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
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
|
===============
LLVM Extensions
===============
.. contents::
:local:
.. toctree::
:hidden:
Introduction
============
This document describes extensions to tools and formats LLVM seeks compatibility
with.
General Assembly Syntax
===========================
C99-style Hexadecimal Floating-point Constants
----------------------------------------------
LLVM's assemblers allow floating-point constants to be written in C99's
hexadecimal format instead of decimal if desired.
.. code-block:: gas
.section .data
.float 0x1c2.2ap3
Machine-specific Assembly Syntax
================================
X86/COFF-Dependent
------------------
Relocations
^^^^^^^^^^^
The following additional relocation types are supported:
**@IMGREL** (AT&T syntax only) generates an image-relative relocation that
corresponds to the COFF relocation types ``IMAGE_REL_I386_DIR32NB`` (32-bit) or
``IMAGE_REL_AMD64_ADDR32NB`` (64-bit).
.. code-block:: gas
.text
fun:
mov foo@IMGREL(%ebx, %ecx, 4), %eax
.section .pdata
.long fun@IMGREL
.long (fun@imgrel + 0x3F)
.long $unwind$fun@imgrel
**.secrel32** generates a relocation that corresponds to the COFF relocation
types ``IMAGE_REL_I386_SECREL`` (32-bit) or ``IMAGE_REL_AMD64_SECREL`` (64-bit).
**.secidx** relocation generates an index of the section that contains
the target. It corresponds to the COFF relocation types
``IMAGE_REL_I386_SECTION`` (32-bit) or ``IMAGE_REL_AMD64_SECTION`` (64-bit).
.. code-block:: gas
.section .debug$S,"rn"
.long 4
.long 242
.long 40
.secrel32 _function_name
.secidx _function_name
...
``.linkonce`` Directive
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Syntax:
``.linkonce [ comdat type [ section identifier ] ]``
Supported COMDAT types:
``discard``
Discards duplicate sections with the same COMDAT symbol. This is the default
if no type is specified.
``one_only``
If the symbol is defined multiple times, the linker issues an error.
``same_size``
Duplicates are discarded, but the linker issues an error if any have
different sizes.
``same_contents``
Duplicates are discarded, but the linker issues an error if any duplicates
do not have exactly the same content.
``associative``
Links the section if a certain other COMDAT section is linked. This other
section is indicated by its section identifier following the comdat type.
The following restrictions apply to the associated section:
1. It must be the name of a section already defined.
2. It must differ from the current section.
3. It must be a COMDAT section.
4. It cannot be another associative COMDAT section.
``largest``
Links the largest section from among the duplicates.
``newest``
Links the newest section from among the duplicates.
.. code-block:: gas
.section .text$foo
.linkonce
...
.section .xdata$foo
.linkonce associative .text$foo
...
``.section`` Directive
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
MC supports passing the information in ``.linkonce`` at the end of
``.section``. For example, these two codes are equivalent
.. code-block:: gas
.section secName, "dr", discard, "Symbol1"
.globl Symbol1
Symbol1:
.long 1
.. code-block:: gas
.section secName, "dr"
.linkonce discard
.globl Symbol1
Symbol1:
.long 1
Note that in the combined form the COMDAT symbol is explicit. This
extension exists to support multiple sections with the same name in
different COMDATs:
.. code-block:: gas
.section secName, "dr", discard, "Symbol1"
.globl Symbol1
Symbol1:
.long 1
.section secName, "dr", discard, "Symbol2"
.globl Symbol2
Symbol2:
.long 1
|
