Fix tensor value assignment and partial indexing in Helion

helion/_compiler/indexing_strategy.py

@@ -26,6 +26,7 @@
     from ..runtime.config import Config
     from .device_function import TensorDescriptorArg
     from .inductor_lowering import CodegenState
+    from .tile_dispatch import TileStrategyDispatch
 
     SymIntLike = torch.SymInt | int
     ShapeLike = Sequence[SymIntLike]
@@ -61,6 +62,70 @@ def _normalize_negative_index(
     return f"({state.codegen.device_function.user_sympy_expr(sympy_expr)})"
 
 
+def _append_remaining_dimensions(
+    input_size: collections.deque,
+    output_size: list[int | torch.SymInt],
+    env: CompileEnvironment,
+) -> None:
+    """Append remaining dimensions from input to output for partial indexing.
+
+    Args:
+        input_size: Deque of remaining input dimensions
+        output_size: List to append output dimensions to
+        env: The compile environment
+    """
+    while input_size:
+        size = input_size.popleft()
+        if size != 1:
+            rdim = env.allocate_reduction_dimension(size)
+            output_size.append(rdim.var)
+        else:
+            output_size.append(1)
+
+
+def _handle_remaining_index_dimensions(
+    index_values: list[str],
+    mask_values: dict[str, None],
+    output_size: list[int | torch.SymInt],
+    output_idx: int,
+    fake_value: torch.Tensor,
+    state: CodegenState,
+    tile_strategy: TileStrategyDispatch,
+    env: CompileEnvironment,
+    dtype: str,
+) -> int:
+    """Handle remaining dimensions for partial indexing in SubscriptIndexing.create.
+
+    Args:
+        index_values: List to append index expressions to
+        mask_values: Dict to add mask expressions to
+        output_size: The output shape
+        output_idx: Current output index
+        fake_value: The tensor being indexed
+        state: The codegen state
+        tile_strategy: The tile strategy
+        env: The compile environment
+        dtype: The triton index type
+
+    Returns:
+        Updated output_idx
+    """
+    while len(index_values) < fake_value.ndim:
+        expand = tile_strategy.expand_str(output_size, output_idx)
+        size = fake_value.size(len(index_values))
+        if size != 1:
+            rdim = env.allocate_reduction_dimension(size)
+            block_idx = rdim.block_id
+            index_var = state.codegen.index_var(block_idx)
+            index_values.append(f"({index_var}){expand}")
+            if mask := state.codegen.mask_var(block_idx):
+                mask_values.setdefault(f"({mask}){expand}")
+        else:
+            index_values.append(f"tl.zeros([1], {dtype}){expand}")
+        output_idx += 1
+    return output_idx
+
+
 class IndexingStrategy:
     def codegen_load(
         self,
@@ -132,6 +197,32 @@ def codegen_store(
     ) -> ast.AST:
         indexing = SubscriptIndexing.create(state, fake_tensor, subscript, extra_mask)
         name = state.device_function.tensor_arg(fake_tensor).name
+
+        # Check if value is a tensor load (Name node with id matching a tensor arg)
+        if isinstance(value, ast.Name) and hasattr(
+            state.device_function, "_tensor_args"
+        ):
+            # Check if this name corresponds to a tensor argument
+            tensor = None
+            for t, tensor_arg in state.device_function._tensor_args.items():
+                if tensor_arg.name == value.id:
+                    tensor = t
+                    break
+
+            if tensor is not None:
+                # Get the shape of the slice we're storing to
+                output_shape = SubscriptIndexing.compute_shape(fake_tensor, subscript)
+                if len(output_shape) == 1 and tensor.ndim == 1:
+                    # Load the entire 1D tensor
+                    value_indexing = SubscriptIndexing.create(
+                        state, tensor, [slice(None)], None
+                    )
+                    value = expr_from_string(
+                        f"tl.load({value.id} + offset, mask)",
+                        offset=value_indexing.index_expr,
+                        mask=value_indexing.mask_expr,
+                    )
+
         return expr_from_string(
             f"tl.store({name} + offset, value, mask)",
             value=value,
@@ -503,7 +594,9 @@ def compute_shape(
     ) -> list[int | torch.SymInt]:
         assert isinstance(tensor, torch.Tensor)
         assert isinstance(index, (list, tuple)), index
-        input_size = collections.deque(tensor.size())
+        input_size: collections.deque[int | torch.SymInt] = collections.deque(
+            tensor.size()
+        )
         output_size = []
         env = CompileEnvironment.current()
         for i, k in enumerate(index):
@@ -547,7 +640,8 @@ def compute_shape(
                 output_size.extend(k.size())
             else:
                 raise exc.InvalidIndexingType(k)
-        assert len(input_size) == 0, "invalid subscript"
+        # For partial indexing, append remaining dimensions to output
+        _append_remaining_dimensions(input_size, output_size, env)
         return output_size
 
     @staticmethod
@@ -675,6 +769,20 @@ def create(
                         )
             else:
                 raise exc.InvalidIndexingType(type(k))
+
+        # Handle remaining dimensions for partial indexing
+        output_idx = _handle_remaining_index_dimensions(
+            index_values,
+            mask_values,
+            output_size,
+            output_idx,
+            fake_value,
+            state,
+            tile_strategy,
+            env,
+            dtype,
+        )
+
         assert len(output_size) == output_idx
         assert len(index_values) == fake_value.ndim
         index_expr = []
@@ -800,7 +908,9 @@ def is_supported(
         if extra_mask is not None:
             # TODO(jansel): support block_ptr with extra_mask
             return False
-        input_sizes = collections.deque(fake_tensor.size())
+        input_sizes: collections.deque[int | torch.SymInt] = collections.deque(
+            fake_tensor.size()
+        )
         for n, k in enumerate(index):
             if k is None:
                 input_size = 1

helion/_compiler/type_propagation.py

@@ -2,6 +2,7 @@
 
 import ast
 import builtins
+import collections
 import contextlib
 import dataclasses
 import functools
@@ -485,12 +486,23 @@ def _device_indexing_size(self, key: TypeInfo) -> list[int | torch.SymInt]:
                 raise exc.OverpackedTile(k)
             else:
                 raise exc.InvalidIndexingType(k)
-        if inputs_consumed != self.fake_value.ndim:
-            raise exc.RankMismatch(
-                self.fake_value.ndim,
-                inputs_consumed,
-                f"tensor shape: {tuple(self.fake_value.shape)}",
+        # Handle partial indexing - add remaining dimensions to output
+        if inputs_consumed < self.fake_value.ndim:
+            # Create a deque with remaining dimensions
+            remaining_sizes: collections.deque[int | torch.SymInt] = collections.deque(
+                self.fake_value.size(i)
+                for i in range(inputs_consumed, self.fake_value.ndim)
             )
+            if self.origin.is_device():
+                # On device, just append the sizes directly
+                output_sizes.extend(remaining_sizes)
+            else:
+                # On host, use the helper to allocate reduction dimensions
+                from helion._compiler.indexing_strategy import (
+                    _append_remaining_dimensions,
+                )
+
+                _append_remaining_dimensions(remaining_sizes, output_sizes, env)
         return output_sizes
 
     def propagate_setitem(

helion/language/_tracing_ops.py

@@ -68,7 +68,11 @@ def _host_tensor(debug_name: str) -> torch.Tensor:
 
 @_decorators.codegen(_host_tensor)
 def _(state: CodegenState) -> ast.AST:
-    return expr_from_string("_host_tensor")  # should be unused
+    # Get the tensor from the FX node metadata
+    tensor = state.fx_node.meta["val"]  # pyright: ignore[reportOptionalMemberAccess]
+    # Get the tensor argument name from the device function
+    tensor_arg = state.device_function.tensor_arg(tensor)
+    return expr_from_string(tensor_arg.name)
 
 
 @has_side_effect

test/test_indexing.py

@@ -808,9 +808,6 @@ def kernel(
         torch.testing.assert_close(src_result, expected_src)
         torch.testing.assert_close(dst_result, expected_dst)
 
-    @skipIfNormalMode(
-        "RankMismatch: Expected ndim=2, but got ndim=1 - tensor value assignment shape mismatch"
-    )
     def test_tensor_value(self):
         """Test both setter from tensor value and getter for [i]"""