Replace llvm::isPodLike<...> by llvm::is_trivially_copyable<...>

As noted in https://bugs.llvm.org/show_bug.cgi?id=36651, the specialization for
isPodLike<std::pair<...>> did not match the expectation of
std::is_trivially_copyable which makes the memcpy optimization invalid.

This patch renames the llvm::isPodLike trait into llvm::is_trivially_copyable.
Unfortunately std::is_trivially_copyable is not portable across compiler / STL
versions. So a portable version is provided too.

Note that the following specialization were invalid:

    std::pair<T0, T1>
    llvm::Optional<T>

Tests have been added to assert that former specialization are respected by the
standard usage of llvm::is_trivially_copyable, and that when a decent version
of std::is_trivially_copyable is available, llvm::is_trivially_copyable is
compared to std::is_trivially_copyable.

As of this patch, llvm::Optional is no longer considered trivially copyable,
even if T is. This is to be fixed in a later patch, as it has impact on a
long-running bug (see r347004)

Note that GCC warns about this UB, but this got silented by https://reviews.llvm.org/D50296.

Differential Revision: https://reviews.llvm.org/D54472

llvm-svn: 351701

Author: serge-sans-paille-qb

clang/include/clang/AST/BaseSubobject.h

@@ -80,11 +80,6 @@ template<> struct DenseMapInfo<clang::BaseSubobject> {
   }
 };
 
-// It's OK to treat BaseSubobject as a POD type.
-template <> struct isPodLike<clang::BaseSubobject> {
-  static const bool value = true;
-};
-
 } // namespace llvm
 
 #endif // LLVM_CLANG_AST_BASESUBOBJECT_H

clang/include/clang/AST/CharUnits.h

@@ -237,10 +237,6 @@ template<> struct DenseMapInfo<clang::CharUnits> {
   }
 };
 
-template <> struct isPodLike<clang::CharUnits> {
-  static const bool value = true;
-};
-
 } // end namespace llvm
 
 #endif // LLVM_CLANG_AST_CHARUNITS_H

clang/include/clang/AST/DeclAccessPair.h

@@ -60,12 +60,4 @@ class DeclAccessPair {
 };
 }
 
-// Take a moment to tell SmallVector that DeclAccessPair is POD.
-namespace llvm {
-template<typename> struct isPodLike;
-template<> struct isPodLike<clang::DeclAccessPair> {
-   static const bool value = true;
-};
-}
-
 #endif

clang/include/clang/AST/DeclarationName.h

@@ -861,9 +861,6 @@ struct DenseMapInfo<clang::DeclarationName> {
   }
 };
 
-template <>
-struct isPodLike<clang::DeclarationName> { static const bool value = true; };
-
 } // namespace llvm
 
 #endif // LLVM_CLANG_AST_DECLARATIONNAME_H

clang/include/clang/AST/ExprObjC.h

@@ -255,12 +255,6 @@ struct ObjCDictionaryElement {
 
 } // namespace clang
 
-namespace llvm {
-
-template <> struct isPodLike<clang::ObjCDictionaryElement> : std::true_type {};
-
-} // namespace llvm
-
 namespace clang {
 
 /// Internal struct for storing Key/value pair.

clang/include/clang/AST/GlobalDecl.h

@@ -139,13 +139,6 @@ namespace llvm {
     }
   };
 
-  // GlobalDecl isn't *technically* a POD type. However, its copy constructor,
-  // copy assignment operator, and destructor are all trivial.
-  template <>
-  struct isPodLike<clang::GlobalDecl> {
-    static const bool value = true;
-  };
-
 } // namespace llvm
 
 #endif // LLVM_CLANG_AST_GLOBALDECL_H

clang/include/clang/AST/Type.h

@@ -94,9 +94,6 @@ namespace llvm {
     enum { NumLowBitsAvailable = clang::TypeAlignmentInBits };
   };
 
-  template <>
-  struct isPodLike<clang::QualType> { static const bool value = true; };
-
 } // namespace llvm
 
 namespace clang {

clang/include/clang/Analysis/ProgramPoint.h

@@ -777,9 +777,6 @@ static bool isEqual(const clang::ProgramPoint &L,
 
 };
 
-template <>
-struct isPodLike<clang::ProgramPoint> { static const bool value = true; };
-
 } // end namespace llvm
 
 #endif

clang/include/clang/Basic/IdentifierTable.h

@@ -938,9 +938,6 @@ struct DenseMapInfo<clang::Selector> {
   }
 };
 
-template <>
-struct isPodLike<clang::Selector> { static const bool value = true; };
-
 template<>
 struct PointerLikeTypeTraits<clang::Selector> {
   static const void *getAsVoidPointer(clang::Selector P) {

clang/include/clang/Basic/SourceLocation.h

@@ -25,7 +25,6 @@
 namespace llvm {
 
 template <typename T> struct DenseMapInfo;
-template <typename T> struct isPodLike;
 
 } // namespace llvm
 
@@ -457,11 +456,6 @@ namespace llvm {
     }
   };
 
-  template <>
-  struct isPodLike<clang::SourceLocation> { static const bool value = true; };
-  template <>
-  struct isPodLike<clang::FileID> { static const bool value = true; };
-
   // Teach SmallPtrSet how to handle SourceLocation.
   template<>
   struct PointerLikeTypeTraits<clang::SourceLocation> {

clang/include/clang/Lex/Token.h

@@ -328,9 +328,4 @@ struct PPConditionalInfo {
 
 } // end namespace clang
 
-namespace llvm {
-  template <>
-  struct isPodLike<clang::Token> { static const bool value = true; };
-} // end namespace llvm
-
 #endif // LLVM_CLANG_LEX_TOKEN_H

clang/include/clang/Sema/CodeCompleteConsumer.h

@@ -655,14 +655,6 @@ class CodeCompletionTUInfo {
 
 } // namespace clang
 
-namespace llvm {
-
-template <> struct isPodLike<clang::CodeCompletionString::Chunk> {
-  static const bool value = true;
-};
-
-} // namespace llvm
-
 namespace clang {
 
 /// A builder class used to construct new code-completion strings.

clang/include/clang/Sema/Ownership.h

@@ -128,9 +128,6 @@ namespace llvm {
     }
   };
 
-  template <class T>
-  struct isPodLike<clang::OpaquePtr<T>> { static const bool value = true; };
-
 } // namespace llvm
 
 namespace clang {

clang/include/clang/StaticAnalyzer/Core/PathSensitive/SVals.h

@@ -667,13 +667,4 @@ class ConcreteInt : public Loc {
 
 } // namespace clang
 
-namespace llvm {
-
-template <typename T> struct isPodLike;
-template <> struct isPodLike<clang::ento::SVal> {
-  static const bool value = true;
-};
-
-} // namespace llvm
-
 #endif // LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_SVALS_H

clang/lib/AST/VTableBuilder.cpp

@@ -846,6 +846,8 @@ class ItaniumVTableBuilder {
       : BaseOffset(CharUnits::Zero()),
       BaseOffsetInLayoutClass(CharUnits::Zero()),
       VTableIndex(0) { }
+
+    MethodInfo(MethodInfo const&) = default;
   };
 
   typedef llvm::DenseMap<const CXXMethodDecl *, MethodInfo> MethodInfoMapTy;

clang/lib/Sema/SemaChecking.cpp

@@ -11662,12 +11662,12 @@ class SequenceChecker : public EvaluatedExprVisitor<SequenceChecker> {
     class Seq {
       friend class SequenceTree;
 
-      unsigned Index = 0;
+      unsigned Index;
 
       explicit Seq(unsigned N) : Index(N) {}
 
     public:
-      Seq() = default;
+      Seq() : Index(0) {}
     };
 
     SequenceTree() { Values.push_back(Value(0)); }

clang/lib/StaticAnalyzer/Core/RegionStore.cpp

@@ -130,10 +130,6 @@ namespace llvm {
     return os;
   }
 
-  template <typename T> struct isPodLike;
-  template <> struct isPodLike<BindingKey> {
-    static const bool value = true;
-  };
 } // end llvm namespace
 
 #ifndef NDEBUG

clang/test/Analysis/llvm-conventions.cpp

@@ -152,8 +152,6 @@ inline bool operator>(StringRef LHS, StringRef RHS);
 inline bool operator>=(StringRef LHS, StringRef RHS);
 inline std::string &operator+=(std::string &buffer, StringRef string);
 hash_code hash_value(StringRef S);
-template <typename T> struct isPodLike;
-template <> struct isPodLike<StringRef> { static const bool value = true; };
 
 } // end of namespace llvm
 

clang/tools/libclang/Indexing.cpp

@@ -93,9 +93,6 @@ typedef llvm::DenseSet<PPRegion> PPRegionSetTy;
 } // end anonymous namespace
 
 namespace llvm {
-  template <> struct isPodLike<PPRegion> {
-    static const bool value = true;
-  };
 
   template <>
   struct DenseMapInfo<PPRegion> {

llvm/docs/ProgrammersManual.rst

@@ -1456,7 +1456,7 @@ SmallVector has grown a few other minor advantages over std::vector, causing
 #. std::vector is exception-safe, and some implementations have pessimizations
    that copy elements when SmallVector would move them.
 
-#. SmallVector understands ``isPodLike<Type>`` and uses realloc aggressively.
+#. SmallVector understands ``llvm::is_trivially_copyable<Type>`` and uses realloc aggressively.
 
 #. Many LLVM APIs take a SmallVectorImpl as an out parameter (see the note
    below).

llvm/include/llvm/ADT/ArrayRef.h

@@ -525,12 +525,6 @@ namespace llvm {
 
   /// @}
 
-  // ArrayRefs can be treated like a POD type.
-  template <typename T> struct isPodLike;
-  template <typename T> struct isPodLike<ArrayRef<T>> {
-    static const bool value = true;
-  };
-
   template <typename T> hash_code hash_value(ArrayRef<T> S) {
     return hash_combine_range(S.begin(), S.end());
   }

llvm/include/llvm/ADT/DenseMap.h

@@ -145,7 +145,8 @@ class DenseMapBase : public DebugEpochBase {
     }
 
     const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
-    if (isPodLike<KeyT>::value && isPodLike<ValueT>::value) {
+    if (is_trivially_copyable<KeyT>::value &&
+        is_trivially_copyable<ValueT>::value) {
       // Use a simpler loop when these are trivial types.
       for (BucketT *P = getBuckets(), *E = getBucketsEnd(); P != E; ++P)
         P->getFirst() = EmptyKey;
@@ -421,7 +422,8 @@ class DenseMapBase : public DebugEpochBase {
     setNumEntries(other.getNumEntries());
     setNumTombstones(other.getNumTombstones());
 
-    if (isPodLike<KeyT>::value && isPodLike<ValueT>::value)
+    if (is_trivially_copyable<KeyT>::value &&
+        is_trivially_copyable<ValueT>::value)
       memcpy(reinterpret_cast<void *>(getBuckets()), other.getBuckets(),
              getNumBuckets() * sizeof(BucketT));
     else

llvm/include/llvm/ADT/ImmutableList.h

@@ -241,10 +241,6 @@ template<typename T> struct DenseMapInfo<ImmutableList<T>> {
   }
 };
 
-template <typename T> struct isPodLike;
-template <typename T>
-struct isPodLike<ImmutableList<T>> { static const bool value = true; };
-
 } // end namespace llvm
 
 #endif // LLVM_ADT_IMMUTABLELIST_H

llvm/include/llvm/ADT/Optional.h

@@ -30,7 +30,7 @@ class raw_ostream;
 
 namespace optional_detail {
 /// Storage for any type.
-template <typename T, bool = isPodLike<T>::value> struct OptionalStorage {
+template <typename T, bool = is_trivially_copyable<T>::value> struct OptionalStorage {
   AlignedCharArrayUnion<T> storage;
   bool hasVal = false;
 
@@ -185,11 +185,6 @@ template <typename T> class Optional {
 #endif
 };
 
-template <typename T> struct isPodLike<Optional<T>> {
-  // An Optional<T> is pod-like if T is.
-  static const bool value = isPodLike<T>::value;
-};
-
 template <typename T, typename U>
 bool operator==(const Optional<T> &X, const Optional<U> &Y) {
   if (X && Y)

llvm/include/llvm/ADT/PointerIntPair.h

@@ -175,12 +175,6 @@ struct PointerIntPairInfo {
   }
 };
 
-template <typename T> struct isPodLike;
-template <typename PointerTy, unsigned IntBits, typename IntType>
-struct isPodLike<PointerIntPair<PointerTy, IntBits, IntType>> {
-  static const bool value = true;
-};
-
 // Provide specialization of DenseMapInfo for PointerIntPair.
 template <typename PointerTy, unsigned IntBits, typename IntType>
 struct DenseMapInfo<PointerIntPair<PointerTy, IntBits, IntType>> {

llvm/include/llvm/ADT/SmallVector.h

@@ -179,9 +179,9 @@ class SmallVectorTemplateCommon : public SmallVectorBase {
   }
 };
 
-/// SmallVectorTemplateBase<isPodLike = false> - This is where we put method
+/// SmallVectorTemplateBase<TriviallyCopyable = false> - This is where we put method
 /// implementations that are designed to work with non-POD-like T's.
-template <typename T, bool = isPodLike<T>::value>
+template <typename T, bool = is_trivially_copyable<T>::value>
 class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
 protected:
   SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
@@ -235,8 +235,8 @@ class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
 };
 
 // Define this out-of-line to dissuade the C++ compiler from inlining it.
-template <typename T, bool isPodLike>
-void SmallVectorTemplateBase<T, isPodLike>::grow(size_t MinSize) {
+template <typename T, bool TriviallyCopyable>
+void SmallVectorTemplateBase<T, TriviallyCopyable>::grow(size_t MinSize) {
   if (MinSize > UINT32_MAX)
     report_bad_alloc_error("SmallVector capacity overflow during allocation");
 
@@ -259,9 +259,8 @@ void SmallVectorTemplateBase<T, isPodLike>::grow(size_t MinSize) {
   this->Capacity = NewCapacity;
 }
 
-
-/// SmallVectorTemplateBase<isPodLike = true> - This is where we put method
-/// implementations that are designed to work with POD-like T's.
+/// SmallVectorTemplateBase<TriviallyCopyable = true> - This is where we put
+/// method implementations that are designed to work with POD-like T's.
 template <typename T>
 class SmallVectorTemplateBase<T, true> : public SmallVectorTemplateCommon<T> {
 protected:
@@ -330,7 +329,7 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
 protected:
   // Default ctor - Initialize to empty.
   explicit SmallVectorImpl(unsigned N)
-      : SmallVectorTemplateBase<T, isPodLike<T>::value>(N) {}
+      : SmallVectorTemplateBase<T>(N) {}
 
 public:
   SmallVectorImpl(const SmallVectorImpl &) = delete;

llvm/include/llvm/ADT/StringRef.h

@@ -927,10 +927,6 @@ namespace llvm {
   LLVM_NODISCARD
   hash_code hash_value(StringRef S);
 
-  // StringRefs can be treated like a POD type.
-  template <typename T> struct isPodLike;
-  template <> struct isPodLike<StringRef> { static const bool value = true; };
-
 } // end namespace llvm
 
 #endif // LLVM_ADT_STRINGREF_H

llvm/include/llvm/ADT/bit.h

@@ -40,11 +40,11 @@ template <typename To, typename From
           , typename = typename std::enable_if<__is_trivially_copyable(To)>::type
           , typename = typename std::enable_if<__is_trivially_copyable(From)>::type
 #else
-  // This case is GCC 4.x. clang with libc++ or libstdc++ never get here. Unlike
-  // llvm/Support/type_traits.h's isPodLike we don't want to provide a
-  // good-enough answer here: developers in that configuration will hit
-  // compilation failures on the bots instead of locally. That's acceptable
-  // because it's very few developers, and only until we move past C++11.
+// This case is GCC 4.x. clang with libc++ or libstdc++ never get here. Unlike
+// llvm/Support/type_traits.h's is_trivially_copyable we don't want to
+// provide a good-enough answer here: developers in that configuration will hit
+// compilation failures on the bots instead of locally. That's acceptable
+// because it's very few developers, and only until we move past C++11.
 #endif
 >
 inline To bit_cast(const From &from) noexcept {