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1 /*
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2 * Copyright 2004 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // Basic logic of a fast version of jni_Get<Primitive>Field:
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26 //
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27 // (See safepoint.hpp for a description of _safepoint_counter)
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28 //
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29 // load _safepoint_counter into old_counter
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30 // IF old_counter is odd THEN
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31 // a safepoint is going on, return jni_GetXXXField
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32 // ELSE
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33 // load the primitive field value into result (speculatively)
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34 // load _safepoint_counter into new_counter
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35 // IF (old_counter == new_counter) THEN
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36 // no safepoint happened during the field access, return result
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37 // ELSE
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38 // a safepoint might have happened in-between, return jni_GetXXXField()
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39 // ENDIF
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40 // ENDIF
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41 //
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42 // LoadLoad membars to maintain the load order may be necessary
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43 // for some platforms.
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44 //
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45 // The fast versions don't check for pending suspension request.
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46 // This is fine since it's totally read-only and doesn't create new race.
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47 //
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48 // There is a hypothetical safepoint counter wraparound. But it's not
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49 // a practical concern.
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50
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51 class JNI_FastGetField : AllStatic {
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52 private:
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53 enum { LIST_CAPACITY = 40 }; // a conservative number for the number of
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54 // speculative loads on all the platforms
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55 static address speculative_load_pclist [];
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56 static address slowcase_entry_pclist [];
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57 static int count;
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58
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59 static address generate_fast_get_int_field0(BasicType type);
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60 static address generate_fast_get_float_field0(BasicType type);
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61
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62 public:
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63 #if defined(_WINDOWS) && !defined(_WIN64)
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64 static GetBooleanField_t jni_fast_GetBooleanField_fp;
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65 static GetByteField_t jni_fast_GetByteField_fp;
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66 static GetCharField_t jni_fast_GetCharField_fp;
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67 static GetShortField_t jni_fast_GetShortField_fp;
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68 static GetIntField_t jni_fast_GetIntField_fp;
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69 static GetLongField_t jni_fast_GetLongField_fp;
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70 static GetFloatField_t jni_fast_GetFloatField_fp;
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71 static GetDoubleField_t jni_fast_GetDoubleField_fp;
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72 #endif
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73
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74 static address generate_fast_get_boolean_field();
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75 static address generate_fast_get_byte_field();
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76 static address generate_fast_get_char_field();
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77 static address generate_fast_get_short_field();
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78 static address generate_fast_get_int_field();
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79 static address generate_fast_get_long_field();
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80 static address generate_fast_get_float_field();
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81 static address generate_fast_get_double_field();
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82
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83 // If pc is in speculative_load_pclist, return the corresponding
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84 // slow case entry pc. Otherwise, return -1.
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85 // This is used by signal/exception handler to handle such case:
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86 // After an even safepoint counter is loaded and a fast field access
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87 // is about to begin, a GC kicks in and shrinks the heap. Then the
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88 // field access may fault. The signal/exception handler needs to
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89 // return to the slow case.
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90 //
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91 // The GC may decide to temporarily stuff some bad values into handles,
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92 // for example, for debugging purpose, in which case we need the mapping also.
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93 static address find_slowcase_pc(address pc);
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94 };
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