diff --git a/clang/unittests/ASTMatchers/ASTMatchersInternalTest.cpp b/clang/unittests/ASTMatchers/ASTMatchersInternalTest.cpp
--- a/clang/unittests/ASTMatchers/ASTMatchersInternalTest.cpp
+++ b/clang/unittests/ASTMatchers/ASTMatchersInternalTest.cpp
@@ -22,6 +22,8 @@
 
 #if GTEST_HAS_DEATH_TEST
 TEST(HasNameDeathTest, DiesOnEmptyName) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   ASSERT_DEBUG_DEATH({
     DeclarationMatcher HasEmptyName = recordDecl(hasName(""));
     EXPECT_TRUE(notMatches("class X {};", HasEmptyName));
diff --git a/clang/unittests/ASTMatchers/Dynamic/VariantValueTest.cpp b/clang/unittests/ASTMatchers/Dynamic/VariantValueTest.cpp
--- a/clang/unittests/ASTMatchers/Dynamic/VariantValueTest.cpp
+++ b/clang/unittests/ASTMatchers/Dynamic/VariantValueTest.cpp
@@ -164,6 +164,8 @@
                    .getMatcher()
                    .hasTypedMatcher<Stmt>());
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   // Trying to get the wrong matcher fails an assertion in Matcher<T>.  We don't
   // do this test when building with MSVC because its debug C runtime prints the
   // assertion failure message as a wide string, which gtest doesn't understand.
diff --git a/clang/unittests/Basic/FileManagerTest.cpp b/clang/unittests/Basic/FileManagerTest.cpp
--- a/clang/unittests/Basic/FileManagerTest.cpp
+++ b/clang/unittests/Basic/FileManagerTest.cpp
@@ -291,6 +291,8 @@
   EXPECT_EQ(&F1->getFileEntry(), &F1Alias2->getFileEntry());
 
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH((void)manager.getFileRef("dir/f1-alias-alias.cpp"),
                "filename redirected to a non-canonical filename?");
 #endif
diff --git a/clang/unittests/Basic/LineOffsetMappingTest.cpp b/clang/unittests/Basic/LineOffsetMappingTest.cpp
--- a/clang/unittests/Basic/LineOffsetMappingTest.cpp
+++ b/clang/unittests/Basic/LineOffsetMappingTest.cpp
@@ -20,6 +20,8 @@
   EXPECT_FALSE(Mapping);
 
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH((void)Mapping.getLines(), "Storage");
 #endif
 }
@@ -34,6 +36,8 @@
   EXPECT_EQ(20u, Mapping[2]);
 
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH((void)Mapping[3], "Invalid index");
 #endif
 }
diff --git a/clang/unittests/Basic/SarifTest.cpp b/clang/unittests/Basic/SarifTest.cpp
--- a/clang/unittests/Basic/SarifTest.cpp
+++ b/clang/unittests/Basic/SarifTest.cpp
@@ -129,6 +129,8 @@
 #if defined(NDEBUG) || !GTEST_HAS_DEATH_TEST
   GTEST_SKIP() << "This death test is only available for debug builds.";
 #endif
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   // GIVEN:
   SarifDocumentWriter Writer{SourceMgr};
 
@@ -150,6 +152,8 @@
 #if defined(NDEBUG) || !GTEST_HAS_DEATH_TEST
   GTEST_SKIP() << "This death test is only available for debug builds.";
 #endif
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   // GIVEN:
   SarifDocumentWriter Writer{SourceMgr};
 
@@ -169,6 +173,7 @@
 #if defined(NDEBUG) || !GTEST_HAS_DEATH_TEST
   GTEST_SKIP() << "This death test is only available for debug builds.";
 #endif
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
 
   // GIVEN:
   SarifDocumentWriter Writer{SourceMgr};
diff --git a/clang/unittests/Lex/LexerTest.cpp b/clang/unittests/Lex/LexerTest.cpp
--- a/clang/unittests/Lex/LexerTest.cpp
+++ b/clang/unittests/Lex/LexerTest.cpp
@@ -485,6 +485,8 @@
   EXPECT_EQ(tok::string_literal, Result.getKind());
   EXPECT_STREQ("\"'C'\"", Result.getLiteralData());
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(StringifyArg(3), "Invalid arg #");
 #endif
 }
diff --git a/clang/unittests/Serialization/InMemoryModuleCacheTest.cpp b/clang/unittests/Serialization/InMemoryModuleCacheTest.cpp
--- a/clang/unittests/Serialization/InMemoryModuleCacheTest.cpp
+++ b/clang/unittests/Serialization/InMemoryModuleCacheTest.cpp
@@ -29,6 +29,8 @@
   EXPECT_FALSE(Cache.shouldBuildPCM("B"));
 
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(Cache.tryToDropPCM("B"), "PCM to remove is unknown");
   EXPECT_DEATH(Cache.finalizePCM("B"), "PCM to finalize is unknown");
 #endif
@@ -46,6 +48,8 @@
   EXPECT_FALSE(Cache.shouldBuildPCM("B"));
 
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(Cache.addPCM("B", getBuffer(2)), "Already has a PCM");
   EXPECT_DEATH(Cache.addBuiltPCM("B", getBuffer(2)),
                "Trying to override tentative PCM");
@@ -64,6 +68,8 @@
   EXPECT_FALSE(Cache.shouldBuildPCM("B"));
 
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(Cache.addPCM("B", getBuffer(2)), "Already has a PCM");
   EXPECT_DEATH(Cache.addBuiltPCM("B", getBuffer(2)),
                "Trying to override finalized PCM");
@@ -87,6 +93,8 @@
   EXPECT_TRUE(Cache.shouldBuildPCM("B"));
 
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(Cache.addPCM("B", getBuffer(2)), "Already has a PCM");
   EXPECT_DEATH(Cache.tryToDropPCM("B"),
                "PCM to remove is scheduled to be built");
diff --git a/clang/unittests/Tooling/TransformerTest.cpp b/clang/unittests/Tooling/TransformerTest.cpp
--- a/clang/unittests/Tooling/TransformerTest.cpp
+++ b/clang/unittests/Tooling/TransformerTest.cpp
@@ -1593,6 +1593,8 @@
 // Verifies that `Type` and `QualType` are not allowed as top-level matchers in
 // rules.
 TEST(TransformerDeathTest, OrderedRuleTypes) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   RewriteRule QualTypeRule = makeRule(qualType(), changeTo(cat("Q")));
   EXPECT_DEATH(transformer::detail::buildMatchers(QualTypeRule),
                "Matcher must be.*node matcher");
diff --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp
--- a/llvm/unittests/ADT/APFloatTest.cpp
+++ b/llvm/unittests/ADT/APFloatTest.cpp
@@ -1361,6 +1361,8 @@
 #ifdef GTEST_HAS_DEATH_TEST
 #ifndef NDEBUG
 TEST(APFloatTest, SemanticsDeath) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(APFloat(APFloat::IEEEquad(), 0).convertToDouble(),
                "Float semantics is not representable by IEEEdouble");
   EXPECT_DEATH(APFloat(APFloat::IEEEdouble(), 0).convertToFloat(),
diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -1431,6 +1431,8 @@
 #ifdef GTEST_HAS_DEATH_TEST
 #ifndef NDEBUG
 TEST(APIntTest, StringDeath) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH((void)APInt(32, "", 0), "Invalid string length");
   EXPECT_DEATH((void)APInt(32, "0", 0), "Radix should be 2, 8, 10, 16, or 36!");
   EXPECT_DEATH((void)APInt(32, "", 10), "Invalid string length");
diff --git a/llvm/unittests/ADT/APSIntTest.cpp b/llvm/unittests/ADT/APSIntTest.cpp
--- a/llvm/unittests/ADT/APSIntTest.cpp
+++ b/llvm/unittests/ADT/APSIntTest.cpp
@@ -193,6 +193,8 @@
 #if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG)
 
 TEST(APSIntTest, StringDeath) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH((void)APSInt(""), "Invalid string length");
   EXPECT_DEATH((void)APSInt("1a"), "Invalid character in digit string");
 }
diff --git a/llvm/unittests/ADT/AnyTest.cpp b/llvm/unittests/ADT/AnyTest.cpp
--- a/llvm/unittests/ADT/AnyTest.cpp
+++ b/llvm/unittests/ADT/AnyTest.cpp
@@ -160,6 +160,8 @@
   llvm::Any D{'x'};
 
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(llvm::any_cast<int>(A), "");
 
   EXPECT_DEATH(llvm::any_cast<float>(B), "");
diff --git a/llvm/unittests/ADT/BumpPtrListTest.cpp b/llvm/unittests/ADT/BumpPtrListTest.cpp
--- a/llvm/unittests/ADT/BumpPtrListTest.cpp
+++ b/llvm/unittests/ADT/BumpPtrListTest.cpp
@@ -235,6 +235,8 @@
   // Resetting a non-empty list should crash.
   L.push_back(5);
 #if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG)
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(L.resetAlloc(), "Cannot reset allocator if not empty");
 #endif
 }
diff --git a/llvm/unittests/ADT/IteratorTest.cpp b/llvm/unittests/ADT/IteratorTest.cpp
--- a/llvm/unittests/ADT/IteratorTest.cpp
+++ b/llvm/unittests/ADT/IteratorTest.cpp
@@ -566,6 +566,8 @@
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
 // Make sure that we can detect when the first range is not the shortest.
 TEST(ZipIteratorTest, ZipFirstNotShortest) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   const std::array<unsigned, 6> longer = {};
   const std::array<unsigned, 4> shorter = {};
 
diff --git a/llvm/unittests/ADT/STLExtrasTest.cpp b/llvm/unittests/ADT/STLExtrasTest.cpp
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -269,6 +269,8 @@
 
 #if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG)
 TEST(STLExtrasTest, EnumerateDifferentLengths) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   std::vector<int> Ints = {0, 1};
   bool Bools[] = {true, false, true};
   std::string Chars = "abc";
diff --git a/llvm/unittests/ADT/SequenceTest.cpp b/llvm/unittests/ADT/SequenceTest.cpp
--- a/llvm/unittests/ADT/SequenceTest.cpp
+++ b/llvm/unittests/ADT/SequenceTest.cpp
@@ -72,6 +72,8 @@
 
 #if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG)
 TEST(StrongIntDeathTest, OutOfBounds) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   // Values above 'INTMAX_MAX' are not representable.
   EXPECT_DEATH(CheckedInt::from<uintmax_t>(INTMAX_MAX + 1ULL), "Out of bounds");
   EXPECT_DEATH(CheckedInt::from<uintmax_t>(UINTMAX_MAX), "Out of bounds");
diff --git a/llvm/unittests/ADT/SmallVectorTest.cpp b/llvm/unittests/ADT/SmallVectorTest.cpp
--- a/llvm/unittests/ADT/SmallVectorTest.cpp
+++ b/llvm/unittests/ADT/SmallVectorTest.cpp
@@ -360,6 +360,8 @@
   EXPECT_EQ(5, Constructable::getNumDestructorCalls());
 
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(V.truncate(2), "Cannot increase size");
 #endif
   V.truncate(1);
@@ -1340,6 +1342,8 @@
   auto &V = this->V;
   (void)V;
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(V.append(V.begin(), V.begin() + 1), this->AssertionMessage);
 
   ASSERT_EQ(3u, NumBuiltinElts(V));
@@ -1394,6 +1398,8 @@
 TYPED_TEST(SmallVectorReferenceInvalidationTest, AssignRange) {
   auto &V = this->V;
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(V.assign(V.begin(), V.end()), this->AssertionMessage);
   EXPECT_DEATH(V.assign(V.begin(), V.end() - 1), this->AssertionMessage);
 #endif
@@ -1474,6 +1480,8 @@
   auto &V = this->V;
   (void)V;
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(V.insert(V.begin(), V.begin(), V.begin() + 1),
                this->AssertionMessage);
 
diff --git a/llvm/unittests/AsmParser/AsmParserTest.cpp b/llvm/unittests/AsmParser/AsmParserTest.cpp
--- a/llvm/unittests/AsmParser/AsmParserTest.cpp
+++ b/llvm/unittests/AsmParser/AsmParserTest.cpp
@@ -35,6 +35,8 @@
 #ifndef NDEBUG
 
 TEST(AsmParserTest, NonNullTerminatedInput) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   LLVMContext Ctx;
   StringRef Source = "; Empty module \n\1\2";
   SMDiagnostic Error;
diff --git a/llvm/unittests/BinaryFormat/MsgPackWriterTest.cpp b/llvm/unittests/BinaryFormat/MsgPackWriterTest.cpp
--- a/llvm/unittests/BinaryFormat/MsgPackWriterTest.cpp
+++ b/llvm/unittests/BinaryFormat/MsgPackWriterTest.cpp
@@ -516,6 +516,8 @@
 
 #ifdef GTEST_HAS_DEATH_TEST
 #ifndef NDEBUG
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(CompatWriter.write(MemoryBufferRef(s, "")), "compatible mode");
 #endif
 #endif
diff --git a/llvm/unittests/CodeGen/GlobalISel/MachineIRBuilderTest.cpp b/llvm/unittests/CodeGen/GlobalISel/MachineIRBuilderTest.cpp
--- a/llvm/unittests/CodeGen/GlobalISel/MachineIRBuilderTest.cpp
+++ b/llvm/unittests/CodeGen/GlobalISel/MachineIRBuilderTest.cpp
@@ -41,6 +41,8 @@
 #ifndef NDEBUG
 
 TEST_F(AArch64GISelMITest, TestBuildConstantFConstantDeath) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   setUp();
   if (!TM)
     GTEST_SKIP();
diff --git a/llvm/unittests/CodeGen/LowLevelTypeTest.cpp b/llvm/unittests/CodeGen/LowLevelTypeTest.cpp
--- a/llvm/unittests/CodeGen/LowLevelTypeTest.cpp
+++ b/llvm/unittests/CodeGen/LowLevelTypeTest.cpp
@@ -222,6 +222,8 @@
 
 // Invalid to directly change the element size for pointers.
 TEST(LowLevelTypeTest, ChangeElementTypeDeath) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   const LLT P0 = LLT::pointer(0, 32);
   const LLT V2P0 = LLT::fixed_vector(2, P0);
 
diff --git a/llvm/unittests/CodeGen/MachineInstrBundleIteratorTest.cpp b/llvm/unittests/CodeGen/MachineInstrBundleIteratorTest.cpp
--- a/llvm/unittests/CodeGen/MachineInstrBundleIteratorTest.cpp
+++ b/llvm/unittests/CodeGen/MachineInstrBundleIteratorTest.cpp
@@ -29,6 +29,8 @@
 #ifdef GTEST_HAS_DEATH_TEST
 #ifndef NDEBUG
 TEST(MachineInstrBundleIteratorTest, CheckForBundles) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   MyBundledInstr MBI;
   auto I = MBI.getIterator();
   auto RI = I.getReverse();
diff --git a/llvm/unittests/FileCheck/FileCheckTest.cpp b/llvm/unittests/FileCheck/FileCheckTest.cpp
--- a/llvm/unittests/FileCheck/FileCheckTest.cpp
+++ b/llvm/unittests/FileCheck/FileCheckTest.cpp
@@ -1647,6 +1647,8 @@
   ASSERT_THAT_ERROR(std::move(Res.TheError), Succeeded());
 
 #ifndef NDEBUG
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   // Recreating @LINE pseudo numeric variable fails.
   EXPECT_DEATH(Cxt.createLineVariable(),
                "@LINE pseudo numeric variable already created");
diff --git a/llvm/unittests/IR/ConstantsTest.cpp b/llvm/unittests/IR/ConstantsTest.cpp
--- a/llvm/unittests/IR/ConstantsTest.cpp
+++ b/llvm/unittests/IR/ConstantsTest.cpp
@@ -300,6 +300,8 @@
 #ifdef GTEST_HAS_DEATH_TEST
 #ifndef NDEBUG
 TEST(ConstantsTest, ReplaceWithConstantTest) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   LLVMContext Context;
   std::unique_ptr<Module> M(new Module("MyModule", Context));
 
diff --git a/llvm/unittests/IR/MetadataTest.cpp b/llvm/unittests/IR/MetadataTest.cpp
--- a/llvm/unittests/IR/MetadataTest.cpp
+++ b/llvm/unittests/IR/MetadataTest.cpp
@@ -4036,6 +4036,8 @@
 // leading to infinite loops.
 #if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG) && !defined(GTEST_HAS_SEH)
 TEST_F(DistinctMDOperandPlaceholderTest, MetadataAsValue) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   // This shouldn't crash.
   DistinctMDOperandPlaceholder PH(7);
   EXPECT_DEATH(MetadataAsValue::get(Context, &PH),
@@ -4043,12 +4045,16 @@
 }
 
 TEST_F(DistinctMDOperandPlaceholderTest, UniquedMDNode) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   // This shouldn't crash.
   DistinctMDOperandPlaceholder PH(7);
   EXPECT_DEATH(MDTuple::get(Context, &PH), "Unexpected callback to owner");
 }
 
 TEST_F(DistinctMDOperandPlaceholderTest, SecondDistinctMDNode) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   // This shouldn't crash.
   DistinctMDOperandPlaceholder PH(7);
   MDTuple::getDistinct(Context, &PH);
@@ -4057,6 +4063,8 @@
 }
 
 TEST_F(DistinctMDOperandPlaceholderTest, TrackingMDRefAndDistinctMDNode) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   // TrackingMDRef doesn't install an owner callback, so it can't be detected
   // as an invalid use.  However, using a placeholder in a TrackingMDRef *and*
   // a distinct node isn't possible and we should assert.
@@ -4249,6 +4257,8 @@
 #if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG) && !defined(GTEST_HAS_SEH)
 typedef MetadataTest MDTupleAllocationDeathTest;
 TEST_F(MDTupleAllocationDeathTest, ResizeRejected) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   MDTuple *A = MDTuple::get(Context, None);
   auto *Value1 = getConstantAsMetadata();
   EXPECT_DEATH(A->push_back(Value1),
diff --git a/llvm/unittests/IR/ValueHandleTest.cpp b/llvm/unittests/IR/ValueHandleTest.cpp
--- a/llvm/unittests/IR/ValueHandleTest.cpp
+++ b/llvm/unittests/IR/ValueHandleTest.cpp
@@ -191,6 +191,8 @@
 #ifdef GTEST_HAS_DEATH_TEST
 
 TEST_F(ValueHandle, AssertingVH_Asserts) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   AssertingVH<Value> AVH(BitcastV.get());
   EXPECT_DEATH({BitcastV.reset();},
                "An asserting value handle still pointed to this value!");
@@ -533,6 +535,8 @@
 #if LLVM_ENABLE_ABI_BREAKING_CHECKS
 
 TEST_F(ValueHandle, PoisoningVH_Asserts) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   PoisoningVH<Value> VH(BitcastV.get());
 
   // The poisoned handle shouldn't assert when the value is deleted.
@@ -553,6 +557,8 @@
 #endif // LLVM_ENABLE_ABI_BREAKING_CHECKS
 
 TEST_F(ValueHandle, TrackingVH_Asserts) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   {
     TrackingVH<Value> VH(BitcastV.get());
 
diff --git a/llvm/unittests/IR/ValueTest.cpp b/llvm/unittests/IR/ValueTest.cpp
--- a/llvm/unittests/IR/ValueTest.cpp
+++ b/llvm/unittests/IR/ValueTest.cpp
@@ -95,6 +95,8 @@
 #ifndef NDEBUG
 
 TEST(GlobalTest, AlignDeath) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   LLVMContext Ctx;
   std::unique_ptr<Module> M(new Module("TestModule", Ctx));
   Type *Int32Ty = Type::getInt32Ty(Ctx);
diff --git a/llvm/unittests/Support/DataExtractorTest.cpp b/llvm/unittests/Support/DataExtractorTest.cpp
--- a/llvm/unittests/Support/DataExtractorTest.cpp
+++ b/llvm/unittests/Support/DataExtractorTest.cpp
@@ -229,6 +229,8 @@
 #if defined(GTEST_HAS_DEATH_TEST) && defined(_DEBUG) &&                        \
     LLVM_ENABLE_ABI_BREAKING_CHECKS
 TEST(DataExtractorDeathTest, Cursor) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   DataExtractor DE(StringRef("AB"), false, 8);
 
   // Even an unused cursor must be checked for errors:
diff --git a/llvm/unittests/Support/ErrorTest.cpp b/llvm/unittests/Support/ErrorTest.cpp
--- a/llvm/unittests/Support/ErrorTest.cpp
+++ b/llvm/unittests/Support/ErrorTest.cpp
@@ -923,6 +923,8 @@
 
 TEST(Error, FileErrorTest) {
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+    testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
     EXPECT_DEATH(
       {
         Error S = Error::success();
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -1429,6 +1429,8 @@
     MaybeMFR = std::move(mfr);
     EXPECT_FALSE(mfr);
 #if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+    testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
     EXPECT_DEATH(mfr.data(), "Mapping failed but used anyway!");
     EXPECT_DEATH(mfr.size(), "Mapping failed but used anyway!");
 #endif
diff --git a/llvm/unittests/Support/YAMLIOTest.cpp b/llvm/unittests/Support/YAMLIOTest.cpp
--- a/llvm/unittests/Support/YAMLIOTest.cpp
+++ b/llvm/unittests/Support/YAMLIOTest.cpp
@@ -3064,6 +3064,8 @@
   Output yout(ostr);
 #ifdef GTEST_HAS_DEATH_TEST
 #ifndef NDEBUG
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(yout << node, "plain scalar documents are not supported");
 #endif
 #endif
diff --git a/llvm/unittests/Support/raw_pwrite_stream_test.cpp b/llvm/unittests/Support/raw_pwrite_stream_test.cpp
--- a/llvm/unittests/Support/raw_pwrite_stream_test.cpp
+++ b/llvm/unittests/Support/raw_pwrite_stream_test.cpp
@@ -38,6 +38,8 @@
 
 #ifdef GTEST_HAS_DEATH_TEST
 #ifndef NDEBUG
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(OS.pwrite("12345", 5, 0),
                "We don't support extending the stream");
 #endif
@@ -74,6 +76,8 @@
 
 #ifdef GTEST_HAS_DEATH_TEST
 #ifndef NDEBUG
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   EXPECT_DEATH(OS.pwrite("12345", 5, 0),
                "We don't support extending the stream");
 #endif
diff --git a/llvm/unittests/Transforms/Utils/ValueMapperTest.cpp b/llvm/unittests/Transforms/Utils/ValueMapperTest.cpp
--- a/llvm/unittests/Transforms/Utils/ValueMapperTest.cpp
+++ b/llvm/unittests/Transforms/Utils/ValueMapperTest.cpp
@@ -265,6 +265,8 @@
 #ifdef GTEST_HAS_DEATH_TEST
 #ifndef NDEBUG
 TEST(ValueMapperTest, mapMetadataLocalAsMetadata) {
+  testing::GTEST_FLAG(death_test_style) = "threadsafe";
+
   LLVMContext C;
   FunctionType *FTy =
       FunctionType::get(Type::getVoidTy(C), Type::getInt8Ty(C), false);