re PR tree-optimization/14287 ([tree-ssa] does not remove unnecessary extensions)

2006-05-04  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/14287
	PR tree-optimization/14844
	PR tree-optimization/19792
	PR tree-optimization/21608
	PR tree-optimization/27090
	* tree-ssa-pre.c (try_combine_conversion): New function.
	(compute_avail): After constructing the value-handle
	expression, use try_combine_conversion to combine NOP_EXPRs
	with previous value-handle expressions and use the result if it
	is available.

	* gcc.dg/tree-ssa/ssa-fre-1.c: New testcase.
	* gcc.dg/tree-ssa/ssa-fre-2.c: Likewise.
	* gcc.dg/tree-ssa/ssa-fre-3.c: Likewise.
	* gcc.dg/tree-ssa/ssa-fre-4.c: Likewise.
	* gcc.dg/tree-ssa/ssa-fre-5.c: Likewise.

From-SVN: r113527

1 files changed, 49 insertions, 3 deletions

diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 38f020f..08f0930 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -3309,6 +3309,42 @@ realify_fake_stores (void)
     }
 }
 
+/* Tree-combine a value number expression *EXPR_P that does a type
+   conversion with the value number expression of its operand.
+   Returns true, if *EXPR_P simplifies to a value number or
+   gimple min-invariant expression different from EXPR_P and
+   sets *EXPR_P to the simplified expression value number.
+   Otherwise returns false and does not change *EXPR_P.  */
+
+static bool
+try_combine_conversion (tree *expr_p)
+{
+  tree expr = *expr_p;
+  tree t;
+
+  if (!((TREE_CODE (expr) == NOP_EXPR
+	 || TREE_CODE (expr) == CONVERT_EXPR)
+	&& TREE_CODE (TREE_OPERAND (expr, 0)) == VALUE_HANDLE
+	&& !VALUE_HANDLE_VUSES (TREE_OPERAND (expr, 0))))
+    return false;
+
+  t = fold_unary (TREE_CODE (expr), TREE_TYPE (expr),
+		  VALUE_HANDLE_EXPR_SET (TREE_OPERAND (expr, 0))->head->expr);
+
+  /* Disallow value expressions we have no value number for already, as
+     we would miss a leader for it here.  */
+  if (t
+      && !(TREE_CODE (t) == VALUE_HANDLE
+	   || is_gimple_min_invariant (t)))
+    t = vn_lookup (t, NULL);
+
+  if (t && t != expr)
+    {
+      *expr_p = t;
+      return true;
+    }
+  return false;
+}
 
 /* Compute the AVAIL set for all basic blocks.
 
@@ -3433,9 +3469,19 @@ compute_avail (void)
 		  tree newt = create_value_expr_from (rhs, block, stmt);
 		  if (newt)
 		    {
-		      add_to_sets (lhs, newt, stmt, TMP_GEN (block),
-				   AVAIL_OUT (block));
-		      value_insert_into_set (EXP_GEN (block), newt);
+		      /* If we can combine a conversion expression
+			 with the expression for its operand just
+			 record the value number for it.  */
+		      if (try_combine_conversion (&newt))
+			vn_add (lhs, newt);
+		      else
+			{
+			  tree val = vn_lookup_or_add (newt, stmt);
+			  vn_add (lhs, val);
+			  value_insert_into_set (EXP_GEN (block), newt);
+			}
+		      bitmap_insert_into_set (TMP_GEN (block), lhs);
+		      bitmap_value_insert_into_set (AVAIL_OUT (block), lhs);
 		      continue;
 		    }
 		}