On Thu, May 20, 2010 at 09:40:47AM -0700, Mark Mitchell wrote: > It is of course a feature much > less valuable on a workstation/server class operating system than on the > VxWorks/RTEMS class of RTOS systems.
Even on servers this option may be quite valuable. I recall seing figures that showed using fp regs for something like structure copies could cost thousands of cpu cycles. Why? With lazy fpu save and restore, the first use of the fpu in a given time slice takes an interrupt. So if your task is only using the fpu occasionally it is a severe misoptimization to choose to use fp regs rather than gp regs. -- Alan Modra Australia Development Lab, IBM
