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src/share/vm/runtime/jfieldIDWorkaround.hpp@9f4457a14b58 (annotated)

src/share/vm/runtime/jfieldIDWorkaround.hpp

Wed, 09 Apr 2008 15:10:22 -0700

author

rasbold

date

Wed, 09 Apr 2008 15:10:22 -0700

changeset 544

9f4457a14b58

parent 435

a61af66fc99e

child 1907

c18cbe5936b8

permissions

-rw-r--r--

Merge

duke@435	1	/*
duke@435	2	* Copyright 2003-2005 Sun Microsystems, Inc. All Rights Reserved.
duke@435	3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435	4	*
duke@435	5	* This code is free software; you can redistribute it and/or modify it
duke@435	6	* under the terms of the GNU General Public License version 2 only, as
duke@435	7	* published by the Free Software Foundation.
duke@435	8	*
duke@435	9	* This code is distributed in the hope that it will be useful, but WITHOUT
duke@435	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@435	12	* version 2 for more details (a copy is included in the LICENSE file that
duke@435	13	* accompanied this code).
duke@435	14	*
duke@435	15	* You should have received a copy of the GNU General Public License version
duke@435	16	* 2 along with this work; if not, write to the Free Software Foundation,
duke@435	17	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435	18	*
duke@435	19	* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435	20	* CA 95054 USA or visit www.sun.com if you need additional information or
duke@435	21	* have any questions.
duke@435	22	*
duke@435	23	*/
duke@435	24
duke@435	25	class jfieldIDWorkaround: AllStatic {
duke@435	26	// This workaround is because JVMTI doesn't have distinct entry points
duke@435	27	// for methods that use static jfieldIDs and instance jfieldIDs.
duke@435	28	// The workaround is to steal a low-order bit:
duke@435	29	// a 1 means the jfieldID is an instance jfieldID,
duke@435	30	// and the rest of the word is the offset of the field.
duke@435	31	// a 0 means the jfieldID is a static jfieldID,
duke@435	32	// and the rest of the word is the JNIid*.
duke@435	33	//
duke@435	34	// Another low-order bit is used to mark if an instance field
duke@435	35	// is accompanied by an indication of which class it applies to.
duke@435	36	//
duke@435	37	// Bit-format of a jfieldID (most significant first):
duke@435	38	// address:30 instance=0:1 checked=0:1
duke@435	39	// offset:30 instance=1:1 checked=0:1
duke@435	40	// klass:23 offset:7 instance=1:1 checked=1:1
duke@435	41	//
duke@435	42	// If the offset does not fit in 7 bits, or if the fieldID is
duke@435	43	// not checked, then the checked bit is zero and the rest of
duke@435	44	// the word (30 bits) contains only the offset.
duke@435	45	//
duke@435	46	private:
duke@435	47	enum {
duke@435	48	checked_bits = 1,
duke@435	49	instance_bits = 1,
duke@435	50	address_bits = BitsPerWord - checked_bits - instance_bits,
duke@435	51
duke@435	52	large_offset_bits = address_bits, // unioned with address
duke@435	53	small_offset_bits = 7,
duke@435	54	klass_bits = address_bits - small_offset_bits,
duke@435	55
duke@435	56	checked_shift = 0,
duke@435	57	instance_shift = checked_shift + checked_bits,
duke@435	58	address_shift = instance_shift + instance_bits,
duke@435	59
duke@435	60	offset_shift = address_shift, // unioned with address
duke@435	61	klass_shift = offset_shift + small_offset_bits,
duke@435	62
duke@435	63	checked_mask_in_place = right_n_bits(checked_bits) << checked_shift,
duke@435	64	instance_mask_in_place = right_n_bits(instance_bits) << instance_shift,
duke@435	65	#ifndef _WIN64
duke@435	66	large_offset_mask = right_n_bits(large_offset_bits),
duke@435	67	small_offset_mask = right_n_bits(small_offset_bits),
duke@435	68	klass_mask = right_n_bits(klass_bits)
duke@435	69	#endif
duke@435	70	};
duke@435	71
duke@435	72	#ifdef _WIN64
duke@435	73	// These values are too big for Win64
duke@435	74	const static uintptr_t large_offset_mask = right_n_bits(large_offset_bits);
duke@435	75	const static uintptr_t small_offset_mask = right_n_bits(small_offset_bits);
duke@435	76	const static uintptr_t klass_mask = right_n_bits(klass_bits);
duke@435	77	#endif
duke@435	78
duke@435	79	// helper routines:
duke@435	80	static bool is_checked_jfieldID(jfieldID id) {
duke@435	81	uintptr_t as_uint = (uintptr_t) id;
duke@435	82	return ((as_uint & checked_mask_in_place) != 0);
duke@435	83	}
duke@435	84	static intptr_t raw_instance_offset(jfieldID id) {
duke@435	85	uintptr_t result = (uintptr_t) id >> address_shift;
duke@435	86	if (VerifyJNIFields && is_checked_jfieldID(id)) {
duke@435	87	result &= small_offset_mask; // cut off the hash bits
duke@435	88	}
duke@435	89	return (intptr_t)result;
duke@435	90	}
duke@435	91	static intptr_t encode_klass_hash(klassOop k, intptr_t offset);
duke@435	92	static bool klass_hash_ok(klassOop k, jfieldID id);
duke@435	93	static void verify_instance_jfieldID(klassOop k, jfieldID id);
duke@435	94
duke@435	95	public:
duke@435	96	static bool is_valid_jfieldID(klassOop k, jfieldID id);
duke@435	97
duke@435	98	static bool is_instance_jfieldID(klassOop k, jfieldID id) {
duke@435	99	uintptr_t as_uint = (uintptr_t) id;
duke@435	100	return ((as_uint & instance_mask_in_place) != 0);
duke@435	101	}
duke@435	102	static bool is_static_jfieldID(jfieldID id) {
duke@435	103	uintptr_t as_uint = (uintptr_t) id;
duke@435	104	return ((as_uint & instance_mask_in_place) == 0);
duke@435	105	}
duke@435	106
duke@435	107	static jfieldID to_instance_jfieldID(klassOop k, int offset) {
duke@435	108	intptr_t as_uint = ((offset & large_offset_mask) << offset_shift) | instance_mask_in_place;
duke@435	109	if (VerifyJNIFields) {
duke@435	110	as_uint |= encode_klass_hash(k, offset);
duke@435	111	}
duke@435	112	jfieldID result = (jfieldID) as_uint;
duke@435	113	#ifndef ASSERT
duke@435	114	// always verify in debug mode; switchable in anything else
duke@435	115	if (VerifyJNIFields)
duke@435	116	#endif // ASSERT
duke@435	117	{
duke@435	118	verify_instance_jfieldID(k, result);
duke@435	119	}
duke@435	120	assert(raw_instance_offset(result) == (offset & large_offset_mask), "extract right offset");
duke@435	121	return result;
duke@435	122	}
duke@435	123
duke@435	124	static intptr_t from_instance_jfieldID(klassOop k, jfieldID id) {
duke@435	125	#ifndef ASSERT
duke@435	126	// always verify in debug mode; switchable in anything else
duke@435	127	if (VerifyJNIFields)
duke@435	128	#endif // ASSERT
duke@435	129	{
duke@435	130	verify_instance_jfieldID(k, id);
duke@435	131	}
duke@435	132	return raw_instance_offset(id);
duke@435	133	}
duke@435	134
duke@435	135	static jfieldID to_static_jfieldID(JNIid* id) {
duke@435	136	assert(id->is_static_field_id(), "from_JNIid, but not static field id");
duke@435	137	jfieldID result = (jfieldID) id;
duke@435	138	assert(from_static_jfieldID(result) == id, "must produce the same static id");
duke@435	139	return result;
duke@435	140	}
duke@435	141
duke@435	142	static JNIid* from_static_jfieldID(jfieldID id) {
duke@435	143	assert(jfieldIDWorkaround::is_static_jfieldID(id),
duke@435	144	"to_JNIid, but not static jfieldID");
duke@435	145	JNIid* result = (JNIid*) id;
duke@435	146	assert(result->is_static_field_id(), "to_JNIid, but not static field id");
duke@435	147	return result;
duke@435	148	}
duke@435	149
duke@435	150	static jfieldID to_jfieldID(instanceKlassHandle k, int offset, bool is_static) {
duke@435	151	if (is_static) {
duke@435	152	JNIid *id = k->jni_id_for(offset);
duke@435	153	debug_only(id->set_is_static_field_id());
duke@435	154	return jfieldIDWorkaround::to_static_jfieldID(id);
duke@435	155	} else {
duke@435	156	return jfieldIDWorkaround::to_instance_jfieldID(k(), offset);
duke@435	157	}
duke@435	158	}
duke@435	159	};