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