Compiling Issues when using Xmmintrin.h

[Jonathan Esteban]

Hi all,

I'm trying to compile a file using this command:

$em++ -g -I src/lib/ -I boost src/lib/pke/multiparty.cpp -v

However, I am getting this error:

In file included from src/lib/pke/multiparty.cpp:7:                                                              

In file included from src/lib/pke/multiparty.h:10:                                                               

In file included from src/lib/Common/Defines.h:9:                                                                

In file included from /home/user/emsdk/fastcomp/fastcomp/lib/clang/6.0.1/include/emmintrin.h:27:      

In file included from /home/user/emsdk/fastcomp/fastcomp/lib/clang/6.0.1/include/xmmintrin.h:27:      

/home/user/emsdk/fastcomp/fastcomp/lib/clang/6.0.1/include/mmintrin.h:47:5: error: use of undeclared  

      identifier '__builtin_ia32_emms'; did you mean '__builtin_isless'?                                         

    __builtin_ia32_emms();

When I compile using g++ I get no error. I think g++ is using another source for its emmintrin.h. I need to use emmintrin.h as it is used in Defines.h through:

#include <emmintrin.h>

Any thoughts? I'm at a loss of ideas and I'm very new to Emscripten and building projects in general. Let me know if you need more debugging info.

Thanks!

[Thomas Lively]

Hi, using native SIMD intrinsics is not supported with WebAssembly because emulating native SIMD via WebAssembly SIMD will lead to unexpected slowdowns. See this recent thread for more details: https://groups.google.com/forum/#!msg/emscripten-discuss/bp_iubXU3BE/vI4opCduCQAJ and see https://emscripten.org/docs/porting/simd.html#porting-simd-code-targeting-webassembly for more information on using WebAssembly's SIMD.

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[Jonathan Esteban]

Thanks for the prompt reply! I've read through the links you provided. What I'm getting at is that there's no way to compile code that uses SIMD intrinsics? (i.e. emmintrin.h)  

[Thomas Lively]

That's right. Those particular intrinsics are specific to x86 platforms. You can use the WebAssembly SIMD intrinsics from https://github.com/emscripten-core/emscripten/blob/incoming/system/include/wasm_simd128.h instead, though.

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[Jonathan Esteban]

Okay, so I'll try replacing the intrinsics we are using with the ones WebAssembly supports. I swapped #include <emmintrin.h> with #include <wasm_simd128.h>

and added the flag -msimd128

so now I'm running:

em++ -msimd128 -g -I src/lib/ -I boost src/lib/pke/multiparty.cpp -v

But I'm getting the following errors:

In file included from src/lib/pke/multiparty.cpp:7:                                                              

In file included from src/lib/pke/multiparty.h:10:                                                               

In file included from src/lib/Common/Defines.h:9:                                                                

/home/jonathanesteban/emsdk/fastcomp/emscripten/system/include/wasm_simd128.h:482:18: error: use of undeclared   

      identifier '__builtin_wasm_bitselect'                                                                      

  return (v128_t)__builtin_wasm_bitselect((__i32x4)a, (__i32x4)b, (__i32x4)mask);                                

                 ^                                                                                               

/home/jonathanesteban/emsdk/fastcomp/emscripten/system/include/wasm_simd128.h:492:10: error: use of undeclared   

      identifier '__builtin_wasm_any_true_i8x16'                                                                 

  return __builtin_wasm_any_true_i8x16((__i8x16)a);  

Any idea of why this is happening?

Thanks

[Thomas Lively]

Yes, it looks like you're using the old fastcomp backend, but SIMD and other post-MVP WebAssembly features are only supported with the new LLVM backend. If you're using the emsdk, you can try installing and activating the `latest-upstream` tag instead of just `latest`.

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[Jonathan Esteban]

Awesome, thank you so much!