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<a name="Instruction-Output"></a>
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<hr>
<a name="Output-of-Assembler-Instructions"></a>
<h4 class="subsection">18.20.7 Output of Assembler Instructions</h4>

<p>This describes assembler instruction output.
</p>
<dl>
<dt><a name="index-REGISTER_005fNAMES"></a>Macro: <strong>REGISTER_NAMES</strong></dt>
<dd><p>A C initializer containing the assembler&rsquo;s names for the machine
registers, each one as a C string constant.  This is what translates
register numbers in the compiler into assembler language.
</p></dd></dl>

<dl>
<dt><a name="index-ADDITIONAL_005fREGISTER_005fNAMES"></a>Macro: <strong>ADDITIONAL_REGISTER_NAMES</strong></dt>
<dd><p>If defined, a C initializer for an array of structures containing a name
and a register number.  This macro defines additional names for hard
registers, thus allowing the <code>asm</code> option in declarations to refer
to registers using alternate names.
</p></dd></dl>

<dl>
<dt><a name="index-OVERLAPPING_005fREGISTER_005fNAMES"></a>Macro: <strong>OVERLAPPING_REGISTER_NAMES</strong></dt>
<dd><p>If defined, a C initializer for an array of structures containing a
name, a register number and a count of the number of consecutive
machine registers the name overlaps.  This macro defines additional
names for hard registers, thus allowing the <code>asm</code> option in
declarations to refer to registers using alternate names.  Unlike
<code>ADDITIONAL_REGISTER_NAMES</code>, this macro should be used when the
register name implies multiple underlying registers.
</p>
<p>This macro should be used when it is important that a clobber in an
<code>asm</code> statement clobbers all the underlying values implied by the
register name.  For example, on ARM, clobbering the double-precision
VFP register &ldquo;d0&rdquo; implies clobbering both single-precision registers
&ldquo;s0&rdquo; and &ldquo;s1&rdquo;.
</p></dd></dl>

<dl>
<dt><a name="index-ASM_005fOUTPUT_005fOPCODE"></a>Macro: <strong>ASM_OUTPUT_OPCODE</strong> <em>(<var>stream</var>, <var>ptr</var>)</em></dt>
<dd><p>Define this macro if you are using an unusual assembler that
requires different names for the machine instructions.
</p>
<p>The definition is a C statement or statements which output an
assembler instruction opcode to the stdio stream <var>stream</var>.  The
macro-operand <var>ptr</var> is a variable of type <code>char *</code> which
points to the opcode name in its &ldquo;internal&rdquo; form&mdash;the form that is
written in the machine description.  The definition should output the
opcode name to <var>stream</var>, performing any translation you desire, and
increment the variable <var>ptr</var> to point at the end of the opcode
so that it will not be output twice.
</p>
<p>In fact, your macro definition may process less than the entire opcode
name, or more than the opcode name; but if you want to process text
that includes &lsquo;<samp>%</samp>&rsquo;-sequences to substitute operands, you must take
care of the substitution yourself.  Just be sure to increment
<var>ptr</var> over whatever text should not be output normally.
</p>
<a name="index-recog_005fdata_002eoperand"></a>
<p>If you need to look at the operand values, they can be found as the
elements of <code>recog_data.operand</code>.
</p>
<p>If the macro definition does nothing, the instruction is output
in the usual way.
</p></dd></dl>

<dl>
<dt><a name="index-FINAL_005fPRESCAN_005fINSN"></a>Macro: <strong>FINAL_PRESCAN_INSN</strong> <em>(<var>insn</var>, <var>opvec</var>, <var>noperands</var>)</em></dt>
<dd><p>If defined, a C statement to be executed just prior to the output of
assembler code for <var>insn</var>, to modify the extracted operands so
they will be output differently.
</p>
<p>Here the argument <var>opvec</var> is the vector containing the operands
extracted from <var>insn</var>, and <var>noperands</var> is the number of
elements of the vector which contain meaningful data for this insn.
The contents of this vector are what will be used to convert the insn
template into assembler code, so you can change the assembler output
by changing the contents of the vector.
</p>
<p>This macro is useful when various assembler syntaxes share a single
file of instruction patterns; by defining this macro differently, you
can cause a large class of instructions to be output differently (such
as with rearranged operands).  Naturally, variations in assembler
syntax affecting individual insn patterns ought to be handled by
writing conditional output routines in those patterns.
</p>
<p>If this macro is not defined, it is equivalent to a null statement.
</p></dd></dl>

<dl>
<dt><a name="index-TARGET_005fASM_005fFINAL_005fPOSTSCAN_005fINSN"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_FINAL_POSTSCAN_INSN</strong> <em>(FILE *<var>file</var>, rtx_insn *<var>insn</var>, rtx *<var>opvec</var>, int <var>noperands</var>)</em></dt>
<dd><p>If defined, this target hook is a function which is executed just after the
output of assembler code for <var>insn</var>, to change the mode of the assembler
if necessary.
</p>
<p>Here the argument <var>opvec</var> is the vector containing the operands
extracted from <var>insn</var>, and <var>noperands</var> is the number of
elements of the vector which contain meaningful data for this insn.
The contents of this vector are what was used to convert the insn
template into assembler code, so you can change the assembler mode
by checking the contents of the vector.
</p></dd></dl>

<dl>
<dt><a name="index-PRINT_005fOPERAND"></a>Macro: <strong>PRINT_OPERAND</strong> <em>(<var>stream</var>, <var>x</var>, <var>code</var>)</em></dt>
<dd><p>A C compound statement to output to stdio stream <var>stream</var> the
assembler syntax for an instruction operand <var>x</var>.  <var>x</var> is an
RTL expression.
</p>
<p><var>code</var> is a value that can be used to specify one of several ways
of printing the operand.  It is used when identical operands must be
printed differently depending on the context.  <var>code</var> comes from
the &lsquo;<samp>%</samp>&rsquo; specification that was used to request printing of the
operand.  If the specification was just &lsquo;<samp>%<var>digit</var></samp>&rsquo; then
<var>code</var> is 0; if the specification was &lsquo;<samp>%<var>ltr</var>
<var>digit</var></samp>&rsquo; then <var>code</var> is the ASCII code for <var>ltr</var>.
</p>
<a name="index-reg_005fnames-1"></a>
<p>If <var>x</var> is a register, this macro should print the register&rsquo;s name.
The names can be found in an array <code>reg_names</code> whose type is
<code>char *[]</code>.  <code>reg_names</code> is initialized from
<code>REGISTER_NAMES</code>.
</p>
<p>When the machine description has a specification &lsquo;<samp>%<var>punct</var></samp>&rsquo;
(a &lsquo;<samp>%</samp>&rsquo; followed by a punctuation character), this macro is called
with a null pointer for <var>x</var> and the punctuation character for
<var>code</var>.
</p></dd></dl>

<dl>
<dt><a name="index-PRINT_005fOPERAND_005fPUNCT_005fVALID_005fP"></a>Macro: <strong>PRINT_OPERAND_PUNCT_VALID_P</strong> <em>(<var>code</var>)</em></dt>
<dd><p>A C expression which evaluates to true if <var>code</var> is a valid
punctuation character for use in the <code>PRINT_OPERAND</code> macro.  If
<code>PRINT_OPERAND_PUNCT_VALID_P</code> is not defined, it means that no
punctuation characters (except for the standard one, &lsquo;<samp>%</samp>&rsquo;) are used
in this way.
</p></dd></dl>

<dl>
<dt><a name="index-PRINT_005fOPERAND_005fADDRESS"></a>Macro: <strong>PRINT_OPERAND_ADDRESS</strong> <em>(<var>stream</var>, <var>x</var>)</em></dt>
<dd><p>A C compound statement to output to stdio stream <var>stream</var> the
assembler syntax for an instruction operand that is a memory reference
whose address is <var>x</var>.  <var>x</var> is an RTL expression.
</p>
<a name="index-TARGET_005fENCODE_005fSECTION_005fINFO-usage"></a>
<p>On some machines, the syntax for a symbolic address depends on the
section that the address refers to.  On these machines, define the hook
<code>TARGET_ENCODE_SECTION_INFO</code> to store the information into the
<code>symbol_ref</code>, and then check for it here.  See <a href="Assembler-Format.html#Assembler-Format">Assembler Format</a>.
</p></dd></dl>

<a name="index-dbr_005fsequence_005flength"></a>
<dl>
<dt><a name="index-DBR_005fOUTPUT_005fSEQEND"></a>Macro: <strong>DBR_OUTPUT_SEQEND</strong> <em>(<var>file</var>)</em></dt>
<dd><p>A C statement, to be executed after all slot-filler instructions have
been output.  If necessary, call <code>dbr_sequence_length</code> to
determine the number of slots filled in a sequence (zero if not
currently outputting a sequence), to decide how many no-ops to output,
or whatever.
</p>
<p>Don&rsquo;t define this macro if it has nothing to do, but it is helpful in
reading assembly output if the extent of the delay sequence is made
explicit (e.g. with white space).
</p></dd></dl>

<a name="index-final_005fsequence"></a>
<p>Note that output routines for instructions with delay slots must be
prepared to deal with not being output as part of a sequence
(i.e. when the scheduling pass is not run, or when no slot fillers could be
found.)  The variable <code>final_sequence</code> is null when not
processing a sequence, otherwise it contains the <code>sequence</code> rtx
being output.
</p>
<a name="index-asm_005ffprintf"></a>
<dl>
<dt><a name="index-REGISTER_005fPREFIX"></a>Macro: <strong>REGISTER_PREFIX</strong></dt>
<dt><a name="index-LOCAL_005fLABEL_005fPREFIX"></a>Macro: <strong>LOCAL_LABEL_PREFIX</strong></dt>
<dt><a name="index-USER_005fLABEL_005fPREFIX"></a>Macro: <strong>USER_LABEL_PREFIX</strong></dt>
<dt><a name="index-IMMEDIATE_005fPREFIX"></a>Macro: <strong>IMMEDIATE_PREFIX</strong></dt>
<dd><p>If defined, C string expressions to be used for the &lsquo;<samp>%R</samp>&rsquo;, &lsquo;<samp>%L</samp>&rsquo;,
&lsquo;<samp>%U</samp>&rsquo;, and &lsquo;<samp>%I</samp>&rsquo; options of <code>asm_fprintf</code> (see
<samp>final.c</samp>).  These are useful when a single <samp>md</samp> file must
support multiple assembler formats.  In that case, the various <samp>tm.h</samp>
files can define these macros differently.
</p></dd></dl>

<dl>
<dt><a name="index-ASM_005fFPRINTF_005fEXTENSIONS"></a>Macro: <strong>ASM_FPRINTF_EXTENSIONS</strong> <em>(<var>file</var>, <var>argptr</var>, <var>format</var>)</em></dt>
<dd><p>If defined this macro should expand to a series of <code>case</code>
statements which will be parsed inside the <code>switch</code> statement of
the <code>asm_fprintf</code> function.  This allows targets to define extra
printf formats which may useful when generating their assembler
statements.  Note that uppercase letters are reserved for future
generic extensions to asm_fprintf, and so are not available to target
specific code.  The output file is given by the parameter <var>file</var>.
The varargs input pointer is <var>argptr</var> and the rest of the format
string, starting the character after the one that is being switched
upon, is pointed to by <var>format</var>.
</p></dd></dl>

<dl>
<dt><a name="index-ASSEMBLER_005fDIALECT"></a>Macro: <strong>ASSEMBLER_DIALECT</strong></dt>
<dd><p>If your target supports multiple dialects of assembler language (such as
different opcodes), define this macro as a C expression that gives the
numeric index of the assembler language dialect to use, with zero as the
first variant.
</p>
<p>If this macro is defined, you may use constructs of the form
</p><div class="smallexample">
<pre class="smallexample">&lsquo;<samp>{option0|option1|option2&hellip;}</samp>&rsquo;
</pre></div>
<p>in the output templates of patterns (see <a href="Output-Template.html#Output-Template">Output Template</a>) or in the
first argument of <code>asm_fprintf</code>.  This construct outputs
&lsquo;<samp>option0</samp>&rsquo;, &lsquo;<samp>option1</samp>&rsquo;, &lsquo;<samp>option2</samp>&rsquo;, etc., if the value of
<code>ASSEMBLER_DIALECT</code> is zero, one, two, etc.  Any special characters
within these strings retain their usual meaning.  If there are fewer
alternatives within the braces than the value of
<code>ASSEMBLER_DIALECT</code>, the construct outputs nothing. If it&rsquo;s needed
to print curly braces or &lsquo;<samp>|</samp>&rsquo; character in assembler output directly,
&lsquo;<samp>%{</samp>&rsquo;, &lsquo;<samp>%}</samp>&rsquo; and &lsquo;<samp>%|</samp>&rsquo; can be used.
</p>
<p>If you do not define this macro, the characters &lsquo;<samp>{</samp>&rsquo;, &lsquo;<samp>|</samp>&rsquo; and
&lsquo;<samp>}</samp>&rsquo; do not have any special meaning when used in templates or
operands to <code>asm_fprintf</code>.
</p>
<p>Define the macros <code>REGISTER_PREFIX</code>, <code>LOCAL_LABEL_PREFIX</code>,
<code>USER_LABEL_PREFIX</code> and <code>IMMEDIATE_PREFIX</code> if you can express
the variations in assembler language syntax with that mechanism.  Define
<code>ASSEMBLER_DIALECT</code> and use the &lsquo;<samp>{option0|option1}</samp>&rsquo; syntax
if the syntax variant are larger and involve such things as different
opcodes or operand order.
</p></dd></dl>

<dl>
<dt><a name="index-ASM_005fOUTPUT_005fREG_005fPUSH"></a>Macro: <strong>ASM_OUTPUT_REG_PUSH</strong> <em>(<var>stream</var>, <var>regno</var>)</em></dt>
<dd><p>A C expression to output to <var>stream</var> some assembler code
which will push hard register number <var>regno</var> onto the stack.
The code need not be optimal, since this macro is used only when
profiling.
</p></dd></dl>

<dl>
<dt><a name="index-ASM_005fOUTPUT_005fREG_005fPOP"></a>Macro: <strong>ASM_OUTPUT_REG_POP</strong> <em>(<var>stream</var>, <var>regno</var>)</em></dt>
<dd><p>A C expression to output to <var>stream</var> some assembler code
which will pop hard register number <var>regno</var> off of the stack.
The code need not be optimal, since this macro is used only when
profiling.
</p></dd></dl>

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