252 lines
13 KiB
HTML
252 lines
13 KiB
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2016 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>GNU Compiler Collection (GCC) Internals: Exception Region Output</title>
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<meta name="description" content="GNU Compiler Collection (GCC) Internals: Exception Region Output">
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<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Exception Region Output">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Assembler-Format.html#Assembler-Format" rel="up" title="Assembler Format">
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<link href="Alignment-Output.html#Alignment-Output" rel="next" title="Alignment Output">
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<link href="Dispatch-Tables.html#Dispatch-Tables" rel="prev" title="Dispatch Tables">
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Exception-Region-Output"></a>
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<div class="header">
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<p>
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Next: <a href="Alignment-Output.html#Alignment-Output" accesskey="n" rel="next">Alignment Output</a>, Previous: <a href="Dispatch-Tables.html#Dispatch-Tables" accesskey="p" rel="prev">Dispatch Tables</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>
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</div>
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<hr>
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<a name="Assembler-Commands-for-Exception-Regions"></a>
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<h4 class="subsection">17.20.9 Assembler Commands for Exception Regions</h4>
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<p>This describes commands marking the start and the end of an exception
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region.
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</p>
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<dl>
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<dt><a name="index-EH_005fFRAME_005fSECTION_005fNAME"></a>Macro: <strong>EH_FRAME_SECTION_NAME</strong></dt>
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<dd><p>If defined, a C string constant for the name of the section containing
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exception handling frame unwind information. If not defined, GCC will
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provide a default definition if the target supports named sections.
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<samp>crtstuff.c</samp> uses this macro to switch to the appropriate section.
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</p>
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<p>You should define this symbol if your target supports DWARF 2 frame
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unwind information and the default definition does not work.
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</p></dd></dl>
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<dl>
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<dt><a name="index-EH_005fFRAME_005fTHROUGH_005fCOLLECT2"></a>Macro: <strong>EH_FRAME_THROUGH_COLLECT2</strong></dt>
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<dd><p>If defined, DWARF 2 frame unwind information will identified by
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specially named labels. The collect2 process will locate these
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labels and generate code to register the frames.
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</p>
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<p>This might be necessary, for instance, if the system linker will not
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place the eh_frames in-between the sentinals from <samp>crtstuff.c</samp>,
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or if the system linker does garbage collection and sections cannot
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be marked as not to be collected.
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</p></dd></dl>
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<dl>
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<dt><a name="index-EH_005fTABLES_005fCAN_005fBE_005fREAD_005fONLY"></a>Macro: <strong>EH_TABLES_CAN_BE_READ_ONLY</strong></dt>
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<dd><p>Define this macro to 1 if your target is such that no frame unwind
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information encoding used with non-PIC code will ever require a
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runtime relocation, but the linker may not support merging read-only
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and read-write sections into a single read-write section.
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</p></dd></dl>
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<dl>
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<dt><a name="index-MASK_005fRETURN_005fADDR"></a>Macro: <strong>MASK_RETURN_ADDR</strong></dt>
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<dd><p>An rtx used to mask the return address found via <code>RETURN_ADDR_RTX</code>, so
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that it does not contain any extraneous set bits in it.
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</p></dd></dl>
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<dl>
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<dt><a name="index-DWARF2_005fUNWIND_005fINFO"></a>Macro: <strong>DWARF2_UNWIND_INFO</strong></dt>
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<dd><p>Define this macro to 0 if your target supports DWARF 2 frame unwind
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information, but it does not yet work with exception handling.
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Otherwise, if your target supports this information (if it defines
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<code>INCOMING_RETURN_ADDR_RTX</code> and <code>OBJECT_FORMAT_ELF</code>),
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GCC will provide a default definition of 1.
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</p></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fEXCEPT_005fUNWIND_005fINFO"></a>Common Target Hook: <em>enum unwind_info_type</em> <strong>TARGET_EXCEPT_UNWIND_INFO</strong> <em>(struct gcc_options *<var>opts</var>)</em></dt>
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<dd><p>This hook defines the mechanism that will be used for exception handling
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by the target. If the target has ABI specified unwind tables, the hook
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should return <code>UI_TARGET</code>. If the target is to use the
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<code>setjmp</code>/<code>longjmp</code>-based exception handling scheme, the hook
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should return <code>UI_SJLJ</code>. If the target supports DWARF 2 frame unwind
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information, the hook should return <code>UI_DWARF2</code>.
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</p>
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<p>A target may, if exceptions are disabled, choose to return <code>UI_NONE</code>.
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This may end up simplifying other parts of target-specific code. The
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default implementation of this hook never returns <code>UI_NONE</code>.
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</p>
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<p>Note that the value returned by this hook should be constant. It should
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not depend on anything except the command-line switches described by
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<var>opts</var>. In particular, the
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setting <code>UI_SJLJ</code> must be fixed at compiler start-up as C pre-processor
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macros and builtin functions related to exception handling are set up
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depending on this setting.
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</p>
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<p>The default implementation of the hook first honors the
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<samp>--enable-sjlj-exceptions</samp> configure option, then
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<code>DWARF2_UNWIND_INFO</code>, and finally defaults to <code>UI_SJLJ</code>. If
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<code>DWARF2_UNWIND_INFO</code> depends on command-line options, the target
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must define this hook so that <var>opts</var> is used correctly.
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</p></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fUNWIND_005fTABLES_005fDEFAULT"></a>Common Target Hook: <em>bool</em> <strong>TARGET_UNWIND_TABLES_DEFAULT</strong></dt>
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<dd><p>This variable should be set to <code>true</code> if the target ABI requires unwinding
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tables even when exceptions are not used. It must not be modified by
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command-line option processing.
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</p></dd></dl>
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<dl>
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<dt><a name="index-DONT_005fUSE_005fBUILTIN_005fSETJMP"></a>Macro: <strong>DONT_USE_BUILTIN_SETJMP</strong></dt>
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<dd><p>Define this macro to 1 if the <code>setjmp</code>/<code>longjmp</code>-based scheme
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should use the <code>setjmp</code>/<code>longjmp</code> functions from the C library
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instead of the <code>__builtin_setjmp</code>/<code>__builtin_longjmp</code> machinery.
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</p></dd></dl>
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<dl>
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<dt><a name="index-JMP_005fBUF_005fSIZE"></a>Macro: <strong>JMP_BUF_SIZE</strong></dt>
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<dd><p>This macro has no effect unless <code>DONT_USE_BUILTIN_SETJMP</code> is also
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defined. Define this macro if the default size of <code>jmp_buf</code> buffer
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for the <code>setjmp</code>/<code>longjmp</code>-based exception handling mechanism
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is not large enough, or if it is much too large.
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The default size is <code>FIRST_PSEUDO_REGISTER * sizeof(void *)</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-DWARF_005fCIE_005fDATA_005fALIGNMENT"></a>Macro: <strong>DWARF_CIE_DATA_ALIGNMENT</strong></dt>
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<dd><p>This macro need only be defined if the target might save registers in the
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function prologue at an offset to the stack pointer that is not aligned to
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<code>UNITS_PER_WORD</code>. The definition should be the negative minimum
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alignment if <code>STACK_GROWS_DOWNWARD</code> is true, and the positive
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minimum alignment otherwise. See <a href="SDB-and-DWARF.html#SDB-and-DWARF">SDB and DWARF</a>. Only applicable if
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the target supports DWARF 2 frame unwind information.
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</p></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fTERMINATE_005fDW2_005fEH_005fFRAME_005fINFO"></a>Target Hook: <em>bool</em> <strong>TARGET_TERMINATE_DW2_EH_FRAME_INFO</strong></dt>
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<dd><p>Contains the value true if the target should add a zero word onto the
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end of a Dwarf-2 frame info section when used for exception handling.
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Default value is false if <code>EH_FRAME_SECTION_NAME</code> is defined, and
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true otherwise.
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</p></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fDWARF_005fREGISTER_005fSPAN"></a>Target Hook: <em>rtx</em> <strong>TARGET_DWARF_REGISTER_SPAN</strong> <em>(rtx <var>reg</var>)</em></dt>
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<dd><p>Given a register, this hook should return a parallel of registers to
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represent where to find the register pieces. Define this hook if the
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register and its mode are represented in Dwarf in non-contiguous
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locations, or if the register should be represented in more than one
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register in Dwarf. Otherwise, this hook should return <code>NULL_RTX</code>.
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If not defined, the default is to return <code>NULL_RTX</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fDWARF_005fFRAME_005fREG_005fMODE"></a>Target Hook: <em>machine_mode</em> <strong>TARGET_DWARF_FRAME_REG_MODE</strong> <em>(int <var>regno</var>)</em></dt>
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<dd><p>Given a register, this hook should return the mode which the
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corresponding Dwarf frame register should have. This is normally
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used to return a smaller mode than the raw mode to prevent call
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clobbered parts of a register altering the frame register size
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</p></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fINIT_005fDWARF_005fREG_005fSIZES_005fEXTRA"></a>Target Hook: <em>void</em> <strong>TARGET_INIT_DWARF_REG_SIZES_EXTRA</strong> <em>(tree <var>address</var>)</em></dt>
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<dd><p>If some registers are represented in Dwarf-2 unwind information in
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multiple pieces, define this hook to fill in information about the
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sizes of those pieces in the table used by the unwinder at runtime.
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It will be called by <code>expand_builtin_init_dwarf_reg_sizes</code> after
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filling in a single size corresponding to each hard register;
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<var>address</var> is the address of the table.
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</p></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fASM_005fTTYPE"></a>Target Hook: <em>bool</em> <strong>TARGET_ASM_TTYPE</strong> <em>(rtx <var>sym</var>)</em></dt>
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<dd><p>This hook is used to output a reference from a frame unwinding table to
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the type_info object identified by <var>sym</var>. It should return <code>true</code>
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if the reference was output. Returning <code>false</code> will cause the
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reference to be output using the normal Dwarf2 routines.
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</p></dd></dl>
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<dl>
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<dt><a name="index-TARGET_005fARM_005fEABI_005fUNWINDER"></a>Target Hook: <em>bool</em> <strong>TARGET_ARM_EABI_UNWINDER</strong></dt>
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<dd><p>This flag should be set to <code>true</code> on targets that use an ARM EABI
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based unwinding library, and <code>false</code> on other targets. This effects
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the format of unwinding tables, and how the unwinder in entered after
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running a cleanup. The default is <code>false</code>.
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</p></dd></dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Alignment-Output.html#Alignment-Output" accesskey="n" rel="next">Alignment Output</a>, Previous: <a href="Dispatch-Tables.html#Dispatch-Tables" accesskey="p" rel="prev">Dispatch Tables</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>
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</div>
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</body>
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</html>
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