diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
@@ -55,6 +55,7 @@
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/SemaBase.h"
 #include "clang/Sema/SemaConcept.h"
+#include "clang/Sema/SemaDiagnostic.h"
 #include "clang/Sema/TypoCorrection.h"
 #include "clang/Sema/Weak.h"
 #include "llvm/ADT/ArrayRef.h"
@@ -3427,7 +3428,8 @@ class Sema final : public SemaBase {
       bool ConstexprSupported, bool CLinkageMayDiffer);
 
   /// type checking declaration initializers (C99 6.7.8)
-  bool CheckForConstantInitializer(Expr *e, QualType t);
+  bool CheckForConstantInitializer(
+      Expr *Init, unsigned DiagID = diag::err_init_element_not_constant);
 
   QualType deduceVarTypeFromInitializer(VarDecl *VDecl, DeclarationName Name,
                                         QualType Type, TypeSourceInfo *TSI,

diff --git a/clang/include/clang/Serialization/ModuleFileExtension.h b/clang/include/clang/Serialization/ModuleFileExtension.h
@@ -9,7 +9,6 @@
 #ifndef LLVM_CLANG_SERIALIZATION_MODULEFILEEXTENSION_H
 #define LLVM_CLANG_SERIALIZATION_MODULEFILEEXTENSION_H
 
-#include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/Support/ExtensibleRTTI.h"
 #include "llvm/Support/HashBuilder.h"
 #include "llvm/Support/MD5.h"

diff --git a/clang/include/clang/Serialization/PCHContainerOperations.h b/clang/include/clang/Serialization/PCHContainerOperations.h
@@ -12,7 +12,7 @@
 #include "clang/Basic/Module.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
-#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/MemoryBufferRef.h"
 #include <memory>
 
 namespace llvm {

diff --git a/clang/lib/AST/Interp/ByteCodeExprGen.cpp b/clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -398,6 +398,35 @@ bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
     return true;
   }
 
+  case CK_VectorSplat: {
+    assert(!classify(CE->getType()));
+    assert(classify(SubExpr->getType()));
+    assert(CE->getType()->isVectorType());
+
+    if (DiscardResult)
+      return this->discard(SubExpr);
+
+    assert(Initializing); // FIXME: Not always correct.
+    const auto *VT = CE->getType()->getAs<VectorType>();
+    PrimType ElemT = classifyPrim(SubExpr);
+    unsigned ElemOffset = allocateLocalPrimitive(
+        SubExpr, ElemT, /*IsConst=*/true, /*IsExtended=*/false);
+
+    if (!this->visit(SubExpr))
+      return false;
+    if (!this->emitSetLocal(ElemT, ElemOffset, CE))
+      return false;
+
+    for (unsigned I = 0; I != VT->getNumElements(); ++I) {
+      if (!this->emitGetLocal(ElemT, ElemOffset, CE))
+        return false;
+      if (!this->emitInitElem(ElemT, I, CE))
+        return false;
+    }
+
+    return true;
+  }
+
   case CK_ToVoid:
     return discard(SubExpr);
 

diff --git a/clang/lib/AST/Interp/ByteCodeExprGen.h b/clang/lib/AST/Interp/ByteCodeExprGen.h
@@ -148,13 +148,20 @@ class ByteCodeExprGen : public ConstStmtVisitor<ByteCodeExprGen<Emitter>, bool>,
     return Ctx.classify(Ty);
   }
 
-  /// Classifies a known primitive type
+  /// Classifies a known primitive type.
   PrimType classifyPrim(QualType Ty) const {
     if (auto T = classify(Ty)) {
       return *T;
     }
     llvm_unreachable("not a primitive type");
   }
+  /// Classifies a known primitive expression.
+  PrimType classifyPrim(const Expr *E) const {
+    if (auto T = classify(E))
+      return *T;
+    llvm_unreachable("not a primitive type");
+  }
+
   /// Evaluates an expression and places the result on the stack. If the
   /// expression is of composite type, a local variable will be created
   /// and a pointer to said variable will be placed on the stack.

diff --git a/clang/lib/Analysis/FlowSensitive/ASTOps.cpp b/clang/lib/Analysis/FlowSensitive/ASTOps.cpp
@@ -0,0 +1,249 @@
+//===-- ASTOps.cc -------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  Operations on AST nodes that are used in flow-sensitive analysis.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/FlowSensitive/ASTOps.h"
+#include "clang/AST/ComputeDependence.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclBase.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/AST/Stmt.h"
+#include "clang/AST/Type.h"
+#include "clang/Analysis/FlowSensitive/StorageLocation.h"
+#include "clang/Basic/LLVM.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/STLExtras.h"
+#include <cassert>
+#include <iterator>
+#include <vector>
+
+#define DEBUG_TYPE "dataflow"
+
+namespace clang::dataflow {
+
+const Expr &ignoreCFGOmittedNodes(const Expr &E) {
+  const Expr *Current = &E;
+  if (auto *EWC = dyn_cast<ExprWithCleanups>(Current)) {
+    Current = EWC->getSubExpr();
+    assert(Current != nullptr);
+  }
+  Current = Current->IgnoreParens();
+  assert(Current != nullptr);
+  return *Current;
+}
+
+const Stmt &ignoreCFGOmittedNodes(const Stmt &S) {
+  if (auto *E = dyn_cast<Expr>(&S))
+    return ignoreCFGOmittedNodes(*E);
+  return S;
+}
+
+// FIXME: Does not precisely handle non-virtual diamond inheritance. A single
+// field decl will be modeled for all instances of the inherited field.
+static void getFieldsFromClassHierarchy(QualType Type, FieldSet &Fields) {
+  if (Type->isIncompleteType() || Type->isDependentType() ||
+      !Type->isRecordType())
+    return;
+
+  for (const FieldDecl *Field : Type->getAsRecordDecl()->fields())
+    Fields.insert(Field);
+  if (auto *CXXRecord = Type->getAsCXXRecordDecl())
+    for (const CXXBaseSpecifier &Base : CXXRecord->bases())
+      getFieldsFromClassHierarchy(Base.getType(), Fields);
+}
+
+/// Gets the set of all fields in the type.
+FieldSet getObjectFields(QualType Type) {
+  FieldSet Fields;
+  getFieldsFromClassHierarchy(Type, Fields);
+  return Fields;
+}
+
+bool containsSameFields(const FieldSet &Fields,
+                        const RecordStorageLocation::FieldToLoc &FieldLocs) {
+  if (Fields.size() != FieldLocs.size())
+    return false;
+  for ([[maybe_unused]] auto [Field, Loc] : FieldLocs)
+    if (!Fields.contains(cast_or_null<FieldDecl>(Field)))
+      return false;
+  return true;
+}
+
+/// Returns the fields of a `RecordDecl` that are initialized by an
+/// `InitListExpr`, in the order in which they appear in
+/// `InitListExpr::inits()`.
+/// `Init->getType()` must be a record type.
+static std::vector<const FieldDecl *>
+getFieldsForInitListExpr(const InitListExpr *InitList) {
+  const RecordDecl *RD = InitList->getType()->getAsRecordDecl();
+  assert(RD != nullptr);
+
+  std::vector<const FieldDecl *> Fields;
+
+  if (InitList->getType()->isUnionType()) {
+    Fields.push_back(InitList->getInitializedFieldInUnion());
+    return Fields;
+  }
+
+  // Unnamed bitfields are only used for padding and do not appear in
+  // `InitListExpr`'s inits. However, those fields do appear in `RecordDecl`'s
+  // field list, and we thus need to remove them before mapping inits to
+  // fields to avoid mapping inits to the wrongs fields.
+  llvm::copy_if(
+      RD->fields(), std::back_inserter(Fields),
+      [](const FieldDecl *Field) { return !Field->isUnnamedBitfield(); });
+  return Fields;
+}
+
+RecordInitListHelper::RecordInitListHelper(const InitListExpr *InitList) {
+  auto *RD = InitList->getType()->getAsCXXRecordDecl();
+  assert(RD != nullptr);
+
+  std::vector<const FieldDecl *> Fields = getFieldsForInitListExpr(InitList);
+  ArrayRef<Expr *> Inits = InitList->inits();
+
+  // Unions initialized with an empty initializer list need special treatment.
+  // For structs/classes initialized with an empty initializer list, Clang
+  // puts `ImplicitValueInitExpr`s in `InitListExpr::inits()`, but for unions,
+  // it doesn't do this -- so we create an `ImplicitValueInitExpr` ourselves.
+  SmallVector<Expr *> InitsForUnion;
+  if (InitList->getType()->isUnionType() && Inits.empty()) {
+    assert(Fields.size() == 1);
+    ImplicitValueInitForUnion.emplace(Fields.front()->getType());
+    InitsForUnion.push_back(&*ImplicitValueInitForUnion);
+    Inits = InitsForUnion;
+  }
+
+  size_t InitIdx = 0;
+
+  assert(Fields.size() + RD->getNumBases() == Inits.size());
+  for (const CXXBaseSpecifier &Base : RD->bases()) {
+    assert(InitIdx < Inits.size());
+    Expr *Init = Inits[InitIdx++];
+    BaseInits.emplace_back(&Base, Init);
+  }
+
+  assert(Fields.size() == Inits.size() - InitIdx);
+  for (const FieldDecl *Field : Fields) {
+    assert(InitIdx < Inits.size());
+    Expr *Init = Inits[InitIdx++];
+    FieldInits.emplace_back(Field, Init);
+  }
+}
+
+static void insertIfGlobal(const Decl &D,
+                           llvm::DenseSet<const VarDecl *> &Globals) {
+  if (auto *V = dyn_cast<VarDecl>(&D))
+    if (V->hasGlobalStorage())
+      Globals.insert(V);
+}
+
+static void insertIfFunction(const Decl &D,
+                             llvm::DenseSet<const FunctionDecl *> &Funcs) {
+  if (auto *FD = dyn_cast<FunctionDecl>(&D))
+    Funcs.insert(FD);
+}
+
+static MemberExpr *getMemberForAccessor(const CXXMemberCallExpr &C) {
+  // Use getCalleeDecl instead of getMethodDecl in order to handle
+  // pointer-to-member calls.
+  const auto *MethodDecl = dyn_cast_or_null<CXXMethodDecl>(C.getCalleeDecl());
+  if (!MethodDecl)
+    return nullptr;
+  auto *Body = dyn_cast_or_null<CompoundStmt>(MethodDecl->getBody());
+  if (!Body || Body->size() != 1)
+    return nullptr;
+  if (auto *RS = dyn_cast<ReturnStmt>(*Body->body_begin()))
+    if (auto *Return = RS->getRetValue())
+      return dyn_cast<MemberExpr>(Return->IgnoreParenImpCasts());
+  return nullptr;
+}
+
+static void getReferencedDecls(const Decl &D, ReferencedDecls &Referenced) {
+  insertIfGlobal(D, Referenced.Globals);
+  insertIfFunction(D, Referenced.Functions);
+  if (const auto *Decomp = dyn_cast<DecompositionDecl>(&D))
+    for (const auto *B : Decomp->bindings())
+      if (auto *ME = dyn_cast_or_null<MemberExpr>(B->getBinding()))
+        // FIXME: should we be using `E->getFoundDecl()`?
+        if (const auto *FD = dyn_cast<FieldDecl>(ME->getMemberDecl()))
+          Referenced.Fields.insert(FD);
+}
+
+/// Traverses `S` and inserts into `Referenced` any declarations that are
+/// declared in or referenced from sub-statements.
+static void getReferencedDecls(const Stmt &S, ReferencedDecls &Referenced) {
+  for (auto *Child : S.children())
+    if (Child != nullptr)
+      getReferencedDecls(*Child, Referenced);
+  if (const auto *DefaultArg = dyn_cast<CXXDefaultArgExpr>(&S))
+    getReferencedDecls(*DefaultArg->getExpr(), Referenced);
+  if (const auto *DefaultInit = dyn_cast<CXXDefaultInitExpr>(&S))
+    getReferencedDecls(*DefaultInit->getExpr(), Referenced);
+
+  if (auto *DS = dyn_cast<DeclStmt>(&S)) {
+    if (DS->isSingleDecl())
+      getReferencedDecls(*DS->getSingleDecl(), Referenced);
+    else
+      for (auto *D : DS->getDeclGroup())
+        getReferencedDecls(*D, Referenced);
+  } else if (auto *E = dyn_cast<DeclRefExpr>(&S)) {
+    insertIfGlobal(*E->getDecl(), Referenced.Globals);
+    insertIfFunction(*E->getDecl(), Referenced.Functions);
+  } else if (const auto *C = dyn_cast<CXXMemberCallExpr>(&S)) {
+    // If this is a method that returns a member variable but does nothing else,
+    // model the field of the return value.
+    if (MemberExpr *E = getMemberForAccessor(*C))
+      if (const auto *FD = dyn_cast<FieldDecl>(E->getMemberDecl()))
+        Referenced.Fields.insert(FD);
+  } else if (auto *E = dyn_cast<MemberExpr>(&S)) {
+    // FIXME: should we be using `E->getFoundDecl()`?
+    const ValueDecl *VD = E->getMemberDecl();
+    insertIfGlobal(*VD, Referenced.Globals);
+    insertIfFunction(*VD, Referenced.Functions);
+    if (const auto *FD = dyn_cast<FieldDecl>(VD))
+      Referenced.Fields.insert(FD);
+  } else if (auto *InitList = dyn_cast<InitListExpr>(&S)) {
+    if (InitList->getType()->isRecordType())
+      for (const auto *FD : getFieldsForInitListExpr(InitList))
+        Referenced.Fields.insert(FD);
+  }
+}
+
+ReferencedDecls getReferencedDecls(const FunctionDecl &FD) {
+  ReferencedDecls Result;
+  // Look for global variable and field references in the
+  // constructor-initializers.
+  if (const auto *CtorDecl = dyn_cast<CXXConstructorDecl>(&FD)) {
+    for (const auto *Init : CtorDecl->inits()) {
+      if (Init->isMemberInitializer()) {
+        Result.Fields.insert(Init->getMember());
+      } else if (Init->isIndirectMemberInitializer()) {
+        for (const auto *I : Init->getIndirectMember()->chain())
+          Result.Fields.insert(cast<FieldDecl>(I));
+      }
+      const Expr *E = Init->getInit();
+      assert(E != nullptr);
+      getReferencedDecls(*E, Result);
+    }
+    // Add all fields mentioned in default member initializers.
+    for (const FieldDecl *F : CtorDecl->getParent()->fields())
+      if (const auto *I = F->getInClassInitializer())
+        getReferencedDecls(*I, Result);
+  }
+  getReferencedDecls(*FD.getBody(), Result);
+
+  return Result;
+}
+
+} // namespace clang::dataflow
diff --git a/clang/lib/Analysis/FlowSensitive/CMakeLists.txt b/clang/lib/Analysis/FlowSensitive/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_clang_library(clangAnalysisFlowSensitive
   AdornedCFG.cpp
   Arena.cpp
+  ASTOps.cpp
   DataflowAnalysisContext.cpp
   DataflowEnvironment.cpp
   Formula.cpp

diff --git a/clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp b/clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp
@@ -14,6 +14,7 @@
 
 #include "clang/Analysis/FlowSensitive/DataflowAnalysisContext.h"
 #include "clang/AST/ExprCXX.h"
+#include "clang/Analysis/FlowSensitive/ASTOps.h"
 #include "clang/Analysis/FlowSensitive/DebugSupport.h"
 #include "clang/Analysis/FlowSensitive/Formula.h"
 #include "clang/Analysis/FlowSensitive/Logger.h"
@@ -359,55 +360,3 @@ DataflowAnalysisContext::~DataflowAnalysisContext() = default;
 
 } // namespace dataflow
 } // namespace clang
-
-using namespace clang;
-
-const Expr &clang::dataflow::ignoreCFGOmittedNodes(const Expr &E) {
-  const Expr *Current = &E;
-  if (auto *EWC = dyn_cast<ExprWithCleanups>(Current)) {
-    Current = EWC->getSubExpr();
-    assert(Current != nullptr);
-  }
-  Current = Current->IgnoreParens();
-  assert(Current != nullptr);
-  return *Current;
-}
-
-const Stmt &clang::dataflow::ignoreCFGOmittedNodes(const Stmt &S) {
-  if (auto *E = dyn_cast<Expr>(&S))
-    return ignoreCFGOmittedNodes(*E);
-  return S;
-}
-
-// FIXME: Does not precisely handle non-virtual diamond inheritance. A single
-// field decl will be modeled for all instances of the inherited field.
-static void getFieldsFromClassHierarchy(QualType Type,
-                                        clang::dataflow::FieldSet &Fields) {
-  if (Type->isIncompleteType() || Type->isDependentType() ||
-      !Type->isRecordType())
-    return;
-
-  for (const FieldDecl *Field : Type->getAsRecordDecl()->fields())
-    Fields.insert(Field);
-  if (auto *CXXRecord = Type->getAsCXXRecordDecl())
-    for (const CXXBaseSpecifier &Base : CXXRecord->bases())
-      getFieldsFromClassHierarchy(Base.getType(), Fields);
-}
-
-/// Gets the set of all fields in the type.
-clang::dataflow::FieldSet clang::dataflow::getObjectFields(QualType Type) {
-  FieldSet Fields;
-  getFieldsFromClassHierarchy(Type, Fields);
-  return Fields;
-}
-
-bool clang::dataflow::containsSameFields(
-    const clang::dataflow::FieldSet &Fields,
-    const clang::dataflow::RecordStorageLocation::FieldToLoc &FieldLocs) {
-  if (Fields.size() != FieldLocs.size())
-    return false;
-  for ([[maybe_unused]] auto [Field, Loc] : FieldLocs)
-    if (!Fields.contains(cast_or_null<FieldDecl>(Field)))
-      return false;
-  return true;
-}
diff --git a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
@@ -17,6 +17,7 @@
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/AST/Type.h"
+#include "clang/Analysis/FlowSensitive/ASTOps.h"
 #include "clang/Analysis/FlowSensitive/DataflowLattice.h"
 #include "clang/Analysis/FlowSensitive/Value.h"
 #include "llvm/ADT/DenseMap.h"
@@ -304,93 +305,6 @@ widenKeyToValueMap(const llvm::MapVector<Key, Value *> &CurMap,
   return WidenedMap;
 }
 
-/// Initializes a global storage value.
-static void insertIfGlobal(const Decl &D,
-                           llvm::DenseSet<const VarDecl *> &Vars) {
-  if (auto *V = dyn_cast<VarDecl>(&D))
-    if (V->hasGlobalStorage())
-      Vars.insert(V);
-}
-
-static void insertIfFunction(const Decl &D,
-                             llvm::DenseSet<const FunctionDecl *> &Funcs) {
-  if (auto *FD = dyn_cast<FunctionDecl>(&D))
-    Funcs.insert(FD);
-}
-
-static MemberExpr *getMemberForAccessor(const CXXMemberCallExpr &C) {
-  // Use getCalleeDecl instead of getMethodDecl in order to handle
-  // pointer-to-member calls.
-  const auto *MethodDecl = dyn_cast_or_null<CXXMethodDecl>(C.getCalleeDecl());
-  if (!MethodDecl)
-    return nullptr;
-  auto *Body = dyn_cast_or_null<CompoundStmt>(MethodDecl->getBody());
-  if (!Body || Body->size() != 1)
-    return nullptr;
-  if (auto *RS = dyn_cast<ReturnStmt>(*Body->body_begin()))
-    if (auto *Return = RS->getRetValue())
-      return dyn_cast<MemberExpr>(Return->IgnoreParenImpCasts());
-  return nullptr;
-}
-
-static void
-getFieldsGlobalsAndFuncs(const Decl &D, FieldSet &Fields,
-                         llvm::DenseSet<const VarDecl *> &Vars,
-                         llvm::DenseSet<const FunctionDecl *> &Funcs) {
-  insertIfGlobal(D, Vars);
-  insertIfFunction(D, Funcs);
-  if (const auto *Decomp = dyn_cast<DecompositionDecl>(&D))
-    for (const auto *B : Decomp->bindings())
-      if (auto *ME = dyn_cast_or_null<MemberExpr>(B->getBinding()))
-        // FIXME: should we be using `E->getFoundDecl()`?
-        if (const auto *FD = dyn_cast<FieldDecl>(ME->getMemberDecl()))
-          Fields.insert(FD);
-}
-
-/// Traverses `S` and inserts into `Fields`, `Vars` and `Funcs` any fields,
-/// global variables and functions that are declared in or referenced from
-/// sub-statements.
-static void
-getFieldsGlobalsAndFuncs(const Stmt &S, FieldSet &Fields,
-                         llvm::DenseSet<const VarDecl *> &Vars,
-                         llvm::DenseSet<const FunctionDecl *> &Funcs) {
-  for (auto *Child : S.children())
-    if (Child != nullptr)
-      getFieldsGlobalsAndFuncs(*Child, Fields, Vars, Funcs);
-  if (const auto *DefaultArg = dyn_cast<CXXDefaultArgExpr>(&S))
-    getFieldsGlobalsAndFuncs(*DefaultArg->getExpr(), Fields, Vars, Funcs);
-  if (const auto *DefaultInit = dyn_cast<CXXDefaultInitExpr>(&S))
-    getFieldsGlobalsAndFuncs(*DefaultInit->getExpr(), Fields, Vars, Funcs);
-
-  if (auto *DS = dyn_cast<DeclStmt>(&S)) {
-    if (DS->isSingleDecl())
-      getFieldsGlobalsAndFuncs(*DS->getSingleDecl(), Fields, Vars, Funcs);
-    else
-      for (auto *D : DS->getDeclGroup())
-        getFieldsGlobalsAndFuncs(*D, Fields, Vars, Funcs);
-  } else if (auto *E = dyn_cast<DeclRefExpr>(&S)) {
-    insertIfGlobal(*E->getDecl(), Vars);
-    insertIfFunction(*E->getDecl(), Funcs);
-  } else if (const auto *C = dyn_cast<CXXMemberCallExpr>(&S)) {
-    // If this is a method that returns a member variable but does nothing else,
-    // model the field of the return value.
-    if (MemberExpr *E = getMemberForAccessor(*C))
-      if (const auto *FD = dyn_cast<FieldDecl>(E->getMemberDecl()))
-        Fields.insert(FD);
-  } else if (auto *E = dyn_cast<MemberExpr>(&S)) {
-    // FIXME: should we be using `E->getFoundDecl()`?
-    const ValueDecl *VD = E->getMemberDecl();
-    insertIfGlobal(*VD, Vars);
-    insertIfFunction(*VD, Funcs);
-    if (const auto *FD = dyn_cast<FieldDecl>(VD))
-      Fields.insert(FD);
-  } else if (auto *InitList = dyn_cast<InitListExpr>(&S)) {
-    if (InitList->getType()->isRecordType())
-      for (const auto *FD : getFieldsForInitListExpr(InitList))
-        Fields.insert(FD);
-  }
-}
-
 namespace {
 
 // Visitor that builds a map from record prvalues to result objects.
@@ -653,36 +567,13 @@ void Environment::initialize() {
 void Environment::initFieldsGlobalsAndFuncs(const FunctionDecl *FuncDecl) {
   assert(FuncDecl->doesThisDeclarationHaveABody());
 
-  FieldSet Fields;
-  llvm::DenseSet<const VarDecl *> Vars;
-  llvm::DenseSet<const FunctionDecl *> Funcs;
-
-  // Look for global variable and field references in the
-  // constructor-initializers.
-  if (const auto *CtorDecl = dyn_cast<CXXConstructorDecl>(FuncDecl)) {
-    for (const auto *Init : CtorDecl->inits()) {
-      if (Init->isMemberInitializer()) {
-        Fields.insert(Init->getMember());
-      } else if (Init->isIndirectMemberInitializer()) {
-        for (const auto *I : Init->getIndirectMember()->chain())
-          Fields.insert(cast<FieldDecl>(I));
-      }
-      const Expr *E = Init->getInit();
-      assert(E != nullptr);
-      getFieldsGlobalsAndFuncs(*E, Fields, Vars, Funcs);
-    }
-    // Add all fields mentioned in default member initializers.
-    for (const FieldDecl *F : CtorDecl->getParent()->fields())
-      if (const auto *I = F->getInClassInitializer())
-          getFieldsGlobalsAndFuncs(*I, Fields, Vars, Funcs);
-  }
-  getFieldsGlobalsAndFuncs(*FuncDecl->getBody(), Fields, Vars, Funcs);
+  ReferencedDecls Referenced = getReferencedDecls(*FuncDecl);
 
   // These have to be added before the lines that follow to ensure that
   // `create*` work correctly for structs.
-  DACtx->addModeledFields(Fields);
+  DACtx->addModeledFields(Referenced.Fields);
 
-  for (const VarDecl *D : Vars) {
+  for (const VarDecl *D : Referenced.Globals) {
     if (getStorageLocation(*D) != nullptr)
       continue;
 
@@ -694,7 +585,7 @@ void Environment::initFieldsGlobalsAndFuncs(const FunctionDecl *FuncDecl) {
     setStorageLocation(*D, createObject(*D, nullptr));
   }
 
-  for (const FunctionDecl *FD : Funcs) {
+  for (const FunctionDecl *FD : Referenced.Functions) {
     if (getStorageLocation(*FD) != nullptr)
       continue;
     auto &Loc = createStorageLocation(*FD);
@@ -1354,64 +1245,6 @@ RecordStorageLocation *getBaseObjectLocation(const MemberExpr &ME,
   return Env.get<RecordStorageLocation>(*Base);
 }
 
-std::vector<const FieldDecl *>
-getFieldsForInitListExpr(const InitListExpr *InitList) {
-  const RecordDecl *RD = InitList->getType()->getAsRecordDecl();
-  assert(RD != nullptr);
-
-  std::vector<const FieldDecl *> Fields;
-
-  if (InitList->getType()->isUnionType()) {
-    Fields.push_back(InitList->getInitializedFieldInUnion());
-    return Fields;
-  }
-
-  // Unnamed bitfields are only used for padding and do not appear in
-  // `InitListExpr`'s inits. However, those fields do appear in `RecordDecl`'s
-  // field list, and we thus need to remove them before mapping inits to
-  // fields to avoid mapping inits to the wrongs fields.
-  llvm::copy_if(
-      RD->fields(), std::back_inserter(Fields),
-      [](const FieldDecl *Field) { return !Field->isUnnamedBitfield(); });
-  return Fields;
-}
-
-RecordInitListHelper::RecordInitListHelper(const InitListExpr *InitList) {
-  auto *RD = InitList->getType()->getAsCXXRecordDecl();
-  assert(RD != nullptr);
-
-  std::vector<const FieldDecl *> Fields = getFieldsForInitListExpr(InitList);
-  ArrayRef<Expr *> Inits = InitList->inits();
-
-  // Unions initialized with an empty initializer list need special treatment.
-  // For structs/classes initialized with an empty initializer list, Clang
-  // puts `ImplicitValueInitExpr`s in `InitListExpr::inits()`, but for unions,
-  // it doesn't do this -- so we create an `ImplicitValueInitExpr` ourselves.
-  SmallVector<Expr *> InitsForUnion;
-  if (InitList->getType()->isUnionType() && Inits.empty()) {
-    assert(Fields.size() == 1);
-    ImplicitValueInitForUnion.emplace(Fields.front()->getType());
-    InitsForUnion.push_back(&*ImplicitValueInitForUnion);
-    Inits = InitsForUnion;
-  }
-
-  size_t InitIdx = 0;
-
-  assert(Fields.size() + RD->getNumBases() == Inits.size());
-  for (const CXXBaseSpecifier &Base : RD->bases()) {
-    assert(InitIdx < Inits.size());
-    Expr *Init = Inits[InitIdx++];
-    BaseInits.emplace_back(&Base, Init);
-  }
-
-  assert(Fields.size() == Inits.size() - InitIdx);
-  for (const FieldDecl *Field : Fields) {
-    assert(InitIdx < Inits.size());
-    Expr *Init = Inits[InitIdx++];
-    FieldInits.emplace_back(Field, Init);
-  }
-}
-
 RecordValue &refreshRecordValue(RecordStorageLocation &Loc, Environment &Env) {
   auto &NewVal = Env.create<RecordValue>(Loc);
   Env.setValue(Loc, NewVal);

diff --git a/clang/lib/Analysis/FlowSensitive/Transfer.cpp b/clang/lib/Analysis/FlowSensitive/Transfer.cpp
@@ -20,7 +20,9 @@
 #include "clang/AST/OperationKinds.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/StmtVisitor.h"
+#include "clang/Analysis/FlowSensitive/ASTOps.h"
 #include "clang/Analysis/FlowSensitive/AdornedCFG.h"
+#include "clang/Analysis/FlowSensitive/DataflowAnalysisContext.h"
 #include "clang/Analysis/FlowSensitive/DataflowEnvironment.h"
 #include "clang/Analysis/FlowSensitive/NoopAnalysis.h"
 #include "clang/Analysis/FlowSensitive/RecordOps.h"

diff --git a/clang/lib/Basic/Targets/SPIR.h b/clang/lib/Basic/Targets/SPIR.h
@@ -315,7 +315,7 @@ class LLVM_LIBRARY_VISIBILITY SPIRVTargetInfo : public BaseSPIRVTargetInfo {
     // SPIR-V IDs are represented with a single 32-bit word.
     SizeType = TargetInfo::UnsignedInt;
     resetDataLayout("e-i64:64-v16:16-v24:32-v32:32-v48:64-"
-                    "v96:128-v192:256-v256:256-v512:512-v1024:1024");
+                    "v96:128-v192:256-v256:256-v512:512-v1024:1024-G1");
   }
 
   void getTargetDefines(const LangOptions &Opts,

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
@@ -12671,7 +12671,7 @@ void Sema::CheckMSVCRTEntryPoint(FunctionDecl *FD) {
   }
 }
 
-bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
+bool Sema::CheckForConstantInitializer(Expr *Init, unsigned DiagID) {
   // FIXME: Need strict checking.  In C89, we need to check for
   // any assignment, increment, decrement, function-calls, or
   // commas outside of a sizeof.  In C99, it's the same list,
@@ -12689,8 +12689,7 @@ bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
   const Expr *Culprit;
   if (Init->isConstantInitializer(Context, false, &Culprit))
     return false;
-  Diag(Culprit->getExprLoc(), diag::err_init_element_not_constant)
-    << Culprit->getSourceRange();
+  Diag(Culprit->getExprLoc(), DiagID) << Culprit->getSourceRange();
   return true;
 }
 
@@ -13808,29 +13807,24 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
     // OpenCL v1.2 s6.5.3: __constant locals must be constant-initialized.
     // This is true even in C++ for OpenCL.
     } else if (VDecl->getType().getAddressSpace() == LangAS::opencl_constant) {
-      CheckForConstantInitializer(Init, DclT);
+      CheckForConstantInitializer(Init);
 
-    // Otherwise, C++ does not restrict the initializer.
+      // Otherwise, C++ does not restrict the initializer.
     } else if (getLangOpts().CPlusPlus) {
       // do nothing
 
     // C99 6.7.8p4: All the expressions in an initializer for an object that has
     // static storage duration shall be constant expressions or string literals.
     } else if (VDecl->getStorageClass() == SC_Static) {
-      CheckForConstantInitializer(Init, DclT);
+      CheckForConstantInitializer(Init);
 
-    // C89 is stricter than C99 for aggregate initializers.
-    // C89 6.5.7p3: All the expressions [...] in an initializer list
-    // for an object that has aggregate or union type shall be
-    // constant expressions.
+      // C89 is stricter than C99 for aggregate initializers.
+      // C89 6.5.7p3: All the expressions [...] in an initializer list
+      // for an object that has aggregate or union type shall be
+      // constant expressions.
     } else if (!getLangOpts().C99 && VDecl->getType()->isAggregateType() &&
                isa<InitListExpr>(Init)) {
-      const Expr *Culprit;
-      if (!Init->isConstantInitializer(Context, false, &Culprit)) {
-        Diag(Culprit->getExprLoc(),
-             diag::ext_aggregate_init_not_constant)
-          << Culprit->getSourceRange();
-      }
+      CheckForConstantInitializer(Init, diag::ext_aggregate_init_not_constant);
     }
 
     if (auto *E = dyn_cast<ExprWithCleanups>(Init))
@@ -13963,7 +13957,7 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
     // Avoid duplicate diagnostics for constexpr variables.
     if (!getLangOpts().CPlusPlus && !VDecl->isInvalidDecl() &&
         !VDecl->isConstexpr())
-      CheckForConstantInitializer(Init, DclT);
+      CheckForConstantInitializer(Init);
   }
 
   QualType InitType = Init->getType();

diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -2001,6 +2001,8 @@ static void markUsedForAliasOrIfunc(Sema &S, Decl *D, const ParsedAttr &AL,
   LookupResult LR(S, Target, Sema::LookupOrdinaryName);
   if (S.LookupName(LR, S.TUScope)) {
     for (NamedDecl *ND : LR) {
+      if (!isa<FunctionDecl>(ND) && !isa<VarDecl>(ND))
+        continue;
       if (MC->shouldMangleDeclName(ND)) {
         llvm::raw_svector_ostream Out(Name);
         Name.clear();

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
@@ -7331,7 +7331,7 @@ Sema::BuildCompoundLiteralExpr(SourceLocation LParenLoc, TypeSourceInfo *TInfo,
     if (!LiteralExpr->isTypeDependent() &&
         !LiteralExpr->isValueDependent() &&
         !literalType->isDependentType()) // C99 6.5.2.5p3
-      if (CheckForConstantInitializer(LiteralExpr, literalType))
+      if (CheckForConstantInitializer(LiteralExpr))
         return ExprError();
   } else if (literalType.getAddressSpace() != LangAS::opencl_private &&
              literalType.getAddressSpace() != LangAS::Default) {

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
@@ -6114,7 +6114,8 @@ InitializationSequence::InitializationSequence(
     Sema &S, const InitializedEntity &Entity, const InitializationKind &Kind,
     MultiExprArg Args, bool TopLevelOfInitList, bool TreatUnavailableAsInvalid)
     : FailedOverloadResult(OR_Success),
-      FailedCandidateSet(Kind.getLocation(), OverloadCandidateSet::CSK_Normal) {
+      FailedCandidateSet(new OverloadCandidateSet(
+          Kind.getLocation(), OverloadCandidateSet::CSK_Normal)) {
   InitializeFrom(S, Entity, Kind, Args, TopLevelOfInitList,
                  TreatUnavailableAsInvalid);
 }
@@ -9735,7 +9736,7 @@ bool InitializationSequence::Diagnose(Sema &S,
     switch (FailedOverloadResult) {
     case OR_Ambiguous:
 
-      FailedCandidateSet.NoteCandidates(
+      FailedCandidateSet->NoteCandidates(
           PartialDiagnosticAt(
               Kind.getLocation(),
               Failure == FK_UserConversionOverloadFailed
@@ -9749,7 +9750,8 @@ bool InitializationSequence::Diagnose(Sema &S,
       break;
 
     case OR_No_Viable_Function: {
-      auto Cands = FailedCandidateSet.CompleteCandidates(S, OCD_AllCandidates, Args);
+      auto Cands =
+          FailedCandidateSet->CompleteCandidates(S, OCD_AllCandidates, Args);
       if (!S.RequireCompleteType(Kind.getLocation(),
                                  DestType.getNonReferenceType(),
                           diag::err_typecheck_nonviable_condition_incomplete,
@@ -9759,13 +9761,13 @@ bool InitializationSequence::Diagnose(Sema &S,
           << OnlyArg->getType() << Args[0]->getSourceRange()
           << DestType.getNonReferenceType();
 
-      FailedCandidateSet.NoteCandidates(S, Args, Cands);
+      FailedCandidateSet->NoteCandidates(S, Args, Cands);
       break;
     }
     case OR_Deleted: {
       OverloadCandidateSet::iterator Best;
-      OverloadingResult Ovl
-        = FailedCandidateSet.BestViableFunction(S, Kind.getLocation(), Best);
+      OverloadingResult Ovl =
+          FailedCandidateSet->BestViableFunction(S, Kind.getLocation(), Best);
 
       StringLiteral *Msg = Best->Function->getDeletedMessage();
       S.Diag(Kind.getLocation(), diag::err_typecheck_deleted_function)
@@ -9949,7 +9951,7 @@ bool InitializationSequence::Diagnose(Sema &S,
     // bad.
     switch (FailedOverloadResult) {
       case OR_Ambiguous:
-        FailedCandidateSet.NoteCandidates(
+        FailedCandidateSet->NoteCandidates(
             PartialDiagnosticAt(Kind.getLocation(),
                                 S.PDiag(diag::err_ovl_ambiguous_init)
                                     << DestType << ArgsRange),
@@ -10003,7 +10005,7 @@ bool InitializationSequence::Diagnose(Sema &S,
           break;
         }
 
-        FailedCandidateSet.NoteCandidates(
+        FailedCandidateSet->NoteCandidates(
             PartialDiagnosticAt(
                 Kind.getLocation(),
                 S.PDiag(diag::err_ovl_no_viable_function_in_init)
@@ -10013,8 +10015,8 @@ bool InitializationSequence::Diagnose(Sema &S,
 
       case OR_Deleted: {
         OverloadCandidateSet::iterator Best;
-        OverloadingResult Ovl
-          = FailedCandidateSet.BestViableFunction(S, Kind.getLocation(), Best);
+        OverloadingResult Ovl =
+            FailedCandidateSet->BestViableFunction(S, Kind.getLocation(), Best);
         if (Ovl != OR_Deleted) {
           S.Diag(Kind.getLocation(), diag::err_ovl_deleted_init)
               << DestType << ArgsRange;
@@ -10093,8 +10095,8 @@ bool InitializationSequence::Diagnose(Sema &S,
     S.Diag(Kind.getLocation(), diag::err_selected_explicit_constructor)
       << Args[0]->getSourceRange();
     OverloadCandidateSet::iterator Best;
-    OverloadingResult Ovl
-      = FailedCandidateSet.BestViableFunction(S, Kind.getLocation(), Best);
+    OverloadingResult Ovl =
+        FailedCandidateSet->BestViableFunction(S, Kind.getLocation(), Best);
     (void)Ovl;
     assert(Ovl == OR_Success && "Inconsistent overload resolution");
     CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
@@ -1057,17 +1057,14 @@ bool OverloadCandidateSet::OperatorRewriteInfo::shouldAddReversed(
 
 void OverloadCandidateSet::destroyCandidates() {
   for (iterator i = begin(), e = end(); i != e; ++i) {
-    for (auto &C : i->Conversions)
-      C.~ImplicitConversionSequence();
+    delete[] i->Conversions.data();
     if (!i->Viable && i->FailureKind == ovl_fail_bad_deduction)
       i->DeductionFailure.Destroy();
   }
 }
 
 void OverloadCandidateSet::clear(CandidateSetKind CSK) {
   destroyCandidates();
-  SlabAllocator.Reset();
-  NumInlineBytesUsed = 0;
   Candidates.clear();
   Functions.clear();
   Kind = CSK;
@@ -6983,7 +6980,7 @@ void Sema::AddOverloadCandidate(
   Candidate.RewriteKind =
       CandidateSet.getRewriteInfo().getRewriteKind(Function, PO);
   Candidate.IsSurrogate = false;
-  Candidate.IsADLCandidate = IsADLCandidate;
+  Candidate.IsADLCandidate = static_cast<unsigned>(IsADLCandidate);
   Candidate.IgnoreObjectArgument = false;
   Candidate.ExplicitCallArguments = Args.size();
 
@@ -7815,7 +7812,7 @@ void Sema::AddTemplateOverloadCandidate(
     Candidate.RewriteKind =
       CandidateSet.getRewriteInfo().getRewriteKind(Candidate.Function, PO);
     Candidate.IsSurrogate = false;
-    Candidate.IsADLCandidate = IsADLCandidate;
+    Candidate.IsADLCandidate = static_cast<unsigned>(IsADLCandidate);
     // Ignore the object argument if there is one, since we don't have an object
     // type.
     Candidate.IgnoreObjectArgument =
@@ -14125,7 +14122,8 @@ static ExprResult FinishOverloadedCallExpr(Sema &SemaRef, Scope *S, Expr *Fn,
       return ExprError();
     return SemaRef.BuildResolvedCallExpr(
         Res.get(), FDecl, LParenLoc, Args, RParenLoc, ExecConfig,
-        /*IsExecConfig=*/false, (*Best)->IsADLCandidate);
+        /*IsExecConfig=*/false,
+        static_cast<CallExpr::ADLCallKind>((*Best)->IsADLCandidate));
   }
 
   case OR_No_Viable_Function: {
@@ -14184,7 +14182,8 @@ static ExprResult FinishOverloadedCallExpr(Sema &SemaRef, Scope *S, Expr *Fn,
       return ExprError();
     return SemaRef.BuildResolvedCallExpr(
         Res.get(), FDecl, LParenLoc, Args, RParenLoc, ExecConfig,
-        /*IsExecConfig=*/false, (*Best)->IsADLCandidate);
+        /*IsExecConfig=*/false,
+        static_cast<CallExpr::ADLCallKind>((*Best)->IsADLCandidate));
   }
   }
 
@@ -14491,7 +14490,8 @@ Sema::CreateOverloadedUnaryOp(SourceLocation OpLoc, UnaryOperatorKind Opc,
       Args[0] = Input;
       CallExpr *TheCall = CXXOperatorCallExpr::Create(
           Context, Op, FnExpr.get(), ArgsArray, ResultTy, VK, OpLoc,
-          CurFPFeatureOverrides(), Best->IsADLCandidate);
+          CurFPFeatureOverrides(),
+          static_cast<CallExpr::ADLCallKind>(Best->IsADLCandidate));
 
       if (CheckCallReturnType(FnDecl->getReturnType(), OpLoc, TheCall, FnDecl))
         return ExprError();
@@ -14909,7 +14909,8 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
         // members; CodeGen should take care not to emit the this pointer.
         TheCall = CXXOperatorCallExpr::Create(
             Context, ChosenOp, FnExpr.get(), Args, ResultTy, VK, OpLoc,
-            CurFPFeatureOverrides(), Best->IsADLCandidate);
+            CurFPFeatureOverrides(),
+            static_cast<CallExpr::ADLCallKind>(Best->IsADLCandidate));
 
         if (const auto *Method = dyn_cast<CXXMethodDecl>(FnDecl);
             Method && Method->isImplicitObjectMemberFunction()) {

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
@@ -31,7 +31,6 @@
 #include "clang/AST/ExternalASTSource.h"
 #include "clang/AST/NestedNameSpecifier.h"
 #include "clang/AST/ODRDiagsEmitter.h"
-#include "clang/AST/ODRHash.h"
 #include "clang/AST/OpenACCClause.h"
 #include "clang/AST/OpenMPClause.h"
 #include "clang/AST/RawCommentList.h"

diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -16,7 +16,6 @@
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/DeclVisitor.h"
 #include "clang/AST/Expr.h"
-#include "clang/AST/ODRHash.h"
 #include "clang/AST/OpenMPClause.h"
 #include "clang/AST/PrettyDeclStackTrace.h"
 #include "clang/Basic/SourceManager.h"

diff --git a/clang/lib/Serialization/ASTWriterStmt.cpp b/clang/lib/Serialization/ASTWriterStmt.cpp
@@ -19,7 +19,6 @@
 #include "clang/AST/ExprOpenMP.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/Lex/Token.h"
-#include "clang/Sema/DeclSpec.h"
 #include "clang/Serialization/ASTRecordWriter.h"
 #include "llvm/Bitstream/BitstreamWriter.h"
 using namespace clang;

diff --git a/clang/lib/Serialization/GeneratePCH.cpp b/clang/lib/Serialization/GeneratePCH.cpp
@@ -17,7 +17,6 @@
 #include "clang/Lex/HeaderSearchOptions.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Sema/SemaConsumer.h"
-#include "clang/Serialization/ASTReader.h"
 #include "clang/Serialization/ASTWriter.h"
 #include "llvm/Bitstream/BitstreamWriter.h"
 

diff --git a/clang/lib/Serialization/GlobalModuleIndex.cpp b/clang/lib/Serialization/GlobalModuleIndex.cpp
@@ -13,7 +13,6 @@
 #include "clang/Serialization/GlobalModuleIndex.h"
 #include "ASTReaderInternals.h"
 #include "clang/Basic/FileManager.h"
-#include "clang/Lex/HeaderSearch.h"
 #include "clang/Serialization/ASTBitCodes.h"
 #include "clang/Serialization/ModuleFile.h"
 #include "clang/Serialization/PCHContainerOperations.h"

diff --git a/clang/lib/Serialization/ModuleFileExtension.cpp b/clang/lib/Serialization/ModuleFileExtension.cpp
@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 #include "clang/Serialization/ModuleFileExtension.h"
-#include "llvm/ADT/Hashing.h"
+
 using namespace clang;
 
 char ModuleFileExtension::ID = 0;

diff --git a/clang/lib/Serialization/PCHContainerOperations.cpp b/clang/lib/Serialization/PCHContainerOperations.cpp
@@ -12,8 +12,6 @@
 
 #include "clang/Serialization/PCHContainerOperations.h"
 #include "clang/AST/ASTConsumer.h"
-#include "clang/Lex/ModuleLoader.h"
-#include "llvm/Bitstream/BitstreamReader.h"
 #include "llvm/Support/raw_ostream.h"
 #include <utility>
 

diff --git a/clang/test/AST/Interp/vectors.cpp b/clang/test/AST/Interp/vectors.cpp
@@ -1,10 +1,23 @@
 // RUN: %clang_cc1 -fexperimental-new-constant-interpreter -verify=expected,both %s
 // RUN: %clang_cc1 -verify=ref,both %s
 
-// ref-no-diagnostics
-
 typedef int __attribute__((vector_size(16))) VI4;
 constexpr VI4 A = {1,2,3,4};
+static_assert(A[0] == 1, ""); // ref-error {{not an integral constant expression}}
+static_assert(A[1] == 2, ""); // ref-error {{not an integral constant expression}}
+static_assert(A[2] == 3, ""); // ref-error {{not an integral constant expression}}
+static_assert(A[3] == 4, ""); // ref-error {{not an integral constant expression}}
+
+/// VectorSplat casts
+typedef __attribute__(( ext_vector_type(4) )) float float4;
+constexpr float4 vec4_0 = (float4)0.5f;
+static_assert(vec4_0[0] == 0.5, ""); // ref-error {{not an integral constant expression}}
+static_assert(vec4_0[1] == 0.5, ""); // ref-error {{not an integral constant expression}}
+static_assert(vec4_0[2] == 0.5, ""); // ref-error {{not an integral constant expression}}
+static_assert(vec4_0[3] == 0.5, ""); // ref-error {{not an integral constant expression}}
+constexpr int vec4_0_discarded = ((float4)12.0f, 0);
+
+
 
 /// From constant-expression-cxx11.cpp
 namespace Vector {

diff --git a/clang/test/CXX/drs/dr0xx.cpp b/clang/test/CXX/drs/dr0xx.cpp
@@ -5,6 +5,11 @@
 // RUN: %clang_cc1 -std=c++20 %s -verify=expected,since-cxx11,since-cxx17 -fexceptions -fcxx-exceptions -pedantic-errors -triple %itanium_abi_triple
 // RUN: %clang_cc1 -std=c++23 %s -verify=expected,since-cxx11,since-cxx17 -fexceptions -fcxx-exceptions -pedantic-errors -triple %itanium_abi_triple
 
+#if __cplusplus == 199711L
+#define static_assert(...) __extension__ _Static_assert(__VA_ARGS__)
+// cxx98-error@-1 {{variadic macros are a C99 feature}}
+#endif
+
 namespace cwg1 { // cwg1: no
   namespace X { extern "C" void cwg1_f(int a = 1); }
   namespace Y { extern "C" void cwg1_f(int a = 1); }
@@ -897,7 +902,7 @@ namespace cwg54 { // cwg54: 2.8
 
 namespace cwg55 { // cwg55: yes
   enum E { e = 5 };
-  int test[(e + 1 == 6) ? 1 : -1];
+  static_assert(e + 1 == 6, "");
 }
 
 namespace cwg56 { // cwg56: yes
@@ -1163,10 +1168,9 @@ namespace cwg75 { // cwg75: yes
 
 namespace cwg76 { // cwg76: yes
   const volatile int n = 1;
-  int arr[n]; // #cwg76-vla
-  // expected-error@#cwg76-vla {{variable length arrays in C++ are a Clang extension}}
-  //   expected-note@#cwg76-vla {{read of volatile-qualified type 'const volatile int' is not allowed in a constant expression}}
-  // expected-error@#cwg76-vla {{variable length array declaration not allowed at file scope}}
+  static_assert(n, "");
+  // expected-error@-1 {{static assertion expression is not an integral constant expression}}
+  //   expected-note@-2 {{read of volatile-qualified type 'const volatile int' is not allowed in a constant expression}}
 }
 
 namespace cwg77 { // cwg77: yes

diff --git a/clang/test/CXX/drs/dr16xx.cpp b/clang/test/CXX/drs/dr16xx.cpp
@@ -153,10 +153,9 @@ namespace cwg1645 { // cwg1645: 3.9
 
 namespace cwg1652 { // cwg1652: 3.6
   int a, b;
-  int arr[&a + 1 == &b ? 1 : 2];
-  // expected-error@-1 {{variable length arrays in C++ are a Clang extension}}
+  static_assert(&a + 1 == &b, "");
+  // expected-error@-1 {{static assertion expression is not an integral constant expression}}
   //   expected-note@-2 {{comparison against pointer '&a + 1' that points past the end of a complete object has unspecified value}}
-  // expected-error@-3 {{variable length array declaration not allowed at file scope}}
 }
 
 namespace cwg1653 { // cwg1653: 4 c++17

diff --git a/clang/test/CXX/drs/dr1xx.cpp b/clang/test/CXX/drs/dr1xx.cpp
@@ -5,6 +5,17 @@
 // RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11,since-cxx17 -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: %clang_cc1 -std=c++23 -triple x86_64-unknown-unknown %s -verify=expected,since-cxx11,since-cxx17 -fexceptions -fcxx-exceptions -pedantic-errors
 
+#if __cplusplus == 199711L
+#define static_assert(...) __extension__ _Static_assert(__VA_ARGS__)
+// cxx98-error@-1 {{variadic macros are a C99 feature}}
+#endif
+
+#if __cplusplus == 199711L
+#define __enable_constant_folding(x) (__builtin_constant_p(x) ? (x) : (x))
+#else
+#define __enable_constant_folding
+#endif
+
 namespace cwg100 { // cwg100: yes
   template<const char (*)[4]> struct A {}; // #cwg100-A
   template<const char (&)[4]> struct B {}; // #cwg100-B
@@ -736,22 +747,16 @@ namespace cwg147 { // cwg147: yes
 
 namespace cwg148 { // cwg148: yes
   struct A { int A::*p; };
-  int check1[__is_pod(int(A::*)) ? 1 : -1];
-  int check2[__is_pod(A) ? 1 : -1];
+  static_assert(__is_pod(int(A::*)), "");
+  static_assert(__is_pod(A), "");
 }
 
 // cwg149: na
 
 namespace cwg151 { // cwg151: 3.1
   struct X {};
   typedef int X::*p;
-#if __cplusplus < 201103L
-#define fold(x) (__builtin_constant_p(0) ? (x) : (x))
-#else
-#define fold
-#endif
-  int check[fold(p() == 0) ? 1 : -1];
-#undef fold
+  static_assert(__enable_constant_folding(p() == 0), "");
 }
 
 namespace cwg152 { // cwg152: yes
@@ -956,42 +961,42 @@ namespace cwg171 {
 
 namespace cwg172 { // cwg172: yes
   enum { zero };
-  int check1[-1 < zero ? 1 : -1];
+  static_assert(-1 < zero, "");
 
   enum { x = -1, y = (unsigned int)-1 };
-  int check2[sizeof(x) > sizeof(int) ? 1 : -1];
+  static_assert(sizeof(x) > sizeof(int), "");
 
   enum { a = (unsigned int)-1 / 2 };
-  int check3a[sizeof(a) == sizeof(int) ? 1 : -1];
-  int check3b[-a < 0 ? 1 : -1];
+  static_assert(sizeof(a) == sizeof(int), "");
+  static_assert(-a < 0, "");
 
   enum { b = (unsigned int)-1 / 2 + 1 };
-  int check4a[sizeof(b) == sizeof(unsigned int) ? 1 : -1];
-  int check4b[-b > 0 ? 1 : -1];
+  static_assert(sizeof(b) == sizeof(unsigned int), "");
+  static_assert(-b > 0, "");
 
   enum { c = (unsigned long)-1 / 2 };
-  int check5a[sizeof(c) == sizeof(long) ? 1 : -1];
-  int check5b[-c < 0 ? 1 : -1];
+  static_assert(sizeof(c) == sizeof(long), "");
+  static_assert(-c < 0, "");
 
   enum { d = (unsigned long)-1 / 2 + 1 };
-  int check6a[sizeof(d) == sizeof(unsigned long) ? 1 : -1];
-  int check6b[-d > 0 ? 1 : -1];
+  static_assert(sizeof(d) == sizeof(unsigned long), "");
+  static_assert(-d > 0, "");
 
   enum { e = (unsigned long long)-1 / 2 };
   // cxx98-error@-1 {{'long long' is a C++11 extension}}
-  int check7a[sizeof(e) == sizeof(long) ? 1 : -1];
-  int check7b[-e < 0 ? 1 : -1];
+  static_assert(sizeof(e) == sizeof(long), "");
+  static_assert(-e < 0, "");
 
   enum { f = (unsigned long long)-1 / 2 + 1 };
   // cxx98-error@-1 {{'long long' is a C++11 extension}}
-  int check8a[sizeof(f) == sizeof(unsigned long) ? 1 : -1];
-  int check8b[-f > 0 ? 1 : -1];
+  static_assert(sizeof(f) == sizeof(unsigned long), "");
+  static_assert(-f > 0, "");
 }
 
 namespace cwg173 { // cwg173: yes
-  int check[('0' + 1 == '1' && '0' + 2 == '2' && '0' + 3 == '3' &&
-             '0' + 4 == '4' && '0' + 5 == '5' && '0' + 6 == '6' &&
-             '0' + 7 == '7' && '0' + 8 == '8' && '0' + 9 == '9') ? 1 : -1];
+  static_assert('0' + 1 == '1' && '0' + 2 == '2' && '0' + 3 == '3' &&
+                '0' + 4 == '4' && '0' + 5 == '5' && '0' + 6 == '6' &&
+                '0' + 7 == '7' && '0' + 8 == '8' && '0' + 9 == '9', "");
 }
 
 // cwg174: sup 1012
@@ -1070,7 +1075,7 @@ namespace cwg177 { // cwg177: yes
 }
 
 namespace cwg178 { // cwg178: yes
-  int check[int() == 0 ? 1 : -1];
+  static_assert(int() == 0, "");
 #if __cplusplus >= 201103L
   static_assert(int{} == 0, "");
   struct S { int a, b; };
@@ -1180,7 +1185,7 @@ namespace cwg187 { // cwg187: sup 481
 
 namespace cwg188 { // cwg188: yes
   char c[10];
-  int check[sizeof(0, c) == 10 ? 1 : -1];
+  static_assert(sizeof(0, c) == 10, "");
 }
 
 // cwg190 FIXME: add codegen test for tbaa

diff --git a/clang/test/CXX/drs/dr2xx.cpp b/clang/test/CXX/drs/dr2xx.cpp
@@ -10,10 +10,15 @@
 typedef __SIZE_TYPE__ size_t;
 // cxx98-error@-1 0-1 {{'long long' is a C++11 extension}}
 
-#if __cplusplus < 201103L
-#define fold(x) (__builtin_constant_p(x) ? (x) : (x))
+#if __cplusplus == 199711L
+#define static_assert(...) __extension__ _Static_assert(__VA_ARGS__)
+// cxx98-error@-1 {{variadic macros are a C99 feature}}
+#endif
+
+#if __cplusplus == 199711L
+#define __enable_constant_folding(x) (__builtin_constant_p(x) ? (x) : (x))
 #else
-#define fold
+#define __enable_constant_folding
 #endif
 
 namespace cwg200 { // cwg200: dup 214
@@ -31,7 +36,7 @@ namespace cwg200 { // cwg200: dup 214
 namespace cwg202 { // cwg202: 3.1
   template<typename T> T f();
   template<int (*g)()> struct X {
-    int arr[fold(g == &f<int>) ? 1 : -1];
+    static_assert(__enable_constant_folding(g == &f<int>), "");
   };
   template struct X<f>;
 }
@@ -1024,7 +1029,7 @@ namespace cwg275 { // cwg275: no
 namespace cwg277 { // cwg277: 3.1
   typedef int *intp;
   int *p = intp();
-  int a[fold(intp() ? -1 : 1)];
+  static_assert(__enable_constant_folding(!intp()), "");
 }
 
 namespace cwg280 { // cwg280: 2.9

diff --git a/clang/test/CXX/drs/dr3xx.cpp b/clang/test/CXX/drs/dr3xx.cpp
@@ -5,6 +5,17 @@
 // RUN: %clang_cc1 -std=c++11 -verify=expected,cxx98-14,cxx98-17,cxx98-20,cxx11-14,since-cxx11 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: %clang_cc1 -std=c++98 -verify=expected,cxx98-14,cxx98-17,cxx98-20,cxx98 -triple %itanium_abi_triple %s -fexceptions -fcxx-exceptions -pedantic-errors
 
+#if __cplusplus == 199711L
+#define static_assert(...) __extension__ _Static_assert(__VA_ARGS__)
+// cxx98-error@-1 {{variadic macros are a C99 feature}}
+#endif
+
+#if __cplusplus == 199711L
+#define __enable_constant_folding(x) (__builtin_constant_p(x) ? (x) : (x))
+#else
+#define __enable_constant_folding
+#endif
+
 namespace cwg300 { // cwg300: yes
   template<typename R, typename A> void f(R (&)(A)) {}
   int g(int);
@@ -396,7 +407,7 @@ namespace cwg324 { // cwg324: 3.6
 
 namespace cwg326 { // cwg326: 3.1
   struct S {};
-  int test[__is_trivially_constructible(S, const S&) ? 1 : -1];
+  static_assert(__is_trivially_constructible(S, const S&), "");
 }
 
 namespace cwg327 { // cwg327: dup 538
@@ -653,7 +664,7 @@ namespace cwg339 { // cwg339: 2.8
 
   template<typename T> A<sizeof(f(T()))> make_A();
 
-  int a[conv_int<char>::value ? 1 : -1];
+  static_assert(conv_int<char>::value, "");
   bool b = conv_int2<char>(A<1>());
   A<1> c = make_A<char>();
 }
@@ -1099,21 +1110,14 @@ namespace cwg364 { // cwg364: yes
 #endif
 
 namespace cwg367 { // cwg367: yes
-  // FIXME: These diagnostics are terrible. Don't diagnose an ill-formed global
-  // array as being a VLA!
-  int a[true ? throw 0 : 4];
-  // expected-error@-1 {{variable length arrays in C++ are a Clang extension}}
-  // expected-error@-2 {{variable length array declaration not allowed at file scope}}
-  int b[true ? 4 : throw 0];
-  // cxx98-error@-1 {{variable length arrays in C++ are a Clang extension}}
-  // cxx98-error@-2 {{variable length array folded to constant array as an extension}}
-  int c[true ? *new int : 4];
-  // expected-error@-1 {{variable length arrays in C++ are a Clang extension}}
+  static_assert(__enable_constant_folding(true ? throw 0 : 4), "");
+  // expected-error@-1 {{expression is not an integral constant expression}}
+  static_assert(__enable_constant_folding(true ? 4 : throw 0), "");
+  static_assert(__enable_constant_folding(true ? *new int : 4), "");
+  // expected-error@-1 {{expression is not an integral constant expression}}
   //   expected-note@-2 {{read of uninitialized object is not allowed in a constant expression}}
-  // expected-error@-3 {{variable length array declaration not allowed at file scope}}
-  int d[true ? 4 : *new int];
-  // cxx98-error@-1 {{variable length arrays in C++ are a Clang extension}}
-  // cxx98-error@-2 {{variable length array folded to constant array as an extension}}
+  static_assert(__enable_constant_folding(true ? 4 : *new int), "");
+
 }
 
 namespace cwg368 { // cwg368: 3.6
@@ -1325,7 +1329,7 @@ namespace cwg383 { // cwg383: yes
   struct B { ~B(); };
   union C { C &operator=(const C&); };
   union D { ~D(); };
-  int check[(__is_pod(A) || __is_pod(B) || __is_pod(C) || __is_pod(D)) ? -1 : 1];
+  static_assert(!__is_pod(A) && !__is_pod(B) && !__is_pod(C) && !__is_pod(D), "");
 }
 
 namespace cwg384 { // cwg384: yes

diff --git a/clang/test/CXX/drs/dr4xx.cpp b/clang/test/CXX/drs/dr4xx.cpp
@@ -6,6 +6,11 @@
 // RUN: env ASAN_OPTIONS=detect_stack_use_after_return=0 %clang_cc1 -std=c++23 %s -verify=expected,since-cxx20,since-cxx17,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: env ASAN_OPTIONS=detect_stack_use_after_return=0 %clang_cc1 -std=c++2c %s -verify=expected,since-cxx20,since-cxx17,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
 
+#if __cplusplus == 199711L
+#define static_assert(...) __extension__ _Static_assert(__VA_ARGS__)
+// cxx98-error@-1 {{variadic macros are a C99 feature}}
+#endif
+
 // FIXME: __SIZE_TYPE__ expands to 'long long' on some targets.
 __extension__ typedef __SIZE_TYPE__ size_t;
 
@@ -217,7 +222,7 @@ namespace cwg407 { // cwg407: 3.8
 }
 
 namespace cwg408 { // cwg408: 3.4
-  template<int N> void g() { int arr[N != 1 ? 1 : -1]; }
+  template<int N> void g() { static_assert(N != 1, ""); }
   template<> void g<2>() { }
 
   template<typename T> struct S {
@@ -239,7 +244,7 @@ namespace cwg408 { // cwg408: 3.4
   };
   template<typename T> int R<T>::arr[1];
   template<typename T> void R<T>::f() {
-    int arr[sizeof(arr) != sizeof(int) ? 1 : -1];
+    static_assert(sizeof(arr) != sizeof(int), "");
   }
   template<> int R<int>::arr[2];
   template void R<int>::f();
@@ -842,11 +847,10 @@ namespace cwg451 { // cwg451: yes
   // expected-warning@-1 {{division by zero is undefined}}
   const int b = 1 / 0; // #cwg451-b
   // expected-warning@-1 {{division by zero is undefined}}
-  int arr[b]; // #cwg451-arr
-  // expected-error@-1 {{variable length arrays in C++ are a Clang extension}}
+  static_assert(b, "");
+  // expected-error@-1 {{expression is not an integral constant expression}}
   //   expected-note@-2 {{initializer of 'b' is not a constant expression}}
   //   expected-note@#cwg451-b {{declared here}}
-  // expected-error@#cwg451-arr {{variable length array declaration not allowed at file scope}}
 }
 
 namespace cwg452 { // cwg452: yes
@@ -876,11 +880,10 @@ namespace cwg456 { // cwg456: yes
 namespace cwg457 { // cwg457: yes
   const int a = 1;
   const volatile int b = 1;
-  int ax[a];
-  int bx[b];
-  // expected-error@-1 {{variable length arrays in C++ are a Clang extension}}
+  static_assert(a, "");
+  static_assert(b, "");
+  // expected-error@-1 {{expression is not an integral constant expression}}
   //   expected-note@-2 {{read of volatile-qualified type 'const volatile int' is not allowed in a constant expression}}
-  // expected-error@-3 {{variable length array declaration not allowed at file scope}}
 
   enum E {
     ea = a,
@@ -1276,20 +1279,18 @@ namespace cwg482 { // cwg482: 3.5
 
 namespace cwg483 { // cwg483: yes
   namespace climits {
-    int check1[__SCHAR_MAX__ >= 127 ? 1 : -1];
-    int check2[__SHRT_MAX__ >= 32767 ? 1 : -1];
-    int check3[__INT_MAX__ >= 32767 ? 1 : -1];
-    int check4[__LONG_MAX__ >= 2147483647 ? 1 : -1];
-    int check5[__LONG_LONG_MAX__ >= 9223372036854775807 ? 1 : -1];
-    // cxx98-error@-1 {{'long long' is a C++11 extension}}
-    // cxx98-error@-2 0-1{{'long long' is a C++11 extension}}
+    static_assert(__SCHAR_MAX__ >= 127, "");
+    static_assert(__SHRT_MAX__ >= 32767, "");
+    static_assert(__INT_MAX__ >= 32767, "");
+    static_assert(__LONG_MAX__ >= 2147483647, "");
+    static_assert(__LONG_LONG_MAX__ >= 9223372036854775807, "");
   }
   namespace cstdint {
-    int check1[__PTRDIFF_WIDTH__ >= 16 ? 1 : -1];
-    int check2[__SIG_ATOMIC_WIDTH__ >= 8 ? 1 : -1];
-    int check3[__SIZE_WIDTH__ >= 16 ? 1 : -1];
-    int check4[__WCHAR_WIDTH__ >= 8 ? 1 : -1];
-    int check5[__WINT_WIDTH__ >= 16 ? 1 : -1];
+    static_assert(__PTRDIFF_WIDTH__ >= 16, "");
+    static_assert(__SIG_ATOMIC_WIDTH__ >= 8, "");
+    static_assert(__SIZE_WIDTH__ >= 16, "");
+    static_assert(__WCHAR_WIDTH__ >= 8, "");
+    static_assert(__WINT_WIDTH__ >= 16, "");
   }
 }
 
@@ -1366,11 +1367,10 @@ namespace cwg486 { // cwg486: yes
 namespace cwg487 { // cwg487: yes
   enum E { e };
   int operator+(int, E); // #cwg487-operator-plus
-  int i[4 + e]; // #cwg487-i
-  // expected-error@-1 {{variable length arrays in C++ are a Clang extension}}
+  static_assert(4 + e, "");
+  // expected-error@-1 {{expression is not an integral constant expression}}
   //   since-cxx11-note@-2 {{non-constexpr function 'operator+' cannot be used in a constant expression}}
   //   since-cxx11-note@#cwg487-operator-plus {{declared here}}
-  // expected-error@#cwg487-i {{variable length array declaration not allowed at file scope}}
 }
 
 namespace cwg488 { // cwg488: yes c++11
@@ -1485,13 +1485,13 @@ namespace cwg495 { // cwg495: 3.5
 namespace cwg496 { // cwg496: sup 2094
   struct A { int n; };
   struct B { volatile int n; };
-  int check1[ __is_trivially_copyable(const int) ? 1 : -1];
+  static_assert(__is_trivially_copyable(const int), "");
   // This checks the cwg2094 behavior, not cwg496
-  int check2[ __is_trivially_copyable(volatile int) ? 1 : -1];
-  int check3[ __is_trivially_constructible(A, const A&) ? 1 : -1];
-  int check4[ __is_trivially_constructible(B, const B&) ? 1 : -1];
-  int check5[ __is_trivially_assignable(A, const A&) ? 1 : -1];
-  int check6[ __is_trivially_assignable(B, const B&) ? 1 : -1];
+  static_assert(__is_trivially_copyable(volatile int), "");
+  static_assert(__is_trivially_constructible(A, const A&), "");
+  static_assert(__is_trivially_constructible(B, const B&), "");
+  static_assert(__is_trivially_assignable(A, const A&), "");
+  static_assert(__is_trivially_assignable(B, const B&), "");
 }
 
 namespace cwg497 { // cwg497: sup 253

diff --git a/clang/test/CXX/drs/dr5xx.cpp b/clang/test/CXX/drs/dr5xx.cpp
@@ -5,6 +5,11 @@
 // RUN: %clang_cc1 -std=c++20 %s -verify=expected,since-cxx20,since-cxx17,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
 // RUN: %clang_cc1 -std=c++23 %s -verify=expected,since-cxx23,since-cxx20,since-cxx17,since-cxx11 -fexceptions -fcxx-exceptions -pedantic-errors
 
+#if __cplusplus == 199711L
+#define static_assert(...) __extension__ _Static_assert(__VA_ARGS__)
+// cxx98-error@-1 {{variadic macros are a C99 feature}}
+#endif
+
 // FIXME: This is included to avoid a diagnostic with no source location
 // pointing at the implicit operator new. We can't match such a diagnostic
 // with -verify.
@@ -819,7 +824,7 @@ namespace cwg565 { // cwg565: yes
 
 namespace cwg566 { // cwg566: yes
 #if __cplusplus >= 201103L
-  int check[int(-3.99) == -3 ? 1 : -1];
+  static_assert(int(-3.99) == -3, "");
 #endif
 }
 
@@ -834,7 +839,7 @@ namespace cwg568 { // cwg568: 3.0 c++11
   public:
     int n;
   };
-  int check_trivial[__is_trivial(trivial) ? 1 : -1];
+  static_assert(__is_trivial(trivial), "");
 
   struct std_layout {
     std_layout();
@@ -843,7 +848,7 @@ namespace cwg568 { // cwg568: 3.0 c++11
   private:
     int n;
   };
-  int check_std_layout[__is_standard_layout(std_layout) ? 1 : -1];
+  static_assert(__is_standard_layout(std_layout), "");
 
   struct aggregate {
     int x;
@@ -885,7 +890,7 @@ namespace cwg570 { // cwg570: dup 633
 
 namespace cwg572 { // cwg572: yes
   enum E { a = 1, b = 2 };
-  int check[a + b == 3 ? 1 : -1];
+  static_assert(a + b == 3, "");
 }
 
 namespace cwg573 { // cwg573: no

diff --git a/clang/test/CXX/drs/dr6xx.cpp b/clang/test/CXX/drs/dr6xx.cpp
@@ -144,7 +144,7 @@ namespace cwg608 { // cwg608: yes
   struct D : B, C {};
 }
 
-int cwg610[-0u == 0u ? 1 : -1]; // cwg610: yes
+static_assert(-0u == 0u, ""); // cwg610: yes
 
 namespace cwg611 { // cwg611: yes
   int k;
@@ -190,8 +190,8 @@ namespace cwg613 { // cwg613: yes c++11
   }
 }
 
-int cwg614_a[(-1) / 2 == 0 ? 1 : -1]; // cwg614: yes
-int cwg614_b[(-1) % 2 == -1 ? 1 : -1];
+static_assert((-1) / 2 == 0, ""); // cwg614: yes
+static_assert((-1) % 2 == -1, "");
 
 namespace cwg615 { // cwg615: yes
   int f();

diff --git a/clang/test/CodeGen/alias.cpp b/clang/test/CodeGen/alias.cpp
@@ -1,27 +1,42 @@
-// RUN: %clang_cc1 -triple x86_64-linux -verify -emit-llvm-only %s
-// RUN: not %clang_cc1 -triple x86_64-linux -emit-llvm-only -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-linux -verify -emit-llvm-only -DERR %s
+// RUN: not %clang_cc1 -triple x86_64-linux -emit-llvm-only -fdiagnostics-parseable-fixits -DERR %s 2>&1 | FileCheck %s --check-prefix=FIXIT
+// RUN: %clang_cc1 -triple x86_64-linux -emit-llvm %s -o - | FileCheck %s
 
+#ifdef ERR
 void *f1_ifunc(void) { return nullptr; }
 void f1(void) __attribute__((alias("f1_ifunc")));
 // expected-error@-1 {{alias must point to a defined variable or function}}
 // expected-note@-2 {{must refer to its mangled name}}
 // expected-note@-3 {{function by that name is mangled as}}
-// CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:30-[[@LINE-4]]:47}:"alias(\"_Z8f1_ifuncv\")"
+// FIXIT: fix-it:"{{.*}}":{[[@LINE-4]]:30-[[@LINE-4]]:47}:"alias(\"_Z8f1_ifuncv\")"
 
 void *f6_resolver_resolver(void) { return 0; }
 void *f6_resolver(void) __attribute__((alias("f6_resolver_resolver")));
 // expected-error@-1 {{alias must point to a defined variable or function}}
 // expected-note@-2 {{must refer to its mangled name}}
 // expected-note@-3 {{function by that name is mangled as}}
-// CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:40-[[@LINE-4]]:69}:"alias(\"_Z20f6_resolver_resolverv\")"
+// FIXIT: fix-it:"{{.*}}":{[[@LINE-4]]:40-[[@LINE-4]]:69}:"alias(\"_Z20f6_resolver_resolverv\")"
 void f6(void) __attribute__((alias("f6_resolver")));
 // expected-error@-1 {{alias must point to a defined variable or function}}
 // expected-note@-2 {{must refer to its mangled name}}
 // expected-note@-3 {{function by that name is mangled as}}
-// CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:30-[[@LINE-4]]:50}:"alias(\"_Z11f6_resolverv\")"
+// FIXIT: fix-it:"{{.*}}":{[[@LINE-4]]:30-[[@LINE-4]]:50}:"alias(\"_Z11f6_resolverv\")"
 
 __attribute__((unused, alias("resolver"), deprecated("hahahaha, isn't C great?")))
 void func();
 // expected-error@-2 {{alias must point to a defined variable or function}}
 // expected-note@-3 {{must refer to its mangled name}}
+#endif
 
+// CHECK: @_ZN4libc4log2Ed ={{.*}} alias double (double), ptr @log2
+// CHECK: define{{.*}} @log2(
+namespace libc { double log2(double x); }
+extern "C" double log2(double);
+namespace std { using ::log2; }
+using std::log2;
+
+namespace libc {
+decltype(libc::log2) __log2_impl__ __asm__("log2");
+decltype(libc::log2) log2 [[gnu::alias("log2")]];
+double __log2_impl__(double x) { return x; }
+}
diff --git a/clang/test/Sema/recover-expr-gh88008-nocrash.c b/clang/test/Sema/recover-expr-gh88008-nocrash.c
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 %s -verify -fsyntax-only -std=c90
+
+struct S {
+  int v;
+};
+
+struct T; // expected-note {{forward declaration of 'struct T'}}
+
+void gh88008_nocrash(struct T *t) {
+  struct S s = { .v = t->y }; // expected-error {{incomplete definition of type 'struct T'}}
+}
diff --git a/...emaCXX/instantiate-new-placement-size.cpp → clang/test/SemaCXX/PR41441.cpp b/...emaCXX/instantiate-new-placement-size.cpp → clang/test/SemaCXX/PR41441.cpp
@@ -1,6 +1,9 @@
-// RUN: %clang -S -fno-discard-value-names -emit-llvm -o - %s | FileCheck %s
-// Issue no: 41441
-#include <new>
+// RUN: %clang --target=x86_64-pc-linux -S -fno-discard-value-names -emit-llvm -o - %s | FileCheck %s
+
+namespace std {
+  using size_t = decltype(sizeof(int));
+};
+void* operator new[](std::size_t, void*) noexcept;
 
 // CHECK: call void @llvm.memset.p0.i64(ptr align 1 %x, i8 0, i64 8, i1 false)
 // CHECK: call void @llvm.memset.p0.i64(ptr align 16 %x, i8 0, i64 32, i1 false)

diff --git a/flang/cmake/modules/AddFlangOffloadRuntime.cmake b/flang/cmake/modules/AddFlangOffloadRuntime.cmake
@@ -10,7 +10,7 @@ set(FLANG_EXPERIMENTAL_OMP_OFFLOAD_BUILD "off" CACHE STRING
 set(FLANG_OMP_DEVICE_ARCHITECTURES "all" CACHE STRING
   "List of OpenMP device architectures to be used to compile the Fortran runtime (e.g. 'gfx1103;sm_90')")
 
-macro(enable_cuda_compilation files)
+macro(enable_cuda_compilation name files)
   if (FLANG_EXPERIMENTAL_CUDA_RUNTIME)
     if (BUILD_SHARED_LIBS)
       message(FATAL_ERROR
@@ -52,6 +52,10 @@ macro(enable_cuda_compilation files)
       include_directories(AFTER ${FLANG_LIBCUDACXX_PATH}/include)
       add_compile_definitions(RT_USE_LIBCUDACXX=1)
     endif()
+
+    # Add an OBJECT library consisting of CUDA PTX.
+    llvm_add_library(${name}PTX OBJECT PARTIAL_SOURCES_INTENDED ${files})
+    set_property(TARGET obj.${name}PTX PROPERTY CUDA_PTX_COMPILATION ON)
   endif()
 endmacro()
 

diff --git a/flang/lib/Decimal/CMakeLists.txt b/flang/lib/Decimal/CMakeLists.txt
@@ -55,7 +55,7 @@ set(sources
 )
 
 include(AddFlangOffloadRuntime)
-enable_cuda_compilation("${sources}")
+enable_cuda_compilation(FortranDecimal "${sources}")
 enable_omp_offload_compilation("${sources}")
 
 add_flang_library(FortranDecimal INSTALL_WITH_TOOLCHAIN ${sources})

diff --git a/flang/runtime/CMakeLists.txt b/flang/runtime/CMakeLists.txt
@@ -224,7 +224,7 @@ set(supported_files
   utf.cpp
   )
 
-enable_cuda_compilation("${supported_files}")
+enable_cuda_compilation(FortranRuntime "${supported_files}")
 enable_omp_offload_compilation("${supported_files}")
 
 if (NOT TARGET FortranFloat128Math)

diff --git a/flang/test/Driver/msvc-dependent-lib-flags.f90 b/flang/test/Driver/msvc-dependent-lib-flags.f90
@@ -1,7 +1,7 @@
-! RUN: %flang -### --target=aarch64-windows-msvc %S/Inputs/hello.f90 -v 2>&1 | FileCheck %s --check-prefixes=MSVC
-! RUN: %flang -### --target=aarch64-windows-msvc -fms-runtime-lib=static_dbg %S/Inputs/hello.f90 -v 2>&1 | FileCheck %s --check-prefixes=MSVC-DEBUG
-! RUN: %flang -### --target=aarch64-windows-msvc -fms-runtime-lib=dll %S/Inputs/hello.f90 -v 2>&1 | FileCheck %s --check-prefixes=MSVC-DLL
-! RUN: %flang -### --target=aarch64-windows-msvc -fms-runtime-lib=dll_dbg %S/Inputs/hello.f90 -v 2>&1 | FileCheck %s --check-prefixes=MSVC-DLL-DEBUG
+! RUN: %flang -### --target=aarch64-windows-msvc -resource-dir=%S/Inputs/resource_dir %S/Inputs/hello.f90 -v 2>&1 | FileCheck %s --check-prefixes=MSVC
+! RUN: %flang -### --target=aarch64-windows-msvc -resource-dir=%S/Inputs/resource_dir -fms-runtime-lib=static_dbg %S/Inputs/hello.f90 -v 2>&1 | FileCheck %s --check-prefixes=MSVC-DEBUG
+! RUN: %flang -### --target=aarch64-windows-msvc -resource-dir=%S/Inputs/resource_dir -fms-runtime-lib=dll %S/Inputs/hello.f90 -v 2>&1 | FileCheck %s --check-prefixes=MSVC-DLL
+! RUN: %flang -### --target=aarch64-windows-msvc -resource-dir=%S/Inputs/resource_dir -fms-runtime-lib=dll_dbg %S/Inputs/hello.f90 -v 2>&1 | FileCheck %s --check-prefixes=MSVC-DLL-DEBUG
 
 ! MSVC: -fc1
 ! MSVC-SAME: --dependent-lib=clang_rt.builtins.lib

diff --git a/flang/test/Semantics/OpenMP/clause-validity01.f90 b/flang/test/Semantics/OpenMP/clause-validity01.f90
@@ -342,8 +342,8 @@
   a = 1.0
   !ERROR: COPYPRIVATE clause is not allowed on the END WORKSHARE directive
   !$omp end workshare nowait copyprivate(a)
+  !ERROR: NOWAIT clause is not allowed on the OMP WORKSHARE directive, use it on OMP END WORKSHARE directive 
   !$omp workshare nowait
-  !ERROR: NOWAIT clause is not allowed on the WORKSHARE directive, use it on OMP END WORKSHARE directive
   !$omp end workshare
   !$omp end parallel
 

diff --git a/libc/src/fenv/CMakeLists.txt b/libc/src/fenv/CMakeLists.txt
@@ -17,7 +17,6 @@ add_entrypoint_object(
   HDRS
     fesetround.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
     -O2
@@ -30,7 +29,6 @@ add_entrypoint_object(
   HDRS
     feclearexcept.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
     -O2
@@ -43,7 +41,6 @@ add_entrypoint_object(
   HDRS
     feraiseexcept.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
     -O2
@@ -56,7 +53,6 @@ add_entrypoint_object(
   HDRS
     fetestexcept.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
     -O2
@@ -69,7 +65,6 @@ add_entrypoint_object(
   HDRS
     fegetenv.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.hdr.types.fenv_t
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
@@ -83,7 +78,6 @@ add_entrypoint_object(
   HDRS
     fesetenv.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.hdr.types.fenv_t
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
@@ -111,7 +105,6 @@ add_entrypoint_object(
   HDRS
     fesetexcept.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
     -O2
@@ -166,7 +159,6 @@ add_entrypoint_object(
   HDRS
     feenableexcept.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
     -O2
@@ -179,7 +171,6 @@ add_entrypoint_object(
   HDRS
     fedisableexcept.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
     -O2
@@ -192,7 +183,6 @@ add_entrypoint_object(
   HDRS
     fegetexcept.h
   DEPENDS
-    libc.hdr.fenv_macros
     libc.src.__support.FPUtil.fenv_impl
   COMPILE_OPTIONS
     -O2

diff --git a/libc/src/fenv/fegetexceptflag.h b/libc/src/fenv/fegetexceptflag.h
@@ -9,7 +9,7 @@
 #ifndef LLVM_LIBC_SRC_FENV_FEGETEXCEPTFLAG_H
 #define LLVM_LIBC_SRC_FENV_FEGETEXCEPTFLAG_H
 
-#include <fenv.h>
+#include "hdr/types/fexcept_t.h"
 
 namespace LIBC_NAMESPACE {
 

diff --git a/libc/src/fenv/fesetexceptflag.h b/libc/src/fenv/fesetexceptflag.h
@@ -9,7 +9,7 @@
 #ifndef LLVM_LIBC_SRC_FENV_FESETEXCEPTFLAG_H
 #define LLVM_LIBC_SRC_FENV_FESETEXCEPTFLAG_H
 
-#include <fenv.h>
+#include "hdr/types/fexcept_t.h"
 
 namespace LIBC_NAMESPACE {
 

diff --git a/libc/src/fenv/feupdateenv.cpp b/libc/src/fenv/feupdateenv.cpp
@@ -10,7 +10,7 @@
 #include "src/__support/FPUtil/FEnvImpl.h"
 #include "src/__support/common.h"
 
-#include <fenv.h>
+#include "hdr/types/fenv_t.h"
 
 namespace LIBC_NAMESPACE {
 

diff --git a/libclc/CMakeLists.txt b/libclc/CMakeLists.txt
@@ -50,7 +50,7 @@ if( LIBCLC_STANDALONE_BUILD OR CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DI
   endif()
 
   # Import required tools as targets
-  foreach( tool clang llvm-as llvm-link opt )
+  foreach( tool IN ITEMS clang llvm-as llvm-link opt )
     find_program( LLVM_TOOL_${tool} ${tool} PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH )
     add_executable( libclc::${tool} IMPORTED GLOBAL )
     set_target_properties( libclc::${tool} PROPERTIES IMPORTED_LOCATION ${LLVM_TOOL_${tool}} )
@@ -68,7 +68,7 @@ else()
     message(FATAL_ERROR "Clang is not enabled, but is required to build libclc in-tree")
   endif()
 
-  foreach( tool clang llvm-as llvm-link opt )
+  foreach( tool IN ITEMS clang llvm-as llvm-link opt )
     add_executable(libclc::${tool} ALIAS ${tool})
   endforeach()
 endif()
@@ -181,7 +181,7 @@ install( FILES ${CMAKE_CURRENT_BINARY_DIR}/libclc.pc DESTINATION "${CMAKE_INSTAL
 install( DIRECTORY generic/include/clc DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}" )
 
 if( ENABLE_RUNTIME_SUBNORMAL )
-  foreach( file subnormal_use_default subnormal_disable )
+  foreach( file IN ITEMS subnormal_use_default subnormal_disable )
     link_bc(
        TARGET ${file}
        INPUTS ${PROJECT_SOURCE_DIR}/generic/lib/${file}.ll

diff --git a/libcxx/.clang-format b/libcxx/.clang-format
@@ -24,6 +24,7 @@ AttributeMacros: [
                   '_LIBCPP_CONSTEXPR_SINCE_CXX23',
                   '_LIBCPP_CONSTEXPR',
                   '_LIBCPP_CONSTINIT',
+                  '_LIBCPP_DEPRECATED_ATOMIC_SYNC',
                   '_LIBCPP_DEPRECATED_IN_CXX11',
                   '_LIBCPP_DEPRECATED_IN_CXX14',
                   '_LIBCPP_DEPRECATED_IN_CXX17',

diff --git a/libcxx/docs/BuildingLibcxx.rst b/libcxx/docs/BuildingLibcxx.rst
@@ -206,6 +206,12 @@ libc++ specific options
 
   Toggle the installation of the libc++ headers.
 
+.. option:: LIBCXX_INSTALL_MODULES:BOOL
+
+  **Default**: ``OFF``
+
+  Toggle the installation of the experimental libc++ module sources.
+
 .. option:: LIBCXX_ENABLE_SHARED:BOOL
 
   **Default**: ``ON``

diff --git a/libcxx/docs/ReleaseNotes/19.rst b/libcxx/docs/ReleaseNotes/19.rst
@@ -75,6 +75,10 @@ Improvements and New Features
 Deprecations and Removals
 -------------------------
 
+- The C++20 synchronization library (``<barrier>``, ``<latch>``, ``atomic::wait``, etc.) has been deprecated
+  in language modes prior to C++20. If you are using these features prior to C++20, please update to ``-std=c++20``.
+  In LLVM 20, the C++20 synchronization library will be removed entirely in language modes prior to C++20.
+
 - TODO: The ``LIBCXX_ENABLE_ASSERTIONS`` CMake variable that was used to enable the safe mode has been deprecated and setting
   it triggers an error; use the ``LIBCXX_HARDENING_MODE`` CMake variable with the value ``extensive`` instead. Similarly,
   the ``_LIBCPP_ENABLE_ASSERTIONS`` macro has been deprecated (setting it to ``1`` still enables the extensive mode in
@@ -93,7 +97,7 @@ Deprecations and Removals
 - The ``_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS`` and ``_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_VOID_SPECIALIZATION``
   macros have been removed in LLVM 19.
 
-- TODO: The ``_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES`` and ``_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES`` macros have
+- The ``_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES`` and ``_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES`` macros have
   been removed in LLVM 19. C++17 and C++20 removed features can still be re-enabled individually.
 
 - The ``_LIBCPP_INLINE_VISIBILITY`` and ``_VSTD`` macros have been removed in LLVM 19.

diff --git a/libcxx/docs/UsingLibcxx.rst b/libcxx/docs/UsingLibcxx.rst
@@ -208,12 +208,6 @@ safety annotations.
 
 C++17 Specific Configuration Macros
 -----------------------------------
-**_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES**:
-  This macro is used to re-enable all the features removed in C++17. The effect
-  is equivalent to manually defining each macro listed below.
-  This macro is deprecated and will be removed in LLVM-19. Use the
-  individual macros listed below.
-
 **_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR**:
   This macro is used to re-enable `auto_ptr`.
 
@@ -238,12 +232,6 @@ C++20 Specific Configuration Macros
   This macro is used to re-enable the function
   ``std::shared_ptr<...>::unique()``.
 
-**_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES**:
-  This macro is used to re-enable all the features removed in C++20. The effect
-  is equivalent to manually defining each macro listed below.
-  This macro is deprecated and will be removed in LLVM-19. Use the
-  individual macros listed below.
-
 **_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS**:
   This macro is used to re-enable the `argument_type`, `result_type`,
   `first_argument_type`, and `second_argument_type` members of class

diff --git a/libcxx/include/__atomic/atomic.h b/libcxx/include/__atomic/atomic.h
@@ -462,22 +462,26 @@ atomic_wait_explicit(const atomic<_Tp>* __o, typename atomic<_Tp>::value_type __
 // atomic_notify_one
 
 template <class _Tp>
-_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void atomic_notify_one(volatile atomic<_Tp>* __o) _NOEXCEPT {
+_LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
+atomic_notify_one(volatile atomic<_Tp>* __o) _NOEXCEPT {
   __o->notify_one();
 }
 template <class _Tp>
-_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void atomic_notify_one(atomic<_Tp>* __o) _NOEXCEPT {
+_LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
+atomic_notify_one(atomic<_Tp>* __o) _NOEXCEPT {
   __o->notify_one();
 }
 
 // atomic_notify_all
 
 template <class _Tp>
-_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void atomic_notify_all(volatile atomic<_Tp>* __o) _NOEXCEPT {
+_LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
+atomic_notify_all(volatile atomic<_Tp>* __o) _NOEXCEPT {
   __o->notify_all();
 }
 template <class _Tp>
-_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void atomic_notify_all(atomic<_Tp>* __o) _NOEXCEPT {
+_LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
+atomic_notify_all(atomic<_Tp>* __o) _NOEXCEPT {
   __o->notify_all();
 }
 

diff --git a/libcxx/include/__atomic/atomic_flag.h b/libcxx/include/__atomic/atomic_flag.h
@@ -49,22 +49,26 @@ struct atomic_flag {
     __cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), __m);
   }
 
-  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void wait(bool __v, memory_order __m = memory_order_seq_cst) const
-      volatile _NOEXCEPT {
+  _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
+  wait(bool __v, memory_order __m = memory_order_seq_cst) const volatile _NOEXCEPT {
     std::__atomic_wait(*this, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);
   }
-  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
+  _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
   wait(bool __v, memory_order __m = memory_order_seq_cst) const _NOEXCEPT {
     std::__atomic_wait(*this, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);
   }
-  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() volatile _NOEXCEPT {
+  _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() volatile _NOEXCEPT {
+    std::__atomic_notify_one(*this);
+  }
+  _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() _NOEXCEPT {
     std::__atomic_notify_one(*this);
   }
-  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() _NOEXCEPT { std::__atomic_notify_one(*this); }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() volatile _NOEXCEPT {
     std::__atomic_notify_all(*this);
   }
-  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() _NOEXCEPT { std::__atomic_notify_all(*this); }
+  _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() _NOEXCEPT {
+    std::__atomic_notify_all(*this);
+  }
 
 #if _LIBCPP_STD_VER >= 20
   _LIBCPP_HIDE_FROM_ABI constexpr atomic_flag() _NOEXCEPT : __a_(false) {}
@@ -141,41 +145,43 @@ inline _LIBCPP_HIDE_FROM_ABI void atomic_flag_clear_explicit(atomic_flag* __o, m
   __o->clear(__m);
 }
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
+inline _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
 atomic_flag_wait(const volatile atomic_flag* __o, bool __v) _NOEXCEPT {
   __o->wait(__v);
 }
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
+inline _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
 atomic_flag_wait(const atomic_flag* __o, bool __v) _NOEXCEPT {
   __o->wait(__v);
 }
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
+inline _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
 atomic_flag_wait_explicit(const volatile atomic_flag* __o, bool __v, memory_order __m) _NOEXCEPT {
   __o->wait(__v, __m);
 }
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
+inline _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
 atomic_flag_wait_explicit(const atomic_flag* __o, bool __v, memory_order __m) _NOEXCEPT {
   __o->wait(__v, __m);
 }
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
+inline _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
 atomic_flag_notify_one(volatile atomic_flag* __o) _NOEXCEPT {
   __o->notify_one();
 }
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void atomic_flag_notify_one(atomic_flag* __o) _NOEXCEPT {
+inline _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
+atomic_flag_notify_one(atomic_flag* __o) _NOEXCEPT {
   __o->notify_one();
 }
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
+inline _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
 atomic_flag_notify_all(volatile atomic_flag* __o) _NOEXCEPT {
   __o->notify_all();
 }
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void atomic_flag_notify_all(atomic_flag* __o) _NOEXCEPT {
+inline _LIBCPP_DEPRECATED_ATOMIC_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_AVAILABILITY_SYNC void
+atomic_flag_notify_all(atomic_flag* __o) _NOEXCEPT {
   __o->notify_all();
 }
 

diff --git a/libcxx/include/__availability b/libcxx/include/__availability
@@ -160,6 +160,15 @@
 #  define _LIBCPP_AVAILABILITY_HAS_TZDB 1
 #  define _LIBCPP_AVAILABILITY_TZDB
 
+// These macros determine whether we assume that std::bad_function_call and
+// std::bad_expected_access provide a key function in the dylib. This allows
+// centralizing their vtable and typeinfo instead of having all TUs provide
+// a weak definition that then gets deduplicated.
+#  define _LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_KEY_FUNCTION 1
+#  define _LIBCPP_AVAILABILITY_BAD_FUNCTION_CALL_KEY_FUNCTION
+#  define _LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION 1
+#  define _LIBCPP_AVAILABILITY_BAD_EXPECTED_ACCESS_KEY_FUNCTION
+
 #elif defined(__APPLE__)
 
 #  define _LIBCPP_AVAILABILITY_HAS_BAD_OPTIONAL_ACCESS                                                                 \
@@ -290,6 +299,13 @@
 #  else
 #    define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 1
 #  endif
+
+#  define _LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_KEY_FUNCTION 0
+#  define _LIBCPP_AVAILABILITY_BAD_FUNCTION_CALL_KEY_FUNCTION __attribute__((unavailable))
+
+#  define _LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION 0
+#  define _LIBCPP_AVAILABILITY_BAD_EXPECTED_ACCESS_KEY_FUNCTION __attribute__((unavailable))
+
 #else
 
 // ...New vendors can add availability markup here...

diff --git a/libcxx/include/__chrono/formatter.h b/libcxx/include/__chrono/formatter.h
@@ -79,7 +79,7 @@ namespace __formatter {
 // small). Therefore a duration uses its own conversion.
 template <class _CharT, class _Rep, class _Period>
 _LIBCPP_HIDE_FROM_ABI void
-__format_sub_seconds(const chrono::duration<_Rep, _Period>& __value, basic_stringstream<_CharT>& __sstr) {
+__format_sub_seconds(basic_stringstream<_CharT>& __sstr, const chrono::duration<_Rep, _Period>& __value) {
   __sstr << std::use_facet<numpunct<_CharT>>(__sstr.getloc()).decimal_point();
 
   using __duration = chrono::duration<_Rep, _Period>;
@@ -110,13 +110,13 @@ __format_sub_seconds(const chrono::duration<_Rep, _Period>& __value, basic_strin
 }
 
 template <class _CharT, __is_time_point _Tp>
-_LIBCPP_HIDE_FROM_ABI void __format_sub_seconds(const _Tp& __value, basic_stringstream<_CharT>& __sstr) {
-  __formatter::__format_sub_seconds(__value.time_since_epoch(), __sstr);
+_LIBCPP_HIDE_FROM_ABI void __format_sub_seconds(basic_stringstream<_CharT>& __sstr, const _Tp& __value) {
+  __formatter::__format_sub_seconds(__sstr, __value.time_since_epoch());
 }
 
 template <class _CharT, class _Duration>
 _LIBCPP_HIDE_FROM_ABI void
-__format_sub_seconds(const chrono::hh_mm_ss<_Duration>& __value, basic_stringstream<_CharT>& __sstr) {
+__format_sub_seconds(basic_stringstream<_CharT>& __sstr, const chrono::hh_mm_ss<_Duration>& __value) {
   __sstr << std::use_facet<numpunct<_CharT>>(__sstr.getloc()).decimal_point();
   if constexpr (chrono::treat_as_floating_point_v<typename _Duration::rep>)
     std::format_to(std::ostreambuf_iterator<_CharT>{__sstr},
@@ -143,7 +143,7 @@ consteval bool __use_fraction() {
 }
 
 template <class _CharT>
-_LIBCPP_HIDE_FROM_ABI void __format_year(int __year, basic_stringstream<_CharT>& __sstr) {
+_LIBCPP_HIDE_FROM_ABI void __format_year(basic_stringstream<_CharT>& __sstr, int __year) {
   if (__year < 0) {
     __sstr << _CharT('-');
     __year = -__year;
@@ -159,7 +159,7 @@ _LIBCPP_HIDE_FROM_ABI void __format_year(int __year, basic_stringstream<_CharT>&
 }
 
 template <class _CharT>
-_LIBCPP_HIDE_FROM_ABI void __format_century(int __year, basic_stringstream<_CharT>& __sstr) {
+_LIBCPP_HIDE_FROM_ABI void __format_century(basic_stringstream<_CharT>& __sstr, int __year) {
   // TODO FMT Write an issue
   // [tab:time.format.spec]
   //   %C The year divided by 100 using floored division. If the result is a
@@ -172,7 +172,7 @@ _LIBCPP_HIDE_FROM_ABI void __format_century(int __year, basic_stringstream<_Char
 
 template <class _CharT, class _Tp>
 _LIBCPP_HIDE_FROM_ABI void __format_chrono_using_chrono_specs(
-    const _Tp& __value, basic_stringstream<_CharT>& __sstr, basic_string_view<_CharT> __chrono_specs) {
+    basic_stringstream<_CharT>& __sstr, const _Tp& __value, basic_string_view<_CharT> __chrono_specs) {
   tm __t              = std::__convert_to_tm<tm>(__value);
   const auto& __facet = std::use_facet<time_put<_CharT>>(__sstr.getloc());
   for (auto __it = __chrono_specs.begin(); __it != __chrono_specs.end(); ++__it) {
@@ -196,7 +196,7 @@ _LIBCPP_HIDE_FROM_ABI void __format_chrono_using_chrono_specs(
         // strftime's output is only defined in the range [00, 99].
         int __year = __t.tm_year + 1900;
         if (__year < 1000 || __year > 9999)
-          __formatter::__format_century(__year, __sstr);
+          __formatter::__format_century(__sstr, __year);
         else
           __facet.put(
               {__sstr}, __sstr, _CharT(' '), std::addressof(__t), std::to_address(__s), std::to_address(__it + 1));
@@ -242,7 +242,7 @@ _LIBCPP_HIDE_FROM_ABI void __format_chrono_using_chrono_specs(
         __facet.put(
             {__sstr}, __sstr, _CharT(' '), std::addressof(__t), std::to_address(__s), std::to_address(__it + 1));
         if constexpr (__use_fraction<_Tp>())
-          __formatter::__format_sub_seconds(__value, __sstr);
+          __formatter::__format_sub_seconds(__sstr, __value);
         break;
 
         // Unlike time_put and strftime the formatting library requires %Y
@@ -283,13 +283,13 @@ _LIBCPP_HIDE_FROM_ABI void __format_chrono_using_chrono_specs(
         // Depending on the platform's libc the range of supported years is
         // limited. Intead of of testing all conditions use the internal
         // implementation unconditionally.
-        __formatter::__format_year(__t.tm_year + 1900, __sstr);
+        __formatter::__format_year(__sstr, __t.tm_year + 1900);
         break;
 
       case _CharT('F'): {
         int __year = __t.tm_year + 1900;
         if (__year < 1000) {
-          __formatter::__format_year(__year, __sstr);
+          __formatter::__format_year(__sstr, __year);
           __sstr << std::format(_LIBCPP_STATICALLY_WIDEN(_CharT, "-{:02}-{:02}"), __t.tm_mon + 1, __t.tm_mday);
         } else
           __facet.put(
@@ -310,7 +310,7 @@ _LIBCPP_HIDE_FROM_ABI void __format_chrono_using_chrono_specs(
             ++__it;
             __facet.put(
                 {__sstr}, __sstr, _CharT(' '), std::addressof(__t), std::to_address(__s), std::to_address(__it + 1));
-            __formatter::__format_sub_seconds(__value, __sstr);
+            __formatter::__format_sub_seconds(__sstr, __value);
             break;
           }
         }
@@ -512,7 +512,7 @@ __format_chrono(const _Tp& __value,
     if constexpr (chrono::__is_duration<_Tp>::value) {
       if (__value < __value.zero())
         __sstr << _CharT('-');
-      __formatter::__format_chrono_using_chrono_specs(chrono::abs(__value), __sstr, __chrono_specs);
+      __formatter::__format_chrono_using_chrono_specs(__sstr, chrono::abs(__value), __chrono_specs);
       // TODO FMT When keeping the precision it will truncate the string.
       // Note that the behaviour what the precision does isn't specified.
       __specs.__precision_ = -1;
@@ -556,7 +556,7 @@ __format_chrono(const _Tp& __value,
           __sstr << _CharT('-');
       }
 
-      __formatter::__format_chrono_using_chrono_specs(__value, __sstr, __chrono_specs);
+      __formatter::__format_chrono_using_chrono_specs(__sstr, __value, __chrono_specs);
     }
   }
 

diff --git a/libcxx/include/__config b/libcxx/include/__config
@@ -16,17 +16,6 @@
 #  pragma GCC system_header
 #endif
 
-#if defined(_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES) && !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS)
-#  pragma clang deprecated(                                                                                            \
-      _LIBCPP_ENABLE_CXX17_REMOVED_FEATURES,                                                                           \
-      "_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES is deprecated in LLVM 18 and will be removed in LLVM 19")
-#endif
-#if defined(_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES) && !defined(_LIBCPP_DISABLE_DEPRECATION_WARNINGS)
-#  pragma clang deprecated(                                                                                            \
-      _LIBCPP_ENABLE_CXX20_REMOVED_FEATURES,                                                                           \
-      "_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES is deprecated in LLVM 18 and will be removed in LLVM 19")
-#endif
-
 #if defined(__apple_build_version__)
 // Given AppleClang XX.Y.Z, _LIBCPP_APPLE_CLANG_VER is XXYZ (e.g. AppleClang 14.0.3 => 1403)
 #  define _LIBCPP_COMPILER_CLANG_BASED
@@ -120,14 +109,11 @@
 #    define _LIBCPP_ABI_FIX_UNORDERED_NODE_POINTER_UB
 #    define _LIBCPP_ABI_FORWARD_LIST_REMOVE_NODE_POINTER_UB
 #    define _LIBCPP_ABI_FIX_UNORDERED_CONTAINER_SIZE_TYPE
-// Define a key function for `bad_function_call` in the library, to centralize
-// its vtable and typeinfo to libc++ rather than having all other libraries
-// using that class define their own copies.
-#    define _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
-// Override the default return value of exception::what() for
-// bad_function_call::what() with a string that is specific to
-// bad_function_call (see http://wg21.link/LWG2233). This is an ABI break
-// because it changes the vtable layout of bad_function_call.
+// Override the default return value of exception::what() for bad_function_call::what()
+// with a string that is specific to bad_function_call (see http://wg21.link/LWG2233).
+// This is an ABI break on platforms that sign and authenticate vtable function pointers
+// because it changes the mangling of the virtual function located in the vtable, which
+// changes how it gets signed.
 #    define _LIBCPP_ABI_BAD_FUNCTION_CALL_GOOD_WHAT_MESSAGE
 // Enable optimized version of __do_get_(un)signed which avoids redundant copies.
 #    define _LIBCPP_ABI_OPTIMIZED_LOCALE_NUM_GET
@@ -197,19 +183,6 @@
 #    if defined(__FreeBSD__) && __FreeBSD__ < 14
 #      define _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR
 #    endif
-// For XCOFF linkers, we have problems if we see a weak hidden version of a symbol
-// in user code (like you get with -fvisibility-inlines-hidden) and then a strong def
-// in the library, so we need to always rely on the library version.
-#    if defined(_AIX)
-#      define _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
-#    endif
-#  endif
-
-#  if defined(_LIBCPP_BUILDING_LIBRARY) || _LIBCPP_ABI_VERSION >= 2
-// Define a key function for `bad_function_call` in the library, to centralize
-// its vtable and typeinfo to libc++ rather than having all other libraries
-// using that class define their own copies.
-#    define _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
 #  endif
 
 // We had some bugs where we use [[no_unique_address]] together with construct_at,
@@ -972,6 +945,14 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_DEPRECATED_(m)
 #  endif
 
+#  if _LIBCPP_STD_VER < 20
+#    define _LIBCPP_DEPRECATED_ATOMIC_SYNC                                                                             \
+      _LIBCPP_DEPRECATED_("The C++20 synchronization library has been deprecated prior to C++20. Please update to "    \
+                          "using -std=c++20 if you need to use these facilities.")
+#  else
+#    define _LIBCPP_DEPRECATED_ATOMIC_SYNC /* nothing */
+#  endif
+
 #  if !defined(_LIBCPP_CXX03_LANG)
 #    define _LIBCPP_DEPRECATED_IN_CXX11 _LIBCPP_DEPRECATED
 #  else
@@ -1238,21 +1219,6 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_IF_WIDE_CHARACTERS(...) __VA_ARGS__
 #  endif
 
-#  if defined(_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES)
-#    define _LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR
-#    define _LIBCPP_ENABLE_CXX17_REMOVED_BINDERS
-#    define _LIBCPP_ENABLE_CXX17_REMOVED_RANDOM_SHUFFLE
-#    define _LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS
-#    define _LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION
-#  endif // _LIBCPP_ENABLE_CXX17_REMOVED_FEATURES
-
-#  if defined(_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES)
-#    define _LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS
-#    define _LIBCPP_ENABLE_CXX20_REMOVED_NEGATORS
-#    define _LIBCPP_ENABLE_CXX20_REMOVED_RAW_STORAGE_ITERATOR
-#    define _LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS
-#  endif // _LIBCPP_ENABLE_CXX20_REMOVED_FEATURES
-
 // clang-format off
 #  define _LIBCPP_PUSH_MACROS _Pragma("push_macro(\"min\")") _Pragma("push_macro(\"max\")") _Pragma("push_macro(\"refresh\")") _Pragma("push_macro(\"move\")") _Pragma("push_macro(\"erase\")")
 #  define _LIBCPP_POP_MACROS _Pragma("pop_macro(\"min\")") _Pragma("pop_macro(\"max\")") _Pragma("pop_macro(\"refresh\")") _Pragma("pop_macro(\"move\")") _Pragma("pop_macro(\"erase\")")

diff --git a/libcxx/include/__expected/bad_expected_access.h b/libcxx/include/__expected/bad_expected_access.h
@@ -9,6 +9,7 @@
 #ifndef _LIBCPP___EXPECTED_BAD_EXPECTED_ACCESS_H
 #define _LIBCPP___EXPECTED_BAD_EXPECTED_ACCESS_H
 
+#include <__availability>
 #include <__config>
 #include <__exception/exception.h>
 #include <__utility/move.h>
@@ -28,9 +29,11 @@ template <class _Err>
 class bad_expected_access;
 
 _LIBCPP_DIAGNOSTIC_PUSH
+#  if !_LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION
 _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wweak-vtables")
+#  endif
 template <>
-class bad_expected_access<void> : public exception {
+class _LIBCPP_EXPORTED_FROM_ABI bad_expected_access<void> : public exception {
 protected:
   _LIBCPP_HIDE_FROM_ABI bad_expected_access() noexcept                                      = default;
   _LIBCPP_HIDE_FROM_ABI bad_expected_access(const bad_expected_access&) noexcept            = default;
@@ -40,11 +43,11 @@ class bad_expected_access<void> : public exception {
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL ~bad_expected_access() override                             = default;
 
 public:
-  // The way this has been designed (by using a class template below) means that we'll already
-  // have a profusion of these vtables in TUs, and the dynamic linker will already have a bunch
-  // of work to do. So it is not worth hiding the <void> specialization in the dylib, given that
-  // it adds deployment target restrictions.
+#  if _LIBCPP_AVAILABILITY_HAS_BAD_EXPECTED_ACCESS_KEY_FUNCTION
+  const char* what() const noexcept override;
+#  else
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL const char* what() const noexcept override { return "bad access to std::expected"; }
+#  endif
 };
 _LIBCPP_DIAGNOSTIC_POP
 

diff --git a/libcxx/include/__functional/function.h b/libcxx/include/__functional/function.h
@@ -11,6 +11,7 @@
 #define _LIBCPP___FUNCTIONAL_FUNCTION_H
 
 #include <__assert>
+#include <__availability>
 #include <__config>
 #include <__exception/exception.h>
 #include <__functional/binary_function.h>
@@ -55,7 +56,9 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 // bad_function_call
 
 _LIBCPP_DIAGNOSTIC_PUSH
+#  if !_LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_KEY_FUNCTION
 _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wweak-vtables")
+#  endif
 class _LIBCPP_EXPORTED_FROM_ABI bad_function_call : public exception {
 public:
   _LIBCPP_HIDE_FROM_ABI bad_function_call() _NOEXCEPT                                    = default;
@@ -64,7 +67,7 @@ class _LIBCPP_EXPORTED_FROM_ABI bad_function_call : public exception {
 // Note that when a key function is not used, every translation unit that uses
 // bad_function_call will end up containing a weak definition of the vtable and
 // typeinfo.
-#  ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
+#  if _LIBCPP_AVAILABILITY_HAS_BAD_FUNCTION_CALL_KEY_FUNCTION
   ~bad_function_call() _NOEXCEPT override;
 #  else
   _LIBCPP_HIDE_FROM_ABI_VIRTUAL ~bad_function_call() _NOEXCEPT override {}

diff --git a/libcxx/include/__fwd/ios.h b/libcxx/include/__fwd/ios.h
@@ -18,6 +18,8 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+class _LIBCPP_EXPORTED_FROM_ABI ios_base;
+
 template <class _CharT, class _Traits = char_traits<_CharT> >
 class _LIBCPP_TEMPLATE_VIS basic_ios;
 

diff --git a/libcxx/include/barrier b/libcxx/include/barrier
@@ -257,7 +257,7 @@ public:
 #  endif // !_LIBCPP_HAS_NO_TREE_BARRIER
 
 template <class _CompletionF = __empty_completion>
-class barrier {
+class _LIBCPP_DEPRECATED_ATOMIC_SYNC barrier {
   __barrier_base<_CompletionF> __b_;
 
 public:

diff --git a/libcxx/include/iosfwd b/libcxx/include/iosfwd
@@ -25,7 +25,6 @@ template<>            struct char_traits<wchar_t>;
 
 template<class T>     class allocator;
 
-class ios_base;
 template <class charT, class traits = char_traits<charT> > class basic_ios;
 
 template <class charT, class traits = char_traits<charT> > class basic_streambuf;
@@ -124,8 +123,6 @@ using wosyncstream = basic_osyncstream<wchar_t>;  // C++20
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-class _LIBCPP_EXPORTED_FROM_ABI ios_base;
-
 template <class _CharT, class _Traits = char_traits<_CharT> >
 class _LIBCPP_TEMPLATE_VIS istreambuf_iterator;
 template <class _CharT, class _Traits = char_traits<_CharT> >

diff --git a/libcxx/include/latch b/libcxx/include/latch
@@ -66,7 +66,7 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-class latch {
+class _LIBCPP_DEPRECATED_ATOMIC_SYNC latch {
   __atomic_base<ptrdiff_t> __a_;
 
 public:

diff --git a/libcxx/include/semaphore b/libcxx/include/semaphore
@@ -127,7 +127,7 @@ private:
 };
 
 template <ptrdiff_t __least_max_value = _LIBCPP_SEMAPHORE_MAX>
-class counting_semaphore {
+class _LIBCPP_DEPRECATED_ATOMIC_SYNC counting_semaphore {
   __atomic_semaphore_base __semaphore_;
 
 public:
@@ -172,7 +172,9 @@ public:
   }
 };
 
-using binary_semaphore = counting_semaphore<1>;
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+using binary_semaphore _LIBCPP_DEPRECATED_ATOMIC_SYNC = counting_semaphore<1>;
+_LIBCPP_SUPPRESS_DEPRECATED_POP
 
 _LIBCPP_END_NAMESPACE_STD
 

diff --git a/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -575,6 +575,7 @@
 {'is_defined': True, 'name': '__ZNKSt3__118__time_get_storageIcE15__do_date_orderEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNKSt3__118__time_get_storageIwE15__do_date_orderEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNKSt3__119__shared_weak_count13__get_deleterERKSt9type_info', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNKSt3__119bad_expected_accessIvE4whatEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNKSt3__120__codecvt_utf8_utf16IDiE10do_unshiftER11__mbstate_tPcS4_RS4_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNKSt3__120__codecvt_utf8_utf16IDiE11do_encodingEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNKSt3__120__codecvt_utf8_utf16IDiE13do_max_lengthEv', 'type': 'FUNC'}
@@ -2073,6 +2074,7 @@
 {'is_defined': True, 'name': '__ZTINSt3__117moneypunct_bynameIwLb1EEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__118basic_stringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__119__shared_weak_countE', 'size': 0, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '__ZTINSt3__119bad_expected_accessIvEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__119basic_istringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__119basic_ostringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTINSt3__120__codecvt_utf8_utf16IDiEE', 'size': 0, 'type': 'OBJECT'}
@@ -2264,6 +2266,7 @@
 {'is_defined': True, 'name': '__ZTSNSt3__117moneypunct_bynameIwLb0EEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__117moneypunct_bynameIwLb1EEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__118basic_stringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '__ZTSNSt3__119bad_expected_accessIvEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__119basic_istringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__119basic_ostringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTSNSt3__13pmr15memory_resourceE', 'size': 0, 'type': 'OBJECT'}
@@ -2482,6 +2485,7 @@
 {'is_defined': True, 'name': '__ZTVNSt3__117moneypunct_bynameIwLb1EEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__118basic_stringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__119__shared_weak_countE', 'size': 0, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '__ZTVNSt3__119bad_expected_accessIvEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__119basic_istringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__119basic_ostringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZTVNSt3__120__codecvt_utf8_utf16IDiEE', 'size': 0, 'type': 'OBJECT'}

diff --git a/libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -209,6 +209,7 @@
 {'is_defined': True, 'name': '_ZNKSt6__ndk118__time_get_storageIcE15__do_date_orderEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNKSt6__ndk118__time_get_storageIwE15__do_date_orderEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNKSt6__ndk119__shared_weak_count13__get_deleterERKSt9type_info', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNKSt6__ndk119bad_expected_accessIvE4whatEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNKSt6__ndk120__codecvt_utf8_utf16IDiE10do_unshiftER9mbstate_tPcS4_RS4_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNKSt6__ndk120__codecvt_utf8_utf16IDiE11do_encodingEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNKSt6__ndk120__codecvt_utf8_utf16IDiE13do_max_lengthEv', 'type': 'FUNC'}
@@ -1722,6 +1723,7 @@
 {'is_defined': True, 'name': '_ZTINSt6__ndk118__time_get_storageIwEE', 'size': 12, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTINSt6__ndk118basic_stringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 12, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTINSt6__ndk119__shared_weak_countE', 'size': 24, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '_ZTINSt6__ndk119bad_expected_accessIvEE', 'size': 12, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTINSt6__ndk119basic_istringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 12, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTINSt6__ndk119basic_ostringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 12, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTINSt6__ndk120__codecvt_utf8_utf16IDiEE', 'size': 12, 'type': 'OBJECT'}
@@ -1958,6 +1960,7 @@
 {'is_defined': True, 'name': '_ZTSNSt6__ndk118__time_get_storageIwEE', 'size': 35, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTSNSt6__ndk118basic_stringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 72, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTSNSt6__ndk119__shared_weak_countE', 'size': 33, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '_ZTSNSt6__ndk119bad_expected_accessIvEE', 'size': 36, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTSNSt6__ndk119basic_istringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 73, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTSNSt6__ndk119basic_ostringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 73, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTSNSt6__ndk120__codecvt_utf8_utf16IDiEE', 'size': 38, 'type': 'OBJECT'}
@@ -2188,6 +2191,7 @@
 {'is_defined': True, 'name': '_ZTVNSt6__ndk117moneypunct_bynameIwLb1EEE', 'size': 56, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTVNSt6__ndk118basic_stringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 60, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTVNSt6__ndk119__shared_weak_countE', 'size': 28, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '_ZTVNSt6__ndk119bad_expected_accessIvEE', 'size': 20, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTVNSt6__ndk119basic_istringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 40, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTVNSt6__ndk119basic_ostringstreamIcNS_11char_traitsIcEENS_9allocatorIcEEEE', 'size': 40, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZTVNSt6__ndk120__codecvt_utf8_utf16IDiEE', 'size': 48, 'type': 'OBJECT'}