Revert "ADT: Fix reference invalidation in SmallVector::push_back and single-element insert"

This reverts commit 9abac60309006db00eca0af406c2e16bef26807c since there
are some bot errors on Windows:
http://lab.llvm.org:8011/#/builders/127/builds/4489

```
FAILED: lib/Support/CMakeFiles/LLVMSupport.dir/IntervalMap.cpp.obj
C:\PROGRA~2\MIB055~1\2017\PROFES~1\VC\Tools\MSVC\1416~1.270\bin\Hostx64\x64\cl.exe  /nologo /TP -DGTEST_HAS_RTTI=0 -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_HAS_EXCEPTIONS=0 -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Ilib\Support -IC:\b\slave\sanitizer-windows\llvm-project\llvm\lib\Support -Iinclude -IC:\b\slave\sanitizer-windows\llvm-project\llvm\include /DWIN32 /D_WINDOWS   /Zc:inline /Zc:__cplusplus /Zi /Zc:strictStrings /Oi /Zc:rvalueCast /bigobj /W4 -wd4141 -wd4146 -wd4244 -wd4267 -wd4291 -wd4351 -wd4456 -wd4457 -wd4458 -wd4459 -wd4503 -wd4624 -wd4722 -wd4100 -wd4127 -wd4512 -wd4505 -wd4610 -wd4510 -wd4702 -wd4245 -wd4706 -wd4310 -wd4701 -wd4703 -wd4389 -wd4611 -wd4805 -wd4204 -wd4577 -wd4091 -wd4592 -wd4319 -wd4709 -wd4324 -w14062 -we4238 /Gw /MD /O2 /Ob2 -UNDEBUG -std:c++14  /EHs-c- /GR- /showIncludes /Folib\Support\CMakeFiles\LLVMSupport.dir\IntervalMap.cpp.obj /Fdlib\Support\CMakeFiles\LLVMSupport.dir\LLVMSupport.pdb /FS -c C:\b\slave\sanitizer-windows\llvm-project\llvm\lib\Support\IntervalMap.cpp
C:\b\slave\sanitizer-windows\llvm-project\llvm\include\llvm/ADT/SmallVector.h(746): error C2672: 'llvm::SmallVectorImpl<T>::insert_one_maybe_copy': no matching overloaded function found
        with
        [
            T=llvm::IntervalMapImpl::Path::Entry
        ]
C:\b\slave\sanitizer-windows\llvm-project\llvm\include\llvm/ADT/SmallVector.h(745): note: while compiling class template member function 'llvm::IntervalMapImpl::Path::Entry *llvm::SmallVectorImpl<T>::insert(llvm::IntervalMapImpl::Path::Entry *,T &&)'
        with
        [
            T=llvm::IntervalMapImpl::Path::Entry
        ]
C:\b\slave\sanitizer-windows\llvm-project\llvm\lib\Support\IntervalMap.cpp(22): note: see reference to function template instantiation 'llvm::IntervalMapImpl::Path::Entry *llvm::SmallVectorImpl<T>::insert(llvm::IntervalMapImpl::Path::Entry *,T &&)' being compiled
        with
        [
            T=llvm::IntervalMapImpl::Path::Entry
        ]
C:\b\slave\sanitizer-windows\llvm-project\llvm\include\llvm/ADT/SmallVector.h(1136): note: see reference to class template instantiation 'llvm::SmallVectorImpl<T>' being compiled
        with
        [
            T=llvm::IntervalMapImpl::Path::Entry
        ]
C:\b\slave\sanitizer-windows\llvm-project\llvm\include\llvm/ADT/IntervalMap.h(790): note: see reference to class template instantiation 'llvm::SmallVector<llvm::IntervalMapImpl::Path::Entry,4>' being compiled
C:\b\slave\sanitizer-windows\llvm-project\llvm\include\llvm/ADT/SmallVector.h(746): error C2783: 'llvm::IntervalMapImpl::Path::Entry *llvm::SmallVectorImpl<T>::insert_one_maybe_copy(llvm::IntervalMapImpl::Path::Entry *,ArgType &&)': could not deduce template argument for '__formal'
        with
        [
            T=llvm::IntervalMapImpl::Path::Entry
        ]
C:\b\slave\sanitizer-windows\llvm-project\llvm\include\llvm/ADT/SmallVector.h(727): note: see declaration of 'llvm::SmallVectorImpl<T>::insert_one_maybe_copy'
        with
        [
            T=llvm::IntervalMapImpl::Path::Entry
        ]
```

1 files changed, 16 insertions, 91 deletions

diff --git a/llvm/unittests/ADT/SmallVectorTest.cpp b/llvm/unittests/ADT/SmallVectorTest.cpp
index c880a6b..d97ab57 100644
--- a/llvm/unittests/ADT/SmallVectorTest.cpp
+++ b/llvm/unittests/ADT/SmallVectorTest.cpp
@@ -53,7 +53,6 @@ public:
 
   Constructable(Constructable && src) : constructed(true) {
     value = src.value;
-    src.value = 0;
     ++numConstructorCalls;
     ++numMoveConstructorCalls;
   }
@@ -75,7 +74,6 @@ public:
   Constructable & operator=(Constructable && src) {
     EXPECT_TRUE(constructed);
     value = src.value;
-    src.value = 0;
     ++numAssignmentCalls;
     ++numMoveAssignmentCalls;
     return *this;
@@ -1058,16 +1056,11 @@ protected:
     return N;
   }
 
-  template <class T> static bool isValueType() {
-    return std::is_same<T, typename VectorT::value_type>::value;
-  }
-
   void SetUp() override {
     SmallVectorTestBase::SetUp();
 
     // Fill up the small size so that insertions move the elements.
-    for (int I = 0, E = NumBuiltinElts(V); I != E; ++I)
-      V.emplace_back(I + 1);
+    V.append({0, 0, 0});
   }
 };
 
@@ -1081,54 +1074,19 @@ TYPED_TEST_CASE(SmallVectorReferenceInvalidationTest,
                 SmallVectorReferenceInvalidationTestTypes);
 
 TYPED_TEST(SmallVectorReferenceInvalidationTest, PushBack) {
-  // Note: setup adds [1, 2, ...] to V until it's at capacity in small mode.
   auto &V = this->V;
-  int N = this->NumBuiltinElts(V);
-
-  // Push back a reference to last element when growing from small storage.
-  V.push_back(V.back());
-  EXPECT_EQ(N, V.back());
-
-  // Check that the old value is still there (not moved away).
-  EXPECT_EQ(N, V[V.size() - 2]);
-
-  // Fill storage again.
-  V.back() = V.size();
-  while (V.size() < V.capacity())
-    V.push_back(V.size() + 1);
-
-  // Push back a reference to last element when growing from large storage.
-  V.push_back(V.back());
-  EXPECT_EQ(int(V.size()) - 1, V.back());
+  (void)V;
+#if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  EXPECT_DEATH(V.push_back(V.back()), this->AssertionMessage);
+#endif
 }
 
 TYPED_TEST(SmallVectorReferenceInvalidationTest, PushBackMoved) {
-  // Note: setup adds [1, 2, ...] to V until it's at capacity in small mode.
   auto &V = this->V;
-  int N = this->NumBuiltinElts(V);
-
-  // Push back a reference to last element when growing from small storage.
-  V.push_back(std::move(V.back()));
-  EXPECT_EQ(N, V.back());
-  if (this->template isValueType<Constructable>()) {
-    // Check that the value was moved (not copied).
-    EXPECT_EQ(0, V[V.size() - 2]);
-  }
-
-  // Fill storage again.
-  V.back() = V.size();
-  while (V.size() < V.capacity())
-    V.push_back(V.size() + 1);
-
-  // Push back a reference to last element when growing from large storage.
-  V.push_back(std::move(V.back()));
-
-  // Check the values.
-  EXPECT_EQ(int(V.size()) - 1, V.back());
-  if (this->template isValueType<Constructable>()) {
-    // Check the value got moved out.
-    EXPECT_EQ(0, V[V.size() - 2]);
-  }
+  (void)V;
+#if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  EXPECT_DEATH(V.push_back(std::move(V.back())), this->AssertionMessage);
+#endif
 }
 
 TYPED_TEST(SmallVectorReferenceInvalidationTest, Resize) {
@@ -1192,53 +1150,20 @@ TYPED_TEST(SmallVectorReferenceInvalidationTest, AssignRange) {
 }
 
 TYPED_TEST(SmallVectorReferenceInvalidationTest, Insert) {
-  // Note: setup adds [1, 2, ...] to V until it's at capacity in small mode.
   auto &V = this->V;
   (void)V;
-
-  // Insert a reference to the back (not at end() or else insert delegates to
-  // push_back()), growing out of small mode. Confirm the value was copied out
-  // (moving out Constructable sets it to 0).
-  V.insert(V.begin(), V.back());
-  EXPECT_EQ(int(V.size() - 1), V.front());
-  EXPECT_EQ(int(V.size() - 1), V.back());
-
-  // Fill up the vector again.
-  while (V.size() < V.capacity())
-    V.push_back(V.size() + 1);
-
-  // Grow again from large storage to large storage.
-  V.insert(V.begin(), V.back());
-  EXPECT_EQ(int(V.size() - 1), V.front());
-  EXPECT_EQ(int(V.size() - 1), V.back());
+#if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  EXPECT_DEATH(V.insert(V.begin(), V.back()), this->AssertionMessage);
+#endif
 }
 
 TYPED_TEST(SmallVectorReferenceInvalidationTest, InsertMoved) {
-  // Note: setup adds [1, 2, ...] to V until it's at capacity in small mode.
   auto &V = this->V;
   (void)V;
-
-  // Insert a reference to the back (not at end() or else insert delegates to
-  // push_back()), growing out of small mode. Confirm the value was copied out
-  // (moving out Constructable sets it to 0).
-  V.insert(V.begin(), std::move(V.back()));
-  EXPECT_EQ(int(V.size() - 1), V.front());
-  if (this->template isValueType<Constructable>()) {
-    // Check the value got moved out.
-    EXPECT_EQ(0, V.back());
-  }
-
-  // Fill up the vector again.
-  while (V.size() < V.capacity())
-    V.push_back(V.size() + 1);
-
-  // Grow again from large storage to large storage.
-  V.insert(V.begin(), std::move(V.back()));
-  EXPECT_EQ(int(V.size() - 1), V.front());
-  if (this->template isValueType<Constructable>()) {
-    // Check the value got moved out.
-    EXPECT_EQ(0, V.back());
-  }
+#if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+  EXPECT_DEATH(V.insert(V.begin(), std::move(V.back())),
+               this->AssertionMessage);
+#endif
 }
 
 TYPED_TEST(SmallVectorReferenceInvalidationTest, InsertN) {