floor on i386

[Brad Lucier]

I just reviewed the various threads on gcc.gnu.org about slow code
generated for the floor intrinsic.

If one had tree nodes or RTL nodes to express the sequence

Save rounding mode
Change rounding mode to round-down
Convert to integer
Restore rounding mode

then perhaps the rounding mode change changes could be moved
outside of loops where they occur, if there were no floating-point
instructions in  the loop that needed the currently set rounding mode.

Brad Lucier