http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54419
--- Comment #7 from Jack Howarth <howarth at nitro dot med.uc.edu> 2012-08-31 15:40:25 UTC --- Would the approach used in the proposed linux kernel patch be feasible? + /* RDRAND sets carry bit on success, otherwise we should try + * again. */ + movl $0x10, %ecx +2: + /* rdrand %eax */ + .byte 0x0f, 0xc7, 0xf0 + jc 4f + loop 2b + + /* Fall through: if RDRAND is supported but fails, use RDTSC, + * which is guaranteed to be supported. */ +3: + rdtsc + shll $0xc, %eax +4: + /* Maximum offset at 64mb to be safe */ Since rdrand is only supported on Ivy Bridge processors, shouldn't src/c++11/random.cc have a fall through using rdtsc in case the processor doesn't support rdrand?
