1 /* 2 * Copyright (c) 2004, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_PRIMS_JNIFASTGETFIELD_HPP 26 #define SHARE_PRIMS_JNIFASTGETFIELD_HPP 27 28 #include "memory/allocation.hpp" 29 #include "prims/jvm_misc.hpp" 30 31 // Basic logic of a fast version of jni_Get<Primitive>Field: 32 // 33 // (See safepoint.hpp for a description of _safepoint_counter) 34 // 35 // load _safepoint_counter into old_counter 36 // IF old_counter is odd THEN 37 // a safepoint is going on, return jni_GetXXXField 38 // ELSE 39 // load the primitive field value into result (speculatively) 40 // load _safepoint_counter into new_counter 41 // IF (old_counter == new_counter) THEN 42 // no safepoint happened during the field access, return result 43 // ELSE 44 // a safepoint might have happened in-between, return jni_GetXXXField() 45 // ENDIF 46 // ENDIF 47 // 48 // LoadLoad membars to maintain the load order may be necessary 49 // for some platforms. 50 // 51 // The fast versions don't check for pending suspension request. 52 // This is fine since it's totally read-only and doesn't create new race. 53 // 54 // There is a hypothetical safepoint counter wraparound. But it's not 55 // a practical concern. 56 57 class JNI_FastGetField : AllStatic { 58 private: 59 enum { LIST_CAPACITY = 40 }; // a conservative number for the number of 60 // speculative loads on all the platforms 61 static address speculative_load_pclist []; 62 static address slowcase_entry_pclist []; 63 static int count; 64 65 static address generate_fast_get_int_field0(BasicType type); 66 static address generate_fast_get_float_field0(BasicType type); 67 68 public: 69 #if defined(_WINDOWS) && !defined(_WIN64) 70 static GetBooleanField_t jni_fast_GetBooleanField_fp; 71 static GetByteField_t jni_fast_GetByteField_fp; 72 static GetCharField_t jni_fast_GetCharField_fp; 73 static GetShortField_t jni_fast_GetShortField_fp; 74 static GetIntField_t jni_fast_GetIntField_fp; 75 static GetLongField_t jni_fast_GetLongField_fp; 76 static GetFloatField_t jni_fast_GetFloatField_fp; 77 static GetDoubleField_t jni_fast_GetDoubleField_fp; 78 #endif 79 80 static address generate_fast_get_boolean_field(); 81 static address generate_fast_get_byte_field(); 82 static address generate_fast_get_char_field(); 83 static address generate_fast_get_short_field(); 84 static address generate_fast_get_int_field(); 85 static address generate_fast_get_long_field(); 86 static address generate_fast_get_float_field(); 87 static address generate_fast_get_double_field(); 88 89 // If pc is in speculative_load_pclist, return the corresponding 90 // slow case entry pc. Otherwise, return -1. 91 // This is used by signal/exception handler to handle such case: 92 // After an even safepoint counter is loaded and a fast field access 93 // is about to begin, a GC kicks in and shrinks the heap. Then the 94 // field access may fault. The signal/exception handler needs to 95 // return to the slow case. 96 // 97 // The GC may decide to temporarily stuff some bad values into handles, 98 // for example, for debugging purpose, in which case we need the mapping also. 99 static address find_slowcase_pc(address pc); 100 }; 101 102 #endif // SHARE_PRIMS_JNIFASTGETFIELD_HPP 103