https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66288
Bug ID: 66288
Summary: parallelized loop vectorized with runtime alias check
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
Another pr46032-inspired example.
Consider par-3.c:
...
#if defined (EXEC)
static void __attribute__((noinline,noclone))
init (double *p, int n)
{
int i;
for (i = 0; i < n; ++i)
p[i] = 0.0;
}
#else
extern void init (double *, int);
#endif
#define nEvents 1000
int
main (int argc)
{
double results[nEvents];
double data[nEvents];
double coeff = 12.2;
init (data, nEvents);
init (results, nEvents);
for (INDEX_TYPE idx = 0; idx < nEvents; idx++)
results[idx] = coeff * data[idx];
return !(results[argc] == 0.0);
}
...
we compile using this command-line:
...
gcc -O2 -ftree-parallelize-loops=2 -ftree-vectorize -S -fdump-tree-all-all
par-3.c -DINDEX_TYPE="unsigned long"
...
[ When using any other INDEX_TYPE than unsigned long, we run into what looks
like PR66285. ]
In the vectorize dump file, we find:
...
par-3.c:26:32: note: versioning for alias required: can't determine dependence
between *data_4[ivtmp_20] and *results_5[ivtmp_20]
par-3.c:26:32: note: mark for run-time aliasing test between *data_4[ivtmp_20]
and *results_5[ivtmp_20]
...
