Info Catalog as: Balign as: Pseudo Ops as: Byte

as: Bundle directives

 
 7.8 Bundle directives
 =====================
 
 7.8.1 '.bundle_align_mode ABS-EXPR'
 -----------------------------------
 
 '.bundle_align_mode' enables or disables "aligned instruction bundle"
 mode.  In this mode, sequences of adjacent instructions are grouped into
 fixed-sized "bundles".  If the argument is zero, this mode is disabled
 (which is the default state).  If the argument it not zero, it gives the
 size of an instruction bundle as a power of two (as for the '.p2align'
 directive, P2align).
 
    For some targets, it's an ABI requirement that no instruction may
 span a certain aligned boundary.  A "bundle" is simply a sequence of
 instructions that starts on an aligned boundary.  For example, if
 ABS-EXPR is '5' then the bundle size is 32, so each aligned chunk of 32
 bytes is a bundle.  When aligned instruction bundle mode is in effect,
 no single instruction may span a boundary between bundles.  If an
 instruction would start too close to the end of a bundle for the length
 of that particular instruction to fit within the bundle, then the space
 at the end of that bundle is filled with no-op instructions so the
 instruction starts in the next bundle.  As a corollary, it's an error if
 any single instruction's encoding is longer than the bundle size.
 
 7.8.2 '.bundle_lock' and '.bundle_unlock'
 -----------------------------------------
 
 The '.bundle_lock' and directive '.bundle_unlock' directives allow
 explicit control over instruction bundle padding.  These directives are
 only valid when '.bundle_align_mode' has been used to enable aligned
 instruction bundle mode.  It's an error if they appear when
 '.bundle_align_mode' has not been used at all, or when the last
 directive was '.bundle_align_mode 0'.
 
    For some targets, it's an ABI requirement that certain instructions
 may appear only as part of specified permissible sequences of multiple
 instructions, all within the same bundle.  A pair of '.bundle_lock' and
 '.bundle_unlock' directives define a "bundle-locked" instruction
 sequence.  For purposes of aligned instruction bundle mode, a sequence
 starting with '.bundle_lock' and ending with '.bundle_unlock' is treated
 as a single instruction.  That is, the entire sequence must fit into a
 single bundle and may not span a bundle boundary.  If necessary, no-op
 instructions will be inserted before the first instruction of the
 sequence so that the whole sequence starts on an aligned bundle
 boundary.  It's an error if the sequence is longer than the bundle size.
 
    For convenience when using '.bundle_lock' and '.bundle_unlock' inside
 assembler macros (Macro), bundle-locked sequences may be nested.
 That is, a second '.bundle_lock' directive before the next
 '.bundle_unlock' directive has no effect except that it must be matched
 by another closing '.bundle_unlock' so that there is the same number of
 '.bundle_lock' and '.bundle_unlock' directives.
 

Info Catalog as: Balign as: Pseudo Ops as: Byte