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 <a name="Old-Constraints"></a>
 <div class="header">
 <p>
 Next: <a href="Stack-and-Calling.html#Stack-and-Calling" accesskey="n" rel="next">Stack and Calling</a>, Previous: <a href="Register-Classes.html#Register-Classes" accesskey="p" rel="prev">Register Classes</a>, Up: <a href="Target-Macros.html#Target-Macros" accesskey="u" rel="up">Target Macros</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
 </div>
 <hr>
 <a name="Obsolete-Macros-for-Defining-Constraints"></a>
 <h3 class="section">17.9 Obsolete Macros for Defining Constraints</h3>
 <a name="index-defining-constraints_002c-obsolete-method"></a>
 <a name="index-constraints_002c-defining_002c-obsolete-method"></a>

 <p>Machine-specific constraints can be defined with these macros instead
 of the machine description constructs described in <a href="Define-Constraints.html#Define-Constraints">Define Constraints</a>.  This mechanism is obsolete.  New ports should not use
 it; old ports should convert to the new mechanism.
 </p>
 <dl>
 <dt><a name="index-CONSTRAINT_005fLEN"></a>Macro: <strong>CONSTRAINT_LEN</strong> <em>(<var>char</var>, <var>str</var>)</em></dt>
 <dd><p>For the constraint at the start of <var>str</var>, which starts with the letter
 <var>c</var>, return the length.  This allows you to have register class /
 constant / extra constraints that are longer than a single letter;
 you don&rsquo;t need to define this macro if you can do with single-letter
 constraints only.  The definition of this macro should use
 DEFAULT_CONSTRAINT_LEN for all the characters that you don&rsquo;t want
 to handle specially.
 There are some sanity checks in genoutput.c that check the constraint lengths
 for the md file, so you can also use this macro to help you while you are
 transitioning from a byzantine single-letter-constraint scheme: when you
 return a negative length for a constraint you want to re-use, genoutput
 will complain about every instance where it is used in the md file.
 </p></dd></dl>

 <dl>
 <dt><a name="index-REG_005fCLASS_005fFROM_005fLETTER"></a>Macro: <strong>REG_CLASS_FROM_LETTER</strong> <em>(<var>char</var>)</em></dt>
 <dd><p>A C expression which defines the machine-dependent operand constraint
 letters for register classes.  If <var>char</var> is such a letter, the
 value should be the register class corresponding to it.  Otherwise,
 the value should be <code>NO_REGS</code>.  The register letter &lsquo;<samp>r</samp>&rsquo;,
 corresponding to class <code>GENERAL_REGS</code>, will not be passed
 to this macro; you do not need to handle it.
 </p></dd></dl>

 <dl>
 <dt><a name="index-REG_005fCLASS_005fFROM_005fCONSTRAINT"></a>Macro: <strong>REG_CLASS_FROM_CONSTRAINT</strong> <em>(<var>char</var>, <var>str</var>)</em></dt>
 <dd><p>Like <code>REG_CLASS_FROM_LETTER</code>, but you also get the constraint string
 passed in <var>str</var>, so that you can use suffixes to distinguish between
 different variants.
 </p></dd></dl>

 <dl>
 <dt><a name="index-CONST_005fOK_005fFOR_005fLETTER_005fP"></a>Macro: <strong>CONST_OK_FOR_LETTER_P</strong> <em>(<var>value</var>, <var>c</var>)</em></dt>
 <dd><p>A C expression that defines the machine-dependent operand constraint
 letters (&lsquo;<samp>I</samp>&rsquo;, &lsquo;<samp>J</samp>&rsquo;, &lsquo;<samp>K</samp>&rsquo;, &hellip; &lsquo;<samp>P</samp>&rsquo;) that specify
 particular ranges of integer values.  If <var>c</var> is one of those
 letters, the expression should check that <var>value</var>, an integer, is in
 the appropriate range and return 1 if so, 0 otherwise.  If <var>c</var> is
 not one of those letters, the value should be 0 regardless of
 <var>value</var>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-CONST_005fOK_005fFOR_005fCONSTRAINT_005fP"></a>Macro: <strong>CONST_OK_FOR_CONSTRAINT_P</strong> <em>(<var>value</var>, <var>c</var>, <var>str</var>)</em></dt>
 <dd><p>Like <code>CONST_OK_FOR_LETTER_P</code>, but you also get the constraint
 string passed in <var>str</var>, so that you can use suffixes to distinguish
 between different variants.
 </p></dd></dl>

 <dl>
 <dt><a name="index-CONST_005fDOUBLE_005fOK_005fFOR_005fLETTER_005fP"></a>Macro: <strong>CONST_DOUBLE_OK_FOR_LETTER_P</strong> <em>(<var>value</var>, <var>c</var>)</em></dt>
 <dd><p>A C expression that defines the machine-dependent operand constraint
 letters that specify particular ranges of <code>const_double</code> values
 (&lsquo;<samp>G</samp>&rsquo; or &lsquo;<samp>H</samp>&rsquo;).
 </p>
 <p>If <var>c</var> is one of those letters, the expression should check that
 <var>value</var>, an RTX of code <code>const_double</code>, is in the appropriate
 range and return 1 if so, 0 otherwise.  If <var>c</var> is not one of those
 letters, the value should be 0 regardless of <var>value</var>.
 </p>
 <p><code>const_double</code> is used for all floating-point constants and for
 <code>DImode</code> fixed-point constants.  A given letter can accept either
 or both kinds of values.  It can use <code>GET_MODE</code> to distinguish
 between these kinds.
 </p></dd></dl>

 <dl>
 <dt><a name="index-CONST_005fDOUBLE_005fOK_005fFOR_005fCONSTRAINT_005fP"></a>Macro: <strong>CONST_DOUBLE_OK_FOR_CONSTRAINT_P</strong> <em>(<var>value</var>, <var>c</var>, <var>str</var>)</em></dt>
 <dd><p>Like <code>CONST_DOUBLE_OK_FOR_LETTER_P</code>, but you also get the constraint
 string passed in <var>str</var>, so that you can use suffixes to distinguish
 between different variants.
 </p></dd></dl>

 <dl>
 <dt><a name="index-EXTRA_005fCONSTRAINT"></a>Macro: <strong>EXTRA_CONSTRAINT</strong> <em>(<var>value</var>, <var>c</var>)</em></dt>
 <dd><p>A C expression that defines the optional machine-dependent constraint
 letters that can be used to segregate specific types of operands, usually
 memory references, for the target machine.  Any letter that is not
 elsewhere defined and not matched by <code>REG_CLASS_FROM_LETTER</code> /
 <code>REG_CLASS_FROM_CONSTRAINT</code>
 may be used.  Normally this macro will not be defined.
 </p>
 <p>If it is required for a particular target machine, it should return 1
 if <var>value</var> corresponds to the operand type represented by the
 constraint letter <var>c</var>.  If <var>c</var> is not defined as an extra
 constraint, the value returned should be 0 regardless of <var>value</var>.
 </p>
 <p>For example, on the ROMP, load instructions cannot have their output
 in r0 if the memory reference contains a symbolic address.  Constraint
 letter &lsquo;<samp>Q</samp>&rsquo; is defined as representing a memory address that does
 <em>not</em> contain a symbolic address.  An alternative is specified with
 a &lsquo;<samp>Q</samp>&rsquo; constraint on the input and &lsquo;<samp>r</samp>&rsquo; on the output.  The next
 alternative specifies &lsquo;<samp>m</samp>&rsquo; on the input and a register class that
 does not include r0 on the output.
 </p></dd></dl>

 <dl>
 <dt><a name="index-EXTRA_005fCONSTRAINT_005fSTR"></a>Macro: <strong>EXTRA_CONSTRAINT_STR</strong> <em>(<var>value</var>, <var>c</var>, <var>str</var>)</em></dt>
 <dd><p>Like <code>EXTRA_CONSTRAINT</code>, but you also get the constraint string passed
 in <var>str</var>, so that you can use suffixes to distinguish between different
 variants.
 </p></dd></dl>

 <dl>
 <dt><a name="index-EXTRA_005fMEMORY_005fCONSTRAINT"></a>Macro: <strong>EXTRA_MEMORY_CONSTRAINT</strong> <em>(<var>c</var>, <var>str</var>)</em></dt>
 <dd><p>A C expression that defines the optional machine-dependent constraint
 letters, amongst those accepted by <code>EXTRA_CONSTRAINT</code>, that should
 be treated like memory constraints by the reload pass.
 </p>
 <p>It should return 1 if the operand type represented by the constraint
 at the start of <var>str</var>, the first letter of which is the letter <var>c</var>,
 comprises a subset of all memory references including
 all those whose address is simply a base register.  This allows the reload
 pass to reload an operand, if it does not directly correspond to the operand
 type of <var>c</var>, by copying its address into a base register.
 </p>
 <p>For example, on the S/390, some instructions do not accept arbitrary
 memory references, but only those that do not make use of an index
 register.  The constraint letter &lsquo;<samp>Q</samp>&rsquo; is defined via
 <code>EXTRA_CONSTRAINT</code> as representing a memory address of this type.
 If the letter &lsquo;<samp>Q</samp>&rsquo; is marked as <code>EXTRA_MEMORY_CONSTRAINT</code>,
 a &lsquo;<samp>Q</samp>&rsquo; constraint can handle any memory operand, because the
 reload pass knows it can be reloaded by copying the memory address
 into a base register if required.  This is analogous to the way
 an &lsquo;<samp>o</samp>&rsquo; constraint can handle any memory operand.
 </p></dd></dl>

 <dl>
 <dt><a name="index-EXTRA_005fADDRESS_005fCONSTRAINT"></a>Macro: <strong>EXTRA_ADDRESS_CONSTRAINT</strong> <em>(<var>c</var>, <var>str</var>)</em></dt>
 <dd><p>A C expression that defines the optional machine-dependent constraint
 letters, amongst those accepted by <code>EXTRA_CONSTRAINT</code> /
 <code>EXTRA_CONSTRAINT_STR</code>, that should
 be treated like address constraints by the reload pass.
 </p>
 <p>It should return 1 if the operand type represented by the constraint
 at the start of <var>str</var>, which starts with the letter <var>c</var>, comprises
 a subset of all memory addresses including
 all those that consist of just a base register.  This allows the reload
 pass to reload an operand, if it does not directly correspond to the operand
 type of <var>str</var>, by copying it into a base register.
 </p>
 <p>Any constraint marked as <code>EXTRA_ADDRESS_CONSTRAINT</code> can only
 be used with the <code>address_operand</code> predicate.  It is treated
 analogously to the &lsquo;<samp>p</samp>&rsquo; constraint.
 </p></dd></dl>

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	<a name="Old-Constraints"></a>
	<div class="header">
	<p>
	Next: <a href="Stack-and-Calling.html#Stack-and-Calling" accesskey="n" rel="next">Stack and Calling</a>, Previous: <a href="Register-Classes.html#Register-Classes" accesskey="p" rel="prev">Register Classes</a>, Up: <a href="Target-Macros.html#Target-Macros" accesskey="u" rel="up">Target Macros</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
	</div>
	<hr>
	<a name="Obsolete-Macros-for-Defining-Constraints"></a>
	<h3 class="section">17.9 Obsolete Macros for Defining Constraints</h3>
	<a name="index-defining-constraints_002c-obsolete-method"></a>
	<a name="index-constraints_002c-defining_002c-obsolete-method"></a>

	<p>Machine-specific constraints can be defined with these macros instead
	of the machine description constructs described in <a href="Define-Constraints.html#Define-Constraints">Define Constraints</a>. This mechanism is obsolete. New ports should not use
	it; old ports should convert to the new mechanism.
	</p>
	<dl>
	<dt><a name="index-CONSTRAINT_005fLEN"></a>Macro: <strong>CONSTRAINT_LEN</strong> <em>(<var>char</var>, <var>str</var>)</em></dt>
	<dd><p>For the constraint at the start of <var>str</var>, which starts with the letter
	<var>c</var>, return the length. This allows you to have register class /
	constant / extra constraints that are longer than a single letter;
	you don’t need to define this macro if you can do with single-letter
	constraints only. The definition of this macro should use
	DEFAULT_CONSTRAINT_LEN for all the characters that you don’t want
	to handle specially.
	There are some sanity checks in genoutput.c that check the constraint lengths
	for the md file, so you can also use this macro to help you while you are
	transitioning from a byzantine single-letter-constraint scheme: when you
	return a negative length for a constraint you want to re-use, genoutput
	will complain about every instance where it is used in the md file.
	</p></dd></dl>

	<dl>
	<dt><a name="index-REG_005fCLASS_005fFROM_005fLETTER"></a>Macro: <strong>REG_CLASS_FROM_LETTER</strong> <em>(<var>char</var>)</em></dt>
	<dd><p>A C expression which defines the machine-dependent operand constraint
	letters for register classes. If <var>char</var> is such a letter, the
	value should be the register class corresponding to it. Otherwise,
	the value should be <code>NO_REGS</code>. The register letter ‘<samp>r</samp>’,
	corresponding to class <code>GENERAL_REGS</code>, will not be passed
	to this macro; you do not need to handle it.
	</p></dd></dl>

	<dl>
	<dt><a name="index-REG_005fCLASS_005fFROM_005fCONSTRAINT"></a>Macro: <strong>REG_CLASS_FROM_CONSTRAINT</strong> <em>(<var>char</var>, <var>str</var>)</em></dt>
	<dd><p>Like <code>REG_CLASS_FROM_LETTER</code>, but you also get the constraint string
	passed in <var>str</var>, so that you can use suffixes to distinguish between
	different variants.
	</p></dd></dl>

	<dl>
	<dt><a name="index-CONST_005fOK_005fFOR_005fLETTER_005fP"></a>Macro: <strong>CONST_OK_FOR_LETTER_P</strong> <em>(<var>value</var>, <var>c</var>)</em></dt>
	<dd><p>A C expression that defines the machine-dependent operand constraint
	letters (‘<samp>I</samp>’, ‘<samp>J</samp>’, ‘<samp>K</samp>’, … ‘<samp>P</samp>’) that specify
	particular ranges of integer values. If <var>c</var> is one of those
	letters, the expression should check that <var>value</var>, an integer, is in
	the appropriate range and return 1 if so, 0 otherwise. If <var>c</var> is
	not one of those letters, the value should be 0 regardless of
	<var>value</var>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-CONST_005fOK_005fFOR_005fCONSTRAINT_005fP"></a>Macro: <strong>CONST_OK_FOR_CONSTRAINT_P</strong> <em>(<var>value</var>, <var>c</var>, <var>str</var>)</em></dt>
	<dd><p>Like <code>CONST_OK_FOR_LETTER_P</code>, but you also get the constraint
	string passed in <var>str</var>, so that you can use suffixes to distinguish
	between different variants.
	</p></dd></dl>

	<dl>
	<dt><a name="index-CONST_005fDOUBLE_005fOK_005fFOR_005fLETTER_005fP"></a>Macro: <strong>CONST_DOUBLE_OK_FOR_LETTER_P</strong> <em>(<var>value</var>, <var>c</var>)</em></dt>
	<dd><p>A C expression that defines the machine-dependent operand constraint
	letters that specify particular ranges of <code>const_double</code> values
	(‘<samp>G</samp>’ or ‘<samp>H</samp>’).
	</p>
	<p>If <var>c</var> is one of those letters, the expression should check that
	<var>value</var>, an RTX of code <code>const_double</code>, is in the appropriate
	range and return 1 if so, 0 otherwise. If <var>c</var> is not one of those
	letters, the value should be 0 regardless of <var>value</var>.
	</p>
	<p><code>const_double</code> is used for all floating-point constants and for
	<code>DImode</code> fixed-point constants. A given letter can accept either
	or both kinds of values. It can use <code>GET_MODE</code> to distinguish
	between these kinds.
	</p></dd></dl>

	<dl>
	<dt><a name="index-CONST_005fDOUBLE_005fOK_005fFOR_005fCONSTRAINT_005fP"></a>Macro: <strong>CONST_DOUBLE_OK_FOR_CONSTRAINT_P</strong> <em>(<var>value</var>, <var>c</var>, <var>str</var>)</em></dt>
	<dd><p>Like <code>CONST_DOUBLE_OK_FOR_LETTER_P</code>, but you also get the constraint
	string passed in <var>str</var>, so that you can use suffixes to distinguish
	between different variants.
	</p></dd></dl>

	<dl>
	<dt><a name="index-EXTRA_005fCONSTRAINT"></a>Macro: <strong>EXTRA_CONSTRAINT</strong> <em>(<var>value</var>, <var>c</var>)</em></dt>
	<dd><p>A C expression that defines the optional machine-dependent constraint
	letters that can be used to segregate specific types of operands, usually
	memory references, for the target machine. Any letter that is not
	elsewhere defined and not matched by <code>REG_CLASS_FROM_LETTER</code> /
	<code>REG_CLASS_FROM_CONSTRAINT</code>
	may be used. Normally this macro will not be defined.
	</p>
	<p>If it is required for a particular target machine, it should return 1
	if <var>value</var> corresponds to the operand type represented by the
	constraint letter <var>c</var>. If <var>c</var> is not defined as an extra
	constraint, the value returned should be 0 regardless of <var>value</var>.
	</p>
	<p>For example, on the ROMP, load instructions cannot have their output
	in r0 if the memory reference contains a symbolic address. Constraint
	letter ‘<samp>Q</samp>’ is defined as representing a memory address that does
	<em>not</em> contain a symbolic address. An alternative is specified with
	a ‘<samp>Q</samp>’ constraint on the input and ‘<samp>r</samp>’ on the output. The next
	alternative specifies ‘<samp>m</samp>’ on the input and a register class that
	does not include r0 on the output.
	</p></dd></dl>

	<dl>
	<dt><a name="index-EXTRA_005fCONSTRAINT_005fSTR"></a>Macro: <strong>EXTRA_CONSTRAINT_STR</strong> <em>(<var>value</var>, <var>c</var>, <var>str</var>)</em></dt>
	<dd><p>Like <code>EXTRA_CONSTRAINT</code>, but you also get the constraint string passed
	in <var>str</var>, so that you can use suffixes to distinguish between different
	variants.
	</p></dd></dl>

	<dl>
	<dt><a name="index-EXTRA_005fMEMORY_005fCONSTRAINT"></a>Macro: <strong>EXTRA_MEMORY_CONSTRAINT</strong> <em>(<var>c</var>, <var>str</var>)</em></dt>
	<dd><p>A C expression that defines the optional machine-dependent constraint
	letters, amongst those accepted by <code>EXTRA_CONSTRAINT</code>, that should
	be treated like memory constraints by the reload pass.
	</p>
	<p>It should return 1 if the operand type represented by the constraint
	at the start of <var>str</var>, the first letter of which is the letter <var>c</var>,
	comprises a subset of all memory references including
	all those whose address is simply a base register. This allows the reload
	pass to reload an operand, if it does not directly correspond to the operand
	type of <var>c</var>, by copying its address into a base register.
	</p>
	<p>For example, on the S/390, some instructions do not accept arbitrary
	memory references, but only those that do not make use of an index
	register. The constraint letter ‘<samp>Q</samp>’ is defined via
	<code>EXTRA_CONSTRAINT</code> as representing a memory address of this type.
	If the letter ‘<samp>Q</samp>’ is marked as <code>EXTRA_MEMORY_CONSTRAINT</code>,
	a ‘<samp>Q</samp>’ constraint can handle any memory operand, because the
	reload pass knows it can be reloaded by copying the memory address
	into a base register if required. This is analogous to the way
	an ‘<samp>o</samp>’ constraint can handle any memory operand.
	</p></dd></dl>

	<dl>
	<dt><a name="index-EXTRA_005fADDRESS_005fCONSTRAINT"></a>Macro: <strong>EXTRA_ADDRESS_CONSTRAINT</strong> <em>(<var>c</var>, <var>str</var>)</em></dt>
	<dd><p>A C expression that defines the optional machine-dependent constraint
	letters, amongst those accepted by <code>EXTRA_CONSTRAINT</code> /
	<code>EXTRA_CONSTRAINT_STR</code>, that should
	be treated like address constraints by the reload pass.
	</p>
	<p>It should return 1 if the operand type represented by the constraint
	at the start of <var>str</var>, which starts with the letter <var>c</var>, comprises
	a subset of all memory addresses including
	all those that consist of just a base register. This allows the reload
	pass to reload an operand, if it does not directly correspond to the operand
	type of <var>str</var>, by copying it into a base register.
	</p>
	<p>Any constraint marked as <code>EXTRA_ADDRESS_CONSTRAINT</code> can only
	be used with the <code>address_operand</code> predicate. It is treated
	analogously to the ‘<samp>p</samp>’ constraint.
	</p></dd></dl>

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