ElementwiseOpFusion: option for disable empty (#430)

* ElementwiseOpFusion: option for disable empty

---------

Co-authored-by: Matthias Gehre <[email protected]>

Author: josel-amd

mlir/include/mlir/Dialect/Linalg/Passes.td

@@ -75,6 +75,11 @@ def LinalgElementwiseOpFusionPass : Pass<"linalg-fuse-elementwise-ops"> {
   let dependentDialects = [
     "affine::AffineDialect", "linalg::LinalgDialect", "memref::MemRefDialect"
   ];
+  let options = [
+    Option<"removeOutsDependency", "remove-outs-dependency", "bool",
+           /*default=*/"true",
+           "Replace out by tensor.empty">,
+  ];
 }
 
 def LinalgNamedOpConversionPass: Pass<"linalg-named-op-conversion"> {

mlir/include/mlir/Dialect/Linalg/Transforms/Transforms.h

@@ -1701,7 +1701,8 @@ using ControlFusionFn = std::function<bool(OpOperand *fusedOperand)>;
 /// when both operations are fusable elementwise operations.
 void populateElementwiseOpsFusionPatterns(
     RewritePatternSet &patterns,
-    const ControlFusionFn &controlElementwiseOpFusion);
+    const ControlFusionFn &controlElementwiseOpFusion,
+    bool replaceOutsDependency = true);
 
 /// Function type which is used to control propagation of tensor.pack/unpack
 /// ops.

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

@@ -2134,11 +2134,13 @@ void mlir::linalg::populateFoldReshapeOpsByCollapsingPatterns(
 
 void mlir::linalg::populateElementwiseOpsFusionPatterns(
     RewritePatternSet &patterns,
-    const ControlFusionFn &controlElementwiseOpsFusion) {
+    const ControlFusionFn &controlElementwiseOpsFusion,
+    bool removeOutsDependency) {
   auto *context = patterns.getContext();
   patterns.add<FuseElementwiseOps>(context, controlElementwiseOpsFusion);
-  patterns.add<FoldFillWithGenericOp, FoldScalarOrSplatConstant,
-               RemoveOutsDependency>(context);
+  patterns.add<FoldFillWithGenericOp, FoldScalarOrSplatConstant>(context);
+  if (removeOutsDependency)
+    patterns.add<RemoveOutsDependency>(context);
   // Add the patterns that clean up dead operands and results.
   populateEraseUnusedOperandsAndResultsPatterns(patterns);
 }
@@ -2180,7 +2182,8 @@ struct LinalgElementwiseOpFusionPass
     };
 
     // Add elementwise op fusion patterns.
-    populateElementwiseOpsFusionPatterns(patterns, defaultControlFn);
+    populateElementwiseOpsFusionPatterns(patterns, defaultControlFn,
+                                         removeOutsDependency);
     populateFoldReshapeOpsByExpansionPatterns(patterns, defaultControlFn);
     tensor::populateBubbleUpExpandShapePatterns(patterns);
 

mlir/test/Dialect/Linalg/fusion-elementwise-ops-no-remove-outs-deps.mlir

@@ -0,0 +1,13 @@
+// RUN: mlir-opt %s -p 'builtin.module(func.func(linalg-fuse-elementwise-ops{remove-outs-dependency=0}))' -split-input-file | FileCheck %s
+
+#identity = affine_map<(d0) -> (d0)>
+
+func.func @keep_outs_dependency(%arg: tensor<4xf32>) -> tensor<4xf32> {
+  // CHECK-NOT: tensor.empty
+  %1 = linalg.generic {indexing_maps = [#identity, #identity], iterator_types = ["parallel"] } ins(%arg: tensor<4xf32>) outs(%arg: tensor<4xf32>) {
+    ^bb0(%in: f32, %out: f32):
+      %exp = arith.negf %in: f32
+      linalg.yield %exp : f32
+  } -> tensor<4xf32>
+  return %1 : tensor<4xf32>
+}