------- Comment #6 from dann at godzilla dot ics dot uci dot edu 2006-12-12
06:07 -------
(In reply to comment #5)
> (In reply to comment #1)
> > Confirmed (but it's not PRE).
> >
> The second is smaller, and no more or less efficient since the addition is
> calculated on both paths anyway.
>
> Both are valid results, and what RTL does with them is it's business.
>
> I don't believe you can claim they should generate identical assembly.
>
> The actual thing this testcase is trying to test, that load-PRE is performed,
> has succeeded.
> Thus i am closing this bug as WORKSFORME.
> If you see something *actually wrong* with the result, rather than just
> disassembly, please feel free to reopen.
Here is a slightly modified example that shows that there's still a PRE
opportunity
void motion_test22(int * data, int i)
{
int j;
if (data[1]) {
data[data[2]] = 2;
j = data[0] * data[3];
i = i * j;
}
data[4] = data[0] * data[3];
data[5] = i;
}
<L0>:;
*((int *) ((unsigned int) *(data + 8B) * 4) + data) = 2;
prephitmp.26 = *data;
prephitmp.31 = *(data + 12B);
i = prephitmp.26 * i * prephitmp.31;
<L1>:;
*(data + 16B) = prephitmp.31 * prephitmp.26;
*(data + 20B) = i;
return;
There are 3 multiplications on the L0-L1 path. It should be possible
to only have 2 multiplications on that path.
--
dann at godzilla dot ics dot uci dot edu changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|WORKSFORME |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30105
