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 "rtl.h"
  25 #include "rtlhooks-def.h"
  26 #include "symtab.h"
  27 #include "hard-reg-set.h"
  28 #include "function.h"
  29 #include "flags.h"
  30 #include "alias.h"
  31 #include "tree.h"
  32 #include "insn-config.h"
  33 #include "expmed.h"
  34 #include "dojump.h"
  35 #include "explow.h"
  36 #include "calls.h"
  37 #include "emit-rtl.h"
  38 #include "varasm.h"
  39 #include "stmt.h"
  40 #include "expr.h"
  41 #include "recog.h"
  42 \f
  43
  44 /* For speed, we will copy the RTX hooks struct member-by-member
  45    instead of doing indirect calls.  For these reason, we initialize
  46    *two* struct rtl_hooks globals: rtl_hooks is the one that is used
  47    to actually call the hooks, while general_rtl_hooks is used
  48    to restore the hooks by passes that modify them.  */
  49
  50 const struct rtl_hooks general_rtl_hooks = RTL_HOOKS_INITIALIZER;
  51 struct rtl_hooks rtl_hooks = RTL_HOOKS_INITIALIZER;
  52
  53 rtx
  54 gen_lowpart_general (machine_mode mode, rtx x)
  55 {
  56   rtx result = gen_lowpart_common (mode, x);
  57
  58   if (result)
  59     return result;
  60   /* Handle SUBREGs and hard REGs that were rejected by
  61      simplify_gen_subreg.  */
  62   else if (REG_P (x) || GET_CODE (x) == SUBREG)
  63     {
  64       result = gen_lowpart_common (mode, copy_to_reg (x));
  65       gcc_assert (result != 0);
  66       return result;
  67     }
  68   else
  69     {
  70       int offset = 0;
  71
  72       /* The only additional case we can do is MEM.  */
  73       gcc_assert (MEM_P (x));
  74
  75       /* The following exposes the use of "x" to CSE.  */
  76       if (GET_MODE_SIZE (GET_MODE (x)) <= UNITS_PER_WORD
  77           && SCALAR_INT_MODE_P (GET_MODE (x))
  78           && TRULY_NOOP_TRUNCATION_MODES_P (mode, GET_MODE (x))
  79           && !reload_completed)
  80         return gen_lowpart_general (mode, force_reg (GET_MODE (x), x));
  81
  82       if (WORDS_BIG_ENDIAN)
  83         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
  84                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
  85
  86       if (BYTES_BIG_ENDIAN)
  87         /* Adjust the address so that the address-after-the-data
  88            is unchanged.  */
  89         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
  90                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
  91
  92       return adjust_address (x, mode, offset);
  93     }
  94 }
  95
  96 rtx
  97 reg_num_sign_bit_copies_general (const_rtx x ATTRIBUTE_UNUSED,
  98                                  machine_mode mode ATTRIBUTE_UNUSED,
  99                                  const_rtx known_x ATTRIBUTE_UNUSED,
 100                                  machine_mode known_mode ATTRIBUTE_UNUSED,
 101                                  unsigned int known_ret ATTRIBUTE_UNUSED,
 102                                  unsigned int *result ATTRIBUTE_UNUSED)
 103 {
 104   return NULL;
 105 }
 106
 107 rtx
 108 reg_nonzero_bits_general (const_rtx x ATTRIBUTE_UNUSED,
 109                           machine_mode mode ATTRIBUTE_UNUSED,
 110                           const_rtx known_x ATTRIBUTE_UNUSED,
 111                           machine_mode known_mode ATTRIBUTE_UNUSED,
 112                           unsigned HOST_WIDE_INT known_ret ATTRIBUTE_UNUSED,
 113                           unsigned HOST_WIDE_INT *nonzero ATTRIBUTE_UNUSED)
 114 {
 115   return NULL;
 116 }
 117
 118 bool
 119 reg_truncated_to_mode_general (machine_mode mode ATTRIBUTE_UNUSED,
 120                                const_rtx x ATTRIBUTE_UNUSED)
 121 {
 122   return false;
 123 }
 124
 125 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
 126    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
 127    least-significant part of X.
 128    MODE specifies how big a part of X to return.
 129
 130    If the requested operation cannot be done, 0 is returned.
 131
 132    This is similar to gen_lowpart_general.  */
 133
 134 rtx
 135 gen_lowpart_if_possible (machine_mode mode, rtx x)
 136 {
 137   rtx result = gen_lowpart_common (mode, x);
 138
 139   if (result)
 140     return result;
 141   else if (MEM_P (x))
 142     {
 143       /* This is the only other case we handle.  */
 144       int offset = 0;
 145       rtx new_rtx;
 146
 147       if (WORDS_BIG_ENDIAN)
 148         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
 149                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
 150       if (BYTES_BIG_ENDIAN)
 151         /* Adjust the address so that the address-after-the-data is
 152            unchanged.  */
 153         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
 154                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
 155
 156       new_rtx = adjust_address_nv (x, mode, offset);
 157       if (! memory_address_addr_space_p (mode, XEXP (new_rtx, 0),
 158                                          MEM_ADDR_SPACE (x)))
 159         return 0;
 160
 161       return new_rtx;
 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