[all-commits] [llvm/llvm-project] d4c41b: [mlir][Transforms] Dialect Conversion: Convert ent...

[Matthias Springer via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d4c41b7fa30be06b5250c0d5abc7a26a83420321
      https://github.com/llvm/llvm-project/commit/d4c41b7fa30be06b5250c0d5abc7a26a83420321
  Author: Matthias Springer <me at m-sp.org>
  Date:   2025-11-03 (Mon, 03 Nov 2025)

  Changed paths:
    M mlir/lib/Transforms/Utils/DialectConversion.cpp
    A mlir/test/Transforms/test-legalizer-no-materializations.mlir
    M mlir/test/Transforms/test-legalizer.mlir
    M mlir/test/lib/Dialect/Test/TestPatterns.cpp

  Log Message:
  -----------
  [mlir][Transforms] Dialect Conversion: Convert entry block only (#165180)

When converting a function, convert only the entry block signature. The
remaining block signatures should be converted by the respective
branching ops. The `FuncToLLVM` / `ControlFlowToLLVM` patterns already
use that design.

```c++
struct BranchOpLowering : public ConvertOpToLLVMPattern<cf::BranchOp> {

  LogicalResult
  matchAndRewrite(cf::BranchOp op, OneToNOpAdaptor adaptor,
                  ConversionPatternRewriter &rewriter) const override {
    // Convert successor block.
    SmallVector<Value> flattenedAdaptor = flattenValues(adaptor.getOperands());
    FailureOr<Block *> convertedBlock =
        getConvertedBlock(rewriter, getTypeConverter(), op, op.getSuccessor(),
                          TypeRange(ValueRange(flattenedAdaptor)));
    // ...
  }
};
```

This is consistent with the fact that operations from unreachable blocks
are not put on the initial worklist.

With this change, parent ops are no longer recursively legalized when
inserting a block, simplifying the conversion driver a bit.

Note for LLVM integration: If you are seeing failures, make sure to:
- Drop `converter.isLegal(&op.getBody())` when checking the legality of
a function op. Only the entry block signature / function type should be
taken into account.
- If you need to convert all reachable blocks and are using `cf`
branching ops, add `populateCFStructuralTypeConversionsAndLegality`.
- If you need to convert all reachable blocks and are using custom
branching ops, implement and populate custom structural type conversion
patterns, similar to `populateCFStructuralTypeConversionsAndLegality`.



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