http://gcc.gnu.org/ml/gcc/2005-01/msg00700.html onsideriing this code: if (onlyjump_p (i2) || (returnjump_p (i2) && !side_effects_p (PATTERN (i2)))) { last2 = i2; /* Count everything except for unconditional jump as insn. */ if (!simplejump_p (i2) && !returnjump_p (i2) && last1) ninsns++; i2 = PREV_INSN (i2); } you count unconditional jumps with a clobber, but you don't count conditional returns (, or even an instruction that solves a travelling salesman problem and returns if it finds a solution within a given cost bound).
r0-127486-ga0cbe71e87398b changed the code slightly . It was originally added with r0-39385-g08f7f057cc4762 and then moved slightly by r0-39553-gd1ee6d9bb7d372. I don't know if Honza would remember any of this code though since it was done over 20 years ago.