// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#ifndef CARBON_TOOLCHAIN_SEM_IR_INST_H_
#define CARBON_TOOLCHAIN_SEM_IR_INST_H_

#include <concepts>
#include <cstdint>

#include "common/check.h"
#include "common/hashing.h"
#include "common/ostream.h"
#include "common/raw_string_ostream.h"
#include "common/struct_reflection.h"
#include "toolchain/base/block_value_store.h"
#include "toolchain/base/index_base.h"
#include "toolchain/base/int.h"
#include "toolchain/base/value_store.h"
#include "toolchain/sem_ir/id_kind.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/inst_kind.h"
#include "toolchain/sem_ir/singleton_insts.h"
#include "toolchain/sem_ir/typed_insts.h"

namespace Carbon::SemIR {

template <typename... TypedInsts>
struct CategoryOf;

// InstLikeTypeInfo is an implementation detail, and not public API.
namespace Internal {

// Information about an instruction-like type, which is a type that an Inst can
// be converted to and from.
template <typename InstLikeType>
struct InstLikeTypeInfo;

// A helper base class for instruction-like types that are structs.
template <typename InstLikeType>
struct InstLikeTypeInfoBase {
  // A corresponding std::tuple<...> type.
  using Tuple =
      decltype(StructReflection::AsTuple(std::declval<InstLikeType>()));

  static constexpr int FirstArgField =
      HasKindMemberAsField<InstLikeType> + HasTypeIdMember<InstLikeType>;

  static constexpr int NumArgs = std::tuple_size_v<Tuple> - FirstArgField;
  static_assert(NumArgs <= 2,
                "Unsupported: typed inst has more than two data fields");

  template <int N>
  using ArgType = std::tuple_element_t<FirstArgField + N, Tuple>;

  template <int N>
  static auto Get(InstLikeType inst) -> ArgType<N> {
    return std::get<FirstArgField + N>(StructReflection::AsTuple(inst));
  }
};

// A particular type of instruction is instruction-like.
template <typename TypedInst>
  requires std::same_as<const InstKind::Definition<
                            typename decltype(TypedInst::Kind)::TypedNodeId>,
                        decltype(TypedInst::Kind)>
struct InstLikeTypeInfo<TypedInst> : InstLikeTypeInfoBase<TypedInst> {
  static_assert(!HasKindMemberAsField<TypedInst>,
                "Instruction type should not have a kind field");
  static auto GetKind(TypedInst /*inst*/) -> InstKind {
    return TypedInst::Kind;
  }
  static constexpr auto IsKind(InstKind kind) -> bool {
    return kind == TypedInst::Kind;
  }
  // A name that can be streamed to an llvm::raw_ostream.
  static auto DebugName() -> InstKind { return TypedInst::Kind; }
};

// If `TypedInst` has an Nth field, validates that `CategoryInst` has a
// corresponding field with a compatible type.
template <typename CategoryInst, typename TypedInst, size_t N>
static consteval auto ValidateCategoryFieldForTypedInst() -> void {
  if constexpr (InstLikeTypeInfoBase<TypedInst>::NumArgs > N) {
    if constexpr (!std::is_same_v<typename InstLikeTypeInfoBase<
                                      CategoryInst>::template ArgType<N>,
                                  AnyRawId>) {
      static_assert(
          std::is_same_v<
              typename InstLikeTypeInfoBase<CategoryInst>::template ArgType<N>,
              typename InstLikeTypeInfoBase<TypedInst>::template ArgType<N>>,
          "Inst category field should be the same type as the "
          "corresponding fields of its typed insts, or AnyRawId if "
          "they have different types");
    }
  }
}

// Validates that `CategoryInst` is compatible with `TypedInst`
template <typename CategoryInst, typename TypedInst>
static consteval auto ValidateCategoryForTypedInst() -> void {
  static_assert(Internal::HasKindMemberAsField<CategoryInst>,
                "Inst category should have an `InstKind` field");
  static_assert(!HasTypeIdMember<TypedInst> || HasTypeIdMember<CategoryInst>,
                "Inst category should have a `TypeId` field if any of its "
                "typed insts do");

  static_assert(InstLikeTypeInfoBase<CategoryInst>::NumArgs >=
                    InstLikeTypeInfoBase<TypedInst>::NumArgs,
                "Inst category should have as many fields as any of its typed "
                "insts");

  ValidateCategoryFieldForTypedInst<CategoryInst, TypedInst, 0>();
  ValidateCategoryFieldForTypedInst<CategoryInst, TypedInst, 1>();
}

// Validates that `CategoryInst` is compatible with all of `TypedInsts`.
// Always returns true; validation failure will cause build errors when
// instantiating the function.
template <typename CategoryInst, typename... TypedInsts>
static consteval auto ValidateCategory(
    CategoryOf<TypedInsts...> /*category_info*/) -> bool {
  (ValidateCategoryForTypedInst<CategoryInst, TypedInsts>(), ...);
  return true;
}

// An instruction category is instruction-like.
template <typename InstCat>
  requires requires { typename InstCat::CategoryInfo; }
struct InstLikeTypeInfo<InstCat> : InstLikeTypeInfoBase<InstCat> {
  static auto GetKind(InstCat cat) -> InstKind { return cat.kind; }
  static constexpr auto IsKind(InstKind kind) -> bool {
    for (InstKind k : InstCat::CategoryInfo::Kinds) {
      if (k == kind) {
        return true;
      }
    }
    return false;
  }
  // A name that can be streamed to an llvm::raw_ostream.
  static auto DebugName() -> std::string {
    RawStringOstream out;
    out << "{";
    llvm::ListSeparator sep;
    for (auto kind : InstCat::CategoryInfo::Kinds) {
      out << sep << kind;
    }
    out << "}";
    return out.TakeStr();
  }

 private:
  // Trigger validation of `InstCat`.
  static_assert(ValidateCategory<InstCat>(typename InstCat::CategoryInfo()));
};

// HasInstCategory is true if T::Kind is an element of InstCat::Kinds.
template <typename InstCat, typename T>
concept HasInstCategory = InstLikeTypeInfo<InstCat>::IsKind(T::Kind);

// A type is InstLike if InstLikeTypeInfo is defined for it.
template <typename T>
concept InstLikeType = requires { sizeof(InstLikeTypeInfo<T>); };

}  // namespace Internal

// A type-erased representation of a SemIR instruction, that may be constructed
// from the specific kinds of instruction defined in `typed_insts.h`. This
// provides access to common fields present on most or all kinds of
// instructions:
//
// - `kind` for run-time logic when the input Kind is unknown.
// - `type_id` for quick type checking.
//
// In addition, kind-specific data can be accessed by casting to the specific
// kind of instruction:
//
// - Use `inst.kind()` or `Is<InstLikeType>` to determine what kind of
//   instruction it is.
// - Cast to a specific type using `inst.As<InstLikeType>()`
//   - Using the wrong kind in `inst.As<InstLikeType>()` is a programming error,
//     and will CHECK-fail in debug modes (opt may too, but it's not an API
//     guarantee).
// - Use `inst.TryAs<InstLikeType>()` to safely access type-specific instruction
//   data where the instruction's kind is not known.
class Inst : public Printable<Inst> {
 public:
  // Associates an argument (arg0 or arg1) with its IdKind.
  class ArgAndKind {
   public:
    explicit ArgAndKind(IdKind kind, int32_t value)
        : kind_(kind), value_(value) {}

    // Converts to `IdT`, validating the `kind` matches.
    template <typename IdT>
    auto As() const -> IdT {
      CARBON_DCHECK(kind_ == IdKind::For<IdT>);
      return IdT(value_);
    }

    // Converts to `IdT`, returning nullopt if the kind is incorrect.
    template <typename IdT>
    auto TryAs() const -> std::optional<IdT> {
      if (kind_ != IdKind::For<IdT>) {
        return std::nullopt;
      }
      return IdT(value_);
    }

    auto kind() const -> IdKind { return kind_; }
    auto value() const -> int32_t { return value_; }

   private:
    IdKind kind_;
    int32_t value_;
  };

  // Makes an instruction for a singleton. This exists to support simple
  // construction of all singletons by File.
  static auto MakeSingleton(InstKind kind) -> Inst {
    CARBON_CHECK(IsSingletonInstKind(kind));
    // Error uses a self-referential type so that it's not accidentally treated
    // as a normal type. Every other builtin is a type, including the
    // self-referential TypeType.
    auto type_id =
        kind == InstKind::ErrorInst ? ErrorInst::TypeId : TypeType::TypeId;
    return Inst(kind, type_id, InstId::NoneIndex, InstId::NoneIndex);
  }

  template <typename TypedInst>
    requires Internal::InstLikeType<TypedInst>
  explicit(false) Inst(TypedInst typed_inst)
      // kind_ is always overwritten below.
      : kind_(),
        type_id_(TypeId::None),
        arg0_(InstId::NoneIndex),
        arg1_(InstId::NoneIndex) {
    if constexpr (Internal::HasKindMemberAsField<TypedInst>) {
      kind_ = typed_inst.kind.AsInt();
    } else {
      kind_ = TypedInst::Kind.AsInt();
    }
    if constexpr (Internal::HasTypeIdMember<TypedInst>) {
      type_id_ = typed_inst.type_id;
    }
    using Info = Internal::InstLikeTypeInfo<TypedInst>;
    if constexpr (Info::NumArgs > 0) {
      arg0_ = ToRaw(Info::template Get<0>(typed_inst));
    }
    if constexpr (Info::NumArgs > 1) {
      arg1_ = ToRaw(Info::template Get<1>(typed_inst));
    }
  }

  // Returns whether this instruction has the specified type.
  template <typename TypedInst>
    requires Internal::InstLikeType<TypedInst>
  auto Is() const -> bool {
    return Internal::InstLikeTypeInfo<TypedInst>::IsKind(kind());
  }

  // Casts this instruction to the given typed instruction, which must match the
  // instruction's kind, and returns the typed instruction.
  template <typename TypedInst>
    requires Internal::InstLikeType<TypedInst>
  auto As() const -> TypedInst {
    using Info = Internal::InstLikeTypeInfo<TypedInst>;
    CARBON_CHECK(Is<TypedInst>(), "Casting inst {0} to wrong kind {1}", *this,
                 Info::DebugName());
    auto build_with_type_id_onwards = [&](auto... type_id_onwards) {
      if constexpr (Internal::HasKindMemberAsField<TypedInst>) {
        return TypedInst{kind(), type_id_onwards...};
      } else {
        return TypedInst{type_id_onwards...};
      }
    };

    auto build_with_args = [&](auto... args) {
      if constexpr (Internal::HasTypeIdMember<TypedInst>) {
        return build_with_type_id_onwards(type_id(), args...);
      } else {
        return build_with_type_id_onwards(args...);
      }
    };

    if constexpr (Info::NumArgs == 0) {
      return build_with_args();
    } else if constexpr (Info::NumArgs == 1) {
      return build_with_args(
          FromRaw<typename Info::template ArgType<0>>(arg0_));
    } else if constexpr (Info::NumArgs == 2) {
      return build_with_args(
          FromRaw<typename Info::template ArgType<0>>(arg0_),
          FromRaw<typename Info::template ArgType<1>>(arg1_));
    }
  }

  // If this instruction is the given kind, returns a typed instruction,
  // otherwise returns nullopt.
  template <typename TypedInst>
    requires Internal::InstLikeType<TypedInst>
  auto TryAs() const -> std::optional<TypedInst> {
    if (Is<TypedInst>()) {
      return As<TypedInst>();
    } else {
      return std::nullopt;
    }
  }

  auto kind() const -> InstKind { return InstKind::FromInt(kind_); }

  // Gets the type of the value produced by evaluating this instruction.
  auto type_id() const -> TypeId { return type_id_; }

  // Gets the first argument of the instruction. NoneIndex if there is no such
  // argument.
  auto arg0() const -> int32_t { return arg0_; }

  // Gets the second argument of the instruction. NoneIndex if there is no such
  // argument.
  auto arg1() const -> int32_t { return arg1_; }

  // Returns arguments with their IdKind.
  auto arg0_and_kind() const -> ArgAndKind {
    return ArgAndKind(ArgKindTable[kind_].first, arg0_);
  }
  auto arg1_and_kind() const -> ArgAndKind {
    return ArgAndKind(ArgKindTable[kind_].second, arg1_);
  }

  // Sets the type of this instruction.
  auto SetType(TypeId type_id) -> void { type_id_ = type_id; }

  // Sets the arguments of this instruction.
  auto SetArgs(int32_t arg0, int32_t arg1) -> void {
    arg0_ = arg0;
    arg1_ = arg1;
  }

  // Convert a field to its raw representation, used as `arg0_` / `arg1_`.
  static constexpr auto ToRaw(AnyIdBase base) -> int32_t { return base.index; }
  static constexpr auto ToRaw(IntId id) -> int32_t { return id.AsRaw(); }

  // Convert a field from its raw representation.
  template <typename T>
    requires IdKind::Contains<T>
  static constexpr auto FromRaw(int32_t raw) -> T {
    return T(raw);
  }
  template <>
  constexpr auto FromRaw<IntId>(int32_t raw) -> IntId {
    return IntId::MakeRaw(raw);
  }

  auto Print(llvm::raw_ostream& out) const -> void;

  friend auto operator==(Inst lhs, Inst rhs) -> bool {
    return std::memcmp(&lhs, &rhs, sizeof(Inst)) == 0;
  }

 private:
  friend class InstTestHelper;

  // Table mapping instruction kinds to their argument kinds.
  //
  // TODO: ArgKindTable would ideally live on InstKind, but can't be there for
  // layering reasons.
  static const std::pair<IdKind, IdKind> ArgKindTable[];

  // Raw constructor, used for testing.
  explicit Inst(InstKind kind, TypeId type_id, int32_t arg0, int32_t arg1)
      : Inst(kind.AsInt(), type_id, arg0, arg1) {}
  explicit constexpr Inst(int32_t kind, TypeId type_id, int32_t arg0,
                          int32_t arg1)
      : kind_(kind), type_id_(type_id), arg0_(arg0), arg1_(arg1) {}

  int32_t kind_;
  TypeId type_id_;

  // Use `As` to access arg0 and arg1.
  int32_t arg0_;
  int32_t arg1_;
};

// TODO: This is currently 16 bytes because we sometimes have 2 arguments for a
// pair of Insts. However, InstKind is 1 byte; if args were 3.5 bytes, we could
// potentially shrink Inst by 4 bytes. This may be worth investigating further.
// Note though that 16 bytes is an ideal size for registers, we may want more
// flags, and 12 bytes would be a more marginal improvement.
static_assert(sizeof(Inst) == 16, "Unexpected Inst size");

// Instruction-like types can be printed by converting them to instructions.
template <typename TypedInst>
  requires Internal::InstLikeType<TypedInst>
inline auto operator<<(llvm::raw_ostream& out, TypedInst inst)
    -> llvm::raw_ostream& {
  Inst(inst).Print(out);
  return out;
}

// Associates a LocId and Inst in order to provide type-checking that the
// TypedNodeId corresponds to the InstT.
struct LocIdAndInst {
  // Constructs a LocIdAndInst with no associated location. This should be used
  // very sparingly: only when it doesn't make sense to store a location even
  // when the instruction kind usually has one, such as for instructions in the
  // constants block.
  template <typename InstT>
  static auto NoLoc(InstT inst) -> LocIdAndInst {
    return LocIdAndInst(LocId::None, inst, /*is_unchecked=*/true);
  }

  // Unsafely form a pair of a location and an instruction. Used in the cases
  // where we can't statically enforce the type matches.
  static auto UncheckedLoc(LocId loc_id, Inst inst) -> LocIdAndInst {
    return LocIdAndInst(loc_id, inst, /*is_unchecked=*/true);
  }

  // Construction for the common case with a typed node.
  template <typename InstT>
    requires(Internal::HasNodeId<InstT>)
  LocIdAndInst(decltype(InstT::Kind)::TypedNodeId node_id, InstT inst)
      : loc_id(node_id), inst(inst) {}

  // Construction for the case where the instruction can have any associated
  // node.
  template <typename InstT>
    requires(Internal::HasUntypedNodeId<InstT>)
  LocIdAndInst(LocId loc_id, InstT inst) : loc_id(loc_id), inst(inst) {}

  LocId loc_id;
  Inst inst;

 private:
  // Note `is_unchecked` serves to disambiguate from public constructors.
  explicit LocIdAndInst(LocId loc_id, Inst inst, bool /*is_unchecked*/)
      : loc_id(loc_id), inst(inst) {}
};

// Provides a ValueStore wrapper for an API specific to instructions.
class InstStore {
 public:
  using IdType = InstId;

  explicit InstStore(File* file) : file_(file) {}

  // Adds an instruction to the instruction list, returning an ID to reference
  // the instruction. Note that this doesn't add the instruction to any
  // instruction block. Check::Context::AddInst or InstBlockStack::AddInst
  // should usually be used instead, to add the instruction to the current
  // block.
  auto AddInNoBlock(LocIdAndInst loc_id_and_inst) -> InstId {
    loc_ids_.push_back(loc_id_and_inst.loc_id);
    return values_.Add(loc_id_and_inst.inst);
  }

  // Returns the requested instruction. The returned instruction always has an
  // unattached type, even if an attached type is stored for it.
  auto Get(InstId inst_id) const -> Inst {
    Inst result = values_.Get(inst_id);
    auto type_id = result.type_id();
    if (type_id.has_value() && type_id.is_symbolic()) {
      result.SetType(GetUnattachedType(type_id));
    }
    return result;
  }

  // Returns the requested instruction, which is known to have the specified
  // type.
  template <typename InstT>
  auto Get(KnownInstId<InstT> inst_id) const -> InstT {
    return Get(static_cast<InstId>(inst_id)).As<InstT>();
  }

  // Returns the requested instruction, preserving its attached type.
  auto GetWithAttachedType(InstId inst_id) const -> Inst {
    return values_.Get(inst_id);
  }

  // Returns the type of the instruction as an attached type.
  auto GetAttachedType(InstId inst_id) const -> TypeId {
    return GetWithAttachedType(inst_id).type_id();
  }

  // Returns the requested instruction and its location ID.
  auto GetWithLocId(InstId inst_id) const -> LocIdAndInst {
    return LocIdAndInst::UncheckedLoc(LocId(inst_id), Get(inst_id));
  }

  // Returns whether the requested instruction is the specified type.
  template <typename InstT>
  auto Is(InstId inst_id) const -> bool {
    return Get(inst_id).Is<InstT>();
  }

  // Returns the requested instruction, which is known to have the specified
  // type.
  template <typename InstT>
  auto GetAs(InstId inst_id) const -> InstT {
    return Get(inst_id).As<InstT>();
  }

  // Returns the requested instruction as the specified type, if it is of that
  // type.
  template <typename InstT>
  auto TryGetAs(InstId inst_id) const -> std::optional<InstT> {
    return Get(inst_id).TryAs<InstT>();
  }

  // Use `Get()` when the instruction type is known.
  template <typename InstT, typename KnownInstT>
  auto TryGetAs(KnownInstId<KnownInstT> inst_id) const = delete;

  // Returns the requested instruction as the specified type, if it is valid and
  // of that type. Otherwise returns nullopt.
  template <typename InstT>
  auto TryGetAsIfValid(InstId inst_id) const -> std::optional<InstT> {
    if (!inst_id.has_value()) {
      return std::nullopt;
    }
    return TryGetAs<InstT>(inst_id);
  }

  template <typename InstT>
  struct GetAsWithIdResult {
    KnownInstId<InstT> inst_id;
    InstT inst;
  };

  // Returns the requested instruction, which is known to have the specified
  // type, along with the original `InstId`, encoding the work of checking its
  // type in a `KnownInstId`.
  template <typename InstT>
  auto GetAsWithId(InstId inst_id) const -> GetAsWithIdResult<InstT> {
    auto inst = GetAs<InstT>(inst_id);
    return {.inst_id = KnownInstId<InstT>::UnsafeMake(inst_id), .inst = inst};
  }

  // Returns the requested instruction, if it is of that type, along with the
  // original `InstId`, encoding the work of checking its type in a
  // `KnownInstId`.
  template <typename InstT>
  auto TryGetAsWithId(InstId inst_id) const
      -> std::optional<GetAsWithIdResult<InstT>> {
    auto inst = TryGetAs<InstT>(inst_id);
    if (!inst) {
      return std::nullopt;
    }
    return {
        {.inst_id = KnownInstId<InstT>::UnsafeMake(inst_id), .inst = *inst}};
  }

  // Attempts to convert the given instruction to the type that contains
  // `member`. If it can be converted, the instruction ID and instruction are
  // replaced by the unwrapped value of that member, and the converted wrapper
  // instruction and its ID are returned. Otherwise returns {nullopt, None}.
  template <typename InstT, typename InstIdT>
    requires std::derived_from<InstIdT, InstId>
  auto TryUnwrap(Inst& inst, InstId& inst_id, InstIdT InstT::* member) const
      -> std::pair<std::optional<InstT>, KnownInstId<InstT>> {
    if (auto wrapped_inst = inst.TryAs<InstT>()) {
      auto wrapped_inst_id = KnownInstId<InstT>::UnsafeMake(inst_id);
      inst_id = (*wrapped_inst).*member;
      inst = Get(inst_id);
      return {wrapped_inst, wrapped_inst_id};
    }
    return {std::nullopt, KnownInstId<InstT>::None};
  }

  // Returns a resolved LocId, which will point to a parse node, an import, or
  // be None.
  //
  // Unresolved LocIds can be backed by an InstId which may or may not have a
  // value after being resolved, so this operation needs to be done before using
  // most operations on LocId.
  auto GetCanonicalLocId(LocId loc_id) const -> LocId {
    while (loc_id.kind() == LocId::Kind::InstId) {
      loc_id = GetNonCanonicalLocId(loc_id.inst_id());
    }
    return loc_id;
  }

  // Gets the resolved LocId for an instruction. InstId can directly construct
  // an unresolved LocId. This skips that step when a resolved LocId is needed.
  auto GetCanonicalLocId(InstId inst_id) const -> LocId {
    return GetCanonicalLocId(GetNonCanonicalLocId(inst_id));
  }

  // Returns a virtual location to use for the desugaring of the code at the
  // specified location.
  auto GetLocIdForDesugaring(LocId loc_id) const -> LocId {
    return GetCanonicalLocId(loc_id).AsDesugared();
  }
  auto GetLocIdForDesugaring(InstId inst_id) const -> LocId {
    return GetCanonicalLocId(inst_id).AsDesugared();
  }

  // Returns the instruction that this instruction was imported from, or
  // ImportIRInstId::None if this instruction was not generated by importing
  // another instruction.
  auto GetImportSource(InstId inst_id) const -> ImportIRInstId {
    auto loc_id = GetNonCanonicalLocId(inst_id);
    return loc_id.kind() == LocId::Kind::ImportIRInstId
               ? loc_id.import_ir_inst_id()
               : ImportIRInstId::None;
  }

  // Overwrites a given instruction with a new value.
  auto Set(InstId inst_id, Inst inst) -> void { values_.Get(inst_id) = inst; }

  // Overwrites a given instruction's location with a new value.
  auto SetLocId(InstId inst_id, LocId loc_id) -> void {
    loc_ids_[inst_id.index] = loc_id;
  }

  // Overwrites a given instruction and location ID with a new value.
  auto SetLocIdAndInst(InstId inst_id, LocIdAndInst loc_id_and_inst) -> void {
    Set(inst_id, loc_id_and_inst.inst);
    SetLocId(inst_id, loc_id_and_inst.loc_id);
  }

  // Reserves space.
  auto Reserve(size_t size) -> void {
    loc_ids_.reserve(size);
    values_.Reserve(size);
  }

  // Collects memory usage of members.
  auto CollectMemUsage(MemUsage& mem_usage, llvm::StringRef label) const
      -> void {
    mem_usage.Collect(MemUsage::ConcatLabel(label, "loc_ids_"), loc_ids_);
    mem_usage.Collect(MemUsage::ConcatLabel(label, "values_"), values_);
  }

  auto values() const [[clang::lifetimebound]]
  -> ValueStore<InstId, Inst>::Range {
    return values_.values();
  }
  auto size() const -> int { return values_.size(); }
  auto enumerate() const [[clang::lifetimebound]] -> auto {
    return values_.enumerate();
  }

 private:
  // Given a symbolic type, get the corresponding unattached type.
  auto GetUnattachedType(TypeId type_id) const -> TypeId;

  // Gets the specified location for an instruction, without performing any
  // canonicalization.
  auto GetNonCanonicalLocId(InstId inst_id) const -> LocId {
    CARBON_CHECK(static_cast<size_t>(inst_id.index) < loc_ids_.size(),
                 "{0} {1}", inst_id.index, loc_ids_.size());
    return loc_ids_[inst_id.index];
  }

  File* file_;
  llvm::SmallVector<LocId> loc_ids_;
  ValueStore<InstId, Inst> values_;
};

// Adapts BlockValueStore for instruction blocks.
class InstBlockStore : public BlockValueStore<InstBlockId, InstId> {
 public:
  using BaseType = BlockValueStore<InstBlockId, InstId>;

  explicit InstBlockStore(llvm::BumpPtrAllocator& allocator)
      : BaseType(allocator) {
    auto exports_id = AddPlaceholder();
    CARBON_CHECK(exports_id == InstBlockId::Exports);
    auto imports_id = AddPlaceholder();
    CARBON_CHECK(imports_id == InstBlockId::Imports);
    auto global_init_id = AddPlaceholder();
    CARBON_CHECK(global_init_id == InstBlockId::GlobalInit);
  }

  // Adds an uninitialized block of the given size. The caller is expected to
  // modify values.
  auto AddUninitialized(size_t size) -> InstBlockId {
    return values().Add(AllocateUninitialized(size));
  }

  // Reserves and returns a block ID. The contents of the block should be
  // specified by calling ReplacePlaceholder.
  auto AddPlaceholder() -> InstBlockId {
    return values().Add(llvm::MutableArrayRef<InstId>());
  }

  // Sets the contents of a placeholder block to the given content.
  auto ReplacePlaceholder(InstBlockId block_id, llvm::ArrayRef<InstId> content)
      -> void {
    CARBON_CHECK(block_id != InstBlockId::Empty);
    CARBON_CHECK(Get(block_id).empty(),
                 "inst block content set more than once");
    values().Get(block_id) = AllocateCopy(content);
  }

  // Returns the contents of the specified block, or an empty array if the block
  // is invalid.
  auto GetOrEmpty(InstBlockId block_id) const -> llvm::ArrayRef<InstId> {
    return block_id.has_value() ? Get(block_id) : llvm::ArrayRef<InstId>();
  }
};

// See common/hashing.h.
inline auto CarbonHashValue(const Inst& value, uint64_t seed) -> HashCode {
  Hasher hasher(seed);
  hasher.HashRaw(value);
  return static_cast<HashCode>(hasher);
}

}  // namespace Carbon::SemIR

#endif  // CARBON_TOOLCHAIN_SEM_IR_INST_H_
