1@c Copyright (C) 2002-2016 Free Software Foundation, Inc. 2@c This is part of the GAS manual. 3@c For copying conditions, see the file as.texinfo. 4@c CRIS description contributed by Axis Communications. 5@ifset GENERIC 6@page 7@node CRIS-Dependent 8@chapter CRIS Dependent Features 9@end ifset 10@ifclear GENERIC 11@node Machine Dependencies 12@chapter CRIS Dependent Features 13@end ifclear 14 15@cindex CRIS support 16@menu 17* CRIS-Opts:: Command-line Options 18* CRIS-Expand:: Instruction expansion 19* CRIS-Symbols:: Symbols 20* CRIS-Syntax:: Syntax 21@end menu 22 23@node CRIS-Opts 24@section Command-line Options 25 26@cindex options, CRIS 27@cindex CRIS options 28The CRIS version of @code{@value{AS}} has these 29machine-dependent command-line options. 30 31@cindex @option{--emulation=criself} command line option, CRIS 32@cindex @option{--emulation=crisaout} command line option, CRIS 33@cindex CRIS @option{--emulation=criself} command line option 34@cindex CRIS @option{--emulation=crisaout} command line option 35 36The format of the generated object files can be either ELF or 37a.out, specified by the command-line options 38@option{--emulation=crisaout} and @option{--emulation=criself}. 39The default is ELF (criself), unless @code{@value{AS}} has been 40configured specifically for a.out by using the configuration 41name @code{cris-axis-aout}. 42 43@cindex @option{--underscore} command line option, CRIS 44@cindex @option{--no-underscore} command line option, CRIS 45@cindex CRIS @option{--underscore} command line option 46@cindex CRIS @option{--no-underscore} command line option 47There are two different link-incompatible ELF object file 48variants for CRIS, for use in environments where symbols are 49expected to be prefixed by a leading @samp{_} character and for 50environments without such a symbol prefix. The variant used for 51GNU/Linux port has no symbol prefix. Which variant to produce 52is specified by either of the options @option{--underscore} and 53@option{--no-underscore}. The default is @option{--underscore}. 54Since symbols in CRIS a.out objects are expected to have a 55@samp{_} prefix, specifying @option{--no-underscore} when 56generating a.out objects is an error. Besides the object format 57difference, the effect of this option is to parse register names 58differently (@pxref{crisnous}). The @option{--no-underscore} 59option makes a @samp{$} register prefix mandatory. 60 61@cindex @option{--pic} command line option, CRIS 62@cindex CRIS @option{--pic} command line option 63@cindex Position-independent code, CRIS 64@cindex CRIS position-independent code 65The option @option{--pic} must be passed to @code{@value{AS}} in 66order to recognize the symbol syntax used for ELF (SVR4 PIC) 67position-independent-code (@pxref{crispic}). This will also 68affect expansion of instructions. The expansion with 69@option{--pic} will use PC-relative rather than (slightly 70faster) absolute addresses in those expansions. This option is only 71valid when generating ELF format object files. 72 73@cindex @option{--march=@var{architecture}} command line option, CRIS 74@cindex CRIS @option{--march=@var{architecture}} command line option 75@cindex Architecture variant option, CRIS 76@cindex CRIS architecture variant option 77The option @option{--march=@var{architecture}} 78@anchor{march-option}specifies the recognized instruction set 79and recognized register names. It also controls the 80architecture type of the object file. Valid values for 81@var{architecture} are: 82@table @code 83 84@item v0_v10 85All instructions and register names for any architecture variant 86in the set v0@dots{}v10 are recognized. This is the 87default if the target is configured as cris-*. 88 89@item v10 90Only instructions and register names for CRIS v10 (as found in 91ETRAX 100 LX) are recognized. This is the default if the target 92is configured as crisv10-*. 93 94@item v32 95Only instructions and register names for CRIS v32 (code name 96Guinness) are recognized. This is the default if the target is 97configured as crisv32-*. This value implies 98@option{--no-mul-bug-abort}. (A subsequent 99@option{--mul-bug-abort} will turn it back on.) 100 101@item common_v10_v32 102Only instructions with register names and addressing modes with 103opcodes common to the v10 and v32 are recognized. 104@end table 105 106@cindex @option{-N} command line option, CRIS 107@cindex CRIS @option{-N} command line option 108When @option{-N} is specified, @code{@value{AS}} will emit a 109warning when a 16-bit branch instruction is expanded into a 11032-bit multiple-instruction construct (@pxref{CRIS-Expand}). 111 112@cindex @option{--no-mul-bug-abort} command line option, CRIS 113@cindex @option{--mul-bug-abort} command line option, CRIS 114@cindex CRIS @option{--no-mul-bug-abort} command line option 115@cindex CRIS @option{--mul-bug-abort} command line option 116 117Some versions of the CRIS v10, for example in the Etrax 100 LX, 118contain a bug that causes destabilizing memory accesses when a 119multiply instruction is executed with certain values in the 120first operand just before a cache-miss. When the 121@option{--mul-bug-abort} command line option is active (the 122default value), @code{@value{AS}} will refuse to assemble a file 123containing a multiply instruction at a dangerous offset, one 124that could be the last on a cache-line, or is in a section with 125insufficient alignment. This placement checking does not catch 126any case where the multiply instruction is dangerously placed 127because it is located in a delay-slot. The 128@option{--mul-bug-abort} command line option turns off the 129checking. 130 131@node CRIS-Expand 132@section Instruction expansion 133 134@cindex instruction expansion, CRIS 135@cindex CRIS instruction expansion 136@code{@value{AS}} will silently choose an instruction that fits 137the operand size for @samp{[register+constant]} operands. For 138example, the offset @code{127} in @code{move.d [r3+127],r4} fits 139in an instruction using a signed-byte offset. Similarly, 140@code{move.d [r2+32767],r1} will generate an instruction using a 14116-bit offset. For symbolic expressions and constants that do 142not fit in 16 bits including the sign bit, a 32-bit offset is 143generated. 144 145For branches, @code{@value{AS}} will expand from a 16-bit branch 146instruction into a sequence of instructions that can reach a 147full 32-bit address. Since this does not correspond to a single 148instruction, such expansions can optionally be warned about. 149@xref{CRIS-Opts}. 150 151If the operand is found to fit the range, a @code{lapc} mnemonic 152will translate to a @code{lapcq} instruction. Use @code{lapc.d} 153to force the 32-bit @code{lapc} instruction. 154 155Similarly, the @code{addo} mnemonic will translate to the 156shortest fitting instruction of @code{addoq}, @code{addo.w} and 157@code{addo.d}, when used with a operand that is a constant known 158at assembly time. 159 160@node CRIS-Symbols 161@section Symbols 162@cindex Symbols, built-in, CRIS 163@cindex Symbols, CRIS, built-in 164@cindex CRIS built-in symbols 165@cindex Built-in symbols, CRIS 166 167Some symbols are defined by the assembler. They're intended to 168be used in conditional assembly, for example: 169@smallexample 170 .if ..asm.arch.cris.v32 171 @var{code for CRIS v32} 172 .elseif ..asm.arch.cris.common_v10_v32 173 @var{code common to CRIS v32 and CRIS v10} 174 .elseif ..asm.arch.cris.v10 | ..asm.arch.cris.any_v0_v10 175 @var{code for v10} 176 .else 177 .error "Code needs to be added here." 178 .endif 179@end smallexample 180 181These symbols are defined in the assembler, reflecting 182command-line options, either when specified or the default. 183They are always defined, to 0 or 1. 184@table @code 185 186@item ..asm.arch.cris.any_v0_v10 187This symbol is non-zero when @option{--march=v0_v10} is specified 188or the default. 189 190@item ..asm.arch.cris.common_v10_v32 191Set according to the option @option{--march=common_v10_v32}. 192 193@item ..asm.arch.cris.v10 194Reflects the option @option{--march=v10}. 195 196@item ..asm.arch.cris.v32 197Corresponds to @option{--march=v10}. 198@end table 199 200Speaking of symbols, when a symbol is used in code, it can have 201a suffix modifying its value for use in position-independent 202code. @xref{CRIS-Pic}. 203 204@node CRIS-Syntax 205@section Syntax 206 207There are different aspects of the CRIS assembly syntax. 208 209@menu 210* CRIS-Chars:: Special Characters 211* CRIS-Pic:: Position-Independent Code Symbols 212* CRIS-Regs:: Register Names 213* CRIS-Pseudos:: Assembler Directives 214@end menu 215 216@node CRIS-Chars 217@subsection Special Characters 218@cindex line comment characters, CRIS 219@cindex CRIS line comment characters 220 221The character @samp{#} is a line comment character. It starts a 222comment if and only if it is placed at the beginning of a line. 223 224A @samp{;} character starts a comment anywhere on the line, 225causing all characters up to the end of the line to be ignored. 226 227A @samp{@@} character is handled as a line separator equivalent 228to a logical new-line character (except in a comment), so 229separate instructions can be specified on a single line. 230 231@node CRIS-Pic 232@subsection Symbols in position-independent code 233@cindex Symbols in position-independent code, CRIS 234@cindex CRIS symbols in position-independent code 235@cindex Position-independent code, symbols in, CRIS 236 237When generating @anchor{crispic}position-independent code (SVR4 238PIC) for use in cris-axis-linux-gnu or crisv32-axis-linux-gnu 239shared libraries, symbol 240suffixes are used to specify what kind of run-time symbol lookup 241will be used, expressed in the object as different 242@emph{relocation types}. Usually, all absolute symbol values 243must be located in a table, the @emph{global offset table}, 244leaving the code position-independent; independent of values of 245global symbols and independent of the address of the code. The 246suffix modifies the value of the symbol, into for example an 247index into the global offset table where the real symbol value 248is entered, or a PC-relative value, or a value relative to the 249start of the global offset table. All symbol suffixes start 250with the character @samp{:} (omitted in the list below). Every 251symbol use in code or a read-only section must therefore have a 252PIC suffix to enable a useful shared library to be created. 253Usually, these constructs must not be used with an additive 254constant offset as is usually allowed, i.e.@: no 4 as in 255@code{symbol + 4} is allowed. This restriction is checked at 256link-time, not at assembly-time. 257 258@table @code 259@item GOT 260 261Attaching this suffix to a symbol in an instruction causes the 262symbol to be entered into the global offset table. The value is 263a 32-bit index for that symbol into the global offset table. 264The name of the corresponding relocation is 265@samp{R_CRIS_32_GOT}. Example: @code{move.d 266[$r0+extsym:GOT],$r9} 267 268@item GOT16 269 270Same as for @samp{GOT}, but the value is a 16-bit index into the 271global offset table. The corresponding relocation is 272@samp{R_CRIS_16_GOT}. Example: @code{move.d 273[$r0+asymbol:GOT16],$r10} 274 275@item PLT 276 277This suffix is used for function symbols. It causes a 278@emph{procedure linkage table}, an array of code stubs, to be 279created at the time the shared object is created or linked 280against, together with a global offset table entry. The value 281is a pc-relative offset to the corresponding stub code in the 282procedure linkage table. This arrangement causes the run-time 283symbol resolver to be called to look up and set the value of the 284symbol the first time the function is called (at latest; 285depending environment variables). It is only safe to leave the 286symbol unresolved this way if all references are function calls. 287The name of the relocation is @samp{R_CRIS_32_PLT_PCREL}. 288Example: @code{add.d fnname:PLT,$pc} 289 290@item PLTG 291 292Like PLT, but the value is relative to the beginning of the 293global offset table. The relocation is 294@samp{R_CRIS_32_PLT_GOTREL}. Example: @code{move.d 295fnname:PLTG,$r3} 296 297@item GOTPLT 298 299Similar to @samp{PLT}, but the value of the symbol is a 32-bit 300index into the global offset table. This is somewhat of a mix 301between the effect of the @samp{GOT} and the @samp{PLT} suffix; 302the difference to @samp{GOT} is that there will be a procedure 303linkage table entry created, and that the symbol is assumed to 304be a function entry and will be resolved by the run-time 305resolver as with @samp{PLT}. The relocation is 306@samp{R_CRIS_32_GOTPLT}. Example: @code{jsr 307[$r0+fnname:GOTPLT]} 308 309@item GOTPLT16 310 311A variant of @samp{GOTPLT} giving a 16-bit value. Its 312relocation name is @samp{R_CRIS_16_GOTPLT}. Example: @code{jsr 313[$r0+fnname:GOTPLT16]} 314 315@item GOTOFF 316 317This suffix must only be attached to a local symbol, but may be 318used in an expression adding an offset. The value is the 319address of the symbol relative to the start of the global offset 320table. The relocation name is @samp{R_CRIS_32_GOTREL}. 321Example: @code{move.d [$r0+localsym:GOTOFF],r3} 322@end table 323 324@node CRIS-Regs 325@subsection Register names 326@cindex register names, CRIS 327@cindex CRIS register names 328 329A @samp{$} character may always prefix a general or special 330register name in an instruction operand but is mandatory when 331the option @option{--no-underscore} is specified or when the 332@code{.syntax register_prefix} directive is in effect 333(@pxref{crisnous}). Register names are case-insensitive. 334 335@node CRIS-Pseudos 336@subsection Assembler Directives 337@cindex assembler directives, CRIS 338@cindex pseudo-ops, CRIS 339@cindex CRIS assembler directives 340@cindex CRIS pseudo-ops 341 342There are a few CRIS-specific pseudo-directives in addition to 343the generic ones. @xref{Pseudo Ops}. Constants emitted by 344pseudo-directives are in little-endian order for CRIS. There is 345no support for floating-point-specific directives for CRIS. 346 347@table @code 348@item .dword EXPRESSIONS 349@cindex assembler directive .dword, CRIS 350@cindex pseudo-op .dword, CRIS 351@cindex CRIS assembler directive .dword 352@cindex CRIS pseudo-op .dword 353 354The @code{.dword} directive is a synonym for @code{.int}, 355expecting zero or more EXPRESSIONS, separated by commas. For 356each expression, a 32-bit little-endian constant is emitted. 357 358@item .syntax ARGUMENT 359@cindex assembler directive .syntax, CRIS 360@cindex pseudo-op .syntax, CRIS 361@cindex CRIS assembler directive .syntax 362@cindex CRIS pseudo-op .syntax 363The @code{.syntax} directive takes as @var{ARGUMENT} one of the 364following case-sensitive choices. 365 366@table @code 367@item no_register_prefix 368 369The @code{.syntax no_register_prefix} @anchor{crisnous}directive 370makes a @samp{$} character prefix on all registers optional. It 371overrides a previous setting, including the corresponding effect 372of the option @option{--no-underscore}. If this directive is 373used when ordinary symbols do not have a @samp{_} character 374prefix, care must be taken to avoid ambiguities whether an 375operand is a register or a symbol; using symbols with names the 376same as general or special registers then invoke undefined 377behavior. 378 379@item register_prefix 380 381This directive makes a @samp{$} character prefix on all 382registers mandatory. It overrides a previous setting, including 383the corresponding effect of the option @option{--underscore}. 384 385@item leading_underscore 386 387This is an assertion directive, emitting an error if the 388@option{--no-underscore} option is in effect. 389 390@item no_leading_underscore 391 392This is the opposite of the @code{.syntax leading_underscore} 393directive and emits an error if the option @option{--underscore} 394is in effect. 395@end table 396 397@item .arch ARGUMENT 398@cindex assembler directive .arch, CRIS 399@cindex pseudo-op .arch, CRIS 400@cindex CRIS assembler directive .arch 401@cindex CRIS pseudo-op .arch 402This is an assertion directive, giving an error if the specified 403@var{ARGUMENT} is not the same as the specified or default value 404for the @option{--march=@var{architecture}} option 405(@pxref{march-option}). 406 407@c If you compare with md_pseudo_table, you see that we don't 408@c document ".file" and ".loc" here. This is because we're just 409@c wrapping the corresponding ELF function and emitting an error for 410@c a.out. 411@end table 412