This cl enforces that the conversion of the type signatures for regions, and thus their entry blocks, is handled via ConversionPatterns. A new hook 'applySignatureConversion' is added to the ConversionPatternRewriter to perform the desired conversion on a region. This also means that the handling of rewriting the signature of a FuncOp is moved to a pattern. A default implementation is provided via 'mlir::populateFuncOpTypeConversionPattern'. This removes the hacky implicit 'dynamically legal' status of FuncOp that was present previously, and leaves it up to the user to decide when/how to convert the signature of a function.
PiperOrigin-RevId: 259161999
This allows for providing specific handling for dynamically legal operations/dialects without overriding the general 'isDynamicallyLegal' hook. This also means that a derived ConversionTarget class need not always be defined when some operations are dynamically legal.
Example usage:
ConversionTarget target(...);
target.addDynamicallyLegalOp<ReturnOp>([](ReturnOp op) {
return ...
};
target.addDynamicallyLegalDialect<StandardOpsDialect>([](Operation *op) {
return ...
};
PiperOrigin-RevId: 258884753
This specific PatternRewriter will allow for exposing hooks in the future that are only useful for the conversion framework, e.g. type conversions.
PiperOrigin-RevId: 258818122
This cl begins a large refactoring over how signature types are converted in the DialectConversion infrastructure. The signatures of blocks are now converted on-demand when an operation held by that block is being converted. This allows for handling the case where a region is created as part of a pattern, something that wasn't possible previously.
This cl also generalizes the region signature conversion used by FuncOp to work on any region of any operation. This generalization allows for removing the 'apply*Conversion' functions that were specific to FuncOp/ModuleOp. The implementation currently uses a new hook on TypeConverter, 'convertRegionSignature', but this should ideally be removed in favor of using Patterns. That depends on adding support to the PatternRewriter used by ConversionPattern to allow applying signature conversions to regions, which should be coming in a followup.
PiperOrigin-RevId: 258645733
This explicit tag is useful is several ways:
*) This simplifies how to mark sub sections of a dialect as explicitly unsupported, e.g. my target supports all operations in the foo dialect except for these select few. This is useful for partial lowerings between dialects.
*) Partial conversions will now verify that operations that were explicitly marked as illegal must be converted. This provides some guarantee that the operations that need to be lowered by a specific pass will be.
PiperOrigin-RevId: 258582879
Users generally want several different modes of conversion. This cl refactors DialectConversion to provide two:
* Partial (applyPartialConversion)
- This mode allows for illegal operations to exist in the IR, and does not fail if an operation fails to be legalized.
* Full (applyFullConversion)
- This mode fails if any operation is not properly legalized to the conversion target. This allows for ensuring that the IR after a conversion only contains operations legal for the target.
PiperOrigin-RevId: 258412243
This cl changes the way that operations/blocks to convert are collected/traversed so that parent region operations can be legalized before their bodies. Most RewritePatterns for region operations assume that the entry arguments to each region are yet to be converted. Given that the bodies are currently converted first, this makes it difficult to fit these patterns into the same run as one converting types.
The operations/blocks to convert are now collected before any legalization has run, which simplifies the conversion logic itself, as legalization may insert new operations, move blocks, etc.
PiperOrigin-RevId: 258170158
When using a RewritePattern and replacing an operation with an existing value, that value may have already been replaced by something else. This cl ensures that only the final value is used when applying rewrites.
PiperOrigin-RevId: 258058488
Modules can now contain more than just Functions, this just updates the iteration API to reflect that. The 'begin'/'end' methods have also been updated to iterate over opaque Operations.
PiperOrigin-RevId: 257099084
As with Functions, Module will soon become an operation, which are value-typed. This eases the transition from Module to ModuleOp. A new class, OwningModuleRef is provided to allow for owning a reference to a Module, and will auto-delete the held module on destruction.
PiperOrigin-RevId: 256196193
Move the data members out of Function and into a new impl storage class 'FunctionStorage'. This allows for Function to become value typed, which will greatly simplify the transition of Function to FuncOp(given that FuncOp is also value typed).
PiperOrigin-RevId: 255983022
Type conversion does not necessarily affect all types, some of them may remain
untouched. The type conversion tool from the dialect conversion framework will
unconditionally insert a temporary cast operation from the type to itself
anyway, and will try to materialize it to a real conversion operation if there
are remaining uses. Simply use the original value instead.
PiperOrigin-RevId: 255975450
During conversion, if a type conversion has dangling uses a type conversion must persist after conversion has finished to maintain valid IR. In these cases, we now query the TypeConverter to materialize a conversion for us. This allows for the default case of a full conversion to continue working as expected, but also handle the degenerate cases more robustly.
PiperOrigin-RevId: 255637171
Now that Locations are attributes, they have direct access to the MLIR context. This allows for simplifying error emission by removing unnecessary context lookups.
PiperOrigin-RevId: 255112791
* Support for 1->0 type mappings, i.e. when the argument is being removed.
* Reordering types when converting a type signature.
* Adding new inputs when converting a type signature.
This cl also lays down the initial foundation for supporting 1->N type mappings, but full support will come in a followup.
Moving forward, function signature changes will be driven by populating a SignatureConversion instance. This class contains all of the necessary information for adding/removing/remapping function signatures; e.g. addInputs, addResults, remapInputs, etc.
PiperOrigin-RevId: 254064665
1) Lowest minimum pattern stack depth when legalizing.
- This leads the system to favor patterns that have lower legalization stacks, i.e. represent a more direct mapping to the target.
2) Pattern benefit.
- When considering multiple patterns with the same legalization depth, this favors patterns with a larger specified benefit.
PiperOrigin-RevId: 252713470
This introduces the support for region-containing operations to the dialect
conversion framework in order to support the conversion of affine control-flow
operations into the standard control flow with branches. Regions that belong
to an operation are converted before the operation itself. The
DialectConversionPattern can therefore access the converted regions of the
original operation and process them further if necessary. In particular, the
conversion is allowed to move the blocks from the original region to other
regions and to split blocks into multiple blocks. All block manipulations must
be performed through the PatternRewriter to ensure they will be undone if the
conversion fails.
Port the pass converting from the affine dialect (loops and ifs with bodies as
regions) to the standard dialect (branch-based cfg) to use DialectConversion in
order to exercise this new functionality. The modification to the lowering
functions are minor and are focused on using the PatterRewriter instead of
directly modifying the IR.
PiperOrigin-RevId: 252625169
- added a typed walk to Block (matching the equivalent on Function)
- added token parsers (incl optional variants) for : and (
- added applyConversionPatterns that takes a list of functions to apply patterns to
PiperOrigin-RevId: 251481608
To accomplish this, moving forward users will need to provide a legalization target that defines what operations are legal for the conversion. A target can mark an operation as legal by providing a specific legalization action. The initial actions are:
* Legal
- This action signals that every instance of the given operation is legal,
i.e. any combination of attributes, operands, types, etc. is valid.
* Dynamic
- This action signals that only some instances of a given operation are legal. This
allows for defining fine-tune constraints, like say std.add is only legal when
operating on 32-bit integers.
An example target is shown below:
struct MyTarget : public ConversionTarget {
MyTarget(MLIRContext &ctx) : ConversionTarget(ctx) {
// All operations in the LLVM dialect are legal.
addLegalDialect<LLVMDialect>();
// std.constant op is always legal on this target.
addLegalOp<ConstantOp>();
// std.return op has dynamic legality constraints.
addDynamicallyLegalOp<ReturnOp>();
}
/// Implement the custom legalization handler to handle
/// std.return.
bool isLegal(Operation *op) override {
// Process the dynamic handling for a std.return op (and any others that were
// marked "dynamic").
...
}
};
PiperOrigin-RevId: 251289374
Originally, FunctionConverter::convertRegion in the DialectConversion framework
was implemented as a function template because it was creating a new region in
the parent object, which could have been an op or a function. Since
DialectConversion now operates in place, new region is no longer created so
there is no need for convertRegion to be aware of the parent, only of the error
reporting location.
--
PiperOrigin-RevId: 249826392
The converter now works by inserting fake producer operations when replacing the results of an existing operation with values of a different, now legal, type. These fake operations are guaranteed to never escape the converter.
--
PiperOrigin-RevId: 248969130
Dialect conversion currently clones the operations that did not match any
pattern. This includes cloning any regions that belong to these operations.
Instead, apply conversion recursively to the nested regions.
Note that if an operation matched one of the conversion patterns, it is up to
the pattern rewriter to fill in the regions of the converted operation. This
may require calling back to the converter and is left for future work.
PiperOrigin-RevId: 240872410
This fixes a bug: previously, during conversion function argument
attributes were neither beings passed through nor converted. This fix
extends DialectConversion to allow for simultaneous conversion of the
function type and the argument attributes.
This was important when lowering MLIR to LLVM where attribute
information (e.g. noalias) needs to be preserved in MLIR(LLVMDialect).
Longer run it seems reasonable that we want to convert both the
function attribute and its type and the argument attributes, but that
requires a small refactoring in Function.h to aggregate these three
fields in an inner struct, which will require some discussion.
PiperOrigin-RevId: 236709409
Function types are built-in in MLIR and affect the validity of the IR itself.
However, advanced target dialects such as the LLVM IR dialect may include
custom function types. Until now, dialect conversion was expecting function
types not to be converted to the custom type: although the signatures was
allowed to change, the outer type must have been an mlir::FunctionType. This
effectively prevented dialect conversion from creating instructions that
operate on values of the custom function type.
Dissociate function signature conversion from general type conversion.
Function signature conversion must still produce an mlir::FunctionType and is
used in places where built-in types are required to make IR valid. General
type conversion is used for SSA values, including function and block arguments
and function results.
Exercise this behavior in the LLVM IR dialect conversion by converting function
types to LLVM IR function pointer types. The pointer to a function is chosen
to provide consistent lowering of higher-order functions: while it is possible
to have a value of function type, it is not possible to create a function type
accepting a returning another function type.
PiperOrigin-RevId: 234124494
This commit introduces a generic dialect conversion/lowering/legalization pass
and illustrates it on StandardOps->LLVMIR conversion.
It partially reuses the PatternRewriter infrastructure and adds the following
functionality:
- an actual pass;
- non-default pattern constructors;
- one-to-many rewrites;
- rewriting terminators with successors;
- not applying patterns iteratively (unlike the existing greedy rewrite driver);
- ability to change function signature;
- ability to change basic block argument types.
The latter two things required, given the existing API, to create new functions
in the same module. Eventually, this should converge with the rest of
PatternRewriter. However, we may want to keep two pass versions: "heavy" with
function/block argument conversion and "light" that only touches operations.
This pass creates new functions within a module as a means to change function
signature, then creates new blocks with converted argument types in the new
function. Then, it traverses the CFG in DFS-preorder to make sure defs are
converted before uses in the dominated blocks. The generic pass has a minimal
interface with two hooks: one to fill in the set of patterns, and another one
to convert types for functions and blocks. The patterns are defined as
separate classes that can be table-generated in the future.
The LLVM IR lowering pass partially inherits from the existing LLVM IR
translator, in particular for type conversion. It defines a conversion pattern
template, instantiated for different operations, and is a good candidate for
tablegen. The lowering does not yet support loads and stores and is not
connected to the translator as it would have broken the existing flows. Future
patches will add missing support before switching the translator in a single
patch.
PiperOrigin-RevId: 230951202
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