gcc/rtlhooks.c

   1 /* Generic hooks for the RTL middle-end.
   2    Copyright (C) 2004, 2005, 2007 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "tm.h"
  24 #include "rtl.h"
  25 #include "rtlhooks-def.h"
  26 #include "expr.h"
  27 #include "recog.h"
  28 \f
  29
  30 /* For speed, we will copy the RTX hooks struct member-by-member
  31    instead of doing indirect calls.  For these reason, we initialize
  32    *two* struct rtl_hooks globals: rtl_hooks is the one that is used
  33    to actually call the hooks, while general_rtl_hooks is used
  34    to restore the hooks by passes that modify them.  */
  35
  36 const struct rtl_hooks general_rtl_hooks = RTL_HOOKS_INITIALIZER;
  37 struct rtl_hooks rtl_hooks = RTL_HOOKS_INITIALIZER;
  38
  39 rtx
  40 gen_lowpart_general (enum machine_mode mode, rtx x)
  41 {
  42   rtx result = gen_lowpart_common (mode, x);
  43
  44   if (result)
  45     return result;
  46   /* Handle SUBREGs and hard REGs that were rejected by
  47      simplify_gen_subreg.  */
  48   else if (REG_P (x) || GET_CODE (x) == SUBREG)
  49     {
  50       result = gen_lowpart_common (mode, copy_to_reg (x));
  51       gcc_assert (result != 0);
  52       return result;
  53     }
  54   else
  55     {
  56       int offset = 0;
  57
  58       /* The only additional case we can do is MEM.  */
  59       gcc_assert (MEM_P (x));
  60
  61       /* The following exposes the use of "x" to CSE.  */
  62       if (GET_MODE_SIZE (GET_MODE (x)) <= UNITS_PER_WORD
  63           && SCALAR_INT_MODE_P (GET_MODE (x))
  64           && TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
  65                                     GET_MODE_BITSIZE (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 /* Similar to gen_lowpart, but cannot emit any instruction via
  84    copy_to_reg or force_reg.  Mainly used in simplify-rtx.c.  */
  85 rtx
  86 gen_lowpart_no_emit_general (enum machine_mode mode, rtx x)
  87 {
  88   rtx result = gen_lowpart_if_possible (mode, x);
  89   if (result)
  90     return result;
  91   else
  92     return x;
  93 }
  94
  95 rtx
  96 reg_num_sign_bit_copies_general (const_rtx x ATTRIBUTE_UNUSED,
  97                                  enum machine_mode mode ATTRIBUTE_UNUSED,
  98                                  const_rtx known_x ATTRIBUTE_UNUSED,
  99                                  enum machine_mode known_mode ATTRIBUTE_UNUSED,
 100                                  unsigned int known_ret ATTRIBUTE_UNUSED,
 101                                  unsigned int *result ATTRIBUTE_UNUSED)
 102 {
 103   return NULL;
 104 }
 105
 106 rtx
 107 reg_nonzero_bits_general (const_rtx x ATTRIBUTE_UNUSED,
 108                           enum machine_mode mode ATTRIBUTE_UNUSED,
 109                           const_rtx known_x ATTRIBUTE_UNUSED,
 110                           enum machine_mode known_mode ATTRIBUTE_UNUSED,
 111                           unsigned HOST_WIDE_INT known_ret ATTRIBUTE_UNUSED,
 112                           unsigned HOST_WIDE_INT *nonzero ATTRIBUTE_UNUSED)
 113 {
 114   return NULL;
 115 }
 116
 117 bool
 118 reg_truncated_to_mode_general (enum machine_mode mode ATTRIBUTE_UNUSED,
 119                                const_rtx x ATTRIBUTE_UNUSED)
 120 {
 121   return false;
 122 }
 123
 124 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
 125    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
 126    least-significant part of X.
 127    MODE specifies how big a part of X to return.
 128
 129    If the requested operation cannot be done, 0 is returned.
 130
 131    This is similar to gen_lowpart_general.  */
 132
 133 rtx
 134 gen_lowpart_if_possible (enum machine_mode mode, rtx x)
 135 {
 136   rtx result = gen_lowpart_common (mode, x);
 137
 138   if (result)
 139     return result;
 140   else if (MEM_P (x))
 141     {
 142       /* This is the only other case we handle.  */
 143       int offset = 0;
 144       rtx new;
 145
 146       if (WORDS_BIG_ENDIAN)
 147         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
 148                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
 149       if (BYTES_BIG_ENDIAN)
 150         /* Adjust the address so that the address-after-the-data is
 151            unchanged.  */
 152         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
 153                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
 154
 155       new = adjust_address_nv (x, mode, offset);
 156       if (! memory_address_p (mode, XEXP (new, 0)))
 157         return 0;
 158
 159       return new;
 160     }
 161   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode
 162            && validate_subreg (mode, GET_MODE (x), x,
 163                                 subreg_lowpart_offset (mode, GET_MODE (x))))
 164     return gen_lowpart_SUBREG (mode, x);
 165   else
 166     return 0;
 167 }
 168 \f