[Mlir-commits] [mlir] [mlir][tensor][NFC] Improve documentation of pack/unpack (PR #72201)

[lorenzo chelini]

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@@ -1753,42 +1753,66 @@ def Tensor_PackOp : Tensor_RelayoutOp<"pack", [
     AttrSizedOperandSegments]> {
   let summary = "tensor pack operation";
   let description = [{
-    The pack operation converts an input tensor to a higher-dimensional tensor
-    with a tiled and packed layout. The mandatory `inner_dims_pos` attribute
-    specifies a permutation for the original dimensions, while `inner_tiles` is the
-    tiling factor for each dimension. The optional attribute `outer_dims_perm`
-    specifies the order for the tiled data dimension, while the attribute
-    `padding_value` specifies a padding value at the boundary on non-perfectly
-    divisible dimensions. Padding is optional:
-    - If absent, it is UB if the tile does not perfectly divide the dimension.
-    - If present, it will pad along high dimensions (high-padding) to make the
-      tile complete.
+    The "pack" operation converts a source tensor of rank `n` into a result
+    tensor of rank `n + k` with a tiled and packed layout (maybe with padding)
+    and optionally transposes the original tiled loop dimensions.
+
+    `inner_dims_pos` (mandatory) specifies `k` source tensor dimensions that are
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chelini wrote:

...The order of the dimensions matters: the tiled dimensions (of size `inner_tiles`) are added to the end of the result tensor in the order in which they appear in `inner_dims_pos`.... Is a bit confusing. The order in which we append the tile for the result tensor is basically `inner_tiles`, it is not the order given by `inner_dims_pos`.

I would re-write as: `inner_dims_pos` (mandatory) specifies `k` source tensor dimensions being tiled, where `0 < k <= n`. The order of the dimensions matters: `inner_dims_pos[k]` represents the source tensor dimension index tiled by the tile size at position `k` in `inner_tiles.`


https://github.com/llvm/llvm-project/pull/72201