[Bug libgomp/81778] libgomp.c/for-5.c failure on nvptx -- illegal memory access

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81778

--- Comment #7 from Tom de Vries <vries at gcc dot gnu.org> ---
A point fix could look like:
...
diff --git a/gcc/omp-expand.c b/gcc/omp-expand.c
index 3990998..2439a89 100644
--- a/gcc/omp-expand.c
+++ b/gcc/omp-expand.c
@@ -4339,6 +4339,26 @@ expand_omp_for_static_chunk (struct omp_region *region,
     L2:
        V -= STEP * (simt_vf - 1)

+    fix could be:
+
+       V = N1 + simt_lane * STEP; // Can this overflow?
+       goto L1;
+    L0:
+       BODY;
+       if (overflow (V += STEP * simt_vf)) goto Loverflow; else goto Lincr;
+       // STEP > 0: if (STEP * simt_vf > max (type (V)) - V)
+       // STEP < 0: if (V < min (type (V)) - STEP * simt_vf)
+    Lincr:
+       V += STEP * simt_vf;
+    L1:
+       if (V cond N2) goto L0; else goto L2;
+    Loverflow:
+        V += STEP;
+       goto Lend;
+    L2:
+       V -= STEP * (simt_vf - 1)
+    Lend:
+
     For collapsed loops, given parameters:
       collapse(3)
       for (V1 = N11; V1 cond1 N12; V1 += STEP1)
...