[Bug tree-optimization/37242] missed FRE opportunity because of signedness of addition

[bonzini at gnu dot org]

------- Comment #5 from bonzini at gnu dot org  2008-08-27 07:14 -------
With this patch:

Index: fold-const.c
===================================================================
--- fold-const.c        (revision 139423)
+++ fold-const.c        (working copy)
@@ -7868,7 +7868,11 @@ fold_unary (enum tree_code code, tree ty
         very likely don't have maximal range for their precision and this
         transformation effectively doesn't preserve non-maximal ranges.  */
       if (TREE_CODE (type) == INTEGER_TYPE
-         && TREE_CODE (op0) == BIT_AND_EXPR
+         && (TREE_CODE (op0) == BIT_AND_EXPR
+             || TREE_CODE (op0) == BIT_IOR_EXPR
+             || TREE_CODE (op0) == BIT_XOR_EXPR
+             || TREE_CODE (op0) == PLUS_EXPR
+             || TREE_CODE (op0) == MINUS_EXPR)
          && TREE_CODE (TREE_OPERAND (op0, 1)) == INTEGER_CST)
        {
          tree and = op0;
@@ -7906,7 +7910,7 @@ fold_unary (enum tree_code code, tree ty
              tem = force_fit_type_double (type, TREE_INT_CST_LOW (and1),
                                           TREE_INT_CST_HIGH (and1), 0,
                                           TREE_OVERFLOW (and1));
-             return fold_build2 (BIT_AND_EXPR, type,
+             return fold_build2 (TREE_CODE (op0), type,
                                  fold_convert (type, and0), tem);
            }
        }

I can fold "(unsigned) (x + 1)" to "(unsigned) x + 1". The problem is that TER
does not fold the trees it creates.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37242