This revision drops init_tensor arguments from Linalg on tensors and instead uniformizes the output buffers and output tensors to be consistent.
This significantly simplifies the usage of Linalg on tensors and is a stepping stone for
its evolution towards a mixed tensor and shape abstraction discussed in https://llvm.discourse.group/t/linalg-and-shapes/2421/19.
Differential Revision: https://reviews.llvm.org/D93469
We lower them to a std.global_memref (uniqued by constant value) + a
std.get_global_memref to produce the corresponding memref value.
This allows removing Linalg's somewhat hacky lowering of tensor
constants, now that std properly supports this.
Differential Revision: https://reviews.llvm.org/D91306
It was incorrect in the presence of a tensor argument with multiple
uses.
The bufferization of subtensor_insert was writing into a converted
memref operand, but there is no guarantee that the converted memref for
that operand is safe to write into. In this case, the same converted
memref is written to in-place by the subtensor_insert bufferization,
violating the tensor-level semantics.
I left some comments in a TODO about ways forward on this. I will be
working actively on this problem in the coming days.
Differential Revision: https://reviews.llvm.org/D91371
Previously, linalg-bufferize was a "finalizing" bufferization pass (it
did a "full" conversion). This wasn't great because it couldn't be used
composably with other bufferization passes like std-bufferize and
scf-bufferize.
This patch makes linalg-bufferize a composable bufferization pass.
Notice that the integration tests are switched over to using a pipeline
of std-bufferize, linalg-bufferize, and (to finalize the conversion)
func-bufferize. It all "just works" together.
While doing this transition, I ran into a nasty bug in the 1-use special
case logic for forwarding init tensors. That logic, while
well-intentioned, was fundamentally flawed, because it assumed that if
the original tensor value had one use, then the converted memref could
be mutated in place. That assumption is wrong in many cases. For
example:
```
%0 = some_tensor : tensor<4xf32>
br ^bb0(%0, %0: tensor<4xf32>, tensor<4xf32>)
^bb0(%bbarg0: tensor<4xf32>, %bbarg1: tensor<4xf32>)
// %bbarg0 is an alias of %bbarg1. We cannot safely write
// to it without analyzing uses of %bbarg1.
linalg.generic ... init(%bbarg0) {...}
```
A similar example can happen in many scenarios with function arguments.
Even more sinister, if the converted memref is produced by a
`std.get_global_memref` of a constant global memref, then we might
attempt to write into read-only statically allocated storage! Not all
memrefs are writable!
Clearly, this 1-use check is not a local transformation that we can do
on the fly in this pattern, so I removed it.
The test is now drastically shorter and I basically rewrote the CHECK
lines from scratch because:
- the new composable linalg-bufferize just doesn't do as much, so there
is less to test
- a lot of the tests were related to the 1-use check, which is now gone,
so there is less to test
- the `-buffer-hoisting -buffer-deallocation` is no longer mixed in, so
the checks related to that had to be rewritten
Differential Revision: https://reviews.llvm.org/D90657
The current BufferPlacement transformation contains several concepts for
hoisting allocations. However, more advanced hoisting techniques should not be
integrated into the BufferPlacement transformation. Hence, this CL refactors the
current BufferPlacement pass into three separate pieces: BufferDeallocation and
BufferAllocation(Loop)Hoisting. Moreover, it extends the hoisting functionality
by allowing to move allocations out of loops.
Differential Revision: https://reviews.llvm.org/D87756
