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78849248 | 1 | @c Copyright 1991, 1992, 1993, 1994, 1995, 1997, 1999, 2000, 2001, |
7c31ae13 | 2 | @c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 |
f7e42eb4 | 3 | @c Free Software Foundation, Inc. |
252b5132 RH |
4 | @c This is part of the GAS manual. |
5 | @c For copying conditions, see the file as.texinfo. | |
6 | @ifset GENERIC | |
7 | @page | |
8 | @node MIPS-Dependent | |
9 | @chapter MIPS Dependent Features | |
10 | @end ifset | |
11 | @ifclear GENERIC | |
12 | @node Machine Dependencies | |
13 | @chapter MIPS Dependent Features | |
14 | @end ifclear | |
15 | ||
16 | @cindex MIPS processor | |
17 | @sc{gnu} @code{@value{AS}} for @sc{mips} architectures supports several | |
84ea6cf2 | 18 | different @sc{mips} processors, and MIPS ISA levels I through V, MIPS32, |
584da044 NC |
19 | and MIPS64. For information about the @sc{mips} instruction set, see |
20 | @cite{MIPS RISC Architecture}, by Kane and Heindrich (Prentice-Hall). | |
21 | For an overview of @sc{mips} assembly conventions, see ``Appendix D: | |
22 | Assembly Language Programming'' in the same work. | |
252b5132 RH |
23 | |
24 | @menu | |
25 | * MIPS Opts:: Assembler options | |
26 | * MIPS Object:: ECOFF object code | |
27 | * MIPS Stabs:: Directives for debugging information | |
28 | * MIPS ISA:: Directives to override the ISA level | |
aed1a261 | 29 | * MIPS symbol sizes:: Directives to override the size of symbols |
252b5132 RH |
30 | * MIPS autoextend:: Directives for extending MIPS 16 bit instructions |
31 | * MIPS insn:: Directive to mark data as an instruction | |
32 | * MIPS option stack:: Directives to save and restore options | |
0eb7102d AJ |
33 | * MIPS ASE instruction generation overrides:: Directives to control |
34 | generation of MIPS ASE instructions | |
037b32b9 | 35 | * MIPS floating-point:: Directives to override floating-point options |
7c31ae13 | 36 | * MIPS Syntax:: MIPS specific syntactical considerations |
252b5132 RH |
37 | @end menu |
38 | ||
39 | @node MIPS Opts | |
40 | @section Assembler options | |
41 | ||
42 | The @sc{mips} configurations of @sc{gnu} @code{@value{AS}} support these | |
43 | special options: | |
44 | ||
45 | @table @code | |
46 | @cindex @code{-G} option (MIPS) | |
47 | @item -G @var{num} | |
48 | This option sets the largest size of an object that can be referenced | |
49 | implicitly with the @code{gp} register. It is only accepted for targets | |
50 | that use @sc{ecoff} format. The default value is 8. | |
51 | ||
52 | @cindex @code{-EB} option (MIPS) | |
53 | @cindex @code{-EL} option (MIPS) | |
54 | @cindex MIPS big-endian output | |
55 | @cindex MIPS little-endian output | |
56 | @cindex big-endian output, MIPS | |
57 | @cindex little-endian output, MIPS | |
58 | @item -EB | |
59 | @itemx -EL | |
60 | Any @sc{mips} configuration of @code{@value{AS}} can select big-endian or | |
61 | little-endian output at run time (unlike the other @sc{gnu} development | |
62 | tools, which must be configured for one or the other). Use @samp{-EB} | |
63 | to select big-endian output, and @samp{-EL} for little-endian. | |
64 | ||
0c000745 RS |
65 | @item -KPIC |
66 | @cindex PIC selection, MIPS | |
67 | @cindex @option{-KPIC} option, MIPS | |
68 | Generate SVR4-style PIC. This option tells the assembler to generate | |
69 | SVR4-style position-independent macro expansions. It also tells the | |
70 | assembler to mark the output file as PIC. | |
71 | ||
72 | @item -mvxworks-pic | |
73 | @cindex @option{-mvxworks-pic} option, MIPS | |
74 | Generate VxWorks PIC. This option tells the assembler to generate | |
75 | VxWorks-style position-independent macro expansions. | |
76 | ||
252b5132 RH |
77 | @cindex MIPS architecture options |
78 | @item -mips1 | |
79 | @itemx -mips2 | |
80 | @itemx -mips3 | |
81 | @itemx -mips4 | |
c67a084a | 82 | @itemx -mips5xo |
e7af610e | 83 | @itemx -mips32 |
af7ee8bf | 84 | @itemx -mips32r2 |
84ea6cf2 | 85 | @itemx -mips64 |
5f74bc13 | 86 | @itemx -mips64r2 |
252b5132 RH |
87 | Generate code for a particular MIPS Instruction Set Architecture level. |
88 | @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors, | |
89 | @samp{-mips2} to the @sc{r6000} processor, @samp{-mips3} to the | |
84ea6cf2 | 90 | @sc{r4000} processor, and @samp{-mips4} to the @sc{r8000} and |
5f74bc13 CD |
91 | @sc{r10000} processors. @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, |
92 | @samp{-mips64}, and @samp{-mips64r2} | |
93 | correspond to generic | |
94 | @sc{MIPS V}, @sc{MIPS32}, @sc{MIPS32 Release 2}, @sc{MIPS64}, | |
95 | and @sc{MIPS64 Release 2} | |
96 | ISA processors, respectively. You can also switch | |
584da044 | 97 | instruction sets during the assembly; see @ref{MIPS ISA, Directives to |
ec68c924 | 98 | override the ISA level}. |
252b5132 | 99 | |
6349b5f4 | 100 | @item -mgp32 |
ca4e0257 RS |
101 | @itemx -mfp32 |
102 | Some macros have different expansions for 32-bit and 64-bit registers. | |
103 | The register sizes are normally inferred from the ISA and ABI, but these | |
104 | flags force a certain group of registers to be treated as 32 bits wide at | |
105 | all times. @samp{-mgp32} controls the size of general-purpose registers | |
106 | and @samp{-mfp32} controls the size of floating-point registers. | |
107 | ||
ad3fea08 TS |
108 | The @code{.set gp=32} and @code{.set fp=32} directives allow the size |
109 | of registers to be changed for parts of an object. The default value is | |
110 | restored by @code{.set gp=default} and @code{.set fp=default}. | |
111 | ||
ca4e0257 RS |
112 | On some MIPS variants there is a 32-bit mode flag; when this flag is |
113 | set, 64-bit instructions generate a trap. Also, some 32-bit OSes only | |
114 | save the 32-bit registers on a context switch, so it is essential never | |
115 | to use the 64-bit registers. | |
6349b5f4 AH |
116 | |
117 | @item -mgp64 | |
ad3fea08 TS |
118 | @itemx -mfp64 |
119 | Assume that 64-bit registers are available. This is provided in the | |
120 | interests of symmetry with @samp{-mgp32} and @samp{-mfp32}. | |
121 | ||
122 | The @code{.set gp=64} and @code{.set fp=64} directives allow the size | |
123 | of registers to be changed for parts of an object. The default value is | |
124 | restored by @code{.set gp=default} and @code{.set fp=default}. | |
6349b5f4 | 125 | |
252b5132 RH |
126 | @item -mips16 |
127 | @itemx -no-mips16 | |
128 | Generate code for the MIPS 16 processor. This is equivalent to putting | |
ad3fea08 | 129 | @code{.set mips16} at the start of the assembly file. @samp{-no-mips16} |
252b5132 RH |
130 | turns off this option. |
131 | ||
df58fc94 RS |
132 | @item -mmicromips |
133 | @itemx -mno-micromips | |
134 | Generate code for the microMIPS processor. This is equivalent to putting | |
135 | @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips} | |
136 | turns off this option. This is equivalent to putting @code{.set nomicromips} | |
137 | at the start of the assembly file. | |
138 | ||
e16bfa71 TS |
139 | @item -msmartmips |
140 | @itemx -mno-smartmips | |
141 | Enables the SmartMIPS extensions to the MIPS32 instruction set, which | |
142 | provides a number of new instructions which target smartcard and | |
143 | cryptographic applications. This is equivalent to putting | |
ad3fea08 | 144 | @code{.set smartmips} at the start of the assembly file. |
e16bfa71 TS |
145 | @samp{-mno-smartmips} turns off this option. |
146 | ||
1f25f5d3 CD |
147 | @item -mips3d |
148 | @itemx -no-mips3d | |
149 | Generate code for the MIPS-3D Application Specific Extension. | |
150 | This tells the assembler to accept MIPS-3D instructions. | |
151 | @samp{-no-mips3d} turns off this option. | |
152 | ||
deec1734 CD |
153 | @item -mdmx |
154 | @itemx -no-mdmx | |
155 | Generate code for the MDMX Application Specific Extension. | |
156 | This tells the assembler to accept MDMX instructions. | |
157 | @samp{-no-mdmx} turns off this option. | |
158 | ||
2ef2b9ae CF |
159 | @item -mdsp |
160 | @itemx -mno-dsp | |
8b082fb1 TS |
161 | Generate code for the DSP Release 1 Application Specific Extension. |
162 | This tells the assembler to accept DSP Release 1 instructions. | |
2ef2b9ae CF |
163 | @samp{-mno-dsp} turns off this option. |
164 | ||
8b082fb1 TS |
165 | @item -mdspr2 |
166 | @itemx -mno-dspr2 | |
167 | Generate code for the DSP Release 2 Application Specific Extension. | |
168 | This option implies -mdsp. | |
169 | This tells the assembler to accept DSP Release 2 instructions. | |
170 | @samp{-mno-dspr2} turns off this option. | |
171 | ||
ef2e4d86 CF |
172 | @item -mmt |
173 | @itemx -mno-mt | |
174 | Generate code for the MT Application Specific Extension. | |
175 | This tells the assembler to accept MT instructions. | |
176 | @samp{-mno-mt} turns off this option. | |
177 | ||
dec0624d MR |
178 | @item -mmcu |
179 | @itemx -mno-mcu | |
180 | Generate code for the MCU Application Specific Extension. | |
181 | This tells the assembler to accept MCU instructions. | |
182 | @samp{-mno-mcu} turns off this option. | |
183 | ||
6b76fefe | 184 | @item -mfix7000 |
9ee72ff1 | 185 | @itemx -mno-fix7000 |
6b76fefe CM |
186 | Cause nops to be inserted if the read of the destination register |
187 | of an mfhi or mflo instruction occurs in the following two instructions. | |
188 | ||
c67a084a NC |
189 | @item -mfix-loongson2f-jump |
190 | @itemx -mno-fix-loongson2f-jump | |
191 | Eliminate instruction fetch from outside 256M region to work around the | |
192 | Loongson2F @samp{jump} instructions. Without it, under extreme cases, | |
193 | the kernel may crash. The issue has been solved in latest processor | |
194 | batches, but this fix has no side effect to them. | |
195 | ||
196 | @item -mfix-loongson2f-nop | |
197 | @itemx -mno-fix-loongson2f-nop | |
198 | Replace nops by @code{or at,at,zero} to work around the Loongson2F | |
199 | @samp{nop} errata. Without it, under extreme cases, cpu might | |
200 | deadlock. The issue has been solved in latest loongson2f batches, but | |
201 | this fix has no side effect to them. | |
202 | ||
d766e8ec | 203 | @item -mfix-vr4120 |
2babba43 | 204 | @itemx -mno-fix-vr4120 |
d766e8ec RS |
205 | Insert nops to work around certain VR4120 errata. This option is |
206 | intended to be used on GCC-generated code: it is not designed to catch | |
207 | all problems in hand-written assembler code. | |
60b63b72 | 208 | |
11db99f8 | 209 | @item -mfix-vr4130 |
2babba43 | 210 | @itemx -mno-fix-vr4130 |
11db99f8 RS |
211 | Insert nops to work around the VR4130 @samp{mflo}/@samp{mfhi} errata. |
212 | ||
6a32d874 CM |
213 | @item -mfix-24k |
214 | @itemx -no-mfix-24k | |
215 | Insert nops to work around the 24K @samp{eret}/@samp{deret} errata. | |
216 | ||
d954098f DD |
217 | @item -mfix-cn63xxp1 |
218 | @itemx -mno-fix-cn63xxp1 | |
219 | Replace @code{pref} hints 0 - 4 and 6 - 24 with hint 28 to work around | |
220 | certain CN63XXP1 errata. | |
221 | ||
252b5132 RH |
222 | @item -m4010 |
223 | @itemx -no-m4010 | |
224 | Generate code for the LSI @sc{r4010} chip. This tells the assembler to | |
225 | accept the @sc{r4010} specific instructions (@samp{addciu}, @samp{ffc}, | |
226 | etc.), and to not schedule @samp{nop} instructions around accesses to | |
227 | the @samp{HI} and @samp{LO} registers. @samp{-no-m4010} turns off this | |
228 | option. | |
229 | ||
230 | @item -m4650 | |
231 | @itemx -no-m4650 | |
232 | Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept | |
233 | the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop} | |
234 | instructions around accesses to the @samp{HI} and @samp{LO} registers. | |
235 | @samp{-no-m4650} turns off this option. | |
236 | ||
237 | @itemx -m3900 | |
238 | @itemx -no-m3900 | |
239 | @itemx -m4100 | |
240 | @itemx -no-m4100 | |
241 | For each option @samp{-m@var{nnnn}}, generate code for the MIPS | |
242 | @sc{r@var{nnnn}} chip. This tells the assembler to accept instructions | |
243 | specific to that chip, and to schedule for that chip's hazards. | |
244 | ||
ec68c924 | 245 | @item -march=@var{cpu} |
252b5132 RH |
246 | Generate code for a particular MIPS cpu. It is exactly equivalent to |
247 | @samp{-m@var{cpu}}, except that there are more value of @var{cpu} | |
248 | understood. Valid @var{cpu} value are: | |
249 | ||
250 | @quotation | |
251 | 2000, | |
252 | 3000, | |
253 | 3900, | |
254 | 4000, | |
255 | 4010, | |
256 | 4100, | |
257 | 4111, | |
60b63b72 RS |
258 | vr4120, |
259 | vr4130, | |
260 | vr4181, | |
252b5132 RH |
261 | 4300, |
262 | 4400, | |
263 | 4600, | |
264 | 4650, | |
265 | 5000, | |
b946ec34 NC |
266 | rm5200, |
267 | rm5230, | |
268 | rm5231, | |
269 | rm5261, | |
270 | rm5721, | |
60b63b72 RS |
271 | vr5400, |
272 | vr5500, | |
252b5132 | 273 | 6000, |
b946ec34 | 274 | rm7000, |
252b5132 | 275 | 8000, |
963ac363 | 276 | rm9000, |
e7af610e | 277 | 10000, |
18ae5d72 | 278 | 12000, |
3aa3176b TS |
279 | 14000, |
280 | 16000, | |
ad3fea08 TS |
281 | 4kc, |
282 | 4km, | |
283 | 4kp, | |
284 | 4ksc, | |
285 | 4kec, | |
286 | 4kem, | |
287 | 4kep, | |
288 | 4ksd, | |
289 | m4k, | |
290 | m4kp, | |
b5503c7b MR |
291 | m14k, |
292 | m14kc, | |
7a795ef4 MR |
293 | m14ke, |
294 | m14kec, | |
ad3fea08 | 295 | 24kc, |
0fdf1951 | 296 | 24kf2_1, |
ad3fea08 | 297 | 24kf, |
0fdf1951 | 298 | 24kf1_1, |
ad3fea08 | 299 | 24kec, |
0fdf1951 | 300 | 24kef2_1, |
ad3fea08 | 301 | 24kef, |
0fdf1951 | 302 | 24kef1_1, |
ad3fea08 | 303 | 34kc, |
0fdf1951 | 304 | 34kf2_1, |
ad3fea08 | 305 | 34kf, |
0fdf1951 | 306 | 34kf1_1, |
f281862d | 307 | 74kc, |
0fdf1951 | 308 | 74kf2_1, |
f281862d | 309 | 74kf, |
0fdf1951 RS |
310 | 74kf1_1, |
311 | 74kf3_2, | |
30f8113a SL |
312 | 1004kc, |
313 | 1004kf2_1, | |
314 | 1004kf, | |
315 | 1004kf1_1, | |
ad3fea08 TS |
316 | 5kc, |
317 | 5kf, | |
318 | 20kc, | |
319 | 25kf, | |
82100185 | 320 | sb1, |
350cc38d MS |
321 | sb1a, |
322 | loongson2e, | |
037b32b9 | 323 | loongson2f, |
fd503541 | 324 | loongson3a, |
52b6b6b9 JM |
325 | octeon, |
326 | xlr | |
252b5132 RH |
327 | @end quotation |
328 | ||
0fdf1951 RS |
329 | For compatibility reasons, @samp{@var{n}x} and @samp{@var{b}fx} are |
330 | accepted as synonyms for @samp{@var{n}f1_1}. These values are | |
331 | deprecated. | |
332 | ||
ec68c924 EC |
333 | @item -mtune=@var{cpu} |
334 | Schedule and tune for a particular MIPS cpu. Valid @var{cpu} values are | |
335 | identical to @samp{-march=@var{cpu}}. | |
336 | ||
316f5878 RS |
337 | @item -mabi=@var{abi} |
338 | Record which ABI the source code uses. The recognized arguments | |
339 | are: @samp{32}, @samp{n32}, @samp{o64}, @samp{64} and @samp{eabi}. | |
252b5132 | 340 | |
aed1a261 RS |
341 | @item -msym32 |
342 | @itemx -mno-sym32 | |
343 | @cindex -msym32 | |
344 | @cindex -mno-sym32 | |
345 | Equivalent to adding @code{.set sym32} or @code{.set nosym32} to | |
346 | the beginning of the assembler input. @xref{MIPS symbol sizes}. | |
347 | ||
252b5132 RH |
348 | @cindex @code{-nocpp} ignored (MIPS) |
349 | @item -nocpp | |
350 | This option is ignored. It is accepted for command-line compatibility with | |
351 | other assemblers, which use it to turn off C style preprocessing. With | |
352 | @sc{gnu} @code{@value{AS}}, there is no need for @samp{-nocpp}, because the | |
353 | @sc{gnu} assembler itself never runs the C preprocessor. | |
354 | ||
037b32b9 AN |
355 | @item -msoft-float |
356 | @itemx -mhard-float | |
357 | Disable or enable floating-point instructions. Note that by default | |
358 | floating-point instructions are always allowed even with CPU targets | |
359 | that don't have support for these instructions. | |
360 | ||
361 | @item -msingle-float | |
362 | @itemx -mdouble-float | |
363 | Disable or enable double-precision floating-point operations. Note | |
364 | that by default double-precision floating-point operations are always | |
365 | allowed even with CPU targets that don't have support for these | |
366 | operations. | |
367 | ||
119d663a NC |
368 | @item --construct-floats |
369 | @itemx --no-construct-floats | |
119d663a NC |
370 | The @code{--no-construct-floats} option disables the construction of |
371 | double width floating point constants by loading the two halves of the | |
372 | value into the two single width floating point registers that make up | |
373 | the double width register. This feature is useful if the processor | |
374 | support the FR bit in its status register, and this bit is known (by | |
375 | the programmer) to be set. This bit prevents the aliasing of the double | |
376 | width register by the single width registers. | |
377 | ||
63bf5651 | 378 | By default @code{--construct-floats} is selected, allowing construction |
119d663a NC |
379 | of these floating point constants. |
380 | ||
252b5132 RH |
381 | @item --trap |
382 | @itemx --no-break | |
383 | @c FIXME! (1) reflect these options (next item too) in option summaries; | |
384 | @c (2) stop teasing, say _which_ instructions expanded _how_. | |
385 | @code{@value{AS}} automatically macro expands certain division and | |
386 | multiplication instructions to check for overflow and division by zero. This | |
387 | option causes @code{@value{AS}} to generate code to take a trap exception | |
388 | rather than a break exception when an error is detected. The trap instructions | |
389 | are only supported at Instruction Set Architecture level 2 and higher. | |
390 | ||
391 | @item --break | |
392 | @itemx --no-trap | |
393 | Generate code to take a break exception rather than a trap exception when an | |
394 | error is detected. This is the default. | |
63486801 | 395 | |
dcd410fe RO |
396 | @item -mpdr |
397 | @itemx -mno-pdr | |
398 | Control generation of @code{.pdr} sections. Off by default on IRIX, on | |
399 | elsewhere. | |
aa6975fb ILT |
400 | |
401 | @item -mshared | |
402 | @itemx -mno-shared | |
403 | When generating code using the Unix calling conventions (selected by | |
404 | @samp{-KPIC} or @samp{-mcall_shared}), gas will normally generate code | |
405 | which can go into a shared library. The @samp{-mno-shared} option | |
406 | tells gas to generate code which uses the calling convention, but can | |
407 | not go into a shared library. The resulting code is slightly more | |
408 | efficient. This option only affects the handling of the | |
409 | @samp{.cpload} and @samp{.cpsetup} pseudo-ops. | |
252b5132 RH |
410 | @end table |
411 | ||
412 | @node MIPS Object | |
413 | @section MIPS ECOFF object code | |
414 | ||
415 | @cindex ECOFF sections | |
416 | @cindex MIPS ECOFF sections | |
417 | Assembling for a @sc{mips} @sc{ecoff} target supports some additional sections | |
418 | besides the usual @code{.text}, @code{.data} and @code{.bss}. The | |
419 | additional sections are @code{.rdata}, used for read-only data, | |
420 | @code{.sdata}, used for small data, and @code{.sbss}, used for small | |
421 | common objects. | |
422 | ||
423 | @cindex small objects, MIPS ECOFF | |
424 | @cindex @code{gp} register, MIPS | |
425 | When assembling for @sc{ecoff}, the assembler uses the @code{$gp} (@code{$28}) | |
426 | register to form the address of a ``small object''. Any object in the | |
427 | @code{.sdata} or @code{.sbss} sections is considered ``small'' in this sense. | |
428 | For external objects, or for objects in the @code{.bss} section, you can use | |
429 | the @code{@value{GCC}} @samp{-G} option to control the size of objects addressed via | |
430 | @code{$gp}; the default value is 8, meaning that a reference to any object | |
431 | eight bytes or smaller uses @code{$gp}. Passing @samp{-G 0} to | |
432 | @code{@value{AS}} prevents it from using the @code{$gp} register on the basis | |
433 | of object size (but the assembler uses @code{$gp} for objects in @code{.sdata} | |
434 | or @code{sbss} in any case). The size of an object in the @code{.bss} section | |
435 | is set by the @code{.comm} or @code{.lcomm} directive that defines it. The | |
436 | size of an external object may be set with the @code{.extern} directive. For | |
437 | example, @samp{.extern sym,4} declares that the object at @code{sym} is 4 bytes | |
438 | in length, whie leaving @code{sym} otherwise undefined. | |
439 | ||
440 | Using small @sc{ecoff} objects requires linker support, and assumes that the | |
441 | @code{$gp} register is correctly initialized (normally done automatically by | |
442 | the startup code). @sc{mips} @sc{ecoff} assembly code must not modify the | |
443 | @code{$gp} register. | |
444 | ||
445 | @node MIPS Stabs | |
446 | @section Directives for debugging information | |
447 | ||
448 | @cindex MIPS debugging directives | |
449 | @sc{mips} @sc{ecoff} @code{@value{AS}} supports several directives used for | |
450 | generating debugging information which are not support by traditional @sc{mips} | |
451 | assemblers. These are @code{.def}, @code{.endef}, @code{.dim}, @code{.file}, | |
452 | @code{.scl}, @code{.size}, @code{.tag}, @code{.type}, @code{.val}, | |
453 | @code{.stabd}, @code{.stabn}, and @code{.stabs}. The debugging information | |
454 | generated by the three @code{.stab} directives can only be read by @sc{gdb}, | |
455 | not by traditional @sc{mips} debuggers (this enhancement is required to fully | |
456 | support C++ debugging). These directives are primarily used by compilers, not | |
457 | assembly language programmers! | |
458 | ||
aed1a261 RS |
459 | @node MIPS symbol sizes |
460 | @section Directives to override the size of symbols | |
461 | ||
462 | @cindex @code{.set sym32} | |
463 | @cindex @code{.set nosym32} | |
464 | The n64 ABI allows symbols to have any 64-bit value. Although this | |
465 | provides a great deal of flexibility, it means that some macros have | |
466 | much longer expansions than their 32-bit counterparts. For example, | |
467 | the non-PIC expansion of @samp{dla $4,sym} is usually: | |
468 | ||
469 | @smallexample | |
470 | lui $4,%highest(sym) | |
471 | lui $1,%hi(sym) | |
472 | daddiu $4,$4,%higher(sym) | |
473 | daddiu $1,$1,%lo(sym) | |
474 | dsll32 $4,$4,0 | |
475 | daddu $4,$4,$1 | |
476 | @end smallexample | |
477 | ||
478 | whereas the 32-bit expansion is simply: | |
479 | ||
480 | @smallexample | |
481 | lui $4,%hi(sym) | |
482 | daddiu $4,$4,%lo(sym) | |
483 | @end smallexample | |
484 | ||
485 | n64 code is sometimes constructed in such a way that all symbolic | |
486 | constants are known to have 32-bit values, and in such cases, it's | |
487 | preferable to use the 32-bit expansion instead of the 64-bit | |
488 | expansion. | |
489 | ||
490 | You can use the @code{.set sym32} directive to tell the assembler | |
491 | that, from this point on, all expressions of the form | |
492 | @samp{@var{symbol}} or @samp{@var{symbol} + @var{offset}} | |
493 | have 32-bit values. For example: | |
494 | ||
495 | @smallexample | |
496 | .set sym32 | |
497 | dla $4,sym | |
498 | lw $4,sym+16 | |
499 | sw $4,sym+0x8000($4) | |
500 | @end smallexample | |
501 | ||
502 | will cause the assembler to treat @samp{sym}, @code{sym+16} and | |
503 | @code{sym+0x8000} as 32-bit values. The handling of non-symbolic | |
504 | addresses is not affected. | |
505 | ||
506 | The directive @code{.set nosym32} ends a @code{.set sym32} block and | |
507 | reverts to the normal behavior. It is also possible to change the | |
508 | symbol size using the command-line options @option{-msym32} and | |
509 | @option{-mno-sym32}. | |
510 | ||
511 | These options and directives are always accepted, but at present, | |
512 | they have no effect for anything other than n64. | |
513 | ||
252b5132 RH |
514 | @node MIPS ISA |
515 | @section Directives to override the ISA level | |
516 | ||
517 | @cindex MIPS ISA override | |
518 | @kindex @code{.set mips@var{n}} | |
519 | @sc{gnu} @code{@value{AS}} supports an additional directive to change | |
520 | the @sc{mips} Instruction Set Architecture level on the fly: @code{.set | |
5f74bc13 CD |
521 | mips@var{n}}. @var{n} should be a number from 0 to 5, or 32, 32r2, 64 |
522 | or 64r2. | |
071742cf | 523 | The values other than 0 make the assembler accept instructions |
584da044 NC |
524 | for the corresponding @sc{isa} level, from that point on in the |
525 | assembly. @code{.set mips@var{n}} affects not only which instructions | |
526 | are permitted, but also how certain macros are expanded. @code{.set | |
527 | mips0} restores the @sc{isa} level to its original level: either the | |
528 | level you selected with command line options, or the default for your | |
ad3fea08 | 529 | configuration. You can use this feature to permit specific @sc{mips3} |
584da044 | 530 | instructions while assembling in 32 bit mode. Use this directive with |
ec68c924 | 531 | care! |
252b5132 | 532 | |
ad3fea08 TS |
533 | @cindex MIPS CPU override |
534 | @kindex @code{.set arch=@var{cpu}} | |
535 | The @code{.set arch=@var{cpu}} directive provides even finer control. | |
536 | It changes the effective CPU target and allows the assembler to use | |
537 | instructions specific to a particular CPU. All CPUs supported by the | |
538 | @samp{-march} command line option are also selectable by this directive. | |
539 | The original value is restored by @code{.set arch=default}. | |
252b5132 | 540 | |
ad3fea08 TS |
541 | The directive @code{.set mips16} puts the assembler into MIPS 16 mode, |
542 | in which it will assemble instructions for the MIPS 16 processor. Use | |
543 | @code{.set nomips16} to return to normal 32 bit mode. | |
e16bfa71 | 544 | |
ec68c924 | 545 | Traditional @sc{mips} assemblers do not support this directive. |
252b5132 | 546 | |
df58fc94 RS |
547 | The directive @code{.set micromips} puts the assembler into microMIPS mode, |
548 | in which it will assemble instructions for the microMIPS processor. Use | |
549 | @code{.set nomicromips} to return to normal 32 bit mode. | |
550 | ||
551 | Traditional @sc{mips} assemblers do not support this directive. | |
552 | ||
252b5132 RH |
553 | @node MIPS autoextend |
554 | @section Directives for extending MIPS 16 bit instructions | |
555 | ||
556 | @kindex @code{.set autoextend} | |
557 | @kindex @code{.set noautoextend} | |
558 | By default, MIPS 16 instructions are automatically extended to 32 bits | |
ad3fea08 TS |
559 | when necessary. The directive @code{.set noautoextend} will turn this |
560 | off. When @code{.set noautoextend} is in effect, any 32 bit instruction | |
561 | must be explicitly extended with the @code{.e} modifier (e.g., | |
562 | @code{li.e $4,1000}). The directive @code{.set autoextend} may be used | |
252b5132 RH |
563 | to once again automatically extend instructions when necessary. |
564 | ||
565 | This directive is only meaningful when in MIPS 16 mode. Traditional | |
566 | @sc{mips} assemblers do not support this directive. | |
567 | ||
568 | @node MIPS insn | |
569 | @section Directive to mark data as an instruction | |
570 | ||
571 | @kindex @code{.insn} | |
572 | The @code{.insn} directive tells @code{@value{AS}} that the following | |
df58fc94 RS |
573 | data is actually instructions. This makes a difference in MIPS 16 and |
574 | microMIPS modes: when loading the address of a label which precedes | |
575 | instructions, @code{@value{AS}} automatically adds 1 to the value, so | |
576 | that jumping to the loaded address will do the right thing. | |
252b5132 | 577 | |
a946d7e3 NC |
578 | @kindex @code{.global} |
579 | The @code{.global} and @code{.globl} directives supported by | |
580 | @code{@value{AS}} will by default mark the symbol as pointing to a | |
581 | region of data not code. This means that, for example, any | |
582 | instructions following such a symbol will not be disassembled by | |
f746e6b9 | 583 | @code{objdump} as it will regard them as data. To change this |
a946d7e3 NC |
584 | behaviour an optional section name can be placed after the symbol name |
585 | in the @code{.global} directive. If this section exists and is known | |
586 | to be a code section, then the symbol will be marked as poiting at | |
587 | code not data. Ie the syntax for the directive is: | |
588 | ||
589 | @code{.global @var{symbol}[ @var{section}][, @var{symbol}[ @var{section}]] ...}, | |
590 | ||
591 | Here is a short example: | |
592 | ||
593 | @example | |
594 | .global foo .text, bar, baz .data | |
595 | foo: | |
596 | nop | |
597 | bar: | |
598 | .word 0x0 | |
599 | baz: | |
600 | .word 0x1 | |
601 | ||
602 | @end example | |
603 | ||
252b5132 RH |
604 | @node MIPS option stack |
605 | @section Directives to save and restore options | |
606 | ||
607 | @cindex MIPS option stack | |
608 | @kindex @code{.set push} | |
609 | @kindex @code{.set pop} | |
610 | The directives @code{.set push} and @code{.set pop} may be used to save | |
611 | and restore the current settings for all the options which are | |
612 | controlled by @code{.set}. The @code{.set push} directive saves the | |
613 | current settings on a stack. The @code{.set pop} directive pops the | |
614 | stack and restores the settings. | |
615 | ||
616 | These directives can be useful inside an macro which must change an | |
617 | option such as the ISA level or instruction reordering but does not want | |
618 | to change the state of the code which invoked the macro. | |
619 | ||
620 | Traditional @sc{mips} assemblers do not support these directives. | |
1f25f5d3 CD |
621 | |
622 | @node MIPS ASE instruction generation overrides | |
623 | @section Directives to control generation of MIPS ASE instructions | |
624 | ||
625 | @cindex MIPS MIPS-3D instruction generation override | |
626 | @kindex @code{.set mips3d} | |
627 | @kindex @code{.set nomips3d} | |
628 | The directive @code{.set mips3d} makes the assembler accept instructions | |
629 | from the MIPS-3D Application Specific Extension from that point on | |
630 | in the assembly. The @code{.set nomips3d} directive prevents MIPS-3D | |
631 | instructions from being accepted. | |
632 | ||
ad3fea08 TS |
633 | @cindex SmartMIPS instruction generation override |
634 | @kindex @code{.set smartmips} | |
635 | @kindex @code{.set nosmartmips} | |
636 | The directive @code{.set smartmips} makes the assembler accept | |
637 | instructions from the SmartMIPS Application Specific Extension to the | |
638 | MIPS32 @sc{isa} from that point on in the assembly. The | |
639 | @code{.set nosmartmips} directive prevents SmartMIPS instructions from | |
640 | being accepted. | |
641 | ||
deec1734 CD |
642 | @cindex MIPS MDMX instruction generation override |
643 | @kindex @code{.set mdmx} | |
644 | @kindex @code{.set nomdmx} | |
645 | The directive @code{.set mdmx} makes the assembler accept instructions | |
646 | from the MDMX Application Specific Extension from that point on | |
647 | in the assembly. The @code{.set nomdmx} directive prevents MDMX | |
648 | instructions from being accepted. | |
649 | ||
8b082fb1 | 650 | @cindex MIPS DSP Release 1 instruction generation override |
2ef2b9ae CF |
651 | @kindex @code{.set dsp} |
652 | @kindex @code{.set nodsp} | |
653 | The directive @code{.set dsp} makes the assembler accept instructions | |
8b082fb1 TS |
654 | from the DSP Release 1 Application Specific Extension from that point |
655 | on in the assembly. The @code{.set nodsp} directive prevents DSP | |
656 | Release 1 instructions from being accepted. | |
657 | ||
658 | @cindex MIPS DSP Release 2 instruction generation override | |
659 | @kindex @code{.set dspr2} | |
660 | @kindex @code{.set nodspr2} | |
661 | The directive @code{.set dspr2} makes the assembler accept instructions | |
662 | from the DSP Release 2 Application Specific Extension from that point | |
663 | on in the assembly. This dirctive implies @code{.set dsp}. The | |
664 | @code{.set nodspr2} directive prevents DSP Release 2 instructions from | |
665 | being accepted. | |
2ef2b9ae | 666 | |
ef2e4d86 CF |
667 | @cindex MIPS MT instruction generation override |
668 | @kindex @code{.set mt} | |
669 | @kindex @code{.set nomt} | |
670 | The directive @code{.set mt} makes the assembler accept instructions | |
671 | from the MT Application Specific Extension from that point on | |
672 | in the assembly. The @code{.set nomt} directive prevents MT | |
673 | instructions from being accepted. | |
674 | ||
dec0624d MR |
675 | @cindex MIPS MCU instruction generation override |
676 | @kindex @code{.set mcu} | |
677 | @kindex @code{.set nomcu} | |
678 | The directive @code{.set mcu} makes the assembler accept instructions | |
679 | from the MCU Application Specific Extension from that point on | |
680 | in the assembly. The @code{.set nomcu} directive prevents MCU | |
681 | instructions from being accepted. | |
682 | ||
1f25f5d3 | 683 | Traditional @sc{mips} assemblers do not support these directives. |
037b32b9 AN |
684 | |
685 | @node MIPS floating-point | |
686 | @section Directives to override floating-point options | |
687 | ||
688 | @cindex Disable floating-point instructions | |
689 | @kindex @code{.set softfloat} | |
690 | @kindex @code{.set hardfloat} | |
691 | The directives @code{.set softfloat} and @code{.set hardfloat} provide | |
692 | finer control of disabling and enabling float-point instructions. | |
693 | These directives always override the default (that hard-float | |
694 | instructions are accepted) or the command-line options | |
695 | (@samp{-msoft-float} and @samp{-mhard-float}). | |
696 | ||
697 | @cindex Disable single-precision floating-point operations | |
605b1dd4 NH |
698 | @kindex @code{.set singlefloat} |
699 | @kindex @code{.set doublefloat} | |
037b32b9 AN |
700 | The directives @code{.set singlefloat} and @code{.set doublefloat} |
701 | provide finer control of disabling and enabling double-precision | |
702 | float-point operations. These directives always override the default | |
703 | (that double-precision operations are accepted) or the command-line | |
704 | options (@samp{-msingle-float} and @samp{-mdouble-float}). | |
705 | ||
706 | Traditional @sc{mips} assemblers do not support these directives. | |
7c31ae13 NC |
707 | |
708 | @node MIPS Syntax | |
709 | @section Syntactical considerations for the MIPS assembler | |
710 | @menu | |
711 | * MIPS-Chars:: Special Characters | |
712 | @end menu | |
713 | ||
714 | @node MIPS-Chars | |
715 | @subsection Special Characters | |
716 | ||
717 | @cindex line comment character, MIPS | |
718 | @cindex MIPS line comment character | |
719 | The presence of a @samp{#} on a line indicates the start of a comment | |
720 | that extends to the end of the current line. | |
721 | ||
722 | If a @samp{#} appears as the first character of a line, the whole line | |
723 | is treated as a comment, but in this case the line can also be a | |
724 | logical line number directive (@pxref{Comments}) or a | |
725 | preprocessor control command (@pxref{Preprocessing}). | |
726 | ||
727 | @cindex line separator, MIPS | |
728 | @cindex statement separator, MIPS | |
729 | @cindex MIPS line separator | |
730 | The @samp{;} character can be used to separate statements on the same | |
731 | line. |