re PR middle-end/28685 (Multiple comparisons are not simplified)

2010-05-08  Sandra Loosemore  <sandra@codesourcery.com>

	PR middle-end/28685

	gcc/
	* tree-ssa-reassoc.c (eliminate_redundant_comparison): New function.
	(optimize_ops_list): Call it.

	gcc/testsuite/
	* gcc.dg/pr28685-1.c: New file.

From-SVN: r159189

4 files changed, 170 insertions, 1 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index cb1661c..28fd31f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2010-05-08  Sandra Loosemore  <sandra@codesourcery.com>
+
+	PR middle-end/28685
+	* tree-ssa-reassoc.c (eliminate_redundant_comparison): New function.
+	(optimize_ops_list): Call it.
+
 2010-05-08  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/44030
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 66630e8..38501a7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2010-05-08  Sandra Loosemore  <sandra@codesourcery.com>
+
+	PR middle-end/28685
+	* gcc.dg/pr28685-1.c: New file.
+
 2010-05-08  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/44030
diff --git a/gcc/testsuite/gcc.dg/pr28685-1.c b/gcc/testsuite/gcc.dg/pr28685-1.c
new file mode 100644
index 0000000..1d9d97e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr28685-1.c
@@ -0,0 +1,50 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" }  */
+
+/* Should produce <=.  */
+int test1 (int a, int b)
+{
+  return (a < b || a == b);
+}
+
+/* Should produce <=.  */
+int test2 (int a, int b)
+{
+  int lt = a < b;
+  int eq = a == b;
+
+  return (lt || eq);
+}
+
+/* Should produce <= (just deleting redundant test).  */
+int test3 (int a, int b)
+{
+  int lt = a <= b;
+  int eq = a == b;
+
+  return (lt || eq);
+}
+
+/* Should produce <= (operands reversed to test the swap logic).  */
+int test4 (int a, int b)
+{
+  int lt = a < b;
+  int eq = b == a;
+
+  return (lt || eq);
+}
+
+/* Should produce constant 0.  */
+int test5 (int a, int b)
+{
+  int lt = a < b;
+  int eq = a == b;
+
+  return (lt && eq);
+}
+
+/* { dg-final { scan-tree-dump-times " <= " 4 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-not " < " "optimized" } } */
+/* { dg-final { scan-tree-dump-not " == " "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
diff --git a/gcc/tree-ssa-reassoc.c b/gcc/tree-ssa-reassoc.c
index aa08085..6bdb57e 100644
--- a/gcc/tree-ssa-reassoc.c
+++ b/gcc/tree-ssa-reassoc.c
@@ -1215,6 +1215,113 @@ undistribute_ops_list (enum tree_code opcode,
   return changed;
 }
 
+/* If OPCODE is BIT_IOR_EXPR or BIT_AND_EXPR and CURR is a comparison
+   expression, examine the other OPS to see if any of them are comparisons
+   of the same values, which we may be able to combine or eliminate.
+   For example, we can rewrite (a < b) | (a == b) as (a <= b).  */
+
+static bool
+eliminate_redundant_comparison (enum tree_code opcode,
+				VEC (operand_entry_t, heap) **ops,
+				unsigned int currindex,
+				operand_entry_t curr)
+{
+  tree op1, op2;
+  enum tree_code lcode, rcode;
+  gimple def1, def2;
+  int i;
+  operand_entry_t oe;
+
+  if (opcode != BIT_IOR_EXPR && opcode != BIT_AND_EXPR)
+    return false;
+
+  /* Check that CURR is a comparison.  */
+  if (TREE_CODE (curr->op) != SSA_NAME)
+    return false;
+  def1 = SSA_NAME_DEF_STMT (curr->op);
+  if (!is_gimple_assign (def1))
+    return false;
+  lcode = gimple_assign_rhs_code (def1);
+  if (TREE_CODE_CLASS (lcode) != tcc_comparison)
+    return false;
+  op1 = gimple_assign_rhs1 (def1);
+  op2 = gimple_assign_rhs2 (def1);
+
+  /* Now look for a similar comparison in the remaining OPS.  */
+  for (i = currindex + 1;
+       VEC_iterate (operand_entry_t, *ops, i, oe);
+       i++)
+    {
+      tree t;
+
+      if (TREE_CODE (oe->op) != SSA_NAME)
+	continue;
+      def2 = SSA_NAME_DEF_STMT (oe->op);
+      if (!is_gimple_assign (def2))
+	continue;
+      rcode = gimple_assign_rhs_code (def2);
+      if (TREE_CODE_CLASS (rcode) != tcc_comparison)
+	continue;
+      if (operand_equal_p (op1, gimple_assign_rhs1 (def2), 0)
+	  && operand_equal_p (op2, gimple_assign_rhs2 (def2), 0))
+	;
+      else if (operand_equal_p (op1, gimple_assign_rhs2 (def2), 0)
+	       && operand_equal_p (op2, gimple_assign_rhs1 (def2), 0))
+	rcode = swap_tree_comparison (rcode);
+      else
+	continue;
+
+      /* If we got here, we have a match.  See if we can combine the
+	 two comparisons.  */
+      t = combine_comparisons (UNKNOWN_LOCATION,
+			       (opcode == BIT_IOR_EXPR
+				? TRUTH_OR_EXPR : TRUTH_AND_EXPR),
+			       lcode, rcode, TREE_TYPE (curr->op), op1, op2);
+      if (!t)
+	continue;
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, "Equivalence: ");
+	  print_generic_expr (dump_file, curr->op, 0);
+	  fprintf (dump_file, " %s ", op_symbol_code (opcode));
+	  print_generic_expr (dump_file, oe->op, 0);
+	  fprintf (dump_file, " -> ");
+	  print_generic_expr (dump_file, t, 0);
+	  fprintf (dump_file, "\n");
+	}
+
+      /* Now we can delete oe, as it has been subsumed by the new combined
+         expression t.  */
+      VEC_ordered_remove (operand_entry_t, *ops, i);
+      reassociate_stats.ops_eliminated ++;
+
+      /* If t is the same as curr->op, we're done.  Otherwise we must
+	 replace curr->op with t.  Special case is if we got a constant
+	 back, in which case we add it to the end instead of in place of
+	 the current entry.  */
+      if (TREE_CODE (t) == INTEGER_CST)
+	{
+	  VEC_ordered_remove (operand_entry_t, *ops, currindex);
+	  add_to_ops_vec (ops, t);
+	}
+      else if (TREE_CODE (t) != lcode)
+	{
+	  tree tmpvar;
+	  gimple sum;
+	  enum tree_code subcode;
+	  tree newop1;
+	  tree newop2;
+	  tmpvar = create_tmp_var (TREE_TYPE (t), NULL);
+	  add_referenced_var (tmpvar);
+	  extract_ops_from_tree (t, &subcode, &newop1, &newop2);
+	  sum = build_and_add_sum (tmpvar, newop1, newop2, subcode);
+	  curr->op = gimple_get_lhs (sum);
+	}
+      return true;
+    }
+
+  return false;
+}
 
 /* Perform various identities and other optimizations on the list of
    operand entries, stored in OPS.  The tree code for the binary
@@ -1276,7 +1383,8 @@ optimize_ops_list (enum tree_code opcode,
       if (eliminate_not_pairs (opcode, ops, i, oe))
 	return;
       if (eliminate_duplicate_pair (opcode, ops, &done, i, oe, oelast)
-	  || (!done && eliminate_plus_minus_pair (opcode, ops, i, oe)))
+	  || (!done && eliminate_plus_minus_pair (opcode, ops, i, oe))
+	  || (!done && eliminate_redundant_comparison (opcode, ops, i, oe)))
 	{
 	  if (done)
 	    return;