https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77902
--- Comment #1 from Allan Jensen <linux at carewolf dot com> ---
Further experimentation shows that GCC can sometimes reason about the remaining
range but does so inconsistenly.
For instance this examplse also fails:
int result = 0;
for (; count >= 4; count -= 4) {
// Manually vectorized or batched code
foobar_4x(result, vector);
vector += 4;
}
for (; count >= 0; --count) { // Still autovectorized
result += *vector++;
}
But replacing the epilogue with a loop that counts up, and GCC
appears to figure out it is pointless to vectorize:
for (int i = 0; i < count; ++count) { // correctly not vectorized
