test_nvvm.py changes for compatibility with CTK 11.8

[rwgk]

Resolve compatibility problems discovered while backporting PR #421 to the 11.8.x branch.

The NVVM IR major & debug_major version numbers in MINIMAL_NVVMIR_TXT in test_nvvm.py need to match the version numbers in the libnvvm.so being used.

For CTK 11.8 the libnvvm.so IR major & debug_major versions numbers are 1 and 3, respectively.

For CTK 12.x the libnvvm.so IR major & debug_major versions numbers are 2 and 3, respectively.

This is easily accommodated for MINIMAL_NVVMIR_TXT, but generating MINIMAL_NVVMIR_BITCODE requires a tool for converting NVVM IR text to bitcode.

If llvmlite is available the conversion is actually very simple:

            bitcode_dynamic = llvmlite_binding.parse_assembly(txt.decode()).as_bitcode()

However, we decided it is best to not make llvmlite a hard dependency for testing. To this end, a dictionary with bitcode inputs in binascii format is introduced, keyed by NVVM IR major & debug_major version numbers, e.g.:

MINIMAL_NVVMIR_BITCODE_STATIC = {
    (1, 3):  # (major, debug_major)
    "4243c0de3514000005000000620c30244a59be669dfbb4bf0b51804c01000000210c00007f010000"
    ...
    "00000000",
    (2, 3):  # (major, debug_major)
    "4243c0de3514000005000000620c30244a59be669dfbb4bf0b51804c01000000210c000080010000"
    ....
    "6e673e0000000000",
}

Now we have a total of four combinations of situations:

• llvmlite available yes/no

• MINIMAL_NVVMIR_BITCODE_STATIC entry available yes/no

1. If both are not available (e.g. for a new CTK version) test_nvvm.py will fail:

                raise RuntimeError("Please `pip install llvmlite` to generate `bitcode_static` (see PR #443)")

2. If only llvmlite is available, running test_nvvm.py will generate the missing entry for MINIMAL_NVVMIR_BITCODE_STATIC, correctly formatted for pasting into test_nvvm.py, and bitcode_static testing will simply be skipped.

                pytest.skip(f"UNAVAILABLE: {request.param}")

3. If only the MINIMAL_NVVMIR_BITCODE_STATIC entry is available, bitcode_dynamic testing will simply be skipped. This is assumed to be the routine situation.

4. If both llvmlite and the MINIMAL_NVVMIR_BITCODE_STATIC entry are available, testing will run with both independently.

With this setup it is expected to be very easy to keep up with new CTK versions. llvmlite is needed only when testing with a new CTK version for the first time, to generate the new MINIMAL_NVVMIR_BITCODE_STATIC entry.

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[rwgk]

/ok to test

[rwgk]

/ok to test

[rwgk]

Hi @leofang, this is ready for merging. I didn't re-run the tests after the last commit c8d0842 because that only changes comments. Testing before was successful for both PRs (this one and #442).

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[leofang]

/ok to test

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