On Tue, Sep 11, 2012 at 01:29:52AM +0100, Maciej W. Rozycki wrote: > Relying on any call-clobbered registers, including $7 to be preserved > across a syscall is risky, to say the least, as this is not guaranteed by > the syscall ABI. I do wonder however why we have these instructions to > save/restore $25 in SAVE_SOME/RESTORE_SOME. This dates back to 2.4 at the > very least. > > Ralf, any insights? It dates back to the initial commit in 36ea5120 from March 27, 1998 for 2.1.90 when for the sake of better lmbench syscall latency numbers I had introduced the concept of partial saving of a register frame. I think it should rather have been in SAVE_TEMP/RESTORE_TEMP instead. Ralf
