bit-for-bit IEEE compliance vs performance - strict compliance bit

[Tom Lynch]

I can add a mode bit to an x86 processor that when set would have the
effect of causing values to round to the IEEE format indicated by the
precision control field.  E.g. rounding to double would ignore the
extra exponent range.  The mode would be off by default; thus insuring
compatibility with existing code.  This would be the "strict IEEE
compliance" mode.

I believe that such a mode would solve the compiler issues right? .. at
least for this AMD processor.  Of course other Vendors could do this
also.  Any one else out there want to settle on a place for the bit?

Would this be desirable?  Are there any other "strict compliance" issues
in the x86 world?

-tom