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Assembly Coverage

Last updated: 2026-03-14

gopus ships assembly only for helpers that stay bit-exact against the pure-Go path.

Selection Model

  • arm64: assembly is selected automatically by GOARCH=arm64.
  • amd64: two helper groups exist:
    • imdct_rotate and kf_bfly use baseline amd64 assembly through the normal *_asm.go wrappers.
    • the wider CELT math helpers use runtime dispatch in celt/amd64_dispatch.go, guarded by internal/cpufeat/amd64.go.
  • Runtime dispatch enables the AVX2+FMA helpers only when the host OS and CPU report both features. Otherwise the generic Go path is used.
  • Non-amd64/arm64 targets use the pure-Go fallbacks.

This means the AVX/FMA paths are not selected purely at compile time. GOAMD64=v3 is not required for the current production dispatch.

CELT Kernels

arm64 kernels:

  • celt/abs_sum_arm64.s
  • celt/exp_rotation_arm64.s
  • celt/float32_arm64.s
  • celt/haar1_arm64.s
  • celt/imdct_rotate_arm64.s
  • celt/kf_bfly5n1_arm64.s
  • celt/kf_bfly_arm64.s
  • celt/pitch_autocorr_arm64.s
  • celt/pitch_xcorr_arm64.s
  • celt/prefilter_innerprod_arm64.s
  • celt/prefilter_xcorr_arm64.s
  • celt/pvq_search_arm64.s
  • celt/stereo_layout_arm64.s
  • celt/tone_lpc_corr_arm64.s
  • celt/transient_energy_arm64.s

amd64 baseline kernels:

  • celt/imdct_rotate_amd64.s
  • celt/kf_bfly_amd64.s

amd64 runtime-dispatched AVX2/FMA kernels:

  • celt/abs_sum_amd64.s
  • celt/exp_rotation_amd64.s
  • celt/float32_amd64.s
  • celt/pitch_autocorr_amd64.s
  • celt/pitch_xcorr_amd64.s
  • celt/prefilter_innerprod_amd64.s
  • celt/prefilter_xcorr_amd64.s
  • celt/pvq_search_amd64.s
  • celt/tone_lpc_corr_amd64.s
  • celt/transient_energy_amd64.s

SILK Kernels

arm64 kernels:

  • silk/inner_prod_arm64.s
  • silk/pitch_xcorr_arm64.s

There is currently no shipped SILK amd64 assembly.

Pure-Go Fallbacks

Representative fallback files for the assembly-backed helpers:

  • celt/abs_sum_default.go
  • celt/exp_rotation_default.go
  • celt/float32_default.go
  • celt/haar1.go, celt/haar1_nonarm64.go
  • celt/imdct_rotate_default.go
  • celt/kf_bfly_default.go
  • celt/kf_bfly5n1.go, celt/kf_bfly5n1_nonarm64.go
  • celt/pitch_autocorr_default.go
  • celt/pitch_xcorr_default.go
  • celt/prefilter_innerprod_default.go
  • celt/prefilter_xcorr_default.go, celt/prefilter_xcorr_fast_default.go
  • celt/pvq_search_default.go
  • celt/stereo_layout_impl.go
  • celt/tone_lpc_corr_default.go
  • celt/transient_energy_default.go
  • silk/inner_prod_default.go
  • silk/pitch_xcorr_impl_default.go

Validation

go test ./celt ./silk -count=1
GOARCH=amd64 GOAMD64=v1 go test ./celt -run '^TestAMD64DispatchMatchesGeneric$' -count=1
GOARCH=amd64 GOAMD64=v1 go test ./celt -count=1
make verify-production
make bench-guard

When assembly behavior is uncertain, confirm parity against the pinned libopus tree in tmp_check/opus-1.6.1/ before tuning.
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