https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98088
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Hafiz Abid Qadeer <ab...@gcc.gnu.org>: https://gcc.gnu.org/g:e4dcb3383bff4c209a918127551cabc56b4171ae commit r10-9711-ge4dcb3383bff4c209a918127551cabc56b4171ae Author: Hafiz Abid Qadeer <ab...@codesourcery.com> Date: Thu Apr 8 17:31:30 2021 +0100 [OpenACC] Fix an ICE where a loop with GT condition is collapsed. We have seen an ICE both on trunk and devel/omp/gcc-10 branches which can be reprodued with this simple testcase. It occurs if an OpenACC loop has a collapse clause and any of the loop being collapsed uses GT or GE condition. This issue is specific to OpenACC. int main (void) { int ix, iy; int dim_x = 16, dim_y = 16; { for (iy = dim_y - 1; iy > 0; --iy) for (ix = dim_x - 1; ix > 0; --ix) ; } } The problem is caused by a failing assertion in expand_oacc_collapse_init. It checks that cond_code for fd->loop should be same as cond_code for all the loops that are being collapsed. As the cond_code for fd->loop is LT_EXPR with collapse clause (set at the end of omp_extract_for_data), this assertion forces that all the loop in collapse clause should use < operator. There does not seem to be anything in the code which demands this condition as loop with > condition works ok otherwise. I digged old mailing list a bit but could not find any discussion on this change. Looking at the code, expand_oacc_for checks that fd->loop->cond_code is either LT_EXPR or GT_EXPR. I guess the original intention was to have similar checks on the loop which are being collapsed. But the way check was written does not acheive that. I have fixed it by modifying the check in the assertion to be same as check on fd->loop->cond_code. I tested goacc and libgomp (with nvptx offloading) and did not see any regression. I have added new tests to check collapse with GT/GE condition. PR middle-end/98088 gcc/ * omp-expand.c (expand_oacc_collapse_init): Update condition in a gcc_assert. gcc/testsuite/ * c-c++-common/goacc/collapse-2.c: New. libgomp/ * testsuite/libgomp.oacc-c-c++-common/collapse-2.c: Add check for loop with GT/GE condition. * testsuite/libgomp.oacc-c-c++-common/collapse-3.c: Likewise. (cherry picked from commit ac200799acb5cd2fb9e1758f6bf5fff1978daaeb)
