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82704155 | 1 | @c Copyright (C) 2009-2019 Free Software Foundation, Inc. |
a06ea964 NC |
2 | @c Contributed by ARM Ltd. |
3 | @c This is part of the GAS manual. | |
4 | @c For copying conditions, see the file as.texinfo. | |
5 | @c man end | |
6 | ||
7 | @ifset GENERIC | |
8 | @page | |
9 | @node AArch64-Dependent | |
10 | @chapter AArch64 Dependent Features | |
11 | @end ifset | |
12 | ||
13 | @ifclear GENERIC | |
14 | @node Machine Dependencies | |
15 | @chapter AArch64 Dependent Features | |
16 | @end ifclear | |
17 | ||
18 | @cindex AArch64 support | |
a06ea964 NC |
19 | @menu |
20 | * AArch64 Options:: Options | |
df359aa7 | 21 | * AArch64 Extensions:: Extensions |
a06ea964 NC |
22 | * AArch64 Syntax:: Syntax |
23 | * AArch64 Floating Point:: Floating Point | |
24 | * AArch64 Directives:: AArch64 Machine Directives | |
25 | * AArch64 Opcodes:: Opcodes | |
26 | * AArch64 Mapping Symbols:: Mapping Symbols | |
27 | @end menu | |
28 | ||
29 | @node AArch64 Options | |
30 | @section Options | |
31 | @cindex AArch64 options (none) | |
32 | @cindex options for AArch64 (none) | |
33 | ||
34 | @c man begin OPTIONS | |
35 | @table @gcctabopt | |
36 | ||
a05a5b64 | 37 | @cindex @option{-EB} command-line option, AArch64 |
a06ea964 NC |
38 | @item -EB |
39 | This option specifies that the output generated by the assembler should | |
40 | be marked as being encoded for a big-endian processor. | |
41 | ||
a05a5b64 | 42 | @cindex @option{-EL} command-line option, AArch64 |
a06ea964 NC |
43 | @item -EL |
44 | This option specifies that the output generated by the assembler should | |
45 | be marked as being encoded for a little-endian processor. | |
46 | ||
a05a5b64 | 47 | @cindex @option{-mabi=} command-line option, AArch64 |
69091a2c YZ |
48 | @item -mabi=@var{abi} |
49 | Specify which ABI the source code uses. The recognized arguments | |
50 | are: @code{ilp32} and @code{lp64}, which decides the generated object | |
51 | file in ELF32 and ELF64 format respectively. The default is @code{lp64}. | |
52 | ||
a05a5b64 | 53 | @cindex @option{-mcpu=} command-line option, AArch64 |
df359aa7 RE |
54 | @item -mcpu=@var{processor}[+@var{extension}@dots{}] |
55 | This option specifies the target processor. The assembler will issue an error | |
56 | message if an attempt is made to assemble an instruction which will not execute | |
57 | on the target processor. The following processor names are recognized: | |
546053ac | 58 | @code{cortex-a34}, |
9c352f1c | 59 | @code{cortex-a35}, |
df359aa7 | 60 | @code{cortex-a53}, |
1e292627 | 61 | @code{cortex-a55}, |
df359aa7 | 62 | @code{cortex-a57}, |
546053ac DZ |
63 | @code{cortex-a65}, |
64 | @code{cortex-a65ae}, | |
2abdd192 | 65 | @code{cortex-a72}, |
1aa70332 | 66 | @code{cortex-a73}, |
1e292627 | 67 | @code{cortex-a75}, |
c2a0f929 | 68 | @code{cortex-a76}, |
546053ac DZ |
69 | @code{cortex-a76ae}, |
70 | @code{cortex-a77}, | |
c8fcc360 | 71 | @code{ares}, |
2412d878 | 72 | @code{exynos-m1}, |
2fe9c2a0 | 73 | @code{falkor}, |
38e75bf2 | 74 | @code{neoverse-n1}, |
516dbc44 | 75 | @code{neoverse-e1}, |
6b21c2bf | 76 | @code{qdf24xx}, |
7605d944 | 77 | @code{saphira}, |
55fbd992 | 78 | @code{thunderx}, |
0a8be2fe | 79 | @code{vulcan}, |
0a9ce86d | 80 | @code{xgene1} |
df359aa7 | 81 | and |
0a9ce86d | 82 | @code{xgene2}. |
df359aa7 RE |
83 | The special name @code{all} may be used to allow the assembler to accept |
84 | instructions valid for any supported processor, including all optional | |
85 | extensions. | |
86 | ||
87 | In addition to the basic instruction set, the assembler can be told to | |
88 | accept, or restrict, various extension mnemonics that extend the | |
89 | processor. @xref{AArch64 Extensions}. | |
90 | ||
91 | If some implementations of a particular processor can have an | |
92 | extension, then then those extensions are automatically enabled. | |
93 | Consequently, you will not normally have to specify any additional | |
94 | extensions. | |
95 | ||
a05a5b64 | 96 | @cindex @option{-march=} command-line option, AArch64 |
df359aa7 RE |
97 | @item -march=@var{architecture}[+@var{extension}@dots{}] |
98 | This option specifies the target architecture. The assembler will | |
99 | issue an error message if an attempt is made to assemble an | |
100 | instruction which will not execute on the target architecture. The | |
acb787b0 | 101 | following architecture names are recognized: @code{armv8-a}, |
70d56181 | 102 | @code{armv8.1-a}, @code{armv8.2-a}, @code{armv8.3-a}, @code{armv8.4-a} |
8ae2d3d9 | 103 | @code{armv8.5-a}, and @code{armv8.6-a}. |
df359aa7 RE |
104 | |
105 | If both @option{-mcpu} and @option{-march} are specified, the | |
106 | assembler will use the setting for @option{-mcpu}. If neither are | |
107 | specified, the assembler will default to @option{-mcpu=all}. | |
108 | ||
109 | The architecture option can be extended with the same instruction set | |
110 | extension options as the @option{-mcpu} option. Unlike | |
111 | @option{-mcpu}, extensions are not always enabled by default, | |
112 | @xref{AArch64 Extensions}. | |
113 | ||
a05a5b64 | 114 | @cindex @code{-mverbose-error} command-line option, AArch64 |
a52e6fd3 YZ |
115 | @item -mverbose-error |
116 | This option enables verbose error messages for AArch64 gas. This option | |
117 | is enabled by default. | |
118 | ||
a05a5b64 | 119 | @cindex @code{-mno-verbose-error} command-line option, AArch64 |
a52e6fd3 YZ |
120 | @item -mno-verbose-error |
121 | This option disables verbose error messages in AArch64 gas. | |
122 | ||
a06ea964 NC |
123 | @end table |
124 | @c man end | |
125 | ||
df359aa7 RE |
126 | @node AArch64 Extensions |
127 | @section Architecture Extensions | |
128 | ||
129 | The table below lists the permitted architecture extensions that are | |
130 | supported by the assembler and the conditions under which they are | |
131 | automatically enabled. | |
132 | ||
133 | Multiple extensions may be specified, separated by a @code{+}. | |
134 | Extension mnemonics may also be removed from those the assembler | |
135 | accepts. This is done by prepending @code{no} to the option that adds | |
136 | the extension. Extensions that are removed must be listed after all | |
137 | extensions that have been added. | |
138 | ||
139 | Enabling an extension that requires other extensions will | |
140 | automatically cause those extensions to be enabled. Similarly, | |
141 | disabling an extension that is required by other extensions will | |
142 | automatically cause those extensions to be disabled. | |
143 | ||
144 | @multitable @columnfractions .12 .17 .17 .54 | |
145 | @headitem Extension @tab Minimum Architecture @tab Enabled by default | |
146 | @tab Description | |
df678013 MM |
147 | @item @code{bf16} @tab ARMv8.2-A @tab ARMv8.6-A or later |
148 | @tab Enable BFloat16 extension. | |
f482d304 RS |
149 | @item @code{compnum} @tab ARMv8.2-A @tab ARMv8.3-A or later |
150 | @tab Enable the complex number SIMD extensions. This implies | |
151 | @code{fp16} and @code{simd}. | |
af117b3c | 152 | @item @code{crc} @tab ARMv8-A @tab ARMv8.1-A or later |
df359aa7 RE |
153 | @tab Enable CRC instructions. |
154 | @item @code{crypto} @tab ARMv8-A @tab No | |
68ffd936 TC |
155 | @tab Enable cryptographic extensions. This implies @code{fp}, @code{simd}, @code{aes} and @code{sha2}. |
156 | @item @code{aes} @tab ARMv8-A @tab No | |
157 | @tab Enable the AES cryptographic extensions. This implies @code{fp} and @code{simd}. | |
158 | @item @code{sha2} @tab ARMv8-A @tab No | |
159 | @tab Enable the SHA2 cryptographic extensions. This implies @code{fp} and @code{simd}. | |
160 | @item @code{sha3} @tab ARMv8.2-A @tab No | |
161 | @tab Enable the ARMv8.2-A SHA2 and SHA3 cryptographic extensions. This implies @code{fp}, @code{simd} and @code{sha2}. | |
162 | @item @code{sm4} @tab ARMv8.2-A @tab No | |
163 | @tab Enable the ARMv8.2-A SM3 and SM4 cryptographic extensions. This implies @code{fp} and @code{simd}. | |
df359aa7 RE |
164 | @item @code{fp} @tab ARMv8-A @tab ARMv8-A or later |
165 | @tab Enable floating-point extensions. | |
87018195 MW |
166 | @item @code{fp16} @tab ARMv8.2-A @tab ARMv8.2-A or later |
167 | @tab Enable ARMv8.2 16-bit floating-point support. This implies | |
168 | @code{fp}. | |
b607cde1 JG |
169 | @item @code{lor} @tab ARMv8-A @tab ARMv8.1-A or later |
170 | @tab Enable Limited Ordering Regions extensions. | |
171 | @item @code{lse} @tab ARMv8-A @tab ARMv8.1-A or later | |
172 | @tab Enable Large System extensions. | |
173 | @item @code{pan} @tab ARMv8-A @tab ARMv8.1-A or later | |
174 | @tab Enable Privileged Access Never support. | |
73af8ed6 MW |
175 | @item @code{profile} @tab ARMv8.2-A @tab No |
176 | @tab Enable statistical profiling extensions. | |
50cc854c MW |
177 | @item @code{ras} @tab ARMv8-A @tab ARMv8.2-A or later |
178 | @tab Enable the Reliability, Availability and Serviceability | |
179 | extension. | |
01cca2f9 SN |
180 | @item @code{rcpc} @tab ARMv8.2-A @tab ARMv8.3-A or later |
181 | @tab Enable the weak release consistency extension. | |
b607cde1 JG |
182 | @item @code{rdma} @tab ARMv8-A @tab ARMv8.1-A or later |
183 | @tab Enable ARMv8.1 Advanced SIMD extensions. This implies @code{simd}. | |
184 | @item @code{simd} @tab ARMv8-A @tab ARMv8-A or later | |
185 | @tab Enable Advanced SIMD extensions. This implies @code{fp}. | |
582e12bf RS |
186 | @item @code{sve} @tab ARMv8.2-A @tab No |
187 | @tab Enable the Scalable Vector Extensions. This implies @code{fp16}, | |
188 | @code{simd} and @code{compnum}. | |
68ffd936 | 189 | @item @code{dotprod} @tab ARMv8.2-A @tab ARMv8.4-A or later |
65a55fbb | 190 | @tab Enable the Dot Product extension. This implies @code{simd}. |
d0f7791c TC |
191 | @item @code{fp16fml} @tab ARMv8.2-A @tab ARMv8.4-A or later |
192 | @tab Enable ARMv8.2 16-bit floating-point multiplication variant support. | |
193 | This implies @code{fp16}. | |
68dfbb92 SD |
194 | @item @code{sb} @tab ARMv8-A @tab ARMv8.5-A or later |
195 | @tab Enable the speculation barrier instruction sb. | |
2ac435d4 SD |
196 | @item @code{predres} @tab ARMv8-A @tab ARMv8.5-A or later |
197 | @tab Enable the Execution and Data and Prediction instructions. | |
af4bcb4c SD |
198 | @item @code{rng} @tab ARMv8.5-A @tab No |
199 | @tab Enable ARMv8.5-A random number instructions. | |
104fefee SD |
200 | @item @code{ssbs} @tab ARMv8-A @tab ARMv8.5-A or later |
201 | @tab Enable Speculative Store Bypassing Safe state read and write. | |
73b605ec SD |
202 | @item @code{memtag} @tab ARMv8.5-A @tab No |
203 | @tab Enable ARMv8.5-A Memory Tagging Extensions. | |
b83b4b13 SD |
204 | @item @code{tme} @tab ARMv8-A @tab No |
205 | @tab Enable Transactional Memory Extensions. | |
7ce2460a MM |
206 | @item @code{sve2} @tab ARMv8-A @tab No |
207 | @tab Enable the SVE2 Extension. | |
ccbdd22f | 208 | @item @code{sve2-bitperm} @tab ARMv8-A @tab No |
7ce2460a MM |
209 | @tab Enable SVE2 BITPERM Extension. |
210 | @item @code{sve2-sm4} @tab ARMv8-A @tab No | |
211 | @tab Enable SVE2 SM4 Extension. | |
212 | @item @code{sve2-aes} @tab ARMv8-A @tab No | |
41be57ca MM |
213 | @tab Enable SVE2 AES Extension. This also enables the .Q->.B form of the |
214 | @code{pmullt} and @code{pmullb} instructions. | |
7ce2460a MM |
215 | @item @code{sve2-sha3} @tab ARMv8-A @tab No |
216 | @tab Enable SVE2 SHA3 Extension. | |
df359aa7 RE |
217 | @end multitable |
218 | ||
a06ea964 NC |
219 | @node AArch64 Syntax |
220 | @section Syntax | |
221 | @menu | |
222 | * AArch64-Chars:: Special Characters | |
223 | * AArch64-Regs:: Register Names | |
224 | * AArch64-Relocations:: Relocations | |
225 | @end menu | |
226 | ||
227 | @node AArch64-Chars | |
228 | @subsection Special Characters | |
229 | ||
230 | @cindex line comment character, AArch64 | |
231 | @cindex AArch64 line comment character | |
232 | The presence of a @samp{//} on a line indicates the start of a comment | |
233 | that extends to the end of the current line. If a @samp{#} appears as | |
234 | the first character of a line, the whole line is treated as a comment. | |
235 | ||
236 | @cindex line separator, AArch64 | |
237 | @cindex statement separator, AArch64 | |
238 | @cindex AArch64 line separator | |
239 | The @samp{;} character can be used instead of a newline to separate | |
240 | statements. | |
241 | ||
242 | @cindex immediate character, AArch64 | |
243 | @cindex AArch64 immediate character | |
244 | The @samp{#} can be optionally used to indicate immediate operands. | |
245 | ||
246 | @node AArch64-Regs | |
247 | @subsection Register Names | |
248 | ||
249 | @cindex AArch64 register names | |
250 | @cindex register names, AArch64 | |
251 | Please refer to the section @samp{4.4 Register Names} of | |
252 | @samp{ARMv8 Instruction Set Overview}, which is available at | |
253 | @uref{http://infocenter.arm.com}. | |
254 | ||
255 | @node AArch64-Relocations | |
256 | @subsection Relocations | |
257 | ||
258 | @cindex relocations, AArch64 | |
259 | @cindex AArch64 relocations | |
260 | @cindex MOVN, MOVZ and MOVK group relocations, AArch64 | |
261 | Relocations for @samp{MOVZ} and @samp{MOVK} instructions can be generated | |
262 | by prefixing the label with @samp{#:abs_g2:} etc. | |
263 | For example to load the 48-bit absolute address of @var{foo} into x0: | |
264 | ||
265 | @smallexample | |
266 | movz x0, #:abs_g2:foo // bits 32-47, overflow check | |
267 | movk x0, #:abs_g1_nc:foo // bits 16-31, no overflow check | |
268 | movk x0, #:abs_g0_nc:foo // bits 0-15, no overflow check | |
269 | @end smallexample | |
270 | ||
271 | @cindex ADRP, ADD, LDR/STR group relocations, AArch64 | |
272 | Relocations for @samp{ADRP}, and @samp{ADD}, @samp{LDR} or @samp{STR} | |
273 | instructions can be generated by prefixing the label with | |
34fd659b | 274 | @samp{:pg_hi21:} and @samp{#:lo12:} respectively. |
a06ea964 | 275 | |
34bca508 | 276 | For example to use 33-bit (+/-4GB) pc-relative addressing to |
a06ea964 NC |
277 | load the address of @var{foo} into x0: |
278 | ||
279 | @smallexample | |
34fd659b | 280 | adrp x0, :pg_hi21:foo |
a06ea964 NC |
281 | add x0, x0, #:lo12:foo |
282 | @end smallexample | |
283 | ||
284 | Or to load the value of @var{foo} into x0: | |
285 | ||
286 | @smallexample | |
34fd659b | 287 | adrp x0, :pg_hi21:foo |
a06ea964 NC |
288 | ldr x0, [x0, #:lo12:foo] |
289 | @end smallexample | |
290 | ||
34fd659b | 291 | Note that @samp{:pg_hi21:} is optional. |
a06ea964 NC |
292 | |
293 | @smallexample | |
294 | adrp x0, foo | |
295 | @end smallexample | |
296 | ||
297 | is equivalent to | |
298 | ||
299 | @smallexample | |
34fd659b | 300 | adrp x0, :pg_hi21:foo |
a06ea964 NC |
301 | @end smallexample |
302 | ||
303 | @node AArch64 Floating Point | |
304 | @section Floating Point | |
305 | ||
306 | @cindex floating point, AArch64 (@sc{ieee}) | |
307 | @cindex AArch64 floating point (@sc{ieee}) | |
308 | The AArch64 architecture uses @sc{ieee} floating-point numbers. | |
309 | ||
310 | @node AArch64 Directives | |
311 | @section AArch64 Machine Directives | |
312 | ||
313 | @cindex machine directives, AArch64 | |
314 | @cindex AArch64 machine directives | |
315 | @table @code | |
316 | ||
317 | @c AAAAAAAAAAAAAAAAAAAAAAAAA | |
8e02d7f5 JW |
318 | |
319 | @cindex @code{.arch} directive, AArch64 | |
320 | @item .arch @var{name} | |
321 | Select the target architecture. Valid values for @var{name} are the same as | |
a05a5b64 | 322 | for the @option{-march} command-line option. |
8e02d7f5 JW |
323 | |
324 | Specifying @code{.arch} clears any previously selected architecture | |
325 | extensions. | |
326 | ||
327 | @cindex @code{.arch_extension} directive, AArch64 | |
328 | @item .arch_extension @var{name} | |
329 | Add or remove an architecture extension to the target architecture. Valid | |
330 | values for @var{name} are the same as those accepted as architectural | |
a05a5b64 | 331 | extensions by the @option{-mcpu} command-line option. |
8e02d7f5 JW |
332 | |
333 | @code{.arch_extension} may be used multiple times to add or remove extensions | |
334 | incrementally to the architecture being compiled for. | |
335 | ||
a06ea964 NC |
336 | @c BBBBBBBBBBBBBBBBBBBBBBBBBB |
337 | ||
338 | @cindex @code{.bss} directive, AArch64 | |
339 | @item .bss | |
340 | This directive switches to the @code{.bss} section. | |
341 | ||
342 | @c CCCCCCCCCCCCCCCCCCCCCCCCCC | |
30fab421 NC |
343 | |
344 | @cindex @code{.cpu} directive, AArch64 | |
345 | @item .cpu @var{name} | |
346 | Set the target processor. Valid values for @var{name} are the same as | |
a05a5b64 | 347 | those accepted by the @option{-mcpu=} command-line option. |
30fab421 | 348 | |
a06ea964 | 349 | @c DDDDDDDDDDDDDDDDDDDDDDDDDD |
30fab421 NC |
350 | |
351 | @cindex @code{.dword} directive, AArch64 | |
352 | @item .dword @var{expressions} | |
353 | The @code{.dword} directive produces 64 bit values. | |
354 | ||
a06ea964 | 355 | @c EEEEEEEEEEEEEEEEEEEEEEEEEE |
30fab421 NC |
356 | |
357 | @cindex @code{.even} directive, AArch64 | |
358 | @item .even | |
359 | The @code{.even} directive aligns the output on the next even byte | |
360 | boundary. | |
361 | ||
a06ea964 | 362 | @c FFFFFFFFFFFFFFFFFFFFFFFFFF |
b20d3859 BW |
363 | |
364 | @cindex @code{.float16} directive, AArch64 | |
365 | @item .float16 @var{value [,...,value_n]} | |
366 | Place the half precision floating point representation of one or more | |
367 | floating-point values into the current section. | |
368 | The format used to encode the floating point values is always the | |
369 | IEEE 754-2008 half precision floating point format. | |
370 | ||
a06ea964 NC |
371 | @c GGGGGGGGGGGGGGGGGGGGGGGGGG |
372 | @c HHHHHHHHHHHHHHHHHHHHHHHHHH | |
373 | @c IIIIIIIIIIIIIIIIIIIIIIIIII | |
30fab421 NC |
374 | |
375 | @cindex @code{.inst} directive, AArch64 | |
376 | @item .inst @var{expressions} | |
377 | Inserts the expressions into the output as if they were instructions, | |
378 | rather than data. | |
379 | ||
a06ea964 NC |
380 | @c JJJJJJJJJJJJJJJJJJJJJJJJJJ |
381 | @c KKKKKKKKKKKKKKKKKKKKKKKKKK | |
382 | @c LLLLLLLLLLLLLLLLLLLLLLLLLL | |
383 | ||
384 | @cindex @code{.ltorg} directive, AArch64 | |
385 | @item .ltorg | |
386 | This directive causes the current contents of the literal pool to be | |
387 | dumped into the current section (which is assumed to be the .text | |
388 | section) at the current location (aligned to a word boundary). | |
df359aa7 | 389 | GAS maintains a separate literal pool for each section and each |
a06ea964 NC |
390 | sub-section. The @code{.ltorg} directive will only affect the literal |
391 | pool of the current section and sub-section. At the end of assembly | |
392 | all remaining, un-empty literal pools will automatically be dumped. | |
393 | ||
df359aa7 | 394 | Note - older versions of GAS would dump the current literal |
a06ea964 NC |
395 | pool any time a section change occurred. This is no longer done, since |
396 | it prevents accurate control of the placement of literal pools. | |
397 | ||
398 | @c MMMMMMMMMMMMMMMMMMMMMMMMMM | |
399 | ||
400 | @c NNNNNNNNNNNNNNNNNNNNNNNNNN | |
401 | @c OOOOOOOOOOOOOOOOOOOOOOOOOO | |
402 | ||
403 | @c PPPPPPPPPPPPPPPPPPPPPPPPPP | |
404 | ||
405 | @cindex @code{.pool} directive, AArch64 | |
406 | @item .pool | |
407 | This is a synonym for .ltorg. | |
408 | ||
409 | @c QQQQQQQQQQQQQQQQQQQQQQQQQQ | |
410 | @c RRRRRRRRRRRRRRRRRRRRRRRRRR | |
411 | ||
412 | @cindex @code{.req} directive, AArch64 | |
413 | @item @var{name} .req @var{register name} | |
414 | This creates an alias for @var{register name} called @var{name}. For | |
415 | example: | |
416 | ||
417 | @smallexample | |
418 | foo .req w0 | |
419 | @end smallexample | |
420 | ||
8975f864 RR |
421 | ip0, ip1, lr and fp are automatically defined to |
422 | alias to X16, X17, X30 and X29 respectively. | |
423 | ||
a06ea964 NC |
424 | @c SSSSSSSSSSSSSSSSSSSSSSSSSS |
425 | ||
426 | @c TTTTTTTTTTTTTTTTTTTTTTTTTT | |
427 | ||
30fab421 NC |
428 | @cindex @code{.tlsdescadd} directive, AArch64 |
429 | @item @code{.tlsdescadd} | |
430 | Emits a TLSDESC_ADD reloc on the next instruction. | |
431 | ||
432 | @cindex @code{.tlsdesccall} directive, AArch64 | |
433 | @item @code{.tlsdesccall} | |
434 | Emits a TLSDESC_CALL reloc on the next instruction. | |
435 | ||
436 | @cindex @code{.tlsdescldr} directive, AArch64 | |
437 | @item @code{.tlsdescldr} | |
438 | Emits a TLSDESC_LDR reloc on the next instruction. | |
439 | ||
a06ea964 NC |
440 | @c UUUUUUUUUUUUUUUUUUUUUUUUUU |
441 | ||
442 | @cindex @code{.unreq} directive, AArch64 | |
443 | @item .unreq @var{alias-name} | |
444 | This undefines a register alias which was previously defined using the | |
445 | @code{req} directive. For example: | |
446 | ||
447 | @smallexample | |
448 | foo .req w0 | |
449 | .unreq foo | |
450 | @end smallexample | |
451 | ||
452 | An error occurs if the name is undefined. Note - this pseudo op can | |
453 | be used to delete builtin in register name aliases (eg 'w0'). This | |
454 | should only be done if it is really necessary. | |
455 | ||
456 | @c VVVVVVVVVVVVVVVVVVVVVVVVVV | |
457 | ||
f166ae01 SN |
458 | @cindex @code{.variant_pcs} directive, AArch64 |
459 | @item .variant_pcs @var{symbol} | |
460 | This directive marks @var{symbol} referencing a function that may | |
461 | follow a variant procedure call standard with different register | |
462 | usage convention from the base procedure call standard. | |
463 | ||
a06ea964 NC |
464 | @c WWWWWWWWWWWWWWWWWWWWWWWWWW |
465 | @c XXXXXXXXXXXXXXXXXXXXXXXXXX | |
a06ea964 | 466 | |
edc66de9 | 467 | @cindex @code{.xword} directive, AArch64 |
30fab421 NC |
468 | @item .xword @var{expressions} |
469 | The @code{.xword} directive produces 64 bit values. This is the same | |
470 | as the @code{.dword} directive. | |
471 | ||
472 | @c YYYYYYYYYYYYYYYYYYYYYYYYYY | |
473 | @c ZZZZZZZZZZZZZZZZZZZZZZZZZZ | |
edc66de9 | 474 | |
3a67e1a6 ST |
475 | @cindex @code{.cfi_b_key_frame} directive, AArch64 |
476 | @item @code{.cfi_b_key_frame} | |
477 | The @code{.cfi_b_key_frame} directive inserts a 'B' character into the CIE | |
478 | corresponding to the current frame's FDE, meaning that its return address has | |
479 | been signed with the B-key. If two frames are signed with differing keys then | |
480 | they will not share the same CIE. This information is intended to be used by | |
481 | the stack unwinder in order to properly authenticate return addresses. | |
482 | ||
a06ea964 NC |
483 | @end table |
484 | ||
485 | @node AArch64 Opcodes | |
486 | @section Opcodes | |
487 | ||
488 | @cindex AArch64 opcodes | |
489 | @cindex opcodes for AArch64 | |
df359aa7 | 490 | GAS implements all the standard AArch64 opcodes. It also |
a06ea964 | 491 | implements several pseudo opcodes, including several synthetic load |
34bca508 | 492 | instructions. |
a06ea964 NC |
493 | |
494 | @table @code | |
495 | ||
496 | @cindex @code{LDR reg,=<expr>} pseudo op, AArch64 | |
497 | @item LDR = | |
498 | @smallexample | |
499 | ldr <register> , =<expression> | |
500 | @end smallexample | |
501 | ||
502 | The constant expression will be placed into the nearest literal pool (if it not | |
503 | already there) and a PC-relative LDR instruction will be generated. | |
504 | ||
505 | @end table | |
506 | ||
507 | For more information on the AArch64 instruction set and assembly language | |
508 | notation, see @samp{ARMv8 Instruction Set Overview} available at | |
509 | @uref{http://infocenter.arm.com}. | |
510 | ||
511 | ||
512 | @node AArch64 Mapping Symbols | |
513 | @section Mapping Symbols | |
514 | ||
515 | The AArch64 ELF specification requires that special symbols be inserted | |
516 | into object files to mark certain features: | |
517 | ||
518 | @table @code | |
519 | ||
520 | @cindex @code{$x} | |
521 | @item $x | |
522 | At the start of a region of code containing AArch64 instructions. | |
523 | ||
524 | @cindex @code{$d} | |
525 | @item $d | |
526 | At the start of a region of data. | |
527 | ||
528 | @end table |