From 46297dccaf9db98370fb48bee43942374b4f7b45 Mon Sep 17 00:00:00 2001
From: Jake VanderPlas <jakevdp@google.com>
Date: Tue, 4 Apr 2023 08:16:59 -0700
Subject: [PATCH] checkify: catch OOB errors in dynamic_slice

This will allow checkify tests to continue working properly after #15377
---
 jax/_src/checkify.py   | 16 ++++++++++++++++
 tests/checkify_test.py | 17 +++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/jax/_src/checkify.py b/jax/_src/checkify.py
index 369de3845e7e..23267f6ce372 100644
--- a/jax/_src/checkify.py
+++ b/jax/_src/checkify.py
@@ -587,6 +587,22 @@ def isnan(x):
   error_checks[_prim] = functools.partial(nan_error_check, _prim)
 
 
+def dynamic_slice_error_check(error, enabled_errors, operand, *start_indices, slice_sizes):
+  out = lax.dynamic_slice_p.bind(operand, *start_indices, slice_sizes=slice_sizes)
+
+  if OOBError not in enabled_errors:
+    return error, out
+
+  operand_dims = np.array(operand.shape)
+  slice_sizes = np.array(slice_sizes)
+  start_indices = jnp.array(start_indices)
+  oob_mask = (start_indices < 0) | (start_indices + slice_sizes > operand_dims)
+
+  payload = oob_payload(oob_mask, start_indices, range(operand.ndim), operand.shape)
+  error = assert_func(error, jnp.any(oob_mask), OOBError(summary(), "dynamic_slice", operand.shape, payload))
+  return error, out
+error_checks[lax.dynamic_slice_p] = dynamic_slice_error_check
+
 def gather_error_check(error, enabled_errors, operand, start_indices, *,
                        dimension_numbers, slice_sizes, unique_indices,
                        indices_are_sorted, mode, fill_value):
diff --git a/tests/checkify_test.py b/tests/checkify_test.py
index 8600270b41a3..57765268923d 100644
--- a/tests/checkify_test.py
+++ b/tests/checkify_test.py
@@ -181,6 +181,23 @@ def raises_oob(fn, idx, *expected_strs):
     raises_oob(multi_idx, (5, -9), "index 5", axis0_msg)
     raises_oob(multi_idx, ((0, 9), 0), "index 9", axis0_msg)
 
+  def test_dynamic_slice_oobs(self):
+    def raises_oob(fn, x, idx, *expected_strs):
+      err, _ = checkify.checkify(jax.jit(fn), errors=checkify.index_checks)(x, idx)
+      error_txt = err.get()
+      self.assertIsNotNone(error_txt)
+      self.assertStartsWith(error_txt, "out-of-bounds indexing")
+      for s in expected_strs:
+        self.assertIn(s, error_txt)
+
+    x = jnp.ones((2, 3, 7))
+    raises_oob(partial(lax.dynamic_slice, slice_sizes=(1, 1, 1)), x, (2, 0, 0), 'index 2')
+    raises_oob(partial(lax.dynamic_slice, slice_sizes=(1, 1, 1)), x, (-3, 0, 0), 'index -1')
+    raises_oob(partial(lax.dynamic_slice, slice_sizes=(1, 1, 1)), x, (0, 3, 0), 'index 3')
+    raises_oob(partial(lax.dynamic_slice, slice_sizes=(1, 1, 1)), x, (0, -5, 0), 'index -2')
+    raises_oob(partial(lax.dynamic_slice, slice_sizes=(1, 1, 1)), x, (0, 1, 8), 'index 8')
+    raises_oob(partial(lax.dynamic_slice, slice_sizes=(1, 1, 1)), x, (0, 1, -10), 'index -3')
+
   @jtu.sample_product(jit=[False, True])
   def test_jit_ordering(self, jit):
     def f(x, i):