7167142: Consider a warning when finding a .hotspotrc or .hotspot_compiler file that isn't used

Summary: Send warnings to output stream
Reviewed-by: dholmes, fparain

src/share/vm/compiler/compilerOracle.cpp

@@ -550,10 +550,12 @@ void CompilerOracle::parse_from_line(char* line) {
   }
 }
 
+static const char* default_cc_file = ".hotspot_compiler";
+
 static const char* cc_file() {
 #ifdef ASSERT
   if (CompileCommandFile == NULL)
-    return ".hotspot_compiler";
+    return default_cc_file;
 #endif
   return CompileCommandFile;
 }
@@ -636,10 +638,17 @@ void compilerOracle_init() {
   CompilerOracle::parse_from_string(CompileOnly, CompilerOracle::parse_compile_only);
   if (CompilerOracle::has_command_file()) {
     CompilerOracle::parse_from_file();
+  } else {
+    struct stat buf;
+    if (os::stat(default_cc_file, &buf) == 0) {
+      warning("%s file is present but has been ignored.  "
+              "Run with -XX:CompileCommandFile=%s to load the file.",
+              default_cc_file, default_cc_file);
+    }
   }
   if (lists[PrintCommand] != NULL) {
     if (PrintAssembly) {
-      warning("CompileCommand and/or .hotspot_compiler file contains 'print' commands, but PrintAssembly is also enabled");
+      warning("CompileCommand and/or %s file contains 'print' commands, but PrintAssembly is also enabled", default_cc_file);
     } else if (FLAG_IS_DEFAULT(DebugNonSafepoints)) {
       warning("printing of assembly code is enabled; turning on DebugNonSafepoints to gain additional output");
       DebugNonSafepoints = true;

src/share/vm/runtime/arguments.cpp

@@ -2971,7 +2971,10 @@ jint Arguments::parse(const JavaVMInitArgs* args) {
   const char* tail;
 
   // If flag "-XX:Flags=flags-file" is used it will be the first option to be processed.
+  const char* hotspotrc = ".hotspotrc";
   bool settings_file_specified = false;
+  bool needs_hotspotrc_warning = false;
+
   const char* flags_file;
   int index;
   for (index = 0; index < args->nOptions; index++) {
@@ -3015,16 +3018,19 @@ jint Arguments::parse(const JavaVMInitArgs* args) {
     if (!process_settings_file(flags_file, true, args->ignoreUnrecognized)) {
       return JNI_EINVAL;
     }
-  }
-
+  } else {
 #ifdef ASSERT
-  // Parse default .hotspotrc settings file
-  if (!settings_file_specified) {
+    // Parse default .hotspotrc settings file
     if (!process_settings_file(".hotspotrc", false, args->ignoreUnrecognized)) {
       return JNI_EINVAL;
     }
-  }
+#else
+    struct stat buf;
+    if (os::stat(hotspotrc, &buf) == 0) {
+      needs_hotspotrc_warning = true;
+    }
 #endif
+  }
 
   if (PrintVMOptions) {
     for (index = 0; index < args->nOptions; index++) {
@@ -3041,6 +3047,14 @@ jint Arguments::parse(const JavaVMInitArgs* args) {
     return result;
   }
 
+  // Delay warning until here so that we've had a chance to process
+  // the -XX:-PrintWarnings flag
+  if (needs_hotspotrc_warning) {
+    warning("%s file is present but has been ignored.  "
+            "Run with -XX:Flags=%s to load the file.",
+            hotspotrc, hotspotrc);
+  }
+
 #if (defined JAVASE_EMBEDDED || defined ARM)
   UNSUPPORTED_OPTION(UseG1GC, "G1 GC");
 #endif