https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85000
--- Comment #1 from G. Steinmetz <gs...@t-online.de> --- Configured with --enable-checking=yes : $ gcc-8-20180318 -c z1.c -O2 -fopenmp during GIMPLE pass: omplower z1.c: In function 'foo': z1.c:8:6: internal compiler error: in scan_omp_1_op, at omp-low.c:3014 n++; ~^~ 0xb3f192 scan_omp_1_op ../../gcc/omp-low.c:3014 0xf66e22 walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*)) ../../gcc/tree.c:11387 0xf67276 walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*, tree_node* (*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*, default_hash_traits<tree_node*> >*)) ../../gcc/tree.c:11703 0x9c00f0 walk_gimple_op(gimple*, tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:203 0x9c072c walk_gimple_stmt(gimple_stmt_iterator*, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:586 0x9c0918 walk_gimple_seq_mod(gimple**, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:51 0x9c07d2 walk_gimple_stmt(gimple_stmt_iterator*, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:596 0x9c0918 walk_gimple_seq_mod(gimple**, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:51 0x9c07d2 walk_gimple_stmt(gimple_stmt_iterator*, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:596 0x9c0918 walk_gimple_seq_mod(gimple**, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:51 0xb3e169 scan_omp ../../gcc/omp-low.c:3205 0xb4a50a scan_omp_parallel ../../gcc/omp-low.c:1796 0xb4a50a scan_omp_1_stmt ../../gcc/omp-low.c:3123 0x9c06fa walk_gimple_stmt(gimple_stmt_iterator*, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:568 0x9c0918 walk_gimple_seq_mod(gimple**, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:51 0x9c07d2 walk_gimple_stmt(gimple_stmt_iterator*, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:596 0x9c0918 walk_gimple_seq_mod(gimple**, tree_node* (*)(gimple_stmt_iterator*, bool*, walk_stmt_info*), tree_node* (*)(tree_node**, int*, void*), walk_stmt_info*) ../../gcc/gimple-walk.c:51 0xb3e169 scan_omp ../../gcc/omp-low.c:3205 0xb5460a execute_lower_omp ../../gcc/omp-low.c:8999 0xb5460a execute ../../gcc/omp-low.c:9056