8303466: C2: failed: malformed control flow. Limit type made precise with MaxL/MinL

Reviewed-by: roland
Backport-of: cc894d849aa5f730d5a806acfc7a237cf5170af1

Author: martinuy

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

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2023, 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 id=test1
+ * @bug 8298935
+ * @summary CMoveI for underflow protection of the limit did not compute a type that was precise enough.
+ *          This lead to dead data but zero-trip-guard control did not die -> "malformed control flow".
+ * @requires vm.compiler2.enabled
+ * @run main/othervm
+ *      -XX:CompileCommand=compileonly,compiler.loopopts.TestUnrollLimitPreciseType::test1
+ *      -XX:CompileCommand=dontinline,compiler.loopopts.TestUnrollLimitPreciseType::*
+ *      -XX:MaxVectorSize=64
+ *      -Xcomp
+ *      -XX:+UnlockExperimentalVMOptions -XX:PerMethodSpecTrapLimit=0 -XX:PerMethodTrapLimit=0
+ *      compiler.loopopts.TestUnrollLimitPreciseType test1
+ */
+
+/*
+ * @test id=test2
+ * @bug 8298935
+ * @summary CMoveI for underflow protection of the limit did not compute a type that was precise enough.
+ *          This lead to dead data but zero-trip-guard control did not die -> "malformed control flow".
+ * @requires vm.compiler2.enabled
+ * @run main/othervm
+ *      -XX:CompileCommand=compileonly,compiler.loopopts.TestUnrollLimitPreciseType::*
+ *      -Xcomp
+ *      compiler.loopopts.TestUnrollLimitPreciseType test2
+ */
+
+
+package compiler.loopopts;
+
+public class TestUnrollLimitPreciseType {
+    static final int RANGE = 512;
+
+    public static void main(String args[]) {
+        if (args.length != 1) {
+            throw new RuntimeException("Need exactly one argument.");
+        }
+        if (args[0].equals("test1")) {
+            byte[] data = new byte[RANGE];
+            test1(data);
+        } else if (args[0].equals("test2")) {
+            test2();
+        } else {
+            throw new RuntimeException("Do not have: " + args[0]);
+        }
+    }
+
+    public static void test1(byte[] data) {
+        // Did not fully analyze this. But it is also unrolled, SuperWorded,
+        // and further unrolled with vectorlized post loop.
+        // Only seems to reproduce with avx512, and not with avx2.
+        for (int j = 192; j < RANGE; j++) {
+            data[j - 192] = (byte)(data[j] * 11);
+        }
+    }
+
+    static void test2() {
+        // Loop is SuperWord'ed.
+        // We unroll more afterwards, and so add vectorized post loop.
+        // But it turns out that the vectorized post loop is never entered.
+        // This lead to assert, because the zero-trip-guard did not collaspse,
+        // but the CastII with the trip count did die.
+        // Only seems to reproduce with avx512, and not with avx2.
+        double dArr[][] = new double[100][100];
+        for (int i = 2, j = 2; j < 68; j++) {
+            dArr[i][j] = 8;
+        }
+    }
+}