Standard Library Builtin Stuff

Vogel · February 14, 2019, 11:59pm

Hello!

I've been trying to investigate how the standard library works and I've found something that I don't fully understand.

It appears as if everything eventually boils down to "Builtin" stuff that's not actually declared anywhere, but just assumed to exist within the stdlib.

For example, a Bool is really just a wrapped for a Builtin.Int1.

Now I would like to know: Where do I find the declaration of this Int1? Or, even more interesting: Where do I find a list of all the Builtin types?

Thank you in advance,

Best regards, Vogel.

scanon · February 15, 2019, 12:04am

Builtins generally expand to LLVM IR types and operations. The mappings are defined directly in the compiler (mostly include/swift/AST/Builtins.def and lib/AST/Builtins.cpp--for example, the Builtin.Int${N} types like Builtin.Int1 are defined via the machinery starting on line 102).

Pogosito · September 30, 2023, 11:59am

Hi, thanks for reply.

Can you explain where find implementation of Builtin.NativeObject.

I already use your answer and found that Builtin.NativeObject mapped to TheNativeObjectType (in Builtins.cpp). It maps by context ASTContext

But there is no mention TheNativeObjectType in ASTContext.cpp ASTContext.h

I try to google TheNativeObjectType in context of LLVM and did not find it.

Could you give more information where find implementation of Builtin type and operations ?

Thanks

Max_Desiatov · September 30, 2023, 4:19pm

AFAIU, most if not all Builtin functions map to LLVM IR instructions, which you can look up in the LLVM language reference.

Pogosito · September 30, 2023, 4:26pm

Thank you very much for your reply.

I already viewed this page and did not find definition of Builtin.NativeObject

With Respect
Pogos

Alejandro · September 30, 2023, 6:04pm

The type is defined here in ASTContext.h:

github.com

apple/swift/blob/e8208547846c6bd4b9333e587d328eea53e45054/include/swift/AST/ASTContext.h#L1009


      
            // Type manipulation routines.
            //===--------------------------------------------------------------------===//
          
            // Builtin type and simple types that are used frequently.
            const CanType TheErrorType;             /// This is the ErrorType singleton.
            const CanType TheUnresolvedType;        /// This is the UnresolvedType singleton.
            const CanType TheEmptyTupleType;        /// This is '()', aka Void
            const CanType TheEmptyPackType;
            const CanType TheAnyType;               /// This is 'Any', the empty protocol composition
          #define SINGLETON_TYPE(SHORT_ID, ID) \
            const CanType The##SHORT_ID##Type;
          #include "swift/AST/TypeNodes.def"
          
            const CanType TheIEEE32Type;            /// 32-bit IEEE floating point
            const CanType TheIEEE64Type;            /// 64-bit IEEE floating point
            
            // Target specific types.
            const CanType TheIEEE16Type;            /// 16-bit IEEE floating point
            const CanType TheIEEE80Type;            /// 80-bit IEEE floating point
            const CanType TheIEEE128Type;           /// 128-bit IEEE floating point
            const CanType ThePPC128Type;            /// 128-bit PowerPC 2xDouble

and in TypeNodes.def:

github.com

apple/swift/blob/main/include/swift/AST/TypeNodes.def

//===--- TypeNodes.def - Swift Type AST Metaprogramming ---------*- C++ -*-===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file defines macros used for macro-metaprogramming with types.
//
//===----------------------------------------------------------------------===//

/// TYPE(id, parent)
///   If the type node is not abstract, its enumerator value is
///   TypeKind::id.  The node's class name is 'id##Type', and the name of
///   its base class (in the Type hierarchy) is 'parent' (including

This file has been truncated. show original

The actual type definition for this type is:

github.com

apple/swift/blob/e8208547846c6bd4b9333e587d328eea53e45054/include/swift/AST/Types.h#L1715


      
          public:
            static bool classof(const TypeBase *T) {
              return T->getKind() == TypeKind::BuiltinPackIndex;
            }
          };
          DEFINE_EMPTY_CAN_TYPE_WRAPPER(BuiltinPackIndexType, BuiltinType)
          
          /// BuiltinNativeObjectType - The builtin opaque object-pointer type.
          /// Useful for keeping an object alive when it is otherwise being
          /// manipulated via an unsafe pointer type.
          class BuiltinNativeObjectType : public BuiltinType {
            friend class ASTContext;
            BuiltinNativeObjectType(const ASTContext &C)
              : BuiltinType(TypeKind::BuiltinNativeObject, C) {}
          public:
            static bool classof(const TypeBase *T) {
              return T->getKind() == TypeKind::BuiltinNativeObject;
            }
          };
          DEFINE_EMPTY_CAN_TYPE_WRAPPER(BuiltinNativeObjectType, BuiltinType)

Pogosito · September 30, 2023, 6:14pm

Thank you very much, I should have read the sources more carefully, thank you

Pogosito · October 7, 2023, 6:16am

Sorry to bother you again.

Could you tell me if I understood correctly that BuiltinNativeObjectType is just a "universal" pointer to any object?

And even somehow embarrassingly, I again could not find the implementation of Builtin functions, for example cancel.

I find only a '.def' file in which most of the functions I'm interested in are wrapped in BUILTIN_MISC_OPERATION_WITH_SILGEN, but the description of what does (and what is it) this is completely incomprehensible to me

Judging by the description, these functions should be generated at the SIL stage, I tried to look at the implementation of the cancel method, generated SIL and got

// Task.cancel()

sil [available 12.0.0] @$sScT6cancelyyF : $@convention(method) <τ_0_0, τ_0_1 where τ_0_0 : Sendable, τ_0_1 : Error> (@guaranteed Task<τ_0_0, τ_0_1>) -> ()

which does not give any ideas for further steps

ktoso · November 20, 2023, 1:27am

Task.cancel is not a builtin:

First go to Task.swift and find cancel:

  public func cancel() {
    _taskCancel(_task)
  }

find that function in the same file:

@available(SwiftStdlib 5.1, *)
@_silgen_name("swift_task_cancel")
public func _taskCancel(_ task: Builtin.NativeObject)

Then find:

SWIFT_CC(swift)
static void swift_task_cancelImpl(AsyncTask *task)

in TaskStatus.cpp.

Builtins like creating groups etc are declared in Builtins.def

BUILTIN_MISC_OPERATION_WITH_SILGEN(GetCurrentExecutor, "getCurrentExecutor", "", Special)

and then the signature is in Builtins.cpp:

  case BuiltinValueKind::GetCurrentExecutor:
    return getGetCurrentExecutor(Context, Id);

and implementation in GenBuiltin.cpp:


  // emitGetCurrentExecutor has no arguments.
  if (Builtin.ID == BuiltinValueKind::GetCurrentExecutor) {
    emitGetCurrentExecutor(IGF, out);
    return;
  }

The above emit forms a call to a runtime function, which eventually ends up in plain runtime function (declared in RuntimeFunctions.def):

SWIFT_CC(swift)
static SerialExecutorRef swift_task_getCurrentExecutorImpl() { ... }

Basically keep looking where GetCurrentExecutor is used, and you'll find all important places -- there's quite a few.

Hope this helps,