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 <a name="Logical-Operators"></a>
 <div class="header">
 <p>
 Previous: <a href="Conditional-Expressions.html#Conditional-Expressions" accesskey="p" rel="prev">Conditional Expressions</a>, Up: <a href="Operands.html#Operands" accesskey="u" rel="up">Operands</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
 </div>
 <hr>
 <a name="Logical-Operators-1"></a>
 <h4 class="subsection">11.5.4 Logical Operators</h4>
 <a name="index-Logical-Operators"></a>

 <p>Except when they appear in the condition operand of a
 <code>GIMPLE_COND</code>, logical &lsquo;and&rsquo; and &lsquo;or&rsquo; operators are simplified
 as follows: <code>a = b &amp;&amp; c</code> becomes
 </p>
 <div class="smallexample">
 <pre class="smallexample">T1 = (bool)b;
 if (T1 == true)
   T1 = (bool)c;
 a = T1;
 </pre></div>

 <p>Note that <code>T1</code> in this example cannot be an expression temporary,
 because it has two different assignments.
 </p>
 <a name="Manipulating-operands"></a>
 <h4 class="subsection">11.5.5 Manipulating operands</h4>

 <p>All gimple operands are of type <code>tree</code>.  But only certain
 types of trees are allowed to be used as operand tuples.  Basic
 validation is controlled by the function
 <code>get_gimple_rhs_class</code>, which given a tree code, returns an
 <code>enum</code> with the following values of type <code>enum
 gimple_rhs_class</code>
 </p>
 <ul>
 <li> <code>GIMPLE_INVALID_RHS</code>
 The tree cannot be used as a GIMPLE operand.

 </li><li> <code>GIMPLE_TERNARY_RHS</code>
 The tree is a valid GIMPLE ternary operation.

 </li><li> <code>GIMPLE_BINARY_RHS</code>
 The tree is a valid GIMPLE binary operation.

 </li><li> <code>GIMPLE_UNARY_RHS</code>
 The tree is a valid GIMPLE unary operation.

 </li><li> <code>GIMPLE_SINGLE_RHS</code>
 The tree is a single object, that cannot be split into simpler
 operands (for instance, <code>SSA_NAME</code>, <code>VAR_DECL</code>, <code>COMPONENT_REF</code>, etc).

 <p>This operand class also acts as an escape hatch for tree nodes
 that may be flattened out into the operand vector, but would need
 more than two slots on the RHS.  For instance, a <code>COND_EXPR</code>
 expression of the form <code>(a op b) ? x : y</code> could be flattened
 out on the operand vector using 4 slots, but it would also
 require additional processing to distinguish <code>c = a op b</code>
 from <code>c = a op b ? x : y</code>.  Something similar occurs with
 <code>ASSERT_EXPR</code>.   In time, these special case tree
 expressions should be flattened into the operand vector.
 </p></li></ul>

 <p>For tree nodes in the categories <code>GIMPLE_TERNARY_RHS</code>,
 <code>GIMPLE_BINARY_RHS</code> and <code>GIMPLE_UNARY_RHS</code>, they cannot be
 stored inside tuples directly.  They first need to be flattened and
 separated into individual components.  For instance, given the GENERIC
 expression
 </p>
 <div class="smallexample">
 <pre class="smallexample">a = b + c
 </pre></div>

 <p>its tree representation is:
 </p>
 <div class="smallexample">
 <pre class="smallexample">MODIFY_EXPR &lt;VAR_DECL  &lt;a&gt;, PLUS_EXPR &lt;VAR_DECL &lt;b&gt;, VAR_DECL &lt;c&gt;&gt;&gt;
 </pre></div>

 <p>In this case, the GIMPLE form for this statement is logically
 identical to its GENERIC form but in GIMPLE, the <code>PLUS_EXPR</code>
 on the RHS of the assignment is not represented as a tree,
 instead the two operands are taken out of the <code>PLUS_EXPR</code> sub-tree
 and flattened into the GIMPLE tuple as follows:
 </p>
 <div class="smallexample">
 <pre class="smallexample">GIMPLE_ASSIGN &lt;PLUS_EXPR, VAR_DECL &lt;a&gt;, VAR_DECL &lt;b&gt;, VAR_DECL &lt;c&gt;&gt;
 </pre></div>

 <a name="Operand-vector-allocation"></a>
 <h4 class="subsection">11.5.6 Operand vector allocation</h4>

 <p>The operand vector is stored at the bottom of the three tuple
 structures that accept operands. This means, that depending on
 the code of a given statement, its operand vector will be at
 different offsets from the base of the structure.  To access
 tuple operands use the following accessors
 </p>
 <dl>
 <dt><a name="index-gimple_005fnum_005fops"></a>GIMPLE function: <em>unsigned</em> <strong>gimple_num_ops</strong> <em>(gimple g)</em></dt>
 <dd><p>Returns the number of operands in statement G.
 </p></dd></dl>

 <dl>
 <dt><a name="index-gimple_005fop"></a>GIMPLE function: <em>tree</em> <strong>gimple_op</strong> <em>(gimple g, unsigned i)</em></dt>
 <dd><p>Returns operand <code>I</code> from statement <code>G</code>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-gimple_005fops"></a>GIMPLE function: <em>tree *</em> <strong>gimple_ops</strong> <em>(gimple g)</em></dt>
 <dd><p>Returns a pointer into the operand vector for statement <code>G</code>.  This
 is computed using an internal table called <code>gimple_ops_offset_</code>[].
 This table is indexed by the gimple code of <code>G</code>.
 </p>
 <p>When the compiler is built, this table is filled-in using the
 sizes of the structures used by each statement code defined in
 gimple.def.  Since the operand vector is at the bottom of the
 structure, for a gimple code <code>C</code> the offset is computed as sizeof
 (struct-of <code>C</code>) - sizeof (tree).
 </p>
 <p>This mechanism adds one memory indirection to every access when
 using <code>gimple_op</code>(), if this becomes a bottleneck, a pass can
 choose to memoize the result from <code>gimple_ops</code>() and use that to
 access the operands.
 </p></dd></dl>

 <a name="Operand-validation"></a>
 <h4 class="subsection">11.5.7 Operand validation</h4>

 <p>When adding a new operand to a gimple statement, the operand will
 be validated according to what each tuple accepts in its operand
 vector.  These predicates are called by the
 <code>gimple_<var>name</var>_set_...()</code>.  Each tuple will use one of the
 following predicates (Note, this list is not exhaustive):
 </p>
 <dl>
 <dt><a name="index-is_005fgimple_005fval"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_val</strong> <em>(tree t)</em></dt>
 <dd><p>Returns true if t is a &quot;GIMPLE value&quot;, which are all the
 non-addressable stack variables (variables for which
 <code>is_gimple_reg</code> returns true) and constants (expressions for which
 <code>is_gimple_min_invariant</code> returns true).
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005faddressable"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_addressable</strong> <em>(tree t)</em></dt>
 <dd><p>Returns true if t is a symbol or memory reference whose address
 can be taken.
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fasm_005fval"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_asm_val</strong> <em>(tree t)</em></dt>
 <dd><p>Similar to <code>is_gimple_val</code> but it also accepts hard registers.
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fcall_005faddr"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_call_addr</strong> <em>(tree t)</em></dt>
 <dd><p>Return true if t is a valid expression to use as the function
 called by a <code>GIMPLE_CALL</code>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fmem_005fref_005faddr"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_mem_ref_addr</strong> <em>(tree t)</em></dt>
 <dd><p>Return true if t is a valid expression to use as first operand
 of a <code>MEM_REF</code> expression.
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fconstant"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_constant</strong> <em>(tree t)</em></dt>
 <dd><p>Return true if t is a valid gimple constant.
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fmin_005finvariant"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_min_invariant</strong> <em>(tree t)</em></dt>
 <dd><p>Return true if t is a valid minimal invariant.  This is different
 from constants, in that the specific value of t may not be known
 at compile time, but it is known that it doesn&rsquo;t change (e.g.,
 the address of a function local variable).
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fip_005finvariant"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_ip_invariant</strong> <em>(tree t)</em></dt>
 <dd><p>Return true if t is an interprocedural invariant.  This means that t
 is a valid invariant in all functions (e.g. it can be an address of a
 global variable but not of a local one).
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fip_005finvariant_005faddress"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_ip_invariant_address</strong> <em>(tree t)</em></dt>
 <dd><p>Return true if t is an <code>ADDR_EXPR</code> that does not change once the
 program is running (and which is valid in all functions).
 </p></dd></dl>


 <a name="Statement-validation"></a>
 <h4 class="subsection">11.5.8 Statement validation</h4>

 <dl>
 <dt><a name="index-is_005fgimple_005fassign"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_assign</strong> <em>(gimple g)</em></dt>
 <dd><p>Return true if the code of g is <code>GIMPLE_ASSIGN</code>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fcall"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_call</strong> <em>(gimple g)</em></dt>
 <dd><p>Return true if the code of g is <code>GIMPLE_CALL</code>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fdebug"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_debug</strong> <em>(gimple g)</em></dt>
 <dd><p>Return true if the code of g is <code>GIMPLE_DEBUG</code>.
 </p></dd></dl>

 <dl>
 <dt><a name="index-gimple_005fassign_005fcast_005fp"></a>GIMPLE function: <em>bool</em> <strong>gimple_assign_cast_p</strong> <em>(gimple g)</em></dt>
 <dd><p>Return true if g is a <code>GIMPLE_ASSIGN</code> that performs a type cast
 operation.
 </p></dd></dl>

 <dl>
 <dt><a name="index-gimple_005fdebug_005fbind_005fp"></a>GIMPLE function: <em>bool</em> <strong>gimple_debug_bind_p</strong> <em>(gimple g)</em></dt>
 <dd><p>Return true if g is a <code>GIMPLE_DEBUG</code> that binds the value of an
 expression to a variable.
 </p></dd></dl>

 <dl>
 <dt><a name="index-is_005fgimple_005fomp"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_omp</strong> <em>(gimple g)</em></dt>
 <dd><p>Return true if g is any of the OpenMP codes.
 </p></dd></dl>

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	<a name="Logical-Operators"></a>
	<div class="header">
	<p>
	Previous: <a href="Conditional-Expressions.html#Conditional-Expressions" accesskey="p" rel="prev">Conditional Expressions</a>, Up: <a href="Operands.html#Operands" accesskey="u" rel="up">Operands</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
	</div>
	<hr>
	<a name="Logical-Operators-1"></a>
	<h4 class="subsection">11.5.4 Logical Operators</h4>
	<a name="index-Logical-Operators"></a>

	<p>Except when they appear in the condition operand of a
	<code>GIMPLE_COND</code>, logical ‘and’ and ‘or’ operators are simplified
	as follows: <code>a = b && c</code> becomes
	</p>
	<div class="smallexample">
	<pre class="smallexample">T1 = (bool)b;
	if (T1 == true)
	T1 = (bool)c;
	a = T1;
	</pre></div>

	<p>Note that <code>T1</code> in this example cannot be an expression temporary,
	because it has two different assignments.
	</p>
	<a name="Manipulating-operands"></a>
	<h4 class="subsection">11.5.5 Manipulating operands</h4>

	<p>All gimple operands are of type <code>tree</code>. But only certain
	types of trees are allowed to be used as operand tuples. Basic
	validation is controlled by the function
	<code>get_gimple_rhs_class</code>, which given a tree code, returns an
	<code>enum</code> with the following values of type <code>enum
	gimple_rhs_class</code>
	</p>
	<ul>
	<li> <code>GIMPLE_INVALID_RHS</code>
	The tree cannot be used as a GIMPLE operand.

	</li><li> <code>GIMPLE_TERNARY_RHS</code>
	The tree is a valid GIMPLE ternary operation.

	</li><li> <code>GIMPLE_BINARY_RHS</code>
	The tree is a valid GIMPLE binary operation.

	</li><li> <code>GIMPLE_UNARY_RHS</code>
	The tree is a valid GIMPLE unary operation.

	</li><li> <code>GIMPLE_SINGLE_RHS</code>
	The tree is a single object, that cannot be split into simpler
	operands (for instance, <code>SSA_NAME</code>, <code>VAR_DECL</code>, <code>COMPONENT_REF</code>, etc).

	<p>This operand class also acts as an escape hatch for tree nodes
	that may be flattened out into the operand vector, but would need
	more than two slots on the RHS. For instance, a <code>COND_EXPR</code>
	expression of the form <code>(a op b) ? x : y</code> could be flattened
	out on the operand vector using 4 slots, but it would also
	require additional processing to distinguish <code>c = a op b</code>
	from <code>c = a op b ? x : y</code>. Something similar occurs with
	<code>ASSERT_EXPR</code>. In time, these special case tree
	expressions should be flattened into the operand vector.
	</p></li></ul>

	<p>For tree nodes in the categories <code>GIMPLE_TERNARY_RHS</code>,
	<code>GIMPLE_BINARY_RHS</code> and <code>GIMPLE_UNARY_RHS</code>, they cannot be
	stored inside tuples directly. They first need to be flattened and
	separated into individual components. For instance, given the GENERIC
	expression
	</p>
	<div class="smallexample">
	<pre class="smallexample">a = b + c
	</pre></div>

	<p>its tree representation is:
	</p>
	<div class="smallexample">
	<pre class="smallexample">MODIFY_EXPR <VAR_DECL <a>, PLUS_EXPR <VAR_DECL <b>, VAR_DECL <c>>>
	</pre></div>

	<p>In this case, the GIMPLE form for this statement is logically
	identical to its GENERIC form but in GIMPLE, the <code>PLUS_EXPR</code>
	on the RHS of the assignment is not represented as a tree,
	instead the two operands are taken out of the <code>PLUS_EXPR</code> sub-tree
	and flattened into the GIMPLE tuple as follows:
	</p>
	<div class="smallexample">
	<pre class="smallexample">GIMPLE_ASSIGN <PLUS_EXPR, VAR_DECL <a>, VAR_DECL <b>, VAR_DECL <c>>
	</pre></div>

	<a name="Operand-vector-allocation"></a>
	<h4 class="subsection">11.5.6 Operand vector allocation</h4>

	<p>The operand vector is stored at the bottom of the three tuple
	structures that accept operands. This means, that depending on
	the code of a given statement, its operand vector will be at
	different offsets from the base of the structure. To access
	tuple operands use the following accessors
	</p>
	<dl>
	<dt><a name="index-gimple_005fnum_005fops"></a>GIMPLE function: <em>unsigned</em> <strong>gimple_num_ops</strong> <em>(gimple g)</em></dt>
	<dd><p>Returns the number of operands in statement G.
	</p></dd></dl>

	<dl>
	<dt><a name="index-gimple_005fop"></a>GIMPLE function: <em>tree</em> <strong>gimple_op</strong> <em>(gimple g, unsigned i)</em></dt>
	<dd><p>Returns operand <code>I</code> from statement <code>G</code>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-gimple_005fops"></a>GIMPLE function: <em>tree *</em> <strong>gimple_ops</strong> <em>(gimple g)</em></dt>
	<dd><p>Returns a pointer into the operand vector for statement <code>G</code>. This
	is computed using an internal table called <code>gimple_ops_offset_</code>[].
	This table is indexed by the gimple code of <code>G</code>.
	</p>
	<p>When the compiler is built, this table is filled-in using the
	sizes of the structures used by each statement code defined in
	gimple.def. Since the operand vector is at the bottom of the
	structure, for a gimple code <code>C</code> the offset is computed as sizeof
	(struct-of <code>C</code>) - sizeof (tree).
	</p>
	<p>This mechanism adds one memory indirection to every access when
	using <code>gimple_op</code>(), if this becomes a bottleneck, a pass can
	choose to memoize the result from <code>gimple_ops</code>() and use that to
	access the operands.
	</p></dd></dl>

	<a name="Operand-validation"></a>
	<h4 class="subsection">11.5.7 Operand validation</h4>

	<p>When adding a new operand to a gimple statement, the operand will
	be validated according to what each tuple accepts in its operand
	vector. These predicates are called by the
	<code>gimple_<var>name</var>_set_...()</code>. Each tuple will use one of the
	following predicates (Note, this list is not exhaustive):
	</p>
	<dl>
	<dt><a name="index-is_005fgimple_005fval"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_val</strong> <em>(tree t)</em></dt>
	<dd><p>Returns true if t is a "GIMPLE value", which are all the
	non-addressable stack variables (variables for which
	<code>is_gimple_reg</code> returns true) and constants (expressions for which
	<code>is_gimple_min_invariant</code> returns true).
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005faddressable"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_addressable</strong> <em>(tree t)</em></dt>
	<dd><p>Returns true if t is a symbol or memory reference whose address
	can be taken.
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fasm_005fval"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_asm_val</strong> <em>(tree t)</em></dt>
	<dd><p>Similar to <code>is_gimple_val</code> but it also accepts hard registers.
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fcall_005faddr"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_call_addr</strong> <em>(tree t)</em></dt>
	<dd><p>Return true if t is a valid expression to use as the function
	called by a <code>GIMPLE_CALL</code>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fmem_005fref_005faddr"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_mem_ref_addr</strong> <em>(tree t)</em></dt>
	<dd><p>Return true if t is a valid expression to use as first operand
	of a <code>MEM_REF</code> expression.
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fconstant"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_constant</strong> <em>(tree t)</em></dt>
	<dd><p>Return true if t is a valid gimple constant.
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fmin_005finvariant"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_min_invariant</strong> <em>(tree t)</em></dt>
	<dd><p>Return true if t is a valid minimal invariant. This is different
	from constants, in that the specific value of t may not be known
	at compile time, but it is known that it doesn’t change (e.g.,
	the address of a function local variable).
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fip_005finvariant"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_ip_invariant</strong> <em>(tree t)</em></dt>
	<dd><p>Return true if t is an interprocedural invariant. This means that t
	is a valid invariant in all functions (e.g. it can be an address of a
	global variable but not of a local one).
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fip_005finvariant_005faddress"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_ip_invariant_address</strong> <em>(tree t)</em></dt>
	<dd><p>Return true if t is an <code>ADDR_EXPR</code> that does not change once the
	program is running (and which is valid in all functions).
	</p></dd></dl>


	<a name="Statement-validation"></a>
	<h4 class="subsection">11.5.8 Statement validation</h4>

	<dl>
	<dt><a name="index-is_005fgimple_005fassign"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_assign</strong> <em>(gimple g)</em></dt>
	<dd><p>Return true if the code of g is <code>GIMPLE_ASSIGN</code>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fcall"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_call</strong> <em>(gimple g)</em></dt>
	<dd><p>Return true if the code of g is <code>GIMPLE_CALL</code>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fdebug"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_debug</strong> <em>(gimple g)</em></dt>
	<dd><p>Return true if the code of g is <code>GIMPLE_DEBUG</code>.
	</p></dd></dl>

	<dl>
	<dt><a name="index-gimple_005fassign_005fcast_005fp"></a>GIMPLE function: <em>bool</em> <strong>gimple_assign_cast_p</strong> <em>(gimple g)</em></dt>
	<dd><p>Return true if g is a <code>GIMPLE_ASSIGN</code> that performs a type cast
	operation.
	</p></dd></dl>

	<dl>
	<dt><a name="index-gimple_005fdebug_005fbind_005fp"></a>GIMPLE function: <em>bool</em> <strong>gimple_debug_bind_p</strong> <em>(gimple g)</em></dt>
	<dd><p>Return true if g is a <code>GIMPLE_DEBUG</code> that binds the value of an
	expression to a variable.
	</p></dd></dl>

	<dl>
	<dt><a name="index-is_005fgimple_005fomp"></a>GIMPLE function: <em>bool</em> <strong>is_gimple_omp</strong> <em>(gimple g)</em></dt>
	<dd><p>Return true if g is any of the OpenMP codes.
	</p></dd></dl>

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