8258393: Shenandoah: "graph should be schedulable" assert failure

Reviewed-by: rkennke, thartmann

src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp

@@ -2459,6 +2459,21 @@ bool MemoryGraphFixer::mem_is_valid(Node* m, Node* c) const {
 
 Node* MemoryGraphFixer::find_mem(Node* ctrl, Node* n) const {
   assert(n == NULL || _phase->ctrl_or_self(n) == ctrl, "");
+  assert(!ctrl->is_Call() || ctrl == n, "projection expected");
+#ifdef ASSERT
+  if ((ctrl->is_Proj() && ctrl->in(0)->is_Call()) ||
+      (ctrl->is_Catch() && ctrl->in(0)->in(0)->is_Call())) {
+    CallNode* call = ctrl->is_Proj() ? ctrl->in(0)->as_Call() : ctrl->in(0)->in(0)->as_Call();
+    int mems = 0;
+    for (DUIterator_Fast imax, i = call->fast_outs(imax); i < imax; i++) {
+      Node* u = call->fast_out(i);
+      if (u->bottom_type() == Type::MEMORY) {
+        mems++;
+      }
+    }
+    assert(mems <= 1, "No node right after call if multiple mem projections");
+  }
+#endif
   Node* mem = _memory_nodes[ctrl->_idx];
   Node* c = ctrl;
   while (!mem_is_valid(mem, c) &&

src/hotspot/share/opto/loopnode.cpp

@@ -4968,26 +4968,26 @@ Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
   if (n->is_Load() && LCA != early) {
     int load_alias_idx = C->get_alias_index(n->adr_type());
     if (C->alias_type(load_alias_idx)->is_rewritable()) {
+      Unique_Node_List worklist;
 
-      Node_List worklist;
-
-      Node *mem = n->in(MemNode::Memory);
+      Node* mem = n->in(MemNode::Memory);
       for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
         Node* s = mem->fast_out(i);
         worklist.push(s);
       }
-      while(worklist.size() != 0 && LCA != early) {
-        Node* s = worklist.pop();
+      for (uint i = 0; i < worklist.size() && LCA != early; i++) {
+        Node* s = worklist.at(i);
         if (s->is_Load() || s->Opcode() == Op_SafePoint ||
-            (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0)) {
+            (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0) ||
+            s->is_Phi()) {
           continue;
         } else if (s->is_MergeMem()) {
           for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
             Node* s1 = s->fast_out(i);
             worklist.push(s1);
           }
         } else {
-          Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
+          Node* sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
           assert(sctrl != NULL || !s->is_reachable_from_root(), "must have control");
           if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
             const TypePtr* adr_type = s->adr_type();
@@ -5011,6 +5011,22 @@ Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
           }
         }
       }
+      // For Phis only consider Region's inputs that were reached by following the memory edges
+      if (LCA != early) {
+        for (uint i = 0; i < worklist.size(); i++) {
+          Node* s = worklist.at(i);
+          if (s->is_Phi() && C->can_alias(s->adr_type(), load_alias_idx)) {
+            Node* r = s->in(0);
+            for (uint j = 1; j < s->req(); j++) {
+              Node* in = s->in(j);
+              Node* r_in = r->in(j);
+              if (worklist.member(in) && is_dominator(early, r_in)) {
+                LCA = dom_lca_for_get_late_ctrl(LCA, r_in, n);
+              }
+            }
+          }
+        }
+      }
     }
   }
 

test/hotspot/jtreg/gc/shenandoah/compiler/TestBadRawMemoryAfterCall.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2021, Red Hat, Inc. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8258393
+ * @summary Shenandoah: "graph should be schedulable" assert failure
+ * @requires vm.flavor == "server"
+ * @requires vm.gc.Shenandoah
+ *
+ * @run main/othervm -XX:+UseShenandoahGC -XX:-BackgroundCompilation TestBadRawMemoryAfterCall
+ *
+ */
+
+public class TestBadRawMemoryAfterCall {
+    public static void main(String[] args) {
+        A a = new A();
+        B b = new B();
+        C c = new C();
+        for (int i = 0; i < 20_000; i++) {
+            test(a);
+            test(b);
+            test(c);
+        }
+    }
+
+    private static Object test(A a) {
+        if (a.getClass() == A.class) {
+        }
+
+        Object o = null;
+        try {
+            a.m();
+            o = a.getClass();
+        } catch (Exception e) {
+
+        }
+        return o;
+    }
+
+    private static class A {
+        void m() throws Exception {
+            throw new Exception();
+        }
+    }
+    private static class B extends A {
+        void m() {
+        }
+    }
+    private static class C extends B {
+        void m() {
+        }
+    }
+}