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   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. _s-390-function-attributes:
   7
   8 S/390 Function Attributes
   9 ^^^^^^^^^^^^^^^^^^^^^^^^^
  10
  11 These function attributes are supported on the S/390:
  12
  13 .. index:: hotpatch function attribute, S/390
  14
  15 .. s-390-fn-attr:: hotpatch (halfwords-before-function-label,halfwords-after-function-label)
  16
  17   On S/390 System z targets, you can use this function attribute to
  18   make GCC generate a 'hot-patching' function prologue.  If the
  19   :option:`-mhotpatch=` command-line option is used at the same time,
  20   the ``hotpatch`` attribute takes precedence.  The first of the
  21   two arguments specifies the number of halfwords to be added before
  22   the function label.  A second argument can be used to specify the
  23   number of halfwords to be added after the function label.  For
  24   both arguments the maximum allowed value is 1000000.
  25
  26   If both arguments are zero, hotpatching is disabled.
  27
  28 .. index:: target function attribute
  29
  30 .. s-390-fn-attr:: target (options)
  31
  32   As discussed in :ref:`common-function-attributes`, this attribute
  33   allows specification of target-specific compilation options.
  34
  35   On S/390, the following options are supported:
  36
  37   :samp:`arch=` :samp:`tune=` :samp:`stack-guard=` :samp:`stack-size=` :samp:`branch-cost=`
  38   :samp:`warn-framesize=` :samp:`backchain` :samp:`no-backchain` :samp:`hard-dfp`
  39   :samp:`no-hard-dfp` :samp:`hard-float` :samp:`soft-float` :samp:`htm` :samp:`no-htm`
  40   :samp:`vx` :samp:`no-vx` :samp:`packed-stack` :samp:`no-packed-stack` :samp:`small-exec`
  41   :samp:`no-small-exec` :samp:`mvcle` :samp:`no-mvcle` :samp:`warn-dynamicstack`
  42   :samp:`no-warn-dynamicstack`
  43
  44   The options work exactly like the S/390 specific command line
  45   options (without the prefix :samp:`-m`) except that they do not
  46   change any feature macros.  For example,
  47
  48   .. code-block:: c++
  49
  50     target("no-vx")
  51
  52   does not undefine the ``__VEC__`` macro.