re PR middle-end/40815 (redundant neg instruction caused by loop-invariant)

	PR middle-end/40815
	* tree-ssa-reassoc.c (broken_up_substracts): Rename to plus_negates.
	(negate_value): Move code to push elements to broken_up_substracts ...
	(eliminate_plus_minus_pair): ... here.  Push operands that have no
	negative pair to plus_negates.
	(repropagate_negates, init_reassoc, fini_reassoc): Update.

	PR middle-end/40815
	* gcc.dg/tree-ssa/reassoc-19.c: New.

From-SVN: r158105

gcc/ChangeLog

+2010-04-08  Maxim Kuvyrkov  <maxim@codesourcery.com>
+
+	PR middle-end/40815
+	* tree-ssa-reassoc.c (broken_up_substracts): Rename to plus_negates.
+	(negate_value): Move code to push elements to broken_up_substracts ...
+	(eliminate_plus_minus_pair): ... here.  Push operands that have no
+	negative pair to plus_negates.
+	(repropagate_negates, init_reassoc, fini_reassoc): Update.
+
 2010-04-07  Ralf Wildenhues  <Ralf.Wildenhues@gmx.de>
 
 	* doc/install.texi (Configuration): Move description of

gcc/testsuite/ChangeLog

+2010-04-08  Maxim Kuvyrkov  <maxim@codesourcery.com>
+
+	PR middle-end/40815
+	* gcc.dg/tree-ssa/reassoc-19.c: New.
+
 2010-04-07  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/18624

gcc/testsuite/gcc.dg/tree-ssa/reassoc-19.c

+/* { dg-do compile } */
+/* { dg-options "-Os -fdump-tree-reassoc2" } */
+
+/* Slightly changed testcase from PR middle-end/40815.  */
+void bar(char*, char*, int);
+void foo(char* left, char* rite, int element)
+{
+  while (left <= rite)
+  {
+    /* This should expand into
+       D.zzzz = D.zzzz - D.xxxx;
+       and NOT to
+       D.D.yyyy = -D.xxxx; D.zzzz = D.zzzz + D.yyyy;  */
+    rite -= element;
+    bar(left, rite, element);
+  }
+}
+
+/* There should be no " + " in the dump.  */
+/* { dg-final { scan-tree-dump-times " \\\+ " 0 "reassoc2" } } */
+/* { dg-final { cleanup-tree-dump "reassoc2" } } */

gcc/tree-ssa-reassoc.c

@@ -467,6 +467,8 @@ eliminate_duplicate_pair (enum tree_code opcode,
   return false;
 }
 
+static VEC(tree, heap) *plus_negates;
+
 /* If OPCODE is PLUS_EXPR, CURR->OP is really a negate expression,
    look in OPS for a corresponding positive operation to cancel it
    out.  If we find one, remove the other from OPS, replace
@@ -521,6 +523,10 @@ eliminate_plus_minus_pair (enum tree_code opcode,
 	}
     }
 
+  /* CURR->OP is a negate expr in a plus expr: save it for later
+     inspection in repropagate_negates().  */
+  VEC_safe_push (tree, heap, plus_negates, curr->op);
+
   return false;
 }
 
@@ -1500,8 +1506,6 @@ get_single_immediate_use (tree lhs)
   return NULL;
 }
 
-static VEC(tree, heap) *broken_up_subtracts;
-
 /* Recursively negate the value of TONEGATE, and return the SSA_NAME
    representing the negated value.  Insertions of any necessary
    instructions go before GSI.
@@ -1544,7 +1548,6 @@ negate_value (tree tonegate, gimple_stmt_iterator *gsi)
   tonegate = fold_build1 (NEGATE_EXPR, TREE_TYPE (tonegate), tonegate);
   resultofnegate = force_gimple_operand_gsi (gsi, tonegate, true,
 					     NULL_TREE, true, GSI_SAME_STMT);
-  VEC_safe_push (tree, heap, broken_up_subtracts, resultofnegate);
   return resultofnegate;
 }
 
@@ -1700,7 +1703,7 @@ repropagate_negates (void)
   unsigned int i = 0;
   tree negate;
 
-  for (i = 0; VEC_iterate (tree, broken_up_subtracts, i, negate); i++)
+  for (i = 0; VEC_iterate (tree, plus_negates, i, negate); i++)
     {
       gimple user = get_single_immediate_use (negate);
 
@@ -2014,7 +2017,7 @@ init_reassoc (void)
 
   free (bbs);
   calculate_dominance_info (CDI_POST_DOMINATORS);
-  broken_up_subtracts = NULL;
+  plus_negates = NULL;
 }
 
 /* Cleanup after the reassociation pass, and print stats if
@@ -2035,7 +2038,7 @@ fini_reassoc (void)
   pointer_map_destroy (operand_rank);
   free_alloc_pool (operand_entry_pool);
   free (bb_rank);
-  VEC_free (tree, heap, broken_up_subtracts);
+  VEC_free (tree, heap, plus_negates);
   free_dominance_info (CDI_POST_DOMINATORS);
   loop_optimizer_finalize ();
 }