openmp: Fix ICE on non-rectangular loop with known 0 iterations

The loops in the testcase are non-rectangular and have 0 iterations
(the outer loop iterates, but the inner one never).  In this case we
just have the overall number of iterations computed (0), and don't have
factor and other values computed.  We never need to map logical iterations
to the individual iterations in that case, and we were crashing during
expansion of that code.

2020-11-18  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/97862
	* omp-expand.c (expand_omp_for_init_vars): Don't use the sqrt path
	if number of iterations is constant 0.

	* c-c++-common/gomp/pr97862.c: New test.

diff --git a/gcc/omp-expand.c b/gcc/omp-expand.c
index b731fd69b1e5b8025ff3f901b2e15bf9ee02ada6..c0e94e5e323690842793f422eceb94cf02ca8790 100644 (file)
--- a/gcc/omp-expand.c
+++ b/gcc/omp-expand.c
@@ -2514,7 +2514,8 @@ expand_omp_for_init_vars (struct omp_for_data *fd, gimple_stmt_iterator *gsi,
              && (TREE_CODE (fd->loop.n2) == INTEGER_CST
                  || fd->first_inner_iterations)
              && (optab_handler (sqrt_optab, TYPE_MODE (double_type_node))
-                 != CODE_FOR_nothing))
+                 != CODE_FOR_nothing)
+             && !integer_zerop (fd->loop.n2))
            {
              tree outer_n1 = fd->adjn1 ? fd->adjn1 : fd->loops[i - 1].n1;
              tree itype = TREE_TYPE (fd->loops[i].v);

diff --git a/gcc/testsuite/c-c++-common/gomp/pr97862.c b/gcc/testsuite/c-c++-common/gomp/pr97862.c
new file mode 100644 (file)
index 0000000..21aad3f
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/gomp/pr97862.c
@@ -0,0 +1,15 @@
+/* PR middle-end/97862 */
+
+void
+foo (void)
+{
+  int i, j;
+#pragma omp for collapse(2)
+  for (i = 0; i < 1; ++i)
+    for (j = 0; j < i; ++j)
+      ;
+#pragma omp for collapse(2)
+  for (i = 0; i < 20; i++)
+    for (j = 0; j < i - 19; j += 1)
+      ;
+}