https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114193
Bug ID: 114193
Summary: missed early break vectorization of reduction
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: acoplan at gcc dot gnu.org
Target Milestone: ---
For the following loop:
int a[1024];
int f(int *x, int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
{
if (a[i] == 42)
break;
sum += a[i];
}
return sum;
}
at -O3 on aarch64 we miss vectorizing it. It works if I move the early exit
down below the update of sum. It looks like vect_analyze_scalar_cycles fails
to detect this as a reduction:
/app/example.c:5:23: note: Analyze phi: sum_10 = PHI <sum_6(7), 0(6)>
/app/example.c:5:23: missed: intermediate value used outside loop.
/app/example.c:5:23: missed: Unknown def-use cycle pattern.
