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

Perevalov Alexey via llvm-dev
Tue, 27 Sep 2016 07:06:51 -0000

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>
>
> int main(void)
>        {
>                NSString *str = [NSString
stringWithCString:"TEST"];
>                NSLog(@"test object %@", str);
>                return 0;
>        }
>
> Compilation in xcode's clang

>Which version?

I think, it doesn't matter, due to with xcode's clang all fine

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?
>
>
>
>
> 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
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