This revision takes the forward value propagation engine in SCCP and refactors it into a more generalized forward dataflow analysis framework. This framework allows for propagating information about values across the various control flow constructs in MLIR, and removes the need for users to reinvent the traversal (often not as completely). There are a few aspects of the traversal, that were conservative for SCCP, that should be relaxed to support the needs of different value analyses. To keep this revision simple, these conservative behaviors will be left in (Note that this won't produce an incorrect result, but may produce more conservative results than necessary in certain edge cases. e.g. region entry arguments for non-region branch interface operations). The framework also only focuses on computing lattices for values, given the SCCP origins, but this is something to relax as needed in the future.
Given that this logic is already in SCCP, a majority of this commit is NFC. The more interesting parts are the interface glue that clients interact with.
Differential Revision: https://reviews.llvm.org/D100915
These properties were useful for a few things before traits had a better integration story, but don't really carry their weight well these days. Most of these properties are already checked via traits in most of the code. It is better to align the system around traits, and improve the performance/cost of traits in general.
Differential Revision: https://reviews.llvm.org/D96088
This makes ignoring a result explicit by the user, and helps to prevent accidental errors with dropped results. Marking LogicalResult as no discard was always the intention from the beginning, but got lost along the way.
Differential Revision: https://reviews.llvm.org/D95841
This class used to serve a few useful purposes:
* Allowed containing a null DictionaryAttr
* Provided some simple mutable API around a DictionaryAttr
The first of which is no longer an issue now that there is much better caching support for attributes in general, and a cache in the context for empty dictionaries. The second results in more trouble than it's worth because it mutates the internal dictionary on every action, leading to a potentially large number of dictionary copies. NamedAttrList is a much better alternative for the second use case, and should be modified as needed to better fit it's usage as a DictionaryAttrBuilder.
Differential Revision: https://reviews.llvm.org/D93442
This fixes a subtle bug where SCCP could incorrectly optimize a private callable while waiting for its arguments to be resolved.
Fixes PR#48457
Differential Revision: https://reviews.llvm.org/D92976
Given that OpState already implicit converts to Operator*, this seems reasonable.
The alternative would be to add more functions to OpState which forward to Operation.
Reviewed By: rriddle, ftynse
Differential Revision: https://reviews.llvm.org/D92266
This transforms the symbol lookups to O(1) from O(NM), greatly speeding up both passes. For a large MLIR module this shaved seconds off of the compilation time.
Differential Revision: https://reviews.llvm.org/D89522
- Arguments of the first block of a region are considered region arguments.
- Add API on Region class to deal with these arguments directly instead of
using the front() block.
- Changed several instances of existing code that can use this API
- Fixes https://bugs.llvm.org/show_bug.cgi?id=46535
Differential Revision: https://reviews.llvm.org/D83599
Makes the relationship and function clearer. Accordingly rename getAttrList to getMutableAttrDict.
Differential Revision: https://reviews.llvm.org/D79125
This revision adds support for propagating constants across symbol-based callgraph edges. It uses the existing Call/CallableOpInterfaces to detect the dataflow edges, and propagates constants through arguments and out of returns.
Differential Revision: https://reviews.llvm.org/D78592
This is possible by adding two new ControlFlowInterface additions:
- A new interface, RegionBranchOpInterface
This interface allows for region holding operations to describe how control flows between regions. This interface initially contains two methods:
* getSuccessorEntryOperands
Returns the operands of this operation used as the entry arguments when entering the region at `index`, which was specified as a successor by `getSuccessorRegions`. when entering. These operands should correspond 1-1 with the successor inputs specified in `getSuccessorRegions`, and may be a subset of the entry arguments for that region.
* getSuccessorRegions
Returns the viable successors of a region, or the possible successor when branching from the parent op. This allows for describing which regions may be executed when entering an operation, and which regions are executed after having executed another region of the parent op. For example, a structured loop operation may always enter into the loop body region. The loop body region may branch back to itself, or exit to the operation.
- A trait, ReturnLike
This trait signals that a terminator exits a region and forwards all of its operands as "exiting" values.
These additions allow for performing more general dataflow analysis in the presence of region holding operations.
Differential Revision: https://reviews.llvm.org/D78447
This revision adds the initial pass for performing SCCP generically in MLIR. SCCP is an algorithm for propagating constants across control flow, and optimistically assumes all values to be constant unless proven otherwise. It currently supports branching control, with support for regions and inter-procedural propagation being added in followups.
Differential Revision: https://reviews.llvm.org/D78397
Mehdi Amini