aarch64-linux-gnu-4.9/share/doc/gccint/MODE_005fCC-Condition-Codes.html - toolchains/linux-x86/gcc - Git at Google

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <!-- Copyright (C) 1988-2015 Free Software Foundation, Inc.

 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
 any later version published by the Free Software Foundation; with the
 Invariant Sections being "Funding Free Software", the Front-Cover
 Texts being (a) (see below), and with the Back-Cover Texts being (b)
 (see below).  A copy of the license is included in the section entitled
 "GNU Free Documentation License".

 (a) The FSF's Front-Cover Text is:

 A GNU Manual

 (b) The FSF's Back-Cover Text is:

 You have freedom to copy and modify this GNU Manual, like GNU
      software.  Copies published by the Free Software Foundation raise
      funds for GNU development. -->
 <!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
 <head>
 <title>GNU Compiler Collection (GCC) Internals: MODE_CC Condition Codes</title>

 <meta name="description" content="GNU Compiler Collection (GCC) Internals: MODE_CC Condition Codes">
 <meta name="keywords" content="GNU Compiler Collection (GCC) Internals: MODE_CC Condition Codes">
 <meta name="resource-type" content="document">
 <meta name="distribution" content="global">
 <meta name="Generator" content="makeinfo">
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
 <link href="index.html#Top" rel="start" title="Top">
 <link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
 <link href="Condition-Code.html#Condition-Code" rel="up" title="Condition Code">
 <link href="Costs.html#Costs" rel="next" title="Costs">
 <link href="CC0-Condition-Codes.html#CC0-Condition-Codes" rel="prev" title="CC0 Condition Codes">
 <style type="text/css">
 <!--
 a.summary-letter {text-decoration: none}
 blockquote.smallquotation {font-size: smaller}
 div.display {margin-left: 3.2em}
 div.example {margin-left: 3.2em}
 div.indentedblock {margin-left: 3.2em}
 div.lisp {margin-left: 3.2em}
 div.smalldisplay {margin-left: 3.2em}
 div.smallexample {margin-left: 3.2em}
 div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
 div.smalllisp {margin-left: 3.2em}
 kbd {font-style:oblique}
 pre.display {font-family: inherit}
 pre.format {font-family: inherit}
 pre.menu-comment {font-family: serif}
 pre.menu-preformatted {font-family: serif}
 pre.smalldisplay {font-family: inherit; font-size: smaller}
 pre.smallexample {font-size: smaller}
 pre.smallformat {font-family: inherit; font-size: smaller}
 pre.smalllisp {font-size: smaller}
 span.nocodebreak {white-space:nowrap}
 span.nolinebreak {white-space:nowrap}
 span.roman {font-family:serif; font-weight:normal}
 span.sansserif {font-family:sans-serif; font-weight:normal}
 ul.no-bullet {list-style: none}
 -->
 </style>


 </head>

 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
 <a name="MODE_005fCC-Condition-Codes"></a>
 <div class="header">
 <p>
 Previous: <a href="CC0-Condition-Codes.html#CC0-Condition-Codes" accesskey="p" rel="prev">CC0 Condition Codes</a>, Up: <a href="Condition-Code.html#Condition-Code" accesskey="u" rel="up">Condition Code</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="Representation-of-condition-codes-using-registers"></a>
 <h4 class="subsection">17.16.2 Representation of condition codes using registers</h4>
 <a name="index-CCmode-1"></a>
 <a name="index-MODE_005fCC-1"></a>

 <dl>
 <dt><a name="index-SELECT_005fCC_005fMODE"></a>Macro: <strong>SELECT_CC_MODE</strong> <em>(<var>op</var>, <var>x</var>, <var>y</var>)</em></dt>
 <dd><p>On many machines, the condition code may be produced by other instructions
 than compares, for example the branch can use directly the condition
 code set by a subtract instruction.  However, on some machines
 when the condition code is set this way some bits (such as the overflow
 bit) are not set in the same way as a test instruction, so that a different
 branch instruction must be used for some conditional branches.  When
 this happens, use the machine mode of the condition code register to
 record different formats of the condition code register.  Modes can
 also be used to record which compare instruction (e.g. a signed or an
 unsigned comparison) produced the condition codes.
 </p>
 <p>If other modes than <code>CCmode</code> are required, add them to
 <samp><var>machine</var>-modes.def</samp> and define <code>SELECT_CC_MODE</code> to choose
 a mode given an operand of a compare.  This is needed because the modes
 have to be chosen not only during RTL generation but also, for example,
 by instruction combination.  The result of <code>SELECT_CC_MODE</code> should
 be consistent with the mode used in the patterns; for example to support
 the case of the add on the SPARC discussed above, we have the pattern
 </p>
 <div class="smallexample">
 <pre class="smallexample">(define_insn &quot;&quot;
   [(set (reg:CC_NOOV 0)
         (compare:CC_NOOV
           (plus:SI (match_operand:SI 0 &quot;register_operand&quot; &quot;%r&quot;)
                    (match_operand:SI 1 &quot;arith_operand&quot; &quot;rI&quot;))
           (const_int 0)))]
   &quot;&quot;
   &quot;&hellip;&quot;)
 </pre></div>

 <p>together with a <code>SELECT_CC_MODE</code> that returns <code>CC_NOOVmode</code>
 for comparisons whose argument is a <code>plus</code>:
 </p>
 <div class="smallexample">
 <pre class="smallexample">#define SELECT_CC_MODE(OP,X,Y) \
   (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT           \
    ? ((OP == LT || OP == LE || OP == GT || OP == GE)     \
       ? CCFPEmode : CCFPmode)                            \
    : ((GET_CODE (X) == PLUS || GET_CODE (X) == MINUS     \
        || GET_CODE (X) == NEG || GET_CODE (x) == ASHIFT) \
       ? CC_NOOVmode : CCmode))
 </pre></div>

 <p>Another reason to use modes is to retain information on which operands
 were used by the comparison; see <code>REVERSIBLE_CC_MODE</code> later in
 this section.
 </p>
 <p>You should define this macro if and only if you define extra CC modes
 in <samp><var>machine</var>-modes.def</samp>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-TARGET_005fCANONICALIZE_005fCOMPARISON"></a>Target Hook: <em>void</em> <strong>TARGET_CANONICALIZE_COMPARISON</strong> <em>(int *<var>code</var>, rtx *<var>op0</var>, rtx *<var>op1</var>, bool <var>op0_preserve_value</var>)</em></dt>
 <dd><p>On some machines not all possible comparisons are defined, but you can
 convert an invalid comparison into a valid one.  For example, the Alpha
 does not have a <code>GT</code> comparison, but you can use an <code>LT</code>
 comparison instead and swap the order of the operands.
 </p>
 <p>On such machines, implement this hook to do any required conversions.
 <var>code</var> is the initial comparison code and <var>op0</var> and <var>op1</var>
 are the left and right operands of the comparison, respectively.  If
 <var>op0_preserve_value</var> is <code>true</code> the implementation is not
 allowed to change the value of <var>op0</var> since the value might be used
 in RTXs which aren&rsquo;t comparisons.  E.g. the implementation is not
 allowed to swap operands in that case.
 </p>
 <p>GCC will not assume that the comparison resulting from this macro is
 valid but will see if the resulting insn matches a pattern in the
 <samp>md</samp> file.
 </p>
 <p>You need not to implement this hook if it would never change the
 comparison code or operands.
 </p></dd></dl>

 <dl>
 <dt><a name="index-REVERSIBLE_005fCC_005fMODE"></a>Macro: <strong>REVERSIBLE_CC_MODE</strong> <em>(<var>mode</var>)</em></dt>
 <dd><p>A C expression whose value is one if it is always safe to reverse a
 comparison whose mode is <var>mode</var>.  If <code>SELECT_CC_MODE</code>
 can ever return <var>mode</var> for a floating-point inequality comparison,
 then <code>REVERSIBLE_CC_MODE (<var>mode</var>)</code> must be zero.
 </p>
 <p>You need not define this macro if it would always returns zero or if the
 floating-point format is anything other than <code>IEEE_FLOAT_FORMAT</code>.
 For example, here is the definition used on the SPARC, where floating-point
 inequality comparisons are given either <code>CCFPEmode</code> or <code>CCFPmode</code>:
 </p>
 <div class="smallexample">
 <pre class="smallexample">#define REVERSIBLE_CC_MODE(MODE) \
    ((MODE) != CCFPEmode &amp;&amp; (MODE) != CCFPmode)
 </pre></div>
 </dd></dl>

 <dl>
 <dt><a name="index-REVERSE_005fCONDITION"></a>Macro: <strong>REVERSE_CONDITION</strong> <em>(<var>code</var>, <var>mode</var>)</em></dt>
 <dd><p>A C expression whose value is reversed condition code of the <var>code</var> for
 comparison done in CC_MODE <var>mode</var>.  The macro is used only in case
 <code>REVERSIBLE_CC_MODE (<var>mode</var>)</code> is nonzero.  Define this macro in case
 machine has some non-standard way how to reverse certain conditionals.  For
 instance in case all floating point conditions are non-trapping, compiler may
 freely convert unordered compares to ordered ones.  Then definition may look
 like:
 </p>
 <div class="smallexample">
 <pre class="smallexample">#define REVERSE_CONDITION(CODE, MODE) \
    ((MODE) != CCFPmode ? reverse_condition (CODE) \
     : reverse_condition_maybe_unordered (CODE))
 </pre></div>
 </dd></dl>

 <dl>
 <dt><a name="index-TARGET_005fFIXED_005fCONDITION_005fCODE_005fREGS"></a>Target Hook: <em>bool</em> <strong>TARGET_FIXED_CONDITION_CODE_REGS</strong> <em>(unsigned int *<var>p1</var>, unsigned int *<var>p2</var>)</em></dt>
 <dd><p>On targets which do not use <code>(cc0)</code>, and which use a hard
 register rather than a pseudo-register to hold condition codes, the
 regular CSE passes are often not able to identify cases in which the
 hard register is set to a common value.  Use this hook to enable a
 small pass which optimizes such cases.  This hook should return true
 to enable this pass, and it should set the integers to which its
 arguments point to the hard register numbers used for condition codes.
 When there is only one such register, as is true on most systems, the
 integer pointed to by <var>p2</var> should be set to
 <code>INVALID_REGNUM</code>.
 </p>
 <p>The default version of this hook returns false.
 </p></dd></dl>

 <dl>
 <dt><a name="index-TARGET_005fCC_005fMODES_005fCOMPATIBLE"></a>Target Hook: <em>enum machine_mode</em> <strong>TARGET_CC_MODES_COMPATIBLE</strong> <em>(enum machine_mode <var>m1</var>, enum machine_mode <var>m2</var>)</em></dt>
 <dd><p>On targets which use multiple condition code modes in class
 <code>MODE_CC</code>, it is sometimes the case that a comparison can be
 validly done in more than one mode.  On such a system, define this
 target hook to take two mode arguments and to return a mode in which
 both comparisons may be validly done.  If there is no such mode,
 return <code>VOIDmode</code>.
 </p>
 <p>The default version of this hook checks whether the modes are the
 same.  If they are, it returns that mode.  If they are different, it
 returns <code>VOIDmode</code>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-TARGET_005fFLAGS_005fREGNUM"></a>Target Hook: <em>unsigned int</em> <strong>TARGET_FLAGS_REGNUM</strong></dt>
 <dd><p>If the target has a dedicated flags register, and it needs to use the post-reload comparison elimination pass, then this value should be set appropriately.
 </p></dd></dl>

 <hr>
 <div class="header">
 <p>
 Previous: <a href="CC0-Condition-Codes.html#CC0-Condition-Codes" accesskey="p" rel="prev">CC0 Condition Codes</a>, Up: <a href="Condition-Code.html#Condition-Code" accesskey="u" rel="up">Condition Code</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>


 </body>
 </html>
	<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
	<html>
	<!-- Copyright (C) 1988-2015 Free Software Foundation, Inc.

	Permission is granted to copy, distribute and/or modify this document
	under the terms of the GNU Free Documentation License, Version 1.3 or
	any later version published by the Free Software Foundation; with the
	Invariant Sections being "Funding Free Software", the Front-Cover
	Texts being (a) (see below), and with the Back-Cover Texts being (b)
	(see below). A copy of the license is included in the section entitled
	"GNU Free Documentation License".

	(a) The FSF's Front-Cover Text is:

	A GNU Manual

	(b) The FSF's Back-Cover Text is:

	You have freedom to copy and modify this GNU Manual, like GNU
	software. Copies published by the Free Software Foundation raise
	funds for GNU development. -->
	<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
	<head>
	<title>GNU Compiler Collection (GCC) Internals: MODE_CC Condition Codes</title>

	<meta name="description" content="GNU Compiler Collection (GCC) Internals: MODE_CC Condition Codes">
	<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: MODE_CC Condition Codes">
	<meta name="resource-type" content="document">
	<meta name="distribution" content="global">
	<meta name="Generator" content="makeinfo">
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
	<link href="index.html#Top" rel="start" title="Top">
	<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
	<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
	<link href="Condition-Code.html#Condition-Code" rel="up" title="Condition Code">
	<link href="Costs.html#Costs" rel="next" title="Costs">
	<link href="CC0-Condition-Codes.html#CC0-Condition-Codes" rel="prev" title="CC0 Condition Codes">
	<style type="text/css">
	<!--
	a.summary-letter {text-decoration: none}
	blockquote.smallquotation {font-size: smaller}
	div.display {margin-left: 3.2em}
	div.example {margin-left: 3.2em}
	div.indentedblock {margin-left: 3.2em}
	div.lisp {margin-left: 3.2em}
	div.smalldisplay {margin-left: 3.2em}
	div.smallexample {margin-left: 3.2em}
	div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
	div.smalllisp {margin-left: 3.2em}
	kbd {font-style:oblique}
	pre.display {font-family: inherit}
	pre.format {font-family: inherit}
	pre.menu-comment {font-family: serif}
	pre.menu-preformatted {font-family: serif}
	pre.smalldisplay {font-family: inherit; font-size: smaller}
	pre.smallexample {font-size: smaller}
	pre.smallformat {font-family: inherit; font-size: smaller}
	pre.smalllisp {font-size: smaller}
	span.nocodebreak {white-space:nowrap}
	span.nolinebreak {white-space:nowrap}
	span.roman {font-family:serif; font-weight:normal}
	span.sansserif {font-family:sans-serif; font-weight:normal}
	ul.no-bullet {list-style: none}
	-->
	</style>


	</head>

	<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
	<a name="MODE_005fCC-Condition-Codes"></a>
	<div class="header">
	<p>
	Previous: <a href="CC0-Condition-Codes.html#CC0-Condition-Codes" accesskey="p" rel="prev">CC0 Condition Codes</a>, Up: <a href="Condition-Code.html#Condition-Code" accesskey="u" rel="up">Condition Code</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="Representation-of-condition-codes-using-registers"></a>
	<h4 class="subsection">17.16.2 Representation of condition codes using registers</h4>
	<a name="index-CCmode-1"></a>
	<a name="index-MODE_005fCC-1"></a>

	<dl>
	<dt><a name="index-SELECT_005fCC_005fMODE"></a>Macro: <strong>SELECT_CC_MODE</strong> <em>(<var>op</var>, <var>x</var>, <var>y</var>)</em></dt>
	<dd><p>On many machines, the condition code may be produced by other instructions
	than compares, for example the branch can use directly the condition
	code set by a subtract instruction. However, on some machines
	when the condition code is set this way some bits (such as the overflow
	bit) are not set in the same way as a test instruction, so that a different
	branch instruction must be used for some conditional branches. When
	this happens, use the machine mode of the condition code register to
	record different formats of the condition code register. Modes can
	also be used to record which compare instruction (e.g. a signed or an
	unsigned comparison) produced the condition codes.
	</p>
	<p>If other modes than <code>CCmode</code> are required, add them to
	<samp><var>machine</var>-modes.def</samp> and define <code>SELECT_CC_MODE</code> to choose
	a mode given an operand of a compare. This is needed because the modes
	have to be chosen not only during RTL generation but also, for example,
	by instruction combination. The result of <code>SELECT_CC_MODE</code> should
	be consistent with the mode used in the patterns; for example to support
	the case of the add on the SPARC discussed above, we have the pattern
	</p>
	<div class="smallexample">
	<pre class="smallexample">(define_insn ""
	[(set (reg:CC_NOOV 0)
	(compare:CC_NOOV
	(plus:SI (match_operand:SI 0 "register_operand" "%r")
	(match_operand:SI 1 "arith_operand" "rI"))
	(const_int 0)))]
	""
	"…")
	</pre></div>

	<p>together with a <code>SELECT_CC_MODE</code> that returns <code>CC_NOOVmode</code>
	for comparisons whose argument is a <code>plus</code>:
	</p>
	<div class="smallexample">
	<pre class="smallexample">#define SELECT_CC_MODE(OP,X,Y) \
	(GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \
	? ((OP == LT \|\| OP == LE \|\| OP == GT \|\| OP == GE) \
	? CCFPEmode : CCFPmode) \
	: ((GET_CODE (X) == PLUS \|\| GET_CODE (X) == MINUS \
	\|\| GET_CODE (X) == NEG \|\| GET_CODE (x) == ASHIFT) \
	? CC_NOOVmode : CCmode))
	</pre></div>

	<p>Another reason to use modes is to retain information on which operands
	were used by the comparison; see <code>REVERSIBLE_CC_MODE</code> later in
	this section.
	</p>
	<p>You should define this macro if and only if you define extra CC modes
	in <samp><var>machine</var>-modes.def</samp>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-TARGET_005fCANONICALIZE_005fCOMPARISON"></a>Target Hook: <em>void</em> <strong>TARGET_CANONICALIZE_COMPARISON</strong> <em>(int <var>code</var>, rtx <var>op0</var>, rtx *<var>op1</var>, bool <var>op0_preserve_value</var>)</em></dt>
	<dd><p>On some machines not all possible comparisons are defined, but you can
	convert an invalid comparison into a valid one. For example, the Alpha
	does not have a <code>GT</code> comparison, but you can use an <code>LT</code>
	comparison instead and swap the order of the operands.
	</p>
	<p>On such machines, implement this hook to do any required conversions.
	<var>code</var> is the initial comparison code and <var>op0</var> and <var>op1</var>
	are the left and right operands of the comparison, respectively. If
	<var>op0_preserve_value</var> is <code>true</code> the implementation is not
	allowed to change the value of <var>op0</var> since the value might be used
	in RTXs which aren’t comparisons. E.g. the implementation is not
	allowed to swap operands in that case.
	</p>
	<p>GCC will not assume that the comparison resulting from this macro is
	valid but will see if the resulting insn matches a pattern in the
	<samp>md</samp> file.
	</p>
	<p>You need not to implement this hook if it would never change the
	comparison code or operands.
	</p></dd></dl>

	<dl>
	<dt><a name="index-REVERSIBLE_005fCC_005fMODE"></a>Macro: <strong>REVERSIBLE_CC_MODE</strong> <em>(<var>mode</var>)</em></dt>
	<dd><p>A C expression whose value is one if it is always safe to reverse a
	comparison whose mode is <var>mode</var>. If <code>SELECT_CC_MODE</code>
	can ever return <var>mode</var> for a floating-point inequality comparison,
	then <code>REVERSIBLE_CC_MODE (<var>mode</var>)</code> must be zero.
	</p>
	<p>You need not define this macro if it would always returns zero or if the
	floating-point format is anything other than <code>IEEE_FLOAT_FORMAT</code>.
	For example, here is the definition used on the SPARC, where floating-point
	inequality comparisons are given either <code>CCFPEmode</code> or <code>CCFPmode</code>:
	</p>
	<div class="smallexample">
	<pre class="smallexample">#define REVERSIBLE_CC_MODE(MODE) \
	((MODE) != CCFPEmode && (MODE) != CCFPmode)
	</pre></div>
	</dd></dl>

	<dl>
	<dt><a name="index-REVERSE_005fCONDITION"></a>Macro: <strong>REVERSE_CONDITION</strong> <em>(<var>code</var>, <var>mode</var>)</em></dt>
	<dd><p>A C expression whose value is reversed condition code of the <var>code</var> for
	comparison done in CC_MODE <var>mode</var>. The macro is used only in case
	<code>REVERSIBLE_CC_MODE (<var>mode</var>)</code> is nonzero. Define this macro in case
	machine has some non-standard way how to reverse certain conditionals. For
	instance in case all floating point conditions are non-trapping, compiler may
	freely convert unordered compares to ordered ones. Then definition may look
	like:
	</p>
	<div class="smallexample">
	<pre class="smallexample">#define REVERSE_CONDITION(CODE, MODE) \
	((MODE) != CCFPmode ? reverse_condition (CODE) \
	: reverse_condition_maybe_unordered (CODE))
	</pre></div>
	</dd></dl>

	<dl>
	<dt><a name="index-TARGET_005fFIXED_005fCONDITION_005fCODE_005fREGS"></a>Target Hook: <em>bool</em> <strong>TARGET_FIXED_CONDITION_CODE_REGS</strong> <em>(unsigned int <var>p1</var>, unsigned int <var>p2</var>)</em></dt>
	<dd><p>On targets which do not use <code>(cc0)</code>, and which use a hard
	register rather than a pseudo-register to hold condition codes, the
	regular CSE passes are often not able to identify cases in which the
	hard register is set to a common value. Use this hook to enable a
	small pass which optimizes such cases. This hook should return true
	to enable this pass, and it should set the integers to which its
	arguments point to the hard register numbers used for condition codes.
	When there is only one such register, as is true on most systems, the
	integer pointed to by <var>p2</var> should be set to
	<code>INVALID_REGNUM</code>.
	</p>
	<p>The default version of this hook returns false.
	</p></dd></dl>

	<dl>
	<dt><a name="index-TARGET_005fCC_005fMODES_005fCOMPATIBLE"></a>Target Hook: <em>enum machine_mode</em> <strong>TARGET_CC_MODES_COMPATIBLE</strong> <em>(enum machine_mode <var>m1</var>, enum machine_mode <var>m2</var>)</em></dt>
	<dd><p>On targets which use multiple condition code modes in class
	<code>MODE_CC</code>, it is sometimes the case that a comparison can be
	validly done in more than one mode. On such a system, define this
	target hook to take two mode arguments and to return a mode in which
	both comparisons may be validly done. If there is no such mode,
	return <code>VOIDmode</code>.
	</p>
	<p>The default version of this hook checks whether the modes are the
	same. If they are, it returns that mode. If they are different, it
	returns <code>VOIDmode</code>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-TARGET_005fFLAGS_005fREGNUM"></a>Target Hook: <em>unsigned int</em> <strong>TARGET_FLAGS_REGNUM</strong></dt>
	<dd><p>If the target has a dedicated flags register, and it needs to use the post-reload comparison elimination pass, then this value should be set appropriately.
	</p></dd></dl>

	<hr>
	<div class="header">
	<p>
	Previous: <a href="CC0-Condition-Codes.html#CC0-Condition-Codes" accesskey="p" rel="prev">CC0 Condition Codes</a>, Up: <a href="Condition-Code.html#Condition-Code" accesskey="u" rel="up">Condition Code</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>



	</body>
	</html>