1 /* Discover if the stack pointer is modified in a function. 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 "output.h" 58 #include "df.h" 59 60 /* Determine if the stack pointer is constant over the life of the function. 61 Only useful before prologues have been emitted. */ 62 63 static void 64 notice_stack_pointer_modification_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, 65 void *data ATTRIBUTE_UNUSED) 66 { 67 if (x == stack_pointer_rtx 68 /* The stack pointer is only modified indirectly as the result 69 of a push until later. See the comments in rtl.texi 70 regarding Embedded Side-Effects on Addresses. */ 71 || (MEM_P (x) 72 && GET_RTX_CLASS (GET_CODE (XEXP (x, 0))) == RTX_AUTOINC 73 && XEXP (XEXP (x, 0), 0) == stack_pointer_rtx)) 74 crtl->sp_is_unchanging = 0; 75 } 76 77 /* Some targets can emit simpler epilogues if they know that sp was 78 not ever modified during the function. After reload, of course, 79 we've already emitted the epilogue so there's no sense searching. */ 80 81 namespace { 82 83 const pass_data pass_data_stack_ptr_mod = 84 { 85 RTL_PASS, /* type */ 86 "*stack_ptr_mod", /* name */ 87 OPTGROUP_NONE, /* optinfo_flags */ 88 TV_NONE, /* tv_id */ 89 0, /* properties_required */ 90 0, /* properties_provided */ 91 0, /* properties_destroyed */ 92 0, /* todo_flags_start */ 93 0, /* todo_flags_finish */ 94 }; 95 96 class pass_stack_ptr_mod : public rtl_opt_pass 97 { 98 public: 99 pass_stack_ptr_mod (gcc::context *ctxt) 100 : rtl_opt_pass (pass_data_stack_ptr_mod, ctxt) 101 {} 102 103 /* opt_pass methods: */ 104 virtual unsigned int execute (function *); 105 106 }; // class pass_stack_ptr_mod 107 108 unsigned int 109 pass_stack_ptr_mod::execute (function *fun) 110 { 111 basic_block bb; 112 rtx_insn *insn; 113 114 /* Assume that the stack pointer is unchanging if alloca hasn't 115 been used. */ 116 crtl->sp_is_unchanging = !fun->calls_alloca; 117 if (crtl->sp_is_unchanging) 118 FOR_EACH_BB_FN (bb, fun) 119 FOR_BB_INSNS (bb, insn) 120 { 121 if (INSN_P (insn)) 122 { 123 /* Check if insn modifies the stack pointer. */ 124 note_stores (PATTERN (insn), 125 notice_stack_pointer_modification_1, 126 NULL); 127 if (! crtl->sp_is_unchanging) 128 return 0; 129 } 130 } 131 132 /* The value coming into this pass was 0, and the exit block uses 133 are based on this. If the value is now 1, we need to redo the 134 exit block uses. */ 135 if (df && crtl->sp_is_unchanging) 136 df_update_exit_block_uses (); 137 138 return 0; 139 } 140 141 } // anon namespace 142 143 rtl_opt_pass * 144 make_pass_stack_ptr_mod (gcc::context *ctxt) 145 { 146 return new pass_stack_ptr_mod (ctxt); 147 } 148