https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66285
--- Comment #7 from vries at gcc dot gnu.org ---
(In reply to Richard Biener from comment #6)
> I thought that parallelizing vectorized loops is harder (you eventually get
> extra prologue and epliogue loops, etc).
Another example, par-4.c:
...
int __attribute__((noinline,noclone))
f (int argc, double *__restrict results, double *__restrict data, INDEX_TYPE n)
{
double coeff = 12.2;
for (INDEX_TYPE idx = 0; idx < n; idx++)
results[idx] = coeff * data[idx];
return !(results[argc] == 0.0);
}
#define nEvents 1000
#if defined (MAIN)
int
main (int argc)
{
double results[nEvents] = {0};
double data[nEvents] = {0};
return f (argc, results, data, nEvents);
}
#endif
...
When not parallelizing, we vectorize without problems:
...
parloops_factor: 0, index_type: int:
vectorized: 1, parallelized: 0
parloops_factor: 0, index_type: unsigned int:
vectorized: 1, parallelized: 0
parloops_factor: 0, index_type: long:
vectorized: 1, parallelized: 0
parloops_factor: 0, index_type: unsigned long:
vectorized: 1, parallelized: 0
...
When parallelizing, we generate both a low iteration count loop, and a
split-off parallelized loop. The vectorizer vectorizes both loops (each of
which contains an epilogue):
...
parloops_factor: 2, index_type: int:
vectorized: 2, parallelized: 1
parloops_factor: 2, index_type: long:
vectorized: 2, parallelized: 1
parloops_factor: 2, index_type: unsigned long:
vectorized: 2, parallelized: 1
...
Except in the case of unsigned int, in which case it only vectorizes the low
iteration count loop:
...
parloops_factor: 2, index_type: unsigned int:
vectorized: 1, parallelized: 1
...
The other loop fails to vectorize in a fashion similar as decribed for par-2.c
with INDEX_TYPE (unsigned) int.
