1/* 2 * Copyright (c) 1997, 2017, 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_VM_UTILITIES_ALIGN_HPP 26#define SHARE_VM_UTILITIES_ALIGN_HPP 27 28#include "utilities/globalDefinitions.hpp" 29 30// Signed variants of alignment helpers. There are two versions of each, a macro 31// for use in places like enum definitions that require compile-time constant 32// expressions and a function for all other places so as to get type checking. 33 34// Using '(what) & ~align_mask(alignment)' to align 'what' down is broken when 35// 'alignment' is an unsigned int and 'what' is a wider type. The & operation 36// will widen the inverted mask, and not sign extend it, leading to a mask with 37// zeros in the most significant bits. The use of align_mask_widened() solves 38// this problem. 39#define align_mask(alignment) ((alignment) - 1) 40#define widen_to_type_of(what, type_carrier) (true ? (what) : (type_carrier)) 41#define align_mask_widened(alignment, type_carrier) widen_to_type_of(align_mask(alignment), (type_carrier)) 42 43#define align_down_(size, alignment) ((size) & ~align_mask_widened((alignment), (size))) 44 45#define align_up_(size, alignment) (align_down_((size) + align_mask(alignment), (alignment))) 46 47#define is_aligned_(size, alignment) (((size) & align_mask(alignment)) == 0) 48 49// Temporary declaration until this file has been restructured. 50template <typename T> 51bool is_power_of_2_t(T x) { 52 return (x != T(0)) && ((x & (x - 1)) == T(0)); 53} 54 55// Helpers to align sizes and check for alignment 56 57template <typename T, typename A> 58inline T align_up(T size, A alignment) { 59 assert(is_power_of_2_t(alignment), "must be a power of 2: " UINT64_FORMAT, (uint64_t)alignment); 60 61 T ret = align_up_(size, alignment); 62 assert(is_aligned_(ret, alignment), "must be aligned: " UINT64_FORMAT, (uint64_t)ret); 63 64 return ret; 65} 66 67template <typename T, typename A> 68inline T align_down(T size, A alignment) { 69 assert(is_power_of_2_t(alignment), "must be a power of 2: " UINT64_FORMAT, (uint64_t)alignment); 70 71 T ret = align_down_(size, alignment); 72 assert(is_aligned_(ret, alignment), "must be aligned: " UINT64_FORMAT, (uint64_t)ret); 73 74 return ret; 75} 76 77template <typename T, typename A> 78inline bool is_aligned(T size, A alignment) { 79 assert(is_power_of_2_t(alignment), "must be a power of 2: " UINT64_FORMAT, (uint64_t)alignment); 80 81 return is_aligned_(size, alignment); 82} 83 84// Align down with a lower bound. If the aligning results in 0, return 'alignment'. 85template <typename T, typename A> 86inline T align_down_bounded(T size, A alignment) { 87 A aligned_size = align_down(size, alignment); 88 return aligned_size > 0 ? aligned_size : alignment; 89} 90 91// Helpers to align pointers and check for alignment. 92 93template <typename T, typename A> 94inline T* align_up(T* ptr, A alignment) { 95 return (T*)align_up((uintptr_t)ptr, alignment); 96} 97 98template <typename T, typename A> 99inline T* align_down(T* ptr, A alignment) { 100 return (T*)align_down((uintptr_t)ptr, alignment); 101} 102 103template <typename T, typename A> 104inline bool is_aligned(T* ptr, A alignment) { 105 return is_aligned((uintptr_t)ptr, alignment); 106} 107 108// Align metaspace objects by rounding up to natural word boundary 109template <typename T> 110inline T align_metadata_size(T size) { 111 return align_up(size, 1); 112} 113 114// Align objects in the Java Heap by rounding up their size, in HeapWord units. 115template <typename T> 116inline T align_object_size(T word_size) { 117 return align_up(word_size, MinObjAlignment); 118} 119 120inline bool is_object_aligned(size_t word_size) { 121 return is_aligned(word_size, MinObjAlignment); 122} 123 124inline bool is_object_aligned(const void* addr) { 125 return is_aligned(addr, MinObjAlignmentInBytes); 126} 127 128// Pad out certain offsets to jlong alignment, in HeapWord units. 129template <typename T> 130inline T align_object_offset(T offset) { 131 return align_up(offset, HeapWordsPerLong); 132} 133 134// Clamp an address to be within a specific page 135// 1. If addr is on the page it is returned as is 136// 2. If addr is above the page_address the start of the *next* page will be returned 137// 3. Otherwise, if addr is below the page_address the start of the page will be returned 138template <typename T> 139inline T* clamp_address_in_page(T* addr, T* page_address, size_t page_size) { 140 if (align_down(addr, page_size) == align_down(page_address, page_size)) { 141 // address is in the specified page, just return it as is 142 return addr; 143 } else if (addr > page_address) { 144 // address is above specified page, return start of next page 145 return align_down(page_address, page_size) + page_size; 146 } else { 147 // address is below specified page, return start of page 148 return align_down(page_address, page_size); 149 } 150} 151 152#endif // SHARE_VM_UTILITIES_ALIGN_HPP 153