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      1 /* Generic hooks for the RTL middle-end.
      2    Copyright (C) 2004-2022 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 
     35 
     37 /* For speed, we will copy the RTX hooks struct member-by-member
     38    instead of doing indirect calls.  For these reason, we initialize
     39    *two* struct rtl_hooks globals: rtl_hooks is the one that is used
     40    to actually call the hooks, while general_rtl_hooks is used
     41    to restore the hooks by passes that modify them.  */
     42 
     43 const struct rtl_hooks general_rtl_hooks = RTL_HOOKS_INITIALIZER;
     44 struct rtl_hooks rtl_hooks = RTL_HOOKS_INITIALIZER;
     45 
     46 rtx
     47 gen_lowpart_general (machine_mode mode, rtx x)
     48 {
     49   rtx result = gen_lowpart_common (mode, x);
     50 
     51   if (result)
     52     return result;
     53   /* Handle SUBREGs and hard REGs that were rejected by
     54      simplify_gen_subreg.  */
     55   else if (REG_P (x) || GET_CODE (x) == SUBREG)
     56     {
     57       result = gen_lowpart_common (mode, copy_to_reg (x));
     58       gcc_assert (result != 0);
     59       return result;
     60     }
     61   else
     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       poly_int64 offset = byte_lowpart_offset (mode, GET_MODE (x));
     75       return adjust_address (x, mode, offset);
     76     }
     77 }
     78 
     79 rtx
     80 reg_num_sign_bit_copies_general (const_rtx, scalar_int_mode, scalar_int_mode,
     81 				 unsigned int *)
     82 {
     83   return NULL;
     84 }
     85 
     86 rtx
     87 reg_nonzero_bits_general (const_rtx, scalar_int_mode, scalar_int_mode,
     88 			  unsigned HOST_WIDE_INT *)
     89 {
     90   return NULL;
     91 }
     92 
     93 bool
     94 reg_truncated_to_mode_general (machine_mode mode ATTRIBUTE_UNUSED,
     95 			       const_rtx x ATTRIBUTE_UNUSED)
     96 {
     97   return false;
     98 }
     99 
    100 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
    101    number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
    102    least-significant part of X.
    103    MODE specifies how big a part of X to return.
    104 
    105    If the requested operation cannot be done, 0 is returned.
    106 
    107    This is similar to gen_lowpart_general.  */
    108 
    109 rtx
    110 gen_lowpart_if_possible (machine_mode mode, rtx x)
    111 {
    112   rtx result = gen_lowpart_common (mode, x);
    113 
    114   if (result)
    115     return result;
    116   else if (MEM_P (x))
    117     {
    118       /* This is the only other case we handle.  */
    119       poly_int64 offset = byte_lowpart_offset (mode, GET_MODE (x));
    120       rtx new_rtx = adjust_address_nv (x, mode, offset);
    121       if (! memory_address_addr_space_p (mode, XEXP (new_rtx, 0),
    122 					 MEM_ADDR_SPACE (x)))
    123 	return 0;
    124 
    125       return new_rtx;
    126     }
    127   else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode && !SUBREG_P (x)
    128 	   && validate_subreg (mode, GET_MODE (x), x,
    129 			       subreg_lowpart_offset (mode, GET_MODE (x))))
    130     return gen_lowpart_SUBREG (mode, x);
    131   else
    132     return 0;
    133 }
    134 
    135