diff options
Diffstat (limited to 'gas/doc/as.texinfo')
-rw-r--r-- | gas/doc/as.texinfo | 56 |
1 files changed, 55 insertions, 1 deletions
diff --git a/gas/doc/as.texinfo b/gas/doc/as.texinfo index 45405b8..2f892e2 100644 --- a/gas/doc/as.texinfo +++ b/gas/doc/as.texinfo @@ -3970,6 +3970,7 @@ Some machine configurations provide additional directives. * Ascii:: @code{.ascii "@var{string}"}@dots{} * Asciz:: @code{.asciz "@var{string}"}@dots{} * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}} +* Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock} * Byte:: @code{.byte @var{expressions}} * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc. * Comm:: @code{.comm @var{symbol} , @var{length} } @@ -4292,6 +4293,59 @@ filled in with the value 0x368d (the exact placement of the bytes depends upon the endianness of the processor). If it skips 1 or 3 bytes, the fill value is undefined. +@node Bundle directives +@section @code{.bundle_align_mode @var{abs-expr}} +@cindex @code{bundle_align_mode} directive +@cindex bundle +@cindex instruction bundle +@cindex aligned instruction bundle +@code{.bundle_align_mode} enables or disables @defn{aligned instruction +bundle} mode. In this mode, sequences of adjacent instructions are grouped +into fixed-sized @defn{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 +@code{.p2align} directive, @pxref{P2align}). + +For some targets, it's an ABI requirement that no instruction may span a +certain aligned boundary. A @defn{bundle} is simply a sequence of +instructions that starts on an aligned boundary. For example, if +@var{abs-expr} is @code{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. + +@section @code{.bundle_lock} and @code{.bundle_unlock} +@cindex @code{bundle_lock} directive +@cindex @code{bundle_unlock} directive +The @code{.bundle_lock} and directive @code{.bundle_unlock} directives +allow explicit control over instruction bundle padding. These directives +are only valid when @code{.bundle_align_mode} has been used to enable +aligned instruction bundle mode. It's an error if they appear when +@code{.bundle_align_mode} has not been used at all, or when the last +directive was @w{@code{.bundle_align_mode 0}}. + +@cindex bundle-locked +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 @code{.bundle_lock} +and @code{.bundle_unlock} directives define a @defn{bundle-locked} +instruction sequence. For purposes of aligned instruction bundle mode, a +sequence starting with @code{.bundle_lock} and ending with +@code{.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. + +Bundle-locked sequences do not nest. It's an error if two +@code{.bundle_lock} directives appear without an intervening +@code{.bundle_unlock} directive. + @node Byte @section @code{.byte @var{expressions}} @@ -5521,7 +5575,7 @@ hence @emph{octa}-word for 16 bytes. Set the location counter to @var{loc} in the absolute section. @var{loc} must be an absolute expression. This directive may be useful for defining symbols with absolute values. Do not confuse it with the @code{.org} -directive. +directive. @node Org @section @code{.org @var{new-lc} , @var{fill}} |