8350971: C2: assert(idx == alias_idx) failed: Following Phi nodes should be on the same memory slice

Reviewed-by: qamai, kvn, aseoane

src/hotspot/share/opto/escape.cpp

@@ -4813,8 +4813,14 @@ void ConnectionGraph::split_unique_types(GrowableArray<Node *>  &alloc_worklist,
     if (visited.test_set(n->_idx)) {
       continue;
     }
-    if (n->is_Phi() || n->is_ClearArray()) {
-      // we don't need to do anything, but the users must be pushed
+    if (n->is_Phi()) {
+      if ((uint) _compile->get_alias_index(n->as_Phi()->adr_type()) < new_index_start) {
+        // Push memory phis on the orig_phis worklist to update
+        // during Phase 4 if needed.
+        orig_phis.append_if_missing(n->as_Phi());
+      }
+    } else if (n->is_ClearArray()) {
+     // we don't need to do anything, but the users must be pushed
     } else if (n->is_MemBar()) { // MemBar nodes
       if (!n->is_Initialize()) { // memory projections for Initialize pushed below (so we get to all their uses)
         // we don't need to do anything, but the users must be pushed

test/hotspot/jtreg/compiler/escapeAnalysis/TestMemoryPhiAlias.java

@@ -0,0 +1,72 @@
+/*
+ * 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 8350971
+ * @summary C2 compilation fails with assert(idx == alias_idx) failed: Following Phi nodes should be on the same memory slice
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:-TieredCompilation -Xbatch -XX:CompileCommand=compileonly,compiler.escapeAnalysis.TestMemoryPhiAlias::main
+ *                   compiler.escapeAnalysis.TestMemoryPhiAlias
+ */
+
+package compiler.escapeAnalysis;
+
+import java.util.function.*;
+
+public class TestMemoryPhiAlias {
+    static int[] iArrFld = new int[400];
+    static int counter = 0;
+    static int doWork() {
+        int[] more = {94};
+        java.util.function.Predicate<Integer> check = m -> m == 0;
+        java.util.function.IntConsumer decrement = x -> more[0]--;
+        java.util.function.BooleanSupplier innerLoop = () -> {
+            while (!check.test(more[0])) {
+                decrement.accept(0);
+            }
+            return true;
+        };
+        counter++;
+        if (counter == 10000000) {
+            throw new RuntimeException("excepted");
+        }
+        innerLoop.getAsBoolean();
+        java.util.function.BooleanSupplier process = () -> check.test(more[0]);
+        while (!process.getAsBoolean()) {
+        }
+        return 0;
+    }
+
+    public static void main(String[] strArr) {
+        int i14 = 1;
+        do {
+            iArrFld[i14] = 211;
+            for (int i15 = 1; i15 < 4; ++i15)
+                try {
+                    TestMemoryPhiAlias.doWork();
+                } catch (RuntimeException e) {
+                    return;
+                }
+        } while (i14 < 5);
+    }
+}