gcc/doc/gcc/extensions-to-the-c-language-family/target-builtins/sh-built-in-functions.rst

   1 ..
   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 .. _sh-built-in-functions:
   7
   8 SH Built-in Functions
   9 ^^^^^^^^^^^^^^^^^^^^^
  10
  11 The following built-in functions are supported on the SH1, SH2, SH3 and SH4
  12 families of processors:
  13
  14 .. function:: void __builtin_set_thread_pointer (void *ptr)
  15
  16   Sets the :samp:`GBR` register to the specified value :samp:`{ptr}`.  This is usually
  17   used by system code that manages threads and execution contexts.  The compiler
  18   normally does not generate code that modifies the contents of :samp:`GBR` and
  19   thus the value is preserved across function calls.  Changing the :samp:`GBR`
  20   value in user code must be done with caution, since the compiler might use
  21   :samp:`GBR` in order to access thread local variables.
  22
  23 .. function:: void * __builtin_thread_pointer (void)
  24
  25   Returns the value that is currently set in the :samp:`GBR` register.
  26   Memory loads and stores that use the thread pointer as a base address are
  27   turned into :samp:`GBR` based displacement loads and stores, if possible.
  28   For example:
  29
  30   .. code-block:: c++
  31
  32     struct my_tcb
  33     {
  34        int a, b, c, d, e;
  35     };
  36
  37     int get_tcb_value (void)
  38     {
  39       // Generate mov.l @(8,gbr),r0 instruction
  40       return ((my_tcb*)__builtin_thread_pointer ())->c;
  41     }
  42
  43 .. function:: unsigned int __builtin_sh_get_fpscr (void)
  44
  45   Returns the value that is currently set in the :samp:`FPSCR` register.
  46
  47 .. function:: void __builtin_sh_set_fpscr (unsigned int val)
  48
  49   Sets the :samp:`FPSCR` register to the specified value :samp:`{val}`, while
  50   preserving the current values of the FR, SZ and PR bits.