Question - how to build for Android arm64-v8

Hello,

I'm trying to compile Opus for Android arm64 (and ultimately other arch's) using the CMakeLists.txt file available in the repository.

My cmake commands are like this:

https://gist.github.com/kvasilye/9004332a5f3f90f2a6e868090d004d7b

This produces an error:

ld: error: undefined symbol: celt_pitch_xcorr_neon
>>> referenced by pitch.c:347 (/home/[ANT.AMAZON.COM/kvasilye/opus/celt/pitch.c:347](http://ant.amazon.com/kvasilye/opus/celt/pitch.c:347))
>>>               CMakeFiles/opus.dir/celt/pitch.c.o:(pitch_search)
>>> referenced by celt_lpc.c:314 (/home/[ANT.AMAZON.COM/kvasilye/opus/celt/celt_lpc.c:314](http://ant.amazon.com/kvasilye/opus/celt/celt_lpc.c:314))
>>>               CMakeFiles/opus.dir/celt/celt_lpc.c.o:(_celt_autocorr)
>>> referenced by burg_modified_FIX.c:98 (/home/[ANT.AMAZON.COM/kvasilye/opus/silk/fixed/burg_modified_FIX.c:98](http://ant.amazon.com/kvasilye/opus/silk/fixed/burg_modified_FIX.c:98))
>>>               CMakeFiles/opus.dir/silk/fixed/burg_modified_FIX.c.o:(silk_burg_modified_c)
>>> referenced 2 more times

Next, I tried to write my own CMakeLists.txt and got stuck too - the undefined symbol above is defined in celt_pitch_xcorr_arm.s which as I understand uses ARM assembler syntax.

I converted the file to GNU syntax using the provided Perl script.

Trying to compile the output with aarch64-linux-gnu-as gives a whole bunch of errors like:

third_party/cmake-build-opus-android-arm64-v8a-Debug/celt_pitch_xcorr_arm_gnu.S: Assembler messages:
third_party/cmake-build-opus-android-arm64-v8a-Debug/celt_pitch_xcorr_arm_gnu.S:1: Error: unknown pseudo-op: `.syntax'
third_party/cmake-build-opus-android-arm64-v8a-Debug/celt_pitch_xcorr_arm_gnu.S:2: Error: junk at end of line, first unrecognized character is `@'
third_party/cmake-build-opus-android-arm64-v8a-Debug/celt_pitch_xcorr_arm_gnu.S:3: Error: junk at end of line, first unrecognized character is `@'
third_party/cmake-build-opus-android-arm64-v8a-Debug/celt_pitch_xcorr_arm_gnu.S:4: Error: junk at end of line, first unrecognized character is `@'
third_party/cmake-build-opus-android-arm64-v8a-Debug/celt_pitch_xcorr_arm_gnu.S:5: Error: junk at end of line, first unrecognized character is `@'

So it looks unhappy with the syntax.

Questions:

1 - What is the right way to compile Opus for Android on arm64-v8a?

2 - If I wanted to compile the asm file, how can I do that?

3 - Is this asm file for both armeabi-v7a and arm64-v8a or just for armeabi-v7a? The symbol is required for arm64-v8a, but there is a directive ".arch armv7-a" at the top of the file so I'm confused.

I really don't know anything about arm assembly to figure these out on my own, any help would be appreciated!

PS - I am able to compile the generated GNU .S file using arm-linux-gnueabi-as on Linux or armv7a-linux-androideabi21-clang which is included in the Android SDK. But that again is for arm7 - and the symbol is missing for arm64-v8a.

Start with the repository's CMakeLists.txt and the celt_pitch_xcorr_arm.s source, then review the provided Perl conversion script and the Android arm64-v8a commands in the issue. Reproduce the undefined-symbol and assembler errors; done means identifying a reproducible arm64-v8a build path and clarifying which assembly source and syntax apply to each ARM target.