8327156: Avoid copying in StringTable::intern(oop, TRAPS)

8326865: Avoid copying in StringTable::intern(Symbol*, TRAPS)
8327825: StringTable::intern is slow

Reviewed-by: dholmes, coleenp, jsjolen

Author: caspernorrbin

src/hotspot/share/classfile/javaClasses.cpp

@@ -347,7 +347,7 @@ Handle java_lang_String::create_from_str(const char* utf8_str, TRAPS) {
 #ifdef ASSERT
   // This check is too strict when the input string is not a valid UTF8.
   // For example, it may be created with arbitrary content via jni_NewStringUTF.
-  if (UTF8::is_legal_utf8((const unsigned char*)utf8_str, strlen(utf8_str), false)) {
+  if (UTF8::is_legal_utf8((const unsigned char*)utf8_str, strlen(utf8_str), /*version_leq_47*/false)) {
     ResourceMark rm;
     const char* expected = utf8_str;
     char* actual = as_utf8_string(h_obj());
@@ -365,7 +365,7 @@ oop java_lang_String::create_oop_from_str(const char* utf8_str, TRAPS) {
   return h_obj();
 }
 
-Handle java_lang_String::create_from_symbol(Symbol* symbol, TRAPS) {
+Handle java_lang_String::create_from_symbol(const Symbol* symbol, TRAPS) {
   const char* utf8_str = (char*)symbol->bytes();
   int utf8_len = symbol->utf8_length();
 
@@ -389,6 +389,8 @@ Handle java_lang_String::create_from_symbol(Symbol* symbol, TRAPS) {
   }
 
 #ifdef ASSERT
+  // This check is too strict on older classfile versions
+  if (UTF8::is_legal_utf8((const unsigned char*)utf8_str, utf8_len, /*version_leq_47*/false))
   {
     ResourceMark rm;
     const char* expected = symbol->as_utf8();
@@ -755,6 +757,35 @@ bool java_lang_String::equals(oop java_string, const jchar* chars, int len) {
   return true;
 }
 
+bool java_lang_String::equals(oop java_string, const char* utf8_string, size_t utf8_len) {
+  assert(java_string->klass() == vmClasses::String_klass(),
+         "must be java_string");
+  typeArrayOop value = java_lang_String::value_no_keepalive(java_string);
+  int length = java_lang_String::length(java_string, value);
+  int unicode_length = UTF8::unicode_length(utf8_string, utf8_len);
+  if (length != unicode_length) {
+    return false;
+  }
+  bool is_latin1 = java_lang_String::is_latin1(java_string);
+  jchar c;
+  if (!is_latin1) {
+    for (int i = 0; i < unicode_length; i++) {
+      utf8_string = UTF8::next(utf8_string, &c);
+      if (value->char_at(i) != c) {
+        return false;
+      }
+    }
+  } else {
+    for (int i = 0; i < unicode_length; i++) {
+      utf8_string = UTF8::next(utf8_string, &c);
+      if ((((jchar) value->byte_at(i)) & 0xff) != c) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
 bool java_lang_String::equals(oop str1, oop str2) {
   assert(str1->klass() == vmClasses::String_klass(),
          "must be java String");

src/hotspot/share/classfile/javaClasses.hpp

@@ -32,6 +32,7 @@
 #include "runtime/handles.hpp"
 #include "runtime/os.hpp"
 #include "utilities/macros.hpp"
+#include "utilities/utf8.hpp"
 #include "utilities/vmEnums.hpp"
 
 class JvmtiThreadState;
@@ -99,7 +100,7 @@ class java_lang_String : AllStatic {
   static oop    create_oop_from_unicode(const jchar* unicode, int len, TRAPS);
   static Handle create_from_str(const char* utf8_str, TRAPS);
   static oop    create_oop_from_str(const char* utf8_str, TRAPS);
-  static Handle create_from_symbol(Symbol* symbol, TRAPS);
+  static Handle create_from_symbol(const Symbol* symbol, TRAPS);
   static Handle create_from_platform_dependent_str(const char* str, TRAPS);
 
   static void set_compact_strings(bool value);
@@ -180,10 +181,24 @@ class java_lang_String : AllStatic {
     return h;
   }
 
+  static unsigned int hash_code(const char* utf8_str, size_t utf8_len) {
+    unsigned int h = 0;
+    int unicode_length = UTF8::unicode_length(utf8_str, utf8_len);
+
+    jchar c;
+    while (unicode_length-- > 0) {
+      utf8_str = UTF8::next(utf8_str, &c);
+      h = 31 * h + ((unsigned int)c);
+    }
+    return h;
+  }
+
   static unsigned int hash_code(oop java_string);
   static unsigned int hash_code_noupdate(oop java_string);
 
+  // Compare strings (of different types/encodings), length is the string (array) length
   static bool equals(oop java_string, const jchar* chars, int len);
+  static bool equals(oop java_string, const char* utf8_str, size_t utf8_len);
   static bool equals(oop str1, oop str2);
   static inline bool value_equals(typeArrayOop str_value1, typeArrayOop str_value2);