[llvm-branch-commits] [llvm] 33be50d - Revert "Reapply "ADT: Fix reference invalidation in SmallVector::push_back and single-element insert""
Nikita Popov via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Fri Jan 15 00:33:50 PST 2021
Author: Nikita Popov
Date: 2021-01-15T09:28:42+01:00
New Revision: 33be50daa9ce1074c3b423a4ab27c70c0722113a
URL: https://github.com/llvm/llvm-project/commit/33be50daa9ce1074c3b423a4ab27c70c0722113a
DIFF: https://github.com/llvm/llvm-project/commit/33be50daa9ce1074c3b423a4ab27c70c0722113a.diff
LOG: Revert "Reapply "ADT: Fix reference invalidation in SmallVector::push_back and single-element insert""
This reverts commit 260a856c2abcef49c7cb3bdcd999701db3e2af38.
This reverts commit 3043e5a5c33c4c871f4a1dfd621a8839f9a1f0b3.
This reverts commit 49142991a685bd427d7e877c29c77371dfb7634c.
This change had a larger than anticipated compile-time impact,
possibly because the small value optimization is not working as
intended. See D93779.
Added:
Modified:
llvm/include/llvm/ADT/SmallVector.h
llvm/unittests/ADT/SmallVectorTest.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/ADT/SmallVector.h b/llvm/include/llvm/ADT/SmallVector.h
index b9c30abcb579..78d0848b1fcc 100644
--- a/llvm/include/llvm/ADT/SmallVector.h
+++ b/llvm/include/llvm/ADT/SmallVector.h
@@ -220,24 +220,6 @@ class SmallVectorTemplateCommon
}
void assertSafeToEmplace() {}
- /// Reserve enough space to add one element, and return the updated element
- /// pointer in case it was a reference to the storage.
- template <class U>
- static const T *reserveForAndGetAddressImpl(U *This, const T &Elt, size_t N) {
- size_t NewSize = This->size() + N;
- if (LLVM_LIKELY(NewSize <= This->capacity()))
- return &Elt;
-
- bool ReferencesStorage = false;
- int64_t Index = -1;
- if (LLVM_UNLIKELY(This->isReferenceToStorage(&Elt))) {
- ReferencesStorage = true;
- Index = &Elt - This->begin();
- }
- This->grow(NewSize);
- return ReferencesStorage ? This->begin() + Index : &Elt;
- }
-
public:
using size_type = size_t;
using
diff erence_type = ptr
diff _t;
@@ -321,12 +303,7 @@ template <typename T, bool = (is_trivially_copy_constructible<T>::value) &&
(is_trivially_move_constructible<T>::value) &&
std::is_trivially_destructible<T>::value>
class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
- friend class SmallVectorTemplateCommon<T>;
-
protected:
- static constexpr bool TakesParamByValue = false;
- using ValueParamT = const T &;
-
SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
static void destroy_range(T *S, T *E) {
@@ -356,31 +333,20 @@ class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
/// element, or MinSize more elements if specified.
void grow(size_t MinSize = 0);
- /// Reserve enough space to add one element, and return the updated element
- /// pointer in case it was a reference to the storage.
- const T *reserveForAndGetAddress(const T &Elt, size_t N = 1) {
- return this->reserveForAndGetAddressImpl(this, Elt, N);
- }
-
- /// Reserve enough space to add one element, and return the updated element
- /// pointer in case it was a reference to the storage.
- T *reserveForAndGetAddress(T &Elt, size_t N = 1) {
- return const_cast<T *>(this->reserveForAndGetAddressImpl(this, Elt, N));
- }
-
- static T &&forward_value_param(T &&V) { return std::move(V); }
- static const T &forward_value_param(const T &V) { return V; }
-
public:
void push_back(const T &Elt) {
- const T *EltPtr = reserveForAndGetAddress(Elt);
- ::new ((void *)this->end()) T(*EltPtr);
+ this->assertSafeToAdd(&Elt);
+ if (LLVM_UNLIKELY(this->size() >= this->capacity()))
+ this->grow();
+ ::new ((void*) this->end()) T(Elt);
this->set_size(this->size() + 1);
}
void push_back(T &&Elt) {
- T *EltPtr = reserveForAndGetAddress(Elt);
- ::new ((void *)this->end()) T(::std::move(*EltPtr));
+ this->assertSafeToAdd(&Elt);
+ if (LLVM_UNLIKELY(this->size() >= this->capacity()))
+ this->grow();
+ ::new ((void*) this->end()) T(::std::move(Elt));
this->set_size(this->size() + 1);
}
@@ -430,18 +396,7 @@ void SmallVectorTemplateBase<T, TriviallyCopyable>::grow(size_t MinSize) {
/// skipping destruction.
template <typename T>
class SmallVectorTemplateBase<T, true> : public SmallVectorTemplateCommon<T> {
- friend class SmallVectorTemplateCommon<T>;
-
protected:
- /// True if it's cheap enough to take parameters by value. Doing so avoids
- /// overhead related to mitigations for reference invalidation.
- static constexpr bool TakesParamByValue = sizeof(T) <= 2 * sizeof(void *);
-
- /// Either const T& or T, depending on whether it's cheap enough to take
- /// parameters by value.
- using ValueParamT =
- typename std::conditional<TakesParamByValue, T, const T &>::type;
-
SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
// No need to do a destroy loop for POD's.
@@ -482,25 +437,12 @@ class SmallVectorTemplateBase<T, true> : public SmallVectorTemplateCommon<T> {
/// least one more element or MinSize if specified.
void grow(size_t MinSize = 0) { this->grow_pod(MinSize, sizeof(T)); }
- /// Reserve enough space to add one element, and return the updated element
- /// pointer in case it was a reference to the storage.
- const T *reserveForAndGetAddress(const T &Elt, size_t N = 1) {
- return this->reserveForAndGetAddressImpl(this, Elt, N);
- }
-
- /// Reserve enough space to add one element, and return the updated element
- /// pointer in case it was a reference to the storage.
- T *reserveForAndGetAddress(T &Elt, size_t N = 1) {
- return const_cast<T *>(this->reserveForAndGetAddressImpl(this, Elt, N));
- }
-
- /// Copy \p V or return a reference, depending on \a ValueParamT.
- static ValueParamT forward_value_param(ValueParamT V) { return V; }
-
public:
- void push_back(ValueParamT Elt) {
- const T *EltPtr = reserveForAndGetAddress(Elt);
- memcpy(reinterpret_cast<void *>(this->end()), EltPtr, sizeof(T));
+ void push_back(const T &Elt) {
+ this->assertSafeToAdd(&Elt);
+ if (LLVM_UNLIKELY(this->size() >= this->capacity()))
+ this->grow();
+ memcpy(reinterpret_cast<void *>(this->end()), &Elt, sizeof(T));
this->set_size(this->size() + 1);
}
@@ -520,9 +462,6 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
using size_type = typename SuperClass::size_type;
protected:
- using SmallVectorTemplateBase<T>::TakesParamByValue;
- using ValueParamT = typename SuperClass::ValueParamT;
-
// Default ctor - Initialize to empty.
explicit SmallVectorImpl(unsigned N)
: SmallVectorTemplateBase<T>(N) {}
@@ -563,7 +502,7 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
/// Like resize, but \ref T is POD, the new values won't be initialized.
void resize_for_overwrite(size_type N) { resizeImpl<true>(N); }
- void resize(size_type N, ValueParamT NV) {
+ void resize(size_type N, const T &NV) {
if (N == this->size())
return;
@@ -572,8 +511,11 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
return;
}
- // N > this->size(). Defer to append.
- this->append(N - this->size(), NV);
+ this->assertSafeToReferenceAfterResize(&NV, N);
+ if (this->capacity() < N)
+ this->grow(N);
+ std::uninitialized_fill(this->end(), this->begin() + N, NV);
+ this->set_size(N);
}
void reserve(size_type N) {
@@ -609,9 +551,12 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
}
/// Append \p NumInputs copies of \p Elt to the end.
- void append(size_type NumInputs, ValueParamT Elt) {
- const T *EltPtr = this->reserveForAndGetAddress(Elt, NumInputs);
- std::uninitialized_fill_n(this->end(), NumInputs, *EltPtr);
+ void append(size_type NumInputs, const T &Elt) {
+ this->assertSafeToAdd(&Elt, NumInputs);
+ if (NumInputs > this->capacity() - this->size())
+ this->grow(this->size()+NumInputs);
+
+ std::uninitialized_fill_n(this->end(), NumInputs, Elt);
this->set_size(this->size() + NumInputs);
}
@@ -677,12 +622,6 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
private:
template <class ArgType> iterator insert_one_impl(iterator I, ArgType &&Elt) {
- // Callers ensure that ArgType is derived from T.
- static_assert(
- std::is_same<std::remove_const_t<std::remove_reference_t<ArgType>>,
- T>::value,
- "ArgType must be derived from T!");
-
if (I == this->end()) { // Important special case for empty vector.
this->push_back(::std::forward<ArgType>(Elt));
return this->end()-1;
@@ -690,11 +629,14 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.");
- // Grow if necessary.
- size_t Index = I - this->begin();
- std::remove_reference_t<ArgType> *EltPtr =
- this->reserveForAndGetAddress(Elt);
- I = this->begin() + Index;
+ // Check that adding an element won't invalidate Elt.
+ this->assertSafeToAdd(&Elt);
+
+ if (this->size() >= this->capacity()) {
+ size_t EltNo = I-this->begin();
+ this->grow();
+ I = this->begin()+EltNo;
+ }
::new ((void*) this->end()) T(::std::move(this->back()));
// Push everything else over.
@@ -702,10 +644,9 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
this->set_size(this->size() + 1);
// If we just moved the element we're inserting, be sure to update
- // the reference (never happens if TakesParamByValue).
- static_assert(!TakesParamByValue || std::is_same<ArgType, T>::value,
- "ArgType must be 'T' when taking by value!");
- if (!TakesParamByValue && this->isReferenceToRange(EltPtr, I, this->end()))
+ // the reference.
+ std::remove_reference_t<ArgType> *EltPtr = &Elt;
+ if (this->isReferenceToRange(EltPtr, I, this->end()))
++EltPtr;
*I = ::std::forward<ArgType>(*EltPtr);
@@ -714,14 +655,12 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
public:
iterator insert(iterator I, T &&Elt) {
- return insert_one_impl(I, this->forward_value_param(std::move(Elt)));
+ return insert_one_impl(I, std::move(Elt));
}
- iterator insert(iterator I, const T &Elt) {
- return insert_one_impl(I, this->forward_value_param(Elt));
- }
+ iterator insert(iterator I, const T &Elt) { return insert_one_impl(I, Elt); }
- iterator insert(iterator I, size_type NumToInsert, ValueParamT Elt) {
+ iterator insert(iterator I, size_type NumToInsert, const T &Elt) {
// Convert iterator to elt# to avoid invalidating iterator when we reserve()
size_t InsertElt = I - this->begin();
@@ -732,9 +671,11 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.");
- // Ensure there is enough space, and get the (maybe updated) address of
- // Elt.
- const T *EltPtr = this->reserveForAndGetAddress(Elt, NumToInsert);
+ // Check that adding NumToInsert elements won't invalidate Elt.
+ this->assertSafeToAdd(&Elt, NumToInsert);
+
+ // Ensure there is enough space.
+ reserve(this->size() + NumToInsert);
// Uninvalidate the iterator.
I = this->begin()+InsertElt;
@@ -751,12 +692,7 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
// Copy the existing elements that get replaced.
std::move_backward(I, OldEnd-NumToInsert, OldEnd);
- // If we just moved the element we're inserting, be sure to update
- // the reference (never happens if TakesParamByValue).
- if (!TakesParamByValue && I <= EltPtr && EltPtr < this->end())
- EltPtr += NumToInsert;
-
- std::fill_n(I, NumToInsert, *EltPtr);
+ std::fill_n(I, NumToInsert, Elt);
return I;
}
@@ -769,16 +705,11 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
size_t NumOverwritten = OldEnd-I;
this->uninitialized_move(I, OldEnd, this->end()-NumOverwritten);
- // If we just moved the element we're inserting, be sure to update
- // the reference (never happens if TakesParamByValue).
- if (!TakesParamByValue && I <= EltPtr && EltPtr < this->end())
- EltPtr += NumToInsert;
-
// Replace the overwritten part.
- std::fill_n(I, NumOverwritten, *EltPtr);
+ std::fill_n(I, NumOverwritten, Elt);
// Insert the non-overwritten middle part.
- std::uninitialized_fill_n(OldEnd, NumToInsert - NumOverwritten, *EltPtr);
+ std::uninitialized_fill_n(OldEnd, NumToInsert-NumOverwritten, Elt);
return I;
}
diff --git a/llvm/unittests/ADT/SmallVectorTest.cpp b/llvm/unittests/ADT/SmallVectorTest.cpp
index 1f6c7db99fa8..d97ab577524f 100644
--- a/llvm/unittests/ADT/SmallVectorTest.cpp
+++ b/llvm/unittests/ADT/SmallVectorTest.cpp
@@ -53,7 +53,6 @@ class Constructable {
Constructable(Constructable && src) : constructed(true) {
value = src.value;
- src.value = 0;
++numConstructorCalls;
++numMoveConstructorCalls;
}
@@ -75,7 +74,6 @@ class Constructable {
Constructable & operator=(Constructable && src) {
EXPECT_TRUE(constructed);
value = src.value;
- src.value = 0;
++numAssignmentCalls;
++numMoveAssignmentCalls;
return *this;
@@ -1058,16 +1056,11 @@ class SmallVectorReferenceInvalidationTest : public SmallVectorTestBase {
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});
}
};
@@ -1081,84 +1074,39 @@ 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) {
auto &V = this->V;
(void)V;
int N = this->NumBuiltinElts(V);
- V.resize(N + 1, V.back());
- EXPECT_EQ(N, V.back());
-
- // Resize to add enough elements that V will grow again. If reference
- // invalidation breaks in the future, sanitizers should be able to catch a
- // use-after-free here.
- V.resize(V.capacity() + 1, V.front());
- EXPECT_EQ(1, V.back());
+#if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+ EXPECT_DEATH(V.resize(N + 1, V.back()), this->AssertionMessage);
+#endif
+
+ // No assertion when shrinking, since the parameter isn't accessed.
+ V.resize(N - 1, V.back());
}
TYPED_TEST(SmallVectorReferenceInvalidationTest, Append) {
auto &V = this->V;
(void)V;
- V.append(1, V.back());
- int N = this->NumBuiltinElts(V);
- EXPECT_EQ(N, V[N - 1]);
-
- // Append enough more elements that V will grow again. This tests growing
- // when already in large mode.
- //
- // If reference invalidation breaks in the future, sanitizers should be able
- // to catch a use-after-free here.
- V.append(V.capacity() - V.size() + 1, V.front());
- EXPECT_EQ(1, V.back());
+#if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+ EXPECT_DEATH(V.append(1, V.back()), this->AssertionMessage);
+#endif
}
TYPED_TEST(SmallVectorReferenceInvalidationTest, AppendRange) {
@@ -1202,72 +1150,28 @@ 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) {
auto &V = this->V;
(void)V;
-
- // Cover NumToInsert <= this->end() - I.
- V.insert(V.begin() + 1, 1, V.back());
- int N = this->NumBuiltinElts(V);
- EXPECT_EQ(N, V[1]);
-
- // Cover NumToInsert > this->end() - I, inserting enough elements that V will
- // also grow again; V.capacity() will be more elements than necessary but
- // it's a simple way to cover both conditions.
- //
- // If reference invalidation breaks in the future, sanitizers should be able
- // to catch a use-after-free here.
- V.insert(V.begin(), V.capacity(), V.front());
- EXPECT_EQ(1, V.front());
+#if !defined(NDEBUG) && GTEST_HAS_DEATH_TEST
+ EXPECT_DEATH(V.insert(V.begin(), 2, V.back()), this->AssertionMessage);
+#endif
}
TYPED_TEST(SmallVectorReferenceInvalidationTest, InsertRange) {
More information about the llvm-branch-commits
mailing list