as.texinfo

基于4个mips核的noc设计

listing-control directives have no effect.

The letters after @samp{-a} may be combined into one option,
@emph{e.g.}, @samp{-aln}.

@node D
@section @code{-D}

@kindex -D
This option has no effect whatsoever, but it is accepted to make it more
likely that scripts written for other assemblers also work with
@code{@value{AS}}.

@node f
@section Work Faster: @code{-f}

@kindex -f
@cindex trusted compiler
@cindex faster processing (@code{-f})
@samp{-f} should only be used when assembling programs written by a
(trusted) compiler.  @samp{-f} stops the assembler from doing whitespace
and comment preprocessing on
the input file(s) before assembling them.  @xref{Preprocessing,
,Preprocessing}.

@quotation
@emph{Warning:} if you use @samp{-f} when the files actually need to be
preprocessed (if they contain comments, for example), @code{@value{AS}} does
not work correctly.
@end quotation

@node I
@section @code{.include} search path: @code{-I} @var{path}

@kindex -I @var{path}
@cindex paths for @code{.include}
@cindex search path for @code{.include}
@cindex @code{include} directive search path
Use this option to add a @var{path} to the list of directories
@code{@value{AS}} searches for files specified in @code{.include}
directives (@pxref{Include,,@code{.include}}).  You may use @code{-I} as
many times as necessary to include a variety of paths.  The current
working directory is always searched first; after that, @code{@value{AS}}
searches any @samp{-I} directories in the same order as they were
specified (left to right) on the command line.

@node K
@section Difference Tables: @code{-K}

@kindex -K
@ifclear DIFF-TBL-KLUGE
On the @value{TARGET} family, this option is allowed, but has no effect.  It is
permitted for compatibility with the @sc{gnu} assembler on other platforms,
where it can be used to warn when the assembler alters the machine code
generated for @samp{.word} directives in difference tables.  The @value{TARGET}
family does not have the addressing limitations that sometimes lead to this
alteration on other platforms.
@end ifclear

@ifset DIFF-TBL-KLUGE
@cindex difference tables, warning
@cindex warning for altered difference tables
@code{@value{AS}} sometimes alters the code emitted for directives of the form
@samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
You can use the @samp{-K} option if you want a warning issued when this
is done.
@end ifset

@node L
@section Include Local Labels: @code{-L}

@kindex -L
@cindex local labels, retaining in output
Labels beginning with @samp{L} (upper case only) are called @dfn{local
labels}. @xref{Symbol Names}.  Normally you do not see such labels when
debugging, because they are intended for the use of programs (like
compilers) that compose assembler programs, not for your notice.
Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
normally debug with them.

This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
in the object file.  Usually if you do this you also tell the linker
@code{@value{LD}} to preserve symbols whose names begin with @samp{L}.

By default, a local label is any label beginning with @samp{L}, but each
target is allowed to redefine the local label prefix.
@ifset HPPA
On the HPPA local labels begin with @samp{L$}.
@end ifset

@node M
@section Assemble in MRI Compatibility Mode: @code{-M}

@kindex -M
@cindex MRI compatibility mode
The @code{-M} or @code{--mri} option selects MRI compatibility mode.  This
changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
configured target) assembler from Microtec Research.  The exact nature of the
MRI syntax will not be documented here; see the MRI manuals for more
information.  Note in particular that the handling of macros and macro
arguments is somewhat different.  The purpose of this option is to permit
assembling existing MRI assembler code using @code{@value{AS}}.

The MRI compatibility is not complete.  Certain operations of the MRI assembler
depend upon its object file format, and can not be supported using other object
file formats.  Supporting these would require enhancing each object file format
individually.  These are:

@itemize @bullet
@item global symbols in common section

The m68k MRI assembler supports common sections which are merged by the linker.
Other object file formats do not support this.  @code{@value{AS}} handles
common sections by treating them as a single common symbol.  It permits local
symbols to be defined within a common section, but it can not support global
symbols, since it has no way to describe them.

@item complex relocations

The MRI assemblers support relocations against a negated section address, and
relocations which combine the start addresses of two or more sections.  These
are not support by other object file formats.

@item @code{END} pseudo-op specifying start address

The MRI @code{END} pseudo-op permits the specification of a start address.
This is not supported by other object file formats.  The start address may
instead be specified using the @code{-e} option to the linker, or in a linker
script.

@item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops

The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
name to the output file.  This is not supported by other object file formats.

@item @code{ORG} pseudo-op

The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
address.  This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
which changes the location within the current section.  Absolute sections are
not supported by other object file formats.  The address of a section may be
assigned within a linker script.
@end itemize

There are some other features of the MRI assembler which are not supported by
@code{@value{AS}}, typically either because they are difficult or because they
seem of little consequence.  Some of these may be supported in future releases.

@itemize @bullet

@item EBCDIC strings

EBCDIC strings are not supported.

@item packed binary coded decimal

Packed binary coded decimal is not supported.  This means that the @code{DC.P}
and @code{DCB.P} pseudo-ops are not supported.

@item @code{FEQU} pseudo-op

The m68k @code{FEQU} pseudo-op is not supported.

@item @code{NOOBJ} pseudo-op

The m68k @code{NOOBJ} pseudo-op is not supported.

@item @code{OPT} branch control options

The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
@code{BRL}, and @code{BRW}---are ignored.  @code{@value{AS}} automatically
relaxes all branches, whether forward or backward, to an appropriate size, so
these options serve no purpose.

@item @code{OPT} list control options

The following m68k @code{OPT} list control options are ignored: @code{C},
@code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
@code{MEX}, @code{MC}, @code{MD}, @code{X}.

@item other @code{OPT} options

The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
@code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.

@item @code{OPT} @code{D} option is default

The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
@code{OPT NOD} may be used to turn it off.

@item @code{XREF} pseudo-op.

The m68k @code{XREF} pseudo-op is ignored.

@item @code{.debug} pseudo-op

The i960 @code{.debug} pseudo-op is not supported.

@item @code{.extended} pseudo-op

The i960 @code{.extended} pseudo-op is not supported.

@item @code{.list} pseudo-op.

The various options of the i960 @code{.list} pseudo-op are not supported.

@item @code{.optimize} pseudo-op

The i960 @code{.optimize} pseudo-op is not supported.

@item @code{.output} pseudo-op

The i960 @code{.output} pseudo-op is not supported.

@item @code{.setreal} pseudo-op

The i960 @code{.setreal} pseudo-op is not supported.

@end itemize

@node MD
@section Dependency tracking: @code{--MD}

@kindex --MD
@cindex dependency tracking
@cindex make rules

@code{@value{AS}} can generate a dependency file for the file it creates.  This
file consists of a single rule suitable for @code{make} describing the
dependencies of the main source file.

The rule is written to the file named in its argument.

This feature is used in the automatic updating of makefiles.

@node o
@section Name the Object File: @code{-o}

@kindex -o
@cindex naming object file
@cindex object file name
There is always one object file output when you run @code{@value{AS}}.  By
default it has the name
@ifset GENERIC
@ifset I960
@file{a.out} (or @file{b.out}, for Intel 960 targets only).
@end ifset
@ifclear I960
@file{a.out}.
@end ifclear
@end ifset
@ifclear GENERIC
@ifset I960
@file{b.out}.
@end ifset
@ifclear I960
@file{a.out}.
@end ifclear
@end ifclear
You use this option (which takes exactly one filename) to give the
object file a different name.

Whatever the object file is called, @code{@value{AS}} overwrites any
existing file of the same name.

@node R
@section Join Data and Text Sections: @code{-R}

@kindex -R
@cindex data and text sections, joining
@cindex text and data sections, joining
@cindex joining text and data sections
@cindex merging text and data sections
@code{-R} tells @code{@value{AS}} to write the object file as if all
data-section data lives in the text section.  This is only done at
the very last moment:  your binary data are the same, but data
section parts are relocated differently.  The data section part of
your object file is zero bytes long because all its bytes are
appended to the text section.  (@xref{Sections,,Sections and Relocation}.)

When you specify @code{-R} it would be possible to generate shorter
address displacements (because we do not have to cross between text and
data section).  We refrain from doing this simply for compatibility with
older versions of @code{@value{AS}}.  In future, @code{-R} may work this way.

@ifset COFF
When @code{@value{AS}} is configured for COFF output,
this option is only useful if you use sections named @samp{.text} and
@samp{.data}.
@end ifset

@ifset HPPA
@code{-R} is not supported for any of the HPPA targets.  Using
@code{-R} generates a warning from @code{@value{AS}}.
@end ifset

@node statistics
@section Display Assembly Statistics: @code{--statistics}

@kindex --statistics
@cindex statistics, about assembly
@cindex time, total for assembly
@cindex space used, maximum for assembly
Use @samp{--statistics} to display two statistics about the resources used by
@code{@value{AS}}: the maximum amount of space allocated during the assembly
(in bytes), and the total execution time taken for the assembly (in @sc{cpu}
seconds).

@node traditional-format
@section Compatible output: @code{--traditional-format}

@kindex --traditional-format
For some targets, the output of @code{@value{AS}} is different in some ways
from the output of some existing assembler.  This switch requests
@code{@value{AS}} to use the traditional format instead.

For example, it disables the exception frame optimizations which
@code{@value{AS}} normally does by default on @code{@value{GCC}} output.

@node v
@section Announce Version: @code{-v}

@kindex -v
@kindex -version
@cindex assembler version
@cindex version of assembler
You can find out what version of as is running by including the
option @samp{-v} (which you can also spell as @samp{-version}) on the
command line.

@node W
@section Control Warnings: @code{-W}, @code{--warn}, @code{--no-warn}, @code{--fatal-warnings}

@code{@value{AS}} should never give a warning or error message when
assembling compiler output.  But programs written by people often
cause @code{@value{AS}} to give a warning that a particular assumption was
made.  All such warnings are directed to the standard error file.

@kindex @samp{-W}
@kindex @samp{--no-warn}
@cindex suppressing warnings
@cindex warnings, suppressing
If you use the @code{-W} and @code{--no-warn} options, no warnings are issued.
This only affects the warning messages: it does not change any particular of
how @code{@value{AS}} assembles your file.  Errors, which stop the assembly,
are still reported.

@kindex @samp{--fatal-warnings}
@cindex errors, caused by warnings
@cindex warnings, causing error
If you use the @code{--fatal-warnings} option, @code{@value{AS}} considers
files that generate warnings to be in error.

@kindex @samp{--warn}
@cindex warnings, switching on
You can switch these options off again by specifying @code{--warn}, which
causes warnings to be output as usual.

@node Z
@section Generate Object File in Spite of Errors: @code{-Z}
@cindex object file, after errors
@cindex errors, continuing after
After an error message, @code{@value{AS}} normally produces no output.  If for
some reason you are interested in object file output even after
@code{@value{AS}} gives an error message on your program, use the @samp{-Z}
option.  If there are any errors, @code{@value{AS}} continues anyways, and
writes an object file after a final warning message of the form @samp{@var{n}
errors, @var{m} warnings, generating bad object file.}

@node Syntax
@chapter Syntax

@cindex machine-independent syntax
@cindex syntax, machine-independent
This chapter describes the machine-independent syntax allowed in a
source file.  @code{@value{AS}} syntax is similar to what many other
assemblers use; it is inspired by the BSD 4.2
@ifclear VAX
assembler.
@end ifclear
@ifset VAX
assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
@end ifset

@menu
* Preprocessing::              Preprocessing
* Whitespace::                  Whitespace
* Comments::                    Comments
* Symbol Intro::                Symbols
* Statements::                  Statements