combine: More distribute_notes trouble (PR69737)

PR64682 is a problem in distribute_notes, where it has trouble putting
a REG_DEAD note for a reg that is set twice in the right spot.  My fix
for that did the wrong thing for PR69567.  And then my attempted fix
for that one made PR64682 fail again.

Instead, let's just lose the note in such complicated cases, like we
already do in certain similar cases.


	PR rtl-optimization/64682
	PR rtl-optimization/69567
	PR rtl-optimization/69737
	* combine.c (distribute_notes) <REG_DEAD>: If the register is set
	in I2 as well, just lose it.

From-SVN: r233356

gcc/ChangeLog

+2016-02-11  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/64682
+	PR rtl-optimization/69567
+	PR rtl-optimization/69737
+	* combine.c (distribute_notes) <REG_DEAD>: If the register is set
+	in I2 as well, just lose it.
+
 2016-02-11  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_last_printed_arch_string):

gcc/combine.c

@@ -13901,7 +13901,6 @@ distribute_notes (rtx notes, rtx_insn *from_insn, rtx_insn *i3, rtx_insn *i2,
 	    tem_insn = from_insn;
 	  else
 	    {
-	      tem_insn = i3;
 	      if (from_insn
 		  && CALL_P (from_insn)
 		  && find_reg_fusage (from_insn, USE, XEXP (note, 0)))
@@ -13910,14 +13909,7 @@ distribute_notes (rtx notes, rtx_insn *from_insn, rtx_insn *i3, rtx_insn *i2,
 		place = i3;
 	      else if (i2 != 0 && next_nonnote_nondebug_insn (i2) == i3
 		       && reg_referenced_p (XEXP (note, 0), PATTERN (i2)))
-		{
-		  place = i2;
-		  /* If the new I2 sets the same register that is marked dead
-		     in the note, the note now should not be put on I2, as the
-		     note refers to a previous incarnation of the reg.  */
-		  if (reg_set_p (XEXP (note, 0), PATTERN (i2)))
-		    tem_insn = i2;
-		}
+		place = i2;
 	      else if ((rtx_equal_p (XEXP (note, 0), elim_i2)
 			&& !(i2mod
 			     && reg_overlap_mentioned_p (XEXP (note, 0),
@@ -13925,6 +13917,12 @@ distribute_notes (rtx notes, rtx_insn *from_insn, rtx_insn *i3, rtx_insn *i2,
 		       || rtx_equal_p (XEXP (note, 0), elim_i1)
 		       || rtx_equal_p (XEXP (note, 0), elim_i0))
 		break;
+	      tem_insn = i3;
+	      /* If the new I2 sets the same register that is marked dead
+		 in the note, we do not know where to put the note.
+		 Give up.  */
+	      if (i2 != 0 && reg_set_p (XEXP (note, 0), PATTERN (i2)))
+		break;
 	    }
 
 	  if (place == 0)