8005772: Stubs report compile id -1 in phase events

Summary: Use 0 to indicate id is NA, -1 for error or uninitalized
Reviewed-by: kvn, twisti

src/share/vm/compiler/compileBroker.cpp

@@ -505,7 +505,7 @@ void CompileTask::log_task(xmlStream* log) {
   ResourceMark rm(thread);
 
   // <task id='9' method='M' osr_bci='X' level='1' blocking='1' stamp='1.234'>
-  if (_compile_id != 0)   log->print(" compile_id='%d'", _compile_id);
+  log->print(" compile_id='%d'", _compile_id);
   if (_osr_bci != CompileBroker::standard_entry_bci) {
     log->print(" compile_kind='osr'");  // same as nmethod::compile_kind
   } // else compile_kind='c2c'

src/share/vm/opto/compile.cpp

@@ -892,7 +892,7 @@ Compile::Compile( ciEnv* ci_env,
   : Phase(Compiler),
     _env(ci_env),
     _log(ci_env->log()),
-    _compile_id(-1),
+    _compile_id(0),
     _save_argument_registers(save_arg_registers),
     _method(NULL),
     _stub_name(stub_name),