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1 files changed, 159 insertions, 0 deletions

diff --git a/gcc/init-regs.c b/gcc/init-regs.c
new file mode 100644
index 000000000..b4dd5e9a1
--- /dev/null
+++ b/gcc/init-regs.c
@@ -0,0 +1,159 @@
+/* Initialization of uninitialized regs.
+   Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "tree.h"
+#include "rtl.h"
+#include "regs.h"
+#include "expr.h"
+#include "tree-pass.h"
+#include "basic-block.h"
+#include "flags.h"
+#include "df.h"
+
+/* Check all of the uses of pseudo variables.  If any use that is MUST
+   uninitialized, add a store of 0 immediately before it.  For
+   subregs, this makes combine happy.  For full word regs, this makes
+   other optimizations, like the register allocator and the reg-stack
+   happy as well as papers over some problems on the arm and other
+   processors where certain isa constraints cannot be handled by gcc.
+   These are of the form where two operands to an insn my not be the
+   same.  The ra will only make them the same if they do not
+   interfere, and this can only happen if one is not initialized.
+
+   There is also the unfortunate consequence that this may mask some
+   buggy programs where people forget to initialize stack variable.
+   Any programmer with half a brain would look at the uninitialized
+   variable warnings.  */
+
+static void
+initialize_uninitialized_regs (void)
+{
+  basic_block bb;
+  bitmap already_genned = BITMAP_ALLOC (NULL);
+
+  if (optimize == 1)
+    {
+      df_live_add_problem ();
+      df_live_set_all_dirty ();
+    }
+
+  df_analyze ();
+
+  FOR_EACH_BB (bb)
+    {
+      rtx insn;
+      bitmap lr = DF_LR_IN (bb);
+      bitmap ur = DF_LIVE_IN (bb);
+      bitmap_clear (already_genned);
+
+      FOR_BB_INSNS (bb, insn)
+	{
+	  unsigned int uid = INSN_UID (insn);
+	  df_ref *use_rec;
+	  if (!NONDEBUG_INSN_P (insn))
+	    continue;
+
+	  for (use_rec = DF_INSN_UID_USES (uid); *use_rec; use_rec++)
+	    {
+	      df_ref use = *use_rec;
+	      unsigned int regno = DF_REF_REGNO (use);
+
+	      /* Only do this for the pseudos.  */
+	      if (regno < FIRST_PSEUDO_REGISTER)
+		continue;
+
+	      /* Do not generate multiple moves for the same regno.
+		 This is common for sequences of subreg operations.
+		 They would be deleted during combine but there is no
+		 reason to churn the system.  */
+	      if (bitmap_bit_p (already_genned, regno))
+		continue;
+
+	      /* A use is MUST uninitialized if it reaches the top of
+		 the block from the inside of the block (the lr test)
+		 and no def for it reaches the top of the block from
+		 outside of the block (the ur test).  */
+	      if (bitmap_bit_p (lr, regno)
+		  && (!bitmap_bit_p (ur, regno)))
+		{
+		  rtx move_insn;
+		  rtx reg = DF_REF_REAL_REG (use);
+
+		  bitmap_set_bit (already_genned, regno);
+
+		  start_sequence ();
+		  emit_move_insn (reg, CONST0_RTX (GET_MODE (reg)));
+		  move_insn = get_insns ();
+		  end_sequence ();
+		  emit_insn_before (move_insn, insn);
+		  if (dump_file)
+		    fprintf (dump_file,
+			     "adding initialization in %s of reg %d at in block %d for insn %d.\n",
+			     current_function_name (), regno, bb->index, uid);
+		}
+	    }
+	}
+    }
+
+  if (optimize == 1)
+    {
+      if (dump_file)
+	df_dump (dump_file);
+      df_remove_problem (df_live);
+    }
+
+  BITMAP_FREE (already_genned);
+}
+
+static bool
+gate_initialize_regs (void)
+{
+  return optimize > 0;
+}
+
+static unsigned int
+rest_of_handle_initialize_regs (void)
+{
+  initialize_uninitialized_regs ();
+  return 0;
+}
+
+struct rtl_opt_pass pass_initialize_regs =
+{
+ {
+  RTL_PASS,
+  "init-regs",                          /* name */
+  gate_initialize_regs,                 /* gate */
+  rest_of_handle_initialize_regs,       /* execute */
+  NULL,                                 /* sub */
+  NULL,                                 /* next */
+  0,                                    /* static_pass_number */
+  TV_NONE,                              /* tv_id */
+  0,                                    /* properties_required */
+  0,                                    /* properties_provided */
+  0,                                    /* properties_destroyed */
+  0,                                    /* todo_flags_start */
+  TODO_dump_func |
+  TODO_df_finish                        /* todo_flags_finish */
+ }
+};