gcc/rtlhooks.c

   1 /* Generic hooks for the RTL middle-end.
   2    Copyright (C) 2004-2017 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 "memmodel.h"
  29 #include "emit-rtl.h"
  30 #include "recog.h"
  31 #include "rtlhooks-def.h"
  32 #include "explow.h"
  33 \f
  34
  35 /* For speed, we will copy the RTX hooks struct member-by-member
  36    instead of doing indirect calls.  For these reason, we initialize
  37    *two* struct rtl_hooks globals: rtl_hooks is the one that is used
  38    to actually call the hooks, while general_rtl_hooks is used
  39    to restore the hooks by passes that modify them.  */
  40
  41 const struct rtl_hooks general_rtl_hooks = RTL_HOOKS_INITIALIZER;
  42 struct rtl_hooks rtl_hooks = RTL_HOOKS_INITIALIZER;
  43
  44 rtx
  45 gen_lowpart_general (machine_mode mode, rtx x)
  46 {
  47   rtx result = gen_lowpart_common (mode, x);
  48
  49   if (result)
  50     return result;
  51   /* Handle SUBREGs and hard REGs that were rejected by
  52      simplify_gen_subreg.  */
  53   else if (REG_P (x) || GET_CODE (x) == SUBREG)
  54     {
  55       result = gen_lowpart_common (mode, copy_to_reg (x));
  56       gcc_assert (result != 0);
  57       return result;
  58     }
  59   else
  60     {
  61       int offset = 0;
  62
  63       /* The only additional case we can do is MEM.  */
  64       gcc_assert (MEM_P (x));
  65
  66       /* The following exposes the use of "x" to CSE.  */
  67       scalar_int_mode xmode;
  68       if (is_a <scalar_int_mode> (GET_MODE (x), &xmode)
  69           && GET_MODE_SIZE (xmode) <= UNITS_PER_WORD
  70           && TRULY_NOOP_TRUNCATION_MODES_P (mode, xmode)
  71           && !reload_completed)
  72         return gen_lowpart_general (mode, force_reg (xmode, x));
  73
  74       if (WORDS_BIG_ENDIAN)
  75         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
  76                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
  77
  78       if (BYTES_BIG_ENDIAN)
  79         /* Adjust the address so that the address-after-the-data
  80            is unchanged.  */
  81         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
  82                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
  83
  84       return adjust_address (x, mode, offset);
  85     }
  86 }
  87
  88 rtx
  89 reg_num_sign_bit_copies_general (const_rtx, scalar_int_mode, scalar_int_mode,
  90                                  unsigned int *)
  91 {
  92   return NULL;
  93 }
  94
  95 rtx
  96 reg_nonzero_bits_general (const_rtx, scalar_int_mode, scalar_int_mode,
  97                           unsigned HOST_WIDE_INT *)
  98 {
  99   return NULL;
 100 }
 101
 102 bool
 103 reg_truncated_to_mode_general (machine_mode mode ATTRIBUTE_UNUSED,
 104                                const_rtx x ATTRIBUTE_UNUSED)
 105 {
 106   return false;
 107 }
 108
 109 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
 110    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
 111    least-significant part of X.
 112    MODE specifies how big a part of X to return.
 113
 114    If the requested operation cannot be done, 0 is returned.
 115
 116    This is similar to gen_lowpart_general.  */
 117
 118 rtx
 119 gen_lowpart_if_possible (machine_mode mode, rtx x)
 120 {
 121   rtx result = gen_lowpart_common (mode, x);
 122
 123   if (result)
 124     return result;
 125   else if (MEM_P (x))
 126     {
 127       /* This is the only other case we handle.  */
 128       int offset = 0;
 129       rtx new_rtx;
 130
 131       if (WORDS_BIG_ENDIAN)
 132         offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
 133                   - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
 134       if (BYTES_BIG_ENDIAN)
 135         /* Adjust the address so that the address-after-the-data is
 136            unchanged.  */
 137         offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
 138                    - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
 139
 140       new_rtx = adjust_address_nv (x, mode, offset);
 141       if (! memory_address_addr_space_p (mode, XEXP (new_rtx, 0),
 142                                          MEM_ADDR_SPACE (x)))
 143         return 0;
 144
 145       return new_rtx;
 146     }
 147   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode
 148            && validate_subreg (mode, GET_MODE (x), x,
 149                                 subreg_lowpart_offset (mode, GET_MODE (x))))
 150     return gen_lowpart_SUBREG (mode, x);
 151   else
 152     return 0;
 153 }
 154 \f