https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104189
--- Comment #7 from John Paul Adrian Glaubitz <glaubitz at physik dot fu-berlin.de> --- FWIW, I also asked David Miller regarding the register preservation and here is his answer: > The full 64-bit registers of the out and global registers are saved at trap > time. > But only 32-bits of the register window registers will be saved. I'm pretty > sure > this is what Solaris does too. > We have a mechanism for doing 64-bit register saves for 32-bit tasks. We > needed > this for some crypto assembler. The process has to request 64-bit saves and > allocate a suitable stack frame (64-bit aligned and biased like 64-bit). He also agrees that defaulting to V8+ in this case should be fine. So, I guess we can go ahead and make this change!