Re: Do C++ signed types have modulo semantics?

[Paul Koning <pkoning at equallogic dot com>]

>>>>> "Steven" == Steven Bosscher <stevenb@suse.de> writes:

 Steven> Indeed.  Frankly this "seems likely" guess confuses me.  It
 Steven> is already well known that using unsigned types for loop
 Steven> counters may greatly improve the code gcc can generate for
 Steven> loops.  With wrap-around semantics, suddenly countable loops
 Steven> are turned into noncountable loops, overflow can occur,
 Steven> dependencies may be introduced that never happen in reality,
 Steven> and so on.

I must be missing something.  Unsigned has wraparound (modulo)
semantics.  So if unsigned loop counters produce better code, why does
making signed ints wrap cause worse code rather than better (just as
good as unsigned) code?

     paul