From c1d5b7c044ba418848c98d36ec21358a1dac568e Mon Sep 17 00:00:00 2001
Date: Sat, 23 May 2020 17:18:39 +0800
Subject: [PATCH] 8223504:improve performance of forall loops by better
 inlining of "iterator()" methods

Summary: <C2>  : improve performance of forall loops by better inlining of "iterator()" methods
LLT: NA
Bug url: https://bugs.openjdk.java.net/browse/JDK-8223504
---
 hotspot/src/share/vm/classfile/systemDictionary.hpp | 3 +++
 hotspot/src/share/vm/classfile/vmSymbols.hpp        | 2 ++
 hotspot/src/share/vm/opto/bytecodeInfo.cpp          | 9 ++++++++-
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/hotspot/src/share/vm/classfile/systemDictionary.hpp b/hotspot/src/share/vm/classfile/systemDictionary.hpp
index 57a9d669b..956b50313 100644
--- a/hotspot/src/share/vm/classfile/systemDictionary.hpp
+++ b/hotspot/src/share/vm/classfile/systemDictionary.hpp
@@ -196,6 +196,9 @@ class Ticks;
   do_klass(Short_klass,                                 java_lang_Short,                           Pre                 ) \
   do_klass(Integer_klass,                               java_lang_Integer,                         Pre                 ) \
   do_klass(Long_klass,                                  java_lang_Long,                            Pre                 ) \
+                                                                                                                         \
+  /* force inline of iterators */                                                                                        \
+  do_klass(Iterator_klass,                              java_util_Iterator,                        Pre                 ) \
   /*end*/
 
 
diff --git a/hotspot/src/share/vm/classfile/vmSymbols.hpp b/hotspot/src/share/vm/classfile/vmSymbols.hpp
index 46f2e2d8b..acc33fcc2 100644
--- a/hotspot/src/share/vm/classfile/vmSymbols.hpp
+++ b/hotspot/src/share/vm/classfile/vmSymbols.hpp
@@ -121,6 +121,8 @@
   template(sun_misc_Launcher_AppClassLoader,          "sun/misc/Launcher$AppClassLoader")         \
   template(sun_misc_Launcher_ExtClassLoader,          "sun/misc/Launcher$ExtClassLoader")         \
                                                                                                   \
+  template(java_util_Iterator,                        "java/util/Iterator")                       \
+                                                                                                  \
   /* Java runtime version access */                                                               \
   template(sun_misc_Version,                          "sun/misc/Version")                         \
   template(java_runtime_name_name,                    "java_runtime_name")                        \
diff --git a/hotspot/src/share/vm/opto/bytecodeInfo.cpp b/hotspot/src/share/vm/opto/bytecodeInfo.cpp
index d16b5631b..06a30b94a 100644
--- a/hotspot/src/share/vm/opto/bytecodeInfo.cpp
+++ b/hotspot/src/share/vm/opto/bytecodeInfo.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2020, 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
@@ -75,6 +75,8 @@ InlineTree::InlineTree(Compile* c,
  *  Return true when EA is ON and a java constructor is called or
  *  a super constructor is called from an inlined java constructor.
  *  Also return true for boxing methods.
+ *  Also return true for methods returning Iterator (including Iterable::iterator())
+ *  that is essential for forall-loops performance.
  */
 static bool is_init_with_ea(ciMethod* callee_method,
                             ciMethod* caller_method, Compile* C) {
@@ -92,6 +94,11 @@ static bool is_init_with_ea(ciMethod* callee_method,
   if (C->eliminate_boxing() && callee_method->is_boxing_method()) {
     return true;
   }
+  ciType *retType = callee_method->signature()->return_type();
+  ciKlass *iter = C->env()->Iterator_klass();
+  if (retType->is_loaded() && iter->is_loaded() && retType->is_subtype_of(iter)) {
+    return true;
+  }
   return false;
 }
 
-- 
2.19.1