re PR rtl-optimization/83496 (wrong code generated with -Os -mbranch-cost=1)

	PR rtl-optimization/83496
	* reorg.c (steal_delay_list_from_target): Change REDUNDANT array from
	booleans to RTXes.  Call fix_reg_dead_note on every non-null element.
	(steal_delay_list_from_fallthrough): Call fix_reg_dead_note on a
	redundant insn, if any.
	(relax_delay_slots): Likewise.
	(update_reg_unused_notes): Rename REDUNDANT_INSN to OTHER_INSN.

From-SVN: r257996

gcc/ChangeLog

+2018-02-26  Eric Botcazou  <ebotcazou@adacore.com>
+
+	PR rtl-optimization/83496
+	* reorg.c (steal_delay_list_from_target): Change REDUNDANT array from
+	booleans to RTX.  Call fix_reg_dead_note on every non-null element.
+	(steal_delay_list_from_fallthrough): Call fix_reg_dead_note on a
+	redundant insn, if any.
+	(relax_delay_slots): Likewise.
+	(update_reg_unused_notes): Rename REDUNDANT_INSN to OTHER_INSN.
+
 2018-02-26  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	PR tree-optimization/83965

gcc/reorg.c

@@ -1036,7 +1036,8 @@ check_annul_list_true_false (int annul_true_p,
 
 static void
 steal_delay_list_from_target (rtx_insn *insn, rtx condition, rtx_sequence *seq,
-			      vec<rtx_insn *> *delay_list, resources *sets,
+			      vec<rtx_insn *> *delay_list,
+			      struct resources *sets,
 			      struct resources *needed,
 			      struct resources *other_needed,
 			      int slots_to_fill, int *pslots_filled,
@@ -1049,7 +1050,7 @@ steal_delay_list_from_target (rtx_insn *insn, rtx condition, rtx_sequence *seq,
   int used_annul = 0;
   int i;
   struct resources cc_set;
-  bool *redundant;
+  rtx_insn **redundant;
 
   /* We can't do anything if there are more delay slots in SEQ than we
      can handle, or if we don't know that it will be a taken branch.
@@ -1088,7 +1089,7 @@ steal_delay_list_from_target (rtx_insn *insn, rtx condition, rtx_sequence *seq,
   if (! targetm.can_follow_jump (insn, seq->insn (0)))
     return;
 
-  redundant = XALLOCAVEC (bool, XVECLEN (seq, 0));
+  redundant = XALLOCAVEC (rtx_insn *, XVECLEN (seq, 0));
   for (i = 1; i < seq->len (); i++)
     {
       rtx_insn *trial = seq->insn (i);
@@ -1152,7 +1153,10 @@ steal_delay_list_from_target (rtx_insn *insn, rtx condition, rtx_sequence *seq,
      we therefore decided not to copy.  */
   for (i = 1; i < seq->len (); i++)
     if (redundant[i])
-      update_block (seq->insn (i), insn);
+      {
+	fix_reg_dead_note (redundant[i], insn);
+	update_block (seq->insn (i), insn);
+      }
 
   /* Show the place to which we will be branching.  */
   *pnew_thread = first_active_target_insn (JUMP_LABEL (seq->insn (0)));
@@ -1199,6 +1203,7 @@ steal_delay_list_from_fallthrough (rtx_insn *insn, rtx condition,
   for (i = 1; i < seq->len (); i++)
     {
       rtx_insn *trial = seq->insn (i);
+      rtx_insn *prior_insn;
 
       /* If TRIAL sets CC0, stealing it will move it too far from the use
 	 of CC0.  */
@@ -1210,8 +1215,9 @@ steal_delay_list_from_fallthrough (rtx_insn *insn, rtx condition,
 	break;
 
       /* If this insn was already done, we don't need it.  */
-      if (redundant_insn (trial, insn, *delay_list))
+      if ((prior_insn = redundant_insn (trial, insn, *delay_list)))
 	{
+	  fix_reg_dead_note (prior_insn, insn);
 	  update_block (trial, insn);
 	  delete_from_delay_slot (trial);
 	  continue;
@@ -1791,15 +1797,14 @@ fix_reg_dead_note (rtx_insn *start_insn, rtx stop_insn)
       }
 }
 
-/* Delete any REG_UNUSED notes that exist on INSN but not on REDUNDANT_INSN.
+/* Delete any REG_UNUSED notes that exist on INSN but not on OTHER_INSN.
 
    This handles the case of udivmodXi4 instructions which optimize their
-   output depending on whether any REG_UNUSED notes are present.
-   we must make sure that INSN calculates as many results as REDUNDANT_INSN
-   does.  */
+   output depending on whether any REG_UNUSED notes are present.  We must
+   make sure that INSN calculates as many results as OTHER_INSN does.  */
 
 static void
-update_reg_unused_notes (rtx_insn *insn, rtx redundant_insn)
+update_reg_unused_notes (rtx_insn *insn, rtx other_insn)
 {
   rtx link, next;
 
@@ -1811,8 +1816,7 @@ update_reg_unused_notes (rtx_insn *insn, rtx redundant_insn)
 	  || !REG_P (XEXP (link, 0)))
 	continue;
 
-      if (! find_regno_note (redundant_insn, REG_UNUSED,
-			     REGNO (XEXP (link, 0))))
+      if (!find_regno_note (other_insn, REG_UNUSED, REGNO (XEXP (link, 0))))
 	remove_note (insn, link);
     }
 }
@@ -2325,9 +2329,8 @@ follow_jumps (rtx label, rtx_insn *jump, bool *crossing)
    taken and THREAD_IF_TRUE is set.  This is used for the branch at the
    end of a loop back up to the top.
 
-   OWN_THREAD and OWN_OPPOSITE_THREAD are true if we are the only user of the
-   thread.  I.e., it is the fallthrough code of our jump or the target of the
-   jump when we are the only jump going there.
+   OWN_THREAD is true if we are the only user of the thread, i.e. it is
+   the target of the jump when we are the only jump going there.
 
    If OWN_THREAD is false, it must be the "true" thread of a jump.  In that
    case, we can only take insns from the head of the thread for our delay
@@ -3118,7 +3121,7 @@ relax_delay_slots (rtx_insn *first)
   /* Look at every JUMP_INSN and see if we can improve it.  */
   for (insn = first; insn; insn = next)
     {
-      rtx_insn *other;
+      rtx_insn *other, *prior_insn;
       bool crossing;
 
       next = next_active_insn (insn);
@@ -3224,8 +3227,9 @@ relax_delay_slots (rtx_insn *first)
       /* See if the first insn in the delay slot is redundant with some
 	 previous insn.  Remove it from the delay slot if so; then set up
 	 to reprocess this insn.  */
-      if (redundant_insn (pat->insn (1), delay_insn, vNULL))
+      if ((prior_insn = redundant_insn (pat->insn (1), delay_insn, vNULL)))
 	{
+	  fix_reg_dead_note (prior_insn, insn);
 	  update_block (pat->insn (1), insn);
 	  delete_from_delay_slot (pat->insn (1));
 	  next = prev_active_insn (next);

gcc/testsuite/ChangeLog

+2018-02-26  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc.c-torture/execute/20180226-1.c: New test.
+
 2018-02-26  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	PR tree-optimization/83965

gcc/testsuite/gcc.c-torture/execute/20180226-1.c

+/home/eric/build/gcc/mips-linux/pr83496.c
\ No newline at end of file