Line data    Source code

       1              : /* Discover if the stack pointer is modified in a function.
       2              :    Copyright (C) 2007-2026 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 "backend.h"
      24              : #include "rtl.h"
      25              : #include "df.h"
      26              : #include "memmodel.h"
      27              : #include "emit-rtl.h"
      28              : #include "tree-pass.h"
      29              : 
      30              : /* Determine if the stack pointer is constant over the life of the function.
      31              :    Only useful before prologues have been emitted.  */
      32              : 
      33              : static void
      34     65800983 : notice_stack_pointer_modification_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED,
      35              :                                      void *data ATTRIBUTE_UNUSED)
      36              : {
      37     65800983 :   if (x == stack_pointer_rtx
      38              :       /* The stack pointer is only modified indirectly as the result
      39              :          of a push until later.  See the comments in rtl.texi
      40              :          regarding Embedded Side-Effects on Addresses.  */
      41     65643131 :       || (MEM_P (x)
      42      8341862 :           && GET_RTX_CLASS (GET_CODE (XEXP (x, 0))) == RTX_AUTOINC
      43        36101 :           && XEXP (XEXP (x, 0), 0) == stack_pointer_rtx))
      44       193953 :     crtl->sp_is_unchanging = 0;
      45     65800983 : }
      46              : 
      47              :   /* Some targets can emit simpler epilogues if they know that sp was
      48              :      not ever modified during the function.  After reload, of course,
      49              :      we've already emitted the epilogue so there's no sense searching.  */
      50              : 
      51              : namespace {
      52              : 
      53              : const pass_data pass_data_stack_ptr_mod =
      54              : {
      55              :   RTL_PASS, /* type */
      56              :   "*stack_ptr_mod", /* name */
      57              :   OPTGROUP_NONE, /* optinfo_flags */
      58              :   TV_NONE, /* tv_id */
      59              :   0, /* properties_required */
      60              :   0, /* properties_provided */
      61              :   0, /* properties_destroyed */
      62              :   0, /* todo_flags_start */
      63              :   0, /* todo_flags_finish */
      64              : };
      65              : 
      66              : class pass_stack_ptr_mod : public rtl_opt_pass
      67              : {
      68              : public:
      69       285722 :   pass_stack_ptr_mod (gcc::context *ctxt)
      70       571444 :     : rtl_opt_pass (pass_data_stack_ptr_mod, ctxt)
      71              :   {}
      72              : 
      73              :   /* opt_pass methods: */
      74              :   unsigned int execute (function *) final override;
      75              : 
      76              : }; // class pass_stack_ptr_mod
      77              : 
      78              : unsigned int
      79      1471361 : pass_stack_ptr_mod::execute (function *fun)
      80              : {
      81      1471361 :   basic_block bb;
      82      1471361 :   rtx_insn *insn;
      83              : 
      84              :   /* Assume that the stack pointer is unchanging if alloca hasn't
      85              :      been used.  */
      86      1471361 :   crtl->sp_is_unchanging = !fun->calls_alloca;
      87      1471361 :   if (crtl->sp_is_unchanging)
      88     12868657 :     FOR_EACH_BB_FN (bb, fun)
      89    135878152 :       FOR_BB_INSNS (bb, insn)
      90              :         {
      91    124465298 :           if (INSN_P (insn))
      92              :             {
      93              :               /* Check if insn modifies the stack pointer.  */
      94    103012516 :               note_stores (insn, notice_stack_pointer_modification_1, NULL);
      95    103012516 :               if (! crtl->sp_is_unchanging)
      96              :                 return 0;
      97              :             }
      98              :         }
      99              : 
     100              :   /* The value coming into this pass was 0, and the exit block uses
     101              :      are based on this.  If the value is now 1, we need to redo the
     102              :      exit block uses.  */
     103      1277408 :   if (df && crtl->sp_is_unchanging)
     104      1261850 :     df_update_exit_block_uses ();
     105              : 
     106              :   return 0;
     107              : }
     108              : 
     109              : } // anon namespace
     110              : 
     111              : rtl_opt_pass *
     112       285722 : make_pass_stack_ptr_mod (gcc::context *ctxt)
     113              : {
     114       285722 :   return new pass_stack_ptr_mod (ctxt);
     115              : }