// 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

#include "toolchain/sem_ir/builtin_function_kind.h"

#include <utility>

#include "toolchain/sem_ir/file.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/type_info.h"
#include "toolchain/sem_ir/typed_insts.h"

namespace Carbon::SemIR {

// A function that validates that a builtin was declared properly.
using ValidateFn = auto(const File& sem_ir, llvm::ArrayRef<InstId> call_params,
                        TypeId return_type) -> bool;

namespace {
// Information about a builtin function.
struct BuiltinInfo {
  llvm::StringLiteral name;
  ValidateFn* validate;
};

// The maximum number of type parameters any builtin needs.
constexpr int MaxTypeParams = 2;

// State used when validating a builtin signature that persists between
// individual checks.
struct ValidateState {
  // The type values of type parameters in the builtin signature. Invalid if
  // either no value has been deduced yet or the parameter is not used.
  TypeId type_params[MaxTypeParams] = {TypeId::None, TypeId::None};
};

// A constraint that applies to types.
template <typename T>
concept TypeConstraint =
    requires(const File& sem_ir, ValidateState& state, TypeId type_id) {
      { T::CheckType(sem_ir, state, type_id) } -> std::convertible_to<bool>;
    };

// A constraint that applies to parameters.
template <typename T>
concept ParamConstraint =
    requires(const File& sem_ir, ValidateState& state, InstId param_id) {
      { T::CheckParam(sem_ir, state, param_id) } -> std::convertible_to<bool>;
    };

// Constraint that a type is generic type parameter `I` of the builtin,
// satisfying `Constraint`. See ValidateSignature for details.
template <int I, typename Constraint>
  requires TypeConstraint<Constraint>
struct TypeParam {
  static_assert(I >= 0 && I < MaxTypeParams);

  static auto CheckType(const File& sem_ir, ValidateState& state,
                        TypeId type_id) -> bool {
    if (state.type_params[I].has_value() && type_id != state.type_params[I]) {
      return false;
    }
    if (!Constraint::CheckType(sem_ir, state, type_id)) {
      return false;
    }
    state.type_params[I] = type_id;
    return true;
  }
};

// Constraint that a type is a specific builtin. See ValidateSignature for
// details.
template <const TypeInstId& BuiltinId>
struct BuiltinType {
  static auto CheckType(const File& sem_ir, ValidateState& /*state*/,
                        TypeId type_id) -> bool {
    return sem_ir.types().GetInstId(type_id) == BuiltinId;
  }
};

// Constraint that a type is a pointer to another type. See ValidateSignature
// for details.
template <typename PointeeT>
  requires TypeConstraint<PointeeT>
struct PointerTo {
  static auto CheckType(const File& sem_ir, ValidateState& state,
                        TypeId type_id) -> bool {
    if (!sem_ir.types().Is<PointerType>(type_id)) {
      return false;
    }
    return CheckType<PointeeT>(sem_ir, state, sem_ir.GetPointeeType(type_id));
  }
};

// Constraint that a type is MaybeUnformed<T>.
template <typename T>
  requires TypeConstraint<T>
struct MaybeUnformed {
  static auto CheckType(const File& sem_ir, ValidateState& state,
                        TypeId type_id) -> bool {
    auto maybe_unformed =
        sem_ir.types().TryGetAs<SemIR::MaybeUnformedType>(type_id);
    if (!maybe_unformed) {
      return false;
    }
    return CheckType<T>(
        sem_ir, state,
        sem_ir.types().GetTypeIdForTypeInstId(maybe_unformed->inner_id));
  }
};

// Constraint that a type is `()`, used as the return type of builtin functions
// with no return value.
struct NoReturn {
  static auto CheckType(const File& sem_ir, ValidateState& /*state*/,
                        TypeId type_id) -> bool {
    auto tuple = sem_ir.types().TryGetAs<TupleType>(type_id);
    if (!tuple) {
      return false;
    }
    return sem_ir.inst_blocks().Get(tuple->type_elements_id).empty();
  }
};

// Constraint that a type is `bool`.
using Bool = BuiltinType<BoolType::TypeInstId>;

// Constraint that a type is `Core.CharLiteral`.
using CharLiteral = BuiltinType<CharLiteralType::TypeInstId>;

// Constraint that a type is `u8` or an adapted type, including `Core.Char`.
struct CharCompatible {
  static auto CheckType(const File& sem_ir, ValidateState& /*state*/,
                        TypeId type_id) -> bool {
    auto int_info = sem_ir.types().TryGetIntTypeInfo(type_id);
    if (!int_info) {
      // Not an integer.
      return false;
    }
    if (!int_info->bit_width.has_value() || int_info->is_signed) {
      // Must be unsigned.
      return false;
    }
    return sem_ir.ints().Get(int_info->bit_width) == 8;
  }
};

// Constraint that requires the type to be a sized integer type.
struct AnySizedInt {
  static auto CheckType(const File& sem_ir, ValidateState& /*state*/,
                        TypeId type_id) -> bool {
    return sem_ir.types().Is<IntType>(type_id);
  }
};

// Constraint that requires the type to be an integer type: either a sized
// integer type or a literal.
struct AnyInt {
  static auto CheckType(const File& sem_ir, ValidateState& state,
                        TypeId type_id) -> bool {
    return AnySizedInt::CheckType(sem_ir, state, type_id) ||
           BuiltinType<IntLiteralType::TypeInstId>::CheckType(sem_ir, state,
                                                              type_id);
  }
};

// Constraint that requires the type to be a sized floating-point type.
struct AnySizedFloat {
  static auto CheckType(const File& sem_ir, ValidateState& /*state*/,
                        TypeId type_id) -> bool {
    return sem_ir.types().Is<FloatType>(type_id);
  }
};

// Constraint that requires the type to be a float type: either a sized float
// type or a literal.
struct AnyFloat {
  static auto CheckType(const File& sem_ir, ValidateState& state,
                        TypeId type_id) -> bool {
    return AnySizedFloat::CheckType(sem_ir, state, type_id) ||
           BuiltinType<FloatLiteralType::TypeInstId>::CheckType(sem_ir, state,
                                                                type_id);
  }
};

// Constraint that allows an arbitrary type.
struct AnyType {
  static auto CheckType(const File& /*sem_ir*/, ValidateState& /*state*/,
                        TypeId /*type_id*/) -> bool {
    return true;
  }
};

// Constraint that requires the type to be the type type.
using Type = BuiltinType<TypeType::TypeInstId>;

// Constraint that a type supports a primitive copy. This happens if its
// initializing representation is a copy of its value representation.
struct PrimitiveCopyable {
  static auto CheckType(const File& sem_ir, ValidateState& /*state*/,
                        TypeId type_id) -> bool {
    return InitRepr::ForType(sem_ir, type_id).IsCopyOfObjectRepr() &&
           ValueRepr::ForType(sem_ir, type_id)
               .IsCopyOfObjectRepr(sem_ir, type_id);
  }
};

// Constraint that a parameter is passed by reference.
template <typename Constraint>
  requires TypeConstraint<Constraint>
struct ByRef {
  static auto CheckParam(const File& sem_ir, ValidateState& state,
                         InstId param_id) -> bool {
    if (auto ref_param = sem_ir.insts().TryGetAs<RefParam>(param_id)) {
      return CheckType<Constraint>(sem_ir, state, ref_param->type_id);
    }
    return false;
  }
};

// Checks that the specified type matches the given type constraint.
template <typename Constraint>
  requires TypeConstraint<Constraint>
auto CheckType(const File& sem_ir, ValidateState& state, TypeId type_id)
    -> bool {
  while (type_id.has_value()) {
    // Allow a type that satisfies the constraint.
    if (Constraint::CheckType(sem_ir, state, type_id)) {
      return true;
    }

    // Also allow a class type that adapts a matching type.
    type_id = sem_ir.types().GetAdaptedType(type_id);
  }
  return false;
}

// CheckParam<Constraint> checks that param_id (which must belong to
// the AnyParam category) matches the given parameter constraint. A type
// constraint is interpreted as a parameter constraint that requires param_id to
// be a ValueParam whose type matches the type constraint.
template <typename Constraint>
  requires ParamConstraint<Constraint>
auto CheckParam(const File& sem_ir, ValidateState& state, InstId param_id)
    -> bool {
  return Constraint::CheckParam(sem_ir, state, param_id);
}

template <typename Constraint>
  requires TypeConstraint<Constraint>
auto CheckParam(const File& sem_ir, ValidateState& state, InstId param_id)
    -> bool {
  if (auto param_pattern = sem_ir.insts().TryGetAs<ValueParam>(param_id)) {
    return CheckType<Constraint>(sem_ir, state, param_pattern->type_id);
  }
  return false;
}

}  // namespace

// Validates that this builtin has a signature matching the specified signature.
//
// `SignatureFnType` is a C++ function type that describes the signature that is
// expected for this builtin. For example, `auto (AnyInt, AnyInt) -> AnyInt`
// specifies that the builtin takes values of two integer types and returns a
// value of a third integer type. Types used within the signature should provide
// a `Check` function that validates that the Carbon type is expected:
//
//   auto CheckType(const File&, ValidateState&, TypeId) -> bool;
//
// To constrain that the same type is used in multiple places in the signature,
// `TypeParam<I, T>` can be used. For example:
//
//   auto (TypeParam<0, AnyInt>, AnyInt) -> TypeParam<0, AnyInt>
//
// describes a builtin that takes two integers, and whose return type matches
// its first parameter type. For convenience, typedefs for `TypeParam<I, T>`
// are used in the descriptions of the builtins.
template <typename SignatureFnType>
static auto ValidateSignature(const File& sem_ir,
                              llvm::ArrayRef<InstId> call_params,
                              TypeId return_type) -> bool {
  using SignatureTraits = llvm::function_traits<SignatureFnType*>;
  ValidateState state;

  // Must have expected number of arguments.
  if (call_params.size() != SignatureTraits::num_args) {
    return false;
  }

  // Argument types must match.
  if (![&]<size_t... Indexes>(std::index_sequence<Indexes...>) {
        return ((CheckParam<typename SignatureTraits::template arg_t<Indexes>>(
                    sem_ir, state, call_params[Indexes])) &&
                ...);
      }(std::make_index_sequence<SignatureTraits::num_args>())) {
    return false;
  }

  // Result type must match.
  if (!CheckType<typename SignatureTraits::result_t>(sem_ir, state,
                                                     return_type)) {
    return false;
  }

  return true;
}

// Validates the signature for NoOp. This ignores all arguments, only validating
// that the return type is compatible.
static auto ValidateNoOpSignature(const File& sem_ir,
                                  llvm::ArrayRef<InstId> /*call_params*/,
                                  TypeId return_type) -> bool {
  ValidateState state;
  return CheckType<NoReturn>(sem_ir, state, return_type);
}

// Descriptions of builtin functions follow. For each builtin, a corresponding
// `BuiltinInfo` constant is declared describing properties of that builtin.
namespace BuiltinFunctionInfo {

// Convenience name used in the builtin type signatures below for a first
// generic type parameter that is constrained to be an integer type.
using IntT = TypeParam<0, AnyInt>;

// Convenience name used in the builtin type signatures below for a second
// generic type parameter that is constrained to be an integer type.
using IntU = TypeParam<1, AnyInt>;

// Convenience name used in the builtin type signatures below for a first
// generic type parameter that is constrained to be a sized integer type.
using SizedIntT = TypeParam<0, AnySizedInt>;

// Convenience name used in the builtin type signatures below for a second
// generic type parameter that is constrained to be a sized integer type.
using SizedIntU = TypeParam<1, AnySizedInt>;

// Convenience name used in the builtin type signatures below for a first
// generic type parameter that is constrained to be an float type.
using FloatT = TypeParam<0, AnyFloat>;

// Convenience name used in the builtin type signatures below for a second
// generic type parameter that is constrained to be an float type.
using FloatU = TypeParam<1, AnyFloat>;

// Convenience name used in the builtin type signatures below for a first
// generic type parameter that is constrained to be a sized float type.
using SizedFloatT = TypeParam<0, AnySizedFloat>;

// Convenience name used in the builtin type signatures below for a first
// generic type parameter that supports primitive copy.
using PrimitiveCopyParamT = TypeParam<0, PrimitiveCopyable>;

// Not a builtin function.
constexpr BuiltinInfo None = {"", nullptr};

constexpr BuiltinInfo NoOp = {"no_op", ValidateNoOpSignature};

constexpr BuiltinInfo PrimitiveCopy = {
    "primitive_copy",
    ValidateSignature<auto(PrimitiveCopyParamT)->PrimitiveCopyParamT>};

// Prints a single character.
constexpr BuiltinInfo PrintChar = {
    "print.char", ValidateSignature<auto(AnySizedInt)->AnySizedInt>};

// Prints an integer.
constexpr BuiltinInfo PrintInt = {
    "print.int", ValidateSignature<auto(AnySizedInt)->NoReturn>};

// Reads a single character from stdin.
constexpr BuiltinInfo ReadChar = {"read.char",
                                  ValidateSignature<auto()->AnySizedInt>};

// Returns the `Core.CharLiteral` type.
constexpr BuiltinInfo CharLiteralMakeType = {"char_literal.make_type",
                                             ValidateSignature<auto()->Type>};

// Returns the `Core.IntLiteral` type.
constexpr BuiltinInfo IntLiteralMakeType = {"int_literal.make_type",
                                            ValidateSignature<auto()->Type>};

// Returns the `Core.FloatLiteral` type.
constexpr BuiltinInfo FloatLiteralMakeType = {"float_literal.make_type",
                                              ValidateSignature<auto()->Type>};

// Returns the `iN` type.
// TODO: Should we use a more specific type as the type of the bit width?
constexpr BuiltinInfo IntMakeTypeSigned = {
    "int.make_type_signed", ValidateSignature<auto(AnyInt)->Type>};

// Returns the `uN` type.
constexpr BuiltinInfo IntMakeTypeUnsigned = {
    "int.make_type_unsigned", ValidateSignature<auto(AnyInt)->Type>};

// Returns float types, such as `f64`. Currently only supports `f64`.
constexpr BuiltinInfo FloatMakeType = {"float.make_type",
                                       ValidateSignature<auto(AnyInt)->Type>};

// Returns the `bool` type.
constexpr BuiltinInfo BoolMakeType = {"bool.make_type",
                                      ValidateSignature<auto()->Type>};

// Returns the `MaybeUnformed(T)` type.
constexpr BuiltinInfo MaybeUnformedMakeType = {
    "maybe_unformed.make_type", ValidateSignature<auto(Type)->Type>};

// Converts between char types, with a diagnostic if the value doesn't fit.
constexpr BuiltinInfo CharConvertChecked = {
    "char.convert_checked",
    ValidateSignature<auto(CharLiteral)->CharCompatible>};

// Converts between integer types, truncating if necessary.
constexpr BuiltinInfo IntConvert = {"int.convert",
                                    ValidateSignature<auto(AnyInt)->AnyInt>};

// Converts between integer types, with a diagnostic if the value doesn't fit.
constexpr BuiltinInfo IntConvertChecked = {
    "int.convert_checked", ValidateSignature<auto(AnyInt)->AnyInt>};

// "int.snegate": integer negation.
constexpr BuiltinInfo IntSNegate = {"int.snegate",
                                    ValidateSignature<auto(IntT)->IntT>};

// "int.sadd": integer addition.
constexpr BuiltinInfo IntSAdd = {"int.sadd",
                                 ValidateSignature<auto(IntT, IntT)->IntT>};

// "int.ssub": integer subtraction.
constexpr BuiltinInfo IntSSub = {"int.ssub",
                                 ValidateSignature<auto(IntT, IntT)->IntT>};

// "int.smul": integer multiplication.
constexpr BuiltinInfo IntSMul = {"int.smul",
                                 ValidateSignature<auto(IntT, IntT)->IntT>};

// "int.sdiv": integer division.
constexpr BuiltinInfo IntSDiv = {"int.sdiv",
                                 ValidateSignature<auto(IntT, IntT)->IntT>};

// "int.smod": integer modulo.
constexpr BuiltinInfo IntSMod = {"int.smod",
                                 ValidateSignature<auto(IntT, IntT)->IntT>};

// "int.unegate": unsigned integer negation.
constexpr BuiltinInfo IntUNegate = {
    "int.unegate", ValidateSignature<auto(SizedIntT)->SizedIntT>};

// "int.uadd": unsigned integer addition.
constexpr BuiltinInfo IntUAdd = {
    "int.uadd", ValidateSignature<auto(SizedIntT, SizedIntT)->SizedIntT>};

// "int.usub": unsigned integer subtraction.
constexpr BuiltinInfo IntUSub = {
    "int.usub", ValidateSignature<auto(SizedIntT, SizedIntT)->SizedIntT>};

// "int.umul": unsigned integer multiplication.
constexpr BuiltinInfo IntUMul = {
    "int.umul", ValidateSignature<auto(SizedIntT, SizedIntT)->SizedIntT>};

// "int.udiv": unsigned integer division.
constexpr BuiltinInfo IntUDiv = {
    "int.udiv", ValidateSignature<auto(SizedIntT, SizedIntT)->SizedIntT>};

// "int.mod": integer modulo.
constexpr BuiltinInfo IntUMod = {
    "int.umod", ValidateSignature<auto(SizedIntT, SizedIntT)->SizedIntT>};

// "int.complement": integer bitwise complement.
constexpr BuiltinInfo IntComplement = {"int.complement",
                                       ValidateSignature<auto(IntT)->IntT>};

// "int.and": integer bitwise and.
constexpr BuiltinInfo IntAnd = {"int.and",
                                ValidateSignature<auto(IntT, IntT)->IntT>};

// "int.or": integer bitwise or.
constexpr BuiltinInfo IntOr = {"int.or",
                               ValidateSignature<auto(IntT, IntT)->IntT>};

// "int.xor": integer bitwise xor.
constexpr BuiltinInfo IntXor = {"int.xor",
                                ValidateSignature<auto(IntT, IntT)->IntT>};

// "int.left_shift": integer left shift.
constexpr BuiltinInfo IntLeftShift = {
    "int.left_shift", ValidateSignature<auto(IntT, IntU)->IntT>};

// "int.right_shift": integer right shift.
constexpr BuiltinInfo IntRightShift = {
    "int.right_shift", ValidateSignature<auto(IntT, IntU)->IntT>};

// "int.sadd_assign": integer in-place addition.
constexpr BuiltinInfo IntSAddAssign = {
    "int.sadd_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.ssub_assign": integer in-place subtraction.
constexpr BuiltinInfo IntSSubAssign = {
    "int.ssub_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.smul_assign": integer in-place multiplication.
constexpr BuiltinInfo IntSMulAssign = {
    "int.smul_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.sdiv_assign": integer in-place division.
constexpr BuiltinInfo IntSDivAssign = {
    "int.sdiv_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.smod_assign": integer in-place modulo.
constexpr BuiltinInfo IntSModAssign = {
    "int.smod_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.uadd_assign": unsigned integer in-place addition.
constexpr BuiltinInfo IntUAddAssign = {
    "int.uadd_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.usub_assign": unsigned integer in-place subtraction.
constexpr BuiltinInfo IntUSubAssign = {
    "int.usub_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.umul_assign": unsigned integer in-place multiplication.
constexpr BuiltinInfo IntUMulAssign = {
    "int.umul_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.udiv_assign": unsigned integer in-place division.
constexpr BuiltinInfo IntUDivAssign = {
    "int.udiv_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.mod_assign": integer in-place modulo.
constexpr BuiltinInfo IntUModAssign = {
    "int.umod_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.and_assign": integer in-place bitwise and.
constexpr BuiltinInfo IntAndAssign = {
    "int.and_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.or_assign": integer in-place bitwise or.
constexpr BuiltinInfo IntOrAssign = {
    "int.or_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.xor_assign": integer in-place bitwise xor.
constexpr BuiltinInfo IntXorAssign = {
    "int.xor_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntT)->NoReturn>};

// "int.left_shift_assign": integer in-place left shift.
constexpr BuiltinInfo IntLeftShiftAssign = {
    "int.left_shift_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntU)->NoReturn>};

// "int.right_shift_assign": integer in-place right shift.
constexpr BuiltinInfo IntRightShiftAssign = {
    "int.right_shift_assign",
    ValidateSignature<auto(ByRef<SizedIntT>, SizedIntU)->NoReturn>};

// "int.eq": integer equality comparison.
constexpr BuiltinInfo IntEq = {"int.eq",
                               ValidateSignature<auto(IntT, IntU)->Bool>};

// "int.neq": integer non-equality comparison.
constexpr BuiltinInfo IntNeq = {"int.neq",
                                ValidateSignature<auto(IntT, IntU)->Bool>};

// "int.less": integer less than comparison.
constexpr BuiltinInfo IntLess = {"int.less",
                                 ValidateSignature<auto(IntT, IntU)->Bool>};

// "int.less_eq": integer less than or equal comparison.
constexpr BuiltinInfo IntLessEq = {"int.less_eq",
                                   ValidateSignature<auto(IntT, IntU)->Bool>};

// "int.greater": integer greater than comparison.
constexpr BuiltinInfo IntGreater = {"int.greater",
                                    ValidateSignature<auto(IntT, IntU)->Bool>};

// "int.greater_eq": integer greater than or equal comparison.
constexpr BuiltinInfo IntGreaterEq = {
    "int.greater_eq", ValidateSignature<auto(IntT, IntU)->Bool>};

// "float.negate": float negation.
constexpr BuiltinInfo FloatNegate = {
    "float.negate", ValidateSignature<auto(SizedFloatT)->SizedFloatT>};

// "float.add": float addition.
constexpr BuiltinInfo FloatAdd = {
    "float.add",
    ValidateSignature<auto(SizedFloatT, SizedFloatT)->SizedFloatT>};

// "float.sub": float subtraction.
constexpr BuiltinInfo FloatSub = {
    "float.sub",
    ValidateSignature<auto(SizedFloatT, SizedFloatT)->SizedFloatT>};

// "float.mul": float multiplication.
constexpr BuiltinInfo FloatMul = {
    "float.mul",
    ValidateSignature<auto(SizedFloatT, SizedFloatT)->SizedFloatT>};

// "float.div": float division.
constexpr BuiltinInfo FloatDiv = {
    "float.div",
    ValidateSignature<auto(SizedFloatT, SizedFloatT)->SizedFloatT>};

// "float.add_assign": float in-place addition.
constexpr BuiltinInfo FloatAddAssign = {
    "float.add_assign",
    ValidateSignature<auto(ByRef<SizedFloatT>, SizedFloatT)->NoReturn>};

// "float.sub_assign": float in-place subtraction.
constexpr BuiltinInfo FloatSubAssign = {
    "float.sub_assign",
    ValidateSignature<auto(ByRef<SizedFloatT>, SizedFloatT)->NoReturn>};

// "float.mul_assign": float in-place multiplication.
constexpr BuiltinInfo FloatMulAssign = {
    "float.mul_assign",
    ValidateSignature<auto(ByRef<SizedFloatT>, SizedFloatT)->NoReturn>};

// "float.div_assign": float in-place division.
constexpr BuiltinInfo FloatDivAssign = {
    "float.div_assign",
    ValidateSignature<auto(ByRef<SizedFloatT>, SizedFloatT)->NoReturn>};

// Converts between floating-point types, with a diagnostic if the value doesn't
// fit.
constexpr BuiltinInfo FloatConvertChecked = {
    "float.convert_checked", ValidateSignature<auto(FloatT)->FloatU>};

// "float.eq": float equality comparison.
constexpr BuiltinInfo FloatEq = {
    "float.eq", ValidateSignature<auto(SizedFloatT, SizedFloatT)->Bool>};

// "float.neq": float non-equality comparison.
constexpr BuiltinInfo FloatNeq = {
    "float.neq", ValidateSignature<auto(SizedFloatT, SizedFloatT)->Bool>};

// "float.less": float less than comparison.
constexpr BuiltinInfo FloatLess = {
    "float.less", ValidateSignature<auto(SizedFloatT, SizedFloatT)->Bool>};

// "float.less_eq": float less than or equal comparison.
constexpr BuiltinInfo FloatLessEq = {
    "float.less_eq", ValidateSignature<auto(SizedFloatT, SizedFloatT)->Bool>};

// "float.greater": float greater than comparison.
constexpr BuiltinInfo FloatGreater = {
    "float.greater", ValidateSignature<auto(SizedFloatT, SizedFloatT)->Bool>};

// "float.greater_eq": float greater than or equal comparison.
constexpr BuiltinInfo FloatGreaterEq = {
    "float.greater_eq",
    ValidateSignature<auto(SizedFloatT, SizedFloatT)->Bool>};

// "bool.eq": bool equality comparison.
constexpr BuiltinInfo BoolEq = {"bool.eq",
                                ValidateSignature<auto(Bool, Bool)->Bool>};

// "bool.neq": bool non-equality comparison.
constexpr BuiltinInfo BoolNeq = {"bool.neq",
                                 ValidateSignature<auto(Bool, Bool)->Bool>};

// "pointer.make_null": returns the representation of a null pointer value. This
// is an unformed state for the pointer type.
constexpr BuiltinInfo PointerMakeNull = {
    "pointer.make_null",
    ValidateSignature<auto()->MaybeUnformed<PointerTo<AnyType>>>};

// "pointer.is_null": determines whether the given pointer representation is a
// null pointer value.
constexpr BuiltinInfo PointerIsNull = {
    "pointer.is_null",
    ValidateSignature<auto(MaybeUnformed<PointerTo<AnyType>>)->Bool>};

// "type.and": facet type combination.
constexpr BuiltinInfo TypeAnd = {"type.and",
                                 ValidateSignature<auto(Type, Type)->Type>};

// The implementation of `Destroy` for a type. The argument must be checked with
// `type.can_destroy` first.
constexpr BuiltinInfo TypeDestroy = {
    "type.destroy", ValidateSignature<auto(ByRef<AnyType>)->NoReturn>};

// Returns a facet type that's used to determine whether a type can use
// `type.destroy`.
constexpr BuiltinInfo TypeCanDestroy = {"type.can_destroy",
                                        ValidateSignature<auto()->Type>};

}  // namespace BuiltinFunctionInfo

CARBON_DEFINE_ENUM_CLASS_NAMES(BuiltinFunctionKind) {
#define CARBON_SEM_IR_BUILTIN_FUNCTION_KIND(Name) \
  BuiltinFunctionInfo::Name.name,
#include "toolchain/sem_ir/builtin_function_kind.def"
};

// Returns the builtin function kind with the given name, or None if the name
// is unknown.
auto BuiltinFunctionKind::ForBuiltinName(llvm::StringRef name)
    -> BuiltinFunctionKind {
#define CARBON_SEM_IR_BUILTIN_FUNCTION_KIND(Name) \
  if (name == BuiltinFunctionInfo::Name.name) {   \
    return BuiltinFunctionKind::Name;             \
  }
#include "toolchain/sem_ir/builtin_function_kind.def"
  return BuiltinFunctionKind::None;
}

auto BuiltinFunctionKind::IsValidType(const File& sem_ir,
                                      llvm::ArrayRef<InstId> call_params,
                                      TypeId return_type) const -> bool {
  static constexpr ValidateFn* ValidateFns[] = {
#define CARBON_SEM_IR_BUILTIN_FUNCTION_KIND(Name) \
  BuiltinFunctionInfo::Name.validate,
#include "toolchain/sem_ir/builtin_function_kind.def"
  };
  return ValidateFns[AsInt()](sem_ir, call_params, return_type);
}

static auto IsLiteralType(const File& sem_ir, TypeId type_id) -> bool {
  // Unwrap adapters.
  type_id = sem_ir.types().GetTransitiveAdaptedType(type_id);
  auto type_inst_id = sem_ir.types().GetAsInst(type_id);
  return type_inst_id.Is<IntLiteralType>() ||
         type_inst_id.Is<FloatLiteralType>();
}

// Determines whether a builtin call involves an integer or floating-point
// literal in its arguments or return type. If so, for many builtins we want to
// treat the call as being compile-time-only. This is because `Core.IntLiteral`
// and `Core.FloatLiteral` have an empty runtime representation, and a value of
// such a type isn't necessarily a compile-time constant, so an arbitrary
// runtime value of such a type may not have a value available for the builtin
// to use. For example, given:
//
// var n: Core.IntLiteral() = 123;
//
// we would be unable to lower a runtime operation such as `(1 as i32) << n`
// because the runtime representation of `n` doesn't track its value at all.
//
// For now, we treat all operations involving `Core.IntLiteral` or
// `Core.FloatLiteral` as being compile-time-only.
//
// TODO: We will need to accept things like `some_i32 << 5` eventually. We could
// allow builtin calls at runtime if all the IntLiteral arguments have constant
// values, or add logic to the prelude to promote the `IntLiteral` operand to a
// different type in such cases.
//
// TODO: For now, we also treat builtins *returning* `Core.IntLiteral` or
// `Core.FloatLiteral` as being compile-time-only. This is mostly done for
// simplicity, but should probably be revisited.
static auto AnyLiteralTypes(const File& sem_ir, llvm::ArrayRef<InstId> arg_ids,
                            TypeId return_type_id) -> bool {
  if (IsLiteralType(sem_ir, return_type_id)) {
    return true;
  }
  for (auto arg_id : arg_ids) {
    if (IsLiteralType(sem_ir, sem_ir.insts().Get(arg_id).type_id())) {
      return true;
    }
  }
  return false;
}

auto BuiltinFunctionKind::IsCompTimeOnly(const File& sem_ir,
                                         llvm::ArrayRef<InstId> arg_ids,
                                         TypeId return_type_id) const -> bool {
  switch (*this) {
    case CharConvertChecked:
    case FloatConvertChecked:
    case IntConvertChecked:
      // Checked conversions are compile-time only.
      return true;

    case IntConvert:
    case IntSNegate:
    case IntComplement:
    case IntSAdd:
    case IntSSub:
    case IntSMul:
    case IntSDiv:
    case IntSMod:
    case IntAnd:
    case IntOr:
    case IntXor:
    case IntLeftShift:
    case IntRightShift:
    case IntEq:
    case IntNeq:
    case IntLess:
    case IntLessEq:
    case IntGreater:
    case IntGreaterEq:
      // Integer operations are compile-time-only if they involve literal types.
      // See AnyLiteralTypes comment for explanation.
      return AnyLiteralTypes(sem_ir, arg_ids, return_type_id);

    case TypeAnd:
      return true;

    case TypeCanDestroy:
      // Type queries must be compile-time.
      return true;

    default:
      // TODO: Should the sized MakeType functions be compile-time only? We
      // can't produce diagnostics for bad sizes at runtime.
      return false;
  }
}

}  // namespace Carbon::SemIR