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compiling 256 bit vector datatype (__m256d) from Intel's AVX extension with gcc7 or clang fails. I am able to compile and use 128 bit vectors (without -mavx flag). But as soon as I try the avx vectors either some assembler command definitions are not found (GCC7) or there is a linker error (clang). I use port to install all compilers or packages.

The program:

#include <iostream>
#include <emmintrin.h>
#include <immintrin.h>
#include <pmmintrin.h>
#include <xmmintrin.h>

struct cpx256 {
    union {
        struct {
            double r1, i1, r2, i2;
        };
        __m256d v;
    };
    cpx256(double r1_in, double i1_in, double r2_in, double i2_in) :
        r1(r1_in), i1(i1_in), r2(r2_in), i2(i2_in){}
};

 std::ostream & operator<< (std::ostream & os, cpx256 cmplx) {
     os << cmplx.r1;
     (cmplx.i1 > 0) ? (os << "+" << cmplx.i1 << "j") : (os << cmplx.i1 << "j");
     os << " | ";
     os << cmplx.r2;
     (cmplx.i2 > 0) ? (os << "+" << cmplx.i2 << "j") : (os << cmplx.i2 << "j");
     return os;
 }

int main(){
    cpx256 b = cpx256(1,2, 3, 4);
    std::cout << b << std::endl;
    return 0;
}

with gcc7:

g++ -std=c++11 -Wall -Wextra -mtune=native -ffast-math -fverbose-asm -mavx avx.cpp
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:57:no such instruction: `vmovsd %xmm0, -16(%rbp)'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:58:no such instruction: `vmovsd %xmm1, -24(%rbp)'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:59:no such instruction: `vmovsd %xmm2, -32(%rbp)'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:60:no such instruction: `vmovsd %xmm3, -40(%rbp)'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:63:no such instruction: `vmovsd -16(%rbp), %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:64:no such instruction: `vmovsd %xmm0, (%rax)'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:66:no such instruction: `vmovsd -24(%rbp), %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:67:no such instruction: `vmovsd %xmm0, 8(%rax)'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:69:no such instruction: `vmovsd -32(%rbp), %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:70:no such instruction: `vmovsd %xmm0, 16(%rax)'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:72:no such instruction: `vmovsd -40(%rbp), %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:73:no such instruction: `vmovsd %xmm0, 24(%rax)'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:99:no such instruction: `vmovd %rdx, %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:103:no such instruction: `vmovsd 24(%rbp), %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:104:no such instruction: `vxorpd %xmm1, %xmm1,%xmm1'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:105:no such instruction: `vcomisd %xmm1, %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:113:no such instruction: `vmovd %rax, %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:123:no such instruction: `vmovd %rdx, %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:138:no such instruction: `vmovd %rdx, %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:142:no such instruction: `vmovsd 40(%rbp), %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:143:no such instruction: `vxorpd %xmm1, %xmm1,%xmm1'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:144:no such instruction: `vcomisd %xmm1, %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:152:no such instruction: `vmovd %rax, %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:162:no such instruction: `vmovd %rdx, %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:190:no such instruction: `vmovsd lC4(%rip), %xmm2'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:191:no such instruction: `vmovsd lC5(%rip), %xmm1'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:192:no such instruction: `vmovsd lC6(%rip), %xmm0'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:195:no such instruction: `vmovapd %xmm2, %xmm3'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:196:no such instruction: `vmovapd %xmm1, %xmm2'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:197:no such instruction: `vmovapd %xmm0, %xmm1'
/var/folders/06/hdqdxlh14czcvkk4t55894y80000gn/T//ccXFPOnA.s:198:no such instruction: `vmovd %rdx, %xmm0'

with clang I get a linker error:

clang -std=c++11 -Wall -Wextra -mtune=native -ffast-math -fverbose-asm -mavx avx.cpp
Undefined symbols for architecture x86_64:
  "std::__1::__basic_string_common<true>::__throw_length_error() const", referenced from:
      std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> > std::__1::__pad_and_output<char, std::__1::char_traits<char> >(std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> >, char const*, char const*, char const*, std::__1::ios_base&, char) in avx-dfd779.o
  "std::__1::locale::use_facet(std::__1::locale::id&) const", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in avx-dfd779.o
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
  "std::__1::ios_base::getloc() const", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in avx-dfd779.o
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::~basic_string()", referenced from:
      std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> > std::__1::__pad_and_output<char, std::__1::char_traits<char> >(std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> >, char const*, char const*, char const*, std::__1::ios_base&, char) in avx-dfd779.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::put(char)", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in avx-dfd779.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::flush()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in avx-dfd779.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::sentry::sentry(std::__1::basic_ostream<char, std::__1::char_traits<char> >&)", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::sentry::~sentry()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::operator<<(double)", referenced from:
      operator<<(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, cpx256) in avx-dfd779.o
  "std::__1::cout", referenced from:
      _main in avx-dfd779.o
  "std::__1::ctype<char>::id", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in avx-dfd779.o
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
  "std::__1::locale::~locale()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in avx-dfd779.o
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
  "std::__1::ios_base::__set_badbit_and_consider_rethrow()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
  "std::__1::ios_base::clear(unsigned int)", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
  "std::terminate()", referenced from:
      ___clang_call_terminate in avx-dfd779.o
  "operator new(unsigned long)", referenced from:
      std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> > std::__1::__pad_and_output<char, std::__1::char_traits<char> >(std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> >, char const*, char const*, char const*, std::__1::ios_base&, char) in avx-dfd779.o
  "___cxa_begin_catch", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
      ___clang_call_terminate in avx-dfd779.o
  "___cxa_end_catch", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
  "___gxx_personality_v0", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in avx-dfd779.o
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in avx-dfd779.o
      std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> > std::__1::__pad_and_output<char, std::__1::char_traits<char> >(std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> >, char const*, char const*, char const*, std::__1::ios_base&, char) in avx-dfd779.o
      Dwarf Exception Unwind Info (__eh_frame) in avx-dfd779.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

CLang: 

clang version 4.0.1 (tags/RELEASE_401/final)
Target: x86_64-apple-darwin16.6.0
Thread model: posix
InstalledDir: /opt/local/libexec/llvm-4.0/bin

GCC7: 

g++ (MacPorts gcc7 7-20170622_0) 7.1.1 20170622

My Laptop CPU: 2,8 GHz Intel Core i7 (should support AVX), Mac OS Sierra 10.12.5

I also update my linker with port (ld64-latest 274.2) and installed and activated mp-clang-4.0. Any ideas?

Marie Hoffmann
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  • Your code compiles and links without problem using the normal Apple version of clang that comes with Xcode. It looks like your homebrew compiler installs are broken ? – Paul R Oct 16 '17 at 16:48
  • Check what assembler version you're using. If `vmovd %rdx, %xmm0` doesn't assemble, your setup is really broken. – Peter Cordes Oct 17 '17 at 05:08
  • clang seems to use version 8.1.0. But I mostly use the GNU compiler collection. I do not know how to check which version it takes, if it's possible at all that it takes a different one. `llvm-gcc -v Apple LLVM version 8.1.0 (clang-802.0.42) Target: x86_64-apple-darwin16.6.0 Thread model: posix InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin` – Marie Hoffmann Oct 17 '17 at 13:12
  • Use `g++ -v -O2 -march=native foo.cpp`. The `-v` will show the commands the front-end runs, including the assembler. (So you can see what path it's using to run the assembler.) IIRC the assembler will also print its version. – Peter Cordes Oct 17 '17 at 14:21

1 Answers1

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Meanwhile I checked the clang call again and found that very stupid mistake calling the C and not the C++ compiler. So this minimal call compiles and executes without errors:

clang++ -std=c++11 -mavx ../tests/sse_tests.cpp

However for the gcc++ version the assembler seems not to be linked correctly and I have no idea how to check this.

Marie Hoffmann
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