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<title>GNU Compiler Collection (GCC) Internals: Flags</title>
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<a name="Flags"></a>
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<div class="header">
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<p>
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Next: <a href="Machine-Modes.html#Machine-Modes" accesskey="n" rel="next">Machine Modes</a>, Previous: <a href="Special-Accessors.html#Special-Accessors" accesskey="p" rel="prev">Special 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="Flags-in-an-RTL-Expression"></a>
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<h3 class="section">13.5 Flags in an RTL Expression</h3>
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<a name="index-flags-in-RTL-expression"></a>
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<p>RTL expressions contain several flags (one-bit bit-fields)
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that are used in certain types of expression. Most often they
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are accessed with the following macros, which expand into lvalues.
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</p>
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<dl compact="compact">
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<dd><a name="index-CONSTANT_005fPOOL_005fADDRESS_005fP"></a>
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<a name="index-symbol_005fref-and-_002fu"></a>
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<a name="index-unchanging_002c-in-symbol_005fref"></a>
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</dd>
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<dt><code>CONSTANT_POOL_ADDRESS_P (<var>x</var>)</code></dt>
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<dd><p>Nonzero in a <code>symbol_ref</code> if it refers to part of the current
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function’s constant pool. For most targets these addresses are in a
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<code>.rodata</code> section entirely separate from the function, but for
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some targets the addresses are close to the beginning of the function.
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In either case GCC assumes these addresses can be addressed directly,
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perhaps with the help of base registers.
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Stored in the <code>unchanging</code> field and printed as ‘<samp>/u</samp>’.
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</p>
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<a name="index-RTL_005fCONST_005fCALL_005fP"></a>
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<a name="index-call_005finsn-and-_002fu"></a>
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<a name="index-unchanging_002c-in-call_005finsn"></a>
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</dd>
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<dt><code>RTL_CONST_CALL_P (<var>x</var>)</code></dt>
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<dd><p>In a <code>call_insn</code> indicates that the insn represents a call to a
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const function. Stored in the <code>unchanging</code> field and printed as
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‘<samp>/u</samp>’.
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</p>
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<a name="index-RTL_005fPURE_005fCALL_005fP"></a>
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<a name="index-call_005finsn-and-_002fi"></a>
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<a name="index-return_005fval_002c-in-call_005finsn"></a>
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</dd>
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<dt><code>RTL_PURE_CALL_P (<var>x</var>)</code></dt>
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<dd><p>In a <code>call_insn</code> indicates that the insn represents a call to a
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pure function. Stored in the <code>return_val</code> field and printed as
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‘<samp>/i</samp>’.
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</p>
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<a name="index-RTL_005fCONST_005fOR_005fPURE_005fCALL_005fP"></a>
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<a name="index-call_005finsn-and-_002fu-or-_002fi"></a>
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</dd>
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<dt><code>RTL_CONST_OR_PURE_CALL_P (<var>x</var>)</code></dt>
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<dd><p>In a <code>call_insn</code>, true if <code>RTL_CONST_CALL_P</code> or
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<code>RTL_PURE_CALL_P</code> is true.
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</p>
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<a name="index-RTL_005fLOOPING_005fCONST_005fOR_005fPURE_005fCALL_005fP"></a>
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<a name="index-call_005finsn-and-_002fc"></a>
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<a name="index-call_002c-in-call_005finsn"></a>
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</dd>
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<dt><code>RTL_LOOPING_CONST_OR_PURE_CALL_P (<var>x</var>)</code></dt>
|
<dd><p>In a <code>call_insn</code> indicates that the insn represents a possibly
|
infinite looping call to a const or pure function. Stored in the
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<code>call</code> field and printed as ‘<samp>/c</samp>’. Only true if one of
|
<code>RTL_CONST_CALL_P</code> or <code>RTL_PURE_CALL_P</code> is true.
|
</p>
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<a name="index-INSN_005fANNULLED_005fBRANCH_005fP"></a>
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<a name="index-jump_005finsn-and-_002fu"></a>
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<a name="index-call_005finsn-and-_002fu-1"></a>
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<a name="index-insn-and-_002fu"></a>
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<a name="index-unchanging_002c-in-jump_005finsn_002c-call_005finsn-and-insn"></a>
|
</dd>
|
<dt><code>INSN_ANNULLED_BRANCH_P (<var>x</var>)</code></dt>
|
<dd><p>In a <code>jump_insn</code>, <code>call_insn</code>, or <code>insn</code> indicates
|
that the branch is an annulling one. See the discussion under
|
<code>sequence</code> below. Stored in the <code>unchanging</code> field and
|
printed as ‘<samp>/u</samp>’.
|
</p>
|
<a name="index-INSN_005fDELETED_005fP"></a>
|
<a name="index-insn-and-_002fv"></a>
|
<a name="index-call_005finsn-and-_002fv"></a>
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<a name="index-jump_005finsn-and-_002fv"></a>
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<a name="index-code_005flabel-and-_002fv"></a>
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<a name="index-jump_005ftable_005fdata-and-_002fv"></a>
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<a name="index-barrier-and-_002fv"></a>
|
<a name="index-note-and-_002fv"></a>
|
<a name="index-volatil_002c-in-insn_002c-call_005finsn_002c-jump_005finsn_002c-code_005flabel_002c-jump_005ftable_005fdata_002c-barrier_002c-and-note"></a>
|
</dd>
|
<dt><code>INSN_DELETED_P (<var>x</var>)</code></dt>
|
<dd><p>In an <code>insn</code>, <code>call_insn</code>, <code>jump_insn</code>, <code>code_label</code>,
|
<code>jump_table_data</code>, <code>barrier</code>, or <code>note</code>,
|
nonzero if the insn has been deleted. Stored in the
|
<code>volatil</code> field and printed as ‘<samp>/v</samp>’.
|
</p>
|
<a name="index-INSN_005fFROM_005fTARGET_005fP"></a>
|
<a name="index-insn-and-_002fs"></a>
|
<a name="index-jump_005finsn-and-_002fs"></a>
|
<a name="index-call_005finsn-and-_002fs"></a>
|
<a name="index-in_005fstruct_002c-in-insn-and-jump_005finsn-and-call_005finsn"></a>
|
</dd>
|
<dt><code>INSN_FROM_TARGET_P (<var>x</var>)</code></dt>
|
<dd><p>In an <code>insn</code> or <code>jump_insn</code> or <code>call_insn</code> in a delay
|
slot of a branch, indicates that the insn
|
is from the target of the branch. If the branch insn has
|
<code>INSN_ANNULLED_BRANCH_P</code> set, this insn will only be executed if
|
the branch is taken. For annulled branches with
|
<code>INSN_FROM_TARGET_P</code> clear, the insn will be executed only if the
|
branch is not taken. When <code>INSN_ANNULLED_BRANCH_P</code> is not set,
|
this insn will always be executed. Stored in the <code>in_struct</code>
|
field and printed as ‘<samp>/s</samp>’.
|
</p>
|
<a name="index-LABEL_005fPRESERVE_005fP"></a>
|
<a name="index-code_005flabel-and-_002fi"></a>
|
<a name="index-note-and-_002fi"></a>
|
<a name="index-in_005fstruct_002c-in-code_005flabel-and-note"></a>
|
</dd>
|
<dt><code>LABEL_PRESERVE_P (<var>x</var>)</code></dt>
|
<dd><p>In a <code>code_label</code> or <code>note</code>, indicates that the label is referenced by
|
code or data not visible to the RTL of a given function.
|
Labels referenced by a non-local goto will have this bit set. Stored
|
in the <code>in_struct</code> field and printed as ‘<samp>/s</samp>’.
|
</p>
|
<a name="index-LABEL_005fREF_005fNONLOCAL_005fP"></a>
|
<a name="index-label_005fref-and-_002fv"></a>
|
<a name="index-reg_005flabel-and-_002fv"></a>
|
<a name="index-volatil_002c-in-label_005fref-and-reg_005flabel"></a>
|
</dd>
|
<dt><code>LABEL_REF_NONLOCAL_P (<var>x</var>)</code></dt>
|
<dd><p>In <code>label_ref</code> and <code>reg_label</code> expressions, nonzero if this is
|
a reference to a non-local label.
|
Stored in the <code>volatil</code> field and printed as ‘<samp>/v</samp>’.
|
</p>
|
<a name="index-MEM_005fKEEP_005fALIAS_005fSET_005fP"></a>
|
<a name="index-mem-and-_002fj"></a>
|
<a name="index-jump_002c-in-mem"></a>
|
</dd>
|
<dt><code>MEM_KEEP_ALIAS_SET_P (<var>x</var>)</code></dt>
|
<dd><p>In <code>mem</code> expressions, 1 if we should keep the alias set for this
|
mem unchanged when we access a component. Set to 1, for example, when we
|
are already in a non-addressable component of an aggregate.
|
Stored in the <code>jump</code> field and printed as ‘<samp>/j</samp>’.
|
</p>
|
<a name="index-MEM_005fVOLATILE_005fP"></a>
|
<a name="index-mem-and-_002fv"></a>
|
<a name="index-asm_005finput-and-_002fv"></a>
|
<a name="index-asm_005foperands-and-_002fv"></a>
|
<a name="index-volatil_002c-in-mem_002c-asm_005foperands_002c-and-asm_005finput"></a>
|
</dd>
|
<dt><code>MEM_VOLATILE_P (<var>x</var>)</code></dt>
|
<dd><p>In <code>mem</code>, <code>asm_operands</code>, and <code>asm_input</code> expressions,
|
nonzero for volatile memory references.
|
Stored in the <code>volatil</code> field and printed as ‘<samp>/v</samp>’.
|
</p>
|
<a name="index-MEM_005fNOTRAP_005fP"></a>
|
<a name="index-mem-and-_002fc"></a>
|
<a name="index-call_002c-in-mem"></a>
|
</dd>
|
<dt><code>MEM_NOTRAP_P (<var>x</var>)</code></dt>
|
<dd><p>In <code>mem</code>, nonzero for memory references that will not trap.
|
Stored in the <code>call</code> field and printed as ‘<samp>/c</samp>’.
|
</p>
|
<a name="index-MEM_005fPOINTER"></a>
|
<a name="index-mem-and-_002ff"></a>
|
<a name="index-frame_005frelated_002c-in-mem"></a>
|
</dd>
|
<dt><code>MEM_POINTER (<var>x</var>)</code></dt>
|
<dd><p>Nonzero in a <code>mem</code> if the memory reference holds a pointer.
|
Stored in the <code>frame_related</code> field and printed as ‘<samp>/f</samp>’.
|
</p>
|
<a name="index-REG_005fFUNCTION_005fVALUE_005fP"></a>
|
<a name="index-reg-and-_002fi"></a>
|
<a name="index-return_005fval_002c-in-reg"></a>
|
</dd>
|
<dt><code>REG_FUNCTION_VALUE_P (<var>x</var>)</code></dt>
|
<dd><p>Nonzero in a <code>reg</code> if it is the place in which this function’s
|
value is going to be returned. (This happens only in a hard
|
register.) Stored in the <code>return_val</code> field and printed as
|
‘<samp>/i</samp>’.
|
</p>
|
<a name="index-REG_005fPOINTER"></a>
|
<a name="index-reg-and-_002ff"></a>
|
<a name="index-frame_005frelated_002c-in-reg"></a>
|
</dd>
|
<dt><code>REG_POINTER (<var>x</var>)</code></dt>
|
<dd><p>Nonzero in a <code>reg</code> if the register holds a pointer. Stored in the
|
<code>frame_related</code> field and printed as ‘<samp>/f</samp>’.
|
</p>
|
<a name="index-REG_005fUSERVAR_005fP"></a>
|
<a name="index-reg-and-_002fv"></a>
|
<a name="index-volatil_002c-in-reg"></a>
|
</dd>
|
<dt><code>REG_USERVAR_P (<var>x</var>)</code></dt>
|
<dd><p>In a <code>reg</code>, nonzero if it corresponds to a variable present in
|
the user’s source code. Zero for temporaries generated internally by
|
the compiler. Stored in the <code>volatil</code> field and printed as
|
‘<samp>/v</samp>’.
|
</p>
|
<p>The same hard register may be used also for collecting the values of
|
functions called by this one, but <code>REG_FUNCTION_VALUE_P</code> is zero
|
in this kind of use.
|
</p>
|
<a name="index-RTX_005fFRAME_005fRELATED_005fP"></a>
|
<a name="index-insn-and-_002ff"></a>
|
<a name="index-call_005finsn-and-_002ff"></a>
|
<a name="index-jump_005finsn-and-_002ff"></a>
|
<a name="index-barrier-and-_002ff"></a>
|
<a name="index-set-and-_002ff"></a>
|
<a name="index-frame_005frelated_002c-in-insn_002c-call_005finsn_002c-jump_005finsn_002c-barrier_002c-and-set"></a>
|
</dd>
|
<dt><code>RTX_FRAME_RELATED_P (<var>x</var>)</code></dt>
|
<dd><p>Nonzero in an <code>insn</code>, <code>call_insn</code>, <code>jump_insn</code>,
|
<code>barrier</code>, or <code>set</code> which is part of a function prologue
|
and sets the stack pointer, sets the frame pointer, or saves a register.
|
This flag should also be set on an instruction that sets up a temporary
|
register to use in place of the frame pointer.
|
Stored in the <code>frame_related</code> field and printed as ‘<samp>/f</samp>’.
|
</p>
|
<p>In particular, on RISC targets where there are limits on the sizes of
|
immediate constants, it is sometimes impossible to reach the register
|
save area directly from the stack pointer. In that case, a temporary
|
register is used that is near enough to the register save area, and the
|
Canonical Frame Address, i.e., DWARF2’s logical frame pointer, register
|
must (temporarily) be changed to be this temporary register. So, the
|
instruction that sets this temporary register must be marked as
|
<code>RTX_FRAME_RELATED_P</code>.
|
</p>
|
<p>If the marked instruction is overly complex (defined in terms of what
|
<code>dwarf2out_frame_debug_expr</code> can handle), you will also have to
|
create a <code>REG_FRAME_RELATED_EXPR</code> note and attach it to the
|
instruction. This note should contain a simple expression of the
|
computation performed by this instruction, i.e., one that
|
<code>dwarf2out_frame_debug_expr</code> can handle.
|
</p>
|
<p>This flag is required for exception handling support on targets with RTL
|
prologues.
|
</p>
|
<a name="index-MEM_005fREADONLY_005fP"></a>
|
<a name="index-mem-and-_002fu"></a>
|
<a name="index-unchanging_002c-in-mem"></a>
|
</dd>
|
<dt><code>MEM_READONLY_P (<var>x</var>)</code></dt>
|
<dd><p>Nonzero in a <code>mem</code>, if the memory is statically allocated and read-only.
|
</p>
|
<p>Read-only in this context means never modified during the lifetime of the
|
program, not necessarily in ROM or in write-disabled pages. A common
|
example of the later is a shared library’s global offset table. This
|
table is initialized by the runtime loader, so the memory is technically
|
writable, but after control is transferred from the runtime loader to the
|
application, this memory will never be subsequently modified.
|
</p>
|
<p>Stored in the <code>unchanging</code> field and printed as ‘<samp>/u</samp>’.
|
</p>
|
<a name="index-SCHED_005fGROUP_005fP"></a>
|
<a name="index-insn-and-_002fs-1"></a>
|
<a name="index-call_005finsn-and-_002fs-1"></a>
|
<a name="index-jump_005finsn-and-_002fs-1"></a>
|
<a name="index-jump_005ftable_005fdata-and-_002fs"></a>
|
<a name="index-in_005fstruct_002c-in-insn_002c-call_005finsn_002c-jump_005finsn-and-jump_005ftable_005fdata"></a>
|
</dd>
|
<dt><code>SCHED_GROUP_P (<var>x</var>)</code></dt>
|
<dd><p>During instruction scheduling, in an <code>insn</code>, <code>call_insn</code>,
|
<code>jump_insn</code> or <code>jump_table_data</code>, indicates that the
|
previous insn must be scheduled together with this insn. This is used to
|
ensure that certain groups of instructions will not be split up by the
|
instruction scheduling pass, for example, <code>use</code> insns before
|
a <code>call_insn</code> may not be separated from the <code>call_insn</code>.
|
Stored in the <code>in_struct</code> field and printed as ‘<samp>/s</samp>’.
|
</p>
|
<a name="index-SET_005fIS_005fRETURN_005fP"></a>
|
<a name="index-insn-and-_002fj"></a>
|
<a name="index-jump_002c-in-insn"></a>
|
</dd>
|
<dt><code>SET_IS_RETURN_P (<var>x</var>)</code></dt>
|
<dd><p>For a <code>set</code>, nonzero if it is for a return.
|
Stored in the <code>jump</code> field and printed as ‘<samp>/j</samp>’.
|
</p>
|
<a name="index-SIBLING_005fCALL_005fP"></a>
|
<a name="index-call_005finsn-and-_002fj"></a>
|
<a name="index-jump_002c-in-call_005finsn"></a>
|
</dd>
|
<dt><code>SIBLING_CALL_P (<var>x</var>)</code></dt>
|
<dd><p>For a <code>call_insn</code>, nonzero if the insn is a sibling call.
|
Stored in the <code>jump</code> field and printed as ‘<samp>/j</samp>’.
|
</p>
|
<a name="index-STRING_005fPOOL_005fADDRESS_005fP"></a>
|
<a name="index-symbol_005fref-and-_002ff"></a>
|
<a name="index-frame_005frelated_002c-in-symbol_005fref"></a>
|
</dd>
|
<dt><code>STRING_POOL_ADDRESS_P (<var>x</var>)</code></dt>
|
<dd><p>For a <code>symbol_ref</code> expression, nonzero if it addresses this function’s
|
string constant pool.
|
Stored in the <code>frame_related</code> field and printed as ‘<samp>/f</samp>’.
|
</p>
|
<a name="index-SUBREG_005fPROMOTED_005fUNSIGNED_005fP"></a>
|
<a name="index-subreg-and-_002fu-and-_002fv"></a>
|
<a name="index-unchanging_002c-in-subreg"></a>
|
<a name="index-volatil_002c-in-subreg"></a>
|
</dd>
|
<dt><code>SUBREG_PROMOTED_UNSIGNED_P (<var>x</var>)</code></dt>
|
<dd><p>Returns a value greater then zero for a <code>subreg</code> that has
|
<code>SUBREG_PROMOTED_VAR_P</code> nonzero if the object being referenced is kept
|
zero-extended, zero if it is kept sign-extended, and less then zero if it is
|
extended some other way via the <code>ptr_extend</code> instruction.
|
Stored in the <code>unchanging</code>
|
field and <code>volatil</code> field, printed as ‘<samp>/u</samp>’ and ‘<samp>/v</samp>’.
|
This macro may only be used to get the value it may not be used to change
|
the value. Use <code>SUBREG_PROMOTED_UNSIGNED_SET</code> to change the value.
|
</p>
|
<a name="index-SUBREG_005fPROMOTED_005fUNSIGNED_005fSET"></a>
|
<a name="index-subreg-and-_002fu"></a>
|
<a name="index-unchanging_002c-in-subreg-1"></a>
|
<a name="index-volatil_002c-in-subreg-1"></a>
|
</dd>
|
<dt><code>SUBREG_PROMOTED_UNSIGNED_SET (<var>x</var>)</code></dt>
|
<dd><p>Set the <code>unchanging</code> and <code>volatil</code> fields in a <code>subreg</code>
|
to reflect zero, sign, or other extension. If <code>volatil</code> is
|
zero, then <code>unchanging</code> as nonzero means zero extension and as
|
zero means sign extension. If <code>volatil</code> is nonzero then some
|
other type of extension was done via the <code>ptr_extend</code> instruction.
|
</p>
|
<a name="index-SUBREG_005fPROMOTED_005fVAR_005fP"></a>
|
<a name="index-subreg-and-_002fs"></a>
|
<a name="index-in_005fstruct_002c-in-subreg"></a>
|
</dd>
|
<dt><code>SUBREG_PROMOTED_VAR_P (<var>x</var>)</code></dt>
|
<dd><p>Nonzero in a <code>subreg</code> if it was made when accessing an object that
|
was promoted to a wider mode in accord with the <code>PROMOTED_MODE</code> machine
|
description macro (see <a href="Storage-Layout.html#Storage-Layout">Storage Layout</a>). In this case, the mode of
|
the <code>subreg</code> is the declared mode of the object and the mode of
|
<code>SUBREG_REG</code> is the mode of the register that holds the object.
|
Promoted variables are always either sign- or zero-extended to the wider
|
mode on every assignment. Stored in the <code>in_struct</code> field and
|
printed as ‘<samp>/s</samp>’.
|
</p>
|
<a name="index-SYMBOL_005fREF_005fUSED"></a>
|
<a name="index-used_002c-in-symbol_005fref"></a>
|
</dd>
|
<dt><code>SYMBOL_REF_USED (<var>x</var>)</code></dt>
|
<dd><p>In a <code>symbol_ref</code>, indicates that <var>x</var> has been used. This is
|
normally only used to ensure that <var>x</var> is only declared external
|
once. Stored in the <code>used</code> field.
|
</p>
|
<a name="index-SYMBOL_005fREF_005fWEAK"></a>
|
<a name="index-symbol_005fref-and-_002fi"></a>
|
<a name="index-return_005fval_002c-in-symbol_005fref"></a>
|
</dd>
|
<dt><code>SYMBOL_REF_WEAK (<var>x</var>)</code></dt>
|
<dd><p>In a <code>symbol_ref</code>, indicates that <var>x</var> has been declared weak.
|
Stored in the <code>return_val</code> field and printed as ‘<samp>/i</samp>’.
|
</p>
|
<a name="index-SYMBOL_005fREF_005fFLAG"></a>
|
<a name="index-symbol_005fref-and-_002fv"></a>
|
<a name="index-volatil_002c-in-symbol_005fref"></a>
|
</dd>
|
<dt><code>SYMBOL_REF_FLAG (<var>x</var>)</code></dt>
|
<dd><p>In a <code>symbol_ref</code>, this is used as a flag for machine-specific purposes.
|
Stored in the <code>volatil</code> field and printed as ‘<samp>/v</samp>’.
|
</p>
|
<p>Most uses of <code>SYMBOL_REF_FLAG</code> are historic and may be subsumed
|
by <code>SYMBOL_REF_FLAGS</code>. Certainly use of <code>SYMBOL_REF_FLAGS</code>
|
is mandatory if the target requires more than one bit of storage.
|
</p>
|
<a name="index-PREFETCH_005fSCHEDULE_005fBARRIER_005fP"></a>
|
<a name="index-prefetch-and-_002fv"></a>
|
<a name="index-volatile_002c-in-prefetch"></a>
|
</dd>
|
<dt><code>PREFETCH_SCHEDULE_BARRIER_P (<var>x</var>)</code></dt>
|
<dd><p>In a <code>prefetch</code>, indicates that the prefetch is a scheduling barrier.
|
No other INSNs will be moved over it.
|
Stored in the <code>volatil</code> field and printed as ‘<samp>/v</samp>’.
|
</p></dd>
|
</dl>
|
|
<p>These are the fields to which the above macros refer:
|
</p>
|
<dl compact="compact">
|
<dd><a name="index-call"></a>
|
<a name="index-_002fc-in-RTL-dump"></a>
|
</dd>
|
<dt><code>call</code></dt>
|
<dd><p>In a <code>mem</code>, 1 means that the memory reference will not trap.
|
</p>
|
<p>In a <code>call</code>, 1 means that this pure or const call may possibly
|
infinite loop.
|
</p>
|
<p>In an RTL dump, this flag is represented as ‘<samp>/c</samp>’.
|
</p>
|
<a name="index-frame_005frelated"></a>
|
<a name="index-_002ff-in-RTL-dump"></a>
|
</dd>
|
<dt><code>frame_related</code></dt>
|
<dd><p>In an <code>insn</code> or <code>set</code> expression, 1 means that it is part of
|
a function prologue and sets the stack pointer, sets the frame pointer,
|
saves a register, or sets up a temporary register to use in place of the
|
frame pointer.
|
</p>
|
<p>In <code>reg</code> expressions, 1 means that the register holds a pointer.
|
</p>
|
<p>In <code>mem</code> expressions, 1 means that the memory reference holds a pointer.
|
</p>
|
<p>In <code>symbol_ref</code> expressions, 1 means that the reference addresses
|
this function’s string constant pool.
|
</p>
|
<p>In an RTL dump, this flag is represented as ‘<samp>/f</samp>’.
|
</p>
|
<a name="index-in_005fstruct"></a>
|
<a name="index-_002fs-in-RTL-dump"></a>
|
</dd>
|
<dt><code>in_struct</code></dt>
|
<dd><p>In <code>reg</code> expressions, it is 1 if the register has its entire life
|
contained within the test expression of some loop.
|
</p>
|
<p>In <code>subreg</code> expressions, 1 means that the <code>subreg</code> is accessing
|
an object that has had its mode promoted from a wider mode.
|
</p>
|
<p>In <code>label_ref</code> expressions, 1 means that the referenced label is
|
outside the innermost loop containing the insn in which the <code>label_ref</code>
|
was found.
|
</p>
|
<p>In <code>code_label</code> expressions, it is 1 if the label may never be deleted.
|
This is used for labels which are the target of non-local gotos. Such a
|
label that would have been deleted is replaced with a <code>note</code> of type
|
<code>NOTE_INSN_DELETED_LABEL</code>.
|
</p>
|
<p>In an <code>insn</code> during dead-code elimination, 1 means that the insn is
|
dead code.
|
</p>
|
<p>In an <code>insn</code> or <code>jump_insn</code> during reorg for an insn in the
|
delay slot of a branch,
|
1 means that this insn is from the target of the branch.
|
</p>
|
<p>In an <code>insn</code> during instruction scheduling, 1 means that this insn
|
must be scheduled as part of a group together with the previous insn.
|
</p>
|
<p>In an RTL dump, this flag is represented as ‘<samp>/s</samp>’.
|
</p>
|
<a name="index-return_005fval"></a>
|
<a name="index-_002fi-in-RTL-dump"></a>
|
</dd>
|
<dt><code>return_val</code></dt>
|
<dd><p>In <code>reg</code> expressions, 1 means the register contains
|
the value to be returned by the current function. On
|
machines that pass parameters in registers, the same register number
|
may be used for parameters as well, but this flag is not set on such
|
uses.
|
</p>
|
<p>In <code>symbol_ref</code> expressions, 1 means the referenced symbol is weak.
|
</p>
|
<p>In <code>call</code> expressions, 1 means the call is pure.
|
</p>
|
<p>In an RTL dump, this flag is represented as ‘<samp>/i</samp>’.
|
</p>
|
<a name="index-jump"></a>
|
<a name="index-_002fj-in-RTL-dump"></a>
|
</dd>
|
<dt><code>jump</code></dt>
|
<dd><p>In a <code>mem</code> expression, 1 means we should keep the alias set for this
|
mem unchanged when we access a component.
|
</p>
|
<p>In a <code>set</code>, 1 means it is for a return.
|
</p>
|
<p>In a <code>call_insn</code>, 1 means it is a sibling call.
|
</p>
|
<p>In an RTL dump, this flag is represented as ‘<samp>/j</samp>’.
|
</p>
|
<a name="index-unchanging"></a>
|
<a name="index-_002fu-in-RTL-dump"></a>
|
</dd>
|
<dt><code>unchanging</code></dt>
|
<dd><p>In <code>reg</code> and <code>mem</code> expressions, 1 means
|
that the value of the expression never changes.
|
</p>
|
<p>In <code>subreg</code> expressions, it is 1 if the <code>subreg</code> references an
|
unsigned object whose mode has been promoted to a wider mode.
|
</p>
|
<p>In an <code>insn</code> or <code>jump_insn</code> in the delay slot of a branch
|
instruction, 1 means an annulling branch should be used.
|
</p>
|
<p>In a <code>symbol_ref</code> expression, 1 means that this symbol addresses
|
something in the per-function constant pool.
|
</p>
|
<p>In a <code>call_insn</code> 1 means that this instruction is a call to a const
|
function.
|
</p>
|
<p>In an RTL dump, this flag is represented as ‘<samp>/u</samp>’.
|
</p>
|
<a name="index-used"></a>
|
</dd>
|
<dt><code>used</code></dt>
|
<dd><p>This flag is used directly (without an access macro) at the end of RTL
|
generation for a function, to count the number of times an expression
|
appears in insns. Expressions that appear more than once are copied,
|
according to the rules for shared structure (see <a href="Sharing.html#Sharing">Sharing</a>).
|
</p>
|
<p>For a <code>reg</code>, it is used directly (without an access macro) by the
|
leaf register renumbering code to ensure that each register is only
|
renumbered once.
|
</p>
|
<p>In a <code>symbol_ref</code>, it indicates that an external declaration for
|
the symbol has already been written.
|
</p>
|
<a name="index-volatil"></a>
|
<a name="index-_002fv-in-RTL-dump"></a>
|
</dd>
|
<dt><code>volatil</code></dt>
|
<dd><a name="index-volatile-memory-references"></a>
|
<p>In a <code>mem</code>, <code>asm_operands</code>, or <code>asm_input</code>
|
expression, it is 1 if the memory
|
reference is volatile. Volatile memory references may not be deleted,
|
reordered or combined.
|
</p>
|
<p>In a <code>symbol_ref</code> expression, it is used for machine-specific
|
purposes.
|
</p>
|
<p>In a <code>reg</code> expression, it is 1 if the value is a user-level variable.
|
0 indicates an internal compiler temporary.
|
</p>
|
<p>In an <code>insn</code>, 1 means the insn has been deleted.
|
</p>
|
<p>In <code>label_ref</code> and <code>reg_label</code> expressions, 1 means a reference
|
to a non-local label.
|
</p>
|
<p>In <code>prefetch</code> expressions, 1 means that the containing insn is a
|
scheduling barrier.
|
</p>
|
<p>In an RTL dump, this flag is represented as ‘<samp>/v</samp>’.
|
</p></dd>
|
</dl>
|
|
<hr>
|
<div class="header">
|
<p>
|
Next: <a href="Machine-Modes.html#Machine-Modes" accesskey="n" rel="next">Machine Modes</a>, Previous: <a href="Special-Accessors.html#Special-Accessors" accesskey="p" rel="prev">Special 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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