re PR tree-optimization/19637 (Missed VRP and FRE opportunities in the presence of casts)

2008-03-17  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/19637
	* fold-const.c (fold_unary): Remove restrictions of removing
	intermediate pointer-conversions (P2)(P1)P0.
	* tree-ssa-ccp.c (maybe_fold_stmt_addition): Recover from
	conversion to void pointer.
	(get_maxval_strlen): Handle addresses of the form &(*p)[0].

	* g++.dg/tree-ssa/pr19637.C: New testcase.

From-SVN: r133291

gcc/ChangeLog

+2008-03-17  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/19637
+	* fold-const.c (fold_unary): Remove restrictions of removing
+	intermediate pointer-conversions (P2)(P1)P0.
+	* tree-ssa-ccp.c (maybe_fold_stmt_addition): Recover from
+	conversion to void pointer.
+	(get_maxval_strlen): Handle addresses of the form &(*p)[0].
+
 2008-03-16  James E. Wilson  <wilson@tuliptree.org>
 
 	PR debug/31510

gcc/fold-const.c

@@ -7784,9 +7784,7 @@ fold_unary (enum tree_code code, tree type, tree op0)
 	     - the initial type is a pointer type and the precisions of the
 	       intermediate and final types differ, or
 	     - the final type is a pointer type and the precisions of the
-	       initial and intermediate types differ.
-	     - the initial type is a pointer to an array and the final type
-	       not.  */
+	       initial and intermediate types differ.  */
 	  if (! inside_float && ! inter_float && ! final_float
 	      && ! inside_vec && ! inter_vec && ! final_vec
 	      && (inter_prec >= inside_prec || inter_prec >= final_prec)
@@ -7798,10 +7796,7 @@ fold_unary (enum tree_code code, tree type, tree op0)
 	      && ! (inside_ptr && inter_prec != final_prec)
 	      && ! (final_ptr && inside_prec != inter_prec)
 	      && ! (final_prec != GET_MODE_BITSIZE (TYPE_MODE (type))
-		    && TYPE_MODE (type) == TYPE_MODE (inter_type))
-	      && ! (inside_ptr && final_ptr
-		    && TREE_CODE (TREE_TYPE (inside_type)) == ARRAY_TYPE
-		    && TREE_CODE (TREE_TYPE (type)) != ARRAY_TYPE))
+		    && TYPE_MODE (type) == TYPE_MODE (inter_type)))
 	    return fold_build1 (code, type, TREE_OPERAND (op0, 0));
 	}
 

gcc/testsuite/ChangeLog

+2008-03-17  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/19637
+	* g++.dg/tree-ssa/pr19637.C: New testcase.
+
 2008-03-16  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/35470

gcc/testsuite/g++.dg/tree-ssa/pr19637.C

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-dom1" } */
+
+#include <new>
+
+struct Foo {
+  Foo() { i[0] = 1; }
+  int i[2];
+};
+
+int foo_char(void)
+{
+  int i[2];
+  new (reinterpret_cast<char *>(i)) Foo();
+  return reinterpret_cast<Foo *>(i)->i[0];
+}
+
+int foo_void(void)
+{
+  int i[2];
+  new (reinterpret_cast<void *>(i)) Foo();
+  return reinterpret_cast<Foo *>(i)->i[0];
+}
+
+int foo_void_offset(void)
+{
+  int i[2];
+  new (reinterpret_cast<void *>(&i[0])) Foo();
+  return reinterpret_cast<Foo *>(&i[0])->i[0];
+}
+
+/* { dg-final { scan-tree-dump-times "return 1;" 3 "dom1" } } */
+/* { dg-final { cleanup-tree-dump "dom1" } } */

gcc/tree-ssa-ccp.c

@@ -2105,6 +2105,12 @@ maybe_fold_stmt_addition (tree expr)
     }
 
   ptd_type = TREE_TYPE (ptr_type);
+  /* If we want a pointer to void, reconstruct the reference from the
+     array element type.  A pointer to that can be trivially converted
+     to void *.  This happens as we fold (void *)(ptr p+ off).  */
+  if (VOID_TYPE_P (ptd_type)
+      && TREE_CODE (TREE_TYPE (op0)) == ARRAY_TYPE)
+    ptd_type = TREE_TYPE (TREE_TYPE (op0));
 
   /* At which point we can try some of the same things as for indirects.  */
   t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type, true);
@@ -2292,6 +2298,17 @@ get_maxval_strlen (tree arg, tree *length, bitmap visited, int type)
       if (TREE_CODE (arg) == COND_EXPR)
         return get_maxval_strlen (COND_EXPR_THEN (arg), length, visited, type)
                && get_maxval_strlen (COND_EXPR_ELSE (arg), length, visited, type);
+      /* We can end up with &(*iftmp_1)[0] here as well, so handle it.  */
+      else if (TREE_CODE (arg) == ADDR_EXPR
+	       && TREE_CODE (TREE_OPERAND (arg, 0)) == ARRAY_REF
+	       && integer_zerop (TREE_OPERAND (TREE_OPERAND (arg, 0), 1)))
+	{
+	  tree aop0 = TREE_OPERAND (TREE_OPERAND (arg, 0), 0);
+	  if (TREE_CODE (aop0) == INDIRECT_REF
+	      && TREE_CODE (TREE_OPERAND (aop0, 0)) == SSA_NAME)
+	    return get_maxval_strlen (TREE_OPERAND (aop0, 0),
+				      length, visited, type);
+	}
 
       if (type == 2)
 	{