8297264: C2: Cast node is not processed again in CCP and keeps a wrong too narrow type which is later replaced by top

Reviewed-by: thartmann, rcastanedalo, kvn

src/hotspot/share/opto/phaseX.cpp

@@ -1847,6 +1847,7 @@ void PhaseCCP::push_more_uses(Unique_Node_List& worklist, Node* parent, const No
   push_counted_loop_phi(worklist, parent, use);
   push_loadp(worklist, use);
   push_and(worklist, parent, use);
+  push_cast_ii(worklist, parent, use);
 }
 
 
@@ -1950,6 +1951,22 @@ void PhaseCCP::push_and(Unique_Node_List& worklist, const Node* parent, const No
   }
 }
 
+// CastII::Value() optimizes CmpI/If patterns if the right input of the CmpI has a constant type. If the CastII input is
+// the same node as the left input into the CmpI node, the type of the CastII node can be improved accordingly. Add the
+// CastII node back to the worklist to re-apply Value() to either not miss this optimization or to undo it because it
+// cannot be applied anymore. We could have optimized the type of the CastII before but now the type of the right input
+// of the CmpI (i.e. 'parent') is no longer constant. The type of the CastII must be widened in this case.
+void PhaseCCP::push_cast_ii(Unique_Node_List& worklist, const Node* parent, const Node* use) const {
+  if (use->Opcode() == Op_CmpI && use->in(2) == parent) {
+    Node* other_cmp_input = use->in(1);
+    for (DUIterator_Fast imax, i = other_cmp_input->fast_outs(imax); i < imax; i++) {
+      Node* cast_ii = other_cmp_input->fast_out(i);
+      if (cast_ii->is_CastII()) {
+        push_if_not_bottom_type(worklist, cast_ii);
+      }
+    }
+  }
+}
 
 //------------------------------do_transform-----------------------------------
 // Top level driver for the recursive transformer

src/hotspot/share/opto/phaseX.hpp

@@ -595,6 +595,7 @@ class PhaseCCP : public PhaseIterGVN {
   void push_loadp(Unique_Node_List& worklist, const Node* use) const;
   static void push_load_barrier(Unique_Node_List& worklist, const BarrierSetC2* barrier_set, const Node* use);
   void push_and(Unique_Node_List& worklist, const Node* parent, const Node* use) const;
+  void push_cast_ii(Unique_Node_List& worklist, const Node* parent, const Node* use) const;
 
  public:
   PhaseCCP( PhaseIterGVN *igvn ); // Compute conditional constants

test/hotspot/jtreg/compiler/ccp/TestCastIIWrongTypeCCP.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2022, 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 8297264
+ * @summary Test that CastII nodes are added to the CCP worklist if they could have been
+ *          optimized due to a CmpI/If pattern.
+ * @run main/othervm -Xcomp -XX:CompileCommand=compileonly,compiler.ccp.TestCastIIWrongTypeCCP::*
+ *                   compiler.ccp.TestCastIIWrongTypeCCP
+ */
+package compiler.ccp;
+
+public class TestCastIIWrongTypeCCP {
+
+    static int x;
+
+    public static void main(String[] args) {
+        test();
+    }
+
+    static void test() {
+        int iArr[] = new int[400];
+        int i = 0;
+        do {
+            for (int i5 = 1; i5 < 4; i5++) {
+                for (int i9 = 2; i9 > i5; i9 -= 3) {
+                    if (x != 0) {
+                        A.unloaded(); // unloaded UCT
+                    }
+                    x = 1;
+                    iArr[5] = 1;
+                }
+            }
+            i++;
+        } while (i < 10000);
+    }
+}
+
+class A {
+    public static void unloaded() {
+    }
+}