Consider this example:
cat > pr41118.c <<EOF
void foo(int n, int *a, int *b)
{
int i;
for (i = 0; i < n; i++)
a[i] = b[i];
}
EOF
gcc -S -O2 pr41118.c -floop-parallelize-all -ftree-parallelize-loops=2
grep GOMP 41118.s
GCC considers the loop parallel, even though arrays pointed to by arguments may
arbitrarily overlap. This is because dependency analysis in graphite treats
p[i] as global_mem[alias_set_for_p][i]. In this example, since both a and b
have
alias set 0, a[0][i0] and b[0][i1] are considered independent for i0 != i1.
--
Summary: Wrong dependence analysis in graphite for unrestricted
pointers
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: amonakov at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41118
