mulle-clang

This is an Objective-C compiler based on clang 17.0.6, written for the, written for the mulle-objc runtime. It corresponds to mulle-objc-runtime v0.20 or better.

See README.txt for more information about clang

The compiler can be used to:

1. compile Objective-C code for mulle-objc
2. compile C code

It is not recommended to use it for C++, since that is not tested. It is not recommended to use it for other Objective-C runtimes, since there have been some changes, that affect other runtimes.

Operation

The compiler compiles Objective-C source for the mulle-objc runtime by default. When compiling for mulle-objc the compiler will use the meta-ABI for all Objective-C method calls. C function calls use the platform convention. The resultant .o files are linkable like any other compiled C code.

AAM - Always Autorelease Mode

The compiler has a special mode called AAM. This changes the Objective-C language in the following ways:

1. There is a tranformation done on selector names

   Name	Transformed Name
   alloc	instantiate
   new	instantiatedObject
   copy	immutableInstance
   mutableCopy	mutableInstance

2. You can not access instance variables directly, but must use properties (or methods)

3. You can not do explicit memory management (like -dealloc, -autorelease, -release, -retain, -retainCount etc.)

The transformed methods will return objects that are autoreleased. Hence the name of the mode. The net effect is, that you have a mode that is ARC-like, yet understandable and much simpler.

Your ARC code may not run in AAM, but AAM code should run in ARC with no problems. If you can't do something in AAM, put it in a category in regular Objective-C style.

The compiler handles .aam files, which enables AAM ("Always Autoreleased Mode").

Additional Compiler options and defined macros

Name	Compiler	Default	Description
__MULLE_OBJC__	-	-	Compiling for mulle-objc
__MULLE_OBJC_UNIVERSEID__	-fobjc-universename=name	-	id of the universe, or 0 for default
__MULLE_OBJC_UNIVERSENAME__	-fobjc-universename=name	-	name of the universe, or NULL for default
__OBJC_CLASS__	-	-	name of the class thats currently being compiled
__OBJC_CATEGORY__	-	-	name of the category that's currently being compiled
__MULLE_OBJC_CLASSID__	-	-	classid of the class thats currently being compiled
__MULLE_OBJC_CATEGORYID__	-	-	uniqueud of the category thats currently being compiled

The following table represents option pairs, that logically exclude each other. Either one is always defined.

Name	Compiler	Default	Description
__MULLE_OBJC_AAM__	.aam file	-	AAM is enabled
__MULLE_OBJC_NO_AAM__	.m file	-	AAM is not enabled
__MULLE_OBJC_TPS__	-fobjc-tps	YES	TPS (tagged pointer support) is enabled
__MULLE_OBJC_NO_TPS__	-fno-objc-tps	NO	TPS is not enabled
__MULLE_OBJC_FCS__	-fobjc-fcs	YES	FCS fast method/class support is enabled
__MULLE_OBJC_NO_FCS__	-fno-objc-fcs	NO	FCS is not enabled
__MULLE_OBJC_TAO__	-fobjc-tao	-	TAO (thread affine objects) is enabled
__MULLE_OBJC_NO_TAO__	-fno-objc-tao	-	TAO is not enabled

The default is -fobjc-tao for -O0 builds and -fno-objc-tao for optimized builds.

Macros used in Code Generation

The compiler output can be tweaked with the following preprocessor macros. All macros must be defined with a simple integer, no expressions. All of them are optional, unless indicated otherwise. The runtime, the Objective-C Foundation on top of the runtime and the user application, will define them.

Name	Description
MULLE_OBJC_RUNTIME_VERSION_MAJOR	Major of version of the runtime
MULLE_OBJC_RUNTIME_VERSION_MINOR	Minor of version of the runtime
MULLE_OBJC_RUNTIME_VERSION_PATCH	Patch of version of the runtime
MULLE_OBJC_FOUNDATION_VERSION_MAJOR	Major of version of the Foundation
MULLE_OBJC_FOUNDATION_VERSION_MINOR	Minor of version of the Foundation
MULLE_OBJC_FOUNDATION_VERSION_PATCH	Patch of version of the Foundation
MULLE_OBJC_USER_VERSION_MAJOR	User supplied major of version
MULLE_OBJC_USER_VERSION_MINOR	User supplied minor of version
MULLE_OBJC_USER_VERSION_PATCH	User supplied patch of version. All these version information values will be stored in the emitted object file.
MULLE_OBJC_FASTCLASSHASH_0	First unique ID of a fast class
...	...
MULLE_OBJC_FASTCLASSHASH_63	Last unique ID of a fast class

Functions used in Code Generation

These are the runtime functions used for method calling, retain/release management, class lookup and exception handling. They are defined in the runtime.

All

Function	Memo
mulle_objc_exception_tryenter	@throw
mulle_objc_exception_tryexit	@finally
mulle_objc_exception_extract	@catch
mulle_objc_exception_match	@catch

Inlining method calls

With -fobjc-inline-method-calls=[1-5] you can control the level of inlining. If you don't specify it, the optimization level is mapped to a inlining setting. (See table below)

cmake sets -O3 as the optimization level, for Release builds, though you may want to prefer -O2 or -Oz for Objective-C code.

Inlining	-fobjc-inline-method-calls	Optimization Level (if -fobjc-inline-method-calls is unset)
No inlining	1	-O0
Minimal inlining	2	-O1/-Os
Partial inlining	3	-O2/-Oz
Default inlining	4	-O3/-O4
Full inlining	5	-O5+

Also note, that if you combine -O0 with -fobjc-inline-method-calls, there won't be any inlining, since -O0 prohibits it.

No inlining

Function	Memo
mulle_objc_object_call	[self foo:bar]
mulle_objc_object_supercall	[super foo:bar]
mulle_objc_object_lookup_infraclass_nofail	[Foo ... for methods
mulle_objc_object_lookup_infraclass_nofast_nofail	__MULLE_OBJC_NO_FCS__
mulle_objc_global_lookup_infraclass_nofail	[Foo ... for functions
mulle_objc_global_lookup_infraclass_nofast_nofail	__MULLE_OBJC_NO_FCS__

Minimal inlining

Like "No inlining" but one function is replaced with a minimally inlining version:

Function	Memo
mulle_objc_object_call_inline_minimal	[self foo:bar]

Partial inlining

Like "No inlining" but four functions are replaced with four inlining functions, and two new inlining functions are used:

Function	Memo
mulle_objc_object_call_inline_partial	[self foo:bar]
mulle_objc_object_supercall_inline_partial	[super foo:bar]
mulle_objc_object_lookup_infraclass_inline_nofail	[Foo ... for methods
mulle_objc_global_lookup_infraclass_inline_nofail	__MULLE_OBJC_NO_FCS__
mulle_objc_object_lookup_infraclass_inline_nofail_nofast	[Foo ... for functions
mulle_objc_global_lookup_infraclass_inline_nofail_nofast	__MULLE_OBJC_NO_FCS__
mulle_objc_object_retain_inline	[foo retain]
mulle_objc_object_release_inline	[foo release]

The partial inlining code, tries to eliminate some constant setup cost by moving it to the compilation. This can be good for multiple calls involving the same object.

Default inlining

Like "Partial inlining", but two functions are replaced with more inlined functions:

Function	Memo
mulle_objc_object_call_inline	[self foo:bar]
mulle_objc_object_call_super_inline	[super foo:bar]

The default inline code checks the cache for an immediate hit, then slower shared coded is used for further cache lookup and cache misses.

Full inlining

Like "Default inlining", but two functions are replaced with fully inlined functions:

Function	Memo
mulle_objc_object_call_inline_full	[self foo:bar]
mulle_objc_object_call_super_inline_full	[super foo:bar]

The full inline code checks the cache for a hit, then slower shared coded is used for cache misses.

Build

You can use the original llvm project instructions to build the project. But do checkout cmake-ninja for a small build script, that sets important build values.

If you are building inside a fresh system, try install-prerequisites that can install all prerequisites for a macos or debian based system.

Afterwards head on over to mulle-objc to get the runtime libraries.

Author

Nat! for Codeon GmbH

Original README.md follows

The LLVM Compiler Infrastructure

Welcome to the LLVM project!

This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.

The LLVM project has multiple components. The core of the project is itself called "LLVM". This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.

C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.

Other components include: the libc++ C++ standard library, the LLD linker, and more.

Getting the Source Code and Building LLVM

Consult the Getting Started with LLVM page for information on building and running LLVM.

For information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.

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Join the LLVM Discourse forums, Discord chat, or #llvm IRC channel on OFTC.

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