Fix a couple of slicing bugs (#1827)

* fix a few bugs

* fix conv grad

* speedup test

* comment

python/tests/test_conv.py

@@ -911,6 +911,44 @@ class TestConv(mlx_tests.MLXTestCase):
             expected = mx.array([[dw00, dw01], [dw10, dw11]])
             self.assertTrue(mx.allclose(dw, expected, rtol=1e-5, atol=1e-5))
 
+        # Test with input dilation
+        inputs = mx.random.normal((1, 14, 14, 2))
+        kernel = mx.random.normal((2, 7, 7, 2))
+
+        def conv_flip(kernel):
+            return mx.conv_general(
+                inputs,
+                kernel,
+                stride=1,
+                padding=([6, 6], [15, 15]),
+                kernel_dilation=(1, 1),
+                input_dilation=(16, 16),
+                groups=1,
+                flip=True,
+            ).sum()
+
+        def reverse_sequence(xs, axis=0):
+            indices = mx.arange(xs.shape[axis] - 1, -1, -1)
+            return mx.take(xs, indices, axis=axis)
+
+        def conv_manual_flip(kernel):
+            for ax in range(1, kernel.ndim - 1):
+                kernel = reverse_sequence(kernel, axis=ax)
+            return mx.conv_general(
+                inputs,
+                kernel,
+                stride=1,
+                padding=([6, 6], [15, 15]),
+                kernel_dilation=(1, 1),
+                input_dilation=(16, 16),
+                groups=1,
+                flip=False,
+            ).sum()
+
+        grad = mx.grad(conv_flip)(kernel)
+        expected_grad = mx.grad(conv_manual_flip)(kernel)
+        self.assertTrue(mx.allclose(grad, expected_grad))
+
     def test_conv_groups_grad(self):
         def fn(x, w):
             num_groups = x.shape[-1] // w.shape[-1]