Also, changes applied to the FP co-processor by other processes on the machine could impact your process, regardless of your own compilation settings.
That's ancient history. Compilers don't use that instruction set any more in normal operation.
GCC, Java, LLVM, etc, will normally emit SSE2 in order to be standards compliant. They will only relax this if you tell them to, then it's your problem.
I believe there is still quite a bit of cautionary discussion of floating point numbers that was written in the age of the x87, so it's important to understand that people were not just misunderstanding IEEE754, even though their concerns are no longer applicable to modern hardware.