On Thu, Sep 29, 2022 at 12:04:05AM +0100, Iain Sandoe wrote: > > On 28 Sep 2022, at 22:30, Segher Boessenkool <seg...@kernel.crashing.org> > > wrote: > > That works on Linux as well. What still does not work is user-mode > > context switches in 32-bit processes (so setjmp and getcontext stuff). > > AFAIU the Darwin impl. it is the same - the user context only contains 32b > register images.
Huh, I thought Darwin did this properly. > Since one can only use the feature between function calls, You still have to preserve the non-volatile GPRs. All 64 bits of it. > I guess that the > setjmp/longjmp stuff is not so critical on Darwin***. However, even being able > to use 64b insns between calls could give a massive win in allowing, for > example, lock-free 64b atomics. But that is not how GCC with -mpowerpc64 works: the calling convention is the usual 32-bit one, but the functions are 64-bit otherwise; it uses all 64 bits of GPRs everywhere except in function calls. Segher
