tree-ssa-reassoc.c (repropagate_negates): Merge negates also into MINUS_EXPRs.

	* tree-ssa-reassoc.c (repropagate_negates): Merge negates also
	into MINUS_EXPRs.
	(can_reassociate_p): New function.
	(break_up_subtract_bb, reassociate_bb): Use it.

testsuite/
	* gcc.dg/tree-ssa/negate.c: New testcase.

From-SVN: r158265

gcc/ChangeLog

+2010-04-13  Michael Matz  <matz@suse.de>
+
+	* tree-ssa-reassoc.c (repropagate_negates): Merge negates also
+	into MINUS_EXPRs.
+	(can_reassociate_p): New function.
+	(break_up_subtract_bb, reassociate_bb): Use it.
+
 2010-04-13  Richard Guenther  <rguenther@suse.de>
 
 	PR bootstrap/43737

gcc/testsuite/ChangeLog

+2010-04-13  Michael Matz  <matz@suse.de>
+
+	* gcc.dg/tree-ssa/negate.c: New testcase.
+
 2010-04-13  Richard Guenther  <rguenther@suse.de>
 
 	PR testsuite/43735

gcc/testsuite/gcc.dg/tree-ssa/negate.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-reassoc1" } */
+
+int f (int a, int b)
+{
+  int x = -a;
+  int y = b - x;
+  return y;
+}
+
+int g (int a, int b)
+{
+  int x = -a;
+  int y = x - b;
+  return y;
+}
+
+/* There should be two additions now.  */
+/* { dg-final { scan-tree-dump-times "\\+" 2 "reassoc1"} } */
+/* { dg-final { cleanup-tree-dump "reassoc1" } } */

gcc/tree-ssa-reassoc.c

@@ -1707,14 +1707,15 @@ repropagate_negates (void)
     {
       gimple user = get_single_immediate_use (negate);
 
+      if (!user || !is_gimple_assign (user))
+	continue;
+
       /* The negate operand can be either operand of a PLUS_EXPR
 	 (it can be the LHS if the RHS is a constant for example).
 
 	 Force the negate operand to the RHS of the PLUS_EXPR, then
 	 transform the PLUS_EXPR into a MINUS_EXPR.  */
-      if (user
-	  && is_gimple_assign (user)
-	  && gimple_assign_rhs_code (user) == PLUS_EXPR)
+      if (gimple_assign_rhs_code (user) == PLUS_EXPR)
 	{
 	  /* If the negated operand appears on the LHS of the
 	     PLUS_EXPR, exchange the operands of the PLUS_EXPR
@@ -1737,9 +1738,63 @@ repropagate_negates (void)
 	      update_stmt (user);
 	    }
 	}
+      else if (gimple_assign_rhs_code (user) == MINUS_EXPR)
+	{
+	  if (gimple_assign_rhs1 (user) == negate)
+	    {
+	      /* We have
+	           x = -a
+		   y = x - b
+		 which we transform into
+		   x = a + b
+		   y = -x .
+		 This pushes down the negate which we possibly can merge
+		 into some other operation, hence insert it into the
+		 plus_negates vector.  */
+	      gimple feed = SSA_NAME_DEF_STMT (negate);
+	      tree a = gimple_assign_rhs1 (feed);
+	      tree rhs2 = gimple_assign_rhs2 (user);
+	      gimple_stmt_iterator gsi = gsi_for_stmt (feed), gsi2;
+	      gimple_replace_lhs (feed, negate);
+	      gimple_assign_set_rhs_with_ops (&gsi, PLUS_EXPR, a, rhs2);
+	      update_stmt (gsi_stmt (gsi));
+	      gsi2 = gsi_for_stmt (user);
+	      gimple_assign_set_rhs_with_ops (&gsi2, NEGATE_EXPR, negate, NULL);
+	      update_stmt (gsi_stmt (gsi2));
+	      gsi_move_before (&gsi, &gsi2);
+	      VEC_safe_push (tree, heap, plus_negates,
+			     gimple_assign_lhs (gsi_stmt (gsi2)));
+	    }
+	  else
+	    {
+	      /* Transform "x = -a; y = b - x" into "y = b + a", getting
+	         rid of one operation.  */
+	      gimple feed = SSA_NAME_DEF_STMT (negate);
+	      tree a = gimple_assign_rhs1 (feed);
+	      tree rhs1 = gimple_assign_rhs1 (user);
+	      gimple_stmt_iterator gsi = gsi_for_stmt (user);
+	      gimple_assign_set_rhs_with_ops (&gsi, PLUS_EXPR, rhs1, a);
+	      update_stmt (gsi_stmt (gsi));
+	    }
+	}
     }
 }
 
+/* Returns true if OP is of a type for which we can do reassociation.
+   That is for integral or non-saturating fixed-point types, and for
+   floating point type when associative-math is enabled.  */
+
+static bool
+can_reassociate_p (tree op)
+{
+  tree type = TREE_TYPE (op);
+  if (INTEGRAL_TYPE_P (type)
+      || NON_SAT_FIXED_POINT_TYPE_P (type)
+      || (flag_associative_math && SCALAR_FLOAT_TYPE_P (type)))
+    return true;
+  return false;
+}
+
 /* Break up subtract operations in block BB.
 
    We do this top down because we don't know whether the subtract is
@@ -1768,27 +1823,15 @@ break_up_subtract_bb (basic_block bb)
       gimple stmt = gsi_stmt (gsi);
       gimple_set_visited (stmt, false);
 
+      if (!is_gimple_assign (stmt)
+	  || !can_reassociate_p (gimple_assign_lhs (stmt)))
+	continue;
+
       /* Look for simple gimple subtract operations.  */
-      if (is_gimple_assign (stmt)
-	  && gimple_assign_rhs_code (stmt) == MINUS_EXPR)
+      if (gimple_assign_rhs_code (stmt) == MINUS_EXPR)
 	{
-	  tree lhs = gimple_assign_lhs (stmt);
-	  tree rhs1 = gimple_assign_rhs1 (stmt);
-	  tree rhs2 = gimple_assign_rhs2 (stmt);
-
-	  /* If associative-math we can do reassociation for
-	     non-integral types.  Or, we can do reassociation for
-	     non-saturating fixed-point types.  */
-	  if ((!INTEGRAL_TYPE_P (TREE_TYPE (lhs))
-	       || !INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
-	       || !INTEGRAL_TYPE_P (TREE_TYPE (rhs2)))
-	      && (!SCALAR_FLOAT_TYPE_P (TREE_TYPE (lhs))
-		  || !SCALAR_FLOAT_TYPE_P (TREE_TYPE(rhs1))
-		  || !SCALAR_FLOAT_TYPE_P (TREE_TYPE(rhs2))
-		  || !flag_associative_math)
-	      && (!NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE (lhs))
-		  || !NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE(rhs1))
-		  || !NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE(rhs2))))
+	  if (!can_reassociate_p (gimple_assign_rhs1 (stmt))
+	      || !can_reassociate_p (gimple_assign_rhs2 (stmt)))
 	    continue;
 
 	  /* Check for a subtract used only in an addition.  If this
@@ -1798,6 +1841,9 @@ break_up_subtract_bb (basic_block bb)
 	  if (should_break_up_subtract (stmt))
 	    break_up_subtract (stmt, &gsi);
 	}
+      else if (gimple_assign_rhs_code (stmt) == NEGATE_EXPR
+	       && can_reassociate_p (gimple_assign_rhs1 (stmt)))
+	VEC_safe_push (tree, heap, plus_negates, gimple_assign_lhs (stmt));
     }
   for (son = first_dom_son (CDI_DOMINATORS, bb);
        son;
@@ -1858,19 +1904,9 @@ reassociate_bb (basic_block bb)
 	  rhs1 = gimple_assign_rhs1 (stmt);
 	  rhs2 = gimple_assign_rhs2 (stmt);
 
-	  /* If associative-math we can do reassociation for
-	     non-integral types.  Or, we can do reassociation for
-	     non-saturating fixed-point types.  */
-	  if ((!INTEGRAL_TYPE_P (TREE_TYPE (lhs))
-	       || !INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
-	       || !INTEGRAL_TYPE_P (TREE_TYPE (rhs2)))
-	      && (!SCALAR_FLOAT_TYPE_P (TREE_TYPE (lhs))
-		  || !SCALAR_FLOAT_TYPE_P (TREE_TYPE(rhs1))
-		  || !SCALAR_FLOAT_TYPE_P (TREE_TYPE(rhs2))
-		  || !flag_associative_math)
-	      && (!NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE (lhs))
-		  || !NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE(rhs1))
-		  || !NON_SAT_FIXED_POINT_TYPE_P (TREE_TYPE(rhs2))))
+	  if (!can_reassociate_p (lhs)
+	      || !can_reassociate_p (rhs1)
+	      || !can_reassociate_p (rhs2))
 	    continue;
 
 	  if (associative_tree_code (rhs_code))