[cfe-users] [llvm-dev] objc object file generated for gnustep runtime for ELF target is too big

[Mehdi Amini via cfe-users]

Sent from my iPhone

> On Sep 27, 2016, at 12:06 AM, Perevalov Alexey <Alexey.Perevalov at hotmail.com> wrote:
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> От: mehdi.amini at apple.com <mehdi.amini at apple.com> от имени Mehdi Amini <mehdi.amini at apple.com>
> Отправлено: 27 сентября 2016 г. 8:46
> Кому: Perevalov Alexey
> Копия: cfe-users at lists.llvm.org; llvm-dev at lists.llvm.org
> Тема: Re: [llvm-dev] objc object file generated for gnustep runtime for ELF target is too big
>     
> 
>> On Sep 26, 2016, at 6:33 AM, Perevalov Alexey via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>> 
>> Dear community,
>> 
>> 
>> I'm using gnustep runtime -fobjc-runtime=gnustep with       gnustep-libobjc2 (https://github.com/gnustep/libobjc2) and
>> 
>> Cocotron/Chameleon.
>> 
>> For following source file
>> 
>> #import <Foundation/Foundation.h>
>>       #import <UIKit/UIKit.h>
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>> int main(void)
>>         {
>>                 NSString *str = [NSString stringWithCString:"TEST"];
>>                 NSLog(@"test object %@", str);
>>                 return 0;
>>         }
>> 
>> Compilation in xcode's clang
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>> Which version?
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> I think, it doesn't matter, due to with xcode's clang all fine

It does: if there is a recent regression in the compiler, it may be in Xcode 8 as well. Can you update and try?

-- 
Mehdi

> but if you intersting,
> 
> xcrun -sdk iphoneos clang --version
> Apple LLVM version 7.0.0 (clang-700.1.76)
> Target: x86_64-apple-darwin15.0.0
> Thread model: posix
> 
> also all fine with open source llvm clang if I choose ios as -fobjc-runtime, I got troubles only with gnustep runtime in clang+llvm-3.8.0 and 3.9.x.
> 
>> — 
>> Mehdi
> 
> 
>> xcrun -sdk iphoneos clang -arch armv7s -mios-version-min=6.1 -c       test_foundation.m -o test_foundation_apple.o
>> gives following result:
>> 1. object file has only 3156 bytes size
>> 2. and in disassembler only main function
>> 3. the final executable will be 49992 bytes size in this case
>> 
>> 
>> But compilation in llvm's clang downloaded from  http://llvm.org/releases/3.8.0/clang+llvm-3.8.0-x86_64-apple-darwin.tar.xz
>> 
>> (
>> clang version 3.8.0 (tags/RELEASE_380/final)
>>       Target: x86_64-apple-darwin15.0.0
>>       Thread model: posix
>>       )
>> gives another results:
>> 1. object file has 159044 bytes size
>> 2. in disassembler a lot of unnecessary .objc_property_list,       .objc_method_list, .objc_protocol_list and .objc_protocol  in .bss       and .data section
>> 3. the final binary size is 101837 bytes size
>> 
>> 
>> 
>> If comment in above sample #import <UIKit/UIKit.h, the size of       object file and binary file in xcode compilation will be the same,
>> but size binary and object file in case of       clang+llvm-3.8.0-x86_64-apple-darwin compilation will be reduced       sufficiently:
>> binary 28569 and object 36952 accordingly.
>> 
>> 
>> 
>> Looks like all protocols from UIKit.h is placed into       binary/object even it's not used there.
>> I got 3.9.0 from public git (branch release_39 of clang git       repository) and found that all protocols interpret as definition       (isThisDeclarationADefinition),
>> and in CGObjCGNU.cpp it's placed into object file whenever it's       used or not. With the same open source compiler and       -fobjc-runtime=ios protocols are not putting into
>> object file even in compilation for ELF (I used -target       arm-linux-gnueabi).
>> I used default binutil linker, not llvm's ld.ldd, due to I have problem with relocation on ARM.
>> I didn't use LTO, due to my linker doesn't have plugin support (I didnt' yet recompile it).
>> 
>> Could somebody point me where to solve that problem, is it AST       generation stage, or linkage stage or maybe it's not a problem and just LTO could be solution here?
>> 
>> 
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>> p.s. It's not only one issue found by me in gnustep runtime       generation, and I'll report these issues in next emails.
>> 
>> 
>> 
>> 
>> 
>>          Best regards,
>>         Alexey Perevalov
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
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