http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55975
--- Comment #26 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-01-23 12:26:30 UTC --- (In reply to comment #25) > So, what is our decision? > > Are we just doing > - static const uptr kHighMemEnd = 0x00000fffffffffffUL; > + static const uptr kHighMemEnd = 0x00003fffffffffffUL; > , leaving SHADOW_OFFSET=(1ULL << 41) > and using ADD instead of OR when applying SHADOW_OFFSET? > > This seems to work on my ppc box (44-bit) with LLVM > (I've changed it to use ADD on PPC) If that works, it is my preference. But needs testing, also with GCC, and with both 44-bit and 46-bit AS. BTW, I wonder why clang generates larger and slower code with ADD instead of OR, at least gcc seems to generate generally better code with ADD, plus on i?86/x86_64 it even has better HW support for that (for ADD can use both add{l,q} and leal, allowing RA to generate better code). GCC for asan generates always ADD, on all architectures, right now.