When establishing the correspondence between transform values and
payload operations or parameters, check that the latter are non-null and
report errors. This was previously allowed for exotic cases of partially
successfull transformations with "apply each" trait, but was dangerous.
The "apply each" implementation was reworked to remove the need for this
functionality, so this can now be hardned to avoid null pointer
dereferences.
Reviewed By: nicolasvasilache
Differential Revision: https://reviews.llvm.org/D141142
Adapt the implementation of TransformEachOpTrait to the existence of
parameter values recently introduced into the transform dialect. In
particular, allow `applyToOne` hooks to return a list containing a mix
of `Operation *` that will be associated with handles and `Attribute`
that will be associated with parameter values by the trait
implementation of the transform interface's `apply` method.
Disentangle the "transposition" of the list of per-payload op partial
results to decrease its overall complexity and detemplatize the code
that doesn't really need templates. This removes the poorly documented
special handling for single-result ops with TransformEachOpTrait that
could have assigned null pointer values to handles.
Reviewed By: springerm
Differential Revision: https://reviews.llvm.org/D140979
This makes it more consistent with the recently added
TransformParamTypeInterface.
Reviewed By: springerm
Differential Revision: https://reviews.llvm.org/D140977
Introduce a new kind of values into the transform dialect -- parameter
values. These values have a type implementing the new
`TransformParamTypeInterface` and are associated with lists of
attributes rather than lists of payload operations. This mechanism
allows one to wrap numeric calculations, typically heuristics, into
transform operations separate from those at actually applying the
transformation. For example, tile size computation can be now separated
from tiling itself, and not hardcoded in the transform dialect. This
further improves the separation of concerns between transform choice and
implementation.
Reviewed By: springerm
Differential Revision: https://reviews.llvm.org/D140976
This is generated by running
```
sed --in-place 's/[[:space:]]\+$//' mlir/**/*.td
sed --in-place 's/[[:space:]]\+$//' mlir/**/*.mlir
```
Reviewed By: rriddle, dcaballe
Differential Revision: https://reviews.llvm.org/D138866
This patch takes the first step towards a more principled modeling of undefined behavior in MLIR as discussed in the following discourse threads:
1. https://discourse.llvm.org/t/semantics-modeling-undefined-behavior-and-side-effects/4812
2. https://discourse.llvm.org/t/rfc-mark-tensor-dim-and-memref-dim-as-side-effecting/65729
This patch in particular does the following:
1. Introduces a ConditionallySpeculatable OpInterface that dynamically determines whether an Operation can be speculated.
2. Re-defines `NoSideEffect` to allow undefined behavior, making it necessary but not sufficient for speculation. Also renames it to `NoMemoryEffect`.
3. Makes LICM respect the above semantics.
4. Changes all ops tagged with `NoSideEffect` today to additionally implement ConditionallySpeculatable and mark themselves as always speculatable. This combined trait is named `Pure`. This makes this change NFC.
For out of tree dialects:
1. Replace `NoSideEffect` with `Pure` if the operation does not have any memory effects, undefined behavior or infinite loops.
2. Replace `NoSideEffect` with `NoSideEffect` otherwise.
The next steps in this process are (I'm proposing to do these in upcoming patches):
1. Update operations like `tensor.dim`, `memref.dim`, `scf.for`, `affine.for` to implement a correct hook for `ConditionallySpeculatable`. I'm also happy to update ops in other dialects if the respective dialect owners would like to and can give me some pointers.
2. Update other passes that speculate operations to consult `ConditionallySpeculatable` in addition to `NoMemoryEffect`. I could not find any other than LICM on a quick skim, but I could have missed some.
3. Add some documentation / FAQs detailing the differences between side effects, undefined behavior, speculatabilty.
Reviewed By: rriddle, mehdi_amini
Differential Revision: https://reviews.llvm.org/D135505
Introduce a type system for the transform dialect. A transform IR type
captures the expectations of the transform IR on the payload IR
operations that are being transformed, such as being of a certain kind
or implementing an interface that enables the transformation. This
provides stricter checking and better readability of the transform IR
than using the catch-all "handle" type.
This change implements the basic support for a type system amendable to
dialect extensions and adds a drop-in replacement for the unrestricted
"handle" type. The actual switch of transform dialect ops to that type
will happen in a separate commit.
See https://discourse.llvm.org/t/rfc-type-system-for-the-transform-dialect/65702
Reviewed By: nicolasvasilache
Differential Revision: https://reviews.llvm.org/D135164
Relax the restriction in the transform dialect interpreter utilities
that expected a payload IR op to be assocaited with at most one
transform IR handle value. This was useful during the initial
bootstrapping to avoid use-after-free error equivalents when a payload
IR op could be erased through one of the handles associated with it and
then accessed through another. It was, however, possible to erase an
ancestor of the payload IR operation in question. The expensive-checks
mode of interpretation is able to detect both cases and has proven
sufficiently robust in debugging use-after-free errors.
Reviewed By: springerm
Differential Revision: https://reviews.llvm.org/D134964
A recent commit introduced helper functions with semantically meaningful names
to populate the lists of memory effects in transform ops, use them whenever
possible.
Depends On D129287
Reviewed By: springerm
Differential Revision: https://reviews.llvm.org/D129365
This handle manipulation operation allows one to define a new handle that is
associated with a the same payload IR operations N times, where N can be driven
by the size of payload IR operation list associated with another handle. This
can be seen as a sort of broadcast that can be used to ensure the lists
associated with two handles have equal numbers of payload IR ops as expected by
many pairwise transform operations.
Introduce an additional "expensive" check that guards against consuming a
handle that is assocaited with the same payload IR operation more than once as
this is likely to lead to double-free or other undesired effects.
Depends On D129110
Reviewed By: nicolasvasilache
Differential Revision: https://reviews.llvm.org/D129216
This revision revisits the implementation of applyToOne and its handling
of recoverable errors as well as propagation of null handles.
The implementation is simplified to always require passing a vector<Operation*>
in which the results are returned, resulting in less template instantiation magic.
Reviewed By: ftynse
Differential Revision: https://reviews.llvm.org/D129185
The result of applying an N-result producing transformation to M payload ops
is an M-wide result, each containing N result operations.
This requires a transposition of the results obtained by calling `applyToOne`.
This revision fixes the issue and adds more advanced tests that exercise the behavior.
Differential Revision: https://reviews.llvm.org/D128414
This revision separates the `LinalgSplitReduction` pattern, whose application is based on attributes,
from its implementation.
A transform dialect op extension is added to control the application of the transformation at a finer granularity.
Differential Revision: https://reviews.llvm.org/D128165
Introduce a transform dialect op that allows one to attempt different
transformation sequences on the same piece of payload IR until one of them
succeeds. This op fundamentally expands the scope of possibilities in the
transform dialect that, until now, could only propagate transformation failure,
at least using in-tree operations. This requires a more detailed specification
of the execution model for the transform dialect that now indicates how failure
is handled and propagated.
Transformations described by transform operations now have tri-state results,
with some errors being fundamentally irrecoverable (e.g., generating malformed
IR) and some others being recoverable by containing ops. Existing transform ops
directly implementing the `apply` interface method are updated to produce this
directly. Transform ops with the `TransformEachTransformOpTrait` are currently
considered to produce only irrecoverable failures and will be updated
separately.
Reviewed By: springerm
Differential Revision: https://reviews.llvm.org/D127724
In the transform dialect, a transform IR handle may be pointing to a payload IR
operation that is an ancestor of another payload IR operation pointed to by
another handle. If such a "parent" handle is consumed by a transformation, this
indicates that the associated operation is likely rewritten, which in turn
means that the "child" handle may now be associated with a dangling pointer or
a pointer to a different operation than originally. Add a handle invalidation
mechanism to guard against such situations by reporting errors at runtime.
Reviewed By: springerm
Differential Revision: https://reviews.llvm.org/D127480
The Transform dialect uses the side effect modeling mechanism to record the
effects of the transform ops on the mapping between Transform IR values and
Payload IR ops. Introduce a checker pass that warns if a Transform IR value is
used after it has been freed (consumed). This pass is mostly intended as a
debugging aid in addition to the verification/assertion mechanisms in the
transform interpreter. It reports all potential use-after-free situations.
The implementation makes a series of simplifying assumptions to be simple and
conservative. A more advanced implementation would rely on the data flow-like
analysis associated with a side-effect resource rather than a value, which is
currently not supported by the analysis infrastructure.
Reviewed By: springerm
Differential Revision: https://reviews.llvm.org/D126381
Add the mechanism for TransformState extensions to update the mapping between
Transform IR values and Payload IR operations held by the state. The mechanism
is intentionally restrictive, similarly to how results of the transform op are
handled.
Introduce test ops that exercise a simple extension that maintains information
across the application of multiple transform ops.
Reviewed By: nicolasvasilache
Differential Revision: https://reviews.llvm.org/D124778
Currently, the sequence of Transform dialect operations only supports a single
use of each operand (verified by the `transform.sequence` operation). This was
originally motivated by the need to guard against accessing a payload IR
operation associated with a transform IR value after this operation has likely
been rewritten by a transformation. However, not all Transform dialect
operations rewrite payload IR, in particular the "navigation" operation such as
`transform.pdl_match` do not.
Introduce memory effects to the Transform dialect operations to describe their
effect on the payload IR and the mapping between payload IR opreations and
transform IR values. Use these effects to replace the single-use rule, allowing
repeated reads and disallowing use-after-free, where operations with the "free"
effect are considered to "consume" the transform IR value and rewrite the
corresponding payload IR operations). As an additional improvement, this
enables code motion transformation on the transform IR itself.
Reviewed By: Mogball
Differential Revision: https://reviews.llvm.org/D124181
This introduces a pair of ops to the Transform dialect that connect it to PDL
patterns. Transform dialect relies on PDL for matching the Payload IR ops that
are about to be transformed. For this purpose, it provides a container op for
patterns, a "pdl_match" op and transform interface implementations that call
into the pattern matching infrastructure.
To enable the caching of compiled patterns, this also provides the extension
mechanism for TransformState. Extensions allow one to store additional
information in the TransformState and thus communicate it between different
Transform dialect operations when they are applied. They can be added and
removed when applying transform ops. An extension containing a symbol table in
which the pattern names are resolved and a pattern compilation cache is
introduced as the first client.
Depends On D123664
Reviewed By: Mogball
Differential Revision: https://reviews.llvm.org/D124007
This dialect provides operations that can be used to control transformation of
the IR using a different portion of the IR. It refers to the IR being
transformed as payload IR, and to the IR guiding the transformation as
transform IR.
The main use case for this dialect is orchestrating fine-grain transformations
on individual operations or sets thereof. For example, it may involve finding
loop-like operations with specific properties (e.g., large size) in the payload
IR, applying loop tiling to those and only those operations, and then applying
loop unrolling to the inner loops produced by the previous transformations. As
such, it is not intended as a replacement for the pass infrastructure, nor for
the pattern rewriting infrastructure. In the most common case, the transform IR
will be processed and applied to payload IR by a pass. Transformations
expressed by the transform dialect may be implemented using the pattern
infrastructure or any other relevant MLIR component.
This dialect is designed to be extensible, that is, clients of this dialect are
allowed to inject additional operations into this dialect using the newly
introduced in this patch `TransformDialectExtension` mechanism. This allows the
dialect to avoid a dependency on the implementation of the transformation as
well as to avoid introducing dialect-specific transform dialects.
See https://discourse.llvm.org/t/rfc-interfaces-and-dialects-for-precise-ir-transformation-control/60927.
Reviewed By: nicolasvasilache, Mogball, rriddle
Differential Revision: https://reviews.llvm.org/D123135
