[CodeGen] Add constant and jump table state

Add stable, tombstone-preserving MachineConstantPool and MachineJumpTableInfo ownership. Define the versioned TargetConstant contract and integrate all table references with builders, verification, and deterministic deep cloning.

1 files changed, 183 insertions, 0 deletions

diff --git a/backend/include/rcc/CodeGen/MachineConstantPool.h b/backend/include/rcc/CodeGen/MachineConstantPool.h
new file mode 100644
index 0000000..cc9ae04
--- /dev/null
+++ b/backend/include/rcc/CodeGen/MachineConstantPool.h
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef RCC_CODEGEN_MACHINECONSTANTPOOL_H
+#define RCC_CODEGEN_MACHINECONSTANTPOOL_H
+
+#include "rcc/CodeGen/MachineIRTypes.h"
+#include "rcc/CodeGen/MachineMemOperand.h"
+#include "rcc/CodeGen/TargetConstant.h"
+#include "rcc/Support/Error.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <span>
+#include <string>
+#include <utility>
+#include <variant>
+#include <vector>
+
+namespace rcc {
+
+enum class ConstantPoolEntryKind : std::uint8_t {
+  Generic,
+  Target,
+  SymbolDifference,
+  BlockAddress,
+  TargetExpression,
+};
+
+enum class ConstantPoolMergeKind : std::uint8_t {
+  Never,
+  Exact,
+};
+
+enum class ConstantPoolRelocationMode : std::uint8_t {
+  None,
+  Static,
+  PositionIndependent,
+  Target,
+};
+
+enum class ConstantPoolSectionKind : std::uint8_t {
+  TargetDefault,
+  ReadOnly,
+  MergeableReadOnly,
+  Data,
+  TextAdjacent,
+  Target,
+  Count,
+};
+
+struct ConstantPoolPlacement final {
+  ConstantPoolSectionKind Section = ConstantPoolSectionKind::TargetDefault;
+  bool UniqueSection = false;
+  std::optional<std::uint64_t> MaximumDistance;
+  std::uint64_t TargetFlags = 0;
+
+  friend bool operator==(const ConstantPoolPlacement &Left,
+                         const ConstantPoolPlacement &Right) = default;
+};
+
+struct GenericConstantData final {
+  std::string TypeIdentity;
+  std::vector<std::byte> Bytes;
+
+  friend bool operator==(const GenericConstantData &Left,
+                         const GenericConstantData &Right) = default;
+};
+
+struct SymbolDifferenceConstant final {
+  std::string Minuend;
+  std::string Subtrahend;
+  std::int64_t Addend = 0;
+
+  friend bool operator==(const SymbolDifferenceConstant &Left,
+                         const SymbolDifferenceConstant &Right) = default;
+};
+
+struct BlockAddressConstant final {
+  std::string FunctionName;
+  std::string BlockName;
+  std::int64_t Addend = 0;
+
+  friend bool operator==(const BlockAddressConstant &Left,
+                         const BlockAddressConstant &Right) = default;
+};
+
+struct TargetExpressionConstant final {
+  TargetConstant Expression;
+};
+
+using MachineConstantPoolValue =
+    std::variant<GenericConstantData, TargetConstant, SymbolDifferenceConstant,
+                 BlockAddressConstant, TargetExpressionConstant>;
+
+struct MachineConstantPoolEntryDesc final {
+  MachineConstantPoolEntryDesc() = default;
+  MachineConstantPoolEntryDesc(const MachineConstantPoolEntryDesc &) = delete;
+  MachineConstantPoolEntryDesc &operator=(const MachineConstantPoolEntryDesc &) = delete;
+  MachineConstantPoolEntryDesc(MachineConstantPoolEntryDesc &&) noexcept = default;
+  MachineConstantPoolEntryDesc &operator=(MachineConstantPoolEntryDesc &&) noexcept = default;
+  ~MachineConstantPoolEntryDesc() = default;
+
+  MachineConstantPoolValue Value;
+  std::uint64_t Size = 0;
+  Alignment Align;
+  ConstantPoolMergeKind Merge = ConstantPoolMergeKind::Never;
+  ConstantPoolRelocationMode Relocation = ConstantPoolRelocationMode::None;
+  ConstantPoolPlacement Placement;
+
+  [[nodiscard]] ConstantPoolEntryKind kind() const noexcept;
+  [[nodiscard]] Expected<void> verify() const;
+  [[nodiscard]] Expected<MachineConstantPoolEntryDesc> clone() const;
+  [[nodiscard]] bool semanticallyEquals(const MachineConstantPoolEntryDesc &Other) const noexcept;
+};
+
+class MachineConstantPoolEntry final {
+public:
+  [[nodiscard]] ConstantPoolIndex index() const noexcept {
+    return Index;
+  }
+
+  [[nodiscard]] bool isTombstone() const noexcept {
+    return std::holds_alternative<std::monostate>(Description);
+  }
+
+  [[nodiscard]] const MachineConstantPoolEntryDesc *description() const noexcept {
+    return std::get_if<MachineConstantPoolEntryDesc>(&Description);
+  }
+
+  [[nodiscard]] Expected<MachineConstantPoolEntryDesc> cloneDescription() const;
+
+private:
+  MachineConstantPoolEntry(ConstantPoolIndex Index, MachineConstantPoolEntryDesc Description)
+      : Index(Index), Description(std::move(Description)) {}
+
+  ConstantPoolIndex Index;
+  std::variant<std::monostate, MachineConstantPoolEntryDesc> Description;
+
+  friend class MachineConstantPool;
+};
+
+class MachineConstantPool final {
+public:
+  MachineConstantPool() = default;
+  MachineConstantPool(const MachineConstantPool &) = delete;
+  MachineConstantPool &operator=(const MachineConstantPool &) = delete;
+  MachineConstantPool(MachineConstantPool &&) noexcept = default;
+  MachineConstantPool &operator=(MachineConstantPool &&) noexcept = default;
+  ~MachineConstantPool() = default;
+
+  [[nodiscard]] Expected<ConstantPoolIndex> addEntry(MachineConstantPoolEntryDesc Description);
+  [[nodiscard]] Expected<void> updateEntry(ConstantPoolIndex Index,
+                                           MachineConstantPoolEntryDesc Description);
+  [[nodiscard]] Expected<void> eraseEntry(ConstantPoolIndex Index);
+
+  [[nodiscard]] const MachineConstantPoolEntry *entry(ConstantPoolIndex Index) const noexcept;
+  [[nodiscard]] std::span<const MachineConstantPoolEntry> entries() const noexcept {
+    return Entries;
+  }
+
+  [[nodiscard]] std::size_t liveEntryCount() const noexcept;
+
+  [[nodiscard]] bool isFrozen() const noexcept {
+    return Frozen;
+  }
+
+  [[nodiscard]] Expected<void> freeze();
+  [[nodiscard]] Expected<void> verify() const;
+
+private:
+  [[nodiscard]] Expected<MachineConstantPoolEntry *> mutableEntry(ConstantPoolIndex Index);
+  [[nodiscard]] const MachineConstantPoolEntry *
+  findEquivalent(const MachineConstantPoolEntryDesc &Description,
+                 std::optional<ConstantPoolIndex> Excluded = std::nullopt) const noexcept;
+
+  std::vector<MachineConstantPoolEntry> Entries;
+  bool Frozen = false;
+};
+
+} // namespace rcc
+
+#endif // RCC_CODEGEN_MACHINECONSTANTPOOL_H