pub const Extended = enum(u16) {
    /// A struct type definition. Contains references to ZIR instructions for
    /// the field types, defaults, and alignments.
    /// `operand` is payload index to `StructDecl`.
    /// `small` is `StructDecl.Small`.
    struct_decl,
    /// An enum type definition. Contains references to ZIR instructions for
    /// the field value expressions and optional type tag expression.
    /// `operand` is payload index to `EnumDecl`.
    /// `small` is `EnumDecl.Small`.
    enum_decl,
    /// A union type definition. Contains references to ZIR instructions for
    /// the field types and optional type tag expression.
    /// `operand` is payload index to `UnionDecl`.
    /// `small` is `UnionDecl.Small`.
    union_decl,
    /// An opaque type definition. Contains references to decls and captures.
    /// `operand` is payload index to `OpaqueDecl`.
    /// `small` is `OpaqueDecl.Small`.
    opaque_decl,
    /// A tuple type. Note that tuples are not namespace/container types.
    /// `operand` is payload index to `TupleDecl`.
    /// `small` is `fields_len: u16`.
    tuple_decl,
    /// Implements the `@This` builtin.
    /// `operand` is `src_node: i32`.
    this,
    /// Implements the `@returnAddress` builtin.
    /// `operand` is `src_node: i32`.
    ret_addr,
    /// Implements the `@src` builtin.
    /// `operand` is payload index to `LineColumn`.
    builtin_src,
    /// Implements the `@errorReturnTrace` builtin.
    /// `operand` is `src_node: i32`.
    error_return_trace,
    /// Implements the `@frame` builtin.
    /// `operand` is `src_node: i32`.
    frame,
    /// Implements the `@frameAddress` builtin.
    /// `operand` is `src_node: i32`.
    frame_address,
    /// Same as `alloc` from `Tag` but may contain an alignment instruction.
    /// `operand` is payload index to `AllocExtended`.
    /// `small`:
    ///  * 0b000X - has type
    ///  * 0b00X0 - has alignment
    ///  * 0b0X00 - 1=const, 0=var
    ///  * 0bX000 - is comptime
    alloc,
    /// The `@extern` builtin.
    /// `operand` is payload index to `BinNode`.
    builtin_extern,
    /// Inline assembly.
    /// `small`:
    ///  * 0b00000000_000XXXXX - `outputs_len`.
    ///  * 0b000000XX_XXX00000 - `inputs_len`.
    ///  * 0b0XXXXX00_00000000 - `clobbers_len`.
    ///  * 0bX0000000_00000000 - is volatile
    /// `operand` is payload index to `Asm`.
    @"asm",
    /// Same as `asm` except the assembly template is not a string literal but a comptime
    /// expression.
    /// The `asm_source` field of the Asm is not a null-terminated string
    /// but instead a Ref.
    asm_expr,
    /// Log compile time variables and emit an error message.
    /// `operand` is payload index to `NodeMultiOp`.
    /// `small` is `operands_len`.
    /// The AST node is the compile log builtin call.
    compile_log,
    /// The builtin `@TypeOf` which returns the type after Peer Type Resolution
    /// of one or more params.
    /// `operand` is payload index to `TypeOfPeer`.
    /// `small` is `operands_len`.
    /// The AST node is the builtin call.
    typeof_peer,
    /// Implements the `@min` builtin for more than 2 args.
    /// `operand` is payload index to `NodeMultiOp`.
    /// `small` is `operands_len`.
    /// The AST node is the builtin call.
    min_multi,
    /// Implements the `@max` builtin for more than 2 args.
    /// `operand` is payload index to `NodeMultiOp`.
    /// `small` is `operands_len`.
    /// The AST node is the builtin call.
    max_multi,
    /// Implements the `@addWithOverflow` builtin.
    /// `operand` is payload index to `BinNode`.
    /// `small` is unused.
    add_with_overflow,
    /// Implements the `@subWithOverflow` builtin.
    /// `operand` is payload index to `BinNode`.
    /// `small` is unused.
    sub_with_overflow,
    /// Implements the `@mulWithOverflow` builtin.
    /// `operand` is payload index to `BinNode`.
    /// `small` is unused.
    mul_with_overflow,
    /// Implements the `@shlWithOverflow` builtin.
    /// `operand` is payload index to `BinNode`.
    /// `small` is unused.
    shl_with_overflow,
    /// `operand` is payload index to `UnNode`.
    c_undef,
    /// `operand` is payload index to `UnNode`.
    c_include,
    /// `operand` is payload index to `BinNode`.
    c_define,
    /// `operand` is payload index to `UnNode`.
    wasm_memory_size,
    /// `operand` is payload index to `BinNode`.
    wasm_memory_grow,
    /// The `@prefetch` builtin.
    /// `operand` is payload index to `BinNode`.
    prefetch,
    /// Implement builtin `@setFloatMode`.
    /// `operand` is payload index to `UnNode`.
    set_float_mode,
    /// Implements the `@errorCast` builtin.
    /// `operand` is payload index to `BinNode`. `lhs` is dest type, `rhs` is operand.
    error_cast,
    /// `operand` is payload index to `UnNode`.
    await_nosuspend,
    /// Implements `@breakpoint`.
    /// `operand` is `src_node: i32`.
    breakpoint,
    /// Implement builtin `@disableInstrumentation`. `operand` is `src_node: i32`.
    disable_instrumentation,
    /// Implement builtin `@disableIntrinsics`. `operand` is `src_node: i32`.
    disable_intrinsics,
    /// Implements the `@select` builtin.
    /// `operand` is payload index to `Select`.
    select,
    /// Implement builtin `@errToInt`.
    /// `operand` is payload index to `UnNode`.
    int_from_error,
    /// Implement builtin `@errorFromInt`.
    /// `operand` is payload index to `UnNode`.
    error_from_int,
    /// Implement builtin `@Type`.
    /// `operand` is payload index to `Reify`.
    /// `small` contains `NameStrategy`.
    reify,
    /// Implements the `@asyncCall` builtin.
    /// `operand` is payload index to `AsyncCall`.
    builtin_async_call,
    /// Implements the `@cmpxchgStrong` and `@cmpxchgWeak` builtins.
    /// `small` 0=>weak 1=>strong
    /// `operand` is payload index to `Cmpxchg`.
    cmpxchg,
    /// Implement builtin `@cVaArg`.
    /// `operand` is payload index to `BinNode`.
    c_va_arg,
    /// Implement builtin `@cVaCopy`.
    /// `operand` is payload index to `UnNode`.
    c_va_copy,
    /// Implement builtin `@cVaEnd`.
    /// `operand` is payload index to `UnNode`.
    c_va_end,
    /// Implement builtin `@cVaStart`.
    /// `operand` is `src_node: i32`.
    c_va_start,
    /// Implements the following builtins:
    /// `@ptrCast`, `@alignCast`, `@addrSpaceCast`, `@constCast`, `@volatileCast`.
    /// Represents an arbitrary nesting of the above builtins. Such a nesting is treated as a
    /// single operation which can modify multiple components of a pointer type.
    /// `operand` is payload index to `BinNode`.
    /// `small` contains `FullPtrCastFlags`.
    /// AST node is the root of the nested casts.
    /// `lhs` is dest type, `rhs` is operand.
    ptr_cast_full,
    /// `operand` is payload index to `UnNode`.
    /// `small` contains `FullPtrCastFlags`.
    /// Guaranteed to only have flags where no explicit destination type is
    /// required (const_cast and volatile_cast).
    /// AST node is the root of the nested casts.
    ptr_cast_no_dest,
    /// Implements the `@workItemId` builtin.
    /// `operand` is payload index to `UnNode`.
    work_item_id,
    /// Implements the `@workGroupSize` builtin.
    /// `operand` is payload index to `UnNode`.
    work_group_size,
    /// Implements the `@workGroupId` builtin.
    /// `operand` is payload index to `UnNode`.
    work_group_id,
    /// Implements the `@inComptime` builtin.
    /// `operand` is `src_node: i32`.
    in_comptime,
    /// Restores the error return index to its last saved state in a given
    /// block. If the block is `.none`, restores to the state from the point
    /// of function entry. If the operand is not `.none`, the restore is
    /// conditional on the operand value not being an error.
    /// `operand` is payload index to `RestoreErrRetIndex`.
    /// `small` is undefined.
    restore_err_ret_index,
    /// Retrieves a value from the current type declaration scope's closure.
    /// `operand` is `src_node: i32`.
    /// `small` is closure index.
    closure_get,
    /// Used as a placeholder instruction which is just a dummy index for Sema to replace
    /// with a specific value. For instance, this is used for the capture of an `errdefer`.
    /// This should never appear in a body.
    value_placeholder,
    /// Implements the `@fieldParentPtr` builtin.
    /// `operand` is payload index to `FieldParentPtr`.
    /// `small` contains `FullPtrCastFlags`.
    /// Guaranteed to not have the `ptr_cast` flag.
    /// Uses the `pl_node` union field with payload `FieldParentPtr`.
    field_parent_ptr,
    /// Get a type or value from `std.builtin`.
    /// `operand` is `src_node: i32`.
    /// `small` is an `Inst.BuiltinValue`.
    builtin_value,
    /// Provide a `@branchHint` for the current block.
    /// `operand` is payload index to `UnNode`.
    /// `small` is unused.
    branch_hint,
    /// Compute the result type for in-place arithmetic, e.g. `+=`.
    /// `operand` is `Zir.Inst.Ref` of the loaded LHS (*not* its type).
    /// `small` is an `Inst.InplaceOp`.
    inplace_arith_result_ty,
    /// Marks a statement that can be stepped to but produces no code.
    /// `operand` and `small` are ignored.
    dbg_empty_stmt,
    /// At this point, AstGen encountered a fatal error which terminated ZIR lowering for this body.
    /// A file-level error has been reported. Sema should terminate semantic analysis.
    /// `operand` and `small` are ignored.
    /// This instruction is always `noreturn`, however, it is not considered as such by ZIR-level queries. This allows AstGen to assume that
    /// any code may have gone here, avoiding false-positive "unreachable code" errors.
    astgen_error,

    pub const InstData = struct {
        opcode: Extended,
        small: u16,
        operand: u32,
    };
}