294 lines
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HTML
294 lines
12 KiB
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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: Special Accessors</title>
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<meta name="description" content="GNU Compiler Collection (GCC) Internals: Special Accessors">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Flags.html#Flags" rel="next" title="Flags">
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<link href="Accessors.html#Accessors" rel="prev" title="Accessors">
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Special-Accessors"></a>
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<div class="header">
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<p>
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Next: <a href="Flags.html#Flags" accesskey="n" rel="next">Flags</a>, Previous: <a href="Accessors.html#Accessors" accesskey="p" rel="prev">Accessors</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</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="Access-to-Special-Operands"></a>
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<h3 class="section">13.4 Access to Special Operands</h3>
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<a name="index-access-to-special-operands"></a>
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<p>Some RTL nodes have special annotations associated with them.
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</p>
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<dl compact="compact">
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<dt><code>MEM</code></dt>
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<dd><dl compact="compact">
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<dd><a name="index-MEM_005fALIAS_005fSET"></a>
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</dd>
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<dt><code>MEM_ALIAS_SET (<var>x</var>)</code></dt>
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<dd><p>If 0, <var>x</var> is not in any alias set, and may alias anything. Otherwise,
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<var>x</var> can only alias <code>MEM</code>s in a conflicting alias set. This value
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is set in a language-dependent manner in the front-end, and should not be
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altered in the back-end. In some front-ends, these numbers may correspond
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in some way to types, or other language-level entities, but they need not,
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and the back-end makes no such assumptions.
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These set numbers are tested with <code>alias_sets_conflict_p</code>.
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</p>
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<a name="index-MEM_005fEXPR"></a>
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</dd>
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<dt><code>MEM_EXPR (<var>x</var>)</code></dt>
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<dd><p>If this register is known to hold the value of some user-level
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declaration, this is that tree node. It may also be a
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<code>COMPONENT_REF</code>, in which case this is some field reference,
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and <code>TREE_OPERAND (<var>x</var>, 0)</code> contains the declaration,
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or another <code>COMPONENT_REF</code>, or null if there is no compile-time
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object associated with the reference.
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</p>
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<a name="index-MEM_005fOFFSET_005fKNOWN_005fP"></a>
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</dd>
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<dt><code>MEM_OFFSET_KNOWN_P (<var>x</var>)</code></dt>
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<dd><p>True if the offset of the memory reference from <code>MEM_EXPR</code> is known.
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‘<samp>MEM_OFFSET (<var>x</var>)</samp>’ provides the offset if so.
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</p>
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<a name="index-MEM_005fOFFSET"></a>
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</dd>
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<dt><code>MEM_OFFSET (<var>x</var>)</code></dt>
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<dd><p>The offset from the start of <code>MEM_EXPR</code>. The value is only valid if
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‘<samp>MEM_OFFSET_KNOWN_P (<var>x</var>)</samp>’ is true.
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</p>
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<a name="index-MEM_005fSIZE_005fKNOWN_005fP"></a>
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</dd>
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<dt><code>MEM_SIZE_KNOWN_P (<var>x</var>)</code></dt>
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<dd><p>True if the size of the memory reference is known.
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‘<samp>MEM_SIZE (<var>x</var>)</samp>’ provides its size if so.
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</p>
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<a name="index-MEM_005fSIZE"></a>
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</dd>
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<dt><code>MEM_SIZE (<var>x</var>)</code></dt>
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<dd><p>The size in bytes of the memory reference.
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This is mostly relevant for <code>BLKmode</code> references as otherwise
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the size is implied by the mode. The value is only valid if
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‘<samp>MEM_SIZE_KNOWN_P (<var>x</var>)</samp>’ is true.
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</p>
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<a name="index-MEM_005fALIGN"></a>
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</dd>
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<dt><code>MEM_ALIGN (<var>x</var>)</code></dt>
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<dd><p>The known alignment in bits of the memory reference.
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</p>
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<a name="index-MEM_005fADDR_005fSPACE"></a>
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</dd>
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<dt><code>MEM_ADDR_SPACE (<var>x</var>)</code></dt>
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<dd><p>The address space of the memory reference. This will commonly be zero
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for the generic address space.
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</p></dd>
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</dl>
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</dd>
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<dt><code>REG</code></dt>
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<dd><dl compact="compact">
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<dd><a name="index-ORIGINAL_005fREGNO"></a>
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</dd>
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<dt><code>ORIGINAL_REGNO (<var>x</var>)</code></dt>
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<dd><p>This field holds the number the register “originally” had; for a
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pseudo register turned into a hard reg this will hold the old pseudo
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register number.
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</p>
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<a name="index-REG_005fEXPR"></a>
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</dd>
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<dt><code>REG_EXPR (<var>x</var>)</code></dt>
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<dd><p>If this register is known to hold the value of some user-level
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declaration, this is that tree node.
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</p>
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<a name="index-REG_005fOFFSET"></a>
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</dd>
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<dt><code>REG_OFFSET (<var>x</var>)</code></dt>
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<dd><p>If this register is known to hold the value of some user-level
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declaration, this is the offset into that logical storage.
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</p></dd>
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</dl>
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</dd>
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<dt><code>SYMBOL_REF</code></dt>
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<dd><dl compact="compact">
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<dd><a name="index-SYMBOL_005fREF_005fDECL"></a>
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</dd>
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<dt><code>SYMBOL_REF_DECL (<var>x</var>)</code></dt>
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<dd><p>If the <code>symbol_ref</code> <var>x</var> was created for a <code>VAR_DECL</code> or
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a <code>FUNCTION_DECL</code>, that tree is recorded here. If this value is
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null, then <var>x</var> was created by back end code generation routines,
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and there is no associated front end symbol table entry.
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</p>
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<p><code>SYMBOL_REF_DECL</code> may also point to a tree of class <code>'c'</code>,
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that is, some sort of constant. In this case, the <code>symbol_ref</code>
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is an entry in the per-file constant pool; again, there is no associated
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front end symbol table entry.
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</p>
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<a name="index-SYMBOL_005fREF_005fCONSTANT"></a>
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</dd>
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<dt><code>SYMBOL_REF_CONSTANT (<var>x</var>)</code></dt>
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<dd><p>If ‘<samp>CONSTANT_POOL_ADDRESS_P (<var>x</var>)</samp>’ is true, this is the constant
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pool entry for <var>x</var>. It is null otherwise.
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</p>
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<a name="index-SYMBOL_005fREF_005fDATA"></a>
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</dd>
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<dt><code>SYMBOL_REF_DATA (<var>x</var>)</code></dt>
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<dd><p>A field of opaque type used to store <code>SYMBOL_REF_DECL</code> or
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<code>SYMBOL_REF_CONSTANT</code>.
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</p>
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<a name="index-SYMBOL_005fREF_005fFLAGS"></a>
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</dd>
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<dt><code>SYMBOL_REF_FLAGS (<var>x</var>)</code></dt>
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<dd><p>In a <code>symbol_ref</code>, this is used to communicate various predicates
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about the symbol. Some of these are common enough to be computed by
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common code, some are specific to the target. The common bits are:
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</p>
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<dl compact="compact">
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<dd><a name="index-SYMBOL_005fREF_005fFUNCTION_005fP"></a>
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<a name="index-SYMBOL_005fFLAG_005fFUNCTION"></a>
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</dd>
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<dt><code>SYMBOL_FLAG_FUNCTION</code></dt>
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<dd><p>Set if the symbol refers to a function.
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</p>
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<a name="index-SYMBOL_005fREF_005fLOCAL_005fP"></a>
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<a name="index-SYMBOL_005fFLAG_005fLOCAL"></a>
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</dd>
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<dt><code>SYMBOL_FLAG_LOCAL</code></dt>
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<dd><p>Set if the symbol is local to this “module”.
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See <code>TARGET_BINDS_LOCAL_P</code>.
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</p>
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<a name="index-SYMBOL_005fREF_005fEXTERNAL_005fP"></a>
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<a name="index-SYMBOL_005fFLAG_005fEXTERNAL"></a>
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</dd>
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<dt><code>SYMBOL_FLAG_EXTERNAL</code></dt>
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<dd><p>Set if this symbol is not defined in this translation unit.
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Note that this is not the inverse of <code>SYMBOL_FLAG_LOCAL</code>.
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</p>
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<a name="index-SYMBOL_005fREF_005fSMALL_005fP"></a>
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<a name="index-SYMBOL_005fFLAG_005fSMALL"></a>
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</dd>
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<dt><code>SYMBOL_FLAG_SMALL</code></dt>
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<dd><p>Set if the symbol is located in the small data section.
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See <code>TARGET_IN_SMALL_DATA_P</code>.
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</p>
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<a name="index-SYMBOL_005fFLAG_005fTLS_005fSHIFT"></a>
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<a name="index-SYMBOL_005fREF_005fTLS_005fMODEL"></a>
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</dd>
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<dt><code>SYMBOL_REF_TLS_MODEL (<var>x</var>)</code></dt>
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<dd><p>This is a multi-bit field accessor that returns the <code>tls_model</code>
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to be used for a thread-local storage symbol. It returns zero for
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non-thread-local symbols.
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</p>
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<a name="index-SYMBOL_005fREF_005fHAS_005fBLOCK_005fINFO_005fP"></a>
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<a name="index-SYMBOL_005fFLAG_005fHAS_005fBLOCK_005fINFO"></a>
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</dd>
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<dt><code>SYMBOL_FLAG_HAS_BLOCK_INFO</code></dt>
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<dd><p>Set if the symbol has <code>SYMBOL_REF_BLOCK</code> and
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<code>SYMBOL_REF_BLOCK_OFFSET</code> fields.
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</p>
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<a name="index-SYMBOL_005fREF_005fANCHOR_005fP"></a>
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<a name="index-SYMBOL_005fFLAG_005fANCHOR"></a>
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<a name="index-_002dfsection_002danchors"></a>
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</dd>
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<dt><code>SYMBOL_FLAG_ANCHOR</code></dt>
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<dd><p>Set if the symbol is used as a section anchor. “Section anchors”
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are symbols that have a known position within an <code>object_block</code>
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and that can be used to access nearby members of that block.
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They are used to implement <samp>-fsection-anchors</samp>.
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</p>
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<p>If this flag is set, then <code>SYMBOL_FLAG_HAS_BLOCK_INFO</code> will be too.
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</p></dd>
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</dl>
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<p>Bits beginning with <code>SYMBOL_FLAG_MACH_DEP</code> are available for
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the target’s use.
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</p></dd>
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</dl>
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<a name="index-SYMBOL_005fREF_005fBLOCK"></a>
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</dd>
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<dt><code>SYMBOL_REF_BLOCK (<var>x</var>)</code></dt>
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<dd><p>If ‘<samp>SYMBOL_REF_HAS_BLOCK_INFO_P (<var>x</var>)</samp>’, this is the
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‘<samp>object_block</samp>’ structure to which the symbol belongs,
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or <code>NULL</code> if it has not been assigned a block.
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</p>
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<a name="index-SYMBOL_005fREF_005fBLOCK_005fOFFSET"></a>
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</dd>
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<dt><code>SYMBOL_REF_BLOCK_OFFSET (<var>x</var>)</code></dt>
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<dd><p>If ‘<samp>SYMBOL_REF_HAS_BLOCK_INFO_P (<var>x</var>)</samp>’, this is the offset of <var>x</var>
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from the first object in ‘<samp>SYMBOL_REF_BLOCK (<var>x</var>)</samp>’. The value is
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negative if <var>x</var> has not yet been assigned to a block, or it has not
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been given an offset within that block.
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</p></dd>
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</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="Flags.html#Flags" accesskey="n" rel="next">Flags</a>, Previous: <a href="Accessors.html#Accessors" accesskey="p" rel="prev">Accessors</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</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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