as: Align
1
1 7.3 '.align ABS-EXPR, ABS-EXPR, ABS-EXPR'
1 =========================================
1
1 Pad the location counter (in the current subsection) to a particular
1 storage boundary. The first expression (which must be absolute) is the
1 alignment required, as described below.
1
1 The second expression (also absolute) gives the fill value to be
1 stored in the padding bytes. It (and the comma) may be omitted. If it
1 is omitted, the padding bytes are normally zero. However, on most
1 systems, if the section is marked as containing code and the fill value
1 is omitted, the space is filled with no-op instructions.
1
1 The third expression is also absolute, and is also optional. If it
1 is present, it is the maximum number of bytes that should be skipped by
1 this alignment directive. If doing the alignment would require skipping
1 more bytes than the specified maximum, then the alignment is not done at
1 all. You can omit the fill value (the second argument) entirely by
1 simply using two commas after the required alignment; this can be useful
1 if you want the alignment to be filled with no-op instructions when
1 appropriate.
1
1 The way the required alignment is specified varies from system to
1 system. For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
1 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
1 alignment request in bytes. For example '.align 8' advances the
1 location counter until it is a multiple of 8. If the location counter
1 is already a multiple of 8, no change is needed. For the tic54x, the
1 first expression is the alignment request in words.
1
1 For other systems, including ppc, i386 using a.out format, arm and
1 strongarm, it is the number of low-order zero bits the location counter
1 must have after advancement. For example '.align 3' advances the
1 location counter until it a multiple of 8. If the location counter is
1 already a multiple of 8, no change is needed.
1
1 This inconsistency is due to the different behaviors of the various
1 native assemblers for these systems which GAS must emulate. GAS also
1 provides '.balign' and '.p2align' directives, described later, which
1 have a consistent behavior across all architectures (but are specific to
1 GAS).
1