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7c31ae13 | 1 | @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 2002, 2006, 2011 |
f7e42eb4 | 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 | @ifset GENERIC | |
6 | @page | |
7 | @node i960-Dependent | |
8 | @chapter Intel 80960 Dependent Features | |
9 | @end ifset | |
10 | @ifclear GENERIC | |
11 | @node Machine Dependencies | |
12 | @chapter Intel 80960 Dependent Features | |
13 | @end ifclear | |
14 | ||
15 | @cindex i960 support | |
16 | @menu | |
17 | * Options-i960:: i960 Command-line Options | |
18 | * Floating Point-i960:: Floating Point | |
19 | * Directives-i960:: i960 Machine Directives | |
20 | * Opcodes for i960:: i960 Opcodes | |
7c31ae13 | 21 | * Syntax of i960:: i960 Syntax |
252b5132 RH |
22 | @end menu |
23 | ||
24 | @c FIXME! Add Syntax sec with discussion of bitfields here, at least so | |
25 | @c long as they're not turned on for other machines than 960. | |
26 | ||
27 | @node Options-i960 | |
28 | ||
29 | @section i960 Command-line Options | |
30 | ||
31 | @cindex i960 options | |
32 | @cindex options, i960 | |
33 | @table @code | |
34 | ||
35 | @cindex i960 architecture options | |
36 | @cindex architecture options, i960 | |
37 | @cindex @code{-A} options, i960 | |
38 | @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC | |
39 | Select the 80960 architecture. Instructions or features not supported | |
40 | by the selected architecture cause fatal errors. | |
41 | ||
42 | @samp{-ACA} is equivalent to @samp{-ACA_A}; @samp{-AKC} is equivalent to | |
43 | @samp{-AMC}. Synonyms are provided for compatibility with other tools. | |
44 | ||
45 | If you do not specify any of these options, @code{@value{AS}} generates code | |
46 | for any instruction or feature that is supported by @emph{some} version of the | |
47 | 960 (even if this means mixing architectures!). In principle, | |
48 | @code{@value{AS}} attempts to deduce the minimal sufficient processor type if | |
49 | none is specified; depending on the object code format, the processor type may | |
50 | be recorded in the object file. If it is critical that the @code{@value{AS}} | |
51 | output match a specific architecture, specify that architecture explicitly. | |
52 | ||
53 | @cindex @code{-b} option, i960 | |
54 | @cindex branch recording, i960 | |
55 | @cindex i960 branch recording | |
56 | @item -b | |
57 | Add code to collect information about conditional branches taken, for | |
58 | later optimization using branch prediction bits. (The conditional branch | |
59 | instructions have branch prediction bits in the CA, CB, and CC | |
60 | architectures.) If @var{BR} represents a conditional branch instruction, | |
61 | the following represents the code generated by the assembler when | |
62 | @samp{-b} is specified: | |
63 | ||
64 | @smallexample | |
65 | call @var{increment routine} | |
66 | .word 0 # pre-counter | |
67 | Label: @var{BR} | |
68 | call @var{increment routine} | |
69 | .word 0 # post-counter | |
70 | @end smallexample | |
71 | ||
72 | The counter following a branch records the number of times that branch | |
b45619c0 | 73 | was @emph{not} taken; the difference between the two counters is the |
252b5132 RH |
74 | number of times the branch @emph{was} taken. |
75 | ||
76 | @cindex @code{gbr960}, i960 postprocessor | |
77 | @cindex branch statistics table, i960 | |
78 | A table of every such @code{Label} is also generated, so that the | |
79 | external postprocessor @code{gbr960} (supplied by Intel) can locate all | |
062b7c0c | 80 | the counters. This table is always labeled @samp{__BRANCH_TABLE__}; |
252b5132 RH |
81 | this is a local symbol to permit collecting statistics for many separate |
82 | object files. The table is word aligned, and begins with a two-word | |
83 | header. The first word, initialized to 0, is used in maintaining linked | |
84 | lists of branch tables. The second word is a count of the number of | |
85 | entries in the table, which follow immediately: each is a word, pointing | |
86 | to one of the labels illustrated above. | |
87 | ||
88 | @c TEXI2ROFF-KILL | |
89 | @ifinfo | |
90 | @c END TEXI2ROFF-KILL | |
91 | @example | |
92 | +------------+------------+------------+ ... +------------+ | |
93 | | | | | | | | |
94 | | *NEXT | COUNT: N | *BRLAB 1 | | *BRLAB N | | |
95 | | | | | | | | |
96 | +------------+------------+------------+ ... +------------+ | |
97 | ||
98 | __BRANCH_TABLE__ layout | |
99 | @end example | |
100 | @c TEXI2ROFF-KILL | |
101 | @end ifinfo | |
102 | @need 2000 | |
103 | @tex | |
104 | \vskip 1pc | |
105 | \line{\leftskip=0pt\hskip\tableindent | |
106 | \boxit{2cm}{\tt *NEXT}\boxit{2cm}{\tt COUNT: \it N}\boxit{2cm}{\tt | |
107 | *BRLAB 1}\ibox{1cm}{\quad\dots}\boxit{2cm}{\tt *BRLAB \it N}\hfil} | |
108 | \centerline{\it {\tt \_\_BRANCH\_TABLE\_\_} layout} | |
109 | @end tex | |
110 | @c END TEXI2ROFF-KILL | |
111 | ||
112 | The first word of the header is used to locate multiple branch tables, | |
113 | since each object file may contain one. Normally the links are | |
114 | maintained with a call to an initialization routine, placed at the | |
115 | beginning of each function in the file. The @sc{gnu} C compiler | |
116 | generates these calls automatically when you give it a @samp{-b} option. | |
117 | For further details, see the documentation of @samp{gbr960}. | |
118 | ||
119 | @cindex @code{-no-relax} option, i960 | |
120 | @item -no-relax | |
121 | Normally, Compare-and-Branch instructions with targets that require | |
122 | displacements greater than 13 bits (or that have external targets) are | |
123 | replaced with the corresponding compare (or @samp{chkbit}) and branch | |
124 | instructions. You can use the @samp{-no-relax} option to specify that | |
125 | @code{@value{AS}} should generate errors instead, if the target displacement | |
126 | is larger than 13 bits. | |
127 | ||
128 | This option does not affect the Compare-and-Jump instructions; the code | |
129 | emitted for them is @emph{always} adjusted when necessary (depending on | |
130 | displacement size), regardless of whether you use @samp{-no-relax}. | |
131 | @end table | |
132 | ||
133 | @node Floating Point-i960 | |
134 | @section Floating Point | |
135 | ||
136 | @cindex floating point, i960 (@sc{ieee}) | |
137 | @cindex i960 floating point (@sc{ieee}) | |
138 | @code{@value{AS}} generates @sc{ieee} floating-point numbers for the directives | |
139 | @samp{.float}, @samp{.double}, @samp{.extended}, and @samp{.single}. | |
140 | ||
141 | @node Directives-i960 | |
142 | @section i960 Machine Directives | |
143 | ||
144 | @cindex machine directives, i960 | |
145 | @cindex i960 machine directives | |
146 | ||
147 | @table @code | |
148 | @cindex @code{bss} directive, i960 | |
149 | @item .bss @var{symbol}, @var{length}, @var{align} | |
150 | Reserve @var{length} bytes in the bss section for a local @var{symbol}, | |
151 | aligned to the power of two specified by @var{align}. @var{length} and | |
152 | @var{align} must be positive absolute expressions. This directive | |
153 | differs from @samp{.lcomm} only in that it permits you to specify | |
154 | an alignment. @xref{Lcomm,,@code{.lcomm}}. | |
155 | @end table | |
156 | ||
157 | @table @code | |
158 | @cindex @code{extended} directive, i960 | |
159 | @item .extended @var{flonums} | |
160 | @code{.extended} expects zero or more flonums, separated by commas; for | |
161 | each flonum, @samp{.extended} emits an @sc{ieee} extended-format (80-bit) | |
162 | floating-point number. | |
163 | ||
164 | @cindex @code{leafproc} directive, i960 | |
165 | @item .leafproc @var{call-lab}, @var{bal-lab} | |
166 | You can use the @samp{.leafproc} directive in conjunction with the | |
167 | optimized @code{callj} instruction to enable faster calls of leaf | |
168 | procedures. If a procedure is known to call no other procedures, you | |
169 | may define an entry point that skips procedure prolog code (and that does | |
170 | not depend on system-supplied saved context), and declare it as the | |
171 | @var{bal-lab} using @samp{.leafproc}. If the procedure also has an | |
172 | entry point that goes through the normal prolog, you can specify that | |
173 | entry point as @var{call-lab}. | |
174 | ||
175 | A @samp{.leafproc} declaration is meant for use in conjunction with the | |
176 | optimized call instruction @samp{callj}; the directive records the data | |
177 | needed later to choose between converting the @samp{callj} into a | |
178 | @code{bal} or a @code{call}. | |
179 | ||
180 | @var{call-lab} is optional; if only one argument is present, or if the | |
181 | two arguments are identical, the single argument is assumed to be the | |
182 | @code{bal} entry point. | |
183 | ||
184 | @cindex @code{sysproc} directive, i960 | |
185 | @item .sysproc @var{name}, @var{index} | |
186 | The @samp{.sysproc} directive defines a name for a system procedure. | |
187 | After you define it using @samp{.sysproc}, you can use @var{name} to | |
188 | refer to the system procedure identified by @var{index} when calling | |
189 | procedures with the optimized call instruction @samp{callj}. | |
190 | ||
191 | Both arguments are required; @var{index} must be between 0 and 31 | |
192 | (inclusive). | |
193 | @end table | |
194 | ||
195 | @node Opcodes for i960 | |
196 | @section i960 Opcodes | |
197 | ||
198 | @cindex opcodes, i960 | |
199 | @cindex i960 opcodes | |
200 | All Intel 960 machine instructions are supported; | |
201 | @pxref{Options-i960,,i960 Command-line Options} for a discussion of | |
202 | selecting the instruction subset for a particular 960 | |
203 | architecture.@refill | |
204 | ||
205 | Some opcodes are processed beyond simply emitting a single corresponding | |
206 | instruction: @samp{callj}, and Compare-and-Branch or Compare-and-Jump | |
207 | instructions with target displacements larger than 13 bits. | |
208 | ||
209 | @menu | |
210 | * callj-i960:: @code{callj} | |
211 | * Compare-and-branch-i960:: Compare-and-Branch | |
212 | @end menu | |
213 | ||
214 | @node callj-i960 | |
215 | @subsection @code{callj} | |
216 | ||
217 | @cindex @code{callj}, i960 pseudo-opcode | |
218 | @cindex i960 @code{callj} pseudo-opcode | |
219 | You can write @code{callj} to have the assembler or the linker determine | |
220 | the most appropriate form of subroutine call: @samp{call}, | |
221 | @samp{bal}, or @samp{calls}. If the assembly source contains | |
222 | enough information---a @samp{.leafproc} or @samp{.sysproc} directive | |
223 | defining the operand---then @code{@value{AS}} translates the | |
224 | @code{callj}; if not, it simply emits the @code{callj}, leaving it | |
225 | for the linker to resolve. | |
226 | ||
227 | @node Compare-and-branch-i960 | |
228 | @subsection Compare-and-Branch | |
229 | ||
230 | @cindex i960 compare/branch instructions | |
231 | @cindex compare/branch instructions, i960 | |
232 | The 960 architectures provide combined Compare-and-Branch instructions | |
233 | that permit you to store the branch target in the lower 13 bits of the | |
234 | instruction word itself. However, if you specify a branch target far | |
235 | enough away that its address won't fit in 13 bits, the assembler can | |
236 | either issue an error, or convert your Compare-and-Branch instruction | |
237 | into separate instructions to do the compare and the branch. | |
238 | ||
239 | @cindex compare and jump expansions, i960 | |
240 | @cindex i960 compare and jump expansions | |
241 | Whether @code{@value{AS}} gives an error or expands the instruction depends | |
242 | on two choices you can make: whether you use the @samp{-no-relax} option, | |
243 | and whether you use a ``Compare and Branch'' instruction or a ``Compare | |
244 | and Jump'' instruction. The ``Jump'' instructions are @emph{always} | |
245 | expanded if necessary; the ``Branch'' instructions are expanded when | |
246 | necessary @emph{unless} you specify @code{-no-relax}---in which case | |
247 | @code{@value{AS}} gives an error instead. | |
248 | ||
249 | These are the Compare-and-Branch instructions, their ``Jump'' variants, | |
250 | and the instruction pairs they may expand into: | |
251 | ||
252 | @c TEXI2ROFF-KILL | |
253 | @ifinfo | |
254 | @c END TEXI2ROFF-KILL | |
255 | @example | |
256 | Compare and | |
257 | Branch Jump Expanded to | |
258 | ------ ------ ------------ | |
259 | bbc chkbit; bno | |
260 | bbs chkbit; bo | |
261 | cmpibe cmpije cmpi; be | |
262 | cmpibg cmpijg cmpi; bg | |
263 | cmpibge cmpijge cmpi; bge | |
264 | cmpibl cmpijl cmpi; bl | |
265 | cmpible cmpijle cmpi; ble | |
266 | cmpibno cmpijno cmpi; bno | |
267 | cmpibne cmpijne cmpi; bne | |
268 | cmpibo cmpijo cmpi; bo | |
269 | cmpobe cmpoje cmpo; be | |
270 | cmpobg cmpojg cmpo; bg | |
271 | cmpobge cmpojge cmpo; bge | |
272 | cmpobl cmpojl cmpo; bl | |
273 | cmpoble cmpojle cmpo; ble | |
274 | cmpobne cmpojne cmpo; bne | |
275 | @end example | |
276 | @c TEXI2ROFF-KILL | |
277 | @end ifinfo | |
278 | @tex | |
279 | \hskip\tableindent | |
280 | \halign{\hfil {\tt #}\quad&\hfil {\tt #}\qquad&{\tt #}\hfil\cr | |
281 | \omit{\hfil\it Compare and\hfil}\span\omit&\cr | |
282 | {\it Branch}&{\it Jump}&{\it Expanded to}\cr | |
283 | bbc& & chkbit; bno\cr | |
284 | bbs& & chkbit; bo\cr | |
285 | cmpibe& cmpije& cmpi; be\cr | |
286 | cmpibg& cmpijg& cmpi; bg\cr | |
287 | cmpibge& cmpijge& cmpi; bge\cr | |
288 | cmpibl& cmpijl& cmpi; bl\cr | |
289 | cmpible& cmpijle& cmpi; ble\cr | |
290 | cmpibno& cmpijno& cmpi; bno\cr | |
291 | cmpibne& cmpijne& cmpi; bne\cr | |
292 | cmpibo& cmpijo& cmpi; bo\cr | |
293 | cmpobe& cmpoje& cmpo; be\cr | |
294 | cmpobg& cmpojg& cmpo; bg\cr | |
295 | cmpobge& cmpojge& cmpo; bge\cr | |
296 | cmpobl& cmpojl& cmpo; bl\cr | |
297 | cmpoble& cmpojle& cmpo; ble\cr | |
298 | cmpobne& cmpojne& cmpo; bne\cr} | |
299 | @end tex | |
300 | @c END TEXI2ROFF-KILL | |
7c31ae13 NC |
301 | |
302 | @node Syntax of i960 | |
303 | @section Syntax for the i960 | |
304 | @menu | |
305 | * i960-Chars:: Special Characters | |
306 | @end menu | |
307 | ||
308 | @node i960-Chars | |
309 | @subsection Special Characters | |
310 | ||
311 | @cindex line comment character, i960 | |
312 | @cindex i960 line comment character | |
313 | The presence of a @samp{#} on a line indicates the start of a comment | |
314 | that extends to the end of the current line. | |
315 | ||
316 | If a @samp{#} appears as the first character of a line, the whole line | |
317 | is treated as a comment, but in this case the line can also be a | |
318 | logical line number directive (@pxref{Comments}) or a | |
319 | preprocessor control command (@pxref{Preprocessing}). | |
320 | ||
321 | @cindex line separator, i960 | |
322 | @cindex statement separator, i960 | |
323 | @cindex i960 line separator | |
324 | The @samp{;} character can be used to separate statements on the same | |
325 | line. |