# HG changeset patch
# User redestad
# Date 1489529932 -3600
#      Tue Mar 14 23:18:52 2017 +0100
# Node ID 6d4a6bd80b6045a53a06854bdf2e1e0103db64c3
# Parent  191ffbdb3d7b734288daa7fb76b37a0a85dfe7eb
8176593: Throwable::getStackTrace performance regression
Reviewed-by: jiangli, iklam, coleenp, sspitsyn

diff --git a/src/share/vm/classfile/stringTable.cpp b/src/share/vm/classfile/stringTable.cpp
--- a/src/share/vm/classfile/stringTable.cpp
+++ b/src/share/vm/classfile/stringTable.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2017, 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
@@ -96,10 +96,14 @@
 
 // Pick hashing algorithm
 unsigned int StringTable::hash_string(const jchar* s, int len) {
-  return use_alternate_hashcode() ? AltHashing::murmur3_32(seed(), s, len) :
+  return use_alternate_hashcode() ? alt_hash_string(s, len) :
                                     java_lang_String::hash_code(s, len);
 }
 
+unsigned int StringTable::alt_hash_string(const jchar* s, int len) {
+  return AltHashing::murmur3_32(seed(), s, len);
+}
+
 unsigned int StringTable::hash_string(oop string) {
   EXCEPTION_MARK;
   if (string == NULL) {
@@ -117,11 +121,10 @@
   }
 }
 
-oop StringTable::lookup_shared(jchar* name, int len) {
-  // java_lang_String::hash_code() was used to compute hash values in the shared table. Don't
-  // use the hash value from StringTable::hash_string() as it might use alternate hashcode.
-  return _shared_table.lookup((const char*)name,
-                              java_lang_String::hash_code(name, len), len);
+oop StringTable::lookup_shared(jchar* name, int len, unsigned int hash) {
+  assert(hash == java_lang_String::hash_code(name, len),
+         "hash must be computed using java_lang_String::hash_code");
+  return _shared_table.lookup((const char*)name, hash, len);
 }
 
 oop StringTable::lookup_in_main_table(int index, jchar* name,
@@ -156,7 +159,7 @@
   unsigned int hashValue;
   int index;
   if (use_alternate_hashcode()) {
-    hashValue = hash_string(name, len);
+    hashValue = alt_hash_string(name, len);
     index = hash_to_index(hashValue);
   } else {
     hashValue = hashValue_arg;
@@ -199,12 +202,15 @@
 }
 
 oop StringTable::lookup(jchar* name, int len) {
-  oop string = lookup_shared(name, len);
+  // shared table always uses java_lang_String::hash_code
+  unsigned int hash = java_lang_String::hash_code(name, len);
+  oop string = lookup_shared(name, len, hash);
   if (string != NULL) {
     return string;
   }
-
-  unsigned int hash = hash_string(name, len);
+  if (use_alternate_hashcode()) {
+    hash = alt_hash_string(name, len);
+  }
   int index = the_table()->hash_to_index(hash);
   string = the_table()->lookup_in_main_table(index, name, len, hash);
 
@@ -215,12 +221,15 @@
 
 oop StringTable::intern(Handle string_or_null, jchar* name,
                         int len, TRAPS) {
-  oop found_string = lookup_shared(name, len);
+  // shared table always uses java_lang_String::hash_code
+  unsigned int hashValue = java_lang_String::hash_code(name, len);
+  oop found_string = lookup_shared(name, len, hashValue);
   if (found_string != NULL) {
     return found_string;
   }
-
-  unsigned int hashValue = hash_string(name, len);
+  if (use_alternate_hashcode()) {
+    hashValue = alt_hash_string(name, len);
+  }
   int index = the_table()->hash_to_index(hashValue);
   found_string = the_table()->lookup_in_main_table(index, name, len, hashValue);
 
diff --git a/src/share/vm/classfile/stringTable.hpp b/src/share/vm/classfile/stringTable.hpp
--- a/src/share/vm/classfile/stringTable.hpp
+++ b/src/share/vm/classfile/stringTable.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2017, 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
@@ -56,7 +56,7 @@
                 unsigned int hashValue, TRAPS);
 
   oop lookup_in_main_table(int index, jchar* chars, int length, unsigned int hashValue);
-  static oop lookup_shared(jchar* name, int len);
+  static oop lookup_shared(jchar* name, int len, unsigned int hash);
 
   // Apply the give oop closure to the entries to the buckets
   // in the range [start_idx, end_idx).
@@ -65,6 +65,13 @@
   // in the range [start_idx, end_idx).
   static void buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed);
 
+  // Hashing algorithm, used as the hash value used by the
+  //     StringTable for bucket selection and comparison (stored in the
+  //     HashtableEntry structures).  This is used in the String.intern() method.
+  static unsigned int hash_string(const jchar* s, int len);
+  static unsigned int hash_string(oop string);
+  static unsigned int alt_hash_string(const jchar* s, int len);
+
   StringTable() : RehashableHashtable<oop, mtSymbol>((int)StringTableSize,
                               sizeof (HashtableEntry<oop, mtSymbol>)) {}
 
@@ -109,12 +116,6 @@
   }
   static void possibly_parallel_oops_do(OopClosure* f);
 
-  // Hashing algorithm, used as the hash value used by the
-  //     StringTable for bucket selection and comparison (stored in the
-  //     HashtableEntry structures).  This is used in the String.intern() method.
-  static unsigned int hash_string(const jchar* s, int len);
-  static unsigned int hash_string(oop string);
-
   // Internal test.
   static void test_alt_hash() PRODUCT_RETURN;