ekalda commented on code in PR #16523:
URL: https://github.com/apache/tvm/pull/16523#discussion_r1481332421
##########
include/tvm/runtime/data_type.h:
##########
@@ -114,17 +118,28 @@ class DataType {
/*! \return whether type is a handle type. */
bool is_handle() const { return code() == DataType::kHandle && !is_void(); }
/*! \return whether type is a vector type. */
- bool is_vector() const { return lanes() > 1; }
+ bool is_vector() const {
+ int encoded_lanes = static_cast<int16_t>(data_.lanes);
+ return encoded_lanes != 0 && encoded_lanes != 1;
+ }
/*! \return whether type is a bool vector type. */
bool is_vector_bool() const { return is_vector() && bits() == 1; }
/*! \return whether type is a Void type. */
bool is_void() const { return code() == DataType::kHandle && bits() == 0 &&
lanes() == 0; }
+ /*! \return Whether the type is scalable. */
+ bool is_scalable() const { return static_cast<int16_t>(data_.lanes) < 0; }
/*!
* \brief Create a new data type by change lanes to a specified value.
* \param lanes The target number of lanes.
* \return the result type.
*/
DataType with_lanes(int lanes) const { return DataType(data_.code,
data_.bits, lanes); }
+ /*!
+ * \brief Create a new scalable data type by changing the lanes to a
specified value.
+ * \param lanes The target number of lanes.
Review Comment:
Thanks @tqchen, thinking about it, you're right, the "lanes" of the scalable
vectors in the current implementation is a bit of a misnomer and in general
causes a lot of issues where the scalability is silently ignored or dropped in
the passes. So I'm in favour of separating the APIs for fixed length and
scalable vectors. Here's a proposal for cleaning it up (it should address your
other comments in this file as well):
* Rename `is_scalable()` -> `is_scalable_vector()` - return `True` if it is
scalable vector, `False` otherwise
* Add `is_fixed_length_vector()` method to check if it is a fixed length
vector
* `is_vector()` should return `True` if it is a vector (scalable or fixed
length) and `False` otherwise
* Reserve `lanes()` for fixed length vectors, i.e. if this function is
called on a scalable vector, return an error
* Add `vscale_factor()` that returns the integer multiplier (so it would be
a scalable vector equivalent of `lanes()`)
* Rename `with_scalable_lanes(lanes)` ->
`with_scalable_vscale_factor(vscale_factor)`
Throughout the codebase `dtype.lanes() != 1` is used as a shorthand to test
for "vectorness", it would be good to replace these instances with
`is_vector()`/`is_fixed_length_vector()`/`is_scalable_vector()` as appropriate.
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