1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1988-2023 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Funding Free Software", the Front-Cover
Texts being (a) (see below), and with the Back-Cover Texts being (b)
(see below). A copy of the license is included in the section entitled
"GNU Free Documentation License".
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development. -->
<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ -->
<head>
<title>GNU Compiler Collection (GCC) Internals: Comparing ordered poly_ints</title>
<meta name="description" content="GNU Compiler Collection (GCC) Internals: Comparing ordered poly_ints">
<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Comparing ordered poly_ints">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link href="index.html#Top" rel="start" title="Top">
<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Comparisons-involving-poly_005fint.html#Comparisons-involving-poly_005fint" rel="up" title="Comparisons involving poly_int">
<link href="Checking-for-a-poly_005fint-marker-value.html#Checking-for-a-poly_005fint-marker-value" rel="next" title="Checking for a poly_int marker value">
<link href="Comparing-potentially_002dunordered-poly_005fints.html#Comparing-potentially_002dunordered-poly_005fints" rel="previous" title="Comparing potentially-unordered poly_ints">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.indentedblock {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
div.smalllisp {margin-left: 3.2em}
kbd {font-style:oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nocodebreak {white-space:nowrap}
span.nolinebreak {white-space:nowrap}
span.roman {font-family:serif; font-weight:normal}
span.sansserif {font-family:sans-serif; font-weight:normal}
ul.no-bullet {list-style: none}
-->
</style>
</head>
<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
<a name="Comparing-ordered-poly_005fints"></a>
<div class="header">
<p>
Next: <a href="Checking-for-a-poly_005fint-marker-value.html#Checking-for-a-poly_005fint-marker-value" accesskey="n" rel="next">Checking for a <code>poly_int</code> marker value</a>, Previous: <a href="Comparing-potentially_002dunordered-poly_005fints.html#Comparing-potentially_002dunordered-poly_005fints" accesskey="p" rel="previous">Comparing potentially-unordered <code>poly_int</code>s</a>, Up: <a href="Comparisons-involving-poly_005fint.html#Comparisons-involving-poly_005fint" accesskey="u" rel="up">Comparisons involving <code>poly_int</code></a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Comparing-ordered-poly_005fints-1"></a>
<h4 class="subsection">10.3.4 Comparing ordered <code>poly_int</code>s</h4>
<p>In cases where there is a definite link between two <code>poly_int</code>s,
such as the outer and inner sizes of subregs, we usually require the sizes
to be ordered by the <code>known_le</code> partial order. <code>poly_int</code> provides
the following utility functions for ordered values:
</p>
<dl compact="compact">
<dt>‘<samp>ordered_p (<var>a</var>, <var>b</var>)</samp>’</dt>
<dd><p>Return true if <var>a</var> and <var>b</var> are ordered by the <code>known_le</code>
partial order.
</p>
</dd>
<dt>‘<samp>ordered_min (<var>a</var>, <var>b</var>)</samp>’</dt>
<dd><p>Assert that <var>a</var> and <var>b</var> are ordered by <code>known_le</code> and return the
minimum of the two. When using this function, please add a comment explaining
why the values are known to be ordered.
</p>
</dd>
<dt>‘<samp>ordered_max (<var>a</var>, <var>b</var>)</samp>’</dt>
<dd><p>Assert that <var>a</var> and <var>b</var> are ordered by <code>known_le</code> and return the
maximum of the two. When using this function, please add a comment explaining
why the values are known to be ordered.
</p></dd>
</dl>
<p>For example, if a subreg has an outer mode of size <var>outer</var> and an
inner mode of size <var>inner</var>:
</p>
<ul>
<li> the subreg is complete if known_eq (<var>inner</var>, <var>outer</var>)
</li><li> otherwise, the subreg is paradoxical if known_le (<var>inner</var>, <var>outer</var>)
</li><li> otherwise, the subreg is partial if known_le (<var>outer</var>, <var>inner</var>)
</li><li> otherwise, the subreg is ill-formed
</li></ul>
<p>Thus the subreg is only valid if
‘<samp>ordered_p (<var>outer</var>, <var>inner</var>)</samp>’ is true. If this condition
is already known to be true then:
</p>
<ul>
<li> the subreg is complete if known_eq (<var>inner</var>, <var>outer</var>)
</li><li> the subreg is paradoxical if maybe_lt (<var>inner</var>, <var>outer</var>)
</li><li> the subreg is partial if maybe_lt (<var>outer</var>, <var>inner</var>)
</li></ul>
<p>with the three conditions being mutually exclusive.
</p>
<p>Code that checks whether a subreg is valid would therefore generally
check whether <code>ordered_p</code> holds (in addition to whatever other
checks are required for subreg validity). Code that is dealing
with existing subregs can assert that <code>ordered_p</code> holds
and use either of the classifications above.
</p>
<hr>
<div class="header">
<p>
Next: <a href="Checking-for-a-poly_005fint-marker-value.html#Checking-for-a-poly_005fint-marker-value" accesskey="n" rel="next">Checking for a <code>poly_int</code> marker value</a>, Previous: <a href="Comparing-potentially_002dunordered-poly_005fints.html#Comparing-potentially_002dunordered-poly_005fints" accesskey="p" rel="previous">Comparing potentially-unordered <code>poly_int</code>s</a>, Up: <a href="Comparisons-involving-poly_005fint.html#Comparisons-involving-poly_005fint" accesskey="u" rel="up">Comparisons involving <code>poly_int</code></a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
</div>
</body>
</html>
|
