[Mlir-commits] [mlir] [mlir][SCFToOpenMP] Use walk pattern driver (PR #155242)

[Matthias Springer]

https://github.com/matthias-springer created https://github.com/llvm/llvm-project/pull/155242

The lowering pattern uses various APIs that are not supported in a dialect conversion such as `Block::eraseArguments` and `RewriterBase::replaceAllUsesWith`. Switch to the more efficient and simpler walk pattern driver.


>From 5205679a2dd81ed85328e470eb53dc44abc85a8c Mon Sep 17 00:00:00 2001
From: Matthias Springer <me at m-sp.org>
Date: Mon, 25 Aug 2025 13:27:12 +0000
Subject: [PATCH] [mlir][SCFToOpenMP] Use walk pattern driver

---
 mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp b/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp
index 34f372af1e4b5..c903016611422 100644
--- a/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp
+++ b/mlir/lib/Conversion/SCFToOpenMP/SCFToOpenMP.cpp
@@ -22,7 +22,7 @@
 #include "mlir/Dialect/SCF/IR/SCF.h"
 #include "mlir/IR/SymbolTable.h"
 #include "mlir/Pass/Pass.h"
-#include "mlir/Transforms/DialectConversion.h"
+#include "mlir/Transforms/WalkPatternRewriteDriver.h"
 
 namespace mlir {
 #define GEN_PASS_DEF_CONVERTSCFTOOPENMPPASS
@@ -538,15 +538,16 @@ struct ParallelOpLowering : public OpRewritePattern<scf::ParallelOp> {
 
 /// Applies the conversion patterns in the given function.
 static LogicalResult applyPatterns(ModuleOp module, unsigned numThreads) {
-  ConversionTarget target(*module.getContext());
-  target.addIllegalOp<scf::ReduceOp, scf::ReduceReturnOp, scf::ParallelOp>();
-  target.addLegalDialect<omp::OpenMPDialect, LLVM::LLVMDialect,
-                         memref::MemRefDialect>();
-
   RewritePatternSet patterns(module.getContext());
   patterns.add<ParallelOpLowering>(module.getContext(), numThreads);
   FrozenRewritePatternSet frozen(std::move(patterns));
-  return applyPartialConversion(module, target, frozen);
+  walkAndApplyPatterns(module, frozen);
+  auto status = module.walk([](Operation *op) {
+    if (isa<scf::ReduceOp, scf::ReduceReturnOp, scf::ParallelOp>(op))
+      return WalkResult::interrupt();
+    return WalkResult::advance();
+  });
+  return failure(status.wasInterrupted());
 }
 
 /// A pass converting SCF operations to OpenMP operations.