[mlir][linalg] Let tile and fuse fail for tile sizes zero.

Adapt `tileConsumerAndFuseProducers` to return failure if the generated tile loop nest is empty since all tile sizes are zero. Additionally, fix `LinalgTileAndFuseTensorOpsPattern` to return success if the pattern applied successfully.

Reviewed By: mravishankar

Differential Revision: https://reviews.llvm.org/D118878

mlir/include/mlir/Dialect/Linalg/Utils/Utils.h

@@ -269,10 +269,10 @@ public:
   /// Returns the loop ops generated from tiling.
   ArrayRef<scf::ForOp> getLoopOps() { return tileLoopOps; }
 
-private:
   /// Returns true if the tile loop nest has no tile loops.
   bool isEmpty();
 
+private:
   /// Returns true if the tile loop nest invariants are satisfied:
   /// - The `rootOp` has been tiled at least once.
   /// - The number of tile loop operations and dimensions match.

mlir/lib/Dialect/Linalg/Transforms/FusionOnTensors.cpp

@@ -458,5 +458,9 @@ mlir::linalg::tileConsumerAndFuseProducers(OpBuilder &b, LinalgOp consumerOp,
     return failure();
   fuseProducersGreedily(tileLoopNest.getRootOp().getInputOperands());
 
+  // Exit if the tile loop nest is empty since all tile sizes are zero.
+  if (tileLoopNest.isEmpty())
+    return failure();
+
   return tileLoopNest;
 }

mlir/lib/Dialect/Linalg/Transforms/Transforms.cpp

@@ -592,10 +592,6 @@ LogicalResult mlir::linalg::LinalgTileAndFuseTensorOpsPattern::matchAndRewrite(
   SmallVector<int64_t> rootTileSizes(options.tileSizes.begin(),
                                      options.tileSizes.begin() +
                                          rootOp.getNumLoops());
-  if (llvm::all_of(rootTileSizes, [](int64_t ts) { return ts == 0; })) {
-    return rewriter.notifyMatchFailure(
-        op, "all tile sizes are zero, nothing to do");
-  }
   SmallVector<int64_t> rootInterchange =
       options.tileInterchange.empty()
           ? llvm::to_vector<6>(llvm::seq<int64_t>(0, rootOp.getNumLoops()))
@@ -603,6 +599,11 @@ LogicalResult mlir::linalg::LinalgTileAndFuseTensorOpsPattern::matchAndRewrite(
                                  options.tileInterchange.begin() +
                                      rootOp.getNumLoops());
 
+  // Check `rootTileSizes` contains non-zero tile sizes.
+  if (llvm::count(rootTileSizes, 0) == static_cast<long>(rootTileSizes.size()))
+    return rewriter.notifyMatchFailure(
+        op, "expect at least one non-zero tile size");
+
   // Check `rootInterchange` is a permutation of the `rootOp` loop dimensions.
   // It has to be a permutation since the tiling cannot tile the same loop
   // dimension multiple times.
@@ -623,7 +624,7 @@ LogicalResult mlir::linalg::LinalgTileAndFuseTensorOpsPattern::matchAndRewrite(
   // Apply the filter if specified.
   for (LinalgOp linalgOp : tileLoopNest->getAllTiledAndFusedOps())
     filter.replaceLinalgTransformationFilter(rewriter, linalgOp);
-  return failure();
+  return success();
 }
 
 /// Linalg generic interchange pattern.

mlir/test/Dialect/Linalg/tile-and-fuse-no-fuse.mlir

@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s -test-linalg-codegen-strategy="anchor-op=linalg.generic fuse tile-sizes=0,0 run-enable-pass=false" -cse -split-input-file | FileCheck %s
+// RUN: mlir-opt %s -test-linalg-codegen-strategy="anchor-op=linalg.matmul fuse tile-sizes=0,0,0 run-enable-pass=false" -split-input-file | FileCheck %s
 
 builtin.func @no_fuse_gemm(%arg0 : tensor<?x?xf32>, %arg1 : tensor<?x?xf32>) -> tensor<?x?xf32> {
   %c0 = arith.constant 0 : index