--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/prims/jniFastGetField.hpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,94 @@
+/*
+ * Copyright 2004 Sun Microsystems, Inc.  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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// Basic logic of a fast version of jni_Get<Primitive>Field:
+//
+// (See safepoint.hpp for a description of _safepoint_counter)
+//
+// load _safepoint_counter into old_counter
+// IF old_counter is odd THEN
+//   a safepoint is going on, return jni_GetXXXField
+// ELSE
+//   load the primitive field value into result (speculatively)
+//   load _safepoint_counter into new_counter
+//   IF (old_counter == new_counter) THEN
+//     no safepoint happened during the field access, return result
+//   ELSE
+//     a safepoint might have happened in-between, return jni_GetXXXField()
+//   ENDIF
+// ENDIF
+//
+// LoadLoad membars to maintain the load order may be necessary
+// for some platforms.
+//
+// The fast versions don't check for pending suspension request.
+// This is fine since it's totally read-only and doesn't create new race.
+//
+// There is a hypothetical safepoint counter wraparound. But it's not
+// a practical concern.
+
+class JNI_FastGetField : AllStatic {
+ private:
+  enum { LIST_CAPACITY = 40 };      // a conservative number for the number of
+                                    // speculative loads on all the platforms
+  static address speculative_load_pclist [];
+  static address slowcase_entry_pclist   [];
+  static int     count;
+
+  static address generate_fast_get_int_field0(BasicType type);
+  static address generate_fast_get_float_field0(BasicType type);
+
+ public:
+#if defined(_WINDOWS) && !defined(_WIN64)
+  static GetBooleanField_t jni_fast_GetBooleanField_fp;
+  static GetByteField_t    jni_fast_GetByteField_fp;
+  static GetCharField_t    jni_fast_GetCharField_fp;
+  static GetShortField_t   jni_fast_GetShortField_fp;
+  static GetIntField_t     jni_fast_GetIntField_fp;
+  static GetLongField_t    jni_fast_GetLongField_fp;
+  static GetFloatField_t   jni_fast_GetFloatField_fp;
+  static GetDoubleField_t  jni_fast_GetDoubleField_fp;
+#endif
+
+  static address generate_fast_get_boolean_field();
+  static address generate_fast_get_byte_field();
+  static address generate_fast_get_char_field();
+  static address generate_fast_get_short_field();
+  static address generate_fast_get_int_field();
+  static address generate_fast_get_long_field();
+  static address generate_fast_get_float_field();
+  static address generate_fast_get_double_field();
+
+  // If pc is in speculative_load_pclist, return the corresponding
+  // slow case entry pc. Otherwise, return -1.
+  // This is used by signal/exception handler to handle such case:
+  // After an even safepoint counter is loaded and a fast field access
+  // is about to begin, a GC kicks in and shrinks the heap. Then the
+  // field access may fault. The signal/exception handler needs to
+  // return to the slow case.
+  //
+  // The GC may decide to temporarily stuff some bad values into handles,
+  // for example, for debugging purpose, in which case we need the mapping also.
+  static address find_slowcase_pc(address pc);
+};