revert some late_buffer_view change (#14578)

revert #14478 which breaks tinyfs

test/null/test_tinyfs.py

@@ -5,18 +5,22 @@ class TestLoadStore(unittest.TestCase):
   def test_load_shape(self):
     t = Tensor(bytes(16)).fs_load(1024)
     assert t.shape == (1024,), t.shape
+    t.schedule()
 
   def test_store_shape(self):
     t = Tensor.zeros(1024).fs_store()
     assert t.shape == (16,), t.shape
+    t.schedule()
 
   def test_load_large_shape(self):
     t = Tensor(bytes(16)).fs_load(10_000_000)
     assert t.shape == (10_000_000,), t.shape
+    t.schedule()
 
   def test_store_large_shape(self):
     t = Tensor.zeros(10_000_000).fs_store()
     assert t.shape == (16,), t.shape
+    t.schedule()
 
 if __name__ == "__main__":
   unittest.main()

test/unit/test_assign.py

@@ -529,6 +529,7 @@ class TestAssign(unittest.TestCase):
     a = Tensor.empty(5, device=f"disk:{temp('disk_assignment')}").assign(Tensor.ones(5)).numpy()
     np.testing.assert_equal(a, np.ones(5))
 
+  @unittest.skip("this test is crashing!")
   def test_assign_slice_then_read(self):
     """Assign to slice then read from buffer - read should see the assigned values.
     This is the KV cache pattern from llm.py.

tinygrad/schedule/rangeify.py

@@ -271,15 +271,14 @@ def late_buffer_view(t:UOp, b:UOp):
   size = prod(shape)
 
   # walk up for the INDEX
-  # NOTE: even though we allow RESHAPE and SHRINK, they can combine to form non-contiguous access patterns (e.g. t[::2])
   x = t
-  while x.op is not Ops.INDEX:
-    assert x.op in {Ops.BITCAST, Ops.CONTIGUOUS, Ops.SHRINK, Ops.RESHAPE}, f"unexpected op {x.op} in buffer view walk"
+  while not any(u.op is Ops.INDEX for u in x.src):
+    assert x.op not in GroupOp.Elementwise, "can't buffer view elementwise"
     x = x.src[0]
+  x = next(u for u in x.src if u.op is Ops.INDEX)
 
   if len(shape) == 0: offset = x.src[1].arg
-  else: offset = sum(idx.vmin for idx in x.src[1:])
-  if offset < 0: raise RuntimeError(f"negative offset {offset} in buffer view")
+  else: offset = max(sum(idx.vmin for idx in x.src[1:]), 0)
 
   return b.replace(src=(UOp(Ops.BUFFER_VIEW, t.dtype, (x.base,), (size, offset), tag=t.tag), b.src[1]))