Subject: Backport JDK-8320308 C2 compilation crashes in LibraryCallKit::inline_unsafe_access

---
 src/hotspot/share/opto/library_call.cpp       |   7 +-
 .../TestUnsafeArrayAccessWithNullBase.java    | 113 ++++++++++++++++++
 2 files changed, 117 insertions(+), 3 deletions(-)
 create mode 100644 test/hotspot/jtreg/compiler/parsing/TestUnsafeArrayAccessWithNullBase.java

diff --git a/src/hotspot/share/opto/library_call.cpp b/src/hotspot/share/opto/library_call.cpp
index af2ea6095..3ef0098c4 100644
--- a/src/hotspot/share/opto/library_call.cpp
+++ b/src/hotspot/share/opto/library_call.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2024, 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
@@ -2004,7 +2004,7 @@ LibraryCallKit::classify_unsafe_addr(Node* &base, Node* &offset, BasicType type)
   if (base_type == nullptr) {
     // Unknown type.
     return Type::AnyPtr;
-  } else if (base_type == TypePtr::NULL_PTR) {
+  } else if (_gvn.type(base->uncast()) == TypePtr::NULL_PTR) {
     // Since this is a null+long form, we have to switch to a rawptr.
     base   = _gvn.transform(new CastX2PNode(offset));
     offset = MakeConX(0);
@@ -2322,8 +2322,9 @@ bool LibraryCallKit::inline_unsafe_access(bool is_store, const BasicType type, c
   SafePointNode* old_map = clone_map();
 
   Node* adr = make_unsafe_address(base, offset, type, kind == Relaxed);
+  assert(!stopped(), "Inlining of unsafe access failed: address construction stopped unexpectedly");
 
-  if (_gvn.type(base)->isa_ptr() == TypePtr::NULL_PTR) {
+  if (_gvn.type(base->uncast())->isa_ptr() == TypePtr::NULL_PTR) {
     if (type != T_OBJECT) {
       decorators |= IN_NATIVE; // off-heap primitive access
     } else {
diff --git a/test/hotspot/jtreg/compiler/parsing/TestUnsafeArrayAccessWithNullBase.java b/test/hotspot/jtreg/compiler/parsing/TestUnsafeArrayAccessWithNullBase.java
new file mode 100644
index 000000000..28eb4f3c1
--- /dev/null
+++ b/test/hotspot/jtreg/compiler/parsing/TestUnsafeArrayAccessWithNullBase.java
@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2024, 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 8320308
+ * @summary Unsafe::getShortUnaligned with base null hidden behind CheckCastPP nodes
+ * @library /test/lib
+ * @modules java.base/jdk.internal.misc
+ * @run main/othervm -Xbatch -XX:CompileCommand=quiet -XX:TypeProfileLevel=222
+ *      -XX:+IgnoreUnrecognizedVMOptions -XX:+AlwaysIncrementalInline
+ *      -XX:CompileCommand=compileonly,compiler.parsing.TestUnsafeArrayAccessWithNullBase::test*
+ *      -XX:-TieredCompilation compiler.parsing.TestUnsafeArrayAccessWithNullBase
+ * @run main compiler.parsing.TestUnsafeArrayAccessWithNullBase
+ */
+
+package compiler.parsing;
+
+import java.lang.reflect.*;
+import jdk.internal.misc.Unsafe;
+
+public class TestUnsafeArrayAccessWithNullBase {
+
+    /*
+    Trigger bug when handling Unsafe.getShortUnaligned with null checks and inlined methods.
+    The bug appears when the method is incrementally inlined and optimized based on the argument profile information.
+
+    Warmup Phase: By warming up with non-null values, the argument profile for the helper methods records non-null types.
+        - insert CheckCastPP: speculative=byte[int:>=0] for return of getSmall/getLarge
+        - insert CheckCastPP: speculative=byte[int:>=0] for argument `Object array` in helperSmall/helperLarge
+    Trigger Phase: Calling test causes LibraryCallKit::inline_unsafe_access(..) for Unsafe::getShortUnaligned to fail:
+        Reason: UNSAFE.getShortUnaligned(array, offset) is called with array=null,
+        but ConP null is now hidden by two CheckCastPP with speculative=byte[int:>=0] in the graph
+    */
+
+    private static final Unsafe UNSAFE = Unsafe.getUnsafe();
+
+    private static final Object byteArray = new byte[1_050_000];
+
+    public static Object getLarge(boolean useNull) {
+        return useNull ? null : byteArray;
+    }
+
+    public static Object getSmall(boolean useNull) {
+        return useNull ? null : new byte[10];
+    }
+
+    // use a helper to delay inlining of UNSAFE.getShortUnaligned
+    public static int helperLarge(Object array, boolean run) {
+        // offset >= os::vm_page_size(): LibraryCallKit::classify_unsafe_addr returns Type::AnyPtr
+        return run ? UNSAFE.getShortUnaligned(array, 1_049_000) : 0; // after warmup CheckCastPP: speculative=byte[int:>=0]
+    }
+
+    public static int accessLargeArray(boolean useNull, boolean run) {
+        Object array = getLarge(useNull); // after warmup CheckCastPP: speculative=byte[int:>=0]
+        // getLarge() ensures null is only visible after helperLarge was (incrementally) inlined
+        return helperLarge(array, run);
+    }
+
+    // use a helper to delay inlining of UNSAFE.getShortUnaligned
+    // warmup adds argument profile information for array: CheckCastPP with type non null
+    public static int helperSmall(Object array, boolean run) {
+        // 0 <= offset < os::vm_page_size():  LibraryCallKit::classify_unsafe_addr returns Type::OopPtr
+        return run ? UNSAFE.getShortUnaligned(array, 1) : 0; // after warmup CheckCastPP: speculative=byte[int:>=0]
+    }
+
+    public static int accessSmallArray(boolean useNull, boolean run) {
+        Object array = getSmall(useNull); // after warmup CheckCastPP: speculative=byte[int:>=0]
+        return helperSmall(array, run);
+    }
+
+    public static int test1(boolean run) {
+        return accessLargeArray(true, run);
+    }
+
+    public static int test2(boolean run) {
+        return accessSmallArray(true, run);
+    }
+
+    public static void main(String[] args) {
+        // Warmup to collect speculative types
+        for (int i = 0; i < 10_000; i++) {
+            accessLargeArray(false, true);
+            accessSmallArray(false, true);
+        }
+
+        // Trigger Compilation
+        for (int i = 0; i < 10_000; ++i) {
+            test1(false);
+            test2(false);
+        }
+    }
+}
-- 
2.33.0