Add an optional argument for pattern rewriter max iteration count (NFC)

Some rewriters take more iterations to converge, add a parameter to overwrite
the built-in maximum iteration count.

Fix PR48073.

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D91553

mlir/include/mlir/Transforms/GreedyPatternRewriteDriver.h

@@ -24,20 +24,38 @@ namespace mlir {
 
 /// Rewrite the regions of the specified operation, which must be isolated from
 /// above, by repeatedly applying the highest benefit patterns in a greedy
-/// work-list driven manner. Return success if no more patterns can be matched
-/// in the result operation regions.
-/// Note: This does not apply patterns to the top-level operation itself. Note:
+/// work-list driven manner.
+/// This variant may stop after a predefined number of iterations, see the
+/// alternative below to provide a specific number of iterations before stopping
+/// in absence of convergence.
+/// Return success if the iterative process converged and no more patterns can
+/// be matched in the result operation regions.
+/// Note: This does not apply patterns to the top-level operation itself.
 ///       These methods also perform folding and simple dead-code elimination
 ///       before attempting to match any of the provided patterns.
-///
 LogicalResult
 applyPatternsAndFoldGreedily(Operation *op,
                              const FrozenRewritePatternList &patterns);
+
+/// Rewrite the regions of the specified operation, with a user-provided limit
+/// on iterations to attempt before reaching convergence.
+LogicalResult
+applyPatternsAndFoldGreedily(Operation *op,
+                             const FrozenRewritePatternList &patterns,
+                             unsigned maxIterations);
+
 /// Rewrite the given regions, which must be isolated from above.
 LogicalResult
 applyPatternsAndFoldGreedily(MutableArrayRef<Region> regions,
                              const FrozenRewritePatternList &patterns);
 
+/// Rewrite the given regions, with a user-provided limit on iterations to
+/// attempt before reaching convergence.
+LogicalResult
+applyPatternsAndFoldGreedily(MutableArrayRef<Region> regions,
+                             const FrozenRewritePatternList &patterns,
+                             unsigned maxIterations);
+
 /// Applies the specified patterns on `op` alone while also trying to fold it,
 /// by selecting the highest benefits patterns in a greedy manner. Returns
 /// success if no more patterns can be matched. `erased` is set to true if `op`

mlir/lib/Transforms/Utils/GreedyPatternRewriteDriver.cpp

@@ -220,12 +220,26 @@ bool GreedyPatternRewriteDriver::simplify(MutableArrayRef<Region> regions,
 LogicalResult
 mlir::applyPatternsAndFoldGreedily(Operation *op,
                                    const FrozenRewritePatternList &patterns) {
-  return applyPatternsAndFoldGreedily(op->getRegions(), patterns);
+  return applyPatternsAndFoldGreedily(op, patterns, maxPatternMatchIterations);
+}
+LogicalResult
+mlir::applyPatternsAndFoldGreedily(Operation *op,
+                                   const FrozenRewritePatternList &patterns,
+                                   unsigned maxIterations) {
+  return applyPatternsAndFoldGreedily(op->getRegions(), patterns,
+                                      maxIterations);
 }
 /// Rewrite the given regions, which must be isolated from above.
 LogicalResult
 mlir::applyPatternsAndFoldGreedily(MutableArrayRef<Region> regions,
                                    const FrozenRewritePatternList &patterns) {
+  return applyPatternsAndFoldGreedily(regions, patterns,
+                                      maxPatternMatchIterations);
+}
+LogicalResult
+mlir::applyPatternsAndFoldGreedily(MutableArrayRef<Region> regions,
+                                   const FrozenRewritePatternList &patterns,
+                                   unsigned maxIterations) {
   if (regions.empty())
     return success();
 
@@ -241,10 +255,10 @@ mlir::applyPatternsAndFoldGreedily(MutableArrayRef<Region> regions,
 
   // Start the pattern driver.
   GreedyPatternRewriteDriver driver(regions[0].getContext(), patterns);
-  bool converged = driver.simplify(regions, maxPatternMatchIterations);
+  bool converged = driver.simplify(regions, maxIterations);
   LLVM_DEBUG(if (!converged) {
     llvm::dbgs() << "The pattern rewrite doesn't converge after scanning "
-                 << maxPatternMatchIterations << " times";
+                 << maxIterations << " times";
   });
   return success(converged);
 }