[Bug c/53353] Missing error/warning when using __int128_t with incorrect asm register constraints

[svfuerst at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53353

--- Comment #4 from Steven Fuerst <svfuerst at gmail dot com> 2012-05-15 02:09:05 UTC ---
Actually, it is the rax:rdx pair that is most likely.  ax:dx only has 32 bits. 
rax:rdx is specified by the 'A' constraint, the only gpr option that is 128
bits.

(Yes, it would be nice to pass a 128 bit integer in some other pair of
registers as an enhancement, but currently only the 'A' constraint works.)