------- Additional Comments From belyshev at depni dot sinp dot msu dot ru
2005-01-23 19:51 -------
(In reply to comment #18)
> I'm not sure what you think the missed optimization is here. You will have
> to show what you want at the assembly level, and explain why you think this
> is a coalescing problem. So far, I don't see a missed optimization.
Short examples in comment #9 I used only to show that there is problem with
variable coalescing at tree level, of course they all optimized at rtl level.
To see *the* problem, compare i386 assembly and .optimized dumps for these two
functions on mainline with patch to bug 19464 applied:
int r[6];
void f (int n)
{
while (-- n)
{
r [0] += r [5];
r [1] += r [0];
r [2] += r [1];
r [3] += r [2];
r [4] += r [3];
r [5] += r [4];
}
}
void g (int n)
{
while (-- n)
{
r [0] += r [1];
r [1] += r [2];
r [2] += r [3];
r [3] += r [4];
r [4] += r [5];
r [5] += r [0];
}
}
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19580
