gcc/rtlhooks.c

   1 /* Generic hooks for the RTL middle-end.
   2    Copyright (C) 2004, 2005 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 2, 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 COPYING.  If not, write to the Free
  18 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301, USA.  */
  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   /* If it's a REG, it must be a hard reg that's not valid in MODE.  */
  48   else if (REG_P (x)
  49            /* Or we could have a subreg of a floating point value.  */
  50            || (GET_CODE (x) == SUBREG
  51                && FLOAT_MODE_P (GET_MODE (SUBREG_REG (x)))))
  52     {
  53       result = gen_lowpart_common (mode, copy_to_reg (x));
  54       gcc_assert (result != 0);
  55       return result;
  56     }
  57   else
  58     {
  59       int offset = 0;
  60
  61       /* The only additional case we can do is MEM.  */
  62       gcc_assert (MEM_P (x));
  63
  64       /* The following exposes the use of "x" to CSE.  */
  65       if (GET_MODE_SIZE (GET_MODE (x)) <= UNITS_PER_WORD
  66           && SCALAR_INT_MODE_P (GET_MODE (x))
  67           && TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
  68                                     GET_MODE_BITSIZE (GET_MODE (x)))
  69           && ! no_new_pseudos)
  70         return gen_lowpart_general (mode, force_reg (GET_MODE (x), x));
  71
  72       if (WORDS_BIG_ENDIAN)
  73         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
  74                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
  75
  76       if (BYTES_BIG_ENDIAN)
  77         /* Adjust the address so that the address-after-the-data
  78            is unchanged.  */
  79         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
  80                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
  81
  82       return adjust_address (x, mode, offset);
  83     }
  84 }
  85
  86 /* Similar to gen_lowpart, but cannot emit any instruction via
  87    copy_to_reg or force_reg.  Mainly used in simplify-rtx.c.  */
  88 rtx
  89 gen_lowpart_no_emit_general (enum machine_mode mode, rtx x)
  90 {
  91   rtx result = gen_lowpart_if_possible (mode, x);
  92   if (result)
  93     return result;
  94   else
  95     return x;
  96 }
  97
  98 rtx
  99 reg_num_sign_bit_copies_general (rtx x ATTRIBUTE_UNUSED,
 100                                  enum machine_mode mode ATTRIBUTE_UNUSED,
 101                                  rtx known_x ATTRIBUTE_UNUSED,
 102                                  enum machine_mode known_mode ATTRIBUTE_UNUSED,
 103                                  unsigned int known_ret ATTRIBUTE_UNUSED,
 104                                  unsigned int *result ATTRIBUTE_UNUSED)
 105 {
 106   return NULL;
 107 }
 108
 109 rtx
 110 reg_nonzero_bits_general (rtx x ATTRIBUTE_UNUSED,
 111                           enum machine_mode mode ATTRIBUTE_UNUSED,
 112                           rtx known_x ATTRIBUTE_UNUSED,
 113                           enum machine_mode known_mode ATTRIBUTE_UNUSED,
 114                           unsigned HOST_WIDE_INT known_ret ATTRIBUTE_UNUSED,
 115                           unsigned HOST_WIDE_INT *nonzero ATTRIBUTE_UNUSED)
 116 {
 117   return NULL;
 118 }
 119
 120 bool
 121 reg_truncated_to_mode_general (enum machine_mode mode ATTRIBUTE_UNUSED,
 122                                rtx x ATTRIBUTE_UNUSED)
 123 {
 124   return false;
 125 }
 126
 127 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
 128    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
 129    least-significant part of X.
 130    MODE specifies how big a part of X to return.
 131
 132    If the requested operation cannot be done, 0 is returned.
 133
 134    This is similar to gen_lowpart_general.  */
 135
 136 rtx
 137 gen_lowpart_if_possible (enum machine_mode mode, rtx x)
 138 {
 139   rtx result = gen_lowpart_common (mode, x);
 140
 141   if (result)
 142     return result;
 143   else if (MEM_P (x))
 144     {
 145       /* This is the only other case we handle.  */
 146       int offset = 0;
 147       rtx new;
 148
 149       if (WORDS_BIG_ENDIAN)
 150         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
 151                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
 152       if (BYTES_BIG_ENDIAN)
 153         /* Adjust the address so that the address-after-the-data is
 154            unchanged.  */
 155         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
 156                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
 157
 158       new = adjust_address_nv (x, mode, offset);
 159       if (! memory_address_p (mode, XEXP (new, 0)))
 160         return 0;
 161
 162       return new;
 163     }
 164   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode)
 165     return gen_lowpart_SUBREG (mode, x);
 166   else
 167     return 0;
 168 }
 169 \f