re PR middle-end/38140 (ice for C code with -O2)

	PR middle-end/38140
	* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): If
	propagating x = &a into *x = b, add a cast if not useless
	type conversion or don't optimize if another stmt would be
	needed.

	* gcc.dg/pr38140.c: New test.

From-SVN: r141949

gcc/ChangeLog

+2008-11-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/38140
+	* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): If
+	propagating x = &a into *x = b, add a cast if not useless
+	type conversion or don't optimize if another stmt would be
+	needed.
+
 2008-11-17  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR middle-end/37908

gcc/testsuite/ChangeLog

+2008-11-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/38140
+	* gcc.dg/pr38140.c: New test.
+
 2008-11-17  Jack Howarth  <howarth@bromo.med.uc.edu>
         
         PR testsuite/38099

gcc/testsuite/gcc.dg/pr38140.c

+/* PR middle-end/38140 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-strict-aliasing" } */
+
+int foo (void *x)
+{
+  int (*fn) (int);
+  *(void **)&fn = x;
+  return fn (6);
+}

gcc/tree-ssa-forwprop.c

@@ -721,13 +721,28 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs,
       && TREE_OPERAND (lhs, 0) == name
       && may_propagate_address_into_dereference (def_rhs, lhs))
     {
-      *lhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
-      fold_stmt_inplace (use_stmt);
-      tidy_after_forward_propagate_addr (use_stmt);
+      bool valid = true;
+      if (lhsp == gimple_assign_lhs_ptr (use_stmt)
+	  && !useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
+					 TREE_TYPE (rhs))
+	  && !CONVERT_EXPR_CODE_P (rhs_code))
+	{
+	  if (rhs_code == SSA_NAME)
+	    gimple_assign_set_rhs_code (use_stmt, NOP_EXPR);
+	  else
+	    valid = false;
+	}
+      if (valid)
+	{
+	  *lhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
+	  fold_stmt_inplace (use_stmt);
+	  tidy_after_forward_propagate_addr (use_stmt);
 
-      /* Continue propagating into the RHS if this was not the only use.  */
-      if (single_use_p)
-	return true;
+	  /* Continue propagating into the RHS if this was not the only
+	     use.  */
+	  if (single_use_p)
+	    return true;
+	}
     }
 
   /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR