When optimizing signed right-shift loops into CLZ operations, the initial
value is checked for non-negativity using Ranger on the loop preheader
edge. However, `range_on_edge` returning true only indicates that the
range query is supported; it does not guarantee that the resulting range
is defined.
Check `undefined_p ()` before applying the non-negativity test in both
`number_of_iterations_cltz` and `number_of_iterations_cltz_complement`.
This prevents an undefined range from being incorrectly treated as a
valid non-negative range.
Regression tested on x86_64-pc-linux-gnu.
gcc/ChangeLog:
* tree-ssa-loop-niter.cc (number_of_iterations_cltz): Reject
undefined ranges returned by Ranger.
(number_of_iterations_cltz_complement): Likewise.
Signed-off-by: Shivam Gupta <[email protected]>
---
gcc/tree-ssa-loop-niter.cc | 2 ++
1 file changed, 2 insertions(+)
diff --git a/gcc/tree-ssa-loop-niter.cc b/gcc/tree-ssa-loop-niter.cc
index dd10e3849..bbfa16c6d 100644
--- a/gcc/tree-ssa-loop-niter.cc
+++ b/gcc/tree-ssa-loop-niter.cc
@@ -2488,6 +2488,7 @@ number_of_iterations_cltz (loop_p loop, edge exit,
int_range_max r (TREE_TYPE (src));
edge e = loop_preheader_edge (loop);
if (!get_range_query (cfun)->range_on_edge (r, e, src)
+ || r.undefined_p ()
|| !r.nonnegative_p ())
return false;
}
@@ -2659,6 +2660,7 @@ number_of_iterations_cltz_complement (loop_p loop, edge
exit,
int_range_max r (TREE_TYPE (src));
edge e = loop_preheader_edge (loop);
if (!get_range_query (cfun)->range_on_edge (r, e, src)
+ || r.undefined_p ()
|| !r.nonnegative_p ())
return false;
}
--
2.43.0
