compute_activation_c never implemented

There is https://github.com/xiph/opus/blob/3da9f7a6db1c05c3996cb363a9d1931a978bf1be/dnn/nnet.h#L133 in the header, but I can't seem to find the implementation of it anywhere.

compilation without SSE/AVX/NEON also fails for me at linking this function.

> com.android.ide.common.process.ProcessException: ninja: Entering directory `/home/user/src/freerdp/client/Android/Studio/freeRDPCore/.cxx/Debug/38e5t665/armeabi-v7a'
  [1/34] Completed 'openssl'
  [2/34] Performing update step for 'openh264'
  -- Already at requested tag: v2.6.0
  [3/34] Performing patch step for 'openh264'
  Applied patch to 'build/platform-android.mk' cleanly.
  Applied patch to 'Makefile' cleanly.
  [4/34] Performing build step for 'opus'
  FAILED: opus-prefix/src/opus-stamp/opus-build /home/user/src/freerdp/client/Android/Studio/freeRDPCore/.cxx/Debug/38e5t665/armeabi-v7a/opus-prefix/src/opus-stamp/opus-build 
  cd /home/user/src/freerdp/client/Android/Studio/freeRDPCore/.cxx/Debug/38e5t665/armeabi-v7a/opus-prefix/src/opus-build && /opt/Android/Sdk/cmake/4.1.2/bin/cmake --build . && /opt/Android/Sdk/cmake/4.1.2/bin/cmake -E touch /home/user/src/freerdp/client/Android/Studio/freeRDPCore/.cxx/Debug/38e5t665/armeabi-v7a/opus-prefix/src/opus-stamp/opus-build
  [1/1] Linking C shared library libopus.so
  FAILED: libopus.so 
  : && /opt/Android/Sdk/ndk/29.0.13113456/toolchains/llvm/prebuilt/linux-x86_64/bin/clang --target=armv7-none-linux-androideabi29 --sysroot=/opt/Android/Sdk/ndk/29.0.13113456/toolchains/llvm/prebuilt/linux-x86_64/sysroot -fPIC -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -march=armv7-a -mthumb -Wformat -Werror=format-security  -fno-limit-debug-info  -shared -Wl,--build-id=sha1 -Wl,--no-rosegment -Wl,--no-undefined-version -Wl,--fatal-warnings -Wl,--no-undefined -Qunused-arguments  -Xlinker --dependency-file=CMakeFiles/opus.dir/link.d -Wl,-soname,libopus.so -o libopus.so CMakeFiles/opus.dir/src/opus.c.o CMakeFiles/opus.dir/src/opus_decoder.c.o CMakeFiles/opus.dir/src/opus_encoder.c.o CMakeFiles/opus.dir/src/extensions.c.o CMakeFiles/opus.dir/src/opus_multistream.c.o CMakeFiles/opus.dir/src/opus_multistream_encoder.c.o CMakeFiles/opus.dir/src/opus_multistream_decoder.c.o CMakeFiles/opus.dir/src/repacketizer.c.o CMakeFiles/opus.dir/src/opus_projection_encoder.c.o CMakeFiles/opus.dir/src/opus_projection_decoder.c.o CMakeFiles/opus.dir/src/mapping_matrix.c.o CMakeFiles/opus.dir/src/analysis.c.o CMakeFiles/opus.dir/src/mlp.c.o CMakeFiles/opus.dir/src/mlp_data.c.o CMakeFiles/opus.dir/silk/CNG.c.o CMakeFiles/opus.dir/silk/code_signs.c.o CMakeFiles/opus.dir/silk/init_decoder.c.o CMakeFiles/opus.dir/silk/decode_core.c.o CMakeFiles/opus.dir/silk/decode_frame.c.o CMakeFiles/opus.dir/silk/decode_parameters.c.o CMakeFiles/opus.dir/silk/decode_indices.c.o CMakeFiles/opus.dir/silk/decode_pulses.c.o CMakeFiles/opus.dir/silk/decoder_set_fs.c.o CMakeFiles/opus.dir/silk/dec_API.c.o CMakeFiles/opus.dir/silk/enc_API.c.o CMakeFiles/opus.dir/silk/encode_indices.c.o CMakeFiles/opus.dir/silk/encode_pulses.c.o CMakeFiles/opus.dir/silk/gain_quant.c.o CMakeFiles/opus.dir/silk/interpolate.c.o CMakeFiles/opus.dir/silk/LP_variable_cutoff.c.o CMakeFiles/opus.dir/silk/NLSF_decode.c.o CMakeFiles/opus.dir/silk/NSQ.c.o CMakeFiles/opus.dir/silk/NSQ_del_dec.c.o CMakeFiles/opus.dir/silk/PLC.c.o CMakeFiles/opus.dir/silk/shell_coder.c.o CMakeFiles/opus.dir/silk/tables_gain.c.o CMakeFiles/opus.dir/silk/tables_LTP.c.o CMakeFiles/opus.dir/silk/tables_NLSF_CB_NB_MB.c.o CMakeFiles/opus.dir/silk/tables_NLSF_CB_WB.c.o CMakeFiles/opus.dir/silk/tables_other.c.o CMakeFiles/opus.dir/silk/tables_pitch_lag.c.o CMakeFiles/opus.dir/silk/tables_pulses_per_block.c.o CMakeFiles/opus.dir/silk/VAD.c.o CMakeFiles/opus.dir/silk/control_audio_bandwidth.c.o CMakeFiles/opus.dir/silk/quant_LTP_gains.c.o CMakeFiles/opus.dir/silk/VQ_WMat_EC.c.o CMakeFiles/opus.dir/silk/HP_variable_cutoff.c.o CMakeFiles/opus.dir/silk/NLSF_encode.c.o CMakeFiles/opus.dir/silk/NLSF_VQ.c.o CMakeFiles/opus.dir/silk/NLSF_unpack.c.o CMakeFiles/opus.dir/silk/NLSF_del_dec_quant.c.o CMakeFiles/opus.dir/silk/process_NLSFs.c.o CMakeFiles/opus.dir/silk/stereo_LR_to_MS.c.o CMakeFiles/opus.dir/silk/stereo_MS_to_LR.c.o CMakeFiles/opus.dir/silk/check_control_input.c.o CMakeFiles/opus.dir/silk/control_SNR.c.o CMakeFiles/opus.dir/silk/init_encoder.c.o CMakeFiles/opus.dir/silk/control_codec.c.o CMakeFiles/opus.dir/silk/A2NLSF.c.o CMakeFiles/opus.dir/silk/ana_filt_bank_1.c.o CMakeFiles/opus.dir/silk/biquad_alt.c.o CMakeFiles/opus.dir/silk/bwexpander_32.c.o CMakeFiles/opus.dir/silk/bwexpander.c.o CMakeFiles/opus.dir/silk/debug.c.o CMakeFiles/opus.dir/silk/decode_pitch.c.o CMakeFiles/opus.dir/silk/inner_prod_aligned.c.o CMakeFiles/opus.dir/silk/lin2log.c.o CMakeFiles/opus.dir/silk/log2lin.c.o CMakeFiles/opus.dir/silk/LPC_analysis_filter.c.o CMakeFiles/opus.dir/silk/LPC_inv_pred_gain.c.o CMakeFiles/opus.dir/silk/table_LSF_cos.c.o CMakeFiles/opus.dir/silk/NLSF2A.c.o CMakeFiles/opus.dir/silk/NLSF_stabilize.c.o CMakeFiles/opus.dir/silk/NLSF_VQ_weights_laroia.c.o CMakeFiles/opus.dir/silk/pitch_est_tables.c.o CMakeFiles/opus.dir/silk/resampler.c.o CMakeFiles/opus.dir/silk/resampler_down2_3.c.o CMakeFiles/opus.dir/silk/resampler_down2.c.o CMakeFiles/opus.dir/silk/resampler_private_AR2.c.o CMakeFiles/opus.dir/silk/resampler_private_down_FIR.c.o CMakeFiles/opus.dir/silk/resampler_private_IIR_FIR.c.o CMakeFiles/opus.dir/silk/resampler_private_up2_HQ.c.o CMakeFiles/opus.dir/silk/resampler_rom.c.o CMakeFiles/opus.dir/silk/sigm_Q15.c.o CMakeFiles/opus.dir/silk/sort.c.o CMakeFiles/opus.dir/silk/sum_sqr_shift.c.o CMakeFiles/opus.dir/silk/stereo_decode_pred.c.o CMakeFiles/opus.dir/silk/stereo_encode_pred.c.o CMakeFiles/opus.dir/silk/stereo_find_predictor.c.o CMakeFiles/opus.dir/silk/stereo_quant_pred.c.o CMakeFiles/opus.dir/silk/LPC_fit.c.o CMakeFiles/opus.dir/celt/bands.c.o CMakeFiles/opus.dir/celt/celt.c.o CMakeFiles/opus.dir/celt/celt_encoder.c.o CMakeFiles/opus.dir/celt/celt_decoder.c.o CMakeFiles/opus.dir/celt/cwrs.c.o CMakeFiles/opus.dir/celt/entcode.c.o CMakeFiles/opus.dir/celt/entdec.c.o CMakeFiles/opus.dir/celt/entenc.c.o CMakeFiles/opus.dir/celt/kiss_fft.c.o CMakeFiles/opus.dir/celt/laplace.c.o CMakeFiles/opus.dir/celt/mathops.c.o CMakeFiles/opus.dir/celt/mdct.c.o CMakeFiles/opus.dir/celt/modes.c.o CMakeFiles/opus.dir/celt/pitch.c.o CMakeFiles/opus.dir/celt/celt_lpc.c.o CMakeFiles/opus.dir/celt/quant_bands.c.o CMakeFiles/opus.dir/celt/rate.c.o CMakeFiles/opus.dir/celt/vq.c.o CMakeFiles/opus.dir/silk/float/apply_sine_window_FLP.c.o CMakeFiles/opus.dir/silk/float/corrMatrix_FLP.c.o CMakeFiles/opus.dir/silk/float/encode_frame_FLP.c.o CMakeFiles/opus.dir/silk/float/find_LPC_FLP.c.o CMakeFiles/opus.dir/silk/float/find_LTP_FLP.c.o CMakeFiles/opus.dir/silk/float/find_pitch_lags_FLP.c.o CMakeFiles/opus.dir/silk/float/find_pred_coefs_FLP.c.o CMakeFiles/opus.dir/silk/float/LPC_analysis_filter_FLP.c.o CMakeFiles/opus.dir/silk/float/LTP_analysis_filter_FLP.c.o CMakeFiles/opus.dir/silk/float/LTP_scale_ctrl_FLP.c.o CMakeFiles/opus.dir/silk/float/noise_shape_analysis_FLP.c.o CMakeFiles/opus.dir/silk/float/process_gains_FLP.c.o CMakeFiles/opus.dir/silk/float/regularize_correlations_FLP.c.o CMakeFiles/opus.dir/silk/float/residual_energy_FLP.c.o CMakeFiles/opus.dir/silk/float/warped_autocorrelation_FLP.c.o CMakeFiles/opus.dir/silk/float/wrappers_FLP.c.o CMakeFiles/opus.dir/silk/float/autocorrelation_FLP.c.o CMakeFiles/opus.dir/silk/float/burg_modified_FLP.c.o CMakeFiles/opus.dir/silk/float/bwexpander_FLP.c.o CMakeFiles/opus.dir/silk/float/energy_FLP.c.o CMakeFiles/opus.dir/silk/float/inner_product_FLP.c.o CMakeFiles/opus.dir/silk/float/k2a_FLP.c.o CMakeFiles/opus.dir/silk/float/LPC_inv_pred_gain_FLP.c.o CMakeFiles/opus.dir/silk/float/pitch_analysis_core_FLP.c.o CMakeFiles/opus.dir/silk/float/scale_copy_vector_FLP.c.o CMakeFiles/opus.dir/silk/float/scale_vector_FLP.c.o CMakeFiles/opus.dir/silk/float/schur_FLP.c.o CMakeFiles/opus.dir/silk/float/sort_FLP.c.o CMakeFiles/opus.dir/celt/arm/armcpu.c.o CMakeFiles/opus.dir/celt/arm/arm_celt_map.c.o CMakeFiles/opus.dir/silk/arm/arm_silk_map.c.o CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o CMakeFiles/opus.dir/celt/arm/celt_neon_intr.c.o CMakeFiles/opus.dir/celt/arm/pitch_neon_intr.c.o CMakeFiles/opus.dir/silk/arm/biquad_alt_neon_intr.c.o CMakeFiles/opus.dir/silk/arm/LPC_inv_pred_gain_neon_intr.c.o CMakeFiles/opus.dir/silk/arm/NSQ_del_dec_neon_intr.c.o CMakeFiles/opus.dir/silk/arm/NSQ_neon.c.o  -lm  -latomic -lm && :
  ld.lld: error: undefined symbol: compute_activation_c
  >>> referenced by arm_dnn_map.c:55 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:55)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_ACTIVATION_IMPL)
  >>> referenced by arm_dnn_map.c:55 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:55)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_ACTIVATION_IMPL)
  >>> referenced by arm_dnn_map.c:55 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:55)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_ACTIVATION_IMPL)
  
  ld.lld: error: undefined symbol: compute_activation_neon
  >>> referenced by arm_dnn_map.c:55 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:55)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_ACTIVATION_IMPL)
  >>> referenced by arm_dnn_map.c:55 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:55)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_ACTIVATION_IMPL)
  
  ld.lld: error: undefined symbol: compute_conv2d_c
  >>> referenced by arm_dnn_map.c:68 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:68)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_CONV2D_IMPL)
  >>> referenced by arm_dnn_map.c:68 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:68)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_CONV2D_IMPL)
  >>> referenced by arm_dnn_map.c:68 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:68)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_CONV2D_IMPL)
  
  ld.lld: error: undefined symbol: compute_conv2d_neon
  >>> referenced by arm_dnn_map.c:68 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:68)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_CONV2D_IMPL)
  >>> referenced by arm_dnn_map.c:68 (/home/user/src/freerdp/client/Android/Studio/freeRDPCore/src/main/cpp/external/opus/dnn/arm/arm_dnn_map.c:68)
  >>>               CMakeFiles/opus.dir/dnn/arm/arm_dnn_map.c.o:(DNN_COMPUTE_CONV2D_IMPL)
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  ninja: build stopped: subcommand failed.
  [5/34] Performing configure step for 'openh264'
  ninja: build stopped: subcommand failed.

Start with the compute_activation_c declaration in dnn/nnet.h and the dispatch references in dnn/arm/arm_dnn_map.c. Reproduce a build without SSE, AVX, and NEON, then trace which implementations are included in that configuration. Done means the affected configuration links successfully without undefined DNN symbols.