[LLVMdev] Compilation error while cross compiling LLVM for ARM - the __clear_cache issue - now the __sync_val_compare_and_swap issue

[Xerxes Rånby]

Prasanth J wrote:
>
> Hi all,
> with reference to the reply below, I downloaded toolchain from
> codesourcery (arm-2009q1-203-arm-none-linux-gnueabi) with gcc 4.3.3...
> when i compile llvm+clang with this toolchain i am getting the
> following error
>
> make[4]: Entering directory
> `/home/prasanth/LLVM_ARM/llvm-with-armgcc433/llvm-obj/tools/clang/tools/c-index-test'
> llvm[4]: Linking Release executable c-index-test (without symbols)
> /home/prasanth/arm-toolchain/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.3/../../../../arm-none-linux-gnueabi/bin/ld:
> /home/prasanth/LLVM_ARM/llvm-with-armgcc433/llvm-obj/Release/bin/c-index-test:
> hidden symbol `__sync_val_compare_and_swap_4' in
> /home/prasanth/arm-toolchain/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.3/libgcc.a(linux-atomic.o)
> is referenced by DSO
> /home/prasanth/arm-toolchain/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.3/../../../../arm-none-linux-gnueabi/bin/ld:
> final link failed: Nonrepresentable section on output
> collect2: ld returned 1 exit status
> make[4]: ***
> [/home/prasanth/LLVM_ARM/llvm-with-armgcc433/llvm-obj/Release/bin/c-index-test]
> Error 1
> make[4]: Leaving directory
> `/home/prasanth/LLVM_ARM/llvm-with-armgcc433/llvm-obj/tools/clang/tools/c-index-test'
> make[3]: *** [all] Error 1
> make[3]: Leaving directory
> `/home/prasanth/LLVM_ARM/llvm-with-armgcc433/llvm-obj/tools/clang/tools'
> make[2]: *** [all] Error 1
> make[2]: Leaving directory
> `/home/prasanth/LLVM_ARM/llvm-with-armgcc433/llvm-obj/tools/clang'
> make[1]: *** [clang/.makeall] Error 2
> make[1]: Leaving directory
> `/home/prasanth/LLVM_ARM/llvm-with-armgcc433/llvm-obj/tools'
> make: *** [all] Error 1
>
> can anyone please tell me why am i getting this error and how can i
> resolve this?
>
> Thanks and Regards,
> Prasanth J
>
>
You get this linking error because the code contains a gcc atomic
intrinsic calls using __sync_val_compare_and_swap . These are GCC
built-ins and have only been implemented on ARM using GCC 4.4.
http://gcc.gnu.org/onlinedocs/gcc-4.4.2/gcc/Atomic-Builtins.html
If you want to use GCC 4.3.3 then you have to implement the
__sync_val_compare_and_swap_4 function yourself.

Ubuntu Jaunty ARM toolchains have been patched to contains the atomic
intrinsics support in GCC 4.3.3

So to solve this issue do one of the following:
a) update your code sourcery cross compiler to arm-2009q3 that are using
GCC 4.4
b) use the Ubuntu gcc 4.3.3 provided toolchain (i use this when
compiling llvm natively on a arm machine without cross compilation)
c) implement the __sync_val_compare_and_swap_4 function and patch llvm
to enable compilation using older toolchains.

Cheers
Xerxes