http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55289
--- Comment #13 from Jack Howarth <howarth at nitro dot med.uc.edu> 2012-11-13 20:25:45 UTC --- Also note the comment in mach_override.c... #elif defined(__x86_64__) // TODO(glider): disassembling the "0x48, 0x89" sequences is trickier than it's done below. // If it stops working, refer to http://ref.x86asm.net/geek.html#modrm_byte_32_64 to do it // more accurately. // Note: 0x48 is in fact the REX.W prefix, but it might be wrong to treat it as a separate // instruction. looks like we are bumping into this bug.
