8249608: Vector register used by C2 compiled method corrupted at safepoint

Always update 'max_vlen_in_bytes'.

Reviewed-by: kvn, vlivanov, chagedorn

src/hotspot/share/opto/superword.cpp

@@ -2637,8 +2637,10 @@ void SuperWord::output() {
         }
       }
 
-      if (vlen_in_bytes >= max_vlen_in_bytes && vlen > max_vlen) {
+      if (vlen > max_vlen) {
         max_vlen = vlen;
+      }
+      if (vlen_in_bytes > max_vlen_in_bytes) {
         max_vlen_in_bytes = vlen_in_bytes;
       }
 #ifdef ASSERT

test/hotspot/jtreg/compiler/vectorization/TestVectorsNotSavedAtSafepoint.java

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 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 8193518 8249608
+ * @summary C2: Vector registers are sometimes corrupted at safepoint
+ * @run main/othervm -XX:-BackgroundCompilation -XX:+UseCountedLoopSafepoints -XX:LoopStripMiningIter=1000 TestVectorsNotSavedAtSafepoint test1
+ * @run main/othervm -XX:-BackgroundCompilation TestVectorsNotSavedAtSafepoint test2
+ */
+
+import java.util.Arrays;
+
+public class TestVectorsNotSavedAtSafepoint {
+
+    static void test1(byte[] barray1, byte[] barray2, byte[] barray3, long[] larray, long v) {
+        // Uses wide vectors, v in vector registers is live at the
+        // safepoint of the outer strip mined loop
+        for (int i = 0; i < larray.length; i++) {
+            larray[i] = v;
+        }
+        // Runs for few iterations so limited unrolling and short
+        // vectors
+        for (int i = 0; i < barray3.length; i++) {
+            barray3[i] = (byte)(barray1[i] + barray2[i]);
+        }
+    }
+
+    public static void test2(int[] iArr, long[] lArr) {
+        // Loop with wide and non-wide vectors
+        for (int i = 0; i < lArr.length; i++) {
+            iArr[i] = 1;
+            lArr[i] = 1;
+        }
+    }
+
+    static class GarbageProducerThread extends Thread {
+        public void run() {
+            for(;;) {
+                Object[] arrays = new Object[1024];
+                for (int i = 0; i < arrays.length; i++) {
+                    arrays[i] = new int[1024];
+                }
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        Thread garbage_producer = new GarbageProducerThread();
+        garbage_producer.setDaemon(true);
+        garbage_producer.start();
+
+        if (args[0].equals("test1")) {
+            byte[] barray = new byte[10];
+            long[] larray1 = new long[1000];
+            long[] larray2 = new long[100_000_000];
+            for (int i = 0; i < 20_000; i++) {
+                test1(barray, barray, barray, larray1, -1);
+            }
+            for (int i = 0; i < 100; i++) {
+                test1(barray, barray, barray, larray2, -1);
+                if (larray2[larray2.length-1] != -1) {
+                    System.out.println("Iter " + i + " Failed with " + Long.toHexString(larray2[larray2.length-1]));
+                    throw new RuntimeException("Test1 failed");
+                }
+            }
+        } else {
+            int iArr[] = new int[100];
+            long lArr[] = new long[100];
+            for (int i = 0; i < 600_000; ++i) {
+                test2(iArr, lArr);
+                for (int j = 0; j < lArr.length; ++j) {
+                    if (iArr[j] != 1 || lArr[j] != 1) {
+                        throw new RuntimeException("Test2 failed at iteration " + i + ": iArr[" + j + "] = " + iArr[j] + ", lArr[" + j + "] = " + lArr[j]);
+                    }
+                }
+            }
+        }
+    }
+}
+