test/hotspot/jtreg/runtime/CompressedOops/CompressedClassPointersEncodingScheme.java

@@ -1,7 +1,7 @@
  /*
-  * Copyright (c) 2013, 2023, Oracle and/or its affiliates. All rights reserved.
+  * Copyright (c) 2013, 2024, 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.

@@ -40,17 +40,20 @@
  
  import java.io.IOException;
  
  public class CompressedClassPointersEncodingScheme {
  
-     private static void test(long forceAddress, long classSpaceSize, long expectedEncodingBase, int expectedEncodingShift) throws IOException {
+     private static void test(long forceAddress, boolean COH, long classSpaceSize, long expectedEncodingBase, int expectedEncodingShift) throws IOException {
          String forceAddressString = String.format("0x%016X", forceAddress).toLowerCase();
          String expectedEncodingBaseString = String.format("0x%016X", expectedEncodingBase).toLowerCase();
          ProcessBuilder pb = ProcessTools.createLimitedTestJavaProcessBuilder(
                  "-Xshare:off", // to make CompressedClassSpaceBaseAddress work
                  "-XX:+UnlockDiagnosticVMOptions",
                  "-XX:-UseCompressedOops", // keep VM from optimizing heap location
+                 "-XX:+UnlockExperimentalVMOptions",
+                 "-XX:" + (COH ? "+" : "-") + "UseCompactObjectHeaders",
+                 "-XX:" + (COH ? "+" : "-") + "UseObjectMonitorTable",
                  "-XX:CompressedClassSpaceBaseAddress=" + forceAddress,
                  "-XX:CompressedClassSpaceSize=" + classSpaceSize,
                  "-Xmx128m",
                  "-Xlog:metaspace*",
                  "-version");

@@ -58,11 +61,12 @@
  
          output.reportDiagnosticSummary();
  
          // We ignore cases where we were not able to map at the force address
          if (output.contains("reserving class space failed")) {
-             throw new SkippedException("Skipping because we cannot force ccs to " + forceAddressString);
+             System.out.println("Skipping because we cannot force ccs to " + forceAddressString);
+             return;
          }
  
          output.shouldHaveExitValue(0);
          output.shouldContain("Narrow klass base: " + expectedEncodingBaseString + ", Narrow klass shift: " + expectedEncodingShift);
      }

@@ -71,11 +75,51 @@
      final static long M = K * 1024;
      final static long G = M * 1024;
      public static void main(String[] args) throws Exception {
          // Test ccs nestling right at the end of the 4G range
          // Expecting base=0, shift=0
-         test(4 * G - 128 * M, 128 * M, 0, 0);
+         test(4 * G - 128 * M, false, 128 * M, 0, 0);
  
+         // Test ccs nestling right at the end of the 32G range
+         // Expecting:
+         // - non-aarch64: base=0, shift=3
+         // - aarch64: base to start of class range, shift 0
+         if (Platform.isAArch64()) {
+             // The best we can do on aarch64 is to be *near* the end of the 32g range, since a valid encoding base
+             // on aarch64 must be 4G aligned, and the max. class space size is 3G.
+             long forceAddress = 0x7_0000_0000L; // 28g, and also a valid EOR immediate
+             test(forceAddress, false, 3 * G, forceAddress, 0);
+         } else {
+             test(32 * G - 128 * M, false, 128 * M, 0, 3);
+         }
+ 
+         // Test ccs starting *below* 4G, but extending upwards beyond 4G. All platforms except aarch64 should pick
+         // zero based encoding.
+         if (Platform.isAArch64()) {
+             long forceAddress = 0xC000_0000L; // make sure we have a valid EOR immediate
+             test(forceAddress, false, G + (128 * M), forceAddress, 0);
+         } else {
+             test(4 * G - 128 * M, false, 2 * 128 * M, 0, 3);
+         }
          // add more...
  
+         // Compact Object Header Mode with tiny classpointers
+         // On all platforms we expect the VM to chose the smallest possible shift value needed to cover the encoding range
+         long forceAddress = 30 * G;
+ 
+         long ccsSize = 128 * M;
+         int expectedShift = 6;
+         test(forceAddress, true, ccsSize, forceAddress, expectedShift);
+ 
+         ccsSize = 512 * M;
+         expectedShift = 8;
+         test(forceAddress, true, ccsSize, forceAddress, expectedShift);
+ 
+         ccsSize = G;
+         expectedShift = 9;
+         test(forceAddress, true, ccsSize, forceAddress, expectedShift);
+ 
+         ccsSize = 3 * G;
+         expectedShift = 10;
+         test(forceAddress, true, ccsSize, forceAddress, expectedShift);
      }
  }