llvm dev - Aug 2014 - [LLVMdev] Prevent clang from replacing code with library calls

Hi Jim,
I have tried "-fno-builtin" but it didn't help.
Thanks,
David


On Tue, Aug 5, 2014 at 12:12 AM, Jim Grosbach <grosbach at apple.com>
wrote:
> Hi David,
>
> "-fno-builtin” is probably what you want.
>
> -Jim
>
> On Aug 4, 2014, at 2:19 AM, David Sela <sela.david at gmail.com>
wrote:
>
> Clang optimizes code by replacing some parts with efficient library
> functions.
>
> For example the following code:
>
> for (i=0;i<size;++i)
>        dest[i]=src[i];
>
> will be compiled to (target=ARM assembly):
>
> bl      __aeabi_memcpy(PLT)
>
> The compile cmd:
>
> /usr/share/android-arm-l14-toolchain/bin/clang31 -cc1 -triple
> arm-none-linux-androideabi -S -target-abi aapcs-linux -target-cpu arm1022e
> -backend-option -arm-enable-ehabi -backend-option
> -arm-enable-ehabi-descriptors -backend-option -arm-ignore-has-ras
> -internal-isystem
> /usr/share/android-arm-l14-toolchain/lib/clang/3.1/include
> -internal-externc-isystem
> /usr/share/android-arm-l14-toolchain/bin/../sysroot/usr/include -o
> myMemcpy.s -x c myMemcpy.c
>
>
> Is there a flag or some other way to prevent the compiler from replacing
> the code with library calls?
>
>
> Thanks in advance,
> David
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20140805/96e949f1/attachment.html>

I'm not sure then. Clang 3.1 is rather old. It's possible that was
broken in that version. Sorry I wasn't more help. That's the correct
option to control the behavior.
> On Aug 5, 2014, at 12:01 AM, David Sela <sela.david at gmail.com>
wrote:
> 
> Hi Jim,
> I have tried "-fno-builtin" but it didn't help.
> Thanks,
> David
> 
> 
>> On Tue, Aug 5, 2014 at 12:12 AM, Jim Grosbach <grosbach at
apple.com> wrote:
>> Hi David,
>> 
>> "-fno-builtin” is probably what you want.
>> 
>> -Jim
>> 
>>> On Aug 4, 2014, at 2:19 AM, David Sela <sela.david at
gmail.com> wrote:
>>> 
>>> Clang optimizes code by replacing some parts with efficient library
functions.
>>> 
>>> For example the following code:
>>> 
>>> 
>>> for (i=0;i<size;++i)
>>>        dest[i]=src[i];
>>> will be compiled to (target=ARM assembly):
>>> 
>>> 
>>> bl      __aeabi_memcpy(PLT)
>>> The compile cmd:
>>> 
>>> /usr/share/android-arm-l14-toolchain/bin/clang31 -cc1 -triple
arm-none-linux-androideabi -S -target-abi aapcs-linux -target-cpu arm1022e
-backend-option -arm-enable-ehabi -backend-option -arm-enable-ehabi-descriptors
-backend-option -arm-ignore-has-ras -internal-isystem
/usr/share/android-arm-l14-toolchain/lib/clang/3.1/include
-internal-externc-isystem
/usr/share/android-arm-l14-toolchain/bin/../sysroot/usr/include -o myMemcpy.s -x
c myMemcpy.c
>>> 
>>> 
>>> 
>>> Is there a flag or some other way to prevent the compiler from
replacing the code with library calls?
>>> 
>>> 
>>> 
>>> Thanks in advance,
>>> David
>>> 
>>> 
>>> 
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20140805/7cbe8d19/attachment.html>

Hi,

I downloaded the latest NDK (r10) and compiled with the following cmd:
*arm-linux-androideabi-clang myMemcpy.c -S -fno-builtin -o0*
It still produces assembly with a call to "memcpy". Maybe the
-*fno-builtin
*is broken also in the latest release.
Do you have some other idea that can help here?

Thanks,
David


On Tue, Aug 5, 2014 at 11:00 AM, Jim Grosbach <grosbach at apple.com>
wrote:
> I'm not sure then. Clang 3.1 is rather old. It's possible that was
broken
> in that version. Sorry I wasn't more help. That's the correct
option to
> control the behavior.
>
> On Aug 5, 2014, at 12:01 AM, David Sela <sela.david at gmail.com>
wrote:
>
> Hi Jim,
> I have tried "-fno-builtin" but it didn't help.
> Thanks,
> David
>
>
> On Tue, Aug 5, 2014 at 12:12 AM, Jim Grosbach <grosbach at apple.com>
wrote:
>
>> Hi David,
>>
>> "-fno-builtin” is probably what you want.
>>
>> -Jim
>>
>> On Aug 4, 2014, at 2:19 AM, David Sela <sela.david at gmail.com>
wrote:
>>
>> Clang optimizes code by replacing some parts with efficient library
>> functions.
>>
>> For example the following code:
>>
>> for (i=0;i<size;++i)
>>        dest[i]=src[i];
>>
>> will be compiled to (target=ARM assembly):
>>
>> bl      __aeabi_memcpy(PLT)
>>
>> The compile cmd:
>>
>> /usr/share/android-arm-l14-toolchain/bin/clang31 -cc1 -triple
>> arm-none-linux-androideabi -S -target-abi aapcs-linux -target-cpu
arm1022e
>> -backend-option -arm-enable-ehabi -backend-option
>> -arm-enable-ehabi-descriptors -backend-option -arm-ignore-has-ras
>> -internal-isystem
>> /usr/share/android-arm-l14-toolchain/lib/clang/3.1/include
>> -internal-externc-isystem
>> /usr/share/android-arm-l14-toolchain/bin/../sysroot/usr/include -o
>> myMemcpy.s -x c myMemcpy.c
>>
>>
>> Is there a flag or some other way to prevent the compiler from
replacing
>> the code with library calls?
>>
>>
>> Thanks in advance,
>> David
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20140807/675fe8d2/attachment.html>