aarch64-linux-gnu-4.9/share/doc/gccint/Dispatch-Tables.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: Dispatch Tables</title>

 <meta name="description" content="GNU Compiler Collection (GCC) Internals: Dispatch Tables">
 <meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Dispatch Tables">
 <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="Assembler-Format.html#Assembler-Format" rel="up" title="Assembler Format">
 <link href="Exception-Region-Output.html#Exception-Region-Output" rel="next" title="Exception Region Output">
 <link href="Instruction-Output.html#Instruction-Output" rel="prev" title="Instruction Output">
 <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="Dispatch-Tables"></a>
 <div class="header">
 <p>
 Next: <a href="Exception-Region-Output.html#Exception-Region-Output" accesskey="n" rel="next">Exception Region Output</a>, Previous: <a href="Instruction-Output.html#Instruction-Output" accesskey="p" rel="prev">Instruction Output</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</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="Output-of-Dispatch-Tables"></a>
 <h4 class="subsection">17.21.8 Output of Dispatch Tables</h4>

 <p>This concerns dispatch tables.
 </p>
 <a name="index-dispatch-table"></a>
 <dl>
 <dt><a name="index-ASM_005fOUTPUT_005fADDR_005fDIFF_005fELT"></a>Macro: <strong>ASM_OUTPUT_ADDR_DIFF_ELT</strong> <em>(<var>stream</var>, <var>body</var>, <var>value</var>, <var>rel</var>)</em></dt>
 <dd><p>A C statement to output to the stdio stream <var>stream</var> an assembler
 pseudo-instruction to generate a difference between two labels.
 <var>value</var> and <var>rel</var> are the numbers of two internal labels.  The
 definitions of these labels are output using
 <code>(*targetm.asm_out.internal_label)</code>, and they must be printed in the same
 way here.  For example,
 </p>
 <div class="smallexample">
 <pre class="smallexample">fprintf (<var>stream</var>, &quot;\t.word L%d-L%d\n&quot;,
          <var>value</var>, <var>rel</var>)
 </pre></div>

 <p>You must provide this macro on machines where the addresses in a
 dispatch table are relative to the table&rsquo;s own address.  If defined, GCC
 will also use this macro on all machines when producing PIC.
 <var>body</var> is the body of the <code>ADDR_DIFF_VEC</code>; it is provided so that the
 mode and flags can be read.
 </p></dd></dl>

 <dl>
 <dt><a name="index-ASM_005fOUTPUT_005fADDR_005fVEC_005fELT"></a>Macro: <strong>ASM_OUTPUT_ADDR_VEC_ELT</strong> <em>(<var>stream</var>, <var>value</var>)</em></dt>
 <dd><p>This macro should be provided on machines where the addresses
 in a dispatch table are absolute.
 </p>
 <p>The definition should be a C statement to output to the stdio stream
 <var>stream</var> an assembler pseudo-instruction to generate a reference to
 a label.  <var>value</var> is the number of an internal label whose
 definition is output using <code>(*targetm.asm_out.internal_label)</code>.
 For example,
 </p>
 <div class="smallexample">
 <pre class="smallexample">fprintf (<var>stream</var>, &quot;\t.word L%d\n&quot;, <var>value</var>)
 </pre></div>
 </dd></dl>

 <dl>
 <dt><a name="index-ASM_005fOUTPUT_005fCASE_005fLABEL"></a>Macro: <strong>ASM_OUTPUT_CASE_LABEL</strong> <em>(<var>stream</var>, <var>prefix</var>, <var>num</var>, <var>table</var>)</em></dt>
 <dd><p>Define this if the label before a jump-table needs to be output
 specially.  The first three arguments are the same as for
 <code>(*targetm.asm_out.internal_label)</code>; the fourth argument is the
 jump-table which follows (a <code>jump_table_data</code> containing an
 <code>addr_vec</code> or <code>addr_diff_vec</code>).
 </p>
 <p>This feature is used on system V to output a <code>swbeg</code> statement
 for the table.
 </p>
 <p>If this macro is not defined, these labels are output with
 <code>(*targetm.asm_out.internal_label)</code>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-ASM_005fOUTPUT_005fCASE_005fEND"></a>Macro: <strong>ASM_OUTPUT_CASE_END</strong> <em>(<var>stream</var>, <var>num</var>, <var>table</var>)</em></dt>
 <dd><p>Define this if something special must be output at the end of a
 jump-table.  The definition should be a C statement to be executed
 after the assembler code for the table is written.  It should write
 the appropriate code to stdio stream <var>stream</var>.  The argument
 <var>table</var> is the jump-table insn, and <var>num</var> is the label-number
 of the preceding label.
 </p>
 <p>If this macro is not defined, nothing special is output at the end of
 the jump-table.
 </p></dd></dl>

 <dl>
 <dt><a name="index-TARGET_005fASM_005fEMIT_005fUNWIND_005fLABEL"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_EMIT_UNWIND_LABEL</strong> <em>(FILE *<var>stream</var>, tree <var>decl</var>, int <var>for_eh</var>, int <var>empty</var>)</em></dt>
 <dd><p>This target hook emits a label at the beginning of each FDE.  It
 should be defined on targets where FDEs need special labels, and it
 should write the appropriate label, for the FDE associated with the
 function declaration <var>decl</var>, to the stdio stream <var>stream</var>.
 The third argument, <var>for_eh</var>, is a boolean: true if this is for an
 exception table.  The fourth argument, <var>empty</var>, is a boolean:
 true if this is a placeholder label for an omitted FDE.
 </p>
 <p>The default is that FDEs are not given nonlocal labels.
 </p></dd></dl>

 <dl>
 <dt><a name="index-TARGET_005fASM_005fEMIT_005fEXCEPT_005fTABLE_005fLABEL"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_EMIT_EXCEPT_TABLE_LABEL</strong> <em>(FILE *<var>stream</var>)</em></dt>
 <dd><p>This target hook emits a label at the beginning of the exception table.
 It should be defined on targets where it is desirable for the table
 to be broken up according to function.
 </p>
 <p>The default is that no label is emitted.
 </p></dd></dl>

 <dl>
 <dt><a name="index-TARGET_005fASM_005fEMIT_005fEXCEPT_005fPERSONALITY"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_EMIT_EXCEPT_PERSONALITY</strong> <em>(rtx <var>personality</var>)</em></dt>
 <dd><p>If the target implements <code>TARGET_ASM_UNWIND_EMIT</code>, this hook may be used to emit a directive to install a personality hook into the unwind info.  This hook should not be used if dwarf2 unwind info is used.
 </p></dd></dl>

 <dl>
 <dt><a name="index-TARGET_005fASM_005fUNWIND_005fEMIT"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_UNWIND_EMIT</strong> <em>(FILE *<var>stream</var>, rtx <var>insn</var>)</em></dt>
 <dd><p>This target hook emits assembly directives required to unwind the
 given instruction.  This is only used when <code>TARGET_EXCEPT_UNWIND_INFO</code>
 returns <code>UI_TARGET</code>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-TARGET_005fASM_005fUNWIND_005fEMIT_005fBEFORE_005fINSN"></a>Target Hook: <em>bool</em> <strong>TARGET_ASM_UNWIND_EMIT_BEFORE_INSN</strong></dt>
 <dd><p>True if the <code>TARGET_ASM_UNWIND_EMIT</code> hook should be called before the assembly for <var>insn</var> has been emitted, false if the hook should be called afterward.
 </p></dd></dl>

 <hr>
 <div class="header">
 <p>
 Next: <a href="Exception-Region-Output.html#Exception-Region-Output" accesskey="n" rel="next">Exception Region Output</a>, Previous: <a href="Instruction-Output.html#Instruction-Output" accesskey="p" rel="prev">Instruction Output</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</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: Dispatch Tables</title>

	<meta name="description" content="GNU Compiler Collection (GCC) Internals: Dispatch Tables">
	<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Dispatch Tables">
	<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="Assembler-Format.html#Assembler-Format" rel="up" title="Assembler Format">
	<link href="Exception-Region-Output.html#Exception-Region-Output" rel="next" title="Exception Region Output">
	<link href="Instruction-Output.html#Instruction-Output" rel="prev" title="Instruction Output">
	<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="Dispatch-Tables"></a>
	<div class="header">
	<p>
	Next: <a href="Exception-Region-Output.html#Exception-Region-Output" accesskey="n" rel="next">Exception Region Output</a>, Previous: <a href="Instruction-Output.html#Instruction-Output" accesskey="p" rel="prev">Instruction Output</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</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="Output-of-Dispatch-Tables"></a>
	<h4 class="subsection">17.21.8 Output of Dispatch Tables</h4>

	<p>This concerns dispatch tables.
	</p>
	<a name="index-dispatch-table"></a>
	<dl>
	<dt><a name="index-ASM_005fOUTPUT_005fADDR_005fDIFF_005fELT"></a>Macro: <strong>ASM_OUTPUT_ADDR_DIFF_ELT</strong> <em>(<var>stream</var>, <var>body</var>, <var>value</var>, <var>rel</var>)</em></dt>
	<dd><p>A C statement to output to the stdio stream <var>stream</var> an assembler
	pseudo-instruction to generate a difference between two labels.
	<var>value</var> and <var>rel</var> are the numbers of two internal labels. The
	definitions of these labels are output using
	<code>(*targetm.asm_out.internal_label)</code>, and they must be printed in the same
	way here. For example,
	</p>
	<div class="smallexample">
	<pre class="smallexample">fprintf (<var>stream</var>, "\t.word L%d-L%d\n",
	<var>value</var>, <var>rel</var>)
	</pre></div>

	<p>You must provide this macro on machines where the addresses in a
	dispatch table are relative to the table’s own address. If defined, GCC
	will also use this macro on all machines when producing PIC.
	<var>body</var> is the body of the <code>ADDR_DIFF_VEC</code>; it is provided so that the
	mode and flags can be read.
	</p></dd></dl>

	<dl>
	<dt><a name="index-ASM_005fOUTPUT_005fADDR_005fVEC_005fELT"></a>Macro: <strong>ASM_OUTPUT_ADDR_VEC_ELT</strong> <em>(<var>stream</var>, <var>value</var>)</em></dt>
	<dd><p>This macro should be provided on machines where the addresses
	in a dispatch table are absolute.
	</p>
	<p>The definition should be a C statement to output to the stdio stream
	<var>stream</var> an assembler pseudo-instruction to generate a reference to
	a label. <var>value</var> is the number of an internal label whose
	definition is output using <code>(*targetm.asm_out.internal_label)</code>.
	For example,
	</p>
	<div class="smallexample">
	<pre class="smallexample">fprintf (<var>stream</var>, "\t.word L%d\n", <var>value</var>)
	</pre></div>
	</dd></dl>

	<dl>
	<dt><a name="index-ASM_005fOUTPUT_005fCASE_005fLABEL"></a>Macro: <strong>ASM_OUTPUT_CASE_LABEL</strong> <em>(<var>stream</var>, <var>prefix</var>, <var>num</var>, <var>table</var>)</em></dt>
	<dd><p>Define this if the label before a jump-table needs to be output
	specially. The first three arguments are the same as for
	<code>(*targetm.asm_out.internal_label)</code>; the fourth argument is the
	jump-table which follows (a <code>jump_table_data</code> containing an
	<code>addr_vec</code> or <code>addr_diff_vec</code>).
	</p>
	<p>This feature is used on system V to output a <code>swbeg</code> statement
	for the table.
	</p>
	<p>If this macro is not defined, these labels are output with
	<code>(*targetm.asm_out.internal_label)</code>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-ASM_005fOUTPUT_005fCASE_005fEND"></a>Macro: <strong>ASM_OUTPUT_CASE_END</strong> <em>(<var>stream</var>, <var>num</var>, <var>table</var>)</em></dt>
	<dd><p>Define this if something special must be output at the end of a
	jump-table. The definition should be a C statement to be executed
	after the assembler code for the table is written. It should write
	the appropriate code to stdio stream <var>stream</var>. The argument
	<var>table</var> is the jump-table insn, and <var>num</var> is the label-number
	of the preceding label.
	</p>
	<p>If this macro is not defined, nothing special is output at the end of
	the jump-table.
	</p></dd></dl>

	<dl>
	<dt><a name="index-TARGET_005fASM_005fEMIT_005fUNWIND_005fLABEL"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_EMIT_UNWIND_LABEL</strong> <em>(FILE *<var>stream</var>, tree <var>decl</var>, int <var>for_eh</var>, int <var>empty</var>)</em></dt>
	<dd><p>This target hook emits a label at the beginning of each FDE. It
	should be defined on targets where FDEs need special labels, and it
	should write the appropriate label, for the FDE associated with the
	function declaration <var>decl</var>, to the stdio stream <var>stream</var>.
	The third argument, <var>for_eh</var>, is a boolean: true if this is for an
	exception table. The fourth argument, <var>empty</var>, is a boolean:
	true if this is a placeholder label for an omitted FDE.
	</p>
	<p>The default is that FDEs are not given nonlocal labels.
	</p></dd></dl>

	<dl>
	<dt><a name="index-TARGET_005fASM_005fEMIT_005fEXCEPT_005fTABLE_005fLABEL"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_EMIT_EXCEPT_TABLE_LABEL</strong> <em>(FILE *<var>stream</var>)</em></dt>
	<dd><p>This target hook emits a label at the beginning of the exception table.
	It should be defined on targets where it is desirable for the table
	to be broken up according to function.
	</p>
	<p>The default is that no label is emitted.
	</p></dd></dl>

	<dl>
	<dt><a name="index-TARGET_005fASM_005fEMIT_005fEXCEPT_005fPERSONALITY"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_EMIT_EXCEPT_PERSONALITY</strong> <em>(rtx <var>personality</var>)</em></dt>
	<dd><p>If the target implements <code>TARGET_ASM_UNWIND_EMIT</code>, this hook may be used to emit a directive to install a personality hook into the unwind info. This hook should not be used if dwarf2 unwind info is used.
	</p></dd></dl>

	<dl>
	<dt><a name="index-TARGET_005fASM_005fUNWIND_005fEMIT"></a>Target Hook: <em>void</em> <strong>TARGET_ASM_UNWIND_EMIT</strong> <em>(FILE *<var>stream</var>, rtx <var>insn</var>)</em></dt>
	<dd><p>This target hook emits assembly directives required to unwind the
	given instruction. This is only used when <code>TARGET_EXCEPT_UNWIND_INFO</code>
	returns <code>UI_TARGET</code>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-TARGET_005fASM_005fUNWIND_005fEMIT_005fBEFORE_005fINSN"></a>Target Hook: <em>bool</em> <strong>TARGET_ASM_UNWIND_EMIT_BEFORE_INSN</strong></dt>
	<dd><p>True if the <code>TARGET_ASM_UNWIND_EMIT</code> hook should be called before the assembly for <var>insn</var> has been emitted, false if the hook should be called afterward.
	</p></dd></dl>

	<hr>
	<div class="header">
	<p>
	Next: <a href="Exception-Region-Output.html#Exception-Region-Output" accesskey="n" rel="next">Exception Region Output</a>, Previous: <a href="Instruction-Output.html#Instruction-Output" accesskey="p" rel="prev">Instruction Output</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</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>