#675: Fix OOB negative slice bug (#676)

Fixes #675

Author: akhilg-nv

tripy/nvtripy/frontend/ops/slice.py

@@ -208,11 +208,19 @@ def get_min(a, b):
                     else minimum(cast_to_dim_size(a), cast_to_dim_size(b))
                 )
 
+            def get_max(a, b):
+                return (
+                    max(a, b)
+                    if isinstance(a, int) and isinstance(b, int)
+                    else maximum(cast_to_dim_size(a), cast_to_dim_size(b))
+                )
+
             if slice_idx.start is not None:
                 start = to_positive_idx(slice_idx.start)
                 # If `start` is past the end, clamp it - if we're going backwards, we need to clamp it to a valid value;
                 # otherwise, we can clamp it out of bounds (which will yield an empty tensor):
                 start = get_min(start, select(step >= 0, dim_size, dim_size - 1))
+                start = get_max(start, 0)  # if the adjusted start is still negative, clamp it to 0
             else:
                 start = default_start
 

tripy/tests/integration/test_slice.py

@@ -69,6 +69,7 @@ class TestSliceOp:
             ((2, 3, 4), lambda t: t[None]),
             ((2, 3, 4), lambda t: t[None, 1:2, :, None]),
             ((2, 3, 4), lambda t: t[..., None, 0, None]),
+            ((1, 2), lambda t: t[:, -4:]),  # negative start greater than dimension size
         ],
     )
     def test_slice(self, use_constant, shape, slice_func, eager_or_compiled):