8267399: C2: java/text/Normalizer/ConformanceTest.java test failed with assertion

Reviewed-by: kvn, neliasso

Author: rwestrel

src/hotspot/share/opto/loopTransform.cpp

@@ -2851,6 +2851,16 @@ int PhaseIdealLoop::do_range_check(IdealLoopTree *loop, Node_List &old_new) {
     register_new_node(main_cmp, main_cle->in(0));
     _igvn.replace_input_of(main_bol, 1, main_cmp);
   }
+  assert(main_limit == cl->limit() || get_ctrl(main_limit) == pre_ctrl, "wrong control for added limit");
+  const TypeInt* orig_limit_t = _igvn.type(orig_limit)->is_int();
+  bool upward = cl->stride_con() > 0;
+  // The new loop limit is <= (for an upward loop) >= (for a downward loop) than the orig limit.
+  // The expression that computes the new limit may be too complicated and the computed type of the new limit
+  // may be too pessimistic. A CastII here guarantees it's not lost.
+  main_limit = new CastIINode(main_limit, TypeInt::make(upward ? min_jint : orig_limit_t->_lo,
+                                                        upward ? orig_limit_t->_hi : max_jint, Type::WidenMax));
+  main_limit->init_req(0, pre_ctrl);
+  register_new_node(main_limit, pre_ctrl);
   // Hack the now-private loop bounds
   _igvn.replace_input_of(main_cmp, 2, main_limit);
   // The OpaqueNode is unshared by design

test/hotspot/jtreg/compiler/loopopts/TestDeadCountedLoop.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2021, Red Hat, Inc. 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 8267399
+ * @summary C2: java/text/Normalizer/ConformanceTest.java test failed with assertion
+ *
+ * @run main/othervm -XX:-TieredCompilation -XX:-BackgroundCompilation TestDeadCountedLoop
+ *
+ */
+
+public class TestDeadCountedLoop {
+    public static void main(String[] args) {
+        for (int i = 0; i < 20_000; i++) {
+            test(true, new int[10], false, 0, 1);
+            test(false, new int[10], false, 0, 1);
+        }
+    }
+
+    private static int test(boolean flag, int[] array2, boolean flag2, int start, int stop) {
+        if (array2 == null) {
+        }
+        int[] array;
+        if (flag) {
+            array = new int[1];
+        } else {
+            array = new int[2];
+        }
+        int len = array.length;
+        int v = 1;
+        for (int j = start; j < stop; j++) {
+            for (int i = 0; i < len; i++) {
+                if (i > 0) {
+                    if (flag2) {
+                        break;
+                    }
+                    v *= array2[i + j];
+                }
+            }
+        }
+
+        return v;
+    }
+}