Lunderberg commented on code in PR #17219:
URL: https://github.com/apache/tvm/pull/17219#discussion_r1698515074
##########
src/tir/ir/buffer.cc:
##########
@@ -334,24 +334,38 @@ inline Array<PrimExpr> BufferOffset(const BufferNode* n,
Array<PrimExpr> index,
return offsets;
}
-Buffer Buffer::GetFlattenedBuffer() const {
- auto self = operator->();
-
+static void ValidateAxisSeparators(const Array<IntImm>& axis_separators,
size_t buffer_dim) {
// These checks ensure that all output axes contain at least one
// input axis.
- for (size_t i = 0; (i + 1) < self->axis_separators.size(); i++) {
- auto sep = self->axis_separators[i]->value;
- auto next_sep = self->axis_separators[i + 1]->value;
- ICHECK_LT(sep, next_sep) << "Axis separators must be in strictly
increasing order.";
- }
- if (self->axis_separators.size()) {
- auto first_sep = self->axis_separators[0]->value;
- ICHECK_GT(first_sep, 0) << "First axis separator must be strictly greater
than 0, "
- << "so that first output axis contains at least
one input axis";
- auto last_sep = self->axis_separators[self->axis_separators.size() -
1]->value;
- ICHECK_LT(last_sep, self->shape.size())
- << "Last output axis must contain at least one input axis.";
+ for (size_t i = 0; (i + 1) < axis_separators.size(); i++) {
+ auto sep = axis_separators[i]->value;
+ auto next_sep = axis_separators[i + 1]->value;
+ CHECK_LT(sep, next_sep) << "ValueError: "
+ << "Axis separators must be in strictly increasing
order, "
+ << "but axis_separators[" << i << "] = " << sep
+ << " is greater than or equal to axis_separators["
<< (i + 1)
+ << "] = " << next_sep << ".";
+ }
+ if (axis_separators.size()) {
+ auto first_sep = axis_separators[0]->value;
+ CHECK_GT(first_sep, 0) << "ValueError: "
+ << "First axis separator must be strictly greater
than 0, "
+ << "so that first output axis contains at least one
input axis. "
+ << "However, the axis_separators[0] = " <<
first_sep;
+ auto last_sep = axis_separators[axis_separators.size() - 1]->value;
+ CHECK_LT(last_sep, buffer_dim)
+ << "ValueError: "
+ << "Last output axis must contain at least one input axis. "
+ << "However, the axis_separators[" << (axis_separators.size() - 1) <<
"] = " << last_sep
+ << " does not leave any input axes between it and the buffer's
dimensionality "
+ << buffer_dim;
Review Comment:
I'm not sure the best way forward on it, as buffer views have always had a
bit of this problem. They have enough information to show/implement element
access of a buffer, but some of the fields (e.g. `strides`) aren't used when
lowering. But at least for `strides`, the field can be set to a value that is
consistent with the parent buffer. For `axis_separators`, the view may not
have sufficient information to determine the flattened shape.
That said, being able to determine the physical dimensionality of a
`tir::Buffer`, regardless of whether it is a view or the original, is useful.
I like your idea of relaxing the `CHECK_GT` and `CHECK_LT` conditions to
`CHECK_GE` and `CHECK_LE`, as it would let these cases be better expressed.
That would allow a physical axis with extent 1 to be determined from an empty
set of logical axes.
(This change all came up from [this failing unit
test](https://github.com/apache/tvm/pull/17219/files#diff-6c21ac3bae4a648708cb2b84c1e975dd9b80b25dada4fc964ed6a2e688b2913cR99).
The `B_subregion0` buffer couldn't satisfy the constraints
`len(view.axis_separators) < len(view.shape)` and `len(view.axis_separators) ==
len(backing_alloc_buf.axis_separators)` at the same time.)
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