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a2c58332 | 1 | @c Copyright (C) 2016-2022 Free Software Foundation, Inc. |
e23eba97 NC |
2 | @c This is part of the GAS anual. |
3 | @c For copying conditions, see the file as.texinfo | |
4 | @c man end | |
5 | ||
6 | @ifset GENERIC | |
7 | @page | |
8 | @node RISC-V-Dependent | |
9 | @chapter RISC-V Dependent Features | |
10 | @end ifset | |
11 | @ifclear GENERIC | |
12 | @node Machine Dependencies | |
13 | @chapter RISC-V Dependent Features | |
14 | @end ifclear | |
15 | ||
16 | @cindex RISC-V support | |
17 | @menu | |
b57e49f7 JW |
18 | * RISC-V-Options:: RISC-V Options |
19 | * RISC-V-Directives:: RISC-V Directives | |
de48783e | 20 | * RISC-V-Modifiers:: RISC-V Assembler Modifiers |
0e35537d | 21 | * RISC-V-Formats:: RISC-V Instruction Formats |
2dc8dd17 | 22 | * RISC-V-ATTRIBUTE:: RISC-V Object Attribute |
e23eba97 NC |
23 | @end menu |
24 | ||
b57e49f7 JW |
25 | @node RISC-V-Options |
26 | @section RISC-V Options | |
e23eba97 | 27 | |
b57e49f7 | 28 | The following table lists all available RISC-V specific options. |
e23eba97 NC |
29 | |
30 | @c man begin OPTIONS | |
31 | @table @gcctabopt | |
e23eba97 | 32 | |
19683c04 PD |
33 | @cindex @samp{-fpic} option, RISC-V |
34 | @item -fpic | |
b57e49f7 | 35 | @itemx -fPIC |
19683c04 PD |
36 | Generate position-independent code |
37 | ||
38 | @cindex @samp{-fno-pic} option, RISC-V | |
39 | @item -fno-pic | |
40 | Don't generate position-independent code (default) | |
41 | ||
4f7eddc4 PD |
42 | @cindex @samp{-march=ISA} option, RISC-V |
43 | @item -march=ISA | |
2922d21d | 44 | Select the base isa, as specified by ISA. For example -march=rv32ima. |
338d56a8 | 45 | If this option and the architecture attributes aren't set, then assembler |
8f595e9b NC |
46 | will check the default configure setting --with-arch=ISA. |
47 | ||
48 | @cindex @samp{-misa-spec=ISAspec} option, RISC-V | |
49 | @item -misa-spec=ISAspec | |
50 | Select the default isa spec version. If the version of ISA isn't set | |
51 | by -march, then assembler helps to set the version according to | |
52 | the default chosen spec. If this option isn't set, then assembler will | |
53 | check the default configure setting --with-isa-spec=ISAspec. | |
54 | ||
55 | @cindex @samp{-mpriv-spec=PRIVspec} option, RISC-V | |
56 | @item -mpriv-spec=PRIVspec | |
57 | Select the privileged spec version. We can decide whether the CSR is valid or | |
58 | not according to the chosen spec. If this option and the privilege attributes | |
59 | aren't set, then assembler will check the default configure setting | |
60 | --with-priv-spec=PRIVspec. | |
2922d21d AW |
61 | |
62 | @cindex @samp{-mabi=ABI} option, RISC-V | |
63 | @item -mabi=ABI | |
64 | Selects the ABI, which is either "ilp32" or "lp64", optionally followed | |
65 | by "f", "d", or "q" to indicate single-precision, double-precision, or | |
66 | quad-precision floating-point calling convention, or none to indicate | |
7f999549 JW |
67 | the soft-float calling convention. Also, "ilp32" can optionally be followed |
68 | by "e" to indicate the RVE ABI, which is always soft-float. | |
e23eba97 | 69 | |
71060565 JW |
70 | @cindex @samp{-mrelax} option, RISC-V |
71 | @item -mrelax | |
72 | Take advantage of linker relaxations to reduce the number of instructions | |
73 | required to materialize symbol addresses. (default) | |
74 | ||
75 | @cindex @samp{-mno-relax} option, RISC-V | |
76 | @item -mno-relax | |
77 | Don't do linker relaxations. | |
78 | ||
bd3380bc NC |
79 | @cindex @samp{-march-attr} option, RISC-V |
80 | @item -march-attr | |
81 | Generate the default contents for the riscv elf attribute section if the | |
82 | .attribute directives are not set. This section is used to record the | |
83 | information that a linker or runtime loader needs to check compatibility. | |
84 | This information includes ISA string, stack alignment requirement, unaligned | |
85 | memory accesses, and the major, minor and revision version of privileged | |
86 | specification. | |
87 | ||
88 | @cindex @samp{-mno-arch-attr} option, RISC-V | |
89 | @item -mno-arch-attr | |
90 | Don't generate the default riscv elf attribute section if the .attribute | |
91 | directives are not set. | |
92 | ||
2ca89224 NC |
93 | @cindex @samp{-mcsr-check} option, RISC-V |
94 | @item -mcsr-check | |
95 | Enable the CSR checking for the ISA-dependent CRS and the read-only CSR. | |
96 | The ISA-dependent CSR are only valid when the specific ISA is set. The | |
97 | read-only CSR can not be written by the CSR instructions. | |
98 | ||
99 | @cindex @samp{-mno-csr-check} option, RISC-V | |
100 | @item -mno-csr-check | |
369afd50 | 101 | Don't do CSR checking. |
286d2f2c MC |
102 | |
103 | @cindex @samp{-mlittle-endian} option, RISC-V | |
104 | @item -mlittle-endian | |
105 | Generate code for a little endian machine. | |
106 | ||
107 | @cindex @samp{-mbig-endian} option, RISC-V | |
108 | @item -mbig-endian | |
109 | Generate code for a big endian machine. | |
e23eba97 NC |
110 | @end table |
111 | @c man end | |
b57e49f7 JW |
112 | |
113 | @node RISC-V-Directives | |
fed44c60 | 114 | @section RISC-V Directives |
b57e49f7 JW |
115 | @cindex machine directives, RISC-V |
116 | @cindex RISC-V machine directives | |
117 | ||
b57e49f7 JW |
118 | The following table lists all available RISC-V specific directives. |
119 | ||
120 | @table @code | |
121 | ||
122 | @cindex @code{align} directive | |
123 | @item .align @var{size-log-2} | |
124 | Align to the given boundary, with the size given as log2 the number of bytes to | |
125 | align to. | |
126 | ||
127 | @cindex Data directives | |
128 | @item .half @var{value} | |
129 | @itemx .word @var{value} | |
130 | @itemx .dword @var{value} | |
131 | Emits a half-word, word, or double-word value at the current position. | |
132 | ||
133 | @cindex DTP-relative data directives | |
134 | @item .dtprelword @var{value} | |
135 | @itemx .dtpreldword @var{value} | |
136 | Emits a DTP-relative word (or double-word) at the current position. This is | |
137 | meant to be used by the compiler in shared libraries for DWARF debug info for | |
138 | thread local variables. | |
139 | ||
140 | @cindex BSS directive | |
141 | @item .bss | |
142 | Sets the current section to the BSS section. | |
143 | ||
144 | @cindex LEB128 directives | |
145 | @item .uleb128 @var{value} | |
146 | @itemx .sleb128 @var{value} | |
147 | Emits a signed or unsigned LEB128 value at the current position. This only | |
148 | accepts constant expressions, because symbol addresses can change with | |
149 | relaxation, and we don't support relocations to modify LEB128 values at link | |
150 | time. | |
151 | ||
152 | @cindex Option directive | |
153 | @cindex @code{option} directive | |
154 | @item .option @var{argument} | |
155 | Modifies RISC-V specific assembler options inline with the assembly code. | |
156 | This is used when particular instruction sequences must be assembled with a | |
157 | specific set of options. For example, since we relax addressing sequences to | |
158 | shorter GP-relative sequences when possible the initial load of GP must not be | |
159 | relaxed and should be emitted as something like | |
160 | ||
161 | @smallexample | |
162 | .option push | |
163 | .option norelax | |
164 | la gp, __global_pointer$ | |
165 | .option pop | |
166 | @end smallexample | |
167 | ||
168 | in order to produce after linker relaxation the expected | |
169 | ||
170 | @smallexample | |
171 | auipc gp, %pcrel_hi(__global_pointer$) | |
172 | addi gp, gp, %pcrel_lo(__global_pointer$) | |
173 | @end smallexample | |
174 | ||
175 | instead of just | |
176 | ||
177 | @smallexample | |
178 | addi gp, gp, 0 | |
179 | @end smallexample | |
180 | ||
181 | It's not expected that options are changed in this manner during regular use, | |
182 | but there are a handful of esoteric cases like the one above where users need | |
183 | to disable particular features of the assembler for particular code sequences. | |
184 | The complete list of option arguments is shown below: | |
185 | ||
186 | @table @code | |
187 | @item push | |
188 | @itemx pop | |
189 | Pushes or pops the current option stack. These should be used whenever | |
190 | changing an option in line with assembly code in order to ensure the user's | |
191 | command-line options are respected for the bulk of the file being assembled. | |
192 | ||
193 | @item rvc | |
194 | @itemx norvc | |
195 | Enables or disables the generation of compressed instructions. Instructions | |
196 | are opportunistically compressed by the RISC-V assembler when possible, but | |
d3ffd7f7 | 197 | sometimes this behavior is not desirable, especially when handling alignments. |
b57e49f7 JW |
198 | |
199 | @item pic | |
200 | @itemx nopic | |
201 | Enables or disables position-independent code generation. Unless you really | |
202 | know what you're doing, this should only be at the top of a file. | |
203 | ||
204 | @item relax | |
205 | @itemx norelax | |
206 | Enables or disables relaxation. The RISC-V assembler and linker | |
207 | opportunistically relax some code sequences, but sometimes this behavior is not | |
208 | desirable. | |
209 | @end table | |
210 | ||
2ca89224 NC |
211 | @item csr-check |
212 | @itemx no-csr-check | |
213 | Enables or disables the CSR checking. | |
214 | ||
d3ffd7f7 NC |
215 | @item arch, @var{+extension[version]} [,...,@var{+extension_n[version_n]}] |
216 | @itemx arch, @var{-extension} [,...,@var{-extension_n}] | |
217 | @itemx arch, @var{=ISA} | |
218 | Enables or disables the extensions for specific code region. For example, | |
219 | @samp{.option arch, +m2p0} means add m extension with version 2.0, and | |
220 | @samp{.option arch, -f, -d} means remove extensions, f and d, from the | |
221 | architecture string. Note that, @samp{.option arch, +c, -c} have the same | |
222 | behavior as @samp{.option rvc, norvc}. However, they are also undesirable | |
223 | sometimes. Besides, @samp{.option arch, -i} is illegal, since we cannot | |
224 | remove the base i extension anytime. If you want to reset the whole ISA | |
225 | string, you can also use @samp{.option arch, =rv32imac} to overwrite the | |
226 | previous settings. | |
227 | ||
0e35537d | 228 | @cindex INSN directives |
a262b82f NC |
229 | @item .insn @var{type}, @var{operand} [,...,@var{operand_n}] |
230 | @itemx .insn @var{insn_length}, @var{value} | |
0e35537d JW |
231 | @itemx .insn @var{value} |
232 | This directive permits the numeric representation of an instructions | |
233 | and makes the assembler insert the operands according to one of the | |
234 | instruction formats for @samp{.insn} (@ref{RISC-V-Formats}). | |
235 | For example, the instruction @samp{add a0, a1, a2} could be written as | |
a262b82f NC |
236 | @samp{.insn r 0x33, 0, 0, a0, a1, a2}. But in fact, the instruction |
237 | formats are difficult to use for some users, so most of them are using | |
238 | @samp{.word} to encode the instruction directly, rather than using | |
239 | @samp{.insn}. It is fine for now, but will be wrong when the mapping | |
240 | symbols are supported, since @samp{.word} will not be shown as an | |
241 | instruction, it should be shown as data. Therefore, we also support | |
242 | two more formats of the @samp{.insn}, the instruction @samp{add a0, a1, a2} | |
243 | could also be written as @samp{.insn 0x4, 0xc58533} or @samp{.insn 0xc58533}. | |
244 | When the @var{insn_length} is set, then assembler will check if the | |
245 | @var{value} is a valid @var{insn_length} bytes instruction. | |
0e35537d | 246 | |
2dc8dd17 JW |
247 | @cindex @code{.attribute} directive, RISC-V |
248 | @item .attribute @var{tag}, @var{value} | |
249 | Set the object attribute @var{tag} to @var{value}. | |
250 | ||
251 | The @var{tag} is either an attribute number, or one of the following: | |
252 | @code{Tag_RISCV_arch}, @code{Tag_RISCV_stack_align}, | |
253 | @code{Tag_RISCV_unaligned_access}, @code{Tag_RISCV_priv_spec}, | |
254 | @code{Tag_RISCV_priv_spec_minor}, @code{Tag_RISCV_priv_spec_revision}. | |
255 | ||
b57e49f7 | 256 | @end table |
0e35537d | 257 | |
de48783e NC |
258 | @node RISC-V-Modifiers |
259 | @section RISC-V Assembler Modifiers | |
260 | ||
261 | The RISC-V assembler supports following modifiers for relocatable addresses | |
262 | used in RISC-V instruction operands. However, we also support some pseudo | |
263 | instructions that are easier to use than these modifiers. | |
264 | ||
265 | @table @code | |
266 | @item %lo(@var{symbol}) | |
267 | The low 12 bits of absolute address for @var{symbol}. | |
268 | ||
269 | @item %hi(@var{symbol}) | |
270 | The high 20 bits of absolute address for @var{symbol}. This is usually | |
271 | used with the %lo modifier to represent a 32-bit absolute address. | |
272 | ||
273 | @smallexample | |
274 | lui a0, %hi(@var{symbol}) // R_RISCV_HI20 | |
275 | addi a0, a0, %lo(@var{symbol}) // R_RISCV_LO12_I | |
276 | ||
277 | lui a0, %hi(@var{symbol}) // R_RISCV_HI20 | |
278 | load/store a0, %lo(@var{symbol})(a0) // R_RISCV_LO12_I/S | |
279 | @end smallexample | |
280 | ||
281 | @item %pcrel_lo(@var{label}) | |
282 | The low 12 bits of relative address between pc and @var{symbol}. | |
283 | The @var{symbol} is related to the high part instruction which is marked | |
284 | by @var{label}. | |
285 | ||
286 | @item %pcrel_hi(@var{symbol}) | |
287 | The high 20 bits of relative address between pc and @var{symbol}. | |
288 | This is usually used with the %pcrel_lo modifier to represent a +/-2GB | |
289 | pc-relative range. | |
290 | ||
291 | @smallexample | |
292 | @var{label}: | |
293 | auipc a0, %pcrel_hi(@var{symbol}) // R_RISCV_PCREL_HI20 | |
294 | addi a0, a0, %pcrel_lo(@var{label}) // R_RISCV_PCREL_LO12_I | |
295 | ||
296 | @var{label}: | |
297 | auipc a0, %pcrel_hi(@var{symbol}) // R_RISCV_PCREL_HI20 | |
298 | load/store a0, %pcrel_lo(@var{label})(a0) // R_RISCV_PCREL_LO12_I/S | |
299 | @end smallexample | |
300 | ||
301 | Or you can use the pseudo lla/lw/sw/... instruction to do this. | |
302 | ||
303 | @smallexample | |
304 | lla a0, @var{symbol} | |
305 | @end smallexample | |
306 | ||
dee35d02 NC |
307 | @item %got_pcrel_hi(@var{symbol}) |
308 | The high 20 bits of relative address between pc and the GOT entry of | |
309 | @var{symbol}. This is usually used with the %pcrel_lo modifier to access | |
310 | the GOT entry. | |
311 | ||
312 | @smallexample | |
313 | @var{label}: | |
314 | auipc a0, %got_pcrel_hi(@var{symbol}) // R_RISCV_GOT_HI20 | |
315 | addi a0, a0, %pcrel_lo(@var{label}) // R_RISCV_PCREL_LO12_I | |
316 | ||
317 | @var{label}: | |
318 | auipc a0, %got_pcrel_hi(@var{symbol}) // R_RISCV_GOT_HI20 | |
319 | load/store a0, %pcrel_lo(@var{label})(a0) // R_RISCV_PCREL_LO12_I/S | |
320 | @end smallexample | |
321 | ||
322 | Also, the pseudo la instruction with PIC has similar behavior. | |
323 | ||
de48783e NC |
324 | @item %tprel_add(@var{symbol}) |
325 | This is used purely to associate the R_RISCV_TPREL_ADD relocation for | |
326 | TLS relaxation. This one is only valid as the fourth operand to the normally | |
327 | 3 operand add instruction. | |
328 | ||
329 | @item %tprel_lo(@var{symbol}) | |
330 | The low 12 bits of relative address between tp and @var{symbol}. | |
331 | ||
332 | @item %tprel_hi(@var{symbol}) | |
333 | The high 20 bits of relative address between tp and @var{symbol}. This is | |
334 | usually used with the %tprel_lo and %tprel_add modifiers to access the thread | |
335 | local variable @var{symbol} in TLS Local Exec. | |
336 | ||
337 | @smallexample | |
338 | lui a5, %tprel_hi(@var{symbol}) // R_RISCV_TPREL_HI20 | |
339 | add a5, a5, tp, %tprel_add(@var{symbol}) // R_RISCV_TPREL_ADD | |
340 | load/store t0, %tprel_lo(@var{symbol})(a5) // R_RISCV_TPREL_LO12_I/S | |
341 | @end smallexample | |
342 | ||
343 | @item %tls_ie_pcrel_hi(@var{symbol}) | |
344 | The high 20 bits of relative address between pc and GOT entry. It is | |
345 | usually used with the %pcrel_lo modifier to access the thread local | |
346 | variable @var{symbol} in TLS Initial Exec. | |
347 | ||
348 | @smallexample | |
349 | la.tls.ie a5, @var{symbol} | |
350 | add a5, a5, tp | |
351 | load/store t0, 0(a5) | |
352 | @end smallexample | |
353 | ||
354 | The pseudo la.tls.ie instruction can be expended to | |
355 | ||
356 | @smallexample | |
357 | @var{label}: | |
358 | auipc a5, %tls_ie_pcrel_hi(@var{symbol}) // R_RISCV_TLS_GOT_HI20 | |
359 | load a5, %pcrel_lo(@var{label})(a5) // R_RISCV_PCREL_LO12_I | |
360 | @end smallexample | |
361 | ||
362 | @item %tls_gd_pcrel_hi(@var{symbol}) | |
363 | The high 20 bits of relative address between pc and GOT entry. It is | |
364 | usually used with the %pcrel_lo modifier to access the thread local variable | |
365 | @var{symbol} in TLS Global Dynamic. | |
366 | ||
367 | @smallexample | |
368 | la.tls.gd a0, @var{symbol} | |
369 | call __tls_get_addr@@plt | |
370 | mv a5, a0 | |
371 | load/store t0, 0(a5) | |
372 | @end smallexample | |
373 | ||
374 | The pseudo la.tls.gd instruction can be expended to | |
375 | ||
376 | @smallexample | |
377 | @var{label}: | |
378 | auipc a0, %tls_gd_pcrel_hi(@var{symbol}) // R_RISCV_TLS_GD_HI20 | |
379 | addi a0, a0, %pcrel_lo(@var{label}) // R_RISCV_PCREL_LO12_I | |
380 | @end smallexample | |
381 | ||
382 | @end table | |
383 | ||
0e35537d | 384 | @node RISC-V-Formats |
de48783e | 385 | @section RISC-V Instruction Formats |
0e35537d JW |
386 | @cindex instruction formats, risc-v |
387 | @cindex RISC-V instruction formats | |
388 | ||
5a9f5403 | 389 | The RISC-V Instruction Set Manual Volume I: User-Level ISA lists 15 |
0e35537d JW |
390 | instruction formats where some of the formats have multiple variants. |
391 | For the @samp{.insn} pseudo directive the assembler recognizes some | |
392 | of the formats. | |
393 | Typically, the most general variant of the instruction format is used | |
394 | by the @samp{.insn} directive. | |
395 | ||
396 | The following table lists the abbreviations used in the table of | |
397 | instruction formats: | |
398 | ||
399 | @display | |
400 | @multitable @columnfractions .15 .40 | |
401 | @item opcode @tab Unsigned immediate or opcode name for 7-bits opcode. | |
402 | @item opcode2 @tab Unsigned immediate or opcode name for 2-bits opcode. | |
403 | @item func7 @tab Unsigned immediate for 7-bits function code. | |
4765cd61 | 404 | @item func6 @tab Unsigned immediate for 6-bits function code. |
0e35537d JW |
405 | @item func4 @tab Unsigned immediate for 4-bits function code. |
406 | @item func3 @tab Unsigned immediate for 3-bits function code. | |
407 | @item func2 @tab Unsigned immediate for 2-bits function code. | |
408 | @item rd @tab Destination register number for operand x, can be GPR or FPR. | |
409 | @item rd' @tab Destination register number for operand x, | |
410 | only accept s0-s1, a0-a5, fs0-fs1 and fa0-fa5. | |
411 | @item rs1 @tab First source register number for operand x, can be GPR or FPR. | |
412 | @item rs1' @tab First source register number for operand x, | |
413 | only accept s0-s1, a0-a5, fs0-fs1 and fa0-fa5. | |
414 | @item rs2 @tab Second source register number for operand x, can be GPR or FPR. | |
415 | @item rs2' @tab Second source register number for operand x, | |
416 | only accept s0-s1, a0-a5, fs0-fs1 and fa0-fa5. | |
417 | @item simm12 @tab Sign-extended 12-bit immediate for operand x. | |
418 | @item simm20 @tab Sign-extended 20-bit immediate for operand x. | |
419 | @item simm6 @tab Sign-extended 6-bit immediate for operand x. | |
5a9f5403 NC |
420 | @item uimm5 @tab Unsigned 5-bit immediate for operand x. |
421 | @item uimm6 @tab Unsigned 6-bit immediate for operand x. | |
0e35537d JW |
422 | @item uimm8 @tab Unsigned 8-bit immediate for operand x. |
423 | @item symbol @tab Symbol or lable reference for operand x. | |
424 | @end multitable | |
425 | @end display | |
426 | ||
427 | The following table lists all available opcode name: | |
428 | ||
429 | @table @code | |
430 | @item C0 | |
431 | @item C1 | |
432 | @item C2 | |
433 | Opcode space for compressed instructions. | |
434 | ||
435 | @item LOAD | |
436 | Opcode space for load instructions. | |
437 | ||
438 | @item LOAD_FP | |
439 | Opcode space for floating-point load instructions. | |
440 | ||
441 | @item STORE | |
442 | Opcode space for store instructions. | |
443 | ||
444 | @item STORE_FP | |
445 | Opcode space for floating-point store instructions. | |
446 | ||
447 | @item AUIPC | |
448 | Opcode space for auipc instruction. | |
449 | ||
450 | @item LUI | |
451 | Opcode space for lui instruction. | |
452 | ||
453 | @item BRANCH | |
454 | Opcode space for branch instructions. | |
455 | ||
456 | @item JAL | |
457 | Opcode space for jal instruction. | |
458 | ||
459 | @item JALR | |
460 | Opcode space for jalr instruction. | |
461 | ||
462 | @item OP | |
463 | Opcode space for ALU instructions. | |
464 | ||
465 | @item OP_32 | |
466 | Opcode space for 32-bits ALU instructions. | |
467 | ||
468 | @item OP_IMM | |
469 | Opcode space for ALU with immediate instructions. | |
470 | ||
471 | @item OP_IMM_32 | |
472 | Opcode space for 32-bits ALU with immediate instructions. | |
473 | ||
474 | @item OP_FP | |
475 | Opcode space for floating-point operation instructions. | |
476 | ||
477 | @item MADD | |
478 | Opcode space for madd instruction. | |
479 | ||
480 | @item MSUB | |
481 | Opcode space for msub instruction. | |
482 | ||
483 | @item NMADD | |
484 | Opcode space for nmadd instruction. | |
485 | ||
486 | @item NMSUB | |
487 | Opcode space for msub instruction. | |
488 | ||
489 | @item AMO | |
490 | Opcode space for atomic memory operation instructions. | |
491 | ||
98602811 | 492 | @item MISC_MEM |
0e35537d JW |
493 | Opcode space for misc instructions. |
494 | ||
495 | @item SYSTEM | |
496 | Opcode space for system instructions. | |
497 | ||
498 | @item CUSTOM_0 | |
499 | @item CUSTOM_1 | |
500 | @item CUSTOM_2 | |
501 | @item CUSTOM_3 | |
502 | Opcode space for customize instructions. | |
503 | ||
504 | @end table | |
505 | ||
506 | An instruction is two or four bytes in length and must be aligned | |
507 | on a 2 byte boundary. The first two bits of the instruction specify the | |
508 | length of the instruction, 00, 01 and 10 indicates a two byte instruction, | |
509 | 11 indicates a four byte instruction. | |
510 | ||
511 | The following table lists the RISC-V instruction formats that are available | |
512 | with the @samp{.insn} pseudo directive: | |
513 | ||
514 | @table @code | |
5a9f5403 | 515 | @item R type: .insn r opcode6, func3, func7, rd, rs1, rs2 |
0e35537d | 516 | @verbatim |
5a9f5403 NC |
517 | +-------+-----+-----+-------+----+---------+ |
518 | | func7 | rs2 | rs1 | func3 | rd | opcode6 | | |
519 | +-------+-----+-----+-------+----+---------+ | |
520 | 31 25 20 15 12 7 0 | |
0e35537d JW |
521 | @end verbatim |
522 | ||
5a9f5403 NC |
523 | @item R type with 4 register operands: .insn r opcode6, func3, func2, rd, rs1, rs2, rs3 |
524 | @itemx R4 type: .insn r4 opcode6, func3, func2, rd, rs1, rs2, rs3 | |
0e35537d | 525 | @verbatim |
5a9f5403 NC |
526 | +-----+-------+-----+-----+-------+----+---------+ |
527 | | rs3 | func2 | rs2 | rs1 | func3 | rd | opcode6 | | |
528 | +-----+-------+-----+-----+-------+----+---------+ | |
529 | 31 27 25 20 15 12 7 0 | |
0e35537d JW |
530 | @end verbatim |
531 | ||
5a9f5403 NC |
532 | @item I type: .insn i opcode6, func3, rd, rs1, simm12 |
533 | @itemx I type: .insn i opcode6, func3, rd, simm12(rs1) | |
0e35537d | 534 | @verbatim |
5a9f5403 NC |
535 | +--------------+-----+-------+----+---------+ |
536 | | simm12[11:0] | rs1 | func3 | rd | opcode6 | | |
537 | +--------------+-----+-------+----+---------+ | |
538 | 31 20 15 12 7 0 | |
0e35537d JW |
539 | @end verbatim |
540 | ||
5a9f5403 | 541 | @item S type: .insn s opcode6, func3, rs2, simm12(rs1) |
0e35537d | 542 | @verbatim |
5a9f5403 NC |
543 | +--------------+-----+-----+-------+-------------+---------+ |
544 | | simm12[11:5] | rs2 | rs1 | func3 | simm12[4:0] | opcode6 | | |
545 | +--------------+-----+-----+-------+-------------+---------+ | |
546 | 31 25 20 15 12 7 0 | |
0e35537d JW |
547 | @end verbatim |
548 | ||
5a9f5403 NC |
549 | @item B type: .insn s opcode6, func3, rs1, rs2, symbol |
550 | @itemx SB type: .insn sb opcode6, func3, rs1, rs2, symbol | |
0e35537d | 551 | @verbatim |
5a9f5403 NC |
552 | +-----------------+-----+-----+-------+----------------+---------+ |
553 | | simm12[12|10:5] | rs2 | rs1 | func3 | simm12[4:1|11] | opcode6 | | |
554 | +-----------------+-----+-----+-------+----------------+---------+ | |
555 | 31 25 20 15 12 7 0 | |
0e35537d JW |
556 | @end verbatim |
557 | ||
5a9f5403 | 558 | @item U type: .insn u opcode6, rd, simm20 |
0e35537d | 559 | @verbatim |
5a9f5403 NC |
560 | +--------------------------+----+---------+ |
561 | | simm20[20|10:1|11|19:12] | rd | opcode6 | | |
562 | +--------------------------+----+---------+ | |
563 | 31 12 7 0 | |
0e35537d JW |
564 | @end verbatim |
565 | ||
5a9f5403 NC |
566 | @item J type: .insn j opcode6, rd, symbol |
567 | @itemx UJ type: .insn uj opcode6, rd, symbol | |
0e35537d | 568 | @verbatim |
5a9f5403 NC |
569 | +------------+--------------+------------+---------------+----+---------+ |
570 | | simm20[20] | simm20[10:1] | simm20[11] | simm20[19:12] | rd | opcode6 | | |
571 | +------------+--------------+------------+---------------+----+---------+ | |
572 | 31 30 21 20 12 7 0 | |
0e35537d JW |
573 | @end verbatim |
574 | ||
4765cd61 | 575 | @item CR type: .insn cr opcode2, func4, rd, rs2 |
0e35537d | 576 | @verbatim |
5a9f5403 NC |
577 | +-------+--------+-----+---------+ |
578 | | func4 | rd/rs1 | rs2 | opcode2 | | |
579 | +-------+--------+-----+---------+ | |
580 | 15 12 7 2 0 | |
0e35537d JW |
581 | @end verbatim |
582 | ||
583 | @item CI type: .insn ci opcode2, func3, rd, simm6 | |
584 | @verbatim | |
5a9f5403 NC |
585 | +-------+----------+--------+------------+---------+ |
586 | | func3 | simm6[5] | rd/rs1 | simm6[4:0] | opcode2 | | |
587 | +-------+----------+--------+------------+---------+ | |
588 | 15 13 12 7 2 0 | |
0e35537d JW |
589 | @end verbatim |
590 | ||
5a9f5403 | 591 | @item CIW type: .insn ciw opcode2, func3, rd', uimm8 |
0e35537d | 592 | @verbatim |
5a9f5403 NC |
593 | +-------+------------+-----+---------+ |
594 | | func3 | uimm8[7:0] | rd' | opcode2 | | |
595 | +-------+-------- ---+-----+---------+ | |
596 | 15 13 5 2 0 | |
0e35537d JW |
597 | @end verbatim |
598 | ||
5a9f5403 | 599 | @item CSS type: .insn css opcode2, func3, rd, uimm6 |
4765cd61 | 600 | @verbatim |
5a9f5403 NC |
601 | +-------+------------+----+---------+ |
602 | | func3 | uimm6[5:0] | rd | opcode2 | | |
603 | +-------+------------+----+---------+ | |
604 | 15 13 7 2 0 | |
4765cd61 JW |
605 | @end verbatim |
606 | ||
5a9f5403 | 607 | @item CL type: .insn cl opcode2, func3, rd', uimm5(rs1') |
0e35537d | 608 | @verbatim |
5a9f5403 NC |
609 | +-------+------------+------+------------+------+---------+ |
610 | | func3 | uimm5[4:2] | rs1' | uimm5[1:0] | rd' | opcode2 | | |
611 | +-------+------------+------+------------+------+---------+ | |
612 | 15 13 10 7 5 2 0 | |
613 | @end verbatim | |
614 | ||
615 | @item CS type: .insn cs opcode2, func3, rs2', uimm5(rs1') | |
616 | @verbatim | |
617 | +-------+------------+------+------------+------+---------+ | |
618 | | func3 | uimm5[4:2] | rs1' | uimm5[1:0] | rs2' | opcode2 | | |
619 | +-------+------------+------+------------+------+---------+ | |
620 | 15 13 10 7 5 2 0 | |
621 | @end verbatim | |
622 | ||
623 | @item CA type: .insn ca opcode2, func6, func2, rd', rs2' | |
624 | @verbatim | |
625 | +-- ----+----------+-------+------+---------+ | |
626 | | func6 | rd'/rs1' | func2 | rs2' | opcode2 | | |
627 | +-------+----------+-------+------+---------+ | |
628 | 15 10 7 5 2 0 | |
629 | @end verbatim | |
630 | ||
631 | @item CB type: .insn cb opcode2, func3, rs1', symbol | |
632 | @verbatim | |
633 | +-------+--------------+------+------------------+---------+ | |
634 | | func3 | simm8[8|4:3] | rs1' | simm8[7:6|2:1|5] | opcode2 | | |
635 | +-------+--------------+------+------------------+---------+ | |
636 | 15 13 10 7 2 0 | |
0e35537d JW |
637 | @end verbatim |
638 | ||
639 | @item CJ type: .insn cj opcode2, symbol | |
640 | @verbatim | |
5a9f5403 NC |
641 | +-------+-------------------------------+---------+ |
642 | | func3 | simm11[11|4|9:8|10|6|7|3:1|5] | opcode2 | | |
643 | +-------+-------------------------------+---------+ | |
644 | 15 13 2 0 | |
0e35537d JW |
645 | @end verbatim |
646 | ||
647 | ||
648 | @end table | |
649 | ||
650 | For the complete list of all instruction format variants see | |
651 | The RISC-V Instruction Set Manual Volume I: User-Level ISA. | |
2dc8dd17 JW |
652 | |
653 | @node RISC-V-ATTRIBUTE | |
654 | @section RISC-V Object Attribute | |
655 | @cindex Object Attribute, RISC-V | |
656 | ||
657 | RISC-V attributes have a string value if the tag number is odd and an integer | |
658 | value if the tag number is even. | |
659 | ||
660 | @table @r | |
661 | @item Tag_RISCV_stack_align (4) | |
662 | Tag_RISCV_strict_align records the N-byte stack alignment for this object. The | |
663 | default value is 16 for RV32I or RV64I, and 4 for RV32E. | |
664 | ||
665 | The smallest value will be used if object files with different | |
666 | Tag_RISCV_stack_align values are merged. | |
667 | ||
668 | @item Tag_RISCV_arch (5) | |
669 | Tag_RISCV_arch contains a string for the target architecture taken from the | |
670 | option @option{-march}. Different architectures will be integrated into a | |
671 | superset when object files are merged. | |
672 | ||
673 | Note that the version information of the target architecture must be presented | |
674 | explicitly in the attribute and abbreviations must be expanded. The version | |
675 | information, if not given by @option{-march}, must be in accordance with the | |
676 | default specified by the tool. For example, the architecture @code{RV32I} has | |
677 | to be recorded in the attribute as @code{RV32I2P0} in which @code{2P0} stands | |
678 | for the default version of its base ISA. On the other hand, the architecture | |
679 | @code{RV32G} has to be presented as @code{RV32I2P0_M2P0_A2P0_F2P0_D2P0} in | |
680 | which the abbreviation @code{G} is expanded to the @code{IMAFD} combination | |
681 | with default versions of the standard extensions. | |
682 | ||
683 | @item Tag_RISCV_unaligned_access (6) | |
684 | Tag_RISCV_unaligned_access is 0 for files that do not allow any unaligned | |
685 | memory accesses, and 1 for files that do allow unaligned memory accesses. | |
686 | ||
687 | @item Tag_RISCV_priv_spec (8) | |
688 | @item Tag_RISCV_priv_spec_minor (10) | |
689 | @item Tag_RISCV_priv_spec_revision (12) | |
690 | Tag_RISCV_priv_spec contains the major/minor/revision version information of | |
691 | the privileged specification. It will report errors if object files of | |
692 | different privileged specification versions are merged. | |
693 | ||
694 | @end table |