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   /* If it's a REG, it must be a hard reg that's not valid in MODE.  */
  47   else if (REG_P (x)
  48            /* Or we could have a subreg of a floating point value.  */
  49            || (GET_CODE (x) == SUBREG
  50                && FLOAT_MODE_P (GET_MODE (SUBREG_REG (x)))))
  51     {
  52       result = gen_lowpart_common (mode, copy_to_reg (x));
  53       gcc_assert (result != 0);
  54       return result;
  55     }
  56   else
  57     {
  58       int offset = 0;
  59
  60       /* The only additional case we can do is MEM.  */
  61       gcc_assert (MEM_P (x));
  62
  63       /* The following exposes the use of "x" to CSE.  */
  64       if (GET_MODE_SIZE (GET_MODE (x)) <= UNITS_PER_WORD
  65           && SCALAR_INT_MODE_P (GET_MODE (x))
  66           && TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
  67                                     GET_MODE_BITSIZE (GET_MODE (x)))
  68           && !reload_completed)
  69         return gen_lowpart_general (mode, force_reg (GET_MODE (x), x));
  70
  71       if (WORDS_BIG_ENDIAN)
  72         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
  73                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
  74
  75       if (BYTES_BIG_ENDIAN)
  76         /* Adjust the address so that the address-after-the-data
  77            is unchanged.  */
  78         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
  79                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
  80
  81       return adjust_address (x, mode, offset);
  82     }
  83 }
  84
  85 /* Similar to gen_lowpart, but cannot emit any instruction via
  86    copy_to_reg or force_reg.  Mainly used in simplify-rtx.c.  */
  87 rtx
  88 gen_lowpart_no_emit_general (enum machine_mode mode, rtx x)
  89 {
  90   rtx result = gen_lowpart_if_possible (mode, x);
  91   if (result)
  92     return result;
  93   else
  94     return x;
  95 }
  96
  97 rtx
  98 reg_num_sign_bit_copies_general (const_rtx x ATTRIBUTE_UNUSED,
  99                                  enum machine_mode mode ATTRIBUTE_UNUSED,
 100                                  const_rtx known_x ATTRIBUTE_UNUSED,
 101                                  enum machine_mode known_mode ATTRIBUTE_UNUSED,
 102                                  unsigned int known_ret ATTRIBUTE_UNUSED,
 103                                  unsigned int *result ATTRIBUTE_UNUSED)
 104 {
 105   return NULL;
 106 }
 107
 108 rtx
 109 reg_nonzero_bits_general (const_rtx x ATTRIBUTE_UNUSED,
 110                           enum machine_mode mode ATTRIBUTE_UNUSED,
 111                           const_rtx known_x ATTRIBUTE_UNUSED,
 112                           enum machine_mode known_mode ATTRIBUTE_UNUSED,
 113                           unsigned HOST_WIDE_INT known_ret ATTRIBUTE_UNUSED,
 114                           unsigned HOST_WIDE_INT *nonzero ATTRIBUTE_UNUSED)
 115 {
 116   return NULL;
 117 }
 118
 119 bool
 120 reg_truncated_to_mode_general (enum machine_mode mode ATTRIBUTE_UNUSED,
 121                                const_rtx x ATTRIBUTE_UNUSED)
 122 {
 123   return false;
 124 }
 125
 126 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
 127    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
 128    least-significant part of X.
 129    MODE specifies how big a part of X to return.
 130
 131    If the requested operation cannot be done, 0 is returned.
 132
 133    This is similar to gen_lowpart_general.  */
 134
 135 rtx
 136 gen_lowpart_if_possible (enum machine_mode mode, rtx x)
 137 {
 138   rtx result = gen_lowpart_common (mode, x);
 139
 140   if (result)
 141     return result;
 142   else if (MEM_P (x))
 143     {
 144       /* This is the only other case we handle.  */
 145       int offset = 0;
 146       rtx new;
 147
 148       if (WORDS_BIG_ENDIAN)
 149         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
 150                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
 151       if (BYTES_BIG_ENDIAN)
 152         /* Adjust the address so that the address-after-the-data is
 153            unchanged.  */
 154         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
 155                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
 156
 157       new = adjust_address_nv (x, mode, offset);
 158       if (! memory_address_p (mode, XEXP (new, 0)))
 159         return 0;
 160
 161       return new;
 162     }
 163   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode
 164            && validate_subreg (mode, GET_MODE (x), x,
 165                                 subreg_lowpart_offset (mode, GET_MODE (x))))
 166     return gen_lowpart_SUBREG (mode, x);
 167   else
 168     return 0;
 169 }
 170 \f