build error on mac osx

[Matthias Kretz]

Hi Tijskens,

welcome to the list! :)

On Friday 17 January 2014 12:42:45 Tijskens Engelbert wrote:
> /Users/etijskens/Downloads/vc-vc/avx/intrinsics.h:582:5: error: use of
> undeclared identifier '_mm_comlt_epu32' AVX_TO_SSE_2(comlt_epu32)
>     ^
> (Similar errors from the three succeeding lines as well)
> I checked the CMake files for any variables that could solve the problem. 
> As suggested in the documentation (portability issues/compiler flags) I
> added CMAKE_CXX_FLAGS -march=corei7-avx -mavx
> 
> The errors go away when i #undef VC_IMPL_XOP just before
> /Users/etijskens/Downloads/vc-vc/avx/intrinsics.h:581
> 
> As far as i know XOP is for AMD cpus and should not be activated in my
> build. CMake  detects TARGET_ARCHITECTURE=ivy-bridge
> 
> i am compiling on a machine with Intel® Core™ i7-3615QM Processor and Mac OS
> X (maverick) using the clang 5.0 compiler. I am not sure that
> a) the problem is correctly solved by undefining VC_IMPL_XOP
> b) there is not a more elegant solution

I never can remember the mapping of Apples clang version to the actual clang 
version. The latest released version of clang is 3.4 
(http://llvm.org/releases/download.html). I think clang --version should print 
the actual version somewhere.

In any case, you are right that your system doesn't need the XOP stuff. The 
XOP code is compiled because the libVc library is supposed to work for any 
target system. Thus you can build build applications for different hosts on 
your machine without having to recompile libVc. But if your compiler doesn't 
do XOP anyway then this feature is moot. So disabling XOP support is the right 
way to go.

We have two options to fix this:
a) quick: call set(Vc_XOP_INTRINSICS_BROKEN true) in cmake/VcMacros.cmake for 
depending on the clang version on Apple systems
b) more generic: make the -mxop compiler flag check more thorough. Right now 
it only tests whether the compiler barfs with the flag. But it doesn't check 
that with -mxop it also supports the XOP intrinsics. There's a similar check 
in cmake/AddCompilerFlag.cmake for -mfma already. Should be easy to copy and 
adjust.

Cheers,
Matthias

-- 
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 Dipl.-Phys. Matthias Kretz

 Web:   http://compeng.uni-frankfurt.de/?mkretz

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