as.texinfo

基于4个mips核的noc设计

@ifclear GENERIC
We also cover special features in the @value{TARGET}
configuration of @code{@value{AS}}, including assembler directives.
@end ifclear
@ifset GENERIC
This manual also describes some of the machine-dependent features of
various flavors of the assembler.
@end ifset

@cindex machine instructions (not covered)
On the other hand, this manual is @emph{not} intended as an introduction
to programming in assembly language---let alone programming in general!
In a similar vein, we make no attempt to introduce the machine
architecture; we do @emph{not} describe the instruction set, standard
mnemonics, registers or addressing modes that are standard to a
particular architecture.
@ifset GENERIC
You may want to consult the manufacturer's
machine architecture manual for this information.
@end ifset
@ifclear GENERIC
@ifset H8/300
For information on the H8/300 machine instruction set, see @cite{H8/300
Series Programming Manual} (Hitachi ADE--602--025).  For the H8/300H,
see @cite{H8/300H Series Programming Manual} (Hitachi).
@end ifset
@ifset H8/500
For information on the H8/500 machine instruction set, see @cite{H8/500
Series Programming Manual} (Hitachi M21T001).
@end ifset
@ifset SH
For information on the Hitachi SH machine instruction set, see
@cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
@end ifset
@ifset Z8000
For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
@end ifset
@end ifclear

@c I think this is [e-mail], 17jan1991
@ignore
Throughout this manual, we assume that you are running @dfn{GNU},
the portable operating system from the @dfn{Free Software
Foundation, Inc.}.  This restricts our attention to certain kinds of
computer (in particular, the kinds of computers that @sc{gnu} can run on);
once this assumption is granted examples and definitions need less
qualification.

@code{@value{AS}} is part of a team of programs that turn a high-level
human-readable series of instructions into a low-level
computer-readable series of instructions.  Different versions of
@code{@value{AS}} are used for different kinds of computer.
@end ignore

@c There used to be a section "Terminology" here, which defined
@c "contents", "byte", "word", and "long".  Defining "word" to any
@c particular size is confusing when the .word directive may generate 16
@c bits on one machine and 32 bits on another; in general, for the user
@c version of this manual, none of these terms seem essential to define.
@c They were used very little even in the former draft of the manual;
@c this draft makes an effort to avoid them (except in names of
@c directives).

@node GNU Assembler
@section The GNU Assembler

@sc{gnu} @code{as} is really a family of assemblers.
@ifclear GENERIC
This manual describes @code{@value{AS}}, a member of that family which is
configured for the @value{TARGET} architectures.
@end ifclear
If you use (or have used) the @sc{gnu} assembler on one architecture, you
should find a fairly similar environment when you use it on another
architecture.  Each version has much in common with the others,
including object file formats, most assembler directives (often called
@dfn{pseudo-ops}) and assembler syntax.@refill

@cindex purpose of @sc{gnu} assembler
@code{@value{AS}} is primarily intended to assemble the output of the
@sc{gnu} C compiler @code{@value{GCC}} for use by the linker
@code{@value{LD}}.  Nevertheless, we've tried to make @code{@value{AS}}
assemble correctly everything that other assemblers for the same
machine would assemble.
@ifset VAX
Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
@end ifset
@ifset M680X0
@c This remark should appear in generic version of manual; assumption
@c here is that generic version sets M680x0.
This doesn't mean @code{@value{AS}} always uses the same syntax as another
assembler for the same architecture; for example, we know of several
incompatible versions of 680x0 assembly language syntax.
@end ifset

Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
program in one pass of the source file.  This has a subtle impact on the
@kbd{.org} directive (@pxref{Org,,@code{.org}}).

@node Object Formats
@section Object File Formats

@cindex object file format
The @sc{gnu} assembler can be configured to produce several alternative
object file formats.  For the most part, this does not affect how you
write assembly language programs; but directives for debugging symbols
are typically different in different file formats.  @xref{Symbol
Attributes,,Symbol Attributes}.
@ifclear GENERIC
@ifclear MULTI-OBJ
On the @value{TARGET}, @code{@value{AS}} is configured to produce
@value{OBJ-NAME} format object files.
@end ifclear
@c The following should exhaust all configs that set MULTI-OBJ, ideally
@ifset A29K
On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
@code{a.out} or COFF format object files.
@end ifset
@ifset I960
On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
@code{b.out} or COFF format object files.
@end ifset
@ifset HPPA
On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
SOM or ELF format object files.
@end ifset
@end ifclear

@node Command Line
@section Command Line

@cindex command line conventions
After the program name @code{@value{AS}}, the command line may contain
options and file names.  Options may appear in any order, and may be
before, after, or between file names.  The order of file names is
significant.

@cindex standard input, as input file
@kindex --
@file{--} (two hyphens) by itself names the standard input file
explicitly, as one of the files for @code{@value{AS}} to assemble.

@cindex options, command line
Except for @samp{--} any command line argument that begins with a
hyphen (@samp{-}) is an option.  Each option changes the behavior of
@code{@value{AS}}.  No option changes the way another option works.  An
option is a @samp{-} followed by one or more letters; the case of
the letter is important.   All options are optional.

Some options expect exactly one file name to follow them.  The file
name may either immediately follow the option's letter (compatible
with older assemblers) or it may be the next command argument (@sc{gnu}
standard).  These two command lines are equivalent:

@smallexample
@value{AS} -o my-object-file.o mumble.s
@value{AS} -omy-object-file.o mumble.s
@end smallexample

@node Input Files
@section Input Files

@cindex input
@cindex source program
@cindex files, input
We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
describe the program input to one run of @code{@value{AS}}.  The program may
be in one or more files; how the source is partitioned into files
doesn't change the meaning of the source.

@c I added "con" prefix to "catenation" just to prove I can overcome my
@c APL training...   [e-mail]
The source program is a concatenation of the text in all the files, in the
order specified.

Each time you run @code{@value{AS}} it assembles exactly one source
program.  The source program is made up of one or more files.
(The standard input is also a file.)

You give @code{@value{AS}} a command line that has zero or more input file
names.  The input files are read (from left file name to right).  A
command line argument (in any position) that has no special meaning
is taken to be an input file name.

If you give @code{@value{AS}} no file names it attempts to read one input file
from the @code{@value{AS}} standard input, which is normally your terminal.  You
may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
to assemble.

Use @samp{--} if you need to explicitly name the standard input file
in your command line.

If the source is empty, @code{@value{AS}} produces a small, empty object
file.

@subheading Filenames and Line-numbers

@cindex input file linenumbers
@cindex line numbers, in input files
There are two ways of locating a line in the input file (or files) and
either may be used in reporting error messages.  One way refers to a line
number in a physical file; the other refers to a line number in a
``logical'' file.  @xref{Errors, ,Error and Warning Messages}.

@dfn{Physical files} are those files named in the command line given
to @code{@value{AS}}.

@dfn{Logical files} are simply names declared explicitly by assembler
directives; they bear no relation to physical files.  Logical file names help
error messages reflect the original source file, when @code{@value{AS}} source
is itself synthesized from other files.  @code{@value{AS}} understands the
@samp{#} directives emitted by the @code{@value{GCC}} preprocessor.  See also
@ref{File,,@code{.file}}.

@node Object
@section Output (Object) File

@cindex object file
@cindex output file
@kindex a.out
@kindex .o
Every time you run @code{@value{AS}} it produces an output file, which is
your assembly language program translated into numbers.  This file
is the object file.  Its default name is
@ifclear BOUT
@code{a.out}.
@end ifclear
@ifset BOUT
@ifset GENERIC
@code{a.out}, or 
@end ifset
@code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
@end ifset
You can give it another name by using the @code{-o} option.  Conventionally,
object file names end with @file{.o}.  The default name is used for historical
reasons: older assemblers were capable of assembling self-contained programs
directly into a runnable program.  (For some formats, this isn't currently
possible, but it can be done for the @code{a.out} format.)

@cindex linker
@kindex ld
The object file is meant for input to the linker @code{@value{LD}}.  It contains
assembled program code, information to help @code{@value{LD}} integrate
the assembled program into a runnable file, and (optionally) symbolic
information for the debugger.

@c link above to some info file(s) like the description of a.out.
@c don't forget to describe @sc{gnu} info as well as Unix lossage.

@node Errors
@section Error and Warning Messages

@cindex error messages
@cindex warning messages
@cindex messages from assembler
@code{@value{AS}} may write warnings and error messages to the standard error
file (usually your terminal).  This should not happen when  a compiler
runs @code{@value{AS}} automatically.  Warnings report an assumption made so
that @code{@value{AS}} could keep assembling a flawed program; errors report a
grave problem that stops the assembly.

@cindex format of warning messages
Warning messages have the format

@smallexample
file_name:@b{NNN}:Warning Message Text
@end smallexample

@noindent
@cindex line numbers, in warnings/errors
(where @b{NNN} is a line number).  If a logical file name has been given
(@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
the current input file is used.  If a logical line number was given
@ifset GENERIC
(@pxref{Line,,@code{.line}})
@end ifset
@ifclear GENERIC
@ifclear A29K
(@pxref{Line,,@code{.line}})
@end ifclear
@ifset A29K
(@pxref{Ln,,@code{.ln}})
@end ifset
@end ifclear
then it is used to calculate the number printed,
otherwise the actual line in the current source file is printed.  The
message text is intended to be self explanatory (in the grand Unix
tradition).

@cindex format of error messages
Error messages have the format
@smallexample
file_name:@b{NNN}:FATAL:Error Message Text
@end smallexample
The file name and line number are derived as for warning
messages.  The actual message text may be rather less explanatory
because many of them aren't supposed to happen.

@node Invoking
@chapter Command-Line Options

@cindex options, all versions of assembler
This chapter describes command-line options available in @emph{all}
versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
@ifclear GENERIC
to the @value{TARGET}.
@end ifclear
@ifset GENERIC
to particular machine architectures.
@end ifset

If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2),
you can use the @samp{-Wa} option to pass arguments through to the assembler.
The assembler arguments must be separated from each other (and the @samp{-Wa})
by commas.  For example:

@smallexample
gcc -c -g -O -Wa,-alh,-L file.c
@end smallexample

@noindent
This passes two options to the assembler: @samp{-alh} (emit a listing to
standard output with with high-level and assembly source) and @samp{-L} (retain
local symbols in the symbol table).

Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
command-line options are automatically passed to the assembler by the compiler.
(You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
precisely what options it passes to each compilation pass, including the
assembler.)

@menu
* a::             -a[cdhlns] enable listings
* D::             -D for compatibility
* f::             -f to work faster
* I::             -I for .include search path
@ifclear DIFF-TBL-KLUGE
* K::             -K for compatibility
@end ifclear
@ifset DIFF-TBL-KLUGE
* K::             -K for difference tables
@end ifset

* L::             -L to retain local labels
* M::		  -M or --mri to assemble in MRI compatibility mode
* MD::            --MD for dependency tracking
* o::             -o to name the object file
* R::             -R to join data and text sections
* statistics::    --statistics to see statistics about assembly
* traditional-format:: --traditional-format for compatible output
* v::             -v to announce version
* W::             -W, --no-warn, --warn, --fatal-warnings to control warnings
* Z::             -Z to make object file even after errors
@end menu

@node a
@section Enable Listings: @code{-a[cdhlns]}

@kindex -a
@kindex -ac
@kindex -ad
@kindex -ah
@kindex -al
@kindex -an
@kindex -as
@cindex listings, enabling
@cindex assembly listings, enabling

These options enable listing output from the assembler.  By itself,
@samp{-a} requests high-level, assembly, and symbols listing.
You can use other letters to select specific options for the list:
@samp{-ah} requests a high-level language listing,
@samp{-al} requests an output-program assembly listing, and
@samp{-as} requests a symbol table listing.
High-level listings require that a compiler debugging option like
@samp{-g} be used, and that assembly listings (@samp{-al}) be requested
also.

Use the @samp{-ac} option to omit false conditionals from a listing.  Any lines
which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
other conditional), or a true @code{.if} followed by an @code{.else}, will be
omitted from the listing.

Use the @samp{-ad} option to omit debugging directives from the
listing.

Once you have specified one of these options, you can further control
listing output and its appearance using the directives @code{.list},
@code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
@code{.sbttl}.
The @samp{-an} option turns off all forms processing.
If you do not request listing output with one of the @samp{-a} options, the