| <html lang="en"> |
| <head> |
| <title>If - Using as</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Using as"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Pseudo-Ops.html#Pseudo-Ops" title="Pseudo Ops"> |
| <link rel="prev" href="Ident.html#Ident" title="Ident"> |
| <link rel="next" href="Incbin.html#Incbin" title="Incbin"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| This file documents the GNU Assembler "as". |
| |
| Copyright (C) 1991-2019 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 |
| or any later version published by the Free Software Foundation; |
| with no Invariant Sections, with no Front-Cover Texts, and with no |
| Back-Cover Texts. A copy of the license is included in the |
| section entitled ``GNU Free Documentation License''. |
| |
| --> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="If"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Incbin.html#Incbin">Incbin</a>, |
| Previous: <a rel="previous" accesskey="p" href="Ident.html#Ident">Ident</a>, |
| Up: <a rel="up" accesskey="u" href="Pseudo-Ops.html#Pseudo-Ops">Pseudo Ops</a> |
| <hr> |
| </div> |
| |
| <h3 class="section">7.44 <code>.if </code><var>absolute expression</var></h3> |
| |
| <p><a name="index-conditional-assembly-361"></a><a name="index-g_t_0040code_007bif_007d-directive-362"></a><code>.if</code> marks the beginning of a section of code which is only |
| considered part of the source program being assembled if the argument |
| (which must be an <var>absolute expression</var>) is non-zero. The end of |
| the conditional section of code must be marked by <code>.endif</code> |
| (see <a href="Endif.html#Endif"><code>.endif</code></a>); optionally, you may include code for the |
| alternative condition, flagged by <code>.else</code> (see <a href="Else.html#Else"><code>.else</code></a>). |
| If you have several conditions to check, <code>.elseif</code> may be used to avoid |
| nesting blocks if/else within each subsequent <code>.else</code> block. |
| |
| <p>The following variants of <code>.if</code> are also supported: |
| |
| <a name="index-g_t_0040code_007bifdef_007d-directive-363"></a> |
| <dl><dt><code>.ifdef </code><var>symbol</var><dd>Assembles the following section of code if the specified <var>symbol</var> |
| has been defined. Note a symbol which has been referenced but not yet defined |
| is considered to be undefined. |
| |
| <p><a name="index-g_t_0040code_007bifb_007d-directive-364"></a><br><dt><code>.ifb </code><var>text</var><dd>Assembles the following section of code if the operand is blank (empty). |
| |
| <p><a name="index-g_t_0040code_007bifc_007d-directive-365"></a><br><dt><code>.ifc </code><var>string1</var><code>,</code><var>string2</var><dd>Assembles the following section of code if the two strings are the same. The |
| strings may be optionally quoted with single quotes. If they are not quoted, |
| the first string stops at the first comma, and the second string stops at the |
| end of the line. Strings which contain whitespace should be quoted. The |
| string comparison is case sensitive. |
| |
| <p><a name="index-g_t_0040code_007bifeq_007d-directive-366"></a><br><dt><code>.ifeq </code><var>absolute expression</var><dd>Assembles the following section of code if the argument is zero. |
| |
| <p><a name="index-g_t_0040code_007bifeqs_007d-directive-367"></a><br><dt><code>.ifeqs </code><var>string1</var><code>,</code><var>string2</var><dd>Another form of <code>.ifc</code>. The strings must be quoted using double quotes. |
| |
| <p><a name="index-g_t_0040code_007bifge_007d-directive-368"></a><br><dt><code>.ifge </code><var>absolute expression</var><dd>Assembles the following section of code if the argument is greater than or |
| equal to zero. |
| |
| <p><a name="index-g_t_0040code_007bifgt_007d-directive-369"></a><br><dt><code>.ifgt </code><var>absolute expression</var><dd>Assembles the following section of code if the argument is greater than zero. |
| |
| <p><a name="index-g_t_0040code_007bifle_007d-directive-370"></a><br><dt><code>.ifle </code><var>absolute expression</var><dd>Assembles the following section of code if the argument is less than or equal |
| to zero. |
| |
| <p><a name="index-g_t_0040code_007biflt_007d-directive-371"></a><br><dt><code>.iflt </code><var>absolute expression</var><dd>Assembles the following section of code if the argument is less than zero. |
| |
| <p><a name="index-g_t_0040code_007bifnb_007d-directive-372"></a><br><dt><code>.ifnb </code><var>text</var><dd>Like <code>.ifb</code>, but the sense of the test is reversed: this assembles the |
| following section of code if the operand is non-blank (non-empty). |
| |
| <p><a name="index-g_t_0040code_007bifnc_007d-directive-373"></a><br><dt><code>.ifnc </code><var>string1</var><code>,</code><var>string2</var><code>.</code><dd>Like <code>.ifc</code>, but the sense of the test is reversed: this assembles the |
| following section of code if the two strings are not the same. |
| |
| <p><a name="index-g_t_0040code_007bifndef_007d-directive-374"></a><a name="index-g_t_0040code_007bifnotdef_007d-directive-375"></a><br><dt><code>.ifndef </code><var>symbol</var><dt><code>.ifnotdef </code><var>symbol</var><dd>Assembles the following section of code if the specified <var>symbol</var> |
| has not been defined. Both spelling variants are equivalent. Note a symbol |
| which has been referenced but not yet defined is considered to be undefined. |
| |
| <p><a name="index-g_t_0040code_007bifne_007d-directive-376"></a><br><dt><code>.ifne </code><var>absolute expression</var><dd>Assembles the following section of code if the argument is not equal to zero |
| (in other words, this is equivalent to <code>.if</code>). |
| |
| <p><a name="index-g_t_0040code_007bifnes_007d-directive-377"></a><br><dt><code>.ifnes </code><var>string1</var><code>,</code><var>string2</var><dd>Like <code>.ifeqs</code>, but the sense of the test is reversed: this assembles the |
| following section of code if the two strings are not the same. |
| </dl> |
| |
| </body></html> |
| |
