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 "input.h"
  29 #include "function.h"
  30 #include "flags.h"
  31 #include "alias.h"
  32 #include "tree.h"
  33 #include "insn-config.h"
  34 #include "expmed.h"
  35 #include "dojump.h"
  36 #include "explow.h"
  37 #include "calls.h"
  38 #include "emit-rtl.h"
  39 #include "varasm.h"
  40 #include "stmt.h"
  41 #include "expr.h"
  42 #include "recog.h"
  43 \f
  44
  45 /* For speed, we will copy the RTX hooks struct member-by-member
  46    instead of doing indirect calls.  For these reason, we initialize
  47    *two* struct rtl_hooks globals: rtl_hooks is the one that is used
  48    to actually call the hooks, while general_rtl_hooks is used
  49    to restore the hooks by passes that modify them.  */
  50
  51 const struct rtl_hooks general_rtl_hooks = RTL_HOOKS_INITIALIZER;
  52 struct rtl_hooks rtl_hooks = RTL_HOOKS_INITIALIZER;
  53
  54 rtx
  55 gen_lowpart_general (machine_mode mode, rtx x)
  56 {
  57   rtx result = gen_lowpart_common (mode, x);
  58
  59   if (result)
  60     return result;
  61   /* Handle SUBREGs and hard REGs that were rejected by
  62      simplify_gen_subreg.  */
  63   else if (REG_P (x) || GET_CODE (x) == SUBREG)
  64     {
  65       result = gen_lowpart_common (mode, copy_to_reg (x));
  66       gcc_assert (result != 0);
  67       return result;
  68     }
  69   else
  70     {
  71       int offset = 0;
  72
  73       /* The only additional case we can do is MEM.  */
  74       gcc_assert (MEM_P (x));
  75
  76       /* The following exposes the use of "x" to CSE.  */
  77       if (GET_MODE_SIZE (GET_MODE (x)) <= UNITS_PER_WORD
  78           && SCALAR_INT_MODE_P (GET_MODE (x))
  79           && TRULY_NOOP_TRUNCATION_MODES_P (mode, GET_MODE (x))
  80           && !reload_completed)
  81         return gen_lowpart_general (mode, force_reg (GET_MODE (x), x));
  82
  83       if (WORDS_BIG_ENDIAN)
  84         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
  85                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
  86
  87       if (BYTES_BIG_ENDIAN)
  88         /* Adjust the address so that the address-after-the-data
  89            is unchanged.  */
  90         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
  91                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
  92
  93       return adjust_address (x, mode, offset);
  94     }
  95 }
  96
  97 rtx
  98 reg_num_sign_bit_copies_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 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                           machine_mode mode ATTRIBUTE_UNUSED,
 111                           const_rtx known_x ATTRIBUTE_UNUSED,
 112                           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 (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 (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_rtx;
 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_rtx = adjust_address_nv (x, mode, offset);
 158       if (! memory_address_addr_space_p (mode, XEXP (new_rtx, 0),
 159                                          MEM_ADDR_SPACE (x)))
 160         return 0;
 161
 162       return new_rtx;
 163     }
 164   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode
 165            && validate_subreg (mode, GET_MODE (x), x,
 166                                 subreg_lowpart_offset (mode, GET_MODE (x))))
 167     return gen_lowpart_SUBREG (mode, x);
 168   else
 169     return 0;
 170 }
 171 \f