swift : improvements and fixes

[jhen0409]

Some small improvements and fixes:

• We currently used int64_t in Metal, so we should use macOS 12 as minimum requirement (macOS v12 platform is defined in swift-tools-version:5.5)
• Add -O3 -DNDEBUG unsafe flags as we already did in the makefile (context: comments in fixed bad memory access exception on ios 17 #3527)
• Add missing ggml-backend.c source for fix build, but I'll remove it in this PR if fix swift package + add example swift implementation of batched api #3562 get merged first

[zshannon]

👍 was just coming here to ask about -O3 flag

[l3utterfly]

I tried adding this before on my branch before, but after this change, I am unable to link it to a production iOS app. The error is: swift package cannot be used as a dependency because it contains unsafe build flags

So this change will stop this package from being used in production apps.

(Not sure if I'm doing something wrong)

[zshannon]

There's something wonky with Xcode (surprise surprise) and SPM here where it throws that error if you're not pinned to a commit sha IIRC, could that be going on in your project config?

(The latest code doesn't work without -O3 so it's not like removing the flag is an option)

[l3utterfly]

Huh, I'm pretty new to XCode so didn't know that. Can you give me an example on how to solve this by pinning it to a commit?

I'm using CMake for the time being.

[jhen0409]

@l3utterfly, In my remember this only happened if use local package, -fno-objc-arc and other flags will also cause this problem even if no -O3.

If you're using remote repository, set commit or version will be best practice, this can be done in Project -> Package Dependencies. However, even if I set master branch, I'm not able to get the error.

[l3utterfly]

ah ok, I was using local packages. Thanks.

@jhen0409 were you able to test if this is still happening after enabling -O3? #3527

Your last EDIT said llama_save_session_file still has an issue.

[jhen0409]

@jhen0409 were you able to test if this is still happening after enabling -O3? #3527

Your last EDIT said llama_save_session_file still has an issue.

I think llama_save_session_file is still broken with O3, currently I use it in main queue as a workaround.

[ggerganov]

Should be fixed on master via b8fe4b5