8356447: Change default for EagerJVMCI to true

src/hotspot/share/jvmci/jvmciCompilerToVM.cpp

@@ -3231,7 +3231,11 @@ C2V_END
 
 C2V_VMENTRY_0(jint, getCompilationActivityMode, (JNIEnv* env, jobject))
   return CompileBroker::get_compilation_activity_mode();
-}
+C2V_END
+
+C2V_VMENTRY_0(jboolean, isCompilerThread, (JNIEnv* env, jobject))
+  return thread->is_Compiler_thread();
+C2V_END
 
 #define CC (char*)  /*cast a literal from (const char*)*/
 #define FN_PTR(f) CAST_FROM_FN_PTR(void*, &(c2v_ ## f))
@@ -3396,6 +3400,7 @@ JNINativeMethod CompilerToVM::methods[] = {
   {CC "getOopMapAt",                                  CC "(" HS_METHOD2 "I[J)V",                                                            FN_PTR(getOopMapAt)},
   {CC "updateCompilerThreadCanCallJava",              CC "(Z)Z",                                                                            FN_PTR(updateCompilerThreadCanCallJava)},
   {CC "getCompilationActivityMode",                   CC "()I",                                                                             FN_PTR(getCompilationActivityMode)},
+  {CC "isCompilerThread",                             CC "()Z",                                                                             FN_PTR(isCompilerThread)},
 };
 
 int CompilerToVM::methods_count() {

src/hotspot/share/jvmci/jvmci_globals.cpp

@@ -86,6 +86,7 @@ bool JVMCIGlobals::check_jvmci_flags_are_consistent() {
       return false;
     }
     FLAG_SET_DEFAULT(EnableJVMCI, true);
+    FLAG_SET_ERGO_IF_DEFAULT(EagerJVMCI, true);
   }
 
   if (EnableJVMCI) {

src/hotspot/share/jvmci/jvmci_globals.hpp

@@ -88,7 +88,8 @@ class fileStream;
           "-XX:-TieredCompilation makes JVMCI compile more of itself.")     \
                                                                             \
   product(bool, EagerJVMCI, false, EXPERIMENTAL,                            \
-          "Force eager JVMCI initialization")                               \
+          "Force eager JVMCI initialization. Defaults to true if "          \
+          "UseJVMCICompiler is true.")                                      \
                                                                             \
   product(bool, PrintBootstrap, true, EXPERIMENTAL,                         \
           "Print JVMCI bootstrap progress and summary")                     \

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/CompilerToVM.java

@@ -1528,4 +1528,9 @@ void getOopMapAt(HotSpotResolvedJavaMethodImpl method, int bci, long[] oopMap) {
      * {@code stop_compilation = 0}, {@code run_compilation = 1} or {@code shutdown_compilation = 2}
      */
     native int getCompilationActivityMode();
+
+    /**
+     * Returns whether the current thread is a CompilerThread.
+     */
+    native boolean isCompilerThread();
 }

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotJVMCICompilerConfig.java

@@ -51,11 +51,27 @@ private static class DummyCompilerFactory implements JVMCICompilerFactory, JVMCI
         DummyCompilerFactory(String reason, HotSpotJVMCIRuntime runtime) {
             this.reason = reason;
             this.runtime = runtime;
+            if (runtime.getConfig().getFlag("EagerJVMCI", Boolean.class)) {
+                if (runtime.getCompilerToVM().isCompilerThread()) {
+                    throw noCompilerError();
+                } else {
+                    // This path will be taken when initializing JVMCI on a non-JIT thread.
+                    // Such a usage of JVMCI might never request a compilation so delay the
+                    // noCompilerError until such a request is made.
+                }
+            }
+        }
+
+        /**
+         * Exits the VM due to unavailability of a JVMCI compiler.
+         */
+        Error noCompilerError() {
+            throw runtime.exitHotSpotWithMessage(1, "Cannot use JVMCI compiler: %s%n", reason);
         }
 
         @Override
         public HotSpotCompilationRequestResult compileMethod(CompilationRequest request) {
-            throw runtime.exitHotSpotWithMessage(1, "Cannot use JVMCI compiler: %s%n", reason);
+            throw noCompilerError();
         }
 
         @Override

test/hotspot/jtreg/compiler/jvmci/TestJVMCIPrintProperties.java

@@ -45,6 +45,7 @@ static void test(String enableFlag) throws Exception {
         ProcessBuilder pb = ProcessTools.createLimitedTestJavaProcessBuilder(
             "-XX:+UnlockExperimentalVMOptions",
             enableFlag, "-Djvmci.Compiler=null",
+            "-XX:-EagerJVMCI",
             "-XX:+JVMCIPrintProperties");
         OutputAnalyzer output = new OutputAnalyzer(pb.start());
         output.shouldContain("[JVMCI properties]"); // expected message