https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84742
--- Comment #3 from Vegard Nossum <vegard.nossum at gmail dot com> --- gcc/recog.c:2395 is: 2390 case '0': case '1': case '2': case '3': case '4': 2391 case '5': case '6': case '7': case '8': case '9': 2392 { 2393 char *end; 2394 op_alt[i].matches = strtoul (p, &end, 10); 2395 op_alt[op_alt[i].matches].matched = i; 2396 p = end; 2397 } 2398 continue; It's a bit weird because I don't see any digits in the constraints in the test case.