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   else if (REG_P (x))
  48     {
  49       /* Must be a hard reg that's not valid in MODE.  */
  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           && ! no_new_pseudos)
  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 (rtx x ATTRIBUTE_UNUSED,
  97                                  enum machine_mode mode ATTRIBUTE_UNUSED,
  98                                  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 (rtx x ATTRIBUTE_UNUSED,
 108                           enum machine_mode mode ATTRIBUTE_UNUSED,
 109                           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 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
 118    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
 119    least-significant part of X.
 120    MODE specifies how big a part of X to return.
 121
 122    If the requested operation cannot be done, 0 is returned.
 123
 124    This is similar to gen_lowpart_general.  */
 125
 126 rtx
 127 gen_lowpart_if_possible (enum machine_mode mode, rtx x)
 128 {
 129   rtx result = gen_lowpart_common (mode, x);
 130
 131   if (result)
 132     return result;
 133   else if (MEM_P (x))
 134     {
 135       /* This is the only other case we handle.  */
 136       int offset = 0;
 137       rtx new;
 138
 139       if (WORDS_BIG_ENDIAN)
 140         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
 141                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
 142       if (BYTES_BIG_ENDIAN)
 143         /* Adjust the address so that the address-after-the-data is
 144            unchanged.  */
 145         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
 146                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
 147
 148       new = adjust_address_nv (x, mode, offset);
 149       if (! memory_address_p (mode, XEXP (new, 0)))
 150         return 0;
 151
 152       return new;
 153     }
 154   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode)
 155     return gen_lowpart_SUBREG (mode, x);
 156   else
 157     return 0;
 158 }
 159 \f