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1 /* Header file for SSA dominator optimizations.
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2 Copyright (C) 2013-2020 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 #ifndef GCC_TREE_SSA_SCOPED_TABLES_H
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21 #define GCC_TREE_SSA_SCOPED_TABLES_H
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22
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23 /* Representation of a "naked" right-hand-side expression, to be used
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24 in recording available expressions in the expression hash table. */
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25
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26 enum expr_kind
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27 {
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28 EXPR_SINGLE,
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29 EXPR_UNARY,
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30 EXPR_BINARY,
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31 EXPR_TERNARY,
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32 EXPR_CALL,
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33 EXPR_PHI
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34 };
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35
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36 struct hashable_expr
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37 {
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38 tree type;
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39 enum expr_kind kind;
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40 union {
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41 struct { tree rhs; } single;
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42 struct { enum tree_code op; tree opnd; } unary;
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43 struct { enum tree_code op; tree opnd0, opnd1; } binary;
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44 struct { enum tree_code op; tree opnd0, opnd1, opnd2; } ternary;
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45 struct { gcall *fn_from; bool pure; size_t nargs; tree *args; } call;
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46 struct { size_t nargs; tree *args; } phi;
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47 } ops;
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48 };
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49
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50 /* Structure for recording known value of a conditional expression.
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51
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52 Clients build vectors of these objects to record known values
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53 that occur on edges. */
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54
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55 struct cond_equivalence
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56 {
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57 /* The condition, in a HASHABLE_EXPR form. */
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58 struct hashable_expr cond;
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59
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60 /* The result of the condition (true or false. */
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61 tree value;
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62 };
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63
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64 /* Structure for entries in the expression hash table. */
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65
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66 typedef class expr_hash_elt * expr_hash_elt_t;
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67
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68 class expr_hash_elt
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69 {
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70 public:
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71 expr_hash_elt (gimple *, tree);
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72 expr_hash_elt (tree);
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73 expr_hash_elt (struct hashable_expr *, tree);
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74 expr_hash_elt (class expr_hash_elt &);
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75 ~expr_hash_elt ();
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76 void print (FILE *);
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77 tree vop (void) { return m_vop; }
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78 tree lhs (void) { return m_lhs; }
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79 struct hashable_expr *expr (void) { return &m_expr; }
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80 expr_hash_elt *stamp (void) { return m_stamp; }
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81 hashval_t hash (void) { return m_hash; }
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82
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83 private:
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84 /* The expression (rhs) we want to record. */
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85 struct hashable_expr m_expr;
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86
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87 /* The value (lhs) of this expression. */
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88 tree m_lhs;
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89
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90 /* The virtual operand associated with the nearest dominating stmt
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91 loading from or storing to expr. */
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92 tree m_vop;
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93
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94 /* The hash value for RHS. */
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95 hashval_t m_hash;
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96
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97 /* A unique stamp, typically the address of the hash
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98 element itself, used in removing entries from the table. */
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99 class expr_hash_elt *m_stamp;
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100
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101 /* We should never be making assignments between objects in this class.
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102 Though it might allow us to exploit C++11 move semantics if we
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103 defined the move constructor and move assignment operator. */
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104 expr_hash_elt& operator= (const expr_hash_elt&);
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105 };
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106
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107 /* Hashtable helpers. */
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108
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109 struct expr_elt_hasher : pointer_hash <expr_hash_elt>
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110 {
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111 static inline hashval_t hash (const value_type &p)
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112 { return p->hash (); }
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113 static bool equal (const value_type &, const compare_type &);
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114 static inline void remove (value_type &element)
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115 { delete element; }
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116 };
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117
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118
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119 /* This class defines a unwindable expression equivalence table
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120 layered on top of the expression hash table.
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121
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122 Essentially it's just a stack of available expression value pairs with
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123 a special marker (NULL, NULL) to indicate unwind points. */
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124
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125 class avail_exprs_stack
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126 {
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127 public:
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128 /* We need access to the AVAIL_EXPR hash table so that we can
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129 remove entries from the hash table when unwinding the stack. */
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130 avail_exprs_stack (hash_table<expr_elt_hasher> *table)
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131 { m_stack.create (20); m_avail_exprs = table; }
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132 ~avail_exprs_stack (void) { m_stack.release (); }
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133
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134 /* Push the unwinding marker onto the stack. */
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135 void push_marker (void) { record_expr (NULL, NULL, 'M'); }
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136
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137 /* Restore the AVAIL_EXPRs table to its state when the last marker
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138 was pushed. */
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139 void pop_to_marker (void);
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140
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141 /* Record a single available expression that can be unwound. */
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142 void record_expr (expr_hash_elt_t, expr_hash_elt_t, char);
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143
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144 /* Get the underlying hash table. Would this be better as
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145 class inheritance? */
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146 hash_table<expr_elt_hasher> *avail_exprs (void)
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147 { return m_avail_exprs; }
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148
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149 /* Lookup and conditionally insert an expression into the table,
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150 recording enough information to unwind as needed. */
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151 tree lookup_avail_expr (gimple *, bool, bool);
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152
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153 void record_cond (cond_equivalence *);
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154
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155 private:
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156 vec<std::pair<expr_hash_elt_t, expr_hash_elt_t> > m_stack;
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157 hash_table<expr_elt_hasher> *m_avail_exprs;
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158
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159 /* For some assignments where the RHS is a binary operator, if we know
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160 a equality relationship between the operands, we may be able to compute
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161 a result, even if we don't know the exact value of the operands. */
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162 tree simplify_binary_operation (gimple *, class expr_hash_elt);
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163
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164 /* We do not allow copying this object or initializing one
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165 from another. */
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166 avail_exprs_stack& operator= (const avail_exprs_stack&);
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167 avail_exprs_stack (class avail_exprs_stack &);
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168 };
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169
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170 /* This class defines an unwindable const/copy equivalence table
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171 layered on top of SSA_NAME_VALUE/set_ssa_name_value.
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172
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173 Essentially it's just a stack of name,prev value pairs with a
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174 special marker (NULL) to indicate unwind points. */
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175
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176 class const_and_copies
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177 {
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178 public:
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179 const_and_copies (void) { m_stack.create (20); };
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180 ~const_and_copies (void) { m_stack.release (); }
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181
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182 /* Push the unwinding marker onto the stack. */
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183 void push_marker (void) { m_stack.safe_push (NULL_TREE); }
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184
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185 /* Restore the const/copies table to its state when the last marker
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186 was pushed. */
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187 void pop_to_marker (void);
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188
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189 /* Record a single const/copy pair that can be unwound. This version
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190 may follow the value chain for the RHS. */
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191 void record_const_or_copy (tree, tree);
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192
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193 /* Special entry point when we want to provide an explicit previous
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194 value for the first argument. Try to get rid of this in the future.
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195
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196 This version may also follow the value chain for the RHS. */
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197 void record_const_or_copy (tree, tree, tree);
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198
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199 private:
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200 /* Record a single const/copy pair that can be unwound. This version
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201 does not follow the value chain for the RHS. */
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202 void record_const_or_copy_raw (tree, tree, tree);
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203
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204 vec<tree> m_stack;
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205 const_and_copies& operator= (const const_and_copies&);
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206 const_and_copies (class const_and_copies &);
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207 };
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208
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209 void initialize_expr_from_cond (tree cond, struct hashable_expr *expr);
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210 void record_conditions (vec<cond_equivalence> *p, tree, tree);
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211
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212 #endif /* GCC_TREE_SSA_SCOPED_TABLES_H */
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