The `constFoldBinaryOp` helper function had limited support for
different input and output types, but the static type of the underlying
value (e.g. `APInt`) had to match between the inputs and the output.
This worked fine for int comparisons of the form `(intN, intN) -> int1`,
as the static type signature was `(APInt, APInt) -> APInt`. However,
float comparisons map `(floatN, floatN) -> int1`, with a static type
signature of `(APFloat, APFloat) -> APInt`. This use case wasn't
supported by `constFoldBinaryOp`.
`constFoldBinaryOp` now accepts an optional template argument overriding
the return type in case it differs from the input type. If the new
template argument isn't provided, the default behavior is unchanged
(i.e. the return type will be assumed to match the input type).
`constFoldUnaryOp` received similar changes in order to support folding
non-cast ops of the form `(T1) -> T2` (e.g. a `sign` op mapping
`(floatN) -> sint32`).
When a conversion pattern is initialized without a type converter, the
driver implementation currently looks up the most recently mapped value.
This is undesirable because the most recently mapped value could be a
materialization. I.e., the type of the value being looked up could
depend on which other patterns have run before. Such an implementation
makes the type conversion infrastructure fragile and unpredictable.
The current implementation also contradicts the documentation in the
markdown file. According to that documentation, the values provided by
the adaptor should match the types of the operands of the match
operation when running without a type converter. This mechanism is not
desirable, either, for two reasons:
1. Some patterns have started to rely on receiving the most recently
mapped value. Changing the behavior to the documented behavior will
cause regressions. (And there would be no easy way to fix those without
forcing the use of a type converter or extending the `getRemappedValue`
API.)
2. It is more useful to receive the most recently mapped value. A value
of the original operand type can be retrieved by using the operand of
the matched operation. The adaptor is not needed at all in that case.
To implement the new behavior, materializations are now annotated with a
marker attribute. The marker is needed because not all
`unrealized_conversion_cast` ops are materializations that act as "pure
type conversions". E.g., when erasing an operation, its results are
mapped to newly-created "out-of-thin-air values", which are
materializations (with no input) that should be treated like regular
replacement values during a lookup. This marker-based lookup strategy is
also compatible with the One-Shot Dialect Conversion implementation
strategy, which does not utilize the mapping infrastructure anymore and
queries all necessary information by examining the IR.
This PR uses `val.getDefiningOp<OpTy>()` to replace `dyn_cast<OpTy>(val.getDefiningOp())` , `dyn_cast_or_null<OpTy>(val.getDefiningOp())` and `dyn_cast_if_present<OpTy>(val.getDefiningOp())`.
ArrayRef has a constructor that accepts std::nullopt. This
constructor dates back to the days when we still had llvm::Optional.
Since the use of std::nullopt outside the context of std::optional is
kind of abuse and not intuitive to new comers, I would like to move
away from the constructor and eventually remove it.
This patch migrates away from std::nullopt in favor of ArrayRef<T>()
where we use perfect forwarding. Note that {} would be ambiguous for
perfect forwarding to work.
This commit adds 1:N support to
`ConversionPatternRewriter::replaceUsesOfBlockArgument`. This was one of
the few remaining dialect conversion APIs that does not support 1:N
conversions yet.
This commit also reuses `replaceUsesOfBlockArgument` in the
implementation of `applySignatureConversion`. This is in preparation of
the One-Shot Dialect Conversion refactoring. The goal is to bring the
`applySignatureConversion` implementation into a state where it works
both with and without rollbacks. To that end, `applySignatureConversion`
should not directly access the `mapping`.
ArrayRef has a constructor that accepts std::nullopt. This
constructor dates back to the days when we still had llvm::Optional.
Since the use of std::nullopt outside the context of std::optional is
kind of abuse and not intuitive to new comers, I would like to move
away from the constructor and eventually remove it.
One of the uses of std::nullopt is in a the constructors for
TypeRange. This patch takes care of the migration where we need
TypeRange() to facilitate perfect forwarding. Note that {} would be
ambiguous for perfecting forwarding to work.
This is similar to other configuration objects used across MLIR.
Rename some fields to better reflect that they are no longer booleans.
Reland 04d261101b4f229189463136a794e3e362a793af / #132253.
I observed that we have the boundary comments in the codebase like:
```
//===----------------------------------------------------------------------===//
// ...
//===----------------------------------------------------------------------===//
```
I also observed that there are incomplete boundary comments. The
revision is generated by a script that completes the boundary comments.
```
//===----------------------------------------------------------------------===//
// ...
...
```
Signed-off-by: hanhanW <hanhan0912@gmail.com>
This commit adds an additional overload to `replaceOpWithMultiple` that
accepts additional container types. This has been brought up by users of
the new `replaceOpWithMultiple` API.
In particular, one missing container type was
`SmallVector<SmallVector<Value>>`. The "default" `ArrayRef<ValueRange>`
container type can lead to use-after-scope errors in cases such as:
```c++
// Compute the replacement value ranges. Some replacements are single
// values, some are value ranges.
SmallVector<ValueRange> repl;
repl.push_back(someValueRange); // OK
for (...) {
// push_back(Value) triggers an implicit conversion to ValueRange,
// which does not own the range.
repl.push_back(someValue); // triggers use-after-scope later
}
rewriter.replaceOpWithMultiple(op, repl);
```
In this example, users should use `SmallVector<SmallVector<Value>>
repl;`.
This commit adds 1:N support to `SignatureConversion::remapInputs`. This
API allows users to replace a block argument with multiple replacement
values. (And the block argument is dropped.) The API already supported
"bbarg --> multiple bbargs" mappings, but "bbarg --> multiple SSA
values" was missing.
---------
Co-authored-by: Markus Böck <markus.boeck02@gmail.com>
This commit updates the internal `ConversionValueMapping` data structure
in the dialect conversion driver to support 1:N replacements. This is
the last major commit for adding 1:N support to the dialect conversion
driver.
Since #116470, the infrastructure already supports 1:N replacements. But
the `ConversionValueMapping` still stored 1:1 value mappings. To that
end, the driver inserted temporary argument materializations (converting
N SSA values into 1 value). This is no longer the case. Argument
materializations are now entirely gone. (They will be deleted from the
type converter after some time, when we delete the old 1:N dialect
conversion driver.)
Note for LLVM integration: Replace all occurrences of
`addArgumentMaterialization` (except for 1:N dialect conversion passes)
with `addSourceMaterialization`.
---------
Co-authored-by: Markus Böck <markus.boeck02@gmail.com>
This commit adds a test case that performs two back-to-back 1:N
replacements: `(i16) -> (i16, i16) -> ((i16, i16), (i16, i16))`. For the
moment, 3 argument materializations are inserted. In the future (when
the conversion value mapping supports 1:N), a single target
materialization will be inserted. Addresses a
[comment](https://github.com/llvm/llvm-project/pull/116524#discussion_r1894629711)
in #116524.
During a 1:N replacement (`applySignatureConversion` or
`replaceOpWithMultiple`), the dialect conversion driver used to insert
two materializations:
* Argument materialization: convert N replacement values to 1 SSA value
of the original type `S`.
* Target materialization: convert original type to legalized type `T`.
The target materialization is unnecessary. Subsequent patterns receive
the replacement values via their adaptors. These patterns have their own
type converter. When they see a replacement value of type `S`, they will
automatically insert a target materialization to type `T`. There is no
reason to do this already during the 1:N replacement. (The functionality
used to be duplicated in `remapValues` and `insertNTo1Materialization`.)
Special case: If a subsequent pattern does not have a type converter, it
does *not* insert any target materializations. That's because the
absence of a type converter indicates that the pattern does not care
about type legality. Therefore, it is correct to pass an SSA value of
type `S` (or any other type) to the pattern.
Note: Most patterns in `TestPatterns.cpp` run without a type converter.
To make sure that the tests still behave the same, some of these
patterns now have a type converter.
This commit is in preparation of adding 1:N support to the conversion
value mapping. Before making any further changes to the mapping
infrastructure, I'd like to make sure that the code base around it (that
uses the mapping) is robust.
The greedy rewriter is used in many different flows and it has a lot of
convenience (work list management, debugging actions, tracing, etc). But
it combines two kinds of greedy behavior 1) how ops are matched, 2)
folding wherever it can.
These are independent forms of greedy and leads to inefficiency. E.g.,
cases where one need to create different phases in lowering and is
required to applying patterns in specific order split across different
passes. Using the driver one ends up needlessly retrying folding/having
multiple rounds of folding attempts, where one final run would have
sufficed.
Of course folks can locally avoid this behavior by just building their
own, but this is also a common requested feature that folks keep on
working around locally in suboptimal ways.
For downstream users, there should be no behavioral change. Updating
from the deprecated should just be a find and replace (e.g., `find ./
-type f -exec sed -i
's|applyPatternsAndFoldGreedily|applyPatternsGreedily|g' {} \;` variety)
as the API arguments hasn't changed between the two.
This commit adds a new `matchAndRewrite` overload to `ConversionPattern`
to support 1:N replacements. This is the first of two main PRs that
merge the 1:1 and 1:N dialect conversion drivers.
The existing `matchAndRewrite` function supports only 1:1 replacements,
as can be seen from the `ArrayRef<Value>` parameter.
```c++
LogicalResult ConversionPattern::matchAndRewrite(
Operation *op, ArrayRef<Value> operands /*adaptor values*/,
ConversionPatternRewriter &rewriter) const;
```
This commit adds a `matchAndRewrite` overload that is called by the
dialect conversion driver. By default, this new overload dispatches to
the original 1:1 `matchAndRewrite` implementation. Existing
`ConversionPattern`s do not need to be changed as long as there are no
1:N type conversions or value replacements.
```c++
LogicalResult ConversionPattern::matchAndRewrite(
Operation *op, ArrayRef<ValueRange> operands /*adaptor values*/,
ConversionPatternRewriter &rewriter) const {
// Note: getOneToOneAdaptorOperands produces a fatal error if at least one
// ValueRange has 0 or more than 1 value.
return matchAndRewrite(op, getOneToOneAdaptorOperands(operands), rewriter);
}
```
The `ConversionValueMapping`, which keeps track of value replacements
and materializations, still does not support 1:N replacements. We still
rely on argument materializations to convert N replacement values back
into a single value. The `ConversionValueMapping` will be generalized to
1:N mappings in the second main PR.
Before handing the adaptor values to a `ConversionPattern`, all argument
materializations are "unpacked". The `ConversionPattern` receives N
replacement values and does not see any argument materializations. This
implementation strategy allows us to use the 1:N infrastructure/API in
`ConversionPattern`s even though some functionality is still missing in
the driver. This strategy was chosen to keep the sizes of the PRs
smaller and to make it easier for downstream users to adapt to API
changes.
This commit also updates the the "decompose call graphs" transformation
and the "sparse tensor codegen" transformation to use the new 1:N
`ConversionPattern` API.
Note for LLVM conversion: If you are using a type converter with 1:N
type conversion rules or if your patterns are performing 1:N
replacements (via `replaceOpWithMultiple` or
`applySignatureConversion`), conversion pattern applications will start
failing (fatal LLVM error) with this error message: `pattern 'name' does
not support 1:N conversion`. The name of the failing pattern is shown in
the error message. These patterns must be updated to the new 1:N
`matchAndRewrite` API.
This commit adds support for 1:N result type conversions for `func.call`
ops. In that case, argument materializations to the original result type
should be inserted (via `replaceOpWithMultiple`).
This commit is in preparation of merging the 1:1 and 1:N conversion
drivers.
This is intended as a fast pattern rewrite driver for the cases when a
simple walk gets the job done but we would still want to implement it in
terms of rewrite patterns (that can be used with the greedy pattern
rewrite driver downstream).
The new driver is inspired by the discussion in
https://github.com/llvm/llvm-project/pull/112454 and the LLVM Dev
presentation from @matthias-springer earlier this week.
This limitation comes with some limitations:
* It does not repeat until a fixpoint or revisit ops modified in place
or newly created ops. In general, it only walks forward (in the
post-order).
* `matchAndRewrite` can only erase the matched op or its descendants.
This is verified under expensive checks.
* It does not perform folding / DCE.
We could probably relax some of these in the future without sacrificing
too much performance.
This commit simplifies the result type of materialization functions.
Previously: `std::optional<Value>`
Now: `Value`
The previous implementation allowed 3 possible return values:
- Non-null value: The materialization function produced a valid
materialization.
- `std::nullopt`: The materialization function failed, but another
materialization can be attempted.
- `Value()`: The materialization failed and so should the dialect
conversion. (Previously: Dialect conversion can roll back.)
This commit removes the last variant. It is not particularly useful
because the dialect conversion will fail anyway if all other
materialization functions produced `std::nullopt`.
Furthermore, in contrast to type conversions, at least one
materialization callback is expected to succeed. In case of a failing
type conversion, the current dialect conversion can roll back and try a
different pattern. This also used to be the case for materializations,
but that functionality was removed with #107109: failed materializations
can no longer trigger a rollback. (They can just make the entire dialect
conversion fail without rollback.) With this in mind, it is even less
useful to have an additional error state for materialization functions.
This commit is in preparation of merging the 1:1 and 1:N type
converters. Target materializations will have to return multiple values
instead of a single one. With this commit, we can keep the API simple:
`SmallVector<Value>` instead of `std::optional<SmallVector<Value>>`.
Note for LLVM integration: All 1:1 materializations should return
`Value` instead of `std::optional<Value>`. Instead of `std::nullopt`
return `Value()`.
This commit makes source/target/argument materializations (via the
`TypeConverter` API) optional.
By default (`ConversionConfig::buildMaterializations = true`), the
dialect conversion infrastructure tries to legalize all unresolved
materializations right after the main transformation process has
succeeded. If at least one unresolved materialization fails to resolve,
the dialect conversion fails. (With an error message such as `failed to
legalize unresolved materialization ...`.) Automatic materializations
through the `TypeConverter` API can now be deactivated. In that case,
every unresolved materialization will show up as a
`builtin.unrealized_conversion_cast` op in the output IR.
There used to be a complex and error-prone analysis in the dialect
conversion that predicted the future uses of unresolved
materializations. Based on that logic, some casts (that were deemed to
unnecessary) were folded. This analysis was needed because folding
happened at a point of time when some IR changes (e.g., op replacements)
had not materialized yet.
This commit removes that analysis. Any folding of cast ops now happens
after all other IR changes have been materialized and the uses can
directly be queried from the IR. This simplifies the analysis
significantly. And certain helper data structures such as
`inverseMapping` are no longer needed for the analysis. The folding
itself is done by `reconcileUnrealizedCasts` (which also exists as a
standalone pass).
After casts have been folded, the remaining casts are materialized
through the `TypeConverter`, as usual. This last step can be deactivated
in the `ConversionConfig`.
`ConversionConfig::buildMaterializations = false` can be used to debug
error messages such as `failed to legalize unresolved materialization
...`. (It is also useful in case automatic materializations are not
needed.) The materializations that failed to resolve can then be seen as
`builtin.unrealized_conversion_cast` ops in the resulting IR. (This is
better than running with `-debug`, because `-debug` shows IR where some
IR changes have not been materialized yet.)
Note: This is a reupload of #104668, but with correct handling of cyclic
unrealized_conversion_casts that may be generated by the dialect
conversion.
This code got lost in #97213 and there was no test for it. Add it back
with an MLIR test.
When a pattern is run without a type converter, we can assume that the
new block argument types of a signature conversion are legal. That's
because they were specified by the user. This won't work for 1->N
conversions due to limitations in the dialect conversion infrastructure,
so the original `FIXME` has to stay in place.
This commit fixes a crash in the dialect conversion when applying a
signature conversion to a block inside of a detached region.
This fixes an issue reported in
4114d5be87 (r1691809730).
This commit simplifies and improves documentation for the part of the
`ConversionPatternRewriter` API that deals with signature conversions.
There are now two public functions for signature conversion:
* `applySignatureConversion` converts a single block signature. This
function used to take a `Region *` (but converted only the entry block).
It now takes a `Block *`.
* `convertRegionTypes` converts all block signatures of a region.
`convertNonEntryRegionTypes` is removed because it is not widely used
and can easily be expressed with a call to `applySignatureConversion`
inside a loop. (See `Detensorize.cpp` for an example.)
Note: For consistency, `convertRegionTypes` could be renamed to
`applySignatureConversion` (overload) in the future. (Or
`applySignatureConversion` renamed to `convertBlockTypes`.)
Also clarify when a type converter and/or signature conversion object is
needed and for what purpose.
Internal code refactoring (NFC) of `ConversionPatternRewriterImpl` (the
part that deals with signature conversions). This part of the codebase
was quite convoluted and unintuitive.
From a functional perspective, this change is NFC. However, the public
API changes, thus not marking as NFC.
Note for LLVM integration: When you see
`applySignatureConversion(region, ...)`, replace with
`applySignatureConversion(region->front(), ...)`. In the unlikely case
that you see `convertNonEntryRegionTypes`, apply the same changes as
this commit did to `Detensorize.cpp`.
---------
Co-authored-by: Markus Böck <markus.boeck02@gmail.com>
This commit changes `OpBuilder::tryFold` to behave more similarly to
`Operation::fold`. Concretely, this ensures that even an in-place fold
returns `success`.
This is necessary to fix a bug in the dialect conversion that occurred
when an in-place folding made an operation legal. The dialect conversion
infrastructure did not check if the result of an in-place folding
legalized the operation and just went ahead and tried to apply pattern
anyways.
The added test contains a simplified version of a breakage we observed
downstream.
This PR massively reorganizes the Test dialect's source files. It moves
manually-written op hooks into `TestOpDefs.cpp`, moves format custom
directive parsers and printers into `TestFormatUtils`, adds missing
comment blocks, and moves around where generated source files are
included for types, attributes, enums, etc. into their own source file.
This will hopefully help navigate the test dialect source code, but also
speeds up compile time of the test dialect by putting generated source
files into separate compilation units.
This also sets up the test dialect to shard its op definitions, done in
the next PR.
Before this change: `notifyOperationReplaced` was triggered when calling
`RewriteBase::replaceOp`.
After this change: `notifyOperationReplaced` is triggered when
`RewriterBase::replaceAllOpUsesWith` or `RewriterBase::replaceOp` is
called.
Until now, every `notifyOperationReplaced` was always sent together with
a `notifyOperationErased`, which made that `notifyOperationErased`
callback irrelevant. More importantly, when a user called
`RewriterBase::replaceAllOpUsesWith`+`RewriterBase::eraseOp` instead of
`RewriterBase::replaceOp`, no `notifyOperationReplaced` callback was
sent, even though the two notations are semantically equivalent. As an
example, this can be a problem when applying patterns with the transform
dialect because the `TrackingListener` will only see the
`notifyOperationErased` callback and the payload op is dropped from the
mappings.
Note: It is still possible to write semantically equivalent code that
does not trigger a `notifyOperationReplaced` (e.g., when op results are
replaced one-by-one), but this commit already improves the situation a
lot.
This commit adds listener support to the dialect conversion. Similarly
to the greedy pattern rewrite driver, an optional listener can be
specified in the configuration object.
Listeners are notified only if the dialect conversion succeeds. In case
of a failure, where some IR changes are first performed and then rolled
back, no notifications are sent.
Due to the fact that some kinds of rewrite are reflected in the IR
immediately and some in a delayed fashion, there are certain limitations
when attaching a listener; these are documented in `ConversionConfig`.
To summarize, users are always notified about all rewrites that
happened, but the notifications are sent all at once at the very end,
and not interleaved with the actual IR changes.
This change is in preparation improvements to
`transform.apply_conversion_patterns`, which currently invalidates all
handles. In the future, it can use a listener to update handles
accordingly, similar to `transform.apply_patterns`.
* `replaceOp` replaces all uses of the original op and erases the old
op.
* `replaceAllUsesWith` replaces all uses of the original op/value/block.
It does not erase any IR.
This commit renames `replaceOpWithIf` to `replaceUsesWithIf`.
`replaceOpWithIf` was a misnomer because the function never erases the
original op. Similarly, `replaceOpWithinBlock` is renamed to
`replaceUsesWithinBlock`. (No "operation replaced" is sent because the
op is not erased.)
Also improve comments.
This commit adds a new `ConversionConfig` struct that allows users to
customize the dialect conversion. This configuration is similar to
`GreedyRewriteConfig` for the greedy pattern rewrite driver.
A few existing options are moved to this objects, simplifying the
dialect conversion API.
This is a re-upload of #82250. The Windows build breakage was fixed in #83768.
This reverts commit 60fbd6050107875956960c3ce35cf94b202d8675.
The dialect conversion maintains sets of "ignored" and "replaced" ops.
This change simplifies the two sets, such that all nested ops are
included. (This was previously not the case and sometimes only the
parent op was included.)
This change allows for more aggressive assertions to prevent incorrect
rewriter API usage. E.g., accessing ops/blocks/regions within an erased
op.
A concrete example: I have seen conversion patterns in downstream
projects where an op is replaced with a new op, and the region of the
old op is afterwards inlined into the newly created op. This is invalid
rewriter API usage: ops that were replaced/erased should not be
accessed. Nested ops will be considered "ignored", even if they are
moved to a different region after the region's parent op was erased
(which is illegal API usage). Instead, create a new op, inline the
regions, then replace the old op with the new op.
This commit adds a new `ConversionConfig` struct that allows users to
customize the dialect conversion. This configuration is similar to
`GreedyRewriteConfig` for the greedy pattern rewrite driver.
A few existing options are moved to this objects, simplifying the
dialect conversion API.
The dialect conversion rolls back in-place op modifications upon
failure. Rolling back modifications of attributes is already supported,
but there was no support for properties until now.
Rename listener callback names:
* `notifyOperationRemoved` -> `notifyOperationErased`
* `notifyBlockRemoved` -> `notifyBlockErased`
The current callback names are misnomers. The callbacks are triggered
when an operation/block is erased, not when it is removed (unlinked).
E.g.:
```c++
/// Notify the listener that the specified operation is about to be erased.
/// At this point, the operation has zero uses.
///
/// Note: This notification is not triggered when unlinking an operation.
virtual void notifyOperationErased(Operation *op) {}
```
This change is in preparation of adding listener support to the dialect
conversion. The dialect conversion internally unlinks IR before erasing
it at a later point of time. There is an important difference between
"remove" and "erase". Lister callback names should be accurate to avoid
confusion.
Add a new rewrite class for "operation movements". This rewrite class
can roll back `moveOpBefore` and `moveOpAfter`.
`RewriterBase::moveOpBefore` and `RewriterBase::moveOpAfter` is no
longer virtual. (The dialect conversion can gather all required
information for rollbacks from listener notifications.)
Similar to `OpBuilder::clone`, operation/block insertion notifications
should be sent when cloning the contents of a region. E.g., this is to
ensure that the newly created operations are put on the worklist of the
greedy pattern rewriter driver.
Also move `cloneRegionBefore` from `RewriterBase` to `OpBuilder`. It
only creates new IR, so it should be part of the builder API (like
`clone(Operation &)`). The function does not have to be virtual. Now
that notifications are properly sent, the override in the dialect
conversion is no longer needed.
When a block is split with `RewriterBase::splitBlock`, a
`notifyBlockInserted` notification, followed by
`notifyOperationInserted` notifications (for moving over the operations
into the new block) should be sent. This commit adds those
notifications.
When a block is inlined into another block, the nested operations are
moved into another block and the `notifyOperationInserted` callback
should be triggered. This commit adds the missing notifications for:
* `RewriterBase::inlineBlockBefore`
* `RewriterBase::mergeBlocks`
This commit adds a new method to the rewriter API: `moveBlockBefore`.
This op is utilized by `inlineRegionBefore` and covered by dialect
conversion test cases.
Also fixes a bug in `moveOpBefore`, where the previous op location was
not passed correctly. Adds a test case to
`test-strict-pattern-driver.mlir`.
The pattern rewriter documentation states that "*all* IR mutations [...]
are required to be performed via the `PatternRewriter`." This commit
adds two functions that were missing from the rewriter API:
`moveOpBefore` and `moveOpAfter`.
After an operation was moved, the `notifyOperationInserted` callback is
triggered. This allows listeners such as the greedy pattern rewrite
driver to react to IR changes.
This commit narrows the discrepancy between the kind of IR modification
that can be performed and the kind of IR modifications that can be
listened to.
This commit renames 4 pattern rewriter API functions:
* `updateRootInPlace` -> `modifyOpInPlace`
* `startRootUpdate` -> `startOpModification`
* `finalizeRootUpdate` -> `finalizeOpModification`
* `cancelRootUpdate` -> `cancelOpModification`
The term "root" is a misnomer. The root is the op that a rewrite pattern
matches against
(https://mlir.llvm.org/docs/PatternRewriter/#root-operation-name-optional).
A rewriter must be notified of all in-place op modifications, not just
in-place modifications of the root
(https://mlir.llvm.org/docs/PatternRewriter/#pattern-rewriter). The old
function names were confusing and have contributed to various broken
rewrite patterns.
Note: The new function names use the term "modify" instead of "update"
for consistency with the `RewriterBase::Listener` terminology
(`notifyOperationModified`).
