1 @c Copyright (C) 1991-2014 Free Software Foundation, Inc. 2 @c This is part of the GAS manual. 3 @c For copying conditions, see the file as.texinfo. 4 @ifset GENERIC 5 @page 6 @node i960-Dependent 7 @chapter Intel 80960 Dependent Features 8 @end ifset 9 @ifclear GENERIC 10 @node Machine Dependencies 11 @chapter Intel 80960 Dependent Features 12 @end ifclear 13 14 @cindex i960 support 15 @menu 16 * Options-i960:: i960 Command-line Options 17 * Floating Point-i960:: Floating Point 18 * Directives-i960:: i960 Machine Directives 19 * Opcodes for i960:: i960 Opcodes 20 * Syntax of i960:: i960 Syntax 21 @end menu 22 23 @c FIXME! Add Syntax sec with discussion of bitfields here, at least so 24 @c long as they're not turned on for other machines than 960. 25 26 @node Options-i960 27 28 @section i960 Command-line Options 29 30 @cindex i960 options 31 @cindex options, i960 32 @table @code 33 34 @cindex i960 architecture options 35 @cindex architecture options, i960 36 @cindex @code{-A} options, i960 37 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC 38 Select the 80960 architecture. Instructions or features not supported 39 by the selected architecture cause fatal errors. 40 41 @samp{-ACA} is equivalent to @samp{-ACA_A}; @samp{-AKC} is equivalent to 42 @samp{-AMC}. Synonyms are provided for compatibility with other tools. 43 44 If you do not specify any of these options, @code{@value{AS}} generates code 45 for any instruction or feature that is supported by @emph{some} version of the 46 960 (even if this means mixing architectures!). In principle, 47 @code{@value{AS}} attempts to deduce the minimal sufficient processor type if 48 none is specified; depending on the object code format, the processor type may 49 be recorded in the object file. If it is critical that the @code{@value{AS}} 50 output match a specific architecture, specify that architecture explicitly. 51 52 @cindex @code{-b} option, i960 53 @cindex branch recording, i960 54 @cindex i960 branch recording 55 @item -b 56 Add code to collect information about conditional branches taken, for 57 later optimization using branch prediction bits. (The conditional branch 58 instructions have branch prediction bits in the CA, CB, and CC 59 architectures.) If @var{BR} represents a conditional branch instruction, 60 the following represents the code generated by the assembler when 61 @samp{-b} is specified: 62 63 @smallexample 64 call @var{increment routine} 65 .word 0 # pre-counter 66 Label: @var{BR} 67 call @var{increment routine} 68 .word 0 # post-counter 69 @end smallexample 70 71 The counter following a branch records the number of times that branch 72 was @emph{not} taken; the difference between the two counters is the 73 number of times the branch @emph{was} taken. 74 75 @cindex @code{gbr960}, i960 postprocessor 76 @cindex branch statistics table, i960 77 A table of every such @code{Label} is also generated, so that the 78 external postprocessor @code{gbr960} (supplied by Intel) can locate all 79 the counters. This table is always labeled @samp{__BRANCH_TABLE__}; 80 this is a local symbol to permit collecting statistics for many separate 81 object files. The table is word aligned, and begins with a two-word 82 header. The first word, initialized to 0, is used in maintaining linked 83 lists of branch tables. The second word is a count of the number of 84 entries in the table, which follow immediately: each is a word, pointing 85 to one of the labels illustrated above. 86 87 @c TEXI2ROFF-KILL 88 @ifinfo 89 @c END TEXI2ROFF-KILL 90 @example 91 +------------+------------+------------+ ... +------------+ 92 | | | | | | 93 | *NEXT | COUNT: N | *BRLAB 1 | | *BRLAB N | 94 | | | | | | 95 +------------+------------+------------+ ... +------------+ 96 97 __BRANCH_TABLE__ layout 98 @end example 99 @c TEXI2ROFF-KILL 100 @end ifinfo 101 @need 2000 102 @tex 103 \vskip 1pc 104 \line{\leftskip=0pt\hskip\tableindent 105 \boxit{2cm}{\tt *NEXT}\boxit{2cm}{\tt COUNT: \it N}\boxit{2cm}{\tt 106 *BRLAB 1}\ibox{1cm}{\quad\dots}\boxit{2cm}{\tt *BRLAB \it N}\hfil} 107 \centerline{\it {\tt \_\_BRANCH\_TABLE\_\_} layout} 108 @end tex 109 @c END TEXI2ROFF-KILL 110 111 The first word of the header is used to locate multiple branch tables, 112 since each object file may contain one. Normally the links are 113 maintained with a call to an initialization routine, placed at the 114 beginning of each function in the file. The @sc{gnu} C compiler 115 generates these calls automatically when you give it a @samp{-b} option. 116 For further details, see the documentation of @samp{gbr960}. 117 118 @cindex @code{-no-relax} option, i960 119 @item -no-relax 120 Normally, Compare-and-Branch instructions with targets that require 121 displacements greater than 13 bits (or that have external targets) are 122 replaced with the corresponding compare (or @samp{chkbit}) and branch 123 instructions. You can use the @samp{-no-relax} option to specify that 124 @code{@value{AS}} should generate errors instead, if the target displacement 125 is larger than 13 bits. 126 127 This option does not affect the Compare-and-Jump instructions; the code 128 emitted for them is @emph{always} adjusted when necessary (depending on 129 displacement size), regardless of whether you use @samp{-no-relax}. 130 @end table 131 132 @node Floating Point-i960 133 @section Floating Point 134 135 @cindex floating point, i960 (@sc{ieee}) 136 @cindex i960 floating point (@sc{ieee}) 137 @code{@value{AS}} generates @sc{ieee} floating-point numbers for the directives 138 @samp{.float}, @samp{.double}, @samp{.extended}, and @samp{.single}. 139 140 @node Directives-i960 141 @section i960 Machine Directives 142 143 @cindex machine directives, i960 144 @cindex i960 machine directives 145 146 @table @code 147 @cindex @code{bss} directive, i960 148 @item .bss @var{symbol}, @var{length}, @var{align} 149 Reserve @var{length} bytes in the bss section for a local @var{symbol}, 150 aligned to the power of two specified by @var{align}. @var{length} and 151 @var{align} must be positive absolute expressions. This directive 152 differs from @samp{.lcomm} only in that it permits you to specify 153 an alignment. @xref{Lcomm,,@code{.lcomm}}. 154 @end table 155 156 @table @code 157 @cindex @code{extended} directive, i960 158 @item .extended @var{flonums} 159 @code{.extended} expects zero or more flonums, separated by commas; for 160 each flonum, @samp{.extended} emits an @sc{ieee} extended-format (80-bit) 161 floating-point number. 162 163 @cindex @code{leafproc} directive, i960 164 @item .leafproc @var{call-lab}, @var{bal-lab} 165 You can use the @samp{.leafproc} directive in conjunction with the 166 optimized @code{callj} instruction to enable faster calls of leaf 167 procedures. If a procedure is known to call no other procedures, you 168 may define an entry point that skips procedure prolog code (and that does 169 not depend on system-supplied saved context), and declare it as the 170 @var{bal-lab} using @samp{.leafproc}. If the procedure also has an 171 entry point that goes through the normal prolog, you can specify that 172 entry point as @var{call-lab}. 173 174 A @samp{.leafproc} declaration is meant for use in conjunction with the 175 optimized call instruction @samp{callj}; the directive records the data 176 needed later to choose between converting the @samp{callj} into a 177 @code{bal} or a @code{call}. 178 179 @var{call-lab} is optional; if only one argument is present, or if the 180 two arguments are identical, the single argument is assumed to be the 181 @code{bal} entry point. 182 183 @cindex @code{sysproc} directive, i960 184 @item .sysproc @var{name}, @var{index} 185 The @samp{.sysproc} directive defines a name for a system procedure. 186 After you define it using @samp{.sysproc}, you can use @var{name} to 187 refer to the system procedure identified by @var{index} when calling 188 procedures with the optimized call instruction @samp{callj}. 189 190 Both arguments are required; @var{index} must be between 0 and 31 191 (inclusive). 192 @end table 193 194 @node Opcodes for i960 195 @section i960 Opcodes 196 197 @cindex opcodes, i960 198 @cindex i960 opcodes 199 All Intel 960 machine instructions are supported; 200 @pxref{Options-i960,,i960 Command-line Options} for a discussion of 201 selecting the instruction subset for a particular 960 202 architecture.@refill 203 204 Some opcodes are processed beyond simply emitting a single corresponding 205 instruction: @samp{callj}, and Compare-and-Branch or Compare-and-Jump 206 instructions with target displacements larger than 13 bits. 207 208 @menu 209 * callj-i960:: @code{callj} 210 * Compare-and-branch-i960:: Compare-and-Branch 211 @end menu 212 213 @node callj-i960 214 @subsection @code{callj} 215 216 @cindex @code{callj}, i960 pseudo-opcode 217 @cindex i960 @code{callj} pseudo-opcode 218 You can write @code{callj} to have the assembler or the linker determine 219 the most appropriate form of subroutine call: @samp{call}, 220 @samp{bal}, or @samp{calls}. If the assembly source contains 221 enough information---a @samp{.leafproc} or @samp{.sysproc} directive 222 defining the operand---then @code{@value{AS}} translates the 223 @code{callj}; if not, it simply emits the @code{callj}, leaving it 224 for the linker to resolve. 225 226 @node Compare-and-branch-i960 227 @subsection Compare-and-Branch 228 229 @cindex i960 compare/branch instructions 230 @cindex compare/branch instructions, i960 231 The 960 architectures provide combined Compare-and-Branch instructions 232 that permit you to store the branch target in the lower 13 bits of the 233 instruction word itself. However, if you specify a branch target far 234 enough away that its address won't fit in 13 bits, the assembler can 235 either issue an error, or convert your Compare-and-Branch instruction 236 into separate instructions to do the compare and the branch. 237 238 @cindex compare and jump expansions, i960 239 @cindex i960 compare and jump expansions 240 Whether @code{@value{AS}} gives an error or expands the instruction depends 241 on two choices you can make: whether you use the @samp{-no-relax} option, 242 and whether you use a ``Compare and Branch'' instruction or a ``Compare 243 and Jump'' instruction. The ``Jump'' instructions are @emph{always} 244 expanded if necessary; the ``Branch'' instructions are expanded when 245 necessary @emph{unless} you specify @code{-no-relax}---in which case 246 @code{@value{AS}} gives an error instead. 247 248 These are the Compare-and-Branch instructions, their ``Jump'' variants, 249 and the instruction pairs they may expand into: 250 251 @c TEXI2ROFF-KILL 252 @ifinfo 253 @c END TEXI2ROFF-KILL 254 @example 255 Compare and 256 Branch Jump Expanded to 257 ------ ------ ------------ 258 bbc chkbit; bno 259 bbs chkbit; bo 260 cmpibe cmpije cmpi; be 261 cmpibg cmpijg cmpi; bg 262 cmpibge cmpijge cmpi; bge 263 cmpibl cmpijl cmpi; bl 264 cmpible cmpijle cmpi; ble 265 cmpibno cmpijno cmpi; bno 266 cmpibne cmpijne cmpi; bne 267 cmpibo cmpijo cmpi; bo 268 cmpobe cmpoje cmpo; be 269 cmpobg cmpojg cmpo; bg 270 cmpobge cmpojge cmpo; bge 271 cmpobl cmpojl cmpo; bl 272 cmpoble cmpojle cmpo; ble 273 cmpobne cmpojne cmpo; bne 274 @end example 275 @c TEXI2ROFF-KILL 276 @end ifinfo 277 @tex 278 \hskip\tableindent 279 \halign{\hfil {\tt #}\quad&\hfil {\tt #}\qquad&{\tt #}\hfil\cr 280 \omit{\hfil\it Compare and\hfil}\span\omit&\cr 281 {\it Branch}&{\it Jump}&{\it Expanded to}\cr 282 bbc& & chkbit; bno\cr 283 bbs& & chkbit; bo\cr 284 cmpibe& cmpije& cmpi; be\cr 285 cmpibg& cmpijg& cmpi; bg\cr 286 cmpibge& cmpijge& cmpi; bge\cr 287 cmpibl& cmpijl& cmpi; bl\cr 288 cmpible& cmpijle& cmpi; ble\cr 289 cmpibno& cmpijno& cmpi; bno\cr 290 cmpibne& cmpijne& cmpi; bne\cr 291 cmpibo& cmpijo& cmpi; bo\cr 292 cmpobe& cmpoje& cmpo; be\cr 293 cmpobg& cmpojg& cmpo; bg\cr 294 cmpobge& cmpojge& cmpo; bge\cr 295 cmpobl& cmpojl& cmpo; bl\cr 296 cmpoble& cmpojle& cmpo; ble\cr 297 cmpobne& cmpojne& cmpo; bne\cr} 298 @end tex 299 @c END TEXI2ROFF-KILL 300 301 @node Syntax of i960 302 @section Syntax for the i960 303 @menu 304 * i960-Chars:: Special Characters 305 @end menu 306 307 @node i960-Chars 308 @subsection Special Characters 309 310 @cindex line comment character, i960 311 @cindex i960 line comment character 312 The presence of a @samp{#} on a line indicates the start of a comment 313 that extends to the end of the current line. 314 315 If a @samp{#} appears as the first character of a line, the whole line 316 is treated as a comment, but in this case the line can also be a 317 logical line number directive (@pxref{Comments}) or a 318 preprocessor control command (@pxref{Preprocessing}). 319 320 @cindex line separator, i960 321 @cindex statement separator, i960 322 @cindex i960 line separator 323 The @samp{;} character can be used to separate statements on the same 324 line. 325
