http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56764
Cong Hou <congh at google dot com> changed:
What |Removed |Added
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CC| |congh at google dot com
--- Comment #2 from Cong Hou <congh at google dot com> ---
I have made a patch on this issue. However, I don't think the example here is
proper. Say z1 == &(x[0][4]) (assume VF=4). Then after unrolling the loop for 4
times, there is still no data dependence that prevents vectorization.
I think a better example is like the one shown below:
__attribute__((noinline, noclone)) void
foo (float x[3][32], float y1, float y2, float y3, float *z1, float *z2, float
*z3)
{
int i;
for (i = 0; i < 16; i++)
{
z1[i] = -y1 * x[0][i*2];
z2[i] = -y2 * x[1][i*2];
z3[i] = -y3 * x[2][i*2];
}
}
Here we have to make sure z1/z2/z3 does not alias with x across the whole range
being traversed. Then we could merge the alias checks between z1 and
&x[0][0:32]/&x[1][0:32]/&x[2][0:32] into one.
