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| <h3 class="section">7.3 <code>.align </code><var>abs-expr</var><code>, </code><var>abs-expr</var><code>, </code><var>abs-expr</var></h3> |
| |
| <p><a name="index-padding-the-location-counter-275"></a><a name="index-g_t_0040code_007balign_007d-directive-276"></a>Pad the location counter (in the current subsection) to a particular storage |
| boundary. The first expression (which must be absolute) is the alignment |
| required, as described below. |
| |
| <p>The second expression (also absolute) gives the fill value to be stored in the |
| padding bytes. It (and the comma) may be omitted. If it is omitted, the |
| padding bytes are normally zero. However, on some systems, if the section is |
| marked as containing code and the fill value is omitted, the space is filled |
| with no-op instructions. |
| |
| <p>The third expression is also absolute, and is also optional. If it is present, |
| it is the maximum number of bytes that should be skipped by this alignment |
| directive. If doing the alignment would require skipping more bytes than the |
| specified maximum, then the alignment is not done at all. You can omit the |
| fill value (the second argument) entirely by simply using two commas after the |
| required alignment; this can be useful if you want the alignment to be filled |
| with no-op instructions when appropriate. |
| |
| <p>The way the required alignment is specified varies from system to system. |
| For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32, |
| s390, sparc, tic4x, tic80 and xtensa, the first expression is the |
| alignment request in bytes. For example ‘<samp><span class="samp">.align 8</span></samp>’ advances |
| the location counter until it is a multiple of 8. If the location counter |
| is already a multiple of 8, no change is needed. For the tic54x, the |
| first expression is the alignment request in words. |
| |
| <p>For other systems, including ppc, i386 using a.out format, arm and |
| strongarm, it is the |
| number of low-order zero bits the location counter must have after |
| advancement. For example ‘<samp><span class="samp">.align 3</span></samp>’ advances the location |
| counter until it a multiple of 8. If the location counter is already a |
| multiple of 8, no change is needed. |
| |
| <p>This inconsistency is due to the different behaviors of the various |
| native assemblers for these systems which GAS must emulate. |
| GAS also provides <code>.balign</code> and <code>.p2align</code> directives, |
| described later, which have a consistent behavior across all |
| architectures (but are specific to GAS). |
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