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1 /* Generic hooks for the RTL middle-end.
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2 Copyright (C) 2004, 2005, 2007, 2008 Free Software Foundation, Inc.
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3
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4 This file is part of GCC.
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5
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6 GCC is free software; you can redistribute it and/or modify it under
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7 the terms of the GNU General Public License as published by the Free
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8 Software Foundation; either version 3, or (at your option) any later
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9 version.
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10
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11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
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13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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14 for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with GCC; see the file COPYING3. If not see
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18 <http://www.gnu.org/licenses/>. */
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19
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20 #include "config.h"
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21 #include "system.h"
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22 #include "coretypes.h"
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23 #include "tm.h"
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24 #include "rtl.h"
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25 #include "rtlhooks-def.h"
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26 #include "expr.h"
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27 #include "recog.h"
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28
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29
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30 /* For speed, we will copy the RTX hooks struct member-by-member
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31 instead of doing indirect calls. For these reason, we initialize
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32 *two* struct rtl_hooks globals: rtl_hooks is the one that is used
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33 to actually call the hooks, while general_rtl_hooks is used
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34 to restore the hooks by passes that modify them. */
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35
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36 const struct rtl_hooks general_rtl_hooks = RTL_HOOKS_INITIALIZER;
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37 struct rtl_hooks rtl_hooks = RTL_HOOKS_INITIALIZER;
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38
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39 rtx
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40 gen_lowpart_general (enum machine_mode mode, rtx x)
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41 {
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42 rtx result = gen_lowpart_common (mode, x);
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43
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44 if (result)
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45 return result;
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46 /* Handle SUBREGs and hard REGs that were rejected by
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47 simplify_gen_subreg. */
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48 else if (REG_P (x) || GET_CODE (x) == SUBREG)
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49 {
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50 result = gen_lowpart_common (mode, copy_to_reg (x));
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51 gcc_assert (result != 0);
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52 return result;
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53 }
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54 else
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55 {
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56 int offset = 0;
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57
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58 /* The only additional case we can do is MEM. */
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59 gcc_assert (MEM_P (x));
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60
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61 /* The following exposes the use of "x" to CSE. */
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62 if (GET_MODE_SIZE (GET_MODE (x)) <= UNITS_PER_WORD
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63 && SCALAR_INT_MODE_P (GET_MODE (x))
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64 && TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
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65 GET_MODE_BITSIZE (GET_MODE (x)))
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66 && !reload_completed)
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67 return gen_lowpart_general (mode, force_reg (GET_MODE (x), x));
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68
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69 if (WORDS_BIG_ENDIAN)
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70 offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
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71 - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
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72
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73 if (BYTES_BIG_ENDIAN)
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74 /* Adjust the address so that the address-after-the-data
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75 is unchanged. */
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76 offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
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77 - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
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78
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79 return adjust_address (x, mode, offset);
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80 }
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81 }
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82
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83 /* Similar to gen_lowpart, but cannot emit any instruction via
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84 copy_to_reg or force_reg. Mainly used in simplify-rtx.c. */
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85 rtx
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86 gen_lowpart_no_emit_general (enum machine_mode mode, rtx x)
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87 {
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88 rtx result = gen_lowpart_if_possible (mode, x);
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89 if (result)
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90 return result;
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91 else
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92 return x;
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93 }
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94
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95 rtx
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96 reg_num_sign_bit_copies_general (const_rtx x ATTRIBUTE_UNUSED,
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97 enum machine_mode mode ATTRIBUTE_UNUSED,
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98 const_rtx known_x ATTRIBUTE_UNUSED,
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99 enum machine_mode known_mode ATTRIBUTE_UNUSED,
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100 unsigned int known_ret ATTRIBUTE_UNUSED,
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101 unsigned int *result ATTRIBUTE_UNUSED)
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102 {
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103 return NULL;
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104 }
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105
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106 rtx
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107 reg_nonzero_bits_general (const_rtx x ATTRIBUTE_UNUSED,
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108 enum machine_mode mode ATTRIBUTE_UNUSED,
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109 const_rtx known_x ATTRIBUTE_UNUSED,
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110 enum machine_mode known_mode ATTRIBUTE_UNUSED,
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111 unsigned HOST_WIDE_INT known_ret ATTRIBUTE_UNUSED,
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112 unsigned HOST_WIDE_INT *nonzero ATTRIBUTE_UNUSED)
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113 {
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114 return NULL;
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115 }
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116
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117 bool
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118 reg_truncated_to_mode_general (enum machine_mode mode ATTRIBUTE_UNUSED,
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119 const_rtx x ATTRIBUTE_UNUSED)
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120 {
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121 return false;
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122 }
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123
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124 /* Assuming that X is an rtx (e.g., MEM, REG or SUBREG) for a fixed-point
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125 number, return an rtx (MEM, SUBREG, or CONST_INT) that refers to the
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126 least-significant part of X.
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127 MODE specifies how big a part of X to return.
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128
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129 If the requested operation cannot be done, 0 is returned.
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130
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131 This is similar to gen_lowpart_general. */
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132
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133 rtx
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134 gen_lowpart_if_possible (enum machine_mode mode, rtx x)
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135 {
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136 rtx result = gen_lowpart_common (mode, x);
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137
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138 if (result)
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139 return result;
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140 else if (MEM_P (x))
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141 {
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142 /* This is the only other case we handle. */
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143 int offset = 0;
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144 rtx new_rtx;
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145
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146 if (WORDS_BIG_ENDIAN)
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147 offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
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148 - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));
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149 if (BYTES_BIG_ENDIAN)
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150 /* Adjust the address so that the address-after-the-data is
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151 unchanged. */
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152 offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode))
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153 - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x))));
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154
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155 new_rtx = adjust_address_nv (x, mode, offset);
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156 if (! memory_address_p (mode, XEXP (new_rtx, 0)))
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157 return 0;
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158
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159 return new_rtx;
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160 }
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161 else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode
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162 && validate_subreg (mode, GET_MODE (x), x,
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163 subreg_lowpart_offset (mode, GET_MODE (x))))
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164 return gen_lowpart_SUBREG (mode, x);
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165 else
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166 return 0;
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167 }
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168
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