Le 26/10/2023 à 11:29, Richard Biener a écrit :
On Wed, Oct 25, 2023 at 5:51 AM Andrew Pinski <pins...@gmail.com> wrote:
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 40767736389..2a2a90230f5 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -15047,15 +15047,33 @@ tree_single_nonnegative_warnv_p (tree t, bool
*strict_overflow_p, int depth)
return RECURSE (TREE_OPERAND (t, 1)) && RECURSE (TREE_OPERAND (t, 2));
case SSA_NAME:
- /* Limit the depth of recursion to avoid quadratic behavior.
- This is expected to catch almost all occurrences in practice.
- If this code misses important cases that unbounded recursion
- would not, passes that need this information could be revised
- to provide it through dataflow propagation. */
- return (!name_registered_for_update_p (t)
- && depth < param_max_ssa_name_query_depth
- && gimple_stmt_nonnegative_warnv_p (SSA_NAME_DEF_STMT (t),
- strict_overflow_p, depth));
+ {
+ /* For integral types, querry the global range if possible. */
query
+ if (INTEGRAL_TYPE_P (TREE_TYPE (t)))
+ {
+ value_range vr;
+ if (get_global_range_query ()->range_of_expr (vr, t)
+ && !vr.varying_p () && !vr.undefined_p ())
+ {
+ /* If the range is nonnegative, return true. */
+ if (vr.nonnegative_p ())
+ return true;
+
+ /* If the range is non-positive, then return false. */
+ if (vr.nonpositive_p ())
+ return false;
That's testing for <= 0, nonnegative for >= 0. This means when
vr.nonpositive_p () the value could still be zero (and nonnegative),
possibly be figured out by the recursion below.
Since we don't have negative_p () do we want to test
nonpositive_p () && nonzero_p () instead?
Maybe !contains_zero_p () instead of nonzero_p () ?
nonzero_p seems to check that the range is exactly the "all but zero"
range as visible in the implementation:
inline bool
irange::nonzero_p () const
{
if (undefined_p ())
return false;
wide_int zero = wi::zero (TYPE_PRECISION (type ()));
return *this == int_range<2> (type (), zero, zero, VR_ANTI_RANGE);
}
