What is the fastest way to convert float to int on x86

Question

What is the fastest way you know to convert a floating-point number to an int on an x86 CPU. Preferrably in C or assembly (that can be in-lined in C) for any combination of

Answer 1

If you can guarantee the CPU running your code is SSE3 compatible (even Pentium 5 is, JBB), you can allow the compiler to use its FISTTP instruction (i.e. -msse3 for gcc). It seems to do the thing like it should always have been done:

http://software.intel.com/en-us/articles/how-to-implement-the-fisttp-streaming-simd-extensions-3-instruction/

Note that FISTTP is different from FISTP (that has its problems, causing the slowness). It comes as part of SSE3 but is actually (the only) X87-side refinement.

Other then X86 CPU's would probably do the conversion just fine, anyways. :)

Processors with SSE3 support