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<h4 class="subsection">10.7.1 Basic Statements</h4>
<p><a name="index-Basic-Statements-1937"></a>
<dl>
<dt><code>ASM_EXPR</code><dd>
Used to represent an inline assembly statement. For an inline assembly
statement like:
<pre class="smallexample"> asm ("mov x, y");
</pre>
<p>The <code>ASM_STRING</code> macro will return a <code>STRING_CST</code> node for
<code>"mov x, y"</code>. If the original statement made use of the
extended-assembly syntax, then <code>ASM_OUTPUTS</code>,
<code>ASM_INPUTS</code>, and <code>ASM_CLOBBERS</code> will be the outputs, inputs,
and clobbers for the statement, represented as <code>STRING_CST</code> nodes.
The extended-assembly syntax looks like:
<pre class="smallexample"> asm ("fsinx %1,%0" : "=f" (result) : "f" (angle));
</pre>
<p>The first string is the <code>ASM_STRING</code>, containing the instruction
template. The next two strings are the output and inputs, respectively;
this statement has no clobbers. As this example indicates, “plain”
assembly statements are merely a special case of extended assembly
statements; they have no cv-qualifiers, outputs, inputs, or clobbers.
All of the strings will be <code>NUL</code>-terminated, and will contain no
embedded <code>NUL</code>-characters.
<p>If the assembly statement is declared <code>volatile</code>, or if the
statement was not an extended assembly statement, and is therefore
implicitly volatile, then the predicate <code>ASM_VOLATILE_P</code> will hold
of the <code>ASM_EXPR</code>.
<br><dt><code>DECL_EXPR</code><dd>
Used to represent a local declaration. The <code>DECL_EXPR_DECL</code> macro
can be used to obtain the entity declared. This declaration may be a
<code>LABEL_DECL</code>, indicating that the label declared is a local label.
(As an extension, GCC allows the declaration of labels with scope.) In
C, this declaration may be a <code>FUNCTION_DECL</code>, indicating the
use of the GCC nested function extension. For more information,
see <a href="Functions.html#Functions">Functions</a>.
<br><dt><code>LABEL_EXPR</code><dd>
Used to represent a label. The <code>LABEL_DECL</code> declared by this
statement can be obtained with the <code>LABEL_EXPR_LABEL</code> macro. The
<code>IDENTIFIER_NODE</code> giving the name of the label can be obtained from
the <code>LABEL_DECL</code> with <code>DECL_NAME</code>.
<br><dt><code>GOTO_EXPR</code><dd>
Used to represent a <code>goto</code> statement. The <code>GOTO_DESTINATION</code> will
usually be a <code>LABEL_DECL</code>. However, if the “computed goto” extension
has been used, the <code>GOTO_DESTINATION</code> will be an arbitrary expression
indicating the destination. This expression will always have pointer type.
<br><dt><code>RETURN_EXPR</code><dd>
Used to represent a <code>return</code> statement. Operand 0 represents the
value to return. It should either be the <code>RESULT_DECL</code> for the
containing function, or a <code>MODIFY_EXPR</code> or <code>INIT_EXPR</code>
setting the function's <code>RESULT_DECL</code>. It will be
<code>NULL_TREE</code> if the statement was just
<pre class="smallexample"> return;
</pre>
<br><dt><code>LOOP_EXPR</code><dd>These nodes represent “infinite” loops. The <code>LOOP_EXPR_BODY</code>
represents the body of the loop. It should be executed forever, unless
an <code>EXIT_EXPR</code> is encountered.
<br><dt><code>EXIT_EXPR</code><dd>These nodes represent conditional exits from the nearest enclosing
<code>LOOP_EXPR</code>. The single operand is the condition; if it is
nonzero, then the loop should be exited. An <code>EXIT_EXPR</code> will only
appear within a <code>LOOP_EXPR</code>.
<br><dt><code>SWITCH_STMT</code><dd>
Used to represent a <code>switch</code> statement. The <code>SWITCH_STMT_COND</code>
is the expression on which the switch is occurring. See the documentation
for an <code>IF_STMT</code> for more information on the representation used
for the condition. The <code>SWITCH_STMT_BODY</code> is the body of the switch
statement. The <code>SWITCH_STMT_TYPE</code> is the original type of switch
expression as given in the source, before any compiler conversions.
<br><dt><code>CASE_LABEL_EXPR</code><dd>
Use to represent a <code>case</code> label, range of <code>case</code> labels, or a
<code>default</code> label. If <code>CASE_LOW</code> is <code>NULL_TREE</code>, then this is a
<code>default</code> label. Otherwise, if <code>CASE_HIGH</code> is <code>NULL_TREE</code>, then
this is an ordinary <code>case</code> label. In this case, <code>CASE_LOW</code> is
an expression giving the value of the label. Both <code>CASE_LOW</code> and
<code>CASE_HIGH</code> are <code>INTEGER_CST</code> nodes. These values will have
the same type as the condition expression in the switch statement.
<p>Otherwise, if both <code>CASE_LOW</code> and <code>CASE_HIGH</code> are defined, the
statement is a range of case labels. Such statements originate with the
extension that allows users to write things of the form:
<pre class="smallexample"> case 2 ... 5:
</pre>
<p>The first value will be <code>CASE_LOW</code>, while the second will be
<code>CASE_HIGH</code>.
</dl>
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