Been a while since I was actively involved in GCC development, but back then most issues like this AFAIR were due to math functions and not basic arithmetic. GC

Been a while since I was actively involved in GCC development, but back then most issues like this AFAIR were due to math functions and not basic arithmetic. GCC doesn't control the target libm, and correctly rounded libm's are rare and much slower than ones which permit a bit more slop in the results.