It really doesn't feel like it was that long ago when AMD introduced its own SIMD extensions called 3DNow!, but it's been long enough now that the chip company is sending the technology out to pasture.
AMD announced last week that 3DNow! is deprecated and will not be supported in certain upcoming AMD processors and will not have that feature flag bit set.
What does this mean for those who make software using these AMD instructions?
If your software used 3DNow! instructions at any point in time you should confirm that you only take that code path after checking to see if the feature is supported during runtime, using CPUID.
Most likely, your code already has another code path to take, such as an SSE path, if 3DNow! instructions are not supported. To reiterate, make sure that the code uses feature bits to determine when the code should take this path. If the code uses the vendorID string rather than a feature bit to make the path determination, AMD processors that support SSE may end up taking a slower path as a result.
Read the full post from the AMD developer blog.