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1 | @c Copyright 1996, 1997, 1998, 1999, 2000, 2001 |
2 | @c Free Software Foundation, Inc. | |
252b5132 RH |
3 | @c This is part of the GAS manual. |
4 | @c For copying conditions, see the file as.texinfo. | |
5 | ||
6 | @ifset GENERIC | |
7 | @page | |
8 | @node ARM-Dependent | |
9 | @chapter ARM Dependent Features | |
10 | @end ifset | |
11 | ||
12 | @ifclear GENERIC | |
13 | @node Machine Dependencies | |
14 | @chapter ARM Dependent Features | |
15 | @end ifclear | |
16 | ||
17 | @cindex ARM support | |
18 | @cindex Thumb support | |
19 | @menu | |
20 | * ARM Options:: Options | |
21 | * ARM Syntax:: Syntax | |
22 | * ARM Floating Point:: Floating Point | |
23 | * ARM Directives:: ARM Machine Directives | |
24 | * ARM Opcodes:: Opcodes | |
25 | @end menu | |
26 | ||
27 | @node ARM Options | |
28 | @section Options | |
29 | @cindex ARM options (none) | |
30 | @cindex options for ARM (none) | |
adcf07e6 | 31 | |
252b5132 | 32 | @table @code |
adcf07e6 | 33 | |
252b5132 | 34 | @cindex @code{-marm} command line option, ARM |
adcf07e6 | 35 | @item -marm@code{[2|250|3|6|60|600|610|620|7|7m|7d|7dm|7di|7dmi|70|700|700i|710|710c|7100|7500|7500fe|7tdmi|8|810|9|9tdmi|920|strongarm|strongarm110|strongarm1100]} |
077b8428 | 36 | @itemx -mxscale |
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37 | This option specifies the target processor. The assembler will issue an |
38 | error message if an attempt is made to assemble an instruction which | |
39 | will not execute on the target processor. | |
adcf07e6 | 40 | |
252b5132 | 41 | @cindex @code{-marmv} command line option, ARM |
077b8428 | 42 | @item -marmv@code{[2|2a|3|3m|4|4t|5|5t|5te]} |
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43 | This option specifies the target architecture. The assembler will issue |
44 | an error message if an attempt is made to assemble an instruction which | |
45 | will not execute on the target architecture. | |
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46 | The option @code{-marmv5te} specifies that v5t architecture should be |
47 | used with the El Segundo extensions enabled. | |
adcf07e6 | 48 | |
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49 | @cindex @code{-mthumb} command line option, ARM |
50 | @item -mthumb | |
51 | This option specifies that only Thumb instructions should be assembled. | |
adcf07e6 | 52 | |
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53 | @cindex @code{-mall} command line option, ARM |
54 | @item -mall | |
55 | This option specifies that any Arm or Thumb instruction should be assembled. | |
adcf07e6 | 56 | |
252b5132 | 57 | @cindex @code{-mfpa} command line option, ARM |
0ac658b8 | 58 | @item -mfpa @code{[10|11]} |
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59 | This option specifies the floating point architecture in use on the |
60 | target processor. | |
adcf07e6 | 61 | |
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62 | @cindex @code{-mfpe-old} command line option, ARM |
63 | @item -mfpe-old | |
a349d9dd | 64 | Do not allow the assembly of floating point multiple instructions. |
adcf07e6 | 65 | |
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66 | @cindex @code{-mno-fpu} command line option, ARM |
67 | @item -mno-fpu | |
68 | Do not allow the assembly of any floating point instructions. | |
adcf07e6 | 69 | |
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70 | @cindex @code{-mthumb-interwork} command line option, ARM |
71 | @item -mthumb-interwork | |
72 | This option specifies that the output generated by the assembler should | |
73 | be marked as supporting interworking. | |
adcf07e6 | 74 | |
252b5132 | 75 | @cindex @code{-mapcs} command line option, ARM |
0ac658b8 | 76 | @item -mapcs @code{[26|32]} |
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77 | This option specifies that the output generated by the assembler should |
78 | be marked as supporting the indicated version of the Arm Procedure. | |
79 | Calling Standard. | |
adcf07e6 | 80 | |
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81 | @cindex @code{-matpcs} command line option, ARM |
82 | @item -matpcs | |
83 | This option specifies that the output generated by the assembler should | |
84 | be marked as supporting the Arm/Thumb Procedure Calling Standard. If | |
85 | enabled this option will cause the assembler to create an empty | |
86 | debugging section in the object file called .arm.atpcs. Debuggers can | |
87 | use this to determine the ABI being used by. | |
88 | ||
adcf07e6 | 89 | @cindex @code{-mapcs-float} command line option, ARM |
252b5132 RH |
90 | @item -mapcs-float |
91 | This indicates the the floating point variant of the APCS should be | |
92 | used. In this variant floating point arguments are passed in FP | |
550262c4 | 93 | registers rather than integer registers. |
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94 | |
95 | @cindex @code{-mapcs-reentrant} command line option, ARM | |
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96 | @item -mapcs-reentrant |
97 | This indicates that the reentrant variant of the APCS should be used. | |
98 | This variant supports position independent code. | |
adcf07e6 | 99 | |
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100 | @cindex @code{-EB} command line option, ARM |
101 | @item -EB | |
102 | This option specifies that the output generated by the assembler should | |
103 | be marked as being encoded for a big-endian processor. | |
adcf07e6 | 104 | |
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105 | @cindex @code{-EL} command line option, ARM |
106 | @item -EL | |
107 | This option specifies that the output generated by the assembler should | |
108 | be marked as being encoded for a little-endian processor. | |
adcf07e6 | 109 | |
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110 | @cindex @code{-k} command line option, ARM |
111 | @cindex PIC code generation for ARM | |
112 | @item -k | |
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113 | This option specifies that the output of the assembler should be marked |
114 | as position-independent code (PIC). | |
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115 | |
116 | @cindex @code{-moabi} command line option, ARM | |
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117 | @item -moabi |
118 | This indicates that the code should be assembled using the old ARM ELF | |
119 | conventions, based on a beta release release of the ARM-ELF | |
120 | specifications, rather than the default conventions which are based on | |
121 | the final release of the ARM-ELF specifications. | |
adcf07e6 | 122 | |
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123 | @end table |
124 | ||
125 | ||
126 | @node ARM Syntax | |
127 | @section Syntax | |
128 | @menu | |
129 | * ARM-Chars:: Special Characters | |
130 | * ARM-Regs:: Register Names | |
131 | @end menu | |
132 | ||
133 | @node ARM-Chars | |
134 | @subsection Special Characters | |
135 | ||
136 | @cindex line comment character, ARM | |
137 | @cindex ARM line comment character | |
550262c4 NC |
138 | The presence of a @samp{@@} on a line indicates the start of a comment |
139 | that extends to the end of the current line. If a @samp{#} appears as | |
140 | the first character of a line, the whole line is treated as a comment. | |
141 | ||
142 | @cindex line separator, ARM | |
143 | @cindex statement separator, ARM | |
144 | @cindex ARM line separator | |
a349d9dd PB |
145 | The @samp{;} character can be used instead of a newline to separate |
146 | statements. | |
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147 | |
148 | @cindex immediate character, ARM | |
149 | @cindex ARM immediate character | |
150 | Either @samp{#} or @samp{$} can be used to indicate immediate operands. | |
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151 | |
152 | @cindex identifiers, ARM | |
153 | @cindex ARM identifiers | |
154 | *TODO* Explain about /data modifier on symbols. | |
155 | ||
156 | @node ARM-Regs | |
157 | @subsection Register Names | |
158 | ||
159 | @cindex ARM register names | |
160 | @cindex register names, ARM | |
161 | *TODO* Explain about ARM register naming, and the predefined names. | |
162 | ||
163 | @node ARM Floating Point | |
164 | @section Floating Point | |
165 | ||
166 | @cindex floating point, ARM (@sc{ieee}) | |
167 | @cindex ARM floating point (@sc{ieee}) | |
168 | The ARM family uses @sc{ieee} floating-point numbers. | |
169 | ||
170 | ||
171 | ||
172 | @node ARM Directives | |
173 | @section ARM Machine Directives | |
174 | ||
175 | @cindex machine directives, ARM | |
176 | @cindex ARM machine directives | |
177 | @table @code | |
178 | ||
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179 | @cindex @code{align} directive, ARM |
180 | @item .align @var{expression} [, @var{expression}] | |
181 | This is the generic @var{.align} directive. For the ARM however if the | |
182 | first argument is zero (ie no alignment is needed) the assembler will | |
183 | behave as if the argument had been 2 (ie pad to the next four byte | |
184 | boundary). This is for compatability with ARM's own assembler. | |
185 | ||
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186 | @cindex @code{req} directive, ARM |
187 | @item @var{name} .req @var{register name} | |
188 | This creates an alias for @var{register name} called @var{name}. For | |
189 | example: | |
190 | ||
191 | @smallexample | |
192 | foo .req r0 | |
193 | @end smallexample | |
194 | ||
195 | @cindex @code{code} directive, ARM | |
0ac658b8 | 196 | @item .code @code{[16|32]} |
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197 | This directive selects the instruction set being generated. The value 16 |
198 | selects Thumb, with the value 32 selecting ARM. | |
199 | ||
200 | @cindex @code{thumb} directive, ARM | |
201 | @item .thumb | |
202 | This performs the same action as @var{.code 16}. | |
203 | ||
204 | @cindex @code{arm} directive, ARM | |
205 | @item .arm | |
206 | This performs the same action as @var{.code 32}. | |
207 | ||
208 | @cindex @code{force_thumb} directive, ARM | |
209 | @item .force_thumb | |
210 | This directive forces the selection of Thumb instructions, even if the | |
211 | target processor does not support those instructions | |
212 | ||
213 | @cindex @code{thumb_func} directive, ARM | |
214 | @item .thumb_func | |
215 | This directive specifies that the following symbol is the name of a | |
216 | Thumb encoded function. This information is necessary in order to allow | |
217 | the assembler and linker to generate correct code for interworking | |
218 | between Arm and Thumb instructions and should be used even if | |
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219 | interworking is not going to be performed. The presence of this |
220 | directive also implies @code{.thumb} | |
252b5132 | 221 | |
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222 | @cindex @code{thumb_set} directive, ARM |
223 | @item .thumb_set | |
224 | This performs the equivalent of a @code{.set} directive in that it | |
225 | creates a symbol which is an alias for another symbol (possibly not yet | |
226 | defined). This directive also has the added property in that it marks | |
227 | the aliased symbol as being a thumb function entry point, in the same | |
228 | way that the @code{.thumb_func} directive does. | |
229 | ||
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230 | @cindex @code{.ltorg} directive, ARM |
231 | @item .ltorg | |
232 | This directive causes the current contents of the literal pool to be | |
233 | dumped into the current section (which is assumed to be the .text | |
234 | section) at the current location (aligned to a word boundary). | |
235 | ||
236 | @cindex @code{.pool} directive, ARM | |
237 | @item .pool | |
238 | This is a synonym for .ltorg. | |
239 | ||
240 | @end table | |
241 | ||
242 | @node ARM Opcodes | |
243 | @section Opcodes | |
244 | ||
245 | @cindex ARM opcodes | |
246 | @cindex opcodes for ARM | |
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247 | @code{@value{AS}} implements all the standard ARM opcodes. It also |
248 | implements several pseudo opcodes, including several synthetic load | |
249 | instructions. | |
252b5132 | 250 | |
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251 | @table @code |
252 | ||
253 | @cindex @code{NOP} pseudo op, ARM | |
254 | @item NOP | |
255 | @smallexample | |
256 | nop | |
257 | @end smallexample | |
252b5132 | 258 | |
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259 | This pseudo op will always evaluate to a legal ARM instruction that does |
260 | nothing. Currently it will evaluate to MOV r0, r0. | |
252b5132 | 261 | |
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262 | @cindex @code{LDR reg,=<label>} pseudo op, ARM |
263 | @item LDR | |
252b5132 RH |
264 | @smallexample |
265 | ldr <register> , = <expression> | |
266 | @end smallexample | |
267 | ||
268 | If expression evaluates to a numeric constant then a MOV or MVN | |
269 | instruction will be used in place of the LDR instruction, if the | |
270 | constant can be generated by either of these instructions. Otherwise | |
271 | the constant will be placed into the nearest literal pool (if it not | |
272 | already there) and a PC relative LDR instruction will be generated. | |
273 | ||
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274 | @cindex @code{ADR reg,<label>} pseudo op, ARM |
275 | @item ADR | |
276 | @smallexample | |
277 | adr <register> <label> | |
278 | @end smallexample | |
279 | ||
280 | This instruction will load the address of @var{label} into the indicated | |
281 | register. The instruction will evaluate to a PC relative ADD or SUB | |
282 | instruction depending upon where the label is located. If the label is | |
283 | out of range, or if it is not defined in the same file (and section) as | |
284 | the ADR instruction, then an error will be generated. This instruction | |
285 | will not make use of the literal pool. | |
286 | ||
287 | @cindex @code{ADRL reg,<label>} pseudo op, ARM | |
288 | @item ADRL | |
289 | @smallexample | |
290 | adrl <register> <label> | |
291 | @end smallexample | |
292 | ||
293 | This instruction will load the address of @var{label} into the indicated | |
a349d9dd | 294 | register. The instruction will evaluate to one or two PC relative ADD |
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295 | or SUB instructions depending upon where the label is located. If a |
296 | second instruction is not needed a NOP instruction will be generated in | |
297 | its place, so that this instruction is always 8 bytes long. | |
298 | ||
299 | If the label is out of range, or if it is not defined in the same file | |
300 | (and section) as the ADRL instruction, then an error will be generated. | |
301 | This instruction will not make use of the literal pool. | |
302 | ||
303 | @end table | |
304 | ||
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305 | For information on the ARM or Thumb instruction sets, see @cite{ARM |
306 | Software Development Toolkit Reference Manual}, Advanced RISC Machines | |
307 | Ltd. | |
308 |