8380579: C2: Intermittent fastdebug assert in Parse::sharpen_type_after_if: missing type check info

Reviewed-by: rcastanedalo, vlivanov

src/hotspot/share/opto/parse2.cpp

@@ -1757,6 +1757,12 @@ static bool match_type_check(PhaseGVN& gvn,
     //   Bool(CmpP(LoadKlass(obj._klass), ConP(Foo.klass)), [eq])
     // or the narrowOop equivalent.
     (*obj) = extract_obj_from_klass_load(&gvn, val);
+    // Some klass comparisons are not directly in the form
+    // Bool(CmpP(LoadKlass(obj._klass), ConP(Foo.klass)), [eq]),
+    // e.g. Bool(CmpP(CastPP(LoadKlass(...)), ConP(klass)), [eq]).
+    // These patterns with nullable klasses arise from example from
+    // load_array_klass_from_mirror.
+    if (*obj == nullptr) { return false; }
     (*cast_type) = tcon->isa_klassptr()->as_instance_type();
     return true; // found
   }

test/hotspot/jtreg/compiler/reflection/TestSharpenTypeAfterIfMissingTypeCheckInfo.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2026, Oracle and/or its affiliates. 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 8380579
+ * @summary Test that C2 match_type_check handles Bool(CmpP(CastPP(LoadKlass(...)), ConP(klass)), eq)
+ * @run main/othervm
+ *      -XX:-TieredCompilation
+ *      -Xcomp
+ *      -XX:CompileCommand=compileonly,${test.main.class}::test
+ *      ${test.main.class}
+ */
+
+package compiler.reflection;
+
+import java.lang.reflect.Array;
+
+public class TestSharpenTypeAfterIfMissingTypeCheckInfo {
+
+    public static void main(String[] args) {
+        for (int i = 0; i < 20_000; i++) {
+            test(i);
+        }
+    }
+
+    static boolean test(int i) {
+        Class componentType;
+        if (i % 2 == 0) {
+            componentType = Object.class;
+        } else {
+            componentType = Integer.class;
+        }
+        Object array = Array.newInstance(componentType, 1);
+        return array.getClass() == Object[].class;
+    }
+}