| @c Copyright 2002 Free Software Foundation, Inc. |
| @c This is part of the GAS manual. |
| @c For copying conditions, see the file as.texinfo. |
| @c CRIS description contributed by Axis Communications. |
| @ifset GENERIC |
| @page |
| @node CRIS-Dependent |
| @chapter CRIS Dependent Features |
| @end ifset |
| @ifclear GENERIC |
| @node Machine Dependencies |
| @chapter CRIS Dependent Features |
| @end ifclear |
| |
| @cindex CRIS support |
| @menu |
| * CRIS-Opts:: Command-line Options |
| * CRIS-Expand:: Instruction expansion |
| * CRIS-Syntax:: Syntax |
| @end menu |
| |
| @node CRIS-Opts |
| @section Command-line Options |
| |
| @cindex options, CRIS |
| @cindex CRIS options |
| The CRIS version of @code{@value{AS}} has these |
| machine-dependent command-line options. |
| |
| @cindex @option{--emulation=criself} command line option, CRIS |
| @cindex @option{--emulation=crisaout} command line option, CRIS |
| @cindex CRIS @option{--emulation=criself} command line option |
| @cindex CRIS @option{--emulation=crisaout} command line option |
| |
| The format of the generated object files can be either ELF or |
| a.out, specified by the command-line options |
| @option{--emulation=crisaout} and @option{--emulation=criself}. |
| The default is ELF (criself), unless @code{@value{AS}} has been |
| configured specifically for a.out by using the configuration |
| name @code{cris-axis-aout}. |
| |
| @cindex @option{--underscore} command line option, CRIS |
| @cindex @option{--no-underscore} command line option, CRIS |
| @cindex CRIS @option{--underscore} command line option |
| @cindex CRIS @option{--no-underscore} command line option |
| There are two different link-incompatible ELF object file |
| variants for CRIS, for use in environments where symbols are |
| expected to be prefixed by a leading @samp{_} character and for |
| environments without such a symbol prefix. The variant used for |
| GNU/Linux port has no symbol prefix. Which variant to produce |
| is specified by either of the options @option{--underscore} and |
| @option{--no-underscore}. The default is @option{--underscore}. |
| Since symbols in CRIS a.out objects are expected to have a |
| @samp{_} prefix, specifying @option{--no-underscore} when |
| generating a.out objects is an error. Besides the object format |
| difference, the effect of this option is to parse register names |
| differently (@pxref{crisnous}). The @option{--no-underscore} |
| option makes a @samp{$} register prefix mandatory. |
| |
| @cindex @option{--pic} command line option, CRIS |
| @cindex CRIS @option{--pic} command line option |
| @cindex Position-independent code, CRIS |
| @cindex CRIS position-independent code |
| The option @option{--pic} must be passed to @code{@value{AS}} in |
| order to recognize the symbol syntax used for ELF (SVR4 PIC) |
| position-independent-code (@pxref{crispic}). This will also |
| affect expansion of instructions. The expansion with |
| @option{--pic} will use PC-relative rather than (slightly |
| faster) absolute addresses in those expansions. |
| |
| @cindex @option{-N} command line option, CRIS |
| @cindex CRIS @option{-N} command line option |
| When @option{-N} is specified, @code{@value{AS}} will emit a |
| warning when a 16-bit branch instruction is expanded into a |
| 32-bit multiple-instruction construct (@pxref{CRIS-Expand}). |
| |
| @node CRIS-Expand |
| @section Instruction expansion |
| |
| @cindex instruction expansion, CRIS |
| @cindex CRIS instruction expansion |
| @code{@value{AS}} will silently choose an instruction that fits |
| the operand size for @samp{[register+constant]} operands. For |
| example, the offset @code{127} in @code{move.d [r3+127],r4} fits |
| in an instruction using a signed-byte offset. Similarly, |
| @code{move.d [r2+32767],r1} will generate an instruction using a |
| 16-bit offset. For symbolic expressions and constants that do |
| not fit in 16 bits including the sign bit, a 32-bit offset is |
| generated. |
| |
| For branches, @code{@value{AS}} will expand from a 16-bit branch |
| instruction into a sequence of instructions that can reach a |
| full 32-bit address. Since this does not correspond to a single |
| instruction, such expansions can optionally be warned about. |
| @xref{CRIS-Opts}. |
| |
| @node CRIS-Syntax |
| @section Syntax |
| |
| There are different aspects of the CRIS assembly syntax. |
| |
| @menu |
| * CRIS-Chars:: Special Characters |
| * CRIS-Pic:: Position-Independent Code Symbols |
| * CRIS-Regs:: Register Names |
| * CRIS-Pseudos:: Assembler Directives |
| @end menu |
| |
| @node CRIS-Chars |
| @subsection Special Characters |
| @cindex line comment characters, CRIS |
| @cindex CRIS line comment characters |
| |
| The character @samp{#} is a line comment character. It starts a |
| comment if and only if it is placed at the beginning of a line. |
| |
| A @samp{;} character starts a comment anywhere on the line, |
| causing all characters up to the end of the line to be ignored. |
| |
| A @samp{@@} character is handled as a line separator equivalent |
| to a logical new-line character (except in a comment), so |
| separate instructions can be specified on a single line. |
| |
| @node CRIS-Pic |
| @subsection Symbols in position-independent code |
| @cindex Symbols in position-independent code, CRIS |
| @cindex CRIS symbols in position-independent code |
| @cindex Position-independent code, symbols in, CRIS |
| |
| When generating @anchor{crispic}position-independent code (SVR4 |
| PIC) for use in cris-axis-linux-gnu shared libraries, symbol |
| suffixes are used to specify what kind of run-time symbol lookup |
| will be used, expressed in the object as different |
| @emph{relocation types}. Usually, all absolute symbol values |
| must be located in a table, the @emph{global offset table}, |
| leaving the code position-independent; independent of values of |
| global symbols and independent of the address of the code. The |
| suffix modifies the value of the symbol, into for example an |
| index into the global offset table where the real symbol value |
| is entered, or a PC-relative value, or a value relative to the |
| start of the global offset table. All symbol suffixes start |
| with the character @samp{:} (omitted in the list below). Every |
| symbol use in code or a read-only section must therefore have a |
| PIC suffix to enable a useful shared library to be created. |
| Usually, these constructs must not be used with an additive |
| constant offset as is usually allowed, i.e.@: no 4 as in |
| @code{symbol + 4} is allowed. This restriction is checked at |
| link-time, not at assembly-time. |
| |
| @table @code |
| @item GOT |
| |
| Attaching this suffix to a symbol in an instruction causes the |
| symbol to be entered into the global offset table. The value is |
| a 32-bit index for that symbol into the global offset table. |
| The name of the corresponding relocation is |
| @samp{R_CRIS_32_GOT}. Example: @code{move.d |
| [$r0+extsym:GOT],$r9} |
| |
| @item GOT16 |
| |
| Same as for @samp{GOT}, but the value is a 16-bit index into the |
| global offset table. The corresponding relocation is |
| @samp{R_CRIS_16_GOT}. Example: @code{move.d |
| [$r0+asymbol:GOT16],$r10} |
| |
| @item PLT |
| |
| This suffix is used for function symbols. It causes a |
| @emph{procedure linkage table}, an array of code stubs, to be |
| created at the time the shared object is created or linked |
| against, together with a global offset table entry. The value |
| is a pc-relative offset to the corresponding stub code in the |
| procedure linkage table. This arrangement causes the run-time |
| symbol resolver to be called to look up and set the value of the |
| symbol the first time the function is called (at latest; |
| depending environment variables). It is only safe to leave the |
| symbol unresolved this way if all references are function calls. |
| The name of the relocation is @samp{R_CRIS_32_PLT_PCREL}. |
| Example: @code{add.d fnname:PLT,$pc} |
| |
| @item PLTG |
| |
| Like PLT, but the value is relative to the beginning of the |
| global offset table. The relocation is |
| @samp{R_CRIS_32_PLT_GOTREL}. Example: @code{move.d |
| fnname:PLTG,$r3} |
| |
| @item GOTPLT |
| |
| Similar to @samp{PLT}, but the value of the symbol is a 32-bit |
| index into the global offset table. This is somewhat of a mix |
| between the effect of the @samp{GOT} and the @samp{PLT} suffix; |
| the difference to @samp{GOT} is that there will be a procedure |
| linkage table entry created, and that the symbol is assumed to |
| be a function entry and will be resolved by the run-time |
| resolver as with @samp{PLT}. The relocation is |
| @samp{R_CRIS_32_GOTPLT}. Example: @code{jsr |
| [$r0+fnname:GOTPLT]} |
| |
| @item GOTPLT16 |
| |
| A variant of @samp{GOTPLT} giving a 16-bit value. Its |
| relocation name is @samp{R_CRIS_16_GOTPLT}. Example: @code{jsr |
| [$r0+fnname:GOTPLT16]} |
| |
| @item GOTOFF |
| |
| This suffix must only be attached to a local symbol, but may be |
| used in an expression adding an offset. The value is the |
| address of the symbol relative to the start of the global offset |
| table. The relocation name is @samp{R_CRIS_32_GOTREL}. |
| Example: @code{move.d [$r0+localsym:GOTOFF],r3} |
| @end table |
| |
| @node CRIS-Regs |
| @subsection Register names |
| @cindex register names, CRIS |
| @cindex CRIS register names |
| |
| A @samp{$} character may always prefix a general or special |
| register name in an instruction operand but is mandatory when |
| the option @option{--no-underscore} is specified or when the |
| @code{.syntax register_prefix} directive is in effect |
| (@pxref{crisnous}). Register names are case-insensitive. |
| |
| @node CRIS-Pseudos |
| @subsection Assembler Directives |
| @cindex assembler directives, CRIS |
| @cindex pseudo-ops, CRIS |
| @cindex CRIS assembler directives |
| @cindex CRIS pseudo-ops |
| |
| There are a few CRIS-specific pseudo-directives in addition to |
| the generic ones. @xref{Pseudo Ops}. Constants emitted by |
| pseudo-directives are in little-endian order for CRIS. There is |
| no support for floating-point-specific directives for CRIS. |
| |
| @table @code |
| @item .dword EXPRESSIONS |
| @cindex assembler directive .dword, CRIS |
| @cindex pseudo-op .dword, CRIS |
| @cindex CRIS assembler directive .dword |
| @cindex CRIS pseudo-op .dword |
| |
| The @code{.dword} directive is a synonym for @code{.int}, |
| expecting zero or more EXPRESSIONS, separated by commas. For |
| each expression, a 32-bit little-endian constant is emitted. |
| |
| @item .syntax ARGUMENT |
| @cindex assembler directive .syntax, CRIS |
| @cindex pseudo-op .syntax, CRIS |
| @cindex CRIS assembler directive .syntax |
| @cindex CRIS pseudo-op .syntax |
| The @code{.syntax} directive takes as ARGUMENT one of the |
| following case-sensitive choices. |
| |
| @table @code |
| @item no_register_prefix |
| |
| The @code{.syntax no_register_prefix} @anchor{crisnous}directive |
| makes a @samp{$} character prefix on all registers optional. It |
| overrides a previous setting, including the corresponding effect |
| of the option @option{--no-underscore}. If this directive is |
| used when ordinary symbols do not have a @samp{_} character |
| prefix, care must be taken to avoid ambiguities whether an |
| operand is a register or a symbol; using symbols with names the |
| same as general or special registers then invoke undefined |
| behavior. |
| |
| @item register_prefix |
| |
| This directive makes a @samp{$} character prefix on all |
| registers mandatory. It overrides a previous setting, including |
| the corresponding effect of the option @option{--underscore}. |
| |
| @item leading_underscore |
| |
| This is an assertion directive, emitting an error if the |
| @option{--no-underscore} option is in effect. |
| |
| @item no_leading_underscore |
| |
| This is the opposite of the @code{.syntax leading_underscore} |
| directive and emits an error if the option @option{--underscore} |
| is in effect. |
| @end table |
| |
| @c If you compare with md_pseudo_table, you see that we don't |
| @c document ".file" and ".loc" here. This is because we're just |
| @c wrapping the corresponding ELF function and emitting an error for |
| @c a.out. |
| @end table |