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study/Ref-docs/manual as/as_18.html
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<HTML>
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<HEAD>
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<!-- This HTML file has been created by texi2html 1.52
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from ../texi/as.texinfo on 24 April 1999 -->
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||||
|
||||
<TITLE>Using as - M680x0 Dependent Features</TITLE>
|
||||
</HEAD>
|
||||
<BODY>
|
||||
Go to the <A HREF="as_1.html">first</A>, <A HREF="as_17.html">previous</A>, <A HREF="as_19.html">next</A>, <A HREF="as_27.html">last</A> section, <A HREF="as_toc.html">table of contents</A>.
|
||||
<P><HR><P>
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||||
|
||||
|
||||
<H1><A NAME="SEC214" HREF="as_toc.html#TOC214">M680x0 Dependent Features</A></H1>
|
||||
|
||||
<P>
|
||||
<A NAME="IDX666"></A>
|
||||
|
||||
</P>
|
||||
|
||||
|
||||
<H2><A NAME="SEC215" HREF="as_toc.html#TOC215">M680x0 Options</A></H2>
|
||||
|
||||
<P>
|
||||
<A NAME="IDX667"></A>
|
||||
<A NAME="IDX668"></A>
|
||||
The Motorola 680x0 version of <CODE>as</CODE> has a few machine
|
||||
dependent options.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
<A NAME="IDX669"></A>
|
||||
You can use the <SAMP>`-l'</SAMP> option to shorten the size of references to undefined
|
||||
symbols. If you do not use the <SAMP>`-l'</SAMP> option, references to undefined
|
||||
symbols are wide enough for a full <CODE>long</CODE> (32 bits). (Since
|
||||
<CODE>as</CODE> cannot know where these symbols end up, <CODE>as</CODE> can
|
||||
only allocate space for the linker to fill in later. Since <CODE>as</CODE>
|
||||
does not know how far away these symbols are, it allocates as much space as it
|
||||
can.) If you use this option, the references are only one word wide (16 bits).
|
||||
This may be useful if you want the object file to be as small as possible, and
|
||||
you know that the relevant symbols are always less than 17 bits away.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
<A NAME="IDX670"></A>
|
||||
For some configurations, especially those where the compiler normally
|
||||
does not prepend an underscore to the names of user variables, the
|
||||
assembler requires a <SAMP>`%'</SAMP> before any use of a register name. This
|
||||
is intended to let the assembler distinguish between C variables and
|
||||
functions named <SAMP>`a0'</SAMP> through <SAMP>`a7'</SAMP>, and so on. The <SAMP>`%'</SAMP> is
|
||||
always accepted, but is not required for certain configurations, notably
|
||||
<SAMP>`sun3'</SAMP>. The <SAMP>`--register-prefix-optional'</SAMP> option may be used
|
||||
to permit omitting the <SAMP>`%'</SAMP> even for configurations for which it is
|
||||
normally required. If this is done, it will generally be impossible to
|
||||
refer to C variables and functions with the same names as register
|
||||
names.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
<A NAME="IDX671"></A>
|
||||
Normally the character <SAMP>`|'</SAMP> is treated as a comment character, which
|
||||
means that it can not be used in expressions. The <SAMP>`--bitwise-or'</SAMP>
|
||||
option turns <SAMP>`|'</SAMP> into a normal character. In this mode, you must
|
||||
either use C style comments, or start comments with a <SAMP>`#'</SAMP> character
|
||||
at the beginning of a line.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
<A NAME="IDX672"></A>
|
||||
<A NAME="IDX673"></A>
|
||||
If you use an addressing mode with a base register without specifying
|
||||
the size, <CODE>as</CODE> will normally use the full 32 bit value.
|
||||
For example, the addressing mode <SAMP>`%a0@(%d0)'</SAMP> is equivalent to
|
||||
<SAMP>`%a0@(%d0:l)'</SAMP>. You may use the <SAMP>`--base-size-default-16'</SAMP>
|
||||
option to tell <CODE>as</CODE> to default to using the 16 bit value.
|
||||
In this case, <SAMP>`%a0@(%d0)'</SAMP> is equivalent to <SAMP>`%a0@(%d0:w)'</SAMP>.
|
||||
You may use the <SAMP>`--base-size-default-32'</SAMP> option to restore the
|
||||
default behaviour.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
<A NAME="IDX674"></A>
|
||||
<A NAME="IDX675"></A>
|
||||
If you use an addressing mode with a displacement, and the value of the
|
||||
displacement is not known, <CODE>as</CODE> will normally assume that
|
||||
the value is 32 bits. For example, if the symbol <SAMP>`disp'</SAMP> has not
|
||||
been defined, <CODE>as</CODE> will assemble the addressing mode
|
||||
<SAMP>`%a0@(disp,%d0)'</SAMP> as though <SAMP>`disp'</SAMP> is a 32 bit value. You may
|
||||
use the <SAMP>`--disp-size-default-16'</SAMP> option to tell <CODE>as</CODE>
|
||||
to instead assume that the displacement is 16 bits. In this case,
|
||||
<CODE>as</CODE> will assemble <SAMP>`%a0@(disp,%d0)'</SAMP> as though
|
||||
<SAMP>`disp'</SAMP> is a 16 bit value. You may use the
|
||||
<SAMP>`--disp-size-default-32'</SAMP> option to restore the default behaviour.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
<A NAME="IDX676"></A>
|
||||
<A NAME="IDX677"></A>
|
||||
<A NAME="IDX678"></A>
|
||||
<CODE>as</CODE> can assemble code for several different members of the
|
||||
Motorola 680x0 family. The default depends upon how <CODE>as</CODE>
|
||||
was configured when it was built; normally, the default is to assemble
|
||||
code for the 68020 microprocessor. The following options may be used to
|
||||
change the default. These options control which instructions and
|
||||
addressing modes are permitted. The members of the 680x0 family are
|
||||
very similar. For detailed information about the differences, see the
|
||||
Motorola manuals.
|
||||
|
||||
</P>
|
||||
<DL COMPACT>
|
||||
|
||||
<DT><SAMP>`-m68000'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68ec000'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68hc000'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68hc001'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68008'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68302'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68306'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68307'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68322'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68356'</SAMP>
|
||||
<DD>
|
||||
Assemble for the 68000. <SAMP>`-m68008'</SAMP>, <SAMP>`-m68302'</SAMP>, and so on are synonyms
|
||||
for <SAMP>`-m68000'</SAMP>, since the chips are the same from the point of view
|
||||
of the assembler.
|
||||
|
||||
<DT><SAMP>`-m68010'</SAMP>
|
||||
<DD>
|
||||
Assemble for the 68010.
|
||||
|
||||
<DT><SAMP>`-m68020'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68ec020'</SAMP>
|
||||
<DD>
|
||||
Assemble for the 68020. This is normally the default.
|
||||
|
||||
<DT><SAMP>`-m68030'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68ec030'</SAMP>
|
||||
<DD>
|
||||
Assemble for the 68030.
|
||||
|
||||
<DT><SAMP>`-m68040'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68ec040'</SAMP>
|
||||
<DD>
|
||||
Assemble for the 68040.
|
||||
|
||||
<DT><SAMP>`-m68060'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68ec060'</SAMP>
|
||||
<DD>
|
||||
Assemble for the 68060.
|
||||
|
||||
<DT><SAMP>`-mcpu32'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68330'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68331'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68332'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68333'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68334'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68336'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68340'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68341'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68349'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68360'</SAMP>
|
||||
<DD>
|
||||
Assemble for the CPU32 family of chips.
|
||||
|
||||
<DT><SAMP>`-m5200'</SAMP>
|
||||
<DD>
|
||||
Assemble for the ColdFire family of chips.
|
||||
|
||||
<DT><SAMP>`-m68881'</SAMP>
|
||||
<DD>
|
||||
<DT><SAMP>`-m68882'</SAMP>
|
||||
<DD>
|
||||
Assemble 68881 floating point instructions. This is the default for the
|
||||
68020, 68030, and the CPU32. The 68040 and 68060 always support
|
||||
floating point instructions.
|
||||
|
||||
<DT><SAMP>`-mno-68881'</SAMP>
|
||||
<DD>
|
||||
Do not assemble 68881 floating point instructions. This is the default
|
||||
for 68000 and the 68010. The 68040 and 68060 always support floating
|
||||
point instructions, even if this option is used.
|
||||
|
||||
<DT><SAMP>`-m68851'</SAMP>
|
||||
<DD>
|
||||
Assemble 68851 MMU instructions. This is the default for the 68020,
|
||||
68030, and 68060. The 68040 accepts a somewhat different set of MMU
|
||||
instructions; <SAMP>`-m68851'</SAMP> and <SAMP>`-m68040'</SAMP> should not be used
|
||||
together.
|
||||
|
||||
<DT><SAMP>`-mno-68851'</SAMP>
|
||||
<DD>
|
||||
Do not assemble 68851 MMU instructions. This is the default for the
|
||||
68000, 68010, and the CPU32. The 68040 accepts a somewhat different set
|
||||
of MMU instructions.
|
||||
</DL>
|
||||
|
||||
|
||||
|
||||
<H2><A NAME="SEC216" HREF="as_toc.html#TOC216">Syntax</A></H2>
|
||||
|
||||
<P>
|
||||
<A NAME="IDX679"></A>
|
||||
This syntax for the Motorola 680x0 was developed at MIT.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
<A NAME="IDX680"></A>
|
||||
<A NAME="IDX681"></A>
|
||||
<A NAME="IDX682"></A>
|
||||
<A NAME="IDX683"></A>
|
||||
The 680x0 version of <CODE>as</CODE> uses instructions names and
|
||||
syntax compatible with the Sun assembler. Intervening periods are
|
||||
ignored; for example, <SAMP>`movl'</SAMP> is equivalent to <SAMP>`mov.l'</SAMP>.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
In the following table <VAR>apc</VAR> stands for any of the address registers
|
||||
(<SAMP>`%a0'</SAMP> through <SAMP>`%a7'</SAMP>), the program counter (<SAMP>`%pc'</SAMP>), the
|
||||
zero-address relative to the program counter (<SAMP>`%zpc'</SAMP>), a suppressed
|
||||
address register (<SAMP>`%za0'</SAMP> through <SAMP>`%za7'</SAMP>), or it may be omitted
|
||||
entirely. The use of <VAR>size</VAR> means one of <SAMP>`w'</SAMP> or <SAMP>`l'</SAMP>, and
|
||||
it may be omitted, along with the leading colon, unless a scale is also
|
||||
specified. The use of <VAR>scale</VAR> means one of <SAMP>`1'</SAMP>, <SAMP>`2'</SAMP>,
|
||||
<SAMP>`4'</SAMP>, or <SAMP>`8'</SAMP>, and it may always be omitted along with the
|
||||
leading colon.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
<A NAME="IDX684"></A>
|
||||
<A NAME="IDX685"></A>
|
||||
The following addressing modes are understood:
|
||||
<DL COMPACT>
|
||||
|
||||
<DT><EM>Immediate</EM>
|
||||
<DD>
|
||||
<SAMP>`#<VAR>number</VAR>'</SAMP>
|
||||
|
||||
<DT><EM>Data Register</EM>
|
||||
<DD>
|
||||
<SAMP>`%d0'</SAMP> through <SAMP>`%d7'</SAMP>
|
||||
|
||||
<DT><EM>Address Register</EM>
|
||||
<DD>
|
||||
<SAMP>`%a0'</SAMP> through <SAMP>`%a7'</SAMP><BR>
|
||||
<SAMP>`%a7'</SAMP> is also known as <SAMP>`%sp'</SAMP>, i.e. the Stack Pointer. <CODE>%a6</CODE>
|
||||
is also known as <SAMP>`%fp'</SAMP>, the Frame Pointer.
|
||||
|
||||
<DT><EM>Address Register Indirect</EM>
|
||||
<DD>
|
||||
<SAMP>`%a0@'</SAMP> through <SAMP>`%a7@'</SAMP>
|
||||
|
||||
<DT><EM>Address Register Postincrement</EM>
|
||||
<DD>
|
||||
<SAMP>`%a0@+'</SAMP> through <SAMP>`%a7@+'</SAMP>
|
||||
|
||||
<DT><EM>Address Register Predecrement</EM>
|
||||
<DD>
|
||||
<SAMP>`%a0@-'</SAMP> through <SAMP>`%a7@-'</SAMP>
|
||||
|
||||
<DT><EM>Indirect Plus Offset</EM>
|
||||
<DD>
|
||||
<SAMP>`<VAR>apc</VAR>@(<VAR>number</VAR>)'</SAMP>
|
||||
|
||||
<DT><EM>Index</EM>
|
||||
<DD>
|
||||
<SAMP>`<VAR>apc</VAR>@(<VAR>number</VAR>,<VAR>register</VAR>:<VAR>size</VAR>:<VAR>scale</VAR>)'</SAMP>
|
||||
|
||||
The <VAR>number</VAR> may be omitted.
|
||||
|
||||
<DT><EM>Postindex</EM>
|
||||
<DD>
|
||||
<SAMP>`<VAR>apc</VAR>@(<VAR>number</VAR>)@(<VAR>onumber</VAR>,<VAR>register</VAR>:<VAR>size</VAR>:<VAR>scale</VAR>)'</SAMP>
|
||||
|
||||
The <VAR>onumber</VAR> or the <VAR>register</VAR>, but not both, may be omitted.
|
||||
|
||||
<DT><EM>Preindex</EM>
|
||||
<DD>
|
||||
<SAMP>`<VAR>apc</VAR>@(<VAR>number</VAR>,<VAR>register</VAR>:<VAR>size</VAR>:<VAR>scale</VAR>)@(<VAR>onumber</VAR>)'</SAMP>
|
||||
|
||||
The <VAR>number</VAR> may be omitted. Omitting the <VAR>register</VAR> produces
|
||||
the Postindex addressing mode.
|
||||
|
||||
<DT><EM>Absolute</EM>
|
||||
<DD>
|
||||
<SAMP>`<VAR>symbol</VAR>'</SAMP>, or <SAMP>`<VAR>digits</VAR>'</SAMP>, optionally followed by
|
||||
<SAMP>`:b'</SAMP>, <SAMP>`:w'</SAMP>, or <SAMP>`:l'</SAMP>.
|
||||
</DL>
|
||||
|
||||
|
||||
|
||||
<H2><A NAME="SEC217" HREF="as_toc.html#TOC217">Motorola Syntax</A></H2>
|
||||
|
||||
<P>
|
||||
<A NAME="IDX686"></A>
|
||||
<A NAME="IDX687"></A>
|
||||
|
||||
</P>
|
||||
<P>
|
||||
The standard Motorola syntax for this chip differs from the syntax
|
||||
already discussed (see section <A HREF="as_18.html#SEC216">Syntax</A>). <CODE>as</CODE> can
|
||||
accept Motorola syntax for operands, even if MIT syntax is used for
|
||||
other operands in the same instruction. The two kinds of syntax are
|
||||
fully compatible.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
In the following table <VAR>apc</VAR> stands for any of the address registers
|
||||
(<SAMP>`%a0'</SAMP> through <SAMP>`%a7'</SAMP>), the program counter (<SAMP>`%pc'</SAMP>), the
|
||||
zero-address relative to the program counter (<SAMP>`%zpc'</SAMP>), or a
|
||||
suppressed address register (<SAMP>`%za0'</SAMP> through <SAMP>`%za7'</SAMP>). The use
|
||||
of <VAR>size</VAR> means one of <SAMP>`w'</SAMP> or <SAMP>`l'</SAMP>, and it may always be
|
||||
omitted along with the leading dot. The use of <VAR>scale</VAR> means one of
|
||||
<SAMP>`1'</SAMP>, <SAMP>`2'</SAMP>, <SAMP>`4'</SAMP>, or <SAMP>`8'</SAMP>, and it may always be omitted
|
||||
along with the leading asterisk.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
The following additional addressing modes are understood:
|
||||
|
||||
</P>
|
||||
<DL COMPACT>
|
||||
|
||||
<DT><EM>Address Register Indirect</EM>
|
||||
<DD>
|
||||
<SAMP>`(%a0)'</SAMP> through <SAMP>`(%a7)'</SAMP><BR>
|
||||
<SAMP>`%a7'</SAMP> is also known as <SAMP>`%sp'</SAMP>, i.e. the Stack Pointer. <CODE>%a6</CODE>
|
||||
is also known as <SAMP>`%fp'</SAMP>, the Frame Pointer.
|
||||
|
||||
<DT><EM>Address Register Postincrement</EM>
|
||||
<DD>
|
||||
<SAMP>`(%a0)+'</SAMP> through <SAMP>`(%a7)+'</SAMP>
|
||||
|
||||
<DT><EM>Address Register Predecrement</EM>
|
||||
<DD>
|
||||
<SAMP>`-(%a0)'</SAMP> through <SAMP>`-(%a7)'</SAMP>
|
||||
|
||||
<DT><EM>Indirect Plus Offset</EM>
|
||||
<DD>
|
||||
<SAMP>`<VAR>number</VAR>(<VAR>%a0</VAR>)'</SAMP> through <SAMP>`<VAR>number</VAR>(<VAR>%a7</VAR>)'</SAMP>,
|
||||
or <SAMP>`<VAR>number</VAR>(<VAR>%pc</VAR>)'</SAMP>.
|
||||
|
||||
The <VAR>number</VAR> may also appear within the parentheses, as in
|
||||
<SAMP>`(<VAR>number</VAR>,<VAR>%a0</VAR>)'</SAMP>. When used with the <VAR>pc</VAR>, the
|
||||
<VAR>number</VAR> may be omitted (with an address register, omitting the
|
||||
<VAR>number</VAR> produces Address Register Indirect mode).
|
||||
|
||||
<DT><EM>Index</EM>
|
||||
<DD>
|
||||
<SAMP>`<VAR>number</VAR>(<VAR>apc</VAR>,<VAR>register</VAR>.<VAR>size</VAR>*<VAR>scale</VAR>)'</SAMP>
|
||||
|
||||
The <VAR>number</VAR> may be omitted, or it may appear within the
|
||||
parentheses. The <VAR>apc</VAR> may be omitted. The <VAR>register</VAR> and the
|
||||
<VAR>apc</VAR> may appear in either order. If both <VAR>apc</VAR> and
|
||||
<VAR>register</VAR> are address registers, and the <VAR>size</VAR> and <VAR>scale</VAR>
|
||||
are omitted, then the first register is taken as the base register, and
|
||||
the second as the index register.
|
||||
|
||||
<DT><EM>Postindex</EM>
|
||||
<DD>
|
||||
<SAMP>`([<VAR>number</VAR>,<VAR>apc</VAR>],<VAR>register</VAR>.<VAR>size</VAR>*<VAR>scale</VAR>,<VAR>onumber</VAR>)'</SAMP>
|
||||
|
||||
The <VAR>onumber</VAR>, or the <VAR>register</VAR>, or both, may be omitted.
|
||||
Either the <VAR>number</VAR> or the <VAR>apc</VAR> may be omitted, but not both.
|
||||
|
||||
<DT><EM>Preindex</EM>
|
||||
<DD>
|
||||
<SAMP>`([<VAR>number</VAR>,<VAR>apc</VAR>,<VAR>register</VAR>.<VAR>size</VAR>*<VAR>scale</VAR>],<VAR>onumber</VAR>)'</SAMP>
|
||||
|
||||
The <VAR>number</VAR>, or the <VAR>apc</VAR>, or the <VAR>register</VAR>, or any two of
|
||||
them, may be omitted. The <VAR>onumber</VAR> may be omitted. The
|
||||
<VAR>register</VAR> and the <VAR>apc</VAR> may appear in either order. If both
|
||||
<VAR>apc</VAR> and <VAR>register</VAR> are address registers, and the <VAR>size</VAR>
|
||||
and <VAR>scale</VAR> are omitted, then the first register is taken as the
|
||||
base register, and the second as the index register.
|
||||
</DL>
|
||||
|
||||
|
||||
|
||||
<H2><A NAME="SEC218" HREF="as_toc.html#TOC218">Floating Point</A></H2>
|
||||
|
||||
<P>
|
||||
<A NAME="IDX688"></A>
|
||||
<A NAME="IDX689"></A>
|
||||
Packed decimal (P) format floating literals are not supported.
|
||||
Feel free to add the code!
|
||||
|
||||
</P>
|
||||
<P>
|
||||
The floating point formats generated by directives are these.
|
||||
|
||||
</P>
|
||||
<DL COMPACT>
|
||||
|
||||
<DT><CODE>.float</CODE>
|
||||
<DD>
|
||||
<A NAME="IDX690"></A>
|
||||
|
||||
<CODE>Single</CODE> precision floating point constants.
|
||||
|
||||
<A NAME="IDX691"></A>
|
||||
<DT><CODE>.double</CODE>
|
||||
<DD>
|
||||
<CODE>Double</CODE> precision floating point constants.
|
||||
|
||||
<A NAME="IDX692"></A>
|
||||
<A NAME="IDX693"></A>
|
||||
<DT><CODE>.extend</CODE>
|
||||
<DD>
|
||||
<DT><CODE>.ldouble</CODE>
|
||||
<DD>
|
||||
<CODE>Extended</CODE> precision (<CODE>long double</CODE>) floating point constants.
|
||||
</DL>
|
||||
|
||||
|
||||
|
||||
<H2><A NAME="SEC219" HREF="as_toc.html#TOC219">680x0 Machine Directives</A></H2>
|
||||
|
||||
<P>
|
||||
<A NAME="IDX694"></A>
|
||||
<A NAME="IDX695"></A>
|
||||
In order to be compatible with the Sun assembler the 680x0 assembler
|
||||
understands the following directives.
|
||||
|
||||
</P>
|
||||
<DL COMPACT>
|
||||
|
||||
<DT><CODE>.data1</CODE>
|
||||
<DD>
|
||||
<A NAME="IDX696"></A>
|
||||
|
||||
This directive is identical to a <CODE>.data 1</CODE> directive.
|
||||
|
||||
<A NAME="IDX697"></A>
|
||||
<DT><CODE>.data2</CODE>
|
||||
<DD>
|
||||
This directive is identical to a <CODE>.data 2</CODE> directive.
|
||||
|
||||
<A NAME="IDX698"></A>
|
||||
<DT><CODE>.even</CODE>
|
||||
<DD>
|
||||
This directive is a special case of the <CODE>.align</CODE> directive; it
|
||||
aligns the output to an even byte boundary.
|
||||
|
||||
<A NAME="IDX699"></A>
|
||||
<DT><CODE>.skip</CODE>
|
||||
<DD>
|
||||
This directive is identical to a <CODE>.space</CODE> directive.
|
||||
</DL>
|
||||
|
||||
|
||||
|
||||
<H2><A NAME="SEC220" HREF="as_toc.html#TOC220">Opcodes</A></H2>
|
||||
|
||||
<P>
|
||||
<A NAME="IDX700"></A>
|
||||
<A NAME="IDX701"></A>
|
||||
<A NAME="IDX702"></A>
|
||||
|
||||
</P>
|
||||
|
||||
|
||||
|
||||
<H3><A NAME="SEC221" HREF="as_toc.html#TOC221">Branch Improvement</A></H3>
|
||||
|
||||
<P>
|
||||
<A NAME="IDX703"></A>
|
||||
<A NAME="IDX704"></A>
|
||||
<A NAME="IDX705"></A>
|
||||
<A NAME="IDX706"></A>
|
||||
Certain pseudo opcodes are permitted for branch instructions.
|
||||
They expand to the shortest branch instruction that reach the
|
||||
target. Generally these mnemonics are made by substituting <SAMP>`j'</SAMP> for
|
||||
<SAMP>`b'</SAMP> at the start of a Motorola mnemonic.
|
||||
|
||||
</P>
|
||||
<P>
|
||||
The following table summarizes the pseudo-operations. A <CODE>*</CODE> flags
|
||||
cases that are more fully described after the table:
|
||||
|
||||
</P>
|
||||
|
||||
<PRE>
|
||||
Displacement
|
||||
+-------------------------------------------------
|
||||
| 68020 68000/10
|
||||
Pseudo-Op |BYTE WORD LONG LONG non-PC relative
|
||||
+-------------------------------------------------
|
||||
jbsr |bsrs bsr bsrl jsr jsr
|
||||
jra |bras bra bral jmp jmp
|
||||
* jXX |bXXs bXX bXXl bNXs;jmpl bNXs;jmp
|
||||
* dbXX |dbXX dbXX dbXX; bra; jmpl
|
||||
* fjXX |fbXXw fbXXw fbXXl fbNXw;jmp
|
||||
|
||||
XX: condition
|
||||
NX: negative of condition XX
|
||||
|
||||
</PRE>
|
||||
|
||||
<P>
|
||||
<CODE>*</CODE>---see full description below
|
||||
|
||||
</P>
|
||||
<DL COMPACT>
|
||||
|
||||
<DT><CODE>jbsr</CODE>
|
||||
<DD>
|
||||
<DT><CODE>jra</CODE>
|
||||
<DD>
|
||||
These are the simplest jump pseudo-operations; they always map to one
|
||||
particular machine instruction, depending on the displacement to the
|
||||
branch target.
|
||||
|
||||
<DT><CODE>j<VAR>XX</VAR></CODE>
|
||||
<DD>
|
||||
Here, <SAMP>`j<VAR>XX</VAR>'</SAMP> stands for an entire family of pseudo-operations,
|
||||
where <VAR>XX</VAR> is a conditional branch or condition-code test. The full
|
||||
list of pseudo-ops in this family is:
|
||||
|
||||
<PRE>
|
||||
jhi jls jcc jcs jne jeq jvc
|
||||
jvs jpl jmi jge jlt jgt jle
|
||||
</PRE>
|
||||
|
||||
For the cases of non-PC relative displacements and long displacements on
|
||||
the 68000 or 68010, <CODE>as</CODE> issues a longer code fragment in terms of
|
||||
<VAR>NX</VAR>, the opposite condition to <VAR>XX</VAR>. For example, for the
|
||||
non-PC relative case:
|
||||
|
||||
<PRE>
|
||||
j<VAR>XX</VAR> foo
|
||||
</PRE>
|
||||
|
||||
gives
|
||||
|
||||
<PRE>
|
||||
b<VAR>NX</VAR>s oof
|
||||
jmp foo
|
||||
oof:
|
||||
</PRE>
|
||||
|
||||
<DT><CODE>db<VAR>XX</VAR></CODE>
|
||||
<DD>
|
||||
The full family of pseudo-operations covered here is
|
||||
|
||||
<PRE>
|
||||
dbhi dbls dbcc dbcs dbne dbeq dbvc
|
||||
dbvs dbpl dbmi dbge dblt dbgt dble
|
||||
dbf dbra dbt
|
||||
</PRE>
|
||||
|
||||
Other than for word and byte displacements, when the source reads
|
||||
<SAMP>`db<VAR>XX</VAR> foo'</SAMP>, <CODE>as</CODE> emits
|
||||
|
||||
<PRE>
|
||||
db<VAR>XX</VAR> oo1
|
||||
bra oo2
|
||||
oo1:jmpl foo
|
||||
oo2:
|
||||
</PRE>
|
||||
|
||||
<DT><CODE>fj<VAR>XX</VAR></CODE>
|
||||
<DD>
|
||||
This family includes
|
||||
|
||||
<PRE>
|
||||
fjne fjeq fjge fjlt fjgt fjle fjf
|
||||
fjt fjgl fjgle fjnge fjngl fjngle fjngt
|
||||
fjnle fjnlt fjoge fjogl fjogt fjole fjolt
|
||||
fjor fjseq fjsf fjsne fjst fjueq fjuge
|
||||
fjugt fjule fjult fjun
|
||||
</PRE>
|
||||
|
||||
For branch targets that are not PC relative, <CODE>as</CODE> emits
|
||||
|
||||
<PRE>
|
||||
fb<VAR>NX</VAR> oof
|
||||
jmp foo
|
||||
oof:
|
||||
</PRE>
|
||||
|
||||
when it encounters <SAMP>`fj<VAR>XX</VAR> foo'</SAMP>.
|
||||
|
||||
</DL>
|
||||
|
||||
|
||||
|
||||
<H3><A NAME="SEC222" HREF="as_toc.html#TOC222">Special Characters</A></H3>
|
||||
|
||||
<P>
|
||||
<A NAME="IDX707"></A>
|
||||
<A NAME="IDX708"></A>
|
||||
<A NAME="IDX709"></A>
|
||||
<A NAME="IDX710"></A>
|
||||
<A NAME="IDX711"></A>
|
||||
<A NAME="IDX712"></A>
|
||||
The immediate character is <SAMP>`#'</SAMP> for Sun compatibility. The
|
||||
line-comment character is <SAMP>`|'</SAMP> (unless the <SAMP>`--bitwise-or'</SAMP>
|
||||
option is used). If a <SAMP>`#'</SAMP> appears at the beginning of a line, it
|
||||
is treated as a comment unless it looks like <SAMP>`# line file'</SAMP>, in
|
||||
which case it is treated normally.
|
||||
|
||||
</P>
|
||||
|
||||
<P><HR><P>
|
||||
Go to the <A HREF="as_1.html">first</A>, <A HREF="as_17.html">previous</A>, <A HREF="as_19.html">next</A>, <A HREF="as_27.html">last</A> section, <A HREF="as_toc.html">table of contents</A>.
|
||||
</BODY>
|
||||
</HTML>
|
||||
Reference in New Issue
Block a user