The i586 targets on x86 are defined to be 32-bit and lacking in sse/sse2 unlike
the i686 target which has sse2 turned on by default. I was mostly curious what
would happen when turning on this target, and it turns out quite a few tests
failed!
Most of the tests here had to do with calling functions with ABI mismatches
where the callee wasn't `#[inline(always)]`. Various pieces have been updated
now and we should be passing all tests.
Only one instruction assertion ended up changing where the function generates a
different instruction with sse2 ambiently enabled and without it enabled.