At optimization levels -o2 and higher, the compiler can generate incorrect code for loops that update a restrict-qualified array using a min/max-style reduction. The array element may retain a stale value instead of being updated.

How it manifests in source:
void update(int8_t* restrict out, const int8_t* restrict in)
{
for (int i = 0; i < N; i++)

}

Workaround 1:
Remove restrict from the affected pointer(s).

void update(int8_t* out, const int8_t* in)

Workaround 2:
Rewrite the reduction to avoid the min/max idiom, keeping restrict.

void update(int8_t* restrict out, const int8_t* restrict in)
{
for (int i = 0; i < N; i++)

}