Are your sure of this? It's my understanding that SSE registers require the use of a special API and standard floating point operations do not use them.
But the last time I worked with them was writing a SIMD vector library 7 years ago.
For 32-bit systems, you still theoretically have to check, but I think every halfway modern compiler also uses SSE2 as the default target.
No, SSE registers are used by most compilers that do floating point these days. They support all the usual IEEE float math operations and a host of bit twiddling operations as well as vector operations. The vector operations do still require using compiler intrinsics in C++, although some autovectorization does occur in gcc, icc, and llvm.
-mfpmath=unit
Generate floating-point arithmetic for selected unit unit. The choices for unit are:
‘387’
Use the standard 387 floating-point coprocessor present on the majority of chips and emulated otherwise. Code compiled with this option runs almost everywhere. The temporary results are computed in 80-bit precision instead of the precision specified by the type, resulting in slightly different results compared to most of other chips. See -ffloat-store for more detailed description.
This is the default choice for non-Darwin x86-32 targets.