test/tsan/race_top_suppression.cpp b/compiler-rt/test/tsan/race_top_suppression.cpp
--- a/compiler-rt/test/tsan/race_top_suppression.cpp
+++ b/compiler-rt/test/tsan/race_top_suppression.cpp
@@ -1,12 +1,12 @@
 // RUN: echo "race_top:TopFunction" > %t.supp
-// RUN: %clangxx_tsan %s -o %t
+// RUN: %clangxx_tsan -O1 %s -o %t
 // RUN: %env_tsan_opts=suppressions='%t.supp' %run %t 2>&1 | FileCheck %s
 // RUN: rm %t.supp
 #include "test.h"
 
 int Global;
 
-void TopFunction(int *p) {
+void TopFunction(int *p) __attribute__((noinline)) {
   *p = 1;
 }
 
diff --git a/compiler-rt/test/tsan/simple_stack.c b/compiler-rt/test/tsan/simple_stack.c
--- a/compiler-rt/test/tsan/simple_stack.c
+++ b/compiler-rt/test/tsan/simple_stack.c
@@ -32,7 +32,7 @@
   return NULL;
 }
 
-void StartThread(pthread_t *t, void *(*f)(void*)) {
+void __attribute__((noinline)) StartThread(pthread_t *t, void *(*f)(void*)) {
   pthread_create(t, NULL, f, NULL);
 }
 
@@ -46,14 +46,14 @@
   return 0;
 }
 
-// RUN: %clang_tsan %s -o %t && %deflake %run %t 2>&1 | FileCheck %s
+// RUN: %clang_tsan -O1 %s -o %t && %deflake %run %t 2>&1 | FileCheck %s
 
 // Also check that functions instrumentation can be configured by either driver
 // or legacy flags:
 
-// RUN: %clangxx_tsan %s -o %t -fno-sanitize-thread-func-entry-exit && %deflake %run %t 2>&1 \
+// RUN: %clangxx_tsan -O1 %s -o %t -fno-sanitize-thread-func-entry-exit && %deflake %run %t 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FUNC-ENTRY-EXIT-OFF %s
-// RUN: %clangxx_tsan %s -o %t -mllvm -tsan-instrument-func-entry-exit=0 && %deflake %run %t 2>&1 \
+// RUN: %clangxx_tsan -O1 %s -o %t -mllvm -tsan-instrument-func-entry-exit=0 && %deflake %run %t 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FUNC-ENTRY-EXIT-OFF %s
 
 // CHECK:      WARNING: ThreadSanitizer: data race
diff --git a/compiler-rt/test/tsan/sleep_sync.cpp b/compiler-rt/test/tsan/sleep_sync.cpp
--- a/compiler-rt/test/tsan/sleep_sync.cpp
+++ b/compiler-rt/test/tsan/sleep_sync.cpp
@@ -1,9 +1,9 @@
-// RUN: %clangxx_tsan %s -o %t && %deflake %run %t | FileCheck %s
+// RUN: %clangxx_tsan -O1 %s -o %t && %deflake %run %t | FileCheck %s
 #include "test.h"
 
 int X = 0;
 
-void MySleep() {
+void MySleep() __attribute__((noinline)) {
   sleep(1);  // the sleep that must appear in the report
 }
 
diff --git a/compiler-rt/test/ubsan/TestCases/Misc/missing_return.cpp b/compiler-rt/test/ubsan/TestCases/Misc/missing_return.cpp
--- a/compiler-rt/test/ubsan/TestCases/Misc/missing_return.cpp
+++ b/compiler-rt/test/ubsan/TestCases/Misc/missing_return.cpp
@@ -1,11 +1,11 @@
-// RUN: %clangxx -fsanitize=return %gmlt %s -o %t
+// RUN: %clangxx -fsanitize=return %gmlt %s -O3 -o %t
 // RUN: not %run %t 2>&1 | FileCheck %s
 // RUN: %env_ubsan_opts=print_stacktrace=1 not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-STACKTRACE
 // Error message does not exact what expected
 // XFAIL: openbsd
 
 // CHECK: missing_return.cpp:[[@LINE+1]]:5: runtime error: execution reached the end of a value-returning function without returning a value
-int f() {
+int f() __attribute__((noinline)) {
 // CHECK-STACKTRACE: #0 {{.*}}f{{.*}}missing_return.cpp:[[@LINE-1]]
 }