[backport from gcc-4.7/trunk, fixes PR48770 regression from PR37273 patch <mikpe@it.uu.se>]

gcc/

2011-06-23  Jeff Law  <law@redhat.com>

	PR middle-end/48770
	* reload.h (reload): Change to return a bool.
	* ira.c (ira): If requested by reload, run a fast DCE pass after
	reload has completed.  Fix comment typo.
	* reload1.c (need_dce): New file scoped static.
	(reload): Set reload_completed here.  Return whether or not a DCE
	pass after reload is needed.
	(delete_dead_insn): Set need_dce as needed.

gcc/testsuite/

2011-06-23  Jeff Law <law@redhat.com>

	PR middle-end/48770
	* gcc.dg/pr48770.c: New test.

--- gcc-4.6.1/gcc/ira.c.~1~	2011-03-08 16:51:12.000000000 +0100
+++ gcc-4.6.1/gcc/ira.c	2011-07-06 13:15:32.000000000 +0200
@@ -321,6 +321,7 @@ along with GCC; see the file COPYING3.  
 #include "integrate.h"
 #include "ggc.h"
 #include "ira-int.h"
+#include "dce.h"
 
 
 struct target_ira default_target_ira;
@@ -3081,6 +3082,7 @@ ira (FILE *f)
   int rebuild_p;
   int saved_flag_ira_share_spill_slots;
   basic_block bb;
+  bool need_dce;
 
   timevar_push (TV_IRA);
 
@@ -3271,7 +3273,7 @@ ira (FILE *f)
   df_set_flags (DF_NO_INSN_RESCAN);
   build_insn_chain ();
 
-  reload_completed = !reload (get_insns (), ira_conflicts_p);
+  need_dce = reload (get_insns (), ira_conflicts_p);
 
   timevar_pop (TV_RELOAD);
 
@@ -3314,7 +3316,7 @@ ira (FILE *f)
 #endif
 
   /* The code after the reload has changed so much that at this point
-     we might as well just rescan everything.  Not that
+     we might as well just rescan everything.  Note that
      df_rescan_all_insns is not going to help here because it does not
      touch the artificial uses and defs.  */
   df_finish_pass (true);
@@ -3326,6 +3328,9 @@ ira (FILE *f)
   if (optimize)
     df_analyze ();
 
+  if (need_dce && optimize)
+    run_fast_dce ();
+
   timevar_pop (TV_IRA);
 }
 
--- gcc-4.6.1/gcc/reload.h.~1~	2010-08-14 23:46:11.000000000 +0200
+++ gcc-4.6.1/gcc/reload.h	2011-07-06 13:15:32.000000000 +0200
@@ -378,7 +378,7 @@ extern void reload_cse_regs (rtx);
 extern void init_reload (void);
 
 /* The reload pass itself.  */
-extern int reload (rtx, int);
+extern bool reload (rtx, int);
 
 /* Mark the slots in regs_ever_live for the hard regs
    used by pseudo-reg number REGNO.  */
--- gcc-4.6.1/gcc/reload1.c.~1~	2011-06-17 13:13:38.000000000 +0200
+++ gcc-4.6.1/gcc/reload1.c	2011-07-06 13:15:32.000000000 +0200
@@ -288,6 +288,10 @@ static char *reload_insn_firstobj;
    examine.  */
 struct insn_chain *reload_insn_chain;
 
+/* TRUE if we potentially left dead insns in the insn stream and want to
+   run DCE immediately after reload, FALSE otherwise.  */
+static bool need_dce;
+
 /* List of all insns needing reloads.  */
 static struct insn_chain *insns_need_reload;
 
@@ -711,10 +715,11 @@ static int *temp_pseudo_reg_arr;
    If GLOBAL is zero, we do not have enough information to do that,
    so any pseudo reg that is spilled must go to the stack.
 
-   Return value is nonzero if reload failed
-   and we must not do any more for this function.  */
+   Return value is TRUE if reload likely left dead insns in the
+   stream and a DCE pass should be run to elimiante them.  Else the
+   return value is FALSE.  */
 
-int
+bool
 reload (rtx first, int global)
 {
   int i, n;
@@ -1318,7 +1323,9 @@ reload (rtx first, int global)
 
   gcc_assert (bitmap_empty_p (&spilled_pseudos));
 
-  return failure;
+  reload_completed = !failure;
+
+  return need_dce;
 }
 
 /* Yet another special case.  Unfortunately, reg-stack forces people to
@@ -2115,14 +2122,19 @@ delete_dead_insn (rtx insn)
   rtx prev = prev_active_insn (insn);
   rtx prev_dest;
 
-  /* If the previous insn sets a register that dies in our insn, delete it
-     too.  */
+  /* If the previous insn sets a register that dies in our insn make
+     a note that we want to run DCE immediately after reload.
+
+     We used to delete the previous insn & recurse, but that's wrong for
+     block local equivalences.  Instead of trying to figure out the exact
+     circumstances where we can delete the potentially dead insns, just
+     let DCE do the job.  */
   if (prev && GET_CODE (PATTERN (prev)) == SET
       && (prev_dest = SET_DEST (PATTERN (prev)), REG_P (prev_dest))
       && reg_mentioned_p (prev_dest, PATTERN (insn))
       && find_regno_note (insn, REG_DEAD, REGNO (prev_dest))
       && ! side_effects_p (SET_SRC (PATTERN (prev))))
-    delete_dead_insn (prev);
+    need_dce = 1;
 
   SET_INSN_DELETED (insn);
 }
--- gcc-4.6.1/gcc/testsuite/gcc.dg/pr48770.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6.1/gcc/testsuite/gcc.dg/pr48770.c	2011-07-06 13:15:32.000000000 +0200
@@ -0,0 +1,21 @@
+/* { dg-do run } */
+/* { dg-options "-O -fprofile-arcs -fPIC -fno-dce -fno-forward-propagate" } */
+
+int test_goto2 (int f)
+{
+  int i;
+  for (i = 0; ({_Bool a = i < 10;a;}); i++)
+  {
+    if (i == f)
+      goto lab2;
+  }
+  return 4;
+lab2:
+  return 8;
+}
+
+int main ()
+{
+  test_goto2 (30);
+  return 0;
+}