* Strip calls to raw_string_ostream::flush(), which is essentially a no-op
* Strip unneeded calls to raw_string_ostream::str(), to avoid excess indirection.
The dialect conversion maintains a set of unresolved materializations
(`UnrealizedConversionCastOp`). Turn that set into a `DenseMap` that
maps from ops to `UnresolvedMaterializationRewrite *`. This improves
efficiency a bit, because an iteration over
`ConversionPatternRewriterImpl::rewrites` can be avoided.
Also delete some dead code.
Handle dropped block arguments and dropped op results in the same way:
build a source materialization (that may fold away if unused). This
simplifies the code base a bit and makes it possible to merge
`legalizeConvertedArgumentTypes` and `legalizeConvertedOpResultTypes` in
a future commit. These two functions are almost doing the same thing
now.
As a side effect, this commit also changes the dialect conversion such
that temporary circular cast ops are no longer generated. (There was a
workaround in #107109 that can now be removed again.) Example:
```
%0 = "builtin.unrealized_conversion_cast"(%1) : (!a) -> !b
%1 = "builtin.unrealized_conversion_cast"(%0) : (!b) -> !a
// No further uses of %0, %1.
```
This happened when:
1. An op was erased. (No replacement values provided.)
2. A conversion pattern for another op builds a replacement value for
the erased op's results (first cast op) during `remapValues`, but that
SSA value is not used during the pattern application.
3. During the finalization phase, `legalizeConvertedOpResultTypes`
thinks that the erased op is alive because of the cast op that was built
in Step 2. It builds a cast from that replacement value to the original
type.
4. During the commit phase, all uses of the original op are replaced
with the casted value produced in Step 3. We have generated circular IR.
This problem can be avoided by making sure that source materializations
are generated for all dropped results. This ensures that we always have
some replacement SSA value in the mapping. Previously, we sometimes had
a value mapped and sometimes not. (No more special casing is needed
anymore to distinguish between "value dropped" or "value replaced with
SSA 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 fixes#94520 by ensuring that any if any block arguments are being
used outside of the original block that the block is not considered a
candidate for merging.
More details: the root cause of the issue described in #94520 was that
`^bb2` and `^bb5` were being merged despite `%4` (an argument to `^bb2`)
was being used later in `^bb7`. When the block merge occurred, that
unintentionally changed the value of `%4` for all downstream code. This
change prevents that from happening.
This patch deprecates DenseMap::getOrInsertDefault in favor of
DenseMap::operator[], which does the same thing, has been around
longer, and is also a household name as part of std::map and
std::unordered_map.
Note that DenseMap provides several equivalent ways to insert or
default-construct a key-value pair:
- operator[Key]
- try_emplace(Key).first->second
- getOrInsertDefault(Key)
- FindAndConstruct(Key).second
There was a redundant `appendRewrite<ReplaceBlockArgRewrite>(block,
origArg);` in `ConversionPatternRewriterImpl::applySignatureConversion`
that had no effect.
This commit changes the inlining to also update the locations of block
arguments. Not updating these locations leads to LLVM IR verification
issues when exporting converted block arguments to phi nodes. This lack
of location update was not visible due to ignoring the argument
locations until recently.
Relevant change: https://github.com/llvm/llvm-project/pull/105534
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.)
Move the implementation of `ReconcileUnrealizedCasts` to
`DialectConversion.cpp`, so that it can be called from there in a future
commit.
This commit is in preparation of decoupling argument/source/target
materializations from the dialect conversion framework. The existing
logic around unresolved materializations that predicts IR changes to
decide if a cast op can be folded/erased will become obsolete, as
`ReconcileUnrealizedCasts` will perform these kind of foldings on fully
materialized IR.
---------
Co-authored-by: Markus Böck <markus.boeck02@gmail.com>
Mem2Reg assumes SSA dependencies but did not check for graph regions.
This fixes it.
---------
Co-authored-by: Christian Ulmann <christianulmann@gmail.com>
There was a typo in the code path that removes unnecessary
materializations.
Before: Update `opResult` (result of an op different from `user`) in
mapping and remove `user`.
```
replaceMaterialization(rewriterImpl, opResult, inputOperands,
inverseMapping);
necessaryMaterializations.remove(materializationOps.lookup(user));
```
After: Update `user->getResults()` in mapping and remove `user`.
```
replaceMaterialization(rewriterImpl, user->getResults(), inputOperands,
inverseMapping);
necessaryMaterializations.remove(materializationOps.lookup(user));
```
When inserting an argument/source/target materialization, the dialect
conversion framework first inserts a "dummy"
`unrealized_conversion_cast` op (during the rewrite process) and then
(in the "finialize" phase) replaces these cast ops with the IR generated
by the type converter callback.
This is the case for all materializations, except when ops are being
replaced with values that have a different type. In that case, the
dialect conversion currently directly emits a source materialization.
This commit changes the implementation, such that a temporary
`unrealized_conversion_cast` is also inserted in that case.
This commit simplifies the code base: all materializations now happen in
`legalizeUnresolvedMaterialization`. This commit makes it possible to
decouple source/target/argument materializations from the dialect
conversion (to reduce the complexity of the code base). Such
materializations can then also be optional. This will be implemented in
a follow-up commit.
Depends on #101476.
---------
Co-authored-by: Jakub Kuderski <jakub@nod-labs.com>
The "inverse mapping" is an inverse IRMapping that points from replaced
values to their original values. This inverse mapping is needed when
legalizing unresolved materializations, to figure out if a value has any
uses. (It is not sufficient to examine the IR, because some IR changes
have not been materialized yet.)
There was a check in `OperationConverter::finalize` that computed the
inverse mapping only when needed. This check is not needed.
`legalizeUnresolvedMaterializations` always computes the inverse
mapping, so we can just do that in `OperationConverter::finalize` before
calling `legalizeUnresolvedMaterializations`.
Depends on #98805
With this PR I am trying to address:
https://github.com/llvm/llvm-project/issues/63230.
What changed:
- While merging identical blocks, don't add a block argument if it is
"identical" to another block argument. I.e., if the two block arguments
refer to the same `Value`. The operations operands in the block will
point to the argument we already inserted. This needs to happen to all
the arguments we pass to the different successors of the parent block
- After merged the blocks, get rid of "unnecessary" arguments. I.e., if
all the predecessors pass the same block argument, there is no need to
pass it as an argument.
- This last simplification clashed with
`BufferDeallocationSimplification`. The reason, I think, is that the two
simplifications are clashing. I.e., `BufferDeallocationSimplification`
contains an analysis based on the block structure. If we simplify the
block structure (by merging and/or dropping block arguments) the
analysis is invalid . The solution I found is to do a more prudent
simplification when running that pass.
**Note-1**: I ran all the integration tests
(`-DMLIR_INCLUDE_INTEGRATION_TESTS=ON`) and they passed.
**Note-2**: I fixed a bug found by @Dinistro in #97697 . The issue was
that, when looking for redundant arguments, I was not considering that
the block might have already some arguments. So the index (in the block
args list) of the i-th `newArgument` is `i+numOfOldArguments`.
This commit moves the argument materialization logic from
`legalizeConvertedArgumentTypes` to
`legalizeUnresolvedMaterializations`.
Before this change:
- Argument materializations were created in
`legalizeConvertedArgumentTypes` (which used to call
`materializeLiveConversions`).
After this change:
- `legalizeConvertedArgumentTypes` creates a "placeholder"
`unrealized_conversion_cast`.
- The placeholder `unrealized_conversion_cast` is replaced with an
argument materialization (using the type converter) in
`legalizeUnresolvedMaterializations`.
- All argument and target materializations now take place in the same
location (`legalizeUnresolvedMaterializations`).
This commit brings us closer towards creating all source/target/argument
materializations in one central step, which can then be made optional
(and delegated to the user) in the future. (There is one more source
materialization step that has not been moved yet.)
This commit also consolidates all `build*UnresolvedMaterialization`
functions into a single `buildUnresolvedMaterialization` function.
This is a re-upload of #96329.
This reverts commit 2aa96fcf75.
This was merged without a test. Also it seems it was only fixing an
issue for users which used a particular workaround that is not actually
needed anymore (skipping UnrealizedConversionCast operands).
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 the handling of dropped arguments and updates
some dialect conversion documentation that is outdated.
When converting a block signature, a `BlockTypeConversionRewrite` object
and potentially multiple `ReplaceBlockArgRewrite` are created. During
the "commit" phase, uses of the old block arguments are replaced with
the new block arguments, but the old implementation was written in an
inconsistent way: some block arguments were replaced in
`BlockTypeConversionRewrite::commit` and some were replaced in
`ReplaceBlockArgRewrite::commit`. The new
`BlockTypeConversionRewrite::commit` implementation is much simpler and
no longer modifies any IR; that is done only in `ReplaceBlockArgRewrite`
now. The `ConvertedArgInfo` data structure is no longer needed.
To that end, materializations of dropped arguments are now built in
`applySignatureConversion` instead of `materializeLiveConversions`; the
latter function no longer has to deal with dropped arguments.
Other minor improvements:
- Add more comments to `applySignatureConversion`.
Note: Error messages around failed materializations for dropped basic
block arguments changed slightly. That is because those materializations
are now built in `legalizeUnresolvedMaterialization` instead of
`legalizeConvertedArgumentTypes`.
This commit is in preparation of decoupling argument/source/target
materializations from the dialect conversion.
This is a re-upload of #96207.
With this PR I am trying to address:
https://github.com/llvm/llvm-project/issues/63230.
What changed:
- While merging identical blocks, don't add a block argument if it is
"identical" to another block argument. I.e., if the two block arguments
refer to the same `Value`. The operations operands in the block will
point to the argument we already inserted. This needs to happen to all
the arguments we pass to the different successors of the parent block
- After merged the blocks, get rid of "unnecessary" arguments. I.e., if
all the predecessors pass the same block argument, there is no need to
pass it as an argument.
- This last simplification clashed with
`BufferDeallocationSimplification`. The reason, I think, is that the two
simplifications are clashing. I.e., `BufferDeallocationSimplification`
contains an analysis based on the block structure. If we simplify the
block structure (by merging and/or dropping block arguments) the
analysis is invalid . The solution I found is to do a more prudent
simplification when running that pass.
**Note**: this a rework of #96871 . I ran all the integration tests
(`-DMLIR_INCLUDE_INTEGRATION_TESTS=ON`) and they passed.
This commit fixes a bug in the dialect conversion. During a 1:N
signature conversion, the dialect conversion did not insert a cast back
to the original block argument type, producing invalid IR.
See `test-block-legalization.mlir`: Without this commit, the operand
type of the op changes because an `unrealized_conversion_cast` is
missing:
```
"test.consumer_of_complex"(%v) : (!llvm.struct<(f64, f64)>) -> ()
```
To implement this fix, it was necessary to change the meaning of
argument materializations. An argument materialization now maps from the
new block argument types to the original block argument type. (It now
behaves almost like a source materialization.) This also addresses a
`FIXME` in the code base:
```
// FIXME: The current argument materialization hook expects the original
// output type, even though it doesn't use that as the actual output type
// of the generated IR. The output type is just used as an indicator of
// the type of materialization to do. This behavior is really awkward in
// that it diverges from the behavior of the other hooks, and can be
// easily misunderstood. We should clean up the argument hooks to better
// represent the desired invariants we actually care about.
```
It is no longer necessary to distinguish between the "output type" and
the "original output type".
Most type converter are already written according to the new API. (Most
implementations use the same conversion functions as for source
materializations.) One exception is the MemRef-to-LLVM type converter,
which materialized an `!llvm.struct` based on the elements of a memref
descriptor. It still does that, but casts the `!llvm.struct` back to the
original memref type. The dialect conversion inserts a target
materialization (to `!llvm.struct`) which cancels out with the other
cast.
This commit also fixes a bug in `computeNecessaryMaterializations`. The
implementation did not account for the possibility that a value was
replaced multiple times. E.g., replace `a` by `b`, then `b` by `c`.
This commit also adds a transform dialect op to populate SCF-to-CF
patterns. This transform op was needed to write a test case. The bug
described here appears only during a complex interplay of 1:N signature
conversions and op replacements. (I was not able to trigger it with ops
and patterns from the `test` dialect without duplicating the `scf.if`
pattern.)
Note for LLVM integration: Make sure that all
`addArgument/Source/TargetMaterialization` functions produce an SSA of
the specified type.
Depends on #98743.
With this PR I am trying to address:
https://github.com/llvm/llvm-project/issues/63230.
What changed:
- While merging identical blocks, don't add a block argument if it is
"identical" to another block argument. I.e., if the two block arguments
refer to the same `Value`. The operations operands in the block will
point to the argument we already inserted
- After merged the blocks, get rid of "unnecessary" arguments. I.e., if
all the predecessors pass the same block argument, there is no need to
pass it as an argument.
- This last simplification clashed with
`BufferDeallocationSimplification`. The reason, I think, is that the two
simplifications are clashing. I.e., `BufferDeallocationSimplification`
contains an analysis based on the block structure. If we simplify the
block structure (by merging and/or dropping block arguments) the
analysis is invalid . The solution I found is to do a more prudent
simplification when running that pass.
**Note**: many tests are still not passing. But I wanted to submit the
code before changing all the tests (and probably adding a couple), so
that we can agree in principle on the algorithm/design.
The `elementPtrs` has changed meaning over time and the name is now
outdated which may be confusing. This PR updates it to a name
representative of current usage.
This commit moves the argument materialization logic from
`legalizeConvertedArgumentTypes` to
`legalizeUnresolvedMaterializations`.
Before this change:
- Argument materializations were created in
`legalizeConvertedArgumentTypes` (which used to call
`materializeLiveConversions`).
After this change:
- `legalizeConvertedArgumentTypes` creates a "placeholder"
`unrealized_conversion_cast`.
- The placeholder `unrealized_conversion_cast` is replaced with an
argument materialization (using the type converter) in
`legalizeUnresolvedMaterializations`.
- All argument and target materializations now take place in the same
location (`legalizeUnresolvedMaterializations`).
This commit brings us closer towards creating all source/target/argument
materializations in one central step, which can then be made optional
(and delegated to the user) in the future. (There is one more source
materialization step that has not been moved yet.)
This commit also consolidates all `build*UnresolvedMaterialization`
functions into a single `buildUnresolvedMaterialization` function.
This commit simplifies the handling of dropped arguments and updates
some dialect conversion documentation that is outdated.
When converting a block signature, a `BlockTypeConversionRewrite` object
and potentially multiple `ReplaceBlockArgRewrite` are created. During
the "commit" phase, uses of the old block arguments are replaced with
the new block arguments, but the old implementation was written in an
inconsistent way: some block arguments were replaced in
`BlockTypeConversionRewrite::commit` and some were replaced in
`ReplaceBlockArgRewrite::commit`. The new
`BlockTypeConversionRewrite::commit` implementation is much simpler and
no longer modifies any IR; that is done only in `ReplaceBlockArgRewrite`
now. The `ConvertedArgInfo` data structure is no longer needed.
To that end, materializations of dropped arguments are now built in
`applySignatureConversion` instead of `materializeLiveConversions`; the
latter function no longer has to deal with dropped arguments.
Other minor improvements:
- Improve variable name: `origOutputType` -> `origArgType`. Add an
assertion to check that this field is only used for argument
materializations.
- Add more comments to `applySignatureConversion`.
Note: Error messages around failed materializations for dropped basic
block arguments changed slightly. That is because those materializations
are now built in `legalizeUnresolvedMaterialization` instead of
`legalizeConvertedArgumentTypes`.
This commit is in preparation of decoupling argument/source/target
materializations from the dialect conversion.
This commit removes a `FIXME` in the code base that was in place because
of patterns that used the dialect conversion API incorrectly. Those
patterns have been fixed and the workaround is no longer needed.
Remove a TODO in the dialect conversion code base when materializing
unresolved conversions:
```
// FIXME: Determine a suitable insertion location when there are multiple
// inputs.
```
The implementation used to select an insertion point as follows:
- If the cast has exactly one operand: right after the definition of the
SSA value.
- Otherwise: right before the cast op.
However, it is not necessary to change the insertion point. Unresolved
materializations (`UnrealizedConversionCastOp`) are built during
`buildUnresolvedArgumentMaterialization` or
`buildUnresolvedTargetMaterialization`. In the former case, the op is
inserted at the beginning of the block. In the latter case, only one
operand is supported in the dialect conversion, and the op is inserted
right after the definition of the SSA value. I.e., the
`UnrealizedConversionCastOp` is already inserted at the right place and
it is not necessary to change the insertion point for the resolved
materialization op.
Note: The IR change changes slightly because the
`unrealized_conversion_cast` ops at the beginning of a block are no
longer doubly-inverted (by setting the insertion to the beginning of the
block when inserting the `unrealized_conversion_cast` and again when
inserting the resolved conversion op). All affected test cases were
fixed by using `CHECK-DAG` instead of `CHECK`.
Also improve the quality of multiple test cases that did not check for
the correct operands.
Note: This commit is in preparation of decoupling the
argument/source/target materialization logic of the type converter from
the dialect conversion (to reduce its complexity and make that
functionality usable from a new dialect conversion driver).
This is a heavy process, and it can trigger a massive explosion in
adding block arguments. While potentially reducing the code size, the
resulting merged blocks with arguments are hiding some of the def-use
chain and can even hinder some further analyses/optimizations: a merge
block does not have it's own path-sensitive context, instead the context
is merged from all the predecessors.
Previous behavior can be restored by passing:
{test-convergence region-simplify=aggressive}
to the canonicalize pass.
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 simplifies the design of the `GreedyPatternRewriterDriver`
class. This class used to inherit from both `PatternRewriter` and
`RewriterBase::Listener` and then attached itself as a listener.
In the new design, the class has a `PatternRewriter` field instead of
inheriting from `PatternRewriter`, which is generally perferred in
object-oriented programming.
---------
Co-authored-by: Markus Böck <markus.boeck02@gmail.com>
This PR attempts to consolidate the different topological sort utilities
into one place. It adds them to the analysis folder because the
`SliceAnalysis` uses some of these.
There are now two different sorting strategies:
1. Sort only according to SSA use-def chains
2. Sort while taking regions into account. This requires a much more
elaborate traversal and cannot be applied on graph regions that easily.
This additionally reimplements the region aware topological sorting
because the previous implementation had an exponential space complexity.
I'm open to suggestions on how to combine this further or how to fuse
the test passes.
