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11.7.1 Basic Statements


Used to represent an inline assembly statement. For an inline assembly statement like:

asm ("mov x, y");

The ASM_STRING macro will return a STRING_CST node for "mov x, y". If the original statement made use of the extended-assembly syntax, then ASM_OUTPUTS, ASM_INPUTS, and ASM_CLOBBERS will be the outputs, inputs, and clobbers for the statement, represented as STRING_CST nodes. The extended-assembly syntax looks like:

asm ("fsinx %1,%0" : "=f" (result) : "f" (angle));

The first string is the ASM_STRING, 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 NUL-terminated, and will contain no embedded NUL-characters.

If the assembly statement is declared volatile, or if the statement was not an extended assembly statement, and is therefore implicitly volatile, then the predicate ASM_VOLATILE_P will hold of the ASM_EXPR.


Used to represent a local declaration. The DECL_EXPR_DECL macro can be used to obtain the entity declared. This declaration may be a LABEL_DECL, 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 FUNCTION_DECL, indicating the use of the GCC nested function extension. For more information, see Functions.


Used to represent a label. The LABEL_DECL declared by this statement can be obtained with the LABEL_EXPR_LABEL macro. The IDENTIFIER_NODE giving the name of the label can be obtained from the LABEL_DECL with DECL_NAME.


Used to represent a goto statement. The GOTO_DESTINATION will usually be a LABEL_DECL. However, if the “computed goto” extension has been used, the GOTO_DESTINATION will be an arbitrary expression indicating the destination. This expression will always have pointer type.


Used to represent a return statement. Operand 0 represents the value to return. It should either be the RESULT_DECL for the containing function, or a MODIFY_EXPR or INIT_EXPR setting the function’s RESULT_DECL. It will be NULL_TREE if the statement was just


These nodes represent “infinite” loops. The LOOP_EXPR_BODY represents the body of the loop. It should be executed forever, unless an EXIT_EXPR is encountered.


These nodes represent conditional exits from the nearest enclosing LOOP_EXPR. The single operand is the condition; if it is nonzero, then the loop should be exited. An EXIT_EXPR will only appear within a LOOP_EXPR.


Used to represent a switch statement. The SWITCH_COND is the expression on which the switch is occurring. The SWITCH_BODY is the body of the switch statement. SWITCH_ALL_CASES_P is true if the switch includes a default label or the case label ranges cover all possible values of the condition expression.

Note that TREE_TYPE for a SWITCH_EXPR represents the original type of switch expression as given in the source, before any compiler conversions, instead of the type of the switch expression itself (which is not meaningful).


Use to represent a case label, range of case labels, or a default label. If CASE_LOW is NULL_TREE, then this is a default label. Otherwise, if CASE_HIGH is NULL_TREE, then this is an ordinary case label. In this case, CASE_LOW is an expression giving the value of the label. Both CASE_LOW and CASE_HIGH are INTEGER_CST nodes. These values will have the same type as the condition expression in the switch statement.

Otherwise, if both CASE_LOW and CASE_HIGH 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:

case 2 ... 5:

The first value will be CASE_LOW, while the second will be CASE_HIGH.


Marks the beginning of a source statement, for purposes of debug information generation.

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