libgcc/config/spu/mfc_multi_tag_reserve.c

/* Copyright (C) 2007-2014 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#include <spu_mfcio.h>
extern vector unsigned int __mfc_tag_table;

/* Reserve a sequential group of tags for exclusive use.  The number of
   tags to be reserved is specified by the <number_of_tags> parameter.
   This routine returns the first tag ID for a sequential list of
   available tags and marks them as reserved. The reserved group
   of tags is in the range starting from the returned tag through
   the returned tag + <number_of_tags>-1.

   If the number of tags requested exceeds the number of available
   sequential tags, then MFC_DMA_TAG_INVALID is returned indicating
   that the request could not be serviced.  */

unsigned int
__mfc_multi_tag_reserve (unsigned int number_of_tags)
{
  vector unsigned int table_copy;
  vector unsigned int one = (vector unsigned int)
        { 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF };
  vector unsigned int count_busy, is_valid;
  vector unsigned int count_total;
  vector unsigned int count_avail = (vector unsigned int) { 0, 0, 0, 0 };
  vector unsigned int index = (vector unsigned int) { 0, 0, 0, 0 };

  table_copy = __mfc_tag_table;


  /* count_busy: number of consecutive busy tags
     count_avail: number of consecutive free tags
     table_copy: temporary copy of the tag table
     count_total: sum of count_busy and count_avail
     index: index of the current working tag  */
  do
    {
      table_copy = spu_sl (table_copy, count_avail);

      count_busy = spu_cntlz (table_copy);
      table_copy = spu_sl (table_copy, count_busy);
      count_avail = spu_cntlz (spu_xor(table_copy, -1));
      count_total = spu_add (count_busy, count_avail);
      index = spu_add (index, count_total);
    }
  while (spu_extract (count_avail, 0) < number_of_tags
	 && spu_extract (table_copy, 0) != 0);

  index = spu_sub (index, count_avail);

  /* is_valid is set to 0xFFFFFFFF if table_copy == 0, 0 otherwise.  */
  is_valid = spu_cmpeq (table_copy, 0);
  index = spu_sel (index, is_valid, is_valid);

  /* Now I need to actually mark the tags as used.  */
  table_copy = spu_sl (one, number_of_tags);
  table_copy = spu_rl (table_copy, -number_of_tags - spu_extract (index, 0));
  table_copy = spu_sel (table_copy, __mfc_tag_table, table_copy);
  __mfc_tag_table = spu_sel (table_copy, __mfc_tag_table, is_valid);

  return spu_extract (index, 0);
}