PR rtl-optimization/29329

	* combine.c (replaced_rhs_insn): Rename to i2mod.
	(replaced_rhs_value): Rename to i2mod_new_rhs.
	(i2mod_old_rhs): New global variable.
	(combine_instructions): Adjust for above change.  Save a copy of
	the old RHS into i2mod_old_rhs when the contents of a REG_EQUAL
	note are substituted in the second instruction.
	(distribute_notes) <REG_DEAD>: Adjust for above change.  Do not
	ditch the note if it pertains to the second eliminated register
	and this register is mentioned in i2mod_old_rhs.

	Revert:
	2006-09-12  Eric Botcazou  <ebotcazou@libertysurf.fr>

	* combine.c (distribute_notes) <REG_DEAD>: Do not consider SETs past
	the insn to which the note was originally attached.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@121037 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 71 insertions, 22 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a201681e4dc..da8bbf58caf 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,22 @@
+2007-01-21  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+	PR rtl-optimization/29329
+	* combine.c (replaced_rhs_insn): Rename to i2mod.
+	(replaced_rhs_value): Rename to i2mod_new_rhs.
+	(i2mod_old_rhs): New global variable.
+	(combine_instructions): Adjust for above change.  Save a copy of
+	the old RHS into i2mod_old_rhs when the contents of a REG_EQUAL
+	note are substituted in the second instruction.
+	(distribute_notes) <REG_DEAD>: Adjust for above change.  Do not
+	ditch the note if it pertains to the second eliminated register
+	and this register is mentioned in i2mod_old_rhs.
+
+	Revert:
+	2006-09-12  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+	* combine.c (distribute_notes) <REG_DEAD>: Do not consider SETs past
+	the insn to which the note was originally attached.
+
 2007-01-21  Jan Hubicka  <jh@suse.cz>
 
 	* ipa-inline.c (inlining_mode): Comment, move up.
diff --git a/gcc/combine.c b/gcc/combine.c
index 32117bee219..aa1e2ce2034 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -123,16 +123,22 @@ static int combine_successes;
 
 static int total_attempts, total_merges, total_extras, total_successes;
 
-/* Sometimes combine tries to replace the right hand side of an insn
-   with the value of a REG_EQUAL note.  This is the insn that has been
-   so modified, or null if none.  */
+/* combine_instructions may try to replace the right hand side of the
+   second instruction with the value of an associated REG_EQUAL note
+   before throwing it at try_combine.  That is problematic when there
+   is a REG_DEAD note for a register used in the old right hand side
+   and can cause distribute_notes to do wrong things.  This is the
+   second instruction if it has been so modified, null otherwise.  */
 
-static rtx replaced_rhs_insn;
+static rtx i2mod;
 
-/* When REPLACED_RHS_INSN is nonnull, this is a copy of the new right
-   hand side.  */
+/* When I2MOD is nonnull, this is a copy of the old right hand side.  */
 
-static rtx replaced_rhs_value;
+static rtx i2mod_old_rhs;
+
+/* When I2MOD is nonnull, this is a copy of the new right hand side.  */
+
+static rtx i2mod_new_rhs;
 
 /* Vector mapping INSN_UIDs to cuids.
    The cuids are like uids but increase monotonically always.
@@ -932,11 +938,12 @@ combine_instructions (rtx f, unsigned int nregs)
 			 be deleted or recognized by try_combine.  */
 		      rtx orig = SET_SRC (set);
 		      SET_SRC (set) = note;
-		      replaced_rhs_insn = temp;
-		      replaced_rhs_value = copy_rtx (note);
-		      next = try_combine (insn, temp, NULL_RTX,
+		      i2mod = temp;
+		      i2mod_old_rhs = copy_rtx (orig);
+		      i2mod_new_rhs = copy_rtx (note);
+		      next = try_combine (insn, i2mod, NULL_RTX,
 					  &new_direct_jump_p);
-		      replaced_rhs_insn = NULL;
+		      i2mod = NULL_RTX;
 		      if (next)
 			goto retry;
 		      SET_SRC (set) = orig;
@@ -12140,8 +12147,8 @@ distribute_notes (rtx notes, rtx from_insn, rtx i3, rtx i2, rtx elim_i2,
 	     use of A and put the death note there.  */
 
 	  if (from_insn
-	      && from_insn == replaced_rhs_insn
-	      && !reg_overlap_mentioned_p (XEXP (note, 0), replaced_rhs_value))
+	      && from_insn == i2mod
+	      && !reg_overlap_mentioned_p (XEXP (note, 0), i2mod_new_rhs))
 	    tem = from_insn;
 	  else
 	    {
@@ -12154,7 +12161,10 @@ distribute_notes (rtx notes, rtx from_insn, rtx i3, rtx i2, rtx elim_i2,
 	      else if (i2 != 0 && next_nonnote_insn (i2) == i3
 		       && reg_referenced_p (XEXP (note, 0), PATTERN (i2)))
 		place = i2;
-	      else if (rtx_equal_p (XEXP (note, 0), elim_i2)
+	      else if ((rtx_equal_p (XEXP (note, 0), elim_i2)
+			&& !(i2mod
+			     && reg_overlap_mentioned_p (XEXP (note, 0),
+							 i2mod_old_rhs)))
 		       || rtx_equal_p (XEXP (note, 0), elim_i1))
 		break;
 	      tem = i3;
@@ -12173,14 +12183,12 @@ distribute_notes (rtx notes, rtx from_insn, rtx i3, rtx i2, rtx elim_i2,
 		      continue;
 		    }
 
-		  /* If TEM is a (reaching) definition of the use to which the
-		     note was attached, see if that is all TEM is doing.  If so,
-		     delete TEM.  Otherwise, make this into a REG_UNUSED note
-		     instead.  Don't delete sets to global register vars.  */
-		  if ((!from_insn
-		       || INSN_CUID (tem) < INSN_CUID (from_insn))
-		      && (REGNO (XEXP (note, 0)) >= FIRST_PSEUDO_REGISTER
-			  || !global_regs[REGNO (XEXP (note, 0))])
+		  /* If the register is being set at TEM, see if that is all
+		     TEM is doing.  If so, delete TEM.  Otherwise, make this
+		     into a REG_UNUSED note instead. Don't delete sets to
+		     global register vars.  */
+		  if ((REGNO (XEXP (note, 0)) >= FIRST_PSEUDO_REGISTER
+		       || !global_regs[REGNO (XEXP (note, 0))])
 		      && reg_set_p (XEXP (note, 0), PATTERN (tem)))
 		    {
 		      rtx set = single_set (tem);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e92e40bcf4f..ff69cda1751 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2007-01-21  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+	* gcc.c-torture/compile/20070121.c: New test.
+
 2007-01-21  Thomas Koenig  <Thomas.Koenig@online.de>
 
 	PR libfortran/30525
diff --git a/gcc/testsuite/gcc.c-torture/compile/20070121.c b/gcc/testsuite/gcc.c-torture/compile/20070121.c
new file mode 100644
index 00000000000..88af8bf6286
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/20070121.c
@@ -0,0 +1,18 @@
+/* PR rtl-optimization/29329 */
+/* Origin: Debian GCC Maintainers <debian-gcc@lists.debian.org> */
+/* Testcase by: Andrew Pinski <pinskia@gmail.com> */
+
+struct node234_Tag
+{
+  int t1;
+  int kids[4];
+  void *elems[3];
+};
+
+void *add234_internal(struct node234_Tag *n, int ei)
+{
+  int j;
+  for (j = ei; j < 2 && n->elems[j+1];)
+    j++;
+  n->kids[j+1] = 0;
+}