2008-03-18 Richard Guenther <rguenther@suse.de>

	* tree-ssa-sccvn.c (visit_reference_op_load): If the lookup
	found an expression with constants, note that in the VN for the lhs.
	* tree-ssa-pre.c (eliminate): Visit COND_EXPR statements and
	fold them to constants if possible.  Run cleanup_cfg if done so.
	(execute_pre): Return todo.
	(do_pre): Likewise.
	(execute_fre): Likewise.
	* tree-ssa-forwprop.c (can_propagate_from): Allow propagation
	of constants.
	(get_prop_source_stmt): Look through pointer conversions.

	* gcc.dg/tree-ssa/forwprop-4.c: New testcase.
	* gcc.dg/tree-ssa/ssa-fre-16.c: Likewise.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@133315 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 22 insertions, 4 deletions

diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c
index 5108cfcd6f2..1766869d0c4 100644
--- a/gcc/tree-ssa-forwprop.c
+++ b/gcc/tree-ssa-forwprop.c
@@ -218,14 +218,28 @@ get_prop_source_stmt (tree name, bool single_use_only, bool *single_use_p)
     /* If name is not a simple copy destination, we found it.  */
     if (TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) != SSA_NAME)
       {
+	tree rhs;
+
 	if (!single_use_only && single_use_p)
 	  *single_use_p = single_use;
 
-	return def_stmt;
+	/* We can look through pointer conversions in the search
+	   for a useful stmt for the comparison folding.  */
+	rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
+	if ((TREE_CODE (rhs) == NOP_EXPR
+	     || TREE_CODE (rhs) == CONVERT_EXPR)
+	    && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
+	    && POINTER_TYPE_P (TREE_TYPE (rhs))
+	    && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0))))
+	  name = TREE_OPERAND (rhs, 0);
+	else
+	  return def_stmt;
+      }
+    else
+      {
+	/* Continue searching the def of the copy source name.  */
+	name = GIMPLE_STMT_OPERAND (def_stmt, 1);
       }
-
-    /* Continue searching the def of the copy source name.  */
-    name = GIMPLE_STMT_OPERAND (def_stmt, 1);
   } while (1);
 }
 
@@ -245,6 +259,10 @@ can_propagate_from (tree def_stmt)
   if (REFERENCE_CLASS_P (rhs))
     return false;
 
+  /* Constants can be always propagated.  */
+  if (is_gimple_min_invariant (rhs))
+    return true;
+
   /* We cannot propagate ssa names that occur in abnormal phi nodes.  */
   switch (TREE_CODE_LENGTH (TREE_CODE (rhs)))
     {