gcc/rtlhooks.c

   1 /* Generic hooks for the RTL middle-end.
   2    Copyright (C) 2004-2015 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 "function.h"
  25 #include "rtl.h"
  26 #include "tree.h"
  27 #include "insn-config.h"
  28 #include "emit-rtl.h"
  29 #include "recog.h"
  30 #include "rtlhooks-def.h"
  31 #include "explow.h"
  32 \f
  33
  34 /* For speed, we will copy the RTX hooks struct member-by-member
  35    instead of doing indirect calls.  For these reason, we initialize
  36    *two* struct rtl_hooks globals: rtl_hooks is the one that is used
  37    to actually call the hooks, while general_rtl_hooks is used
  38    to restore the hooks by passes that modify them.  */
  39
  40 const struct rtl_hooks general_rtl_hooks = RTL_HOOKS_INITIALIZER;
  41 struct rtl_hooks rtl_hooks = RTL_HOOKS_INITIALIZER;
  42
  43 rtx
  44 gen_lowpart_general (machine_mode mode, rtx x)
  45 {
  46   rtx result = gen_lowpart_common (mode, x);
  47
  48   if (result)
  49     return result;
  50   /* Handle SUBREGs and hard REGs that were rejected by
  51      simplify_gen_subreg.  */
  52   else if (REG_P (x) || GET_CODE (x) == SUBREG)
  53     {
  54       result = gen_lowpart_common (mode, copy_to_reg (x));
  55       gcc_assert (result != 0);
  56       return result;
  57     }
  58   else
  59     {
  60       int offset = 0;
  61
  62       /* The only additional case we can do is MEM.  */
  63       gcc_assert (MEM_P (x));
  64
  65       /* The following exposes the use of "x" to CSE.  */
  66       if (GET_MODE_SIZE (GET_MODE (x)) <= UNITS_PER_WORD
  67           && SCALAR_INT_MODE_P (GET_MODE (x))
  68           && TRULY_NOOP_TRUNCATION_MODES_P (mode, GET_MODE (x))
  69           && !reload_completed)
  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 rtx
  87 reg_num_sign_bit_copies_general (const_rtx x ATTRIBUTE_UNUSED,
  88                                  machine_mode mode ATTRIBUTE_UNUSED,
  89                                  const_rtx known_x ATTRIBUTE_UNUSED,
  90                                  machine_mode known_mode ATTRIBUTE_UNUSED,
  91                                  unsigned int known_ret ATTRIBUTE_UNUSED,
  92                                  unsigned int *result ATTRIBUTE_UNUSED)
  93 {
  94   return NULL;
  95 }
  96
  97 rtx
  98 reg_nonzero_bits_general (const_rtx x ATTRIBUTE_UNUSED,
  99                           machine_mode mode ATTRIBUTE_UNUSED,
 100                           const_rtx known_x ATTRIBUTE_UNUSED,
 101                           machine_mode known_mode ATTRIBUTE_UNUSED,
 102                           unsigned HOST_WIDE_INT known_ret ATTRIBUTE_UNUSED,
 103                           unsigned HOST_WIDE_INT *nonzero ATTRIBUTE_UNUSED)
 104 {
 105   return NULL;
 106 }
 107
 108 bool
 109 reg_truncated_to_mode_general (machine_mode mode ATTRIBUTE_UNUSED,
 110                                const_rtx x ATTRIBUTE_UNUSED)
 111 {
 112   return false;
 113 }
 114
 115 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
 116    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
 117    least-significant part of X.
 118    MODE specifies how big a part of X to return.
 119
 120    If the requested operation cannot be done, 0 is returned.
 121
 122    This is similar to gen_lowpart_general.  */
 123
 124 rtx
 125 gen_lowpart_if_possible (machine_mode mode, rtx x)
 126 {
 127   rtx result = gen_lowpart_common (mode, x);
 128
 129   if (result)
 130     return result;
 131   else if (MEM_P (x))
 132     {
 133       /* This is the only other case we handle.  */
 134       int offset = 0;
 135       rtx new_rtx;
 136
 137       if (WORDS_BIG_ENDIAN)
 138         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
 139                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
 140       if (BYTES_BIG_ENDIAN)
 141         /* Adjust the address so that the address-after-the-data is
 142            unchanged.  */
 143         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
 144                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
 145
 146       new_rtx = adjust_address_nv (x, mode, offset);
 147       if (! memory_address_addr_space_p (mode, XEXP (new_rtx, 0),
 148                                          MEM_ADDR_SPACE (x)))
 149         return 0;
 150
 151       return new_rtx;
 152     }
 153   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode
 154            && validate_subreg (mode, GET_MODE (x), x,
 155                                 subreg_lowpart_offset (mode, GET_MODE (x))))
 156     return gen_lowpart_SUBREG (mode, x);
 157   else
 158     return 0;
 159 }
 160 \f