There is a blog conversation about a guy who wrote an app to analyse data on a Linux machine and wanted to share it with people in Windows. He observed problems when using MSVC++ compiler and GCC for Windows. That's where I found the compiler switches.
-msse2 -mfpmath=sse
I put these in both the Linux and the Windows Makefile, but it is redundant in Linux as this is part of the default settings.
You cannot understate the meaning of "default" with GNU GCC. It is what compiles the Linux kernel. (Yes. I know that is a special case with special magic.)
James.