8355230: Crash in fuzzer tests: assert(n != nullptr) failed: must not be null

Reviewed-by: thartmann, epeter

Author: rwestrel

src/hotspot/share/opto/node.cpp

@@ -3120,7 +3120,7 @@ void TypeNode::make_paths_from_here_dead(PhaseIterGVN* igvn, PhaseIdealLoop* loo
         assert(r->is_Region() || r->is_top(), "unexpected Phi's control");
         if (r->is_Region()) {
           for (uint j = 1; j < u->req(); ++j) {
-            if (u->in(j) == n) {
+            if (u->in(j) == n && r->in(j) != nullptr) {
               make_path_dead(igvn, loop, r, j, phase_str);
             }
           }

test/hotspot/jtreg/compiler/c2/TestNullRegionInputAtPhiMakePathDead.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2025, 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 8355230
+ * @summary Crash in fuzzer tests: assert(n != nullptr) failed: must not be null
+ * @run main/othervm -XX:CompileCommand=compileonly,TestNullRegionInputAtPhiMakePathDead::* -Xcomp TestNullRegionInputAtPhiMakePathDead
+ */
+
+public class TestNullRegionInputAtPhiMakePathDead {
+
+    public static long instanceCount=-37082278491330812L;
+    public static float fFld=1.509F;
+    public static int iFld=89;
+
+    public static long vMeth_check_sum = 0;
+
+    public void mainTest() {
+
+        int i19, i20=13736, i21, i24=5;
+        boolean b2=true;
+
+        double d;
+        int i3;
+
+        for (d = 5; d < 131; ++d) {
+            i3 = 12;
+            while (--i3 > 0) {
+                TestNullRegionInputAtPhiMakePathDead.fFld *= -31237;
+            }
+        }
+        TestNullRegionInputAtPhiMakePathDead.fFld %= 16334;
+        TestNullRegionInputAtPhiMakePathDead.instanceCount = 0;
+        for (i19 = 2; i19 < 281; i19++) {
+            try {
+                TestNullRegionInputAtPhiMakePathDead.iFld = (57 % i20);
+            } catch (ArithmeticException a_e) {}
+            i20 += (((i19 * TestNullRegionInputAtPhiMakePathDead.fFld) + TestNullRegionInputAtPhiMakePathDead.instanceCount) - i19);
+            for (i21 = i19; i21 < 90; i21++) {
+                if (b2) {
+                } else {
+                    // CastII of b2 to false added here becomes top during igvn. It's used by a Phi
+                    // at a Region that merges paths from the switch and if. Some of those paths are
+                    // found unreachable at parse time but added to the Region anyway.
+                    switch ((((i21 >>> 1) % 4) * 5) + 115) {
+                    case 129:
+                        break;
+                    case 135:
+                        i24 |= i24;
+                    }
+                }
+            }
+        }
+
+        System.out.println("vMeth_check_sum: " + vMeth_check_sum);
+    }
+    public static void main(String[] strArr) {
+        try {
+            TestNullRegionInputAtPhiMakePathDead _instance = new TestNullRegionInputAtPhiMakePathDead();
+            for (int i = 0; i < 10; i++ ) {
+                _instance.mainTest();
+            }
+         } catch (Exception ex) {
+         }
+    }
+}