1 /* Initialization of uninitialized regs. 2 Copyright (C) 2007-2015 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 "hash-set.h" 25 #include "machmode.h" 26 #include "vec.h" 27 #include "double-int.h" 28 #include "input.h" 29 #include "alias.h" 30 #include "symtab.h" 31 #include "wide-int.h" 32 #include "inchash.h" 33 #include "tree.h" 34 #include "rtl.h" 35 #include "regs.h" 36 #include "hashtab.h" 37 #include "hard-reg-set.h" 38 #include "function.h" 39 #include "flags.h" 40 #include "statistics.h" 41 #include "real.h" 42 #include "fixed-value.h" 43 #include "insn-config.h" 44 #include "expmed.h" 45 #include "dojump.h" 46 #include "explow.h" 47 #include "calls.h" 48 #include "emit-rtl.h" 49 #include "varasm.h" 50 #include "stmt.h" 51 #include "expr.h" 52 #include "tree-pass.h" 53 #include "predict.h" 54 #include "dominance.h" 55 #include "cfg.h" 56 #include "basic-block.h" 57 #include "df.h" 58 59 /* Check all of the uses of pseudo variables. If any use that is MUST 60 uninitialized, add a store of 0 immediately before it. For 61 subregs, this makes combine happy. For full word regs, this makes 62 other optimizations, like the register allocator and the reg-stack 63 happy as well as papers over some problems on the arm and other 64 processors where certain isa constraints cannot be handled by gcc. 65 These are of the form where two operands to an insn my not be the 66 same. The ra will only make them the same if they do not 67 interfere, and this can only happen if one is not initialized. 68 69 There is also the unfortunate consequence that this may mask some 70 buggy programs where people forget to initialize stack variable. 71 Any programmer with half a brain would look at the uninitialized 72 variable warnings. */ 73 74 static void 75 initialize_uninitialized_regs (void) 76 { 77 basic_block bb; 78 bitmap already_genned = BITMAP_ALLOC (NULL); 79 80 if (optimize == 1) 81 { 82 df_live_add_problem (); 83 df_live_set_all_dirty (); 84 } 85 86 df_analyze (); 87 88 FOR_EACH_BB_FN (bb, cfun) 89 { 90 rtx_insn *insn; 91 bitmap lr = DF_LR_IN (bb); 92 bitmap ur = DF_LIVE_IN (bb); 93 bitmap_clear (already_genned); 94 95 FOR_BB_INSNS (bb, insn) 96 { 97 df_ref use; 98 if (!NONDEBUG_INSN_P (insn)) 99 continue; 100 101 FOR_EACH_INSN_USE (use, insn) 102 { 103 unsigned int regno = DF_REF_REGNO (use); 104 105 /* Only do this for the pseudos. */ 106 if (regno < FIRST_PSEUDO_REGISTER) 107 continue; 108 109 /* Ignore pseudo PIC register. */ 110 if (pic_offset_table_rtx 111 && regno == REGNO (pic_offset_table_rtx)) 112 continue; 113 114 /* Do not generate multiple moves for the same regno. 115 This is common for sequences of subreg operations. 116 They would be deleted during combine but there is no 117 reason to churn the system. */ 118 if (bitmap_bit_p (already_genned, regno)) 119 continue; 120 121 /* A use is MUST uninitialized if it reaches the top of 122 the block from the inside of the block (the lr test) 123 and no def for it reaches the top of the block from 124 outside of the block (the ur test). */ 125 if (bitmap_bit_p (lr, regno) 126 && (!bitmap_bit_p (ur, regno))) 127 { 128 rtx_insn *move_insn; 129 rtx reg = DF_REF_REAL_REG (use); 130 131 bitmap_set_bit (already_genned, regno); 132 133 start_sequence (); 134 emit_move_insn (reg, CONST0_RTX (GET_MODE (reg))); 135 move_insn = get_insns (); 136 end_sequence (); 137 emit_insn_before (move_insn, insn); 138 if (dump_file) 139 fprintf (dump_file, 140 "adding initialization in %s of reg %d at in block %d for insn %d.\n", 141 current_function_name (), regno, bb->index, 142 INSN_UID (insn)); 143 } 144 } 145 } 146 } 147 148 if (optimize == 1) 149 { 150 if (dump_file) 151 df_dump (dump_file); 152 df_remove_problem (df_live); 153 } 154 155 BITMAP_FREE (already_genned); 156 } 157 158 namespace { 159 160 const pass_data pass_data_initialize_regs = 161 { 162 RTL_PASS, /* type */ 163 "init-regs", /* name */ 164 OPTGROUP_NONE, /* optinfo_flags */ 165 TV_NONE, /* tv_id */ 166 0, /* properties_required */ 167 0, /* properties_provided */ 168 0, /* properties_destroyed */ 169 0, /* todo_flags_start */ 170 TODO_df_finish, /* todo_flags_finish */ 171 }; 172 173 class pass_initialize_regs : public rtl_opt_pass 174 { 175 public: 176 pass_initialize_regs (gcc::context *ctxt) 177 : rtl_opt_pass (pass_data_initialize_regs, ctxt) 178 {} 179 180 /* opt_pass methods: */ 181 virtual bool gate (function *) { return optimize > 0; } 182 virtual unsigned int execute (function *) 183 { 184 initialize_uninitialized_regs (); 185 return 0; 186 } 187 188 }; // class pass_initialize_regs 189 190 } // anon namespace 191 192 rtl_opt_pass * 193 make_pass_initialize_regs (gcc::context *ctxt) 194 { 195 return new pass_initialize_regs (ctxt); 196 } 197