compiler: prevent hosted per-thread arrays are dereferenced within partree at read

Author: mloubout

devito/passes/iet/parpragma.py

@@ -317,11 +317,21 @@ def _make_parregion(self, partree, parrays):
             i = n.write
             if not (i.is_Array or i.is_TempFunction):
                 continue
-            elif i in parrays:
-                pi = parrays[i]
-            else:
-                pi = parrays.setdefault(i, i._make_pointer(dim=self.threadid))
-            vexpandeds.append(VExpanded(i, pi))
+            elif i not in parrays:
+                parrays.setdefault(i, i._make_pointer(dim=self.threadid))
+            vexpandeds.append(i)
+
+        # Vector-expand all read Arrays within `partree` that were not
+        # already vector-expanded above. Those might be written to in
+        # a previous parallel region such as hoisted time invariants.
+        for n in FindNodes(Expression).visit(partree):
+            for i in n.reads:
+                if not (i.is_Array or i.is_TempFunction):
+                    continue
+                elif i in parrays and i not in vexpandeds:
+                    vexpandeds.append(i)
+
+        vexpandeds = [VExpanded(i, parrays[i]) for i in vexpandeds]
 
         if vexpandeds:
             init = self.langbb['thread-num'](retobj=self.threadid)