https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115014
--- Comment #2 from Martin Doucha <mdoucha at suse dot cz> --- (In reply to Andrew Pinski from comment #1) > I am not so sure this is wanted. GCC assumes a flat memory system for stack > and normal memory accesses . This is certainly not wanted in the most common case where the flat memory assumption is correct. But it should be used for compiling embedded binaries with -ffreestanding argument. > >1) If the address in EBP was calculated from stack pointer value, generate > >unprefixed instructions. > > This fix is not simple really because addresses don't need to be just in EBP > really and even can be stored off into stack memory and then loaded back. > > It seems like there must be a better way of implementing this inside your > kernel as a flat memory system between stack and data segments is not going > to change because it would add a very complex tracking. The worst case for adding prefixes where they're not needed is slight binary size and possibly performance penalty. The worst case for not adding them is stack segment exception. The tracking does not need to be perfect.
