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| Next: <a href="Blocks.html#Blocks" accesskey="n" rel="next">Blocks</a>, Up: <a href="Statements.html#Statements" accesskey="u" rel="up">Statements</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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| <a name="Basic-Statements-1"></a> |
| <h4 class="subsection">10.7.1 Basic Statements</h4> |
| <a name="index-Basic-Statements"></a> |
| |
| <dl compact="compact"> |
| <dt><code>ASM_EXPR</code></dt> |
| <dd> |
| <p>Used to represent an inline assembly statement. For an inline assembly |
| statement like: |
| </p><div class="smallexample"> |
| <pre class="smallexample">asm ("mov x, y"); |
| </pre></div> |
| <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: |
| </p><div class="smallexample"> |
| <pre class="smallexample">asm ("fsinx %1,%0" : "=f" (result) : "f" (angle)); |
| </pre></div> |
| <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> |
| <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>. |
| </p> |
| </dd> |
| <dt><code>DECL_EXPR</code></dt> |
| <dd> |
| <p>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>. |
| </p> |
| </dd> |
| <dt><code>LABEL_EXPR</code></dt> |
| <dd> |
| <p>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>. |
| </p> |
| </dd> |
| <dt><code>GOTO_EXPR</code></dt> |
| <dd> |
| <p>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. |
| </p> |
| </dd> |
| <dt><code>RETURN_EXPR</code></dt> |
| <dd> |
| <p>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 |
| </p><div class="smallexample"> |
| <pre class="smallexample">return; |
| </pre></div> |
| |
| </dd> |
| <dt><code>LOOP_EXPR</code></dt> |
| <dd><p>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. |
| </p> |
| </dd> |
| <dt><code>EXIT_EXPR</code></dt> |
| <dd><p>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>. |
| </p> |
| </dd> |
| <dt><code>SWITCH_STMT</code></dt> |
| <dd> |
| <p>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. |
| </p> |
| </dd> |
| <dt><code>CASE_LABEL_EXPR</code></dt> |
| <dd> |
| <p>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> |
| <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: |
| </p><div class="smallexample"> |
| <pre class="smallexample">case 2 ... 5: |
| </pre></div> |
| <p>The first value will be <code>CASE_LOW</code>, while the second will be |
| <code>CASE_HIGH</code>. |
| </p> |
| </dd> |
| </dl> |
| |
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