Hi Mike, On 21 Jul 2012, at 18:27, Mike Stump wrote:
> On Jul 21, 2012, at 9:12 AM, Iain Sandoe wrote: >> At present, if a G5 or 970 processor is selected (-mcpu=), we can (and do) >> generate 64 bit register usage for m32 code. This appears to be a >> long-standing bug. > > Hum, do you have an example of something that fails? I can look for something, if necessary. > I ask, cause I think the if you say that you have a 64-bit processor, then, > generating code for a 64-bit processor isn't necessarily wrong. indeed, highly desirable to make use of any improvements available. > If you say you have a 64-bit processor, then you likely have an OS that runs > on that processor, and that OS I'm thinking will save and restore the full > 64-bit registers. If not, do you have a pointer to documentation that says > this won't work? Mac_OS_X_ABI_Function_Calls.pdf pp 19 para 2 (box). This stipulates that even on a 64 bit processor, only the lower 32 bits of nonvolatile registers are saved/restored. All 64 bits are saved across context switches/asynchronous events. That is to quote the doc: one can *only* use the full 64 bits 'between function calls' safely. If there's a different mechanism for enforcing what's implied above, then we could use that. cheers Iain
