8359602: Ideal optimizations depending on input type are missed because of missing notification mechanism from CCP

Reviewed-by: epeter, thartmann

Author: benoitmaillard

src/hotspot/share/opto/phaseX.cpp

@@ -3121,6 +3121,7 @@ Node *PhaseCCP::transform_once( Node *n ) {
     hash_delete(n);             // changing bottom type may force a rehash
     n->raise_bottom_type(t);
     _worklist.push(n);          // n re-enters the hash table via the worklist
+    add_users_to_worklist(n);   // if ideal or identity optimizations depend on the input type, users need to be notified
   }
 
   // TEMPORARY fix to ensure that 2nd GVN pass eliminates null checks

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

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2025, 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 8359602
+ * @summary The control input of a ModI node should be discarded if it is
+ *          possible to prove that the divisor can never be 0.
+ *          VerifyIterativeGVN checks that this optimization was applied
+ * @run main/othervm -XX:CompileCommand=quiet -XX:-TieredCompilation
+ *      -XX:+UnlockDiagnosticVMOptions -Xcomp -XX:+IgnoreUnrecognizedVMOptions
+ *      -XX:CompileCommand=compileonly,compiler.c2.TestModControlFoldedAfterCCP::test
+ *      -XX:VerifyIterativeGVN=1110 compiler.c2.TestModControlFoldedAfterCCP
+ * @run main compiler.c2.TestModControlFoldedAfterCCP
+ *
+ */
+
+package compiler.c2;
+
+public class TestModControlFoldedAfterCCP {
+    static void test() {
+        int i22, i24 = -1191, i28;
+        int iArr1[] = new int[1];
+        for (int i = 1;i < 100; i++) {
+            for (int j = 4; j > i; j--) {
+                i22 = i24;
+
+                // divisor is either -1191 or -13957
+                iArr1[0] = 5 % i22;
+            }
+            for (i28 = i; i28 < 2; ++i28) {
+                i24 = -13957;
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        test();
+    }
+}