Gracefully exit when the minimum instructions set is not found about highway HOT 4 CLOSED

Hi, thanks for reporting this! The intention is definitely to gracefully fall back to a generic fallback implementation.

The HWY_SCALAR fallback might be disabled if we compile with say -msse4 (targets.h could then consider HWY_SCALAR superseded and only generate sse4, which would crash when run on an old enough CPU). Our CMake file does not specify such a flag, though.

It's also possible that the builtin_trap in hwy::Abort (called when a test fails) would manifest as SIGILL, but it's surprising that we do not see any other output if that were the case.

Any chance you could run this in a debugger to see where exactly this is happening?

FYI tests/hwy_test has moved to highway_test in 0.12.0.

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Sadly I can't test it myself as I don't have an old system laying around. It was reported to me by another user.
Could setting DHWY_COMPILE_ALL_ATTAINABLE help?

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Could setting DHWY_COMPILE_ALL_ATTAINABLE help?

Yes, that would prevent disabling the fallback, if that is indeed the problem.

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This has been worked out downstream with bug reviewer.

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