For SSE scalar float / double intrinsics,  “hand” optimization is no longer necessary. This was important, when SSE was initially introduced, and compiler support was limited or nonexistent.  Also SSE scalar float / double provided additional (16) registers and IEEE-754 compliance, not available from the 8087 floating point architecture that preceded it. So application developers where motivated to use SSE instructions versus what the compiler was generating at the time. Modern compilers can now generate and optimize these (SSE scalar) instructions for Intel from C standard scalar code. Of course PowerISA supported IEEE-754 float and double and had 32 dedicated floating point registers from the start (and now 64 with VSX). So replacing Intel specific scalar intrinsic implementation with the equivalent C language scalar implementation is usually a win; it allows the compiler to apply the latest optimization and tuning for the latest generation processor, and is portable to other platforms where the compiler can also apply the latest optimization and tuning for that processor's latest generation.