https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67986
Bug ID: 67986
Summary: OpenMP collapse - invalid code generated.
Product: gcc
Version: 4.9.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libgomp
Assignee: unassigned at gcc dot gnu.org
Reporter: lbukata at gmail dot com
CC: jakub at gcc dot gnu.org
Target Milestone: ---
Created attachment 36525
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36525&action=edit
Simple demonstration of the bug.
Invalid code for the following code:
#pragma omp parallel for collapse(2)
for (int32_t i = 0; i < N-1; ++i) {
for (int32_t j = i+1; j < N; ++j) {
#pragma omp critical
cout<<"(i,j): ("<<i<<","<<j<<")"<<endl;
}
}
Sequential code generates valid pairs of indices, however, the parallel code
neglects the dependency of inner loop range on outer loop variable. The full
source is attached.
Tested on both GCC 4.8.5 and GCC 4.9.3 with the same result. The distro is
Gentoo Linux 2015.
