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292 lines
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292 lines
16 KiB
HTML
4 years ago
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<html lang="en">
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<head>
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<title>File Framework - GNU Compiler Collection (GCC) Internals</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="GNU Compiler Collection (GCC) Internals">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Assembler-Format.html#Assembler-Format" title="Assembler Format">
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<link rel="next" href="Data-Output.html#Data-Output" title="Data Output">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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Copyright (C) 1988-2015 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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<style type="text/css"><!--
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pre.display { font-family:inherit }
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pre.format { font-family:inherit }
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span.sc { font-variant:small-caps }
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span.roman { font-family:serif; font-weight:normal; }
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span.sansserif { font-family:sans-serif; font-weight:normal; }
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--></style>
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</head>
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<body>
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<div class="node">
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<a name="File-Framework"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Data-Output.html#Data-Output">Data Output</a>,
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Up: <a rel="up" accesskey="u" href="Assembler-Format.html#Assembler-Format">Assembler Format</a>
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<hr>
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</div>
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<h4 class="subsection">17.20.1 The Overall Framework of an Assembler File</h4>
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<p><a name="index-assembler-format-4555"></a><a name="index-output-of-assembler-code-4556"></a>
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<!-- prevent bad page break with this line -->
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This describes the overall framework of an assembly file.
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<p><a name="index-default_005ffile_005fstart-4557"></a>
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<div class="defun">
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— Target Hook: void <b>TARGET_ASM_FILE_START</b> (<var>void</var>)<var><a name="index-TARGET_005fASM_005fFILE_005fSTART-4558"></a></var><br>
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<blockquote><p>Output to <code>asm_out_file</code> any text which the assembler expects to
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find at the beginning of a file. The default behavior is controlled
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by two flags, documented below. Unless your target's assembler is
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quite unusual, if you override the default, you should call
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<code>default_file_start</code> at some point in your target hook. This
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lets other target files rely on these variables.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: bool <b>TARGET_ASM_FILE_START_APP_OFF</b><var><a name="index-TARGET_005fASM_005fFILE_005fSTART_005fAPP_005fOFF-4559"></a></var><br>
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<blockquote><p>If this flag is true, the text of the macro <code>ASM_APP_OFF</code> will be
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printed as the very first line in the assembly file, unless
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<samp><span class="option">-fverbose-asm</span></samp> is in effect. (If that macro has been defined
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to the empty string, this variable has no effect.) With the normal
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definition of <code>ASM_APP_OFF</code>, the effect is to notify the GNU
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assembler that it need not bother stripping comments or extra
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whitespace from its input. This allows it to work a bit faster.
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<p>The default is false. You should not set it to true unless you have
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verified that your port does not generate any extra whitespace or
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comments that will cause GAS to issue errors in NO_APP mode.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: bool <b>TARGET_ASM_FILE_START_FILE_DIRECTIVE</b><var><a name="index-TARGET_005fASM_005fFILE_005fSTART_005fFILE_005fDIRECTIVE-4560"></a></var><br>
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<blockquote><p>If this flag is true, <code>output_file_directive</code> will be called
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for the primary source file, immediately after printing
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<code>ASM_APP_OFF</code> (if that is enabled). Most ELF assemblers expect
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this to be done. The default is false.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_ASM_FILE_END</b> (<var>void</var>)<var><a name="index-TARGET_005fASM_005fFILE_005fEND-4561"></a></var><br>
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<blockquote><p>Output to <code>asm_out_file</code> any text which the assembler expects
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to find at the end of a file. The default is to output nothing.
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</p></blockquote></div>
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<div class="defun">
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— Function: void <b>file_end_indicate_exec_stack</b> ()<var><a name="index-file_005fend_005findicate_005fexec_005fstack-4562"></a></var><br>
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<blockquote><p>Some systems use a common convention, the ‘<samp><span class="samp">.note.GNU-stack</span></samp>’
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special section, to indicate whether or not an object file relies on
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the stack being executable. If your system uses this convention, you
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should define <code>TARGET_ASM_FILE_END</code> to this function. If you
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need to do other things in that hook, have your hook function call
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this function.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_ASM_LTO_START</b> (<var>void</var>)<var><a name="index-TARGET_005fASM_005fLTO_005fSTART-4563"></a></var><br>
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<blockquote><p>Output to <code>asm_out_file</code> any text which the assembler expects
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to find at the start of an LTO section. The default is to output
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nothing.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_ASM_LTO_END</b> (<var>void</var>)<var><a name="index-TARGET_005fASM_005fLTO_005fEND-4564"></a></var><br>
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<blockquote><p>Output to <code>asm_out_file</code> any text which the assembler expects
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to find at the end of an LTO section. The default is to output
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nothing.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_ASM_CODE_END</b> (<var>void</var>)<var><a name="index-TARGET_005fASM_005fCODE_005fEND-4565"></a></var><br>
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<blockquote><p>Output to <code>asm_out_file</code> any text which is needed before emitting
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unwind info and debug info at the end of a file. Some targets emit
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here PIC setup thunks that cannot be emitted at the end of file,
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because they couldn't have unwind info then. The default is to output
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nothing.
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</p></blockquote></div>
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<div class="defun">
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— Macro: <b>ASM_COMMENT_START</b><var><a name="index-ASM_005fCOMMENT_005fSTART-4566"></a></var><br>
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<blockquote><p>A C string constant describing how to begin a comment in the target
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assembler language. The compiler assumes that the comment will end at
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the end of the line.
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</p></blockquote></div>
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<div class="defun">
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— Macro: <b>ASM_APP_ON</b><var><a name="index-ASM_005fAPP_005fON-4567"></a></var><br>
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<blockquote><p>A C string constant for text to be output before each <code>asm</code>
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statement or group of consecutive ones. Normally this is
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<code>"#APP"</code>, which is a comment that has no effect on most
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assemblers but tells the GNU assembler that it must check the lines
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that follow for all valid assembler constructs.
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</p></blockquote></div>
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<div class="defun">
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— Macro: <b>ASM_APP_OFF</b><var><a name="index-ASM_005fAPP_005fOFF-4568"></a></var><br>
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<blockquote><p>A C string constant for text to be output after each <code>asm</code>
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statement or group of consecutive ones. Normally this is
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<code>"#NO_APP"</code>, which tells the GNU assembler to resume making the
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time-saving assumptions that are valid for ordinary compiler output.
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</p></blockquote></div>
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<div class="defun">
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— Macro: <b>ASM_OUTPUT_SOURCE_FILENAME</b> (<var>stream, name</var>)<var><a name="index-ASM_005fOUTPUT_005fSOURCE_005fFILENAME-4569"></a></var><br>
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<blockquote><p>A C statement to output COFF information or DWARF debugging information
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which indicates that filename <var>name</var> is the current source file to
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the stdio stream <var>stream</var>.
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<p>This macro need not be defined if the standard form of output
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for the file format in use is appropriate.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_ASM_OUTPUT_SOURCE_FILENAME</b> (<var>FILE *file, const char *name</var>)<var><a name="index-TARGET_005fASM_005fOUTPUT_005fSOURCE_005fFILENAME-4570"></a></var><br>
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<blockquote><p>Output COFF information or DWARF debugging information which indicates that filename <var>name</var> is the current source file to the stdio stream <var>file</var>.
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<p>This target hook need not be defined if the standard form of output for the file format in use is appropriate.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_ASM_OUTPUT_IDENT</b> (<var>const char *name</var>)<var><a name="index-TARGET_005fASM_005fOUTPUT_005fIDENT-4571"></a></var><br>
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<blockquote><p>Output a string based on <var>name</var>, suitable for the ‘<samp><span class="samp">#ident</span></samp>’ directive, or the equivalent directive or pragma in non-C-family languages. If this hook is not defined, nothing is output for the ‘<samp><span class="samp">#ident</span></samp>’ directive.
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</p></blockquote></div>
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<div class="defun">
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— Macro: <b>OUTPUT_QUOTED_STRING</b> (<var>stream, string</var>)<var><a name="index-OUTPUT_005fQUOTED_005fSTRING-4572"></a></var><br>
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<blockquote><p>A C statement to output the string <var>string</var> to the stdio stream
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<var>stream</var>. If you do not call the function <code>output_quoted_string</code>
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in your config files, GCC will only call it to output filenames to
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the assembler source. So you can use it to canonicalize the format
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of the filename using this macro.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_ASM_NAMED_SECTION</b> (<var>const char *name, unsigned int flags, tree decl</var>)<var><a name="index-TARGET_005fASM_005fNAMED_005fSECTION-4573"></a></var><br>
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<blockquote><p>Output assembly directives to switch to section <var>name</var>. The section
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should have attributes as specified by <var>flags</var>, which is a bit mask
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of the <code>SECTION_*</code> flags defined in <samp><span class="file">output.h</span></samp>. If <var>decl</var>
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is non-NULL, it is the <code>VAR_DECL</code> or <code>FUNCTION_DECL</code> with which
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this section is associated.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: section * <b>TARGET_ASM_FUNCTION_SECTION</b> (<var>tree decl, enum node_frequency freq, bool startup, bool exit</var>)<var><a name="index-TARGET_005fASM_005fFUNCTION_005fSECTION-4574"></a></var><br>
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<blockquote><p>Return preferred text (sub)section for function <var>decl</var>.
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Main purpose of this function is to separate cold, normal and hot
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functions. <var>startup</var> is true when function is known to be used only
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at startup (from static constructors or it is <code>main()</code>).
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<var>exit</var> is true when function is known to be used only at exit
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(from static destructors).
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Return NULL if function should go to default text section.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: void <b>TARGET_ASM_FUNCTION_SWITCHED_TEXT_SECTIONS</b> (<var>FILE *file, tree decl, bool new_is_cold</var>)<var><a name="index-TARGET_005fASM_005fFUNCTION_005fSWITCHED_005fTEXT_005fSECTIONS-4575"></a></var><br>
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<blockquote><p>Used by the target to emit any assembler directives or additional labels needed when a function is partitioned between different sections. Output should be written to <var>file</var>. The function decl is available as <var>decl</var> and the new section is `cold' if <var>new_is_cold</var> is <code>true</code>.
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</p></blockquote></div>
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<div class="defun">
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— Common Target Hook: bool <b>TARGET_HAVE_NAMED_SECTIONS</b><var><a name="index-TARGET_005fHAVE_005fNAMED_005fSECTIONS-4576"></a></var><br>
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<blockquote><p>This flag is true if the target supports <code>TARGET_ASM_NAMED_SECTION</code>.
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It must not be modified by command-line option processing.
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</p></blockquote></div>
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<p><a name="TARGET_005fHAVE_005fSWITCHABLE_005fBSS_005fSECTIONS"></a>
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<div class="defun">
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— Target Hook: bool <b>TARGET_HAVE_SWITCHABLE_BSS_SECTIONS</b><var><a name="index-TARGET_005fHAVE_005fSWITCHABLE_005fBSS_005fSECTIONS-4577"></a></var><br>
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<blockquote><p>This flag is true if we can create zeroed data by switching to a BSS
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section and then using <code>ASM_OUTPUT_SKIP</code> to allocate the space.
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This is true on most ELF targets.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: unsigned int <b>TARGET_SECTION_TYPE_FLAGS</b> (<var>tree decl, const char *name, int reloc</var>)<var><a name="index-TARGET_005fSECTION_005fTYPE_005fFLAGS-4578"></a></var><br>
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<blockquote><p>Choose a set of section attributes for use by <code>TARGET_ASM_NAMED_SECTION</code>
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based on a variable or function decl, a section name, and whether or not the
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declaration's initializer may contain runtime relocations. <var>decl</var> may be
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null, in which case read-write data should be assumed.
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<p>The default version of this function handles choosing code vs data,
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read-only vs read-write data, and <code>flag_pic</code>. You should only
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need to override this if your target has special flags that might be
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set via <code>__attribute__</code>.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: int <b>TARGET_ASM_RECORD_GCC_SWITCHES</b> (<var>print_switch_type type, const char *text</var>)<var><a name="index-TARGET_005fASM_005fRECORD_005fGCC_005fSWITCHES-4579"></a></var><br>
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<blockquote><p>Provides the target with the ability to record the gcc command line
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switches that have been passed to the compiler, and options that are
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enabled. The <var>type</var> argument specifies what is being recorded.
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It can take the following values:
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<dl>
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<dt><code>SWITCH_TYPE_PASSED</code><dd><var>text</var> is a command line switch that has been set by the user.
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<br><dt><code>SWITCH_TYPE_ENABLED</code><dd><var>text</var> is an option which has been enabled. This might be as a
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direct result of a command line switch, or because it is enabled by
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default or because it has been enabled as a side effect of a different
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command line switch. For example, the <samp><span class="option">-O2</span></samp> switch enables
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various different individual optimization passes.
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<br><dt><code>SWITCH_TYPE_DESCRIPTIVE</code><dd><var>text</var> is either NULL or some descriptive text which should be
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ignored. If <var>text</var> is NULL then it is being used to warn the
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target hook that either recording is starting or ending. The first
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time <var>type</var> is SWITCH_TYPE_DESCRIPTIVE and <var>text</var> is NULL, the
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warning is for start up and the second time the warning is for
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wind down. This feature is to allow the target hook to make any
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necessary preparations before it starts to record switches and to
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perform any necessary tidying up after it has finished recording
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switches.
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<br><dt><code>SWITCH_TYPE_LINE_START</code><dd>This option can be ignored by this target hook.
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||
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||
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|
<br><dt><code>SWITCH_TYPE_LINE_END</code><dd>This option can be ignored by this target hook.
|
||
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</dl>
|
||
|
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||
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<p>The hook's return value must be zero. Other return values may be
|
||
|
|
supported in the future.
|
||
|
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||
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|
<p>By default this hook is set to NULL, but an example implementation is
|
||
|
|
provided for ELF based targets. Called <var>elf_record_gcc_switches</var>,
|
||
|
|
it records the switches as ASCII text inside a new, string mergeable
|
||
|
|
section in the assembler output file. The name of the new section is
|
||
|
|
provided by the <code>TARGET_ASM_RECORD_GCC_SWITCHES_SECTION</code> target
|
||
|
|
hook.
|
||
|
|
</p></blockquote></div>
|
||
|
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|
||
|
|
<div class="defun">
|
||
|
|
— Target Hook: const char * <b>TARGET_ASM_RECORD_GCC_SWITCHES_SECTION</b><var><a name="index-TARGET_005fASM_005fRECORD_005fGCC_005fSWITCHES_005fSECTION-4580"></a></var><br>
|
||
|
|
<blockquote><p>This is the name of the section that will be created by the example
|
||
|
|
ELF implementation of the <code>TARGET_ASM_RECORD_GCC_SWITCHES</code> target
|
||
|
|
hook.
|
||
|
|
</p></blockquote></div>
|
||
|
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</body></html>
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