Sadly even SSE vs. AVX is enough to often give different results, as SSE doesn't have support for fused multiply-add instructions which allow calculation of a*b + c with guaranteed correct rounding. Even though this should allow CPUs from 2013 and later to all use FMA, gcc/clang don't enable AVX by default for the x86-64 targets. And even if they did, results are only guaranteed identical if implementations have chosen the exact same polynomial approximation method and no compiler optimizations alter the instruction sequence.
Unfortunately, floating point results will probably continue to differ across platforms for the foreseeable future.
Unfortunately, floating point results will probably continue to differ across platforms for the foreseeable future.