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[/] [openrisc/] [trunk/] [gnu-stable/] [gcc-4.5.1/] [gcc/] [stack-ptr-mod.c] - Blame information for rev 859

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Line No. Rev Author Line
1 280 jeremybenn
/* Discover if the stack pointer is modified in a function.
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   Copyright (C) 2007, 2008, 2009
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   Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3.  If not see
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<http://www.gnu.org/licenses/>.  */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "tm.h"
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#include "tree.h"
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#include "rtl.h"
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#include "regs.h"
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#include "expr.h"
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#include "tree-pass.h"
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#include "basic-block.h"
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#include "flags.h"
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#include "output.h"
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#include "df.h"
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/* Determine if the stack pointer is constant over the life of the function.
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   Only useful before prologues have been emitted.  */
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static void
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notice_stack_pointer_modification_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED,
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                                     void *data ATTRIBUTE_UNUSED)
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{
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  if (x == stack_pointer_rtx
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      /* The stack pointer is only modified indirectly as the result
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         of a push until later.  See the comments in rtl.texi
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         regarding Embedded Side-Effects on Addresses.  */
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      || (MEM_P (x)
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          && GET_RTX_CLASS (GET_CODE (XEXP (x, 0))) == RTX_AUTOINC
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          && XEXP (XEXP (x, 0), 0) == stack_pointer_rtx))
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    current_function_sp_is_unchanging = 0;
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}
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static void
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notice_stack_pointer_modification (void)
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{
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  basic_block bb;
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  rtx insn;
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  /* Assume that the stack pointer is unchanging if alloca hasn't
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     been used.  */
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  current_function_sp_is_unchanging = !cfun->calls_alloca;
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  if (current_function_sp_is_unchanging)
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    FOR_EACH_BB (bb)
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      FOR_BB_INSNS (bb, insn)
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        {
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          if (INSN_P (insn))
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            {
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              /* Check if insn modifies the stack pointer.  */
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              note_stores (PATTERN (insn),
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                           notice_stack_pointer_modification_1,
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                           NULL);
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              if (! current_function_sp_is_unchanging)
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                return;
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            }
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        }
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  /* The value coming into this pass was 0, and the exit block uses
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     are based on this.  If the value is now 1, we need to redo the
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     exit block uses.  */
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  if (df && current_function_sp_is_unchanging)
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    df_update_exit_block_uses ();
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}
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  /* Some targets can emit simpler epilogues if they know that sp was
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     not ever modified during the function.  After reload, of course,
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     we've already emitted the epilogue so there's no sense searching.  */
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static unsigned int
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rest_of_handle_stack_ptr_mod (void)
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{
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  notice_stack_pointer_modification ();
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  return 0;
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}
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struct rtl_opt_pass pass_stack_ptr_mod =
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{
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 {
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  RTL_PASS,
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  "*stack_ptr_mod",                     /* name */
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  NULL,                                 /* gate */
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  rest_of_handle_stack_ptr_mod,         /* execute */
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  NULL,                                 /* sub */
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  NULL,                                 /* next */
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  0,                                    /* static_pass_number */
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  TV_NONE,                              /* tv_id */
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  0,                                    /* properties_required */
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  0,                                    /* properties_provided */
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  0,                                    /* properties_destroyed */
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  0,                                    /* todo_flags_start */
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 }
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};

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