159 lines
4.6 KiB
C
159 lines
4.6 KiB
C
/* Initialization of uninitialized regs.
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Copyright (C) 2007, 2008, 2009 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 "df.h"
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/* Check all of the uses of pseudo variables. If any use that is MUST
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uninitialized, add a store of 0 immediately before it. For
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subregs, this makes combine happy. For full word regs, this makes
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other optimizations, like the register allocator and the reg-stack
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happy as well as papers over some problems on the arm and other
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processors where certain isa constraints cannot be handled by gcc.
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These are of the form where two operands to an insn my not be the
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same. The ra will only make them the same if they do not
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interfere, and this can only happen if one is not initialized.
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There is also the unfortunate consequence that this may mask some
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buggy programs where people forget to initialize stack variable.
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Any programmer with half a brain would look at the uninitialized
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variable warnings. */
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static void
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initialize_uninitialized_regs (void)
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{
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basic_block bb;
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bitmap already_genned = BITMAP_ALLOC (NULL);
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if (optimize == 1)
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{
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df_live_add_problem ();
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df_live_set_all_dirty ();
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}
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df_analyze ();
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FOR_EACH_BB (bb)
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{
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rtx insn;
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bitmap lr = DF_LR_IN (bb);
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bitmap ur = DF_LIVE_IN (bb);
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bitmap_clear (already_genned);
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FOR_BB_INSNS (bb, insn)
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{
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unsigned int uid = INSN_UID (insn);
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df_ref *use_rec;
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if (!NONDEBUG_INSN_P (insn))
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continue;
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for (use_rec = DF_INSN_UID_USES (uid); *use_rec; use_rec++)
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{
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df_ref use = *use_rec;
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unsigned int regno = DF_REF_REGNO (use);
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/* Only do this for the pseudos. */
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if (regno < FIRST_PSEUDO_REGISTER)
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continue;
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/* Do not generate multiple moves for the same regno.
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This is common for sequences of subreg operations.
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They would be deleted during combine but there is no
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reason to churn the system. */
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if (bitmap_bit_p (already_genned, regno))
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continue;
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/* A use is MUST uninitialized if it reaches the top of
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the block from the inside of the block (the lr test)
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and no def for it reaches the top of the block from
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outside of the block (the ur test). */
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if (bitmap_bit_p (lr, regno)
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&& (!bitmap_bit_p (ur, regno)))
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{
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rtx move_insn;
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rtx reg = DF_REF_REAL_REG (use);
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bitmap_set_bit (already_genned, regno);
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start_sequence ();
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emit_move_insn (reg, CONST0_RTX (GET_MODE (reg)));
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move_insn = get_insns ();
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end_sequence ();
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emit_insn_before (move_insn, insn);
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if (dump_file)
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fprintf (dump_file,
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"adding initialization in %s of reg %d at in block %d for insn %d.\n",
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current_function_name (), regno, bb->index, uid);
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}
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}
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}
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}
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if (optimize == 1)
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{
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if (dump_file)
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df_dump (dump_file);
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df_remove_problem (df_live);
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}
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BITMAP_FREE (already_genned);
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}
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static bool
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gate_initialize_regs (void)
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{
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return optimize > 0;
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}
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static unsigned int
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rest_of_handle_initialize_regs (void)
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{
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initialize_uninitialized_regs ();
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return 0;
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}
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struct rtl_opt_pass pass_initialize_regs =
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{
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{
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RTL_PASS,
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"init-regs", /* name */
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gate_initialize_regs, /* gate */
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rest_of_handle_initialize_regs, /* 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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TODO_df_finish /* todo_flags_finish */
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}
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};
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