1/*
2 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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).
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23 */
24
25#ifndef SHARE_UTILITIES_ALIGN_HPP
26#define SHARE_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_UTILITIES_ALIGN_HPP
153