Index: postreload.c
===================================================================
--- postreload.c	(revision 180683)
+++ postreload.c	(working copy)
@@ -112,8 +112,8 @@ reload_cse_simplify (rtx insn, rtx testr
 	  if (REG_P (value)
 	      && ! REG_FUNCTION_VALUE_P (value))
 	    value = 0;
-	  check_for_inc_dec (insn);
-	  delete_insn_and_edges (insn);
+	  if (check_for_inc_dec (insn, NULL))
+	    delete_insn_and_edges (insn);
 	  return;
 	}
 
@@ -164,8 +164,8 @@ reload_cse_simplify (rtx insn, rtx testr
 
       if (i < 0)
 	{
-	  check_for_inc_dec (insn);
-	  delete_insn_and_edges (insn);
+	  if (check_for_inc_dec (insn, NULL))
+	    delete_insn_and_edges (insn);
 	  /* We're done with this insn.  */
 	  return;
 	}
Index: regset.h
===================================================================
--- regset.h	(revision 180683)
+++ regset.h	(working copy)
@@ -1,6 +1,6 @@
 /* Define regsets.
    Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
-   2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
+   2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -115,6 +115,9 @@ #define EXECUTE_IF_AND_IN_REG_SET(REGSET
 
 extern regset regs_invalidated_by_call_regset;
 
+/* Same information as FIXED_REG_SET but in regset form.  */
+extern regset fixed_regset;
+
 /* An obstack for regsets.  */
 extern bitmap_obstack reg_obstack;
 
Index: dse.c
===================================================================
--- dse.c	(revision 180683)
+++ dse.c	(working copy)
@@ -33,6 +33,7 @@ Software Foundation; either version 3, o
 #include "tm_p.h"
 #include "regs.h"
 #include "hard-reg-set.h"
+#include "regset.h"
 #include "flags.h"
 #include "df.h"
 #include "cselib.h"
@@ -377,6 +378,13 @@ struct insn_info
      created.  */
   read_info_t read_rec;
 
+  /* The live fixed registers.  We assume only fixed registers can
+     cause trouble by being clobbered from an expanded pattern;
+     storing only the live fixed registers (rather than all registers)
+     means less memory needs to be allocated / copied for the individual
+     stores.  */
+  regset fixed_regs_live;
+
   /* The prev insn in the basic block.  */
   struct insn_info * prev_insn;
 
@@ -448,9 +456,9 @@ struct bb_info
   /* The following bitvector is indexed by the reg number.  It
      contains the set of regs that are live at the current instruction
      being processed.  While it contains info for all of the
-     registers, only the pseudos are actually examined.  It is used to
-     assure that shift sequences that are inserted do not accidently
-     clobber live hard regs.  */
+     registers, only the hard registers are actually examined.  It is used
+     to assure that shift and/or add sequences that are inserted do not
+     accidently clobber live hard regs.  */
   bitmap regs_live;
 };
 
@@ -827,6 +835,51 @@ free_store_info (insn_info_t insn_info)
   insn_info->store_rec = NULL;
 }
 
+typedef struct
+{
+  rtx insert_before;
+  rtx first, current;
+  regset fixed_regs_live;
+  bool failure;
+} note_add_store_info;
+
+/* Callback for emit_inc_dec_insn_before via note_stores.
+   Check if a register is clobbered which is life afterwards.  */
+static void
+note_add_store (rtx loc, const_rtx expr ATTRIBUTE_UNUSED, void *data)
+{
+  rtx insn, *nextp;
+  note_add_store_info *info = (note_add_store_info *) data;
+  int r, n;
+
+  if (!REG_P (loc))
+    return;
+  /* If this register is referenced by the current or an earlier insn,
+     that's OK.  E.g. this applies to the register that is being incremented
+     with this addition.  */
+  nextp = &info->first;
+  do
+    {
+      insn = *nextp;
+      nextp = &NEXT_INSN (insn);
+      if (reg_referenced_p (loc, PATTERN (insn)))
+	return;
+    }
+  while (insn != info->current);
+
+  if (!info->fixed_regs_live)
+    {
+      info->failure =  true;
+      return;
+    }
+  /* Now check if this is a live fixed register.  */
+  r = REGNO (loc);
+  n = HARD_REGNO_NREGS (r, GET_MODE (loc));
+  while (--n >=  0)
+    if (REGNO_REG_SET_P (info->fixed_regs_live, r+n))
+      info->failure =  true;
+}
+
 /* Callback for for_each_inc_dec that emits an INSN that sets DEST to
    SRC + SRCOFF before insn ARG.  */
 
@@ -835,31 +888,62 @@ emit_inc_dec_insn_before (rtx mem ATTRIB
 			  rtx op ATTRIBUTE_UNUSED,
 			  rtx dest, rtx src, rtx srcoff, void *arg)
 {
-  rtx insn = (rtx)arg;
-
-  if (srcoff)
-    src = gen_rtx_PLUS (GET_MODE (src), src, srcoff);
+  insn_info_t insn_info = (insn_info_t) arg;
+  rtx insn = insn_info->insn, new_insn, cur;
+  note_add_store_info info;
 
   /* We can reuse all operands without copying, because we are about
      to delete the insn that contained it.  */
-
-  emit_insn_before (gen_rtx_SET (VOIDmode, dest, src), insn);
+  if (srcoff)
+    new_insn = gen_add3_insn (dest, src, srcoff);
+  else
+    new_insn = gen_move_insn (dest, src);
+  info.insert_before = insn;
+  info.first = new_insn;
+  info.fixed_regs_live = insn_info->fixed_regs_live;
+  info.failure = false;
+  for (cur = new_insn; cur; cur = NEXT_INSN (cur))
+    {
+      info.current = cur;
+      note_stores (PATTERN (cur), note_add_store, &info);
+    }
+  if (info.failure)
+    return 1;
+  emit_insn_before (new_insn, insn);
 
   return -1;
 }
 
 /* Before we delete INSN, make sure that the auto inc/dec, if it is
-   there, is split into a separate insn.  */
+   there, is split into a separate insn.
+   Return true on success (or if there was nothing to do), false on failure.  */
 
-void
-check_for_inc_dec (rtx insn)
+static bool
+check_for_inc_dec_1 (insn_info_t insn_info)
 {
+  rtx insn = insn_info->insn;
   rtx note = find_reg_note (insn, REG_INC, NULL_RTX);
   if (note)
-    for_each_inc_dec (&insn, emit_inc_dec_insn_before, insn);
+    return for_each_inc_dec (&insn, emit_inc_dec_insn_before, insn_info) == 0;
+  return true;
 }
 
 
+/* Entry point for postreload.  */
+bool
+check_for_inc_dec (rtx insn, regset fixed_regs_live)
+{
+  struct insn_info insn_info;
+  rtx note;
+
+  insn_info.insn = insn;
+  insn_info.fixed_regs_live = fixed_regs_live;
+  note = find_reg_note (insn, REG_INC, NULL_RTX);
+  if (note)
+    return for_each_inc_dec (&insn, emit_inc_dec_insn_before, &insn_info) == 0;
+  return true;
+}
+
 /* Delete the insn and free all of the fields inside INSN_INFO.  */
 
 static void
@@ -870,7 +954,8 @@ delete_dead_store_insn (insn_info_t insn
   if (!dbg_cnt (dse))
     return;
 
-  check_for_inc_dec (insn_info->insn);
+  if (!check_for_inc_dec_1 (insn_info))
+    return;
   if (dump_file)
     {
       fprintf (dump_file, "Locally deleting insn %d ",
@@ -2375,6 +2460,16 @@ get_call_args (rtx call_insn, tree fn, r
   return true;
 }
 
+/* Return a bitmap of the fixed registers contained in IN.  */
+static bitmap
+copy_fixed_regs (const_bitmap in)
+{
+  bitmap ret;
+
+  ret = ALLOC_REG_SET (NULL);
+  bitmap_and (ret, in, fixed_regset);
+  return ret;
+}
 
 /* Apply record_store to all candidate stores in INSN.  Mark INSN
    if some part of it is not a candidate store and assigns to a
@@ -2529,6 +2624,8 @@ scan_insn (bb_info_t bb_info, rtx insn)
 			  active_local_stores_len = 1;
 			  active_local_stores = NULL;
 			}
+		      insn_info->fixed_regs_live
+			= copy_fixed_regs (bb_info->regs_live);
 		      insn_info->next_local_store = active_local_stores;
 		      active_local_stores = insn_info;
 		    }
@@ -2579,6 +2676,7 @@ scan_insn (bb_info_t bb_info, rtx insn)
 	  active_local_stores_len = 1;
 	  active_local_stores = NULL;
 	}
+      insn_info->fixed_regs_live = copy_fixed_regs (bb_info->regs_live);
       insn_info->next_local_store = active_local_stores;
       active_local_stores = insn_info;
     }
@@ -3622,9 +3720,9 @@ dse_step5_nospill (void)
 		}
 	      if (deleted)
 		{
-		  if (dbg_cnt (dse))
+		  if (dbg_cnt (dse)
+		      && check_for_inc_dec_1 (insn_info))
 		    {
-		      check_for_inc_dec (insn_info->insn);
 		      delete_insn (insn_info->insn);
 		      insn_info->insn = NULL;
 		      globally_deleted++;
@@ -3702,12 +3800,12 @@ dse_step5_spill (void)
 		    deleted = false;
 		  store_info = store_info->next;
 		}
-	      if (deleted && dbg_cnt (dse))
+	      if (deleted && dbg_cnt (dse)
+		  && check_for_inc_dec_1 (insn_info))
 		{
 		  if (dump_file)
 		    fprintf (dump_file, "Spill deleting insn %d\n",
 			     INSN_UID (insn_info->insn));
-		  check_for_inc_dec (insn_info->insn);
 		  delete_insn (insn_info->insn);
 		  spill_deleted++;
 		  insn_info->insn = NULL;
Index: rtl.h
===================================================================
--- rtl.h	(revision 180683)
+++ rtl.h	(working copy)
@@ -2396,7 +2396,7 @@ extern int exp_equiv_p (const_rtx, const
 extern unsigned hash_rtx (const_rtx x, enum machine_mode, int *, int *, bool);
 
 /* In dse.c */
-extern void check_for_inc_dec (rtx insn);
+extern bool check_for_inc_dec (rtx insn, bitmap);
 
 /* In jump.c */
 extern int comparison_dominates_p (enum rtx_code, enum rtx_code);
Index: reginfo.c
===================================================================
--- reginfo.c	(revision 180683)
+++ reginfo.c	(working copy)
@@ -1,7 +1,7 @@
 /* Compute different info about registers.
    Copyright (C) 1987, 1988, 1991, 1992, 1993, 1994, 1995, 1996
    1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
-   2009, 2010  Free Software Foundation, Inc.
+   2009, 2010, 2011  Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -94,6 +94,9 @@ static tree GTY(()) global_regs_decl[FIR
    in dataflow more conveniently.  */
 regset regs_invalidated_by_call_regset;
 
+/* Same information as fixed_reg_set but in regset form.  */
+regset fixed_regset;
+
 /* The bitmap_obstack is used to hold some static variables that
    should not be reset after each function is compiled.  */
 static bitmap_obstack persistent_obstack;
@@ -451,6 +454,10 @@ init_reg_sets_1 (void)
     }
   else
     CLEAR_REG_SET (regs_invalidated_by_call_regset);
+  if (!fixed_regset)
+    fixed_regset = ALLOC_REG_SET (&persistent_obstack);
+  else
+    CLEAR_REG_SET (fixed_regset);
 
   for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
     {
@@ -462,7 +469,10 @@ init_reg_sets_1 (void)
 #endif
 
       if (fixed_regs[i])
-	SET_HARD_REG_BIT (fixed_reg_set, i);
+	{
+	  SET_HARD_REG_BIT (fixed_reg_set, i);
+	  SET_REGNO_REG_SET (fixed_regset, i);
+	}
 
       if (call_used_regs[i])
 	SET_HARD_REG_BIT (call_used_reg_set, i);
