From 49d70380a6a95e4039f6b5e5ccce09671d5b4796 Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Sun, 2 Aug 2026 02:56:39 +0800
Subject: [CodeGen] Add machine metadata graphs

Model ordered function-local metadata tuples with explicit embedded-IR and MachineFunction reference scopes. Preserve slot zero, distinct nodes, forward references, and cyclic graphs while verifying function-local closure and cloning the graph deterministically.
---
 backend/lib/CodeGen/MachineMetadata.cpp | 114 ++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 backend/lib/CodeGen/MachineMetadata.cpp

(limited to 'backend/lib/CodeGen/MachineMetadata.cpp')

diff --git a/backend/lib/CodeGen/MachineMetadata.cpp b/backend/lib/CodeGen/MachineMetadata.cpp
new file mode 100644
index 0000000..24a04e9
--- /dev/null
+++ b/backend/lib/CodeGen/MachineMetadata.cpp
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "rcc/CodeGen/MachineMetadata.h"
+
+#include <cstddef>
+#include <string>
+#include <unordered_set>
+#include <utility>
+
+namespace rcc {
+namespace {
+
+[[nodiscard]] Expected<void> verifyNodeElements(const MachineMetadataNode &Node) {
+  for (const MachineMetadataElement &Element : Node.Elements) {
+    if (!Element.isValid()) {
+      return makeUnexpected(ErrorCode::VerificationError,
+                            "machine metadata tuple contains an invalid element");
+    }
+    const MachineMetadataReference *Reference = Element.reference();
+    if (Reference != nullptr && !Reference->isValid()) {
+      return makeUnexpected(ErrorCode::VerificationError,
+                            "machine metadata tuple contains an invalid reference");
+    }
+  }
+  return {};
+}
+
+} // namespace
+
+Expected<MachineMetadataElement>
+MachineMetadataElement::reference(MachineMetadataReference Reference) {
+  if (!Reference.isValid()) {
+    return makeUnexpected(ErrorCode::InvalidArgument,
+                          "machine metadata element reference must be valid");
+  }
+  return MachineMetadataElement(Reference);
+}
+
+MachineMetadataElement MachineMetadataElement::string(std::string Value) {
+  return MachineMetadataElement(std::move(Value));
+}
+
+Expected<void> MachineMetadataInfo::addNode(MachineMetadataNode Node) {
+  auto Verification = verifyNodeElements(Node);
+  if (!Verification)
+    return std::unexpected(Verification.error());
+  if (SlotToIndex.contains(Node.Slot)) {
+    return makeUnexpected(ErrorCode::InvalidArgument, "machine metadata slot is already defined");
+  }
+
+  const std::size_t Index = Nodes.size();
+  SlotToIndex.emplace(Node.Slot, Index);
+  Nodes.push_back(std::move(Node));
+  return {};
+}
+
+const MachineMetadataNode *MachineMetadataInfo::node(std::uint32_t Slot) const noexcept {
+  const auto Position = SlotToIndex.find(Slot);
+  if (Position == SlotToIndex.end())
+    return nullptr;
+  return &Nodes[Position->second];
+}
+
+Expected<void> MachineMetadataInfo::verify() const {
+  if (SlotToIndex.size() != Nodes.size()) {
+    return makeUnexpected(ErrorCode::VerificationError,
+                          "machine metadata slot index has an inconsistent size");
+  }
+
+  std::unordered_set<std::uint32_t> Slots;
+  for (std::size_t Index = 0; Index < Nodes.size(); ++Index) {
+    const MachineMetadataNode &Node = Nodes[Index];
+    if (!Slots.insert(Node.Slot).second) {
+      return makeUnexpected(ErrorCode::VerificationError,
+                            "machine metadata contains duplicate slot definitions");
+    }
+    const auto Position = SlotToIndex.find(Node.Slot);
+    if (Position == SlotToIndex.end() || Position->second != Index) {
+      return makeUnexpected(ErrorCode::VerificationError,
+                            "machine metadata slot index is inconsistent");
+    }
+    auto ElementVerification = verifyNodeElements(Node);
+    if (!ElementVerification)
+      return ElementVerification;
+  }
+
+  for (const MachineMetadataNode &Node : Nodes) {
+    for (const MachineMetadataElement &Element : Node.Elements) {
+      const MachineMetadataReference *Reference = Element.reference();
+      if (Reference != nullptr && Reference->scope() == MachineMetadataScope::MachineFunction &&
+          !Slots.contains(Reference->slot())) {
+        return makeUnexpected(ErrorCode::VerificationError,
+                              "machine metadata tuple references an undefined function slot");
+      }
+    }
+  }
+  return {};
+}
+
+Expected<MachineMetadataInfo> MachineMetadataInfo::clone() const {
+  auto Verification = verify();
+  if (!Verification)
+    return std::unexpected(Verification.error());
+
+  MachineMetadataInfo Result;
+  for (const MachineMetadataNode &Node : Nodes) {
+    auto AddResult = Result.addNode(Node);
+    if (!AddResult)
+      return std::unexpected(AddResult.error());
+  }
+  return Result;
+}
+
+} // namespace rcc
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