[LLVMdev] Prevent clang from replacing code with library calls

[Jim Grosbach]

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
> 
> 
> 
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