arm_acle.h compiler errors when building for iOS with Xcode 15.3

[geertbleyen]

arm_acle.h compiler errors when building for iOS with Xcode 15.3

[ebiggers]

It looks like the problem is that for a couple weeks in the llvm-project development branch, arm64 crc intrinsics did not work unless crc support was enabled in the whole file, and Apple happened to fork LLVM during that time and release it starting sometime in the Xcode 15 series. (It's after llvm/llvm-project@b2d7a0d but before llvm/llvm-project@30b67c6.)

The "fix" is likely going to be to disable the use of crc instructions on those versions of Xcode, which will make it compile but will reduce CRC-32 performance. It may be a good idea to use a different version of Xcode so that your build of libdeflate can use these instructions. Note that this problem will go away in future versions of Xcode due to the incorporation of llvm/llvm-project@30b67c6, so it's likely just going to be a few versions in the 15.x series that will be affected.

[geertbleyen]

Thanks for the detailed information! The projects where we need to do these compiles don't have a hard dependency on Xcode versions above 15.0.1, so we can stick with that version for now.

[ebiggers]

3b766cd fixed this by using a fallback to inline assembly. You should be able to use the latest Xcode now. I don't have a way to easily test different Xcode versions, so let me know if it still doesn't work for some reason. Thanks!

[geertbleyen]

@ebiggers , I can confirm this issues has been solved in 3b766cd for Xcode 15.3 (I haven't tested 15.1. or 15.2).
Much appreciated!