>>>>> "tm" == tm gccmail <[EMAIL PROTECTED]> writes:
tm> On 25 Mar 2005, Ian Lance Taylor wrote: >> Safe but very costly. It assumes that every processor has a cheap >> way to save and restore the condition codes in user mode, which is >> not necessarily the case. And it assumes that the save and >> restore can be removed when not required, which is not obvious to >> me. tm> Not necessarily. tm> You need the ability to regenerate the condition code. There's at tm> least two ways of doing this: tm> 1. Saving/restoring the condition code tm> 2. Rematerializing the condition code. This would usually be a tm> simple load which is faster than the save/load combo of #1. "is faster" -- on some processors, yes. Not on all. For example, an MFPS/MTPS pair to a register on a PDP-11 (when available) is likely to be faster than a load that references memory. paul
