--enable-neon flag for fftw

[tangjinchuan]

brew gist-logs <formula> link OR brew config AND brew doctor output

a2@A2deMacBook-Pro ~ % brew config        
HOMEBREW_VERSION: 4.3.1
ORIGIN: https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git
HEAD: e0bc557e7b991cb23583679e1cf1c8a92b793aeb
Last commit: 5 days ago
Core tap JSON: 25 May 09:16 UTC
Core cask tap JSON: 25 May 09:16 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_API_DOMAIN: https://mirrors.tuna.tsinghua.edu.cn/homebrew-bottles/api
HOMEBREW_BREW_GIT_REMOTE: https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git
HOMEBREW_CASK_OPTS: []
HOMEBREW_CORE_GIT_REMOTE: https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/homebrew-core.git
HOMEBREW_MAKE_JOBS: 12
Homebrew Ruby: 3.3.1 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/3.3.1/bin/ruby
CPU: dodeca-core 64-bit arm_blizzard_avalanche
Clang: 15.0.0 build 1500
Git: 2.39.3 => /Library/Developer/CommandLineTools/usr/bin/git
Curl: 8.4.0 => /usr/bin/curl
macOS: 14.4.1-arm64
CLT: 15.3.0.0.1.1708646388
Xcode: N/A
Rosetta 2: false
a2@A2deMacBook-Pro ~ %

Verification

• My brew doctor output says Your system is ready to brew. and am still able to reproduce my issue.
• I ran brew update and am still able to reproduce my issue.
• I have resolved all warnings from brew doctor and that did not fix my problem.
• I searched for recent similar issues at https://github.com/Homebrew/homebrew-core/issues?q=is%3Aissue and found no duplicates.

What were you trying to do (and why)?

I was looking at the rb file for fftw, and I could not find any sign of neon extension for Apple Silicon CPU. It would be desirable to enable this extension so that GNU octave can have a better performance while doing FFT.
https://github.com/Homebrew/homebrew-core/blob/e84fce57d1e9a2b44bfba8ee5a289ce4665f827f/Formula/f/fftw.rb
The way to enable Neon is here. http://fftw.org/fftw3_doc/Installation-on-Unix.html

What happened (include all command output)?

version -fftw
ans = fftw-3.3.10

What did you expect to happen?

For Intel based system it would produce a string based on the supported extensions. However, I don't know if the same applies to Apple Silicon with Homebrew.

version -fftw
ans = fftw-3.3.10-sse2-avx-avx2-avx2_128-avx512

Step-by-step reproduction instructions (by running brew commands)

I would like to know if Neon is enabled for fftw so that it can be used by GNU octave.

[SMillerDev]

Please make a pull request to request changes to formula.