1 files changed, 153 insertions, 0 deletions
diff --git a/contrib/llvm-project/lldb/source/Plugins/Language/CPlusPlus/LibCxxSpan.cpp b/contrib/llvm-project/lldb/source/Plugins/Language/CPlusPlus/LibCxxSpan.cpp
new file mode 100644
index 000000000000..9895f336bfd0
--- /dev/null
+++ b/contrib/llvm-project/lldb/source/Plugins/Language/CPlusPlus/LibCxxSpan.cpp
@@ -0,0 +1,153 @@
+//===-- LibCxxSpan.cpp ----------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "LibCxx.h"
+
+#include "lldb/Core/ValueObject.h"
+#include "lldb/DataFormatters/FormattersHelpers.h"
+#include "lldb/Utility/ConstString.h"
+#include "llvm/ADT/APSInt.h"
+#include <optional>
+
+using namespace lldb;
+using namespace lldb_private;
+using namespace lldb_private::formatters;
+
+namespace lldb_private {
+namespace formatters {
+
+class LibcxxStdSpanSyntheticFrontEnd : public SyntheticChildrenFrontEnd {
+public:
+  LibcxxStdSpanSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);
+
+  ~LibcxxStdSpanSyntheticFrontEnd() override = default;
+
+  llvm::Expected<uint32_t> CalculateNumChildren() override;
+
+  lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override;
+
+  /// Determines properties of the std::span<> associated with this object
+  //
+  // std::span can either be instantiated with a compile-time known
+  // extent or a std::dynamic_extent (this is the default if only the
+  // type template argument is provided). The layout of std::span
+  // depends on whether the extent is dynamic or not. For static
+  // extents (e.g., std::span<int, 9>):
+  //
+  // (std::__1::span<const int, 9>) s = {
+  //   __data = 0x000000016fdff494
+  // }
+  //
+  // For dynamic extents, e.g., std::span<int>, the layout is:
+  //
+  // (std::__1::span<const int, 18446744073709551615>) s = {
+  //   __data = 0x000000016fdff494
+  //   __size = 6
+  // }
+  //
+  // This function checks for a '__size' member to determine the number
+  // of elements in the span. If no such member exists, we get the size
+  // from the only other place it can be: the template argument.
+  lldb::ChildCacheState Update() override;
+
+  bool MightHaveChildren() override;
+
+  size_t GetIndexOfChildWithName(ConstString name) override;
+
+private:
+  ValueObject *m_start = nullptr; ///< First element of span. Held, not owned.
+  CompilerType m_element_type{};  ///< Type of span elements.
+  size_t m_num_elements = 0;      ///< Number of elements in span.
+  uint32_t m_element_size = 0;    ///< Size in bytes of each span element.
+};
+
+lldb_private::formatters::LibcxxStdSpanSyntheticFrontEnd::
+    LibcxxStdSpanSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
+    : SyntheticChildrenFrontEnd(*valobj_sp) {
+  if (valobj_sp)
+    Update();
+}
+
+llvm::Expected<uint32_t> lldb_private::formatters::
+    LibcxxStdSpanSyntheticFrontEnd::CalculateNumChildren() {
+  return m_num_elements;
+}
+
+lldb::ValueObjectSP
+lldb_private::formatters::LibcxxStdSpanSyntheticFrontEnd::GetChildAtIndex(
+    uint32_t idx) {
+  if (!m_start)
+    return {};
+
+  uint64_t offset = idx * m_element_size;
+  offset = offset + m_start->GetValueAsUnsigned(0);
+  StreamString name;
+  name.Printf("[%" PRIu64 "]", (uint64_t)idx);
+  return CreateValueObjectFromAddress(name.GetString(), offset,
+                                      m_backend.GetExecutionContextRef(),
+                                      m_element_type);
+}
+
+lldb::ChildCacheState
+lldb_private::formatters::LibcxxStdSpanSyntheticFrontEnd::Update() {
+  // Get element type.
+  ValueObjectSP data_type_finder_sp = GetChildMemberWithName(
+      m_backend, {ConstString("__data_"), ConstString("__data")});
+  if (!data_type_finder_sp)
+    return lldb::ChildCacheState::eRefetch;
+
+  m_element_type = data_type_finder_sp->GetCompilerType().GetPointeeType();
+
+  // Get element size.
+  if (std::optional<uint64_t> size = m_element_type.GetByteSize(nullptr)) {
+    m_element_size = *size;
+
+    // Get data.
+    if (m_element_size > 0) {
+      m_start = data_type_finder_sp.get();
+    }
+
+    // Get number of elements.
+    if (auto size_sp = GetChildMemberWithName(
+            m_backend, {ConstString("__size_"), ConstString("__size")})) {
+      m_num_elements = size_sp->GetValueAsUnsigned(0);
+    } else if (auto arg =
+                   m_backend.GetCompilerType().GetIntegralTemplateArgument(1)) {
+
+      m_num_elements = arg->value.getLimitedValue();
+    }
+  }
+
+  return lldb::ChildCacheState::eReuse;
+}
+
+bool lldb_private::formatters::LibcxxStdSpanSyntheticFrontEnd::
+    MightHaveChildren() {
+  return true;
+}
+
+size_t lldb_private::formatters::LibcxxStdSpanSyntheticFrontEnd::
+    GetIndexOfChildWithName(ConstString name) {
+  if (!m_start)
+    return UINT32_MAX;
+  return ExtractIndexFromString(name.GetCString());
+}
+
+lldb_private::SyntheticChildrenFrontEnd *
+LibcxxStdSpanSyntheticFrontEndCreator(CXXSyntheticChildren *,
+                                      lldb::ValueObjectSP valobj_sp) {
+  if (!valobj_sp)
+    return nullptr;
+  CompilerType type = valobj_sp->GetCompilerType();
+  if (!type.IsValid() || type.GetNumTemplateArguments() != 2)
+    return nullptr;
+  return new LibcxxStdSpanSyntheticFrontEnd(valobj_sp);
+}
+
+} // namespace formatters
+} // namespace lldb_private