gcc/rtlhooks.c

   1 /* Generic hooks for the RTL middle-end.
   2    Copyright (C) 2004-2020 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 #include "target.h"
  34 \f
  35
  36 /* For speed, we will copy the RTX hooks struct member-by-member
  37    instead of doing indirect calls.  For these reason, we initialize
  38    *two* struct rtl_hooks globals: rtl_hooks is the one that is used
  39    to actually call the hooks, while general_rtl_hooks is used
  40    to restore the hooks by passes that modify them.  */
  41
  42 const struct rtl_hooks general_rtl_hooks = RTL_HOOKS_INITIALIZER;
  43 struct rtl_hooks rtl_hooks = RTL_HOOKS_INITIALIZER;
  44
  45 rtx
  46 gen_lowpart_general (machine_mode mode, rtx x)
  47 {
  48   rtx result = gen_lowpart_common (mode, x);
  49
  50   if (result)
  51     return result;
  52   /* Handle SUBREGs and hard REGs that were rejected by
  53      simplify_gen_subreg.  */
  54   else if (REG_P (x) || GET_CODE (x) == SUBREG)
  55     {
  56       result = gen_lowpart_common (mode, copy_to_reg (x));
  57       gcc_assert (result != 0);
  58       return result;
  59     }
  60   else
  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       scalar_int_mode xmode;
  67       if (is_a <scalar_int_mode> (GET_MODE (x), &xmode)
  68           && GET_MODE_SIZE (xmode) <= UNITS_PER_WORD
  69           && TRULY_NOOP_TRUNCATION_MODES_P (mode, xmode)
  70           && !reload_completed)
  71         return gen_lowpart_general (mode, force_reg (xmode, x));
  72
  73       poly_int64 offset = byte_lowpart_offset (mode, GET_MODE (x));
  74       return adjust_address (x, mode, offset);
  75     }
  76 }
  77
  78 rtx
  79 reg_num_sign_bit_copies_general (const_rtx, scalar_int_mode, scalar_int_mode,
  80                                  unsigned int *)
  81 {
  82   return NULL;
  83 }
  84
  85 rtx
  86 reg_nonzero_bits_general (const_rtx, scalar_int_mode, scalar_int_mode,
  87                           unsigned HOST_WIDE_INT *)
  88 {
  89   return NULL;
  90 }
  91
  92 bool
  93 reg_truncated_to_mode_general (machine_mode mode ATTRIBUTE_UNUSED,
  94                                const_rtx x ATTRIBUTE_UNUSED)
  95 {
  96   return false;
  97 }
  98
  99 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
 100    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
 101    least-significant part of X.
 102    MODE specifies how big a part of X to return.
 103
 104    If the requested operation cannot be done, 0 is returned.
 105
 106    This is similar to gen_lowpart_general.  */
 107
 108 rtx
 109 gen_lowpart_if_possible (machine_mode mode, rtx x)
 110 {
 111   rtx result = gen_lowpart_common (mode, x);
 112
 113   if (result)
 114     return result;
 115   else if (MEM_P (x))
 116     {
 117       /* This is the only other case we handle.  */
 118       poly_int64 offset = byte_lowpart_offset (mode, GET_MODE (x));
 119       rtx new_rtx = adjust_address_nv (x, mode, offset);
 120       if (! memory_address_addr_space_p (mode, XEXP (new_rtx, 0),
 121                                          MEM_ADDR_SPACE (x)))
 122         return 0;
 123
 124       return new_rtx;
 125     }
 126   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode && !SUBREG_P (x)
 127            && validate_subreg (mode, GET_MODE (x), x,
 128                                subreg_lowpart_offset (mode, GET_MODE (x))))
 129     return gen_lowpart_SUBREG (mode, x);
 130   else
 131     return 0;
 132 }
 133 \f