[pulseaudio-discuss] webrtc: build failures on i386

[Rex Dieter]

Arun Raghavan wrote:


> Looking at the code, they already do runtime detection, so if you build
> on a machine with SSE2 and intrinsics, you should be okay for this to
> run on any machine with or with SSE2. Example of the code:
> 
>   #if defined(WEBRTC_ARCH_X86_FAMILY)
>     if (WebRtc_GetCPUInfo(kSSE2)) {
>       WebRtcAec_InitAec_SSE2();
>     }
>   #endif

I found at least one place where runtime detection was short-circuited in ./webrtc/common_audio/fir_filter.cc :
(I found FIRFilterSSE2 cannot compile at all if -msse2 isn't enabled (and __SSE2__ isn't defined), at least not with gcc6 on fedora 24)

// If we know the minimum architecture at compile time, avoid CPU detection.
#if defined(WEBRTC_ARCH_X86_FAMILY)
#if defined(__SSE2__)
  filter =
      new FIRFilterSSE2(coefficients, coefficients_length, max_input_length);
#else
  // x86 CPU detection required.
  if (WebRtc_GetCPUInfo(kSSE2)) {
    filter =
        new FIRFilterSSE2(coefficients, coefficients_length, max_input_length);
  } else {
    filter = new FIRFilterC(coefficients, coefficients_length);
  }

I had to patch this to unconditionally follow the #else case on x86, see also:
http://pkgs.fedoraproject.org/cgit/rpms/webrtc-audio-processing.git/tree/webrtc-audio-processing-0.2-x86_sse2_runtime_detection.patch

and related,
http://pkgs.fedoraproject.org/cgit/rpms/webrtc-audio-processing.git/tree/webrtc-audio-processing-0.2-x86_msse2.patch

to force use of -msse2 compiler flag on x86 builds.

-- Rex