Hi!
The OpenMP 5 standard requires that if some loop in OpenMP loop nest refers
to some outer loop's iterator variable, then the subtraction of the
multiplication
factors for the outer iterator multiplied by the outer increment modulo the
inner increment is 0. For loops with non-constants in any of these we can't
diagnose it, it would be a task for something like -fsanitize=openmp,
but if all these are constant, we can diagnose it.
Bootstrapped/regtested on x86_64-linux and i686-linux, committed to trunk.
2020-07-02 Jakub Jelinek <ja...@redhat.com>
* omp-expand.c (expand_omp_for): Diagnose non-rectangular loops with
invalid steps - ((m2 - m1) * incr_outer) % incr must be 0 in valid
OpenMP non-rectangular loops. Use XALLOCAVEC.
* c-c++-common/gomp/loop-7.c: New test.
--- gcc/omp-expand.c.jj 2020-06-29 14:51:54.855085915 +0200
+++ gcc/omp-expand.c 2020-06-30 15:45:00.531813174 +0200
@@ -7122,15 +7122,55 @@ expand_omp_for (struct omp_region *regio
struct omp_for_data fd;
struct omp_for_data_loop *loops;
- loops
- = (struct omp_for_data_loop *)
- alloca (gimple_omp_for_collapse (last_stmt (region->entry))
- * sizeof (struct omp_for_data_loop));
+ loops = XALLOCAVEC (struct omp_for_data_loop,
+ gimple_omp_for_collapse (last_stmt (region->entry)));
omp_extract_for_data (as_a <gomp_for *> (last_stmt (region->entry)),
&fd, loops);
region->sched_kind = fd.sched_kind;
region->sched_modifiers = fd.sched_modifiers;
region->has_lastprivate_conditional = fd.lastprivate_conditional != 0;
+ if (fd.non_rect && !gimple_omp_for_combined_into_p (fd.for_stmt))
+ {
+ for (int i = fd.first_nonrect; i <= fd.last_nonrect; i++)
+ if ((loops[i].m1 || loops[i].m2)
+ && (loops[i].m1 == NULL_TREE
+ || TREE_CODE (loops[i].m1) == INTEGER_CST)
+ && (loops[i].m2 == NULL_TREE
+ || TREE_CODE (loops[i].m2) == INTEGER_CST)
+ && TREE_CODE (loops[i].step) == INTEGER_CST
+ && TREE_CODE (loops[i - loops[i].outer].step) == INTEGER_CST)
+ {
+ tree t;
+ tree itype = TREE_TYPE (loops[i].v);
+ if (loops[i].m1 && loops[i].m2)
+ t = fold_build2 (MINUS_EXPR, itype, loops[i].m2, loops[i].m1);
+ else if (loops[i].m1)
+ t = fold_build1 (NEGATE_EXPR, itype, loops[i].m1);
+ else
+ t = loops[i].m2;
+ t = fold_build2 (MULT_EXPR, itype, t,
+ fold_convert (itype,
+ loops[i - loops[i].outer].step));
+ if (TYPE_UNSIGNED (itype) && loops[i].cond_code == GT_EXPR)
+ t = fold_build2 (TRUNC_MOD_EXPR, itype,
+ fold_build1 (NEGATE_EXPR, itype, t),
+ fold_build1 (NEGATE_EXPR, itype,
+ fold_convert (itype,
+ loops[i].step)));
+ else
+ t = fold_build2 (TRUNC_MOD_EXPR, itype, t,
+ fold_convert (itype, loops[i].step));
+ if (integer_nonzerop (t))
+ error_at (gimple_location (fd.for_stmt),
+ "invalid OpenMP non-rectangular loop step; "
+ "%<(%E - %E) * %E%> is not a multiple of loop %d "
+ "step %qE",
+ loops[i].m2 ? loops[i].m2 : integer_zero_node,
+ loops[i].m1 ? loops[i].m1 : integer_zero_node,
+ loops[i - loops[i].outer].step, i + 1,
+ loops[i].step);
+ }
+ }
gcc_assert (EDGE_COUNT (region->entry->succs) == 2);
BRANCH_EDGE (region->entry)->flags &= ~EDGE_ABNORMAL;
--- gcc/testsuite/c-c++-common/gomp/loop-7.c.jj 2020-06-30 16:29:38.969728972
+0200
+++ gcc/testsuite/c-c++-common/gomp/loop-7.c 2020-06-30 15:49:17.788152186
+0200
@@ -0,0 +1,24 @@
+void
+foo (void)
+{
+ #pragma omp for collapse(2) /* { dg-error "invalid OpenMP non-rectangular
loop step" } */
+ for (int i = 0; i < 6; i++)
+ for (int j = 4 * i; j < 7 * i; j += 2)
+ ;
+ #pragma omp for collapse(2) /* { dg-error "invalid OpenMP non-rectangular
loop step" } */
+ for (int i = 0; i < 32; i += 7)
+ for (int j = 3 * i; j < 7 * i; j += 30)
+ ;
+ #pragma omp for collapse(2)
+ for (int i = 0; i < 6; i++)
+ for (int j = 4 * i; j < 6 * i; j += 2)
+ ;
+ #pragma omp for collapse(2)
+ for (int i = 0; i < 6; i += 2)
+ for (int j = 4 * i; j < 7 * i; j += 2)
+ ;
+ #pragma omp for collapse(2)
+ for (int i = 0; i < 6; i += 5)
+ for (int j = 4 * i; j < 7 * i; j += 15)
+ ;
+}
Jakub
