strcat+strcat+strcat == baaad

[David Laight]

> With gcc 3.2? That compiler optimizes the jmp away in an if statement,
> apparently assuming that the "if" clause is executed much more often.
> The "else" clause, OTOH, jmp's to the end of the subroutine and jumps
> back afterwards. Thus if the compiler guesses wrongly, the CPU'll have
> to do two more jmp's per loop, with possible instruction cache miss.
> Hard for me to believe that'll be a speed improvement on any CPU. If the
> compiler guesses right, 1 jmp will be saved per loop.

Actually 2.95.3 which doesn't seem to want to generate a loop
with only one taken branch.  Something must make the conditional
forward jump be faster than the unconditional one.
And yes, I couldn't believe it either :-)

	David

-- 
David Laight: david at l8s.co.uk