http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50037
--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-08-11
12:12:56 UTC ---
The following patch makes us handle the canonical testcase on the tree level,
but not yet the original testcase (because of the * 2).
We should really preserve value-range information from VRP.
Index: gcc/tree-ssa-loop-niter.c
===================================================================
--- gcc/tree-ssa-loop-niter.c (revision 177649)
+++ gcc/tree-ssa-loop-niter.c (working copy)
@@ -126,6 +126,32 @@ determine_value_range (tree type, tree v
return;
}
+ /* Check if we can determine a value-range from VARs definition.
+ ??? We should simply preserve VRP information. */
+ if (TREE_CODE (var) == SSA_NAME)
+ {
+ gimple def_stmt = SSA_NAME_DEF_STMT (var);
+ if (is_gimple_assign (def_stmt)
+ && gimple_assign_rhs_code (def_stmt) == BIT_AND_EXPR)
+ {
+ tree rhs2 = gimple_assign_rhs2 (def_stmt);
+ if (TREE_CODE (rhs2) == INTEGER_CST
+ && tree_int_cst_sgn (rhs2) > 0)
+ {
+ double_int maxdi;
+ if (TREE_INT_CST_HIGH (rhs2) == 0)
+ maxdi = double_int_mask (HOST_BITS_PER_WIDE_INT
+ - clz_hwi (TREE_INT_CST_LOW (rhs2)));
+ else
+ maxdi = double_int_mask (HOST_BITS_PER_DOUBLE_INT
+ - clz_hwi (TREE_INT_CST_LOW (rhs2)));
+ mpz_set_si (min, 0);
+ mpz_set_double_int (max, maxdi, true);
+ return;
+ }
+ }
+ }
+
/* If the computation may wrap, we know nothing about the value, except for
the range of the type. */
get_type_static_bounds (type, min, max);
