[clang] [clang] Implement a bitwise_copyable builtin type trait. (PR #86512)

[Ilya Biryukov via cfe-commits]

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@@ -2718,6 +2718,36 @@ bool QualType::isTriviallyCopyableType(const ASTContext &Context) const {
                                      /*IsCopyConstructible=*/false);
 }
 
+bool QualType::isBitwiseCloneableType(const ASTContext & Context) const {
+  QualType CanonicalType = getCanonicalType();
+  if (CanonicalType->isIncompleteType() || CanonicalType->isDependentType())
+    return false;
+  // Trivially copyable types are bitwise clonable, e.g. scalar types.
+  if (CanonicalType.isTriviallyCopyableType(Context))
+    return true;
+
+  if (CanonicalType->isArrayType())
+    return Context.getBaseElementType(CanonicalType)
+        .isBitwiseCloneableType(Context);
+
+  if (const auto *RD = CanonicalType->getAsCXXRecordDecl()) {
+    for (auto Base : RD->bases())
+      if (!Base.getType().isBitwiseCloneableType(Context))
+        return false;
+    for (auto VBase : RD->vbases())
+      if (!VBase.getType().isBitwiseCloneableType(Context))
+        return false;
+
+    for (auto *const Field : RD->fields()) {
+      QualType T = Context.getBaseElementType(Field->getType());
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ilya-biryukov wrote:

Why do we need to call `getBaseElementType` here?
Why not simply call the `isBitwiseCloneableType(Field->getType())`?

https://github.com/llvm/llvm-project/pull/86512