8231405: [Shenandoah] guarantee(d != NULL) failed: Null dominator info

Reviewed-by: shade, rkennke

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

@@ -1272,6 +1272,18 @@ void ShenandoahBarrierC2Support::pin_and_expand(PhaseIdealLoop* phase) {
     }
     if ((ctrl->is_Proj() && ctrl->in(0)->is_CallJava()) || ctrl->is_CallJava()) {
       CallNode* call = ctrl->is_Proj() ? ctrl->in(0)->as_CallJava() : ctrl->as_CallJava();
+      if (call->entry_point() == OptoRuntime::rethrow_stub()) {
+        // The rethrow call may have too many projections to be
+        // properly handled here. Given there's no reason for a
+        // barrier to depend on the call, move it above the call
+        if (phase->get_ctrl(val) == ctrl) {
+          assert(val->Opcode() == Op_DecodeN, "unexpected node");
+          assert(phase->is_dominator(phase->get_ctrl(val->in(1)), call->in(0)), "Load is too low");
+          phase->set_ctrl(val, call->in(0));
+        }
+        phase->set_ctrl(lrb, call->in(0));
+        continue;
+      }
       CallProjections projs;
       call->extract_projections(&projs, false, false);
 

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

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2019, 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 8231405
+ * @summary barrier expansion breaks if barrier is right after call to rethrow stub
+ * @key gc
+ * @requires vm.gc.Shenandoah & !vm.graal.enabled
+ *
+ * @run main/othervm -XX:CompileOnly=CallMultipleCatchProjs::test -Xcomp -Xverify:none -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC CallMultipleCatchProjs
+ *
+ */
+
+public class CallMultipleCatchProjs {
+    private static A field = new A();
+
+    public static void main(String[] args) throws Exception {
+        Exception3 exception3 = new Exception3();
+        test(new Exception2());
+    }
+
+    static int test(Exception exception) throws Exception {
+        try {
+            throw exception;
+        } catch (Exception1 e1) {
+            return 1;
+        } catch (Exception2 e2) {
+            return field.i + 2;
+        } catch (Exception3 e3) {
+            return field.i + 3;
+        }
+    }
+
+    private static class Exception1 extends Exception {
+    }
+
+    private static class Exception2 extends Exception {
+    }
+
+    private static class Exception3 extends Exception {
+    }
+
+    private static class A {
+        public int i;
+    }
+}