8305753: Allow JIT compilation for -Xshare:dump

Reviewed-by: dholmes, matsaave, ccheung

src/hotspot/share/runtime/arguments.cpp

@@ -131,6 +131,9 @@ char* Arguments::_ext_dirs = nullptr;
 // True if -Xshare:auto option was specified.
 static bool xshare_auto_cmd_line = false;
 
+// True if -Xint/-Xmixed/-Xcomp were specified
+static bool mode_flag_cmd_line = false;
+
 bool PathString::set_value(const char *value, AllocFailType alloc_failmode) {
   char* new_value = AllocateHeap(strlen(value)+1, mtArguments, alloc_failmode);
   if (new_value == nullptr) {
@@ -2600,13 +2603,16 @@ jint Arguments::parse_each_vm_init_arg(const JavaVMInitArgs* args, bool* patch_m
     // -Xint
     } else if (match_option(option, "-Xint")) {
           set_mode_flags(_int);
+          mode_flag_cmd_line = true;
     // -Xmixed
     } else if (match_option(option, "-Xmixed")) {
           set_mode_flags(_mixed);
+          mode_flag_cmd_line = true;
     // -Xcomp
     } else if (match_option(option, "-Xcomp")) {
       // for testing the compiler; turn off all flags that inhibit compilation
           set_mode_flags(_comp);
+          mode_flag_cmd_line = true;
     // -Xshare:dump
     } else if (match_option(option, "-Xshare:dump")) {
       DumpSharedSpaces = true;
@@ -3031,14 +3037,18 @@ jint Arguments::finalize_vm_init_args(bool patch_mod_javabase) {
 
 #if INCLUDE_CDS
   if (DumpSharedSpaces) {
-    // Compiler threads may concurrently update the class metadata (such as method entries), so it's
-    // unsafe with -Xshare:dump (which modifies the class metadata in place). Let's disable
-    // compiler just to be safe.
-    //
-    // Note: this is not a concern for dynamically dumping shared spaces, which makes a copy of the
-    // class metadata instead of modifying them in place. The copy is inaccessible to the compiler.
-    // TODO: revisit the following for the static archive case.
-    set_mode_flags(_int);
+    if (!mode_flag_cmd_line) {
+      // By default, -Xshare:dump runs in interpreter-only mode, which is required for deterministic archive.
+      //
+      // If your classlist is large and you don't care about deterministic dumping, you can use
+      // -Xshare:dump -Xmixed to improve dumping speed.
+      set_mode_flags(_int);
+    } else if (_mode == _comp) {
+      // -Xcomp may use excessive CPU for the test tiers. Also, -Xshare:dump runs a small and fixed set of
+      // Java code, so there's not much benefit in running -Xcomp.
+      log_info(cds)("reduced -Xcomp to -Xmixed for static dumping");
+      set_mode_flags(_mixed);
+    }
 
     // String deduplication may cause CDS to iterate the strings in different order from one
     // run to another which resulting in non-determinstic CDS archives.

src/java.base/share/man/java.1

@@ -5069,6 +5069,18 @@ The output of this command should contain the following text:
 \f[V][info][class,load] test.Hello source: shared objects file\f[R]
 .RE
 .RE
+.PP
+By default, when the \f[V]-Xshare:dump\f[R] option is used, the JVM runs
+in interpreter-only mode (as if the \f[V]-Xint\f[R] option were
+specified).
+This is required for generating deterministic output in the shared
+archive file.
+I.e., the exact same archive will be generated, bit-for-bit, every time
+you dump it.
+However, if deterministic output is not needed, and you have a large
+classlist, you can explicitly add \f[V]-Xmixed\f[R] to the command-line
+to enable the JIT compiler.
+This will speed up the archive creation.
 .SS Creating a Dynamic CDS Archive File with -XX:ArchiveClassesAtExit
 .PP
 Advantages of dynamic CDS archives are:

test/hotspot/jtreg/runtime/cds/DeterministicDump.java

@@ -79,6 +79,7 @@ public class DeterministicDump {
         String archiveName = logName + ".jsa";
         String mapName = logName + ".map";
         CDSOptions opts = (new CDSOptions())
+            .addPrefix("-Xint") // Override any -Xmixed/-Xcomp flags from jtreg -vmoptions
             .addPrefix("-Xlog:cds=debug")
             .addPrefix("-Xlog:cds+map*=trace:file=" + mapName + ":none:filesize=0")
             .setArchiveName(archiveName)

test/hotspot/jtreg/runtime/cds/appcds/CommandLineFlagCombo.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 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
@@ -59,7 +59,10 @@ public class CommandLineFlagCombo {
         "-XX:+UseCompressedOops",
         "-XX:ObjectAlignmentInBytes=16",
         "-XX:ObjectAlignmentInBytes=32",
-        "-XX:ObjectAlignmentInBytes=64"
+        "-XX:ObjectAlignmentInBytes=64",
+        "-Xint",
+        "-Xmixed",
+        "-Xcomp",
     };
 
     public static void main(String[] args) throws Exception {