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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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).
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15 * You should have received a copy of the GNU General Public License version
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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.
50 template <typename T>
51 bool 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
57 template <typename T, typename A>
58 inline T align_up(T size, A alignment) {
59 assert(is_power_of_2_t(alignment), "must be a power of 2: " UINT64_FORMAT);
60
61 T ret = align_up_(size, alignment);
62 assert(is_aligned_(ret, alignment), "must be aligned: " UINT64_FORMAT);
63
64 return ret;
65 }
66
67 template <typename T, typename A>
68 inline T align_down(T size, A alignment) {
69 assert(is_power_of_2_t(alignment), "must be a power of 2: " UINT64_FORMAT);
70
71 T ret = align_down_(size, alignment);
72 assert(is_aligned_(ret, alignment), "must be aligned: " UINT64_FORMAT);
73
74 return ret;
75 }
76
77 template <typename T, typename A>
78 inline bool is_aligned(T size, A alignment) {
79 assert(is_power_of_2_t(alignment), "must be a power of 2: " UINT64_FORMAT);
80
81 return is_aligned_(size, alignment);
82 }
83
84 // Align down with a lower bound. If the aligning results in 0, return 'alignment'.
85 template <typename T, typename A>
86 inline 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
93 template <typename T, typename A>
94 inline T* align_up(T* ptr, A alignment) {
95 return (T*)align_up((uintptr_t)ptr, alignment);
96 }
97
98 template <typename T, typename A>
99 inline T* align_down(T* ptr, A alignment) {
100 return (T*)align_down((uintptr_t)ptr, alignment);
101 }
102
103 template <typename T, typename A>
104 inline 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
109 template <typename T>
110 inline 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.
115 template <typename T>
116 inline T align_object_size(T word_size) {
117 return align_up(word_size, MinObjAlignment);
118 }
119
120 inline bool is_object_aligned(size_t word_size) {
121 return is_aligned(word_size, MinObjAlignment);
122 }
123
124 inline 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.
129 template <typename T>
130 inline 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
138 template <typename T>
139 inline 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