1 files changed, 259 insertions, 0 deletions
diff --git a/backend/include/rcc/CodeGen/TargetConstant.h b/backend/include/rcc/CodeGen/TargetConstant.h
new file mode 100644
index 0000000..37f352e
--- /dev/null
+++ b/backend/include/rcc/CodeGen/TargetConstant.h
@@ -0,0 +1,259 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef RCC_CODEGEN_TARGETCONSTANT_H
+#define RCC_CODEGEN_TARGETCONSTANT_H
+
+#include "rcc/CodeGen/MachineIRTypes.h"
+#include "rcc/CodeGen/MachineMemOperand.h"
+#include "rcc/Support/Error.h"
+
+#include <concepts>
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <optional>
+#include <span>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+namespace rcc {
+
+struct TargetConstantFixup final {
+  std::uint64_t Offset = 0;
+  TargetRelocationKindID Kind;
+  std::string Symbol;
+  std::int64_t Addend = 0;
+
+  friend bool operator==(const TargetConstantFixup &Left,
+                         const TargetConstantFixup &Right) = default;
+};
+
+struct TargetConstantEmission final {
+  std::vector<std::byte> Bytes;
+  std::vector<TargetConstantFixup> Fixups;
+
+  [[nodiscard]] Expected<void> verify() const;
+
+  friend bool operator==(const TargetConstantEmission &Left,
+                         const TargetConstantEmission &Right) = default;
+};
+
+struct EncodedTargetConstant final {
+  TargetConstantTypeID TypeID;
+  std::uint32_t Version = 0;
+  std::vector<std::byte> Payload;
+
+  friend bool operator==(const EncodedTargetConstant &Left,
+                         const EncodedTargetConstant &Right) = default;
+};
+
+template <typename ValueT>
+concept TargetConstantValue =
+    std::move_constructible<ValueT> &&
+    requires(const ValueT &Value, const ValueT &Other, std::uint32_t Version,
+             std::span<const std::byte> Payload, std::string_view Text) {
+      { ValueT::stableTypeID() } -> std::same_as<TargetConstantTypeID>;
+      { ValueT::schemaVersion() } -> std::same_as<std::uint32_t>;
+      { Value.verify() } -> std::same_as<Expected<void>>;
+      { Value.clone() } -> std::same_as<Expected<ValueT>>;
+      { Value.stableHash() } -> std::same_as<std::uint64_t>;
+      { Value.print() } -> std::same_as<std::string>;
+      { Value.encode() } -> std::same_as<Expected<std::vector<std::byte>>>;
+      { Value.emit() } -> std::same_as<Expected<TargetConstantEmission>>;
+      { Value.requiredAlignment() } -> std::same_as<Alignment>;
+      { Value.relocationKind() } -> std::same_as<std::optional<TargetRelocationKindID>>;
+      { Value == Other } -> std::convertible_to<bool>;
+      { ValueT::parse(Text) } -> std::same_as<Expected<ValueT>>;
+      { ValueT::decode(Version, Payload) } -> std::same_as<Expected<ValueT>>;
+    };
+
+class TargetConstant final {
+public:
+  TargetConstant() = default;
+  TargetConstant(const TargetConstant &) = delete;
+  TargetConstant &operator=(const TargetConstant &) = delete;
+  TargetConstant(TargetConstant &&) noexcept;
+  TargetConstant &operator=(TargetConstant &&) noexcept;
+  ~TargetConstant();
+
+  template <TargetConstantValue ValueT>
+  [[nodiscard]] static Expected<TargetConstant> create(ValueT Value) {
+    if (ValueT::stableTypeID().value() == 0)
+      return makeUnexpected(ErrorCode::InvalidArgument, "target constant TypeID must be nonzero");
+    if (ValueT::schemaVersion() == 0) {
+      return makeUnexpected(ErrorCode::InvalidArgument,
+                            "target constant schema version must be nonzero");
+    }
+    auto Verification = Value.verify();
+    if (!Verification)
+      return std::unexpected(Verification.error());
+
+    std::unique_ptr<Concept> NewStorage = std::make_unique<Model<ValueT>>(std::move(Value));
+    return TargetConstant(std::move(NewStorage));
+  }
+
+  template <TargetConstantValue ValueT>
+  [[nodiscard]] static Expected<TargetConstant> parse(std::string_view Text) {
+    auto Value = ValueT::parse(Text);
+    if (!Value)
+      return std::unexpected(Value.error());
+    return create<ValueT>(std::move(*Value));
+  }
+
+  template <TargetConstantValue ValueT>
+  [[nodiscard]] static Expected<TargetConstant> decode(const EncodedTargetConstant &Encoded) {
+    if (Encoded.TypeID != ValueT::stableTypeID()) {
+      return makeUnexpected(ErrorCode::ParseError,
+                            "encoded target constant TypeID does not match its target schema");
+    }
+    if (Encoded.Version == 0)
+      return makeUnexpected(ErrorCode::ParseError, "target constant version must be nonzero");
+    auto Value = ValueT::decode(Encoded.Version, Encoded.Payload);
+    if (!Value)
+      return std::unexpected(Value.error());
+    return create<ValueT>(std::move(*Value));
+  }
+
+  [[nodiscard]] bool hasValue() const noexcept {
+    return Storage != nullptr;
+  }
+
+  [[nodiscard]] std::optional<TargetConstantTypeID> typeID() const noexcept;
+  [[nodiscard]] std::optional<std::uint32_t> schemaVersion() const noexcept;
+  [[nodiscard]] Expected<void> verify() const;
+  [[nodiscard]] Expected<TargetConstant> clone() const;
+  [[nodiscard]] Expected<std::uint64_t> stableHash() const;
+  [[nodiscard]] Expected<std::string> print() const;
+  [[nodiscard]] Expected<EncodedTargetConstant> encode() const;
+  [[nodiscard]] Expected<TargetConstantEmission> emit() const;
+  [[nodiscard]] Expected<Alignment> requiredAlignment() const;
+  [[nodiscard]] Expected<std::optional<TargetRelocationKindID>> relocationKind() const;
+
+  [[nodiscard]] bool equals(const TargetConstant &Other) const noexcept;
+
+  template <TargetConstantValue ValueT> [[nodiscard]] ValueT *getIf() noexcept {
+    if (!hasType<ValueT>())
+      return nullptr;
+    return &static_cast<Model<ValueT> *>(Storage.get())->value();
+  }
+
+  template <TargetConstantValue ValueT> [[nodiscard]] const ValueT *getIf() const noexcept {
+    if (!hasType<ValueT>())
+      return nullptr;
+    return &static_cast<const Model<ValueT> *>(Storage.get())->value();
+  }
+
+private:
+  class Concept {
+  public:
+    Concept() = default;
+    Concept(const Concept &) = delete;
+    Concept &operator=(const Concept &) = delete;
+    Concept(Concept &&) = delete;
+    Concept &operator=(Concept &&) = delete;
+    virtual ~Concept() = default;
+
+    [[nodiscard]] virtual TargetConstantTypeID typeID() const noexcept = 0;
+    [[nodiscard]] virtual std::uint32_t schemaVersion() const noexcept = 0;
+    [[nodiscard]] virtual const void *localTypeToken() const noexcept = 0;
+    [[nodiscard]] virtual Expected<void> verify() const = 0;
+    [[nodiscard]] virtual Expected<std::unique_ptr<Concept>> cloneStorage() const = 0;
+    [[nodiscard]] virtual std::uint64_t stableHash() const noexcept = 0;
+    [[nodiscard]] virtual std::string print() const = 0;
+    [[nodiscard]] virtual Expected<std::vector<std::byte>> encodePayload() const = 0;
+    [[nodiscard]] virtual Expected<TargetConstantEmission> emit() const = 0;
+    [[nodiscard]] virtual Alignment requiredAlignment() const noexcept = 0;
+    [[nodiscard]] virtual std::optional<TargetRelocationKindID> relocationKind() const noexcept = 0;
+    [[nodiscard]] virtual bool equals(const Concept &Other) const noexcept = 0;
+  };
+
+  template <typename ValueT> [[nodiscard]] static const void *typeToken() noexcept {
+    static const std::byte Token{};
+    return &Token;
+  }
+
+  template <TargetConstantValue ValueT> class Model final : public Concept {
+  public:
+    explicit Model(ValueT Value) : Value(std::move(Value)) {}
+
+    [[nodiscard]] TargetConstantTypeID typeID() const noexcept override {
+      return ValueT::stableTypeID();
+    }
+
+    [[nodiscard]] std::uint32_t schemaVersion() const noexcept override {
+      return ValueT::schemaVersion();
+    }
+
+    [[nodiscard]] const void *localTypeToken() const noexcept override {
+      return TargetConstant::typeToken<ValueT>();
+    }
+
+    [[nodiscard]] Expected<void> verify() const override {
+      return Value.verify();
+    }
+
+    [[nodiscard]] Expected<std::unique_ptr<Concept>> cloneStorage() const override {
+      auto Cloned = Value.clone();
+      if (!Cloned)
+        return std::unexpected(Cloned.error());
+      std::unique_ptr<Concept> Result = std::make_unique<Model<ValueT>>(std::move(*Cloned));
+      return Result;
+    }
+
+    [[nodiscard]] std::uint64_t stableHash() const noexcept override {
+      return Value.stableHash();
+    }
+
+    [[nodiscard]] std::string print() const override {
+      return Value.print();
+    }
+
+    [[nodiscard]] Expected<std::vector<std::byte>> encodePayload() const override {
+      return Value.encode();
+    }
+
+    [[nodiscard]] Expected<TargetConstantEmission> emit() const override {
+      return Value.emit();
+    }
+
+    [[nodiscard]] Alignment requiredAlignment() const noexcept override {
+      return Value.requiredAlignment();
+    }
+
+    [[nodiscard]] std::optional<TargetRelocationKindID> relocationKind() const noexcept override {
+      return Value.relocationKind();
+    }
+
+    [[nodiscard]] bool equals(const Concept &Other) const noexcept override {
+      if (Other.localTypeToken() != TargetConstant::typeToken<ValueT>())
+        return false;
+      return Value == static_cast<const Model<ValueT> &>(Other).Value;
+    }
+
+    [[nodiscard]] ValueT &value() noexcept {
+      return Value;
+    }
+
+    [[nodiscard]] const ValueT &value() const noexcept {
+      return Value;
+    }
+
+  private:
+    ValueT Value;
+  };
+
+  explicit TargetConstant(std::unique_ptr<Concept> Storage) : Storage(std::move(Storage)) {}
+
+  template <TargetConstantValue ValueT> [[nodiscard]] bool hasType() const noexcept {
+    return Storage != nullptr && Storage->typeID() == ValueT::stableTypeID() &&
+           Storage->localTypeToken() == typeToken<ValueT>();
+  }
+
+  std::unique_ptr<Concept> Storage;
+};
+
+} // namespace rcc
+
+#endif // RCC_CODEGEN_TARGETCONSTANT_H