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111
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1 /* Analyze functions to determine if callers need to allocate a frame header
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2 on the stack. The frame header is used by callees to save their arguments.
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3 This optimization is specific to TARGET_OLDABI targets. For TARGET_NEWABI
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4 targets, if a frame header is required, it is allocated by the callee.
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5
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6
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131
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7 Copyright (C) 2015-2018 Free Software Foundation, Inc.
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111
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8
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9 This file is part of GCC.
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10
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11 GCC is free software; you can redistribute it and/or modify it
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12 under the terms of the GNU General Public License as published by the
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13 Free Software Foundation; either version 3, or (at your option) any
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14 later version.
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15
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16 GCC is distributed in the hope that it will be useful, but WITHOUT
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17 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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18 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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19 for more details.
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20
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21 You should have received a copy of the GNU General Public License
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22 along with GCC; see the file COPYING3. If not see
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23 <http://www.gnu.org/licenses/>. */
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24
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25
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131
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26 #define IN_TARGET_CODE 1
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27
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111
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28 #include "config.h"
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29 #include "system.h"
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30 #include "context.h"
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31 #include "coretypes.h"
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131
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32 #include "backend.h"
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111
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33 #include "tree.h"
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34 #include "tree-core.h"
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35 #include "tree-pass.h"
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36 #include "target.h"
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37 #include "target-globals.h"
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38 #include "profile-count.h"
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39 #include "cgraph.h"
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40 #include "function.h"
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41 #include "basic-block.h"
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42 #include "gimple.h"
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43 #include "gimple-iterator.h"
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44 #include "gimple-walk.h"
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45
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46 static unsigned int frame_header_opt (void);
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47
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48 namespace {
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49
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50 const pass_data pass_data_ipa_frame_header_opt =
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51 {
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52 IPA_PASS, /* type */
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53 "frame-header-opt", /* name */
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54 OPTGROUP_NONE, /* optinfo_flags */
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55 TV_CGRAPHOPT, /* tv_id */
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56 0, /* properties_required */
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57 0, /* properties_provided */
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58 0, /* properties_destroyed */
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59 0, /* todo_flags_start */
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60 0, /* todo_flags_finish */
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61 };
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62
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63 class pass_ipa_frame_header_opt : public ipa_opt_pass_d
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64 {
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65 public:
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66 pass_ipa_frame_header_opt (gcc::context *ctxt)
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67 : ipa_opt_pass_d (pass_data_ipa_frame_header_opt, ctxt,
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68 NULL, /* generate_summary */
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69 NULL, /* write_summary */
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70 NULL, /* read_summary */
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71 NULL, /* write_optimization_summary */
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72 NULL, /* read_optimization_summary */
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73 NULL, /* stmt_fixup */
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74 0, /* function_transform_todo_flags_start */
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75 NULL, /* function_transform */
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76 NULL) /* variable_transform */
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77 {}
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78
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79 /* opt_pass methods: */
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80 virtual bool gate (function *)
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81 {
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82 /* This optimization has no affect if TARGET_NEWABI. If optimize
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83 is not at least 1 then the data needed for the optimization is
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84 not available and nothing will be done anyway. */
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85 return TARGET_OLDABI && flag_frame_header_optimization && optimize > 0;
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86 }
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87
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88 virtual unsigned int execute (function *) { return frame_header_opt (); }
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89
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90 }; // class pass_ipa_frame_header_opt
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91
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92 } // anon namespace
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93
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94 static ipa_opt_pass_d *
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95 make_pass_ipa_frame_header_opt (gcc::context *ctxt)
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96 {
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97 return new pass_ipa_frame_header_opt (ctxt);
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98 }
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99
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100 void
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101 mips_register_frame_header_opt (void)
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102 {
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103 opt_pass *p = make_pass_ipa_frame_header_opt (g);
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131
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104 struct register_pass_info f = { p, "comdats", 1, PASS_POS_INSERT_AFTER };
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111
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105 register_pass (&f);
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106 }
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107
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108
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109 /* Return true if it is certain that this is a leaf function. False if it is
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110 not a leaf function or if it is impossible to tell. */
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111
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112 static bool
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113 is_leaf_function (function *fn)
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114 {
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115 basic_block bb;
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116 gimple_stmt_iterator gsi;
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117
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118 /* If we do not have a cfg for this function be conservative and assume
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119 it is not a leaf function. */
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120 if (fn->cfg == NULL)
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121 return false;
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122
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123 FOR_EACH_BB_FN (bb, fn)
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124 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
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125 if (is_gimple_call (gsi_stmt (gsi)))
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126 return false;
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127 return true;
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128 }
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129
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130 /* Return true if this function has inline assembly code or if we cannot
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131 be certain that it does not. False if we know that there is no inline
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132 assembly. */
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133
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134 static bool
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135 has_inlined_assembly (function *fn)
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136 {
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137 basic_block bb;
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138 gimple_stmt_iterator gsi;
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139
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140 /* If we do not have a cfg for this function be conservative and assume
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141 it is may have inline assembly. */
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142 if (fn->cfg == NULL)
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143 return true;
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144
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145 FOR_EACH_BB_FN (bb, fn)
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146 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
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147 if (gimple_code (gsi_stmt (gsi)) == GIMPLE_ASM)
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148 return true;
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149
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150 return false;
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151 }
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152
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153 /* Return true if this function will use the stack space allocated by its
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154 caller or if we cannot determine for certain that it does not. */
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155
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156 static bool
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157 needs_frame_header_p (function *fn)
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158 {
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159 tree t;
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160
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161 if (fn->decl == NULL)
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162 return true;
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163
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164 if (fn->stdarg)
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165 return true;
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166
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167 for (t = DECL_ARGUMENTS (fn->decl); t; t = TREE_CHAIN (t))
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168 {
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169 if (!use_register_for_decl (t))
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170 return true;
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171
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172 /* Some 64-bit types may get copied to general registers using the frame
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173 header, see mips_output_64bit_xfer. Checking for SImode only may be
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174 overly restrictive but it is guaranteed to be safe. */
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175 if (DECL_MODE (t) != SImode)
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176 return true;
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177 }
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178
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179 return false;
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180 }
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181
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182 /* Return true if the argument stack space allocated by function FN is used.
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183 Return false if the space is needed or if the need for the space cannot
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184 be determined. */
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185
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186 static bool
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187 callees_functions_use_frame_header (function *fn)
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188 {
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189 basic_block bb;
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190 gimple_stmt_iterator gsi;
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191 gimple *stmt;
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192 tree called_fn_tree;
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193 function *called_fn;
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194
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195 if (fn->cfg == NULL)
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196 return true;
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197
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198 FOR_EACH_BB_FN (bb, fn)
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199 {
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200 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
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201 {
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202 stmt = gsi_stmt (gsi);
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203 if (is_gimple_call (stmt))
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204 {
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205 called_fn_tree = gimple_call_fndecl (stmt);
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206 if (called_fn_tree != NULL)
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207 {
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208 called_fn = DECL_STRUCT_FUNCTION (called_fn_tree);
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209 if (called_fn == NULL
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210 || DECL_WEAK (called_fn_tree)
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211 || has_inlined_assembly (called_fn)
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212 || !is_leaf_function (called_fn)
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213 || !called_fn->machine->does_not_use_frame_header)
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214 return true;
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215 }
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216 else
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217 return true;
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218 }
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219 }
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220 }
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221 return false;
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222 }
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223
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224 /* Set the callers_may_not_allocate_frame flag for any function which
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225 function FN calls because FN may not allocate a frame header. */
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226
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227 static void
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228 set_callers_may_not_allocate_frame (function *fn)
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229 {
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230 basic_block bb;
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231 gimple_stmt_iterator gsi;
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232 gimple *stmt;
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233 tree called_fn_tree;
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234 function *called_fn;
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235
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236 if (fn->cfg == NULL)
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237 return;
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238
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239 FOR_EACH_BB_FN (bb, fn)
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240 {
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241 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
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242 {
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243 stmt = gsi_stmt (gsi);
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244 if (is_gimple_call (stmt))
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245 {
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246 called_fn_tree = gimple_call_fndecl (stmt);
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247 if (called_fn_tree != NULL)
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248 {
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249 called_fn = DECL_STRUCT_FUNCTION (called_fn_tree);
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250 if (called_fn != NULL)
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251 called_fn->machine->callers_may_not_allocate_frame = true;
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252 }
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253 }
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254 }
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255 }
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256 return;
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257 }
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258
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259 /* Scan each function to determine those that need its frame headers. Perform
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260 a second scan to determine if the allocation can be skipped because none of
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261 their callees require the frame header. */
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262
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263 static unsigned int
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264 frame_header_opt ()
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265 {
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266 struct cgraph_node *node;
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267 function *fn;
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268
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269 FOR_EACH_DEFINED_FUNCTION (node)
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270 {
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271 fn = node->get_fun ();
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272 if (fn != NULL)
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273 fn->machine->does_not_use_frame_header = !needs_frame_header_p (fn);
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274 }
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275
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276 FOR_EACH_DEFINED_FUNCTION (node)
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277 {
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278 fn = node->get_fun ();
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279 if (fn != NULL)
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280 fn->machine->optimize_call_stack
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281 = !callees_functions_use_frame_header (fn) && !is_leaf_function (fn);
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282 }
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283
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284 FOR_EACH_DEFINED_FUNCTION (node)
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285 {
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286 fn = node->get_fun ();
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287 if (fn != NULL && fn->machine->optimize_call_stack)
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288 set_callers_may_not_allocate_frame (fn);
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289 }
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290
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291 return 0;
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292 }
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