gcc/rtlhooks.c

   1 /* Generic hooks for the RTL middle-end.
   2    Copyright (C) 2004, 2005, 2007, 2008, 2009, 2011, 2012
   3    Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "tm.h"
  25 #include "rtl.h"
  26 #include "rtlhooks-def.h"
  27 #include "expr.h"
  28 #include "recog.h"
  29 \f
  30
  31 /* For speed, we will copy the RTX hooks struct member-by-member
  32    instead of doing indirect calls.  For these reason, we initialize
  33    *two* struct rtl_hooks globals: rtl_hooks is the one that is used
  34    to actually call the hooks, while general_rtl_hooks is used
  35    to restore the hooks by passes that modify them.  */
  36
  37 const struct rtl_hooks general_rtl_hooks = RTL_HOOKS_INITIALIZER;
  38 struct rtl_hooks rtl_hooks = RTL_HOOKS_INITIALIZER;
  39
  40 rtx
  41 gen_lowpart_general (enum machine_mode mode, rtx x)
  42 {
  43   rtx result = gen_lowpart_common (mode, x);
  44
  45   if (result)
  46     return result;
  47   /* Handle SUBREGs and hard REGs that were rejected by
  48      simplify_gen_subreg.  */
  49   else if (REG_P (x) || GET_CODE (x) == SUBREG)
  50     {
  51       result = gen_lowpart_common (mode, copy_to_reg (x));
  52       gcc_assert (result != 0);
  53       return result;
  54     }
  55   else
  56     {
  57       int offset = 0;
  58
  59       /* The only additional case we can do is MEM.  */
  60       gcc_assert (MEM_P (x));
  61
  62       /* The following exposes the use of "x" to CSE.  */
  63       if (GET_MODE_SIZE (GET_MODE (x)) <= UNITS_PER_WORD
  64           && SCALAR_INT_MODE_P (GET_MODE (x))
  65           && TRULY_NOOP_TRUNCATION_MODES_P (mode, GET_MODE (x))
  66           && !reload_completed)
  67         return gen_lowpart_general (mode, force_reg (GET_MODE (x), x));
  68
  69       if (WORDS_BIG_ENDIAN)
  70         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
  71                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
  72
  73       if (BYTES_BIG_ENDIAN)
  74         /* Adjust the address so that the address-after-the-data
  75            is unchanged.  */
  76         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
  77                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
  78
  79       return adjust_address (x, mode, offset);
  80     }
  81 }
  82
  83 rtx
  84 reg_num_sign_bit_copies_general (const_rtx x ATTRIBUTE_UNUSED,
  85                                  enum machine_mode mode ATTRIBUTE_UNUSED,
  86                                  const_rtx known_x ATTRIBUTE_UNUSED,
  87                                  enum machine_mode known_mode ATTRIBUTE_UNUSED,
  88                                  unsigned int known_ret ATTRIBUTE_UNUSED,
  89                                  unsigned int *result ATTRIBUTE_UNUSED)
  90 {
  91   return NULL;
  92 }
  93
  94 rtx
  95 reg_nonzero_bits_general (const_rtx x ATTRIBUTE_UNUSED,
  96                           enum machine_mode mode ATTRIBUTE_UNUSED,
  97                           const_rtx known_x ATTRIBUTE_UNUSED,
  98                           enum machine_mode known_mode ATTRIBUTE_UNUSED,
  99                           unsigned HOST_WIDE_INT known_ret ATTRIBUTE_UNUSED,
 100                           unsigned HOST_WIDE_INT *nonzero ATTRIBUTE_UNUSED)
 101 {
 102   return NULL;
 103 }
 104
 105 bool
 106 reg_truncated_to_mode_general (enum machine_mode mode ATTRIBUTE_UNUSED,
 107                                const_rtx x ATTRIBUTE_UNUSED)
 108 {
 109   return false;
 110 }
 111
 112 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
 113    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
 114    least-significant part of X.
 115    MODE specifies how big a part of X to return.
 116
 117    If the requested operation cannot be done, 0 is returned.
 118
 119    This is similar to gen_lowpart_general.  */
 120
 121 rtx
 122 gen_lowpart_if_possible (enum machine_mode mode, rtx x)
 123 {
 124   rtx result = gen_lowpart_common (mode, x);
 125
 126   if (result)
 127     return result;
 128   else if (MEM_P (x))
 129     {
 130       /* This is the only other case we handle.  */
 131       int offset = 0;
 132       rtx new_rtx;
 133
 134       if (WORDS_BIG_ENDIAN)
 135         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
 136                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
 137       if (BYTES_BIG_ENDIAN)
 138         /* Adjust the address so that the address-after-the-data is
 139            unchanged.  */
 140         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
 141                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
 142
 143       new_rtx = adjust_address_nv (x, mode, offset);
 144       if (! memory_address_addr_space_p (mode, XEXP (new_rtx, 0),
 145                                          MEM_ADDR_SPACE (x)))
 146         return 0;
 147
 148       return new_rtx;
 149     }
 150   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode
 151            && validate_subreg (mode, GET_MODE (x), x,
 152                                 subreg_lowpart_offset (mode, GET_MODE (x))))
 153     return gen_lowpart_SUBREG (mode, x);
 154   else
 155     return 0;
 156 }
 157 \f