https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124074
--- Comment #3 from Thiago Macieira <thiago at kde dot org> --- (In reply to John Platts from comment #2) > Correction: In addition, Microsoft has made some changes to the x86-64 > calling convention for Win64 which makes R16-R29 volatile (which do not need > to be saved by the callee) and R30-R31 nonvolatile (which need to be saved > by the callee prior to use) on x86-64 systems supporting APX, which is > described at > https://learn.microsoft.com/en-us/cpp/build/x64-calling-convention?view=msvc- > 170. I've been discussing with some Intel engineers that System V ABI should also reserve r30 and r31 as non-volatile.
