as: Align
7.3 '.align ABS-EXPR, ABS-EXPR, ABS-EXPR'
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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.
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 most
systems, if the section is marked as containing code and the fill value
is omitted, the space is filled with no-op instructions.
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.
The way the required alignment is specified varies from system to
system. For the arc, hppa, i386 using ELF, iq2000, m68k, or1k, s390,
sparc, tic4x, tic80 and xtensa, the first expression is the alignment
request in bytes. For example '.align 8' 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.
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 '.align 3' advances the
location counter until it a multiple of 8. If the location counter is
already a multiple of 8, no change is needed.
This inconsistency is due to the different behaviors of the various
native assemblers for these systems which GAS must emulate. GAS also
provides '.balign' and '.p2align' directives, described later, which
have a consistent behavior across all architectures (but are specific to
GAS).
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