[Bug]: clang-18 / NDK 27 Compilation hangs / Runs out of memory when using SIMD __ext_vector_type__(3) short

[fil-spatial]

Description

With any clang-18 version shipped with any of the NDK 27.* publicly versions the following SIMD code hangs indefinitely.

More specifically:
With any NDK 27 version and:

• target armv8
• SIMD vector of size 3
• SIMD vector of type short
• compilation not optimised (-O0)

the following SIMD code hangs indefinitely and possibly runs out of memory (exit 137)

typedef __attribute__((__ext_vector_type__(3))) short vector_short3;

void func()
{
    vector_short3 result;
    result.x = short(1);
}

This can be also verified in godbolt here: https://godbolt.org/z/48fdKoEon

Note: it is enough to change any of the pre-condition above to have the compilation to complete successfully.
So to say it is very a nit (yet annoying) case.

Assuming a strict requirements for NDK27, it would be great if you could recommend the workaround with the best tradeoff between the followings - or recommend better.

• just use normal vector/struct of short for 3 dimensional vectors
• just use int instead of short for the vector
• Compile all objs relying on this type with at least -O1 also for debug builds

Upstream bug

llvm/llvm-project#156836

Commit to cherry-pick

No response

I am using a supported NDK

• I have checked and the NDK I'm using is currently supported

Affected versions

r27

Host OS

Mac, Linux

Host OS version

All versions

Affected ABIs

arm64-v8a